LUNAR AND NEAR-EARTH DEVELOPMENT An Interactive Qualifying Project Report

Document technical information

Format pdf
Size 911.0 kB
First found Jun 9, 2017

Document content analysis

Language
English
Type
not defined
Concepts
no text concepts found

Persons

Alan Turing
Alan Turing

wikipedia, lookup

Chris Bryant
Chris Bryant

wikipedia, lookup

George R. Brown
George R. Brown

wikipedia, lookup

Walter Hohmann
Walter Hohmann

wikipedia, lookup

Organizations

Places

Transcript

LUNAR AND NEAR-EARTH DEVELOPMENT
An Interactive Qualifying Project Report
submitted to the Faculty
of the
WORCESTER POLYTECHNIC INSTITUTE
in partial fulfillment of the requirements for the
Degree of Bachelor of Science
by
Kathleen L. Haas
Francesco P. Bivona
Christopher J. Bryant
Matthew J. Fabian
Matthew J. Silva Sa
Michael F. Scaduto
Date: February 28, 2008
Professor Mayer Humi, Major Advisor
1. space
2. moon
3. humanity
This report represents the work of one or more WPI undergraduate students
submitted to the faculty as evidence of completion of a degree requirement.
WPI routinely publishes these reports on its web site without editorial or peer review.
1
Abstract
Executive Summary
Introduction & Motivations
03
03
05
1
Reasons to Explore
1.1 The Exploring Spirit
1.2 Threats to the Planet: Near Earth Objects
1.3 Global Dimming
Space Technology and Humanity
2.1 Space Technology on the Consumer Level
2.2 Satellite Communication Systems
2.3 Satellite Power Systems
Radiation Protection
3.1 Overview
3.2 Electrostatic Shielding
3.3 Drawbacks
3.4 Alternate Methods
Robots and Artificial Intelligence
4.1 Early Automata
4.2 Artificial Intelligence
4.3 Evolution Software
4.4 Robots in Space
Transportation Technology
5.1 Overview
5.2 Project Constellation – Ares I
5.3 Project Constellation – Ares V
5.4 Project Constellation – Orion
5.5 Project Constellation – LSAM
5.6 Project Constellation – Execution
5.7 Propulsion Alternatives
5.8 Space Elevator – A Solution to Escape Velocity?
5.9 Low Energy Trajectories
5.9.1 Simulating Low Energy Trajectories
Moon Colonization
6.1 Introduction
6.2 Energy
6.3 Personnel
6.4 Resources
6.5 Location
6.6 Law
07
07
08
10
12
12
16
18
20
20
22
25
25
27
27
28
33
35
39
39
39
40
41
42
43
44
47
50
55
60
60
65
70
71
74
74
Conclusions
Recommendations for Future IQPs
Bibliography
78
79
81
2
3
4
5
6
2
Abstract
We investigated the social and technological aspects and requirements of colonizing the moon
and its impacts on humanity. To this end we considered various visionary technologies for the
establishment of a successful lunar base. In depth studies were performed regarding the
commercial motivations, laws and consumer applications involved in a lunar base. Such a base
will serve as a focal point for helium-3 mining, the detection and observation of near-Earth
objects and will serve as a spaceport to the planets.
Executive Summary
For ages mankind has been fascinated with the universe. A thirst for knowledge has driven
humanity to reach farther out to the world we inhabit, exploring each corner, and to what lay
beyond this planet. The reasons to venture out into the universe are as vast as the space to be
explored. Many justify this push for learning with the idea of the exploring spirit. As seen
throughout history mankind pushes the limits to comprehend the happenings of their
surroundings. From conquering the skies to exploring the depths, the exploring spirit has lead
mankind to new understandings and new applications to further their quest. Although this spirit
does not die too easily, it does raise enough mass involvement need to push mankind to its limits.
Threats to survival are evident in that entire species have been wiped out in one cataclysmic
event. Branching out humanity, to other parts of space, increases the probability that the human
race will endure an asteroid collision, or a sudden ice age. Global dimming has been masking
global warming for years. If not kept in check, the pollution from many of mankind’s industrial
processes will lead to a total climatic change that will test the survival of humanity.
3
These motivations lead to great technological advances that trickle back down to the consumer
level. In order to traverse the vastness of space efficient use of energy is needed by space
explorers. This advancement in energy can then be applied to the consumer level and in turn
further benefit humanity. New technologies, such as satellite communications and telemetry are
developed for use in space, can be applied here on Earth in many areas, such as reprogrammable
pacemakers. Ideas can be tested for practical consumer purposes such as a satellite system
developed for supplying power. The synergistic effect between the consumer level and the space
program leads to mutual development.
A huge limitation to prolonged space exploration is the detrimental effect of radiation. Radiation
protection is a key aspect to the future of space missions. New materials as well as novel
applications protect the space explorers from the deadly radiation. Radiation shields that utilize
the charge of the incoming particles are one method of protecting astronauts. By using a
combination of materials such as the Kevlar in astronaut suits as well as the recently developed
RXF1, protection technology can be developed that is both function and affordable. When these
advances are just not enough missions must rely on the help of robotics.
Artificial intelligence and robots play a large role in the future of space exploration. With the
obvious benefits of keeping human life out of harm’s way completely, robots will serve as a
simple helping hand for astronauts. NASA will be able to use artificial intelligence to send a
rover to explore the surface of the moon or any other planet. Software that allows a machine to
learn and reason like its human counterpart will propel space exploration. Missions far out of
contact from planet Earth will be carried out with a guarantee of success due to the human-like
intelligence of its explorers.
4
These missions that lie beyond this solar system present the obvious challenge of transportation.
This challenge is present in the nearest of mission as well. With the development of new
transportation technology the feasibility of space missions increases. With NASA’s plans for
Project Constellation, current fuel methods are optimized while new methods are investigated.
With the application of these new methods, a more advanced understanding of the complex laws
of gravity that govern motion can increase the efficiency of space travel ten-fold. Low energy
orbits link planets to planets like space highways with virtually no fuel cost. These
transportation methods will simplify the direct route from the Earth to the moon.
The colonization of the moon is a fundamental step to exploring other planets. There are many
challenges presented by the establishment of a lunar outpost. Once the laws are in place to
govern the process of moon colonization, the crew and location must be considered. With the
presence of a medical expert a must, it is clear that a broad spectrum of fields must be covered by
the crew as well as focused expertise. Along with the rigorous criteria for personnel, a plan must
be established to supply the crew with resources at the poles of the moon, the most likely point
of colonization. Supplying this outpost with water and energy will be a daunting task, which
must be accomplished efficiently for future space missions to be successful.
Introduction & Motivations
Francesco Bivona became involved in this project due to his interest in space travel and
exploration that he has had since childhood. He is an electrical and computer engineering major,
and as such was particularly interested in the technical aspects of a lunar base, such as
electrostatic shielding.
5
Matthew Fabian has been interested in space travel and how it has advanced us both literally and
symbolically as a species. His interests in computer science and interactive media have provided
a great vantage point for looking at the development of computer technology required for
advanced space travel.
Chris Bryant has been interested in space since his early childhood fantasy of wanting to become
an astronaut. While his career goals have changed since then to the field of mechanical
engineering, his interest in space intrigued him to participate in this project. His mechanical
engineering amplitude proved to be a fundamental necessity for the examination of space
technology.
Michael Scaduto has always been fascinated by the idea of space travel and colonization from an
early age. Interest in space is what led Michael to attend Worcester Polytechnic Institute as an
Aerospace Engineering major. Although his major has since changed to Civil Engineering,
Michael is still intrigued with the possibilities facing humanity and space over the next half
century and felt that this IQP was right for him.
The origins of the universe, as well as the laws that govern it, has always intrigued Matthew
Silva Sa. His passion for learning the fundamentals of physics through mathematics led him to
become involved in this project. Only by venturing beyond the world we live in can the true
nature of the universe be explained. The colonization of the moon is a vital step in acquiring
more knowledge of space.
Kathleen's interest in space exploration started at an early age, when she began spending hours
stargazing and playing with the telescope of her father, an amateur astronomer. She was always
6
fascinated by the idea of humanity traveling into space and exploring the unknown. She is
mainly interested in aspects of lunar colonization related to powering a potential base.
1 Reasons to Explore
1.1 The Exploring Spirit
There are many psychological and practical motivations for exploring space. Few will deny that
deep within mankind lies the urge to discover what lies beyond what is already known. Referred
to by many as “the exploring spirit,” it is the reason man has climbed to the tallest point on
Earth, conquered the poles and circled the globe in a balloon. It led the conquistadores to
explore other areas of the world and it has led to humanity’s inevitable firm grasp that it has on
our planet. It is driven by the curiosity instilled in us from our ancestors, and our deep desire to
inform ourselves of our surroundings so that we may better prepare for future endeavors. Pride
also plays an important role—many European voyages to explore new lands were motivated by a
sense of pride and patriotism to be the first to go somewhere or do something.
Much more recently in our history, our spirit, pride and curiosity have led mankind into an age of
space exploration. With so much of our planet discovered and documented, space exploration is
logically the next step of our curiosity’s focus. Satellites have been launched, probes sent out
enormous distances and man has landed on the moon. What we do from here depends on the
support that space exploration receives from the public in the decades to come. Many see space
colonization as inevitable—it is seen with the same sense of Manifest Destiny of previous
thinkers. There may be a day when humans exist but our planet will be uninhabitable from
environmental shifts or catastrophic asteroid impacts. Having an extra planet we can call home
is reassuring for the survival of our race.
7
The vacuum of space is a harsh environment. Extreme temperatures and levels of radiation
along with the more obvious lack of air and water make space exploration several-fold more
complicated than Earth exploration. It is much more costly and difficult to maintain human life
outside the confines of our atmosphere.
History has taught us that once the envelope has been pushed, public interest dies quickly. After
man had touched the moon’s surface, public interest of the Apollo program steadily declined.
Even if man were to walk on Mars, then what? Would the public have the patience to support
space exploration with no immediate benefit? Would the explorative spirit in us all be enough to
sustain us, or would our curiosity die out? The occasional millionaire may want an expensive
low gravity vacation, but other reasons would certainly be needed in order for the public to
justify paying for the research and development needed for such expensive endeavors.
Long term space colonization rests on several questions. Can we harvest and make use of
foreign materials or will all living supplies have to come from Earth? Do we have the political
and social interest to fund such expensive ventures? Will potential sources of income emerge as
we explore space, allowing commerce within space to go beyond the satellite communications
industry?
While a complete cost-benefit analysis should always be considered, there are many more
practical and pressing reasons to develop space technology. The universe is not standing idly by.
There are many threats to our planet that will require us to be prepared with tried and tested
space technology.
8
1.2 Threats to the Planet: Near Earth Objects
With asteroids, environmental issues, gamma-ray bursts and ourselves, it is clear that our stay on
planet Earth is a temporary one. Whether the human race can live past such a catastrophe
depends on our technology and how effectively we can find and migrate to a “backup” planet.
There are threats posed against our small planet on a regular basis in the form of near-Earth
objects (NEOs). These are not the only threat to humanity by any means, but they are one of the
most potent. One of these asteroids caused the extinction of the dinosaurs, when it collided with
the Yucatan Peninsula 65 million years ago. Such a monstrosity would have exerted a force of
200 billion kilotons on impact, judging by the Yucatan crater.1
Asteroid impacts are not always of this caliber, however. Smaller impacts are not so infrequent.
One of the more recent of such impacts occurred on October 1, 1990, when an asteroid only a
few meters in diameter collided with the central Pacific Ocean, yielding only 10 kilotons.
Another larger impact brought a force of 100 kilotons to Russia, near Vladivostok in 1947. The
smaller of the two was roughly equivalent to the atomic bomb that was used against Nagasaki at
the end of the Second World War.2
To use nuclear weapons to alter an NEO’s trajectory, we would have to know about it far in
advance. While nuclear explosives deliver tremendous force, the mass of the asteroid often
negates the impact: a 10 megaton hydrogen bomb would apply about 109 N of force, but
distributed over a mass so large that the generated velocity change is measured in mere
thousandths of a meter per second. For such a small velocity to cause the asteroid to avoid a
target 12,800 km in diameter, it must be given well over 100 years of time to do so.3
9
Little has been done specifically in this field; the most prominent accomplishment in progress is
the Orion program, which plans to bring humans back to the moon. There have also been
numerous endeavors to track near-Earth objects, or NEOs. This has been done with increasing
vigor over the past decade, with two bills proposed in the United States in 2004: The Pete
Conrad Act, which rewards amateur astronomers for sighting NEOs, and the George R. Brown
Near-Earth Object Survey Act, which allocates $20 billion to NASA for NEO surveying.4 All of
this is not particularly effective defense, but it is at least a path on which further improvements
can be made. It would be beneficial to perform more detailed, possibly close-range studies on the
composition of the asteroids that approach us, but it would be necessary to have actual humans at
locations beyond Earth, to speed up the process of interception and to allow for multiple attempts
in case the first one does not succeed. Without this, we would be dealing with probabilities with
which we would not want to wager the fate of humanity, if not the fate of all life on Earth.
1.3 Global Dimming
Global dimming is the effect of the gradual reduction of the amount of sunlight reaching the
Earth’s surface. This effect has not been accepted by the global scientific community until very
recently.5 It was observed by taking systematic measurements of the amount of sunlight
reaching the Earth’s surface since the 1950s. Global dimming has even been suggested to have
hidden the effects of global warming.
This phenomenon has mainly three causes. The sun is not getting darker but clouds, air pollution,
and aerosols are getting in the way reflecting a portion of the light from the sun back into space.
The main cause seems to be aerosols and air pollution being put into the atmosphere by human
action.6 These micron or smaller sized particles are made of sulfates, black and organic carbon,
10
dust, and even sea salt. These aerosols and other particles absorb solar energy and reflect
sunlight back into space. The particles also serve as nuclei for cloud droplets. This is a problem
because more pollution results in clouds forming with larger amounts of smaller drops. These
small drops reflect more sunlight and make the clouds act like giant mirrors. The small drops
also remain in the sky about half a day longer before falling to Earth which dramatically
increasing this effect.
Global dimming directly contradicts global warming and as a result the findings of less sunlight
reaching the Earth’s surface were ignored by much of the scientific community who were
embracing global warming. If less sunlight was reaching the Earth then this would cause cooling.
This was opposite of the heating effect that was being observed. As it turns out a reduction in
global dimming could in fact cause even more global warming. The first publication showing
evidence of global dimming was at the Swiss Federal Institute of Technology in 1985.7 Atsumu
Ohmura a geography researcher found that solar radiation hitting the Earth’s surface had
decreased by more than ten percent during the previous three decades. He published his findings
"Secular variation of global radiation in Europe" in 1989. In 1990 Viivi Russak published
“trends of solar radiation, cloudiness and atmospheric transparency during recent decades in
Estonia" and in 1994 Beate Liepert published "Solar radiation in Germany - Observed trends and
an assessment of their causes". These publications were painting a picture that global dimming
was something to be taken seriously.
Global dimming has even helped explain one of the greatest mysteries of climatology. If the
Earth was getting warmer then the rate of evaporation would be expected to increase but the
opposite effect has been observed. In the past fifty years or so there have extensive studies of pan
evaporation. This is an experiment using a pan filled with water that is used to determine the
11
quantity of evaporation at a given location. Pan evaporation has shown that evaporation is
decreasing which means that less sunlight is reaching them. Global dimming has provided an
explanation for this result.
The amount of dimming reported varies from region to region but the global average seems to be
around 2-3 percent per decade. This data is only terrestrial and does not include the area over
oceans. However since the early 1990s the trend has been slowly reversing or brightening. The
Baseline Surface Radiation Network, which was started in the early 1990s to collect surface
measurements, has shown a reduction of four percent in the past decade. This shift occurred at
the same time global aerosol levels were beginning to decline. This evidence strongly supports
that aerosol pollutants are a main cause of global dimming. It also supports why global warming
has had such a strong effect in the recent decade.
Another cause of global dimming is the contrails left by aircraft. This effect only became
prevalent after the September 11, 2001 attacks on the World Trade Center. During the three days
after the attack nearly all civil air traffic was grounded, providing a rare opportunity to research
the effects of these manmade clouds. Dr. David Travis had been researching for 15 years
whether contrails were having a significant effect on the Earth’s climate.8 During this rare
opportunity he observed an increase of over one degree Celsius in diurnal temperature variation.
This is a huge change in climate for just a few short days and shows that the population might be
doing more damage to the climate than previously thought.
12
2 Space Technology and Humanity
2.1 Space Technology on the Consumer Level
The motivations to develop technologies for space-travel are also found in every day life. Space
travel is complicated and often requires technology that does not yet exist, but that needs to be
created. There are often spin-offs of these technologies that are used commercially and for the
benefit of all of humanity, not just astronauts.
A major concern for astronauts is access to clean water. NASA engineers developed water
purification systems to recycle water for consumption on the International Space Station.
Astronauts and lab rats aboard the station excrete urine which is purified and exhale water vapor
and which is condensed and then purified. The purification process begins with a filter that
removes debris and other impurities, then continues with a catalytic oxidation reactor that kills
bacteria and viruses. The technology for water purification has applications here on Earth,
especially in third-world countries with limited access to clean water.
There were three major advances to technology related to pacemakers brought about by NASA.
The need for rechargeable long-life batteries on spacecraft led to similar batteries in pacemakers.
Space microminiaturization technology led to a single-chip pacemaker that dramatically reduced
the size of pulse generators implanted inside a human’s chest. Finally, technology for two-way
communication with satellites led the way for two-way communication between doctors and
pacemakers, allowing the doctors to reprogram the device without requiring surgery, using
bidirectional telemetry.
Formulaid, which is an algae-based oil used in baby formula, was developed as part of a NASA
program called Closed Environment Life Support System (CELSS), in which microalgae was
13
studied as a supply of food and oxygen and as a catalyst in waste disposal that could be used
during space travel. It contains docosahexaeonoic acid (DHA) and arachidonic acid (ARA), two
essential polyunsaturated fatty acids which are found in the grey matter of the brain and in the
retina, believed to be closely related to development of mental and visual abilities. Both acids are
found in human milk but were not found in most infant formulas. With this new development,
however, babies and infants have more necessary nutrients in their formula that they would be
receiving if they were breast-feeding.
Catalysts for low-temperature oxidation of carbon monoxide were originally designed by
NASA’s Langley Research Center for use in a satellite project. In order to enhance the life of
carbon dioxide lasers, these were to recapture and recycle carbon dioxide. These lasers, which
produce beams of infrared light, have high power levels and are used for cutting, welding, and
even surgical procedures. All the oxidation catalysts need in order to function is a flow of gas
through them, with no extra energy input required. These catalysts are now used extensively here
on Earth, even though the satellite project never launched. A main use is in racecars, in which
drivers often used to become sick from carbon monoxide fumes in exhaust because the drivers
drive so close to each other for such long periods of time. The catalysts developed by NASA are
now used to create filters to prevent carbon monoxide poisoning.
Technology developed by NASA is even used in commercial and industrial products for
protection of the environment. Originally, work at the Jet Propulsion Laboratory (JPL) was done
to study microencapsulation of live cells. Living cells and biological materials were encased in a
sphere tough, semi-permeable material with diameters less than a millimeter. The JPL was
investigating the possibility of injecting microcapsules of thyroid hormone cells through a
hypodermic needle into humans to treat hormonal disorders. Today, we use the design as the
14
delivery mechanism for beeswax microcapsules which act as a food source for microbes that
consume oil. The most obvious application of this is in the cleaning of oil spills before the oil
settles to the bottom, causing liver, reproductive, and growth problems with bottom-dwelling
animals. In addition, boat-owners use BioSok Maintenance Systems, a commercial product
which clean contaminated bilge water before it is dumped overboard.
As the name suggests, "space blankets" originated from NASA technology. A space blanket,
made by dusting aluminum vapor over a light film, lacks the traditional softness often associated
with a blanket. It makes up for this, however, in its extremely light weight and ability to reflect
80% of a person’s body heat back to them. These qualities make them popular with campers and
other outdoorsmen, who value portability and effectiveness over comfort. The material has been
incorporated into many outdoor products suitable for temperatures as low as -72 degrees
Fahrenheit. The blankets have also been used for humanitarian relief in places such as Pakistan
following their 2005 Earthquake.
The space blanket material has been invaluable to NASA, and was used on almost every mission
they have launched. Instead of using them to conserve heat, however, they are used to block the
sun, as they reflect infrared light, the most thermally intense wavelength found in space. When
Skylab was first launched, the material saved NASA millions when Skylab began to overheat
immediately after it was launched. By effectively tying space blankets to the outside to cover a
damaged heat shield, Skylab was saved.
The first commercial use of space blankets came from marathons, who needed a way to keep
runners warm when they finished the race. As they stopped running their body heat would drop
quickly, and due to crowded finish lines, they would become hypothermic before being able to
15
change into their street clothes. It is now expected for marathon organizers to dispense the
blankets, which when folded are very small, to runners crossing the finish line. 9
It is often said that necessity is the mother of invention. Space travel is worth humanity’s time in
that, like war, it brings with it the motivation to be innovative and ground-breaking. Space travel
is an investment that has the potential to pay off. For example, if humans spent the money now to
create a lunar colony, we would need to find a way to power the colony, and perhaps this
necessity would lead to a way to harvest the energy of He-3. This in turn would then lead to a
cleaner energy source. While space travel is expensive, humans have the potential to create much
more wealth than they put in.
2.2 Satellite Communication Systems
Research into space travel and exploration has already yielded results that benefit the general
public. One of the more significant ways in which this has occurred would be the advent of
satellite communication. Satellite communication was envisioned as early as the inception of the
space programs of the United States and the Soviet Union, as would be evidenced by Sputnik’s
primary purpose being the transmission of a simple radio signal. However, the true benefits of
this have only reached the majority of humanity within the past couple of decades. Cellular
phones, Global Positioning Systems, the Internet – all of these would be either impossible or
greatly hindered without the use of satellites. There are multiple techniques for satellite usage,
each with its benefits and drawbacks. There are also new developments in satellite technology
still in progress, such as the implementation of Ka-band radio transmissions from satellites.
16
Improvements such as these should continue to be pursued, as well as other aspects of space
exploration that could be run alongside it.
There are three typical orbital patterns followed by satellites today. These are Geostationary
Earth Orbit (GEO), Medium Earth Orbit (MEO) and Low Earth Orbit (LEO) satellites. As their
names suggest, the primary difference between these satellite arrangements is the altitude which
the satellites have with respect to the Earth’s surface. Their altitudes are roughly 36,000 km,
10,000 km, and 900 km, respectively. The name of GEOs does not imply its altitude so much as
the fact that they are at such an altitude that their orbits keep them at the same position above the
Earth’s surface at all times. Despite it seeming easier to have LEO satellites in place, the closer
these satellites are to Earth, the more satellites are necessary for complete coverage. Only three
or four are needed for a GEO system, while 24-66 would be needed for LEO systems, with MEO
somewhere in between. Another advantage of GEO is that the satellites are always in the same
place, and as such ground-based antennae can be kept pointed in the same direction for ideal
reception. This advantage is only really present with stationary antennae, however, and not
mobile devices (cellular phones, etc.). Due to the higher number of satellites required for a LEO
system, another problem presents itself. There would either need to be a large number of
mechanisms on the ground for receiving data, or a means of interaction between satellites, which
would be a complicated process.10
Despite the seemingly incredible advantage GEO systems have over the competition, there are
two reasons why LEO or MEO systems have become far more dominant – radiation and
propagation delay. GEO satellites extend a good deal beyond the reach of the Earth’s magnetic
field. This can cause a good deal of interference with transmissions that are also
electromagnetically based, as any satellite transmissions would be. This is detrimental in
17
particular when there is peculiar solar activity in progress. Also, the greater distances involved
cause greater propagation delays. LEOs have roughly a 10 millisecond delay, while MEOs have
roughly 80 ms and LEOs have between 250-270 ms. This is considering ideal conditions, which
are off between 80-180 ms in practice. The threshold for delay without causing issues such as
echoing with audio transmissions is 300 ms, so often GEO systems are impractical for this
purpose. Still possible for the transmission of data in text form or the like, but overall, MEOs and
LEOs perform better. Thus, most satellite arrangements in development or in use (i.e. Globalstar,
Iridium, or Odyssey) are exclusively MEO, LEO, or some combination involving one or both of
those.11
Despite the fact that numerous of these satellite systems are already in place, there is still room
for improvement. One of these is the implementation of Ka-band transmission frequencies.
Frequency is another important aspect of satellite data transmission, as with higher frequency
comes higher rate of data transfer, and less likelihood of congestion within the satellite network.
Ka-band frequencies are far higher than those used previous (C- and Ku- band), by over an order
of magnitude. C- and Ku- band frequencies are within the MHz or single-digit GHz frequencies,
While the Ka-band spectrum is also called the 30/20 GHz spectrum. Systems implementing this
broadband capability have been in development since roughly 2000, and continue to be expanded
upon.12
Thus, there is a good deal of improvement that can still be made upon the satellite
communication capabilities we have currently in place. With improvements in band frequencies,
a greater benefit to the general public can be obtained. As such, this serves as at least one of the
motivating factors for further investment of resources into space travel and exploration. New
breakthroughs are always a possibility, and as has already been seen, they have a tendency to
18
return to the masses in a noticeable way. Not all of the results of space travel will remain solely
in textbooks.
2.3 Satellite Power Systems
One concept for the use of satellites to benefit humanity is that of a Satellite Power System, in
which one or more satellites are kept in a geosynchronous orbit around the Earth, gathering solar
power with large, intricate panels, and an equal number of refracting antennae (“rectennas”)
collecting the energy on the surface, which would have been converted to microwaves by the
satellite(s) and transmitted downward. It is technically a possibility, but for numerous reasons, at
present it is both economically and ecologically infeasible.
Why is this? First and foremost, for the transmission of any significant amount of microwaves, a
large area of the Earth’s surface is needed to be cleared out for the array collecting energy on the
ground. The base formula for the ground area needed is as follows:
D = 2.44 d λ/Dtrans
Where d is the distance from the surface, lambda is the wavelength of the transmitted
microwaves, and Dtrans is the diameter of the transmitter. ‘d’ in this case would be 36,000 km (the
altitude required for geosynchronous orbit) and lambda would be about 12 cm for microwaves at
the desired frequencies. So, the needed surface diameter would be 10.5/Dtrans. Proposed plans for
a system such as this, to be at all effective at receiving and converting large enough amounts of
energy, would require a 1 km transmitting diameter, so over a 10 km diameter is required. Both
the difficulties in delivering a 1 km transmitter and the even larger solar panels required, and the
necessity for large cleared areas, make this not a cost effective prospect. A possibility, yes, but
clearing out a large region of uninhabited forest or desert, along with the maintenance costs in
19
either location, would prevent such a power source from being a suitable competitor or
replacement for current sources of energy.13
There are ways of minimizing this. For instance, the solar panels could be made immobile. They
would not be effective for as long a period of time, but it greatly simplifies the design. Not only
could there be fewer moving parts in the satellite design, but also the transmitter could be placed
directly on the panel itself, as oppose to being in some central, immobile portion of the satellite.
Wiring is expensive, so this also makes the prospect far cheaper. Even with this, however, at
current technological standards, it is still not entirely cost effective. The matter of large
transmitter and receiver sizes is still an issue, and one that has yet to be resolved.14
Another issue to take into consideration is the effect on the environment. The effect of a constant
exposure to 2450 MHz microwave radiation at varying degrees of power per area, on both
humans and the environment at large, must be taken into consideration and studied. It may prove
to make the process outright infeasible, and if not it may be far more costly to both make it
possible and make it safe. Furthermore, a low-humidity and precipitation region may be
desirable, as the effect of the system’s radiation on mobile cloud cover, let alone the clouds’
effect on the system, remain largely unknowns. The likely solution to radiation spread out along
the surroundings would be to simply clear out the surroundings and make them inaccessible to
the general population, but this would still be costly.15
Overall, these combined factors make the process of a satellite power system infeasible. Perhaps
with research into other forms of energy transmission (lasers, for instance), along with some of
the cost-cutting measures mentioned here, it could be accomplished. It does not seem entirely
20
unworthy of further study, but at the moment it is slightly beyond the reach of modern
technology.
3 Radiation Protection
3.1 Overview
There are many dangers astronauts face both on the moon and in space. To effectively protect
astronauts on the moon or elsewhere in space, effective means of protection need to be
developed. The Earth’s atmosphere and magnetic field protect us from radiation and
micrometeoroids but in space there is nothing to protect astronauts from their deadly effects.
Violent explosions on the sun’s surface accelerate protons near the speed of light, creating
electromagnetic radiation throughout the entire electromagnetic spectrum, known as Solar
Particle Events (SPE). Galactic cosmic radiation (GCR), large bursts of high-energy particles
that are believed to come from supernovae, also contribute to the bombardment of radiation
present in space. Astronauts on long term missions need be concerned with the amount of
exposure to radiation they receive.
SPE can have an energy of 100 MeV to 300 MeV and GCR can have an energy of 1,000 MeV to
10,000 MeV.16 These high energy particles can easily penetrate conventional space craft, as well
as the astronauts in them, subjecting them to large doses of radiation. These particles can damage
DNA therefore increasing the risk of cancer, cataracts, neurological disorders and non-cancer
mortality risks. Large doses of this space radiation can even cause immediate death. 17 If humans
are to live in space for extended periods of time then there must be protection from these deadly
phenomena.
21
One possible way to protect astronauts from space radiation and micrometeoroids would be to
simply bury a moon base under the surface. This would create a barrier that would help absorb
the harmful particles of cosmic rays and solar flares as well as micrometeoroids. The problem
with only this solution is astronauts cannot continuously be underground. They need to be
protected on the surface as well. The technology already exists to protect astronauts from
micrometeoroids in space. A Thermal Micrometeoroid Garment makes up the outer layers of
today’s space suits and effectively protects astronauts from micrometeoroids. The Thermal
Micrometeoroid Garment does this by using seven layers of aluminized Mylar laminated with
Dacron and an outer layer of white Ortho-Fabric made with a combination of Gore-Tex, Kevlar,
and Nomex.18 Protection against space radiation is another challenge yet to be developed.
The Apollo missions had no real radiation protection because of the added mass of the required
lead. They relied on the scarcity of solar flares and galactic cosmic rays, as well as the overall
brevity of the missions. Traveling through the Van Allen belt at their speeds may have only
resulted in less than 1 rem of radiation—hardly enough to make anyone even feel ill. However,
over the amount of time needed for an excursion to Mars or a permanent colonization of the
moon, some form of radiation protection is needed. The dense material option may be too costly
due to the cost of the materials themselves, let alone the amount of energy it would take to move
a spacecraft or the required materials for a surface structure. The increased mass would put a
large strain on the craft’s propulsion system.
One possibility that could offer protection against space radiation on the surface of the moon is
some type of electrostatic radiation shield that could deflect the charged particles. R. H. Levy
was the first to propose such shielding in the early 1960’s, but his ideas were never pursued
much past the mid-1970’s because of the lack long-term space missions requiring such
22
technology. The simplest device would, like Earth, be a magnetic dipole. Because a particle
inside a magnetic field has a curved path, as it approaches the shield it would curve away from it,
protecting the craft and people within.
3.2 Electrostatic Shielding
This principle is based on deflecting charged particles by means of Lorentz force:
F = qE + qv × B . Where q is the charge of a radiation particle, v is the particle velocity, E is the
electric field of the shield and B is the magnetic component of the field.19 This could be achieved
by mounting electrically charged spheres on top of 40 meter poles above a populated moon base.
One design involves several spheres oriented on three axes, six with a 20-meter radius, charged
to -300MV, 160 meters away from the protected region, and six with a 10-meter radius, charged
to 300MV, 50 meters away from the protected region (see Fig. 1). 20
Figure 1
23
It is estimated that each spherical structure and supports would weigh 20-40 tons, depending on
the materials used. This is capable of deflecting or greatly reducing the impact energy of most
bombarding particles.21 Another design is called the multi-shield approach (Fig. 2). This concept
employs multiple levels of electrostatic shields made from spherical generators high in the air
combined with flat electrostatic screens constructed low to the ground.
Figure 2
Recent technological advances make the prospect of magnetic shielding not terribly far from
reality. First, high strength-to-weight materials are available. The strength of the magnetic field
is limited by the tensile strength of the material used. New materials, like Lead(II) oxide (PbO)
or Kevlar provide more strength for their weight than steel. Higher-temperature superconductors
are now available. These superconductors use separated copper-oxide planes and are able to
operate at more than 77K—a temperature range that would allow for the direct radiation of
excess heat off into space.
24
Due to the development of particle colliders, technology in large superconducting magnets has
improved recently. Computers are now able to solve direct numerical integration, allowing them
to solve particle trajectory problems necessary for running the magnetic shield. Previously,
software would need to approximate their integral solutions to be quick enough to be useful.
Magnetic radiation shielding may be a viable option in the near future, like in Moon colonization
or manned missions to Mars.
3.3 Drawbacks
Despite all of this, the idea is far from perfect, however. The main crippling design challenge for
this type of device is power. The power required to run one of these devices is huge and there is
currently no available technology to produce it. The power that would be required to protect
against solar particles would be at least 100 MV and the power required to protect against cosmic
ray particles would be at least 1000 MV.22 Another problem is that EM fields have potentially
been linked to human health risks, such as a certain varieties of cancer.23 This would have to be
avoided, as well as the impact on electronic equipment that EM fields would have. Elevating the
spheres well above any sort of settlement would reduce the negative impacts, while still
providing protection from radiation originating in space.
In a comprehensive space colonization effort, the protection of astronauts in a space craft is also
a pressing issue. One possibility, like on the moon, would be a multi-pole electrostatic radiation
shield. This would use three electrically charged spheres aligned along the axis of the ship. Two
negatively charged spheres would be at either end with a positively charged sphere at the center
near the crew module.24 This combination should be enough to deflect high energy protons and
electrons that would otherwise penetrate the space craft. This still does not alleviate the immense
25
problem of getting enough power to run this device. That problem would need to be solved in
order for this idea to be feasible.
3.4 Alternate Methods
An alternative would be to place the ships cryogenic fluids around the crew module. Liquid
hydrogen is typically used for fuel and is also very good at absorbing space radiation. The atoms
of liquid hydrogen do not fragment into secondary particles like heavier elements do when hit
with high energy radiation. The secondary particles can be as deadly as the space radiation
itself.25
The materials with which spacecrafts’ hulls are constructed could also be changed to be more
radiation-resistant. NASA scientists have invented a new polyethylene-based material that is
stronger and lighter than aluminum, called RXF1. The real benefit of this material is not its
strength to weight ratio but rather the fact that it has superior space radiation shielding properties.
Compared to aluminum, RXF1 is 50 percent better at shielding solar flares and 15 percent better
at shielding cosmic rays.
The benefit of plastic-like materials rather than heavier materials like aluminum is that they
produce a lot less secondary radiation. When the shielding material is bombarded with space
radiation particles, small nuclear reactions are produced with the atoms of the shielding material.
Those reactions create harmful nuclear byproducts that enter the spacecraft. RXF1 makes a good
shielding material because it is made of lightweight carbon and hydrogen atoms that produce
minimal secondary radiation particles when bombarded with space radiation while at the same
time fragmenting the incoming radiation particles.
26
RXF1 is amazingly strong and light. Currently the specifications of how it is made are secret
because it is patent pending. What is known so far is that RXF1 has three times the tensile
strength of aluminum and is 2.6 times lighter. Therefore, it could also potentially serve as a
ballistic shield that could deflect micrometeorites. RXF1 is also a fabric so it could be used to
drape around molds and even shaped into specific spacecraft components.26 Overall this is an
exciting new material that has potentially many applications in the aerospace industry.
Perhaps power concerns with electrostatic shielding could be worked around with nuclear power,
at least for the lower power requirement SPEs have, but that would require even more research.
Ultimately it may be necessary to initially construct underground complexes regardless, but that
in itself takes time during which taking such precautions against radiation would be useful. Even
after subterraneous construction, should it occur, radiation is still a pressing issue for long term
space transit as well. If and when electrostatic shielding becomes feasible on the moon, it will
also be of value to humanity while reaching out to Mars and beyond.
4 Robots & Artificial Intelligence
4. 1 Early Automata
As far as history goes back, man has toyed with the idea of creating entities other than
themselves that were intelligent. In early Greek history, myths of Hephaestus and Pygmalion
talk of intelligent robots. In the 1400’s the first clocks were made using lathes and in 1652 the
first digital calculating machine was made.
In 1950, Alan Turing proposed that a Turing Machine, a hypothetical computer that uses an
infinitely long piece of magnetic tape, defined what is computable through machine intelligence.
In other words, if something can be calculated or determined, then a Turing Machine could be
27
constructed to determine it. Things that have this calculating power are called Turing powerful
and pass a Turing Test. It can be argued that a human brain is only Turing powerful, as it is
simply a “machine” that takes in input, your current collective memory and sensory input, and
provides an output, new electrical impulses in your brain and muscle contractions or relaxations.
Far in the future, man may be able to simulate a brain. Today, we already have amazingly
complex artificially intelligent (AI) programs. These programs, accompanied with capable
robots, are and will continue to be essential to voyages into space.
In 1958, MIT computer scientist John McCarthy invented Lisp, derived from “List Processing
Language”. Lisp paved the way for several areas of computer programming, especially AI, to
thrive. Lisp, now developed into an entire family of computer programming languages, was
originally designed for mathematical notation. However, it quickly became the language of
choice for creating artificially intelligent systems. Kent Pitman of HyperMedia Inc. jokingly
said, “Please don't assume Lisp is only useful for Animation and Graphics, AI, Bioinformatics,
B2B and E-Commerce, Data Mining… Intelligent Agents, Knowledge Management, Mechanical
Computer Aided Design, Modeling and Simulation… just because these are the only things they
happened to list.”
Mostly everything in Lisp is stored in “linked lists,” a list made of several nodes each pointing to
the next element of the list. Lisp’s source code itself is made of linked lists, allowing
programmers to effectively rearrange pieces of code during program execution using smaller,
domain-specific programming languages imbedded within Lisp. This makes it attractive to AI
programmers. It is nearly the oldest programming language still in use today, second only to
IBM’s Mathematical Formula Translating System (Fortran).
28
4.2 Artificial Intelligence
Today, we may not be able to simulate true intelligence, but developments in the field of
artificial intelligence (AI) have been integral to the development of self-sufficient automata.
However, even modern-day complex computer-run systems, like those that run autopilots for
aircraft, only need to be able to account for so much. They are usually massive, deterministic
sets of algorithms and used merely as tools by humans to aid in the decision making process.
Early programs were limited greatly by the relatively slow hardware available at the time. AI
was heavily influenced by various academic areas like biology, neural networks, game theory,
statistics, logic and philosophy.27
As the places humanity aims for become more remote and less inhabitable, the need for robots
that can account for a large range of problems becomes more apparent. The decision making
capabilities of humans are usually taken for granted until one tries to emulate it algorithmically.
However, NASA is continually improving the artificial intelligence of their rovers and their
navigation systems in the interest of making them more self reliant and better at humanistic
decision making capabilities. These traits will be integral to the construction of remote bases on
the moon and mars in the future, as well as assisting human teams in exploration and
experimentation.28
At NASA Ames Research Center in California, computer programmers are developing complex
AI software for rovers. In the past, simple artificial intelligence (AI) systems allowed rovers to
make simple navigation and path finding decisions. NASA aims to have a much smarter system
to replace the decision making of mission controllers for expeditions millions of miles away,
where the speed of light becomes a major issue with communication and direct remote control
29
becomes impossible. “The Exploration Vision calls for closer cooperation between humans and
robots than ever before. Creating robust robotic assistants, as well as making key spacecraft
systems self sufficient, requires building systems that can adapt their behavior to environments
that are complex, rapidly changing, and incompletely understood.”
The Ames Research center’s Intelligent Systems Division has several artificially intelligent
programs open and available to the public “to increase NASA software quality via community
peer review, accelerate software development via community contributions, maximize the
awareness and impact of NASA research, and increase dissemination of NASA software in
support of NASA's education mission.” This software includes a genetic evolutionary program
written in Java, a virtual vision framework called Vision Workbench, and an AI system for life
support.
In late 2005, the Collaborative Decision Systems milestone demonstration showcased rovers
built on the Intelligent Deployable Execution Agents (IDEA) architecture, a Linux based goaloriented system for autonomous agents designed to take and respond to commands. “In the
demonstration… during a simulated extravehicular activity (EVA), an astronaut verbally
commanded both rovers to assist in different ways in getting a microscopic image of a new rock.
The operation was overseen by habitat-based crew members … assisted by a personal agent
running on the astronaut's backpack computer which automatically filed data products and kept
the astronaut on schedule.” 29
Here, the goal is to develop robots that will assist human astronauts in extra-vehicular activities
and to lighten the overall load of physical labor required of them. While a completely
autonomous robot is ideal, a more realistic alternative is to allow different degrees of use
30
specification. An astronaut can give a very high level command, and very specific command, or
directly control the rover, depending on the rover’s ability to deal with the situation on its own.
This can be a time saver, as more detailed commands can be given only if the robot cannot first
figure out things for itself.
Artificially intelligent systems are also needed for much broader decision making. It is
necessary to automate the work of the astronauts and information regarding mission control.
Because of the signal delays involved in a mission to Mars, for example, the hope is to create a
computerized substitute for mission control on Earth.
“The system is designed for tasks that can be decomposed into loosely coupled subtasks that
each person and robot can execute. By using a distributed multi-agent architecture, people,
robots, tools, instruments, and interfaces can be integrated into a coherent data and workflow
system.”8 Through a system of subtask division, the robot is able to convert a spoken command
into a series of subtasks. Those subtasks are broken down further until they can be split into
machine level commands, like moving a specific piece of the robot.
Despite these efforts, we are still far away from having completely autonomous systems, capable
of exploring the outer depths of the universe completely independent of human intervention.
Once this is available, human space exploration will be able to reach a new tier in how far it can
go and what it can accomplish.
Dennis Gorelik, a Montana software developer who specializes in AI, outlines what he calls a
True Artificial Intelligence System (AIS). AIS tried to completely simulate and implement the
functionality and thinking capacity of the human brain. An AI system should be able to learn
like a child without any help from programmers and should be able to think abstractly enough to
31
learn in any field of study.
An AIS has eight essential components. First is main memory which would hold a table of
established concepts and a table of established cause-effect relationships that the AIS has
learned. Second is a motivation system. The motivation system drives the AIS similar to an
animal being driven by its instincts. It includes a hierarchy of goals based on their importance
and relevance. Third is an integration of the main memory and the motivation system. Here,
you have “super” goals and “sub” goals. “Super goals recognize specific events and generate a
reward based on these events. Sub goals are modified by a reward value.” Goals that are hardcoded into the system should constantly evaluate and make conclusions based on where it is
relative to its ultimate goals. Fourth is a decision making system that is tightly knit with the
motivation system. The last four can be described as constantly learning, reading outside input
from the world, forgetting useless information, and being able to alter its own program on the go.
Fundamentally, many of the principles of Gorelik’s supposed AIS come from the way humans
think. For example, Gorelik believes that sight (digital image processing) is not necessarily
required for intelligence, as blind people are still intelligent. In deciding whether or not an AIS
should be able to explain how it logically came to any given decision, Gorelik proposed that very
few humans are able to do this, so it does not make sense as a requirement for AI. Deciding
whether or not to use a statistical algorithm depends on whether or not humans would. For
example, if a person sees “4 + 5 = ?”, most people do not calculate the sum of four and five, but
rather instantly remember that four and five make nine. On the other hand, larger numbers
would need to be calculated normally.
Another important feature of AI systems is being able to identify and communicate with other
intelligent entities, namely humans. “After all, we get a lot of what we learn based on the
32
feedback of other intelligent entities.” Computers must be able to learn, from others and from
themselves, the rules of which the universe runs by. “Many AI developers try to put the
‘practical rules’ into code directly. This is just wrong. The consequences of putting practical
rules in the code are severe: development takes a huge amount of time… My estimation is that
[these programs learn] at least 10 times slower than average human… That means that
programming a ‘practical rule set’ of 20-year-old will take at least 200 man-years. Huge
development time is not the major problem though. The real problem is that such system still is
not able to learn.”
4.3 Evolutionary Software
Evolutionary software works by creating a system where different components of a device or
algorithm can be created, tested and mixed with other components based on their performance.
This system creates a Darwinian method of coming up with device/software designs or
configurations where the computer mixes and matches aspects of top-performing components to
come up with a naturally selected solution.
The Intelligent Systems Division’s artificial evolutionary software program is quite powerful.
One project, lead by Kalmanje Krishnakumar, sought to optimize the design of antennae using
evolutionary software.30 Instead of a manual design, which is labor intensive, the program uses
evolutionary algorithms to generate an optimal shape and size for the antennae. It started with
random antenna designs refined those using thousands of evolutionary iterations. “We told the
computer program what performance the antenna should have, and the computer simulated
evolution, keeping the best antenna designs that approached what we asked for. Eventually, it
zeroed in on something that met the desired specifications for the mission," Ames Center
33
researcher Jason Lohn said. The results were unlike anything any engineer would think up. 31
This 2.5 cm2 antenna can is designed for satellite communication with Earth. The evolutionary
software it was written runs on 120 separate computers.32
Two antennae designs generated from NASA’s evolutionary AI software.
Evolutionary software was used by a lab in Sussex, England to create a chip that could
distinguish between two distinct tones.33 Dr. Adrian Thompson, a researcher for the Department
of Informatics, used a Field-Programmable Gate Array (FPGA)—a chip whose logic is not hardwired and can be rewritten. FPGAs are slower and produce more heat, but are obviously much
more flexible.
Using only 100 logic gates, the first generations seemed almost random. By generation 220, the
chip could reproduce the tone it was given. By generation 1400 it could distinguish between
tones half of the time, and by generation 4000 it was completely functional. Thompson took it
further by later making it respond to verbal “stop” and “go” commands. The chip only used 37
logic gates and 5 completely separated areas of circuitry. Despite being seemingly independent,
disabling one section caused the chip to stop working. Not even Dr. Adrian Thompson knew
how it worked.34
34
Using evolutionary software to create complex AI architectures has its share of advantages and
disadvantages. While AI programming can create very complex programs using very little
resources, its future is limited. Systems that ensure the safety of others, like medical equipment
or military navigation systems, must be thoroughly tested and declared safe and bug-free. With
AI programming, it is entirely possible for vestigial or dormant traits to appear in programs,
making them unpredictable or unreliable. Relying on AI software to run our lives would be
dangerous, and many would be thinking that The Matrix has predicted the future.
4.4 Robots in Space
In 2000, a company called Applied Space Resources (ASR), in coordination with physicist Mark
W. Tilden, created a couple different designs for robots they would like to send to the moon in
their own endeavors. These very small, insect-like devices could sift through the surface and pick
up loose dust. This dust would interfere with larger devices if left unaltered. These would have to
be cheap, and built in large numbers. The idea envisioned by Tilden is something along the lines
of an ecosystem, but involving robotic equipment. Tilden’s ideas do greatly resemble an
ecosystem. The robots he envisions have a base set of tasks they do consistently, as opposed to
being directly instructed.35 This makes autonomy a key element. Without it, constant
communication would be necessary for every device on the surface, and this would be
complicated and expensive.
Sending simple machines for simple tasks, and then sending more advanced robotics for
construction of infrastructure is sensible. Unfortunately, it does not seem that these commercial
endeavors have been carried out or developed to a great extent. They were initially slated for
2004, but this has not been the case. Given that there was little information available on the
35
technical aspects of this plan of Tilden’s, it may this was nothing more than a pipedream before
it was shot down, possibly due to the fact that it was not government-backed. However, the
principle in the broadest sense is sound. Preparations for colonization should involve preliminary
robotic work automated via artificial intelligence. This can be followed by remotely controlled
robotics and human settlement.
The moon is a very hostile place for humans. Once humans have started colonizing, robots
would be invaluable in sharing the workload and lessoning the amount of harmful exposure
astronauts would be exposed to on a day to day basis. Unlike humans, robots are not as ill fitted
for surviving in the harsh environment of space.
Currently the Robot Systems Technology Branch at NASA's Johnson Space Center in a
collaborative effort with DARPA is designing a humanoid robot called Robonaut. Robonaut is
being designed for Extravehicular Activity (EVA), or spacewalks. Its goal is to have greater
dexterity, work envelope, ranges of motion, strength and endurance then that of a suited
astronaut. Robonaut’s design concept is an anthropomorphic robot that is the size of an astronaut
in a space suit. It has two arms, two five fingered hands, a head and a torso. Its dexterous arms
enable dual-arm operations and its hands can directly interact with a wide range of interfaces
without special tooling. Robonaut’s hands each have fourteen degrees of freedom. Its forearm
houses the motors and drive electronics with a two degree of freedom wrist, and its hand is fully
functional with respect to a human hand.36
Robonaut’s arms are designed with human equivalent strength, human scale reach, thermal
endurance for an eight hour EVA, fine manipulation and a motion range that is better than a
36
human. Each arm contains thermal vacuum rated motors, harmonic drives and fail safe brakes.
Each joint contains sixteen sensors of strain gages, encoders, and absolute position sensors.
Robonaut
Robonaut’s head is mounted on an jointed neck. The head houses two color camera eyes that are
capable of producing stereo vision with a third smaller camera for peripheral vision. The vision
system is capable of tracking moving humans and objects. The head is protected by a helmet
made of an epoxy resin that is made using a stereo lithography machine at the Johnson Space
Center.
Robonaut’s control system combines cooperator commands, force data, and safety rules that
provides real time control. It can be controlled directly by what is called telepresence, by shared
37
control or by full autonomy. Telepresence uses a human operator to control the actions of
Robonaut remotely. Since Robonaut has 47 degrees of freedom and is anthropomorphic the best
way to control it is a kind of master-slave control mechanism that can duplicate the same
motions of the robot. The control system includes a Helmet Mounted Display that shows what
Robonaut sees, force and tactile feedback gloves and posture trackers. It resembles a virtual
reality type system that effectively immerses the operator in Robonaut’s workspace. The Helmet
Mounted Display can display stereo or bi-ocular view, field-of-view and it has graphical overlay
capabilities. It also has speech recognition capabilities.
The hands are controlled by glove based finger pose sensors and bend sensitive materials that
track the motion of each of the teleoperator's fingers. Then that information is used to move
Robonaut’s fingers in the same way. This way complex manipulation tasks are performed easily
by just moving one’s own hands. The motion of the head, arms and torso are performed in much
the same way as the hands except the teleoperator’s movements are acquired by magnetic based
position and orientation sensors. In this way Robonaut can be controlled precisely and safely
from a remote location.
Robonaut is designed so the torso can be mounted in a variety of different ways depending on its
application. It could be mounted on a rover for mobility on the moon, a Space Shuttle arm for
space walks or even some kind of biped legs.
Robotics and advanced AI development are two industries that will have a mutually beneficial
relationship with space travel. Devices like Robonaut and artificially intelligent rovers will be
essential in doing the heavy lifting in man’s space endeavors.
38
5 Transportation Technology
5.1 Overview
Transportation technology is the foundation of any space endeavor. In this section current as
well as future transportation technologies, programs and trajectories will be discussed. The
future development of safe and efficient transportation technology will be imperative for future
colonization of the moon and beyond.
Viable, safe and economical transportation to the moon is an extreme technological challenge.
NASA has already begun the process of designing components to achieve this goal. Instead of
designing a whole new space vehicle to go to the moon, NASA announced in September 2005
that they are going to rely on a lot of existing technology to enable more efficient construction.
The basic technology needed for this task has already been used successfully during the first
Apollo missions to the moon. Now this technology needs to be improved not only to go to the
moon, but to stay there for extended periods of time.
NASA has started Project Constellation to create the latest generation of spacecraft for human
spaceflight. Project Constellation consists of the Ares I and Ares V launch vehicles, the Orion
crew capsule, the Earth Departure Stage and the Lunar Surface Access Module. All these
spacecraft are necessary for a mission to the moon.
5.2 Project Constellation – Ares I
The Ares I launch vehicle, also known as the Crew Launch Vehicle, will be a two stage rocket.
The first stage will be a single Solid Rocket Booster. Its design will be adapted from the current
39
Space Shuttle Solid Rocket Booster to produce more thrust, burn longer and therefore be able to
reach a higher orbit. The main design change to be made to the first stage is an additional
segment. The Solid Rocket Booster on the Space Shuttle today has four segments. The
improved design will have five segments. The upper stage of the Ares I will be powered by a J2X rocket engine. The J-2X is fueled by liquid hydrogen and liquid oxygen and its design was
derived from the J-2 rocket engine that was used on the Saturn IB and Saturn V rockets. Ares I
is capable of carrying a payload of up to 25,000 mT to low Earth orbit.37
Courtesy of NASA
5.2 Project Constellation – Ares V
The Ares V launch vehicle, also known as the Cargo Launch Vehicle, will also be a two stage
rocket. The first stage will use both liquid and solid fuel engines simultaneously producing
about 8.9 million pounds of thrust with a burn time of about 150 seconds. It will use two Solid
40
Rocket Boosters like the single Solid Rocket Booster on Ares I in conjunction with five RS-68
liquid fueled rockets. The Rocketdyne RS-68 Rocket System is the largest existing liquid
hydrogen and liquid oxygen fueled engine and it is capable of producing 663,000 pounds of
thrust. The upper stage will use a J2-X rocket engine like the second stage of the Ares I. Ares V
will be capable of carrying up to 65,000 mT of payload to lunar orbit or 130,000 mT of payload
to low Earth orbit.38
Courtesy of NASA
5.4 Project Constellation – Orion
The Orion Crew Capsule will be able to carry a crew of four to six astronauts. It consists of four
main parts: the Crew Module, Launch Abort System, Service Module, and Spacecraft Adapter.
The Crew Module will be used for, as the name implies, carrying the crew. It will be able to
automatically dock to the International Space Station. It will use parachutes to slow its decent to
Earth after reentering the atmosphere and will land as well as be recovered at sea. The Crew
41
Module will also be able to be reused up to 10 times. The Service Module will hold the
propulsion system and expendable onboard supplies. It will be propelled mainly by an Aerojet
AJ-10 rocket engine that will be fueled by nitrogen tetroxide and monomethyl hydrazine. It will
also contain a Reaction Control System that will consist of maneuvering thrusters that will use
the same propellants. The Launch Abort System will be able to separate the Crew Module from
the launch vehicle in the event of an emergency. It will be able to do this on the launch pad or
during the ascent. It will use a solid rocket powered launch abort motor that will use reverse
flow to separate the Crew Module from the launch vehicle. The Spacecraft Adapter is what links
the Service Module to the launch vehicle.39
5.5 Project Constellation – LSAM
The Lunar Surface Access Module (LSAM) will be used as the transport vehicle to and from the
moon. It will have two parts, an assent stage and a descent stages. The assent stage will house
the crew and the decent stage will contain the crew’s consumable resources and scientific
equipment. The LSAM will not be reusable. The Earth Departure Stage is propelled by a J2-X
42
rocket engine. It will be used as the main propulsion system to deliver the Lunar Surface Access
Module and Orion to the moon.40
5.6 Project Constellation – Execution
The whole system of Project Constellation will work as follows. First Ares V will be used to
launch the heavy cargo load of the Earth Departure Stage and the Lunar Surface Access Module
to low Earth orbit. Then two to four weeks later Ares I will be used to launch Orion to low Earth
orbit. The advantage of having two separate launch vehicles is it enables more specialized
designs for the different purposes the rockets need to fulfill. The next step will require Orion to
dock with the Lunar Surface Access Module and the Earth Departure Stage. Then the Earth
Departure Stage will be fired and propel the three parts to 25,000 mph towards the moon. The
Earth Departure Stage will then be jettisoned. Three days later Orion and the Lunar Surface
Access Module will arrive at the moon. The LSAM will use its rocket engine as a brake to enter
into orbit around the moon. The crew will then leave Orion, enter the LSAM, undock and the
LSAM’s decent stage will be used to deliver the crew to the moon. Orion will remain in orbit for
up to six months.
When the crew are ready to return to Earth the LSAM’s assent stage will be used to rejoin Orion
in its lunar orbit. It will leave the decent stage behind. The crew will then reenter Orion and
jettison the assent stage that will eventually crash on the dark side of the moon. Orion will then
fire its rocket engine propelling itself toward Earth. Three days later Orion will reach Earth and
jettison its Service Module that will burn up in Earth’s atmosphere. The Crew Module will then
reenter Earth’s atmosphere, after which its parachutes will deploy to slow its decent. The Crew
Module will finally land in the ocean where it will be recovered and used again. While NASA’s
43
Project Constellation is a great relatively short term solution it only requires the currently
available technology of chemical rockets. In the future other transportation technologies will
need to be explored.
5.7 Propulsion Alternatives
One of the most obvious technological barriers standing before mankind is our inability to move
through space at sufficient speeds. Even our modern space shuttles cannot break 30,000 km/hr.
One design study program, titled “Project Orion,” sought to design a vessel with a high thrust
and high specific impulse in the interest of enabling fast, cheap interplanetary travel. Started in
1958, Project Orion explored the possibility of using nuclear pulse propulsion, an idea originally
proposed by Stanislaw Ulam in 1947, to allow for theoretical speeds of up to six percent the
speed of light. The Nuclear Test Ban Treaty of 1963 brought Project Orion to an unfortunate
end.
The design of the Orion worked by releasing a nuclear device several hundred meters behind the
craft and then detonating it. The impulse from the plasma wave would be absorbed into large
pusher plates attached to a two stage shock absorber. An Orion ship could be as large as
materials allowed. One proposed model would place the ship at 400 m long and over 8 million
tons. The nuclear reaction mass used to create explosions would be disk shaped to create a long
and cylindrical plasma wave. This would allow the collimation factor, the fraction of the plasma
wave that hits the absorption plates, to be much higher than normal. A proposed “Super Orion,”
using thermonuclear propulsion would be able to travel to the edge of the outer planets and back
in under a year. A trip to Proxima Centauri would take only 44 years. The use of thermonuclear
explosions would increase the top speed to nearly .10c.
44
Realizing a nuclear propelled craft is not without its own problems. Launching an Orion or
detonating a nuclear bomb in a low orbit would create an EMP blast that would hurt nearby
electrical equipment. The craft’s creation and testing would violate the Nuclear Test Ban Treaty
and previous attempts to create exceptions in the interest of space travel have not been successful
due to international pressures. The pressure plates could erode away after continued subjection
to large forces and temperatures as high as 67,000° C. Engineering pressure plates capable of
withstanding such erosive forces would be hard to test, as creating an environment capable of
containing repeated nuclear explosions would be very difficult. However, calculations show that
a pusher plate could be designed that would only erode away 1 mm after continued use, and that
if protected by an oil, it would not erode at all.
Another potential problem is the levels of radiation astronauts would be exposed to at each
nuclear pulse, however the very protection that keeps harmful solar flares from hurting the crew
could be increased and would be able to account for such radioactivity. Detonating in low Earth
orbits would be acceptable so long as it is done well above our magnetosphere, so fallout would
not return to Earth. To avoid the complications of launching directly from Earth, any vessel or
space station of such a large magnitude would have to be built in space.
While there are many obstacles preventing nuclear propulsion from being a reality now, it is an
attainable landmark in our explorations into deeper space.
Another possible alternative to traditional chemical propulsion is electrical propulsion. As
opposed to simple driving force from reacting chemicals, a fuel can be ignited and controlled
with electricity. Not only is it possible, but it can be implemented with far greater fuel efficiency.
45
It is not without its drawbacks, of course, but it is available now, and has been in development
over the past forty years.
Indeed, research into electrical thrusters dates back as far as 1950s, and testing as in 1962.
Between then and the mid-1980s, 77 flight tests of electrical thrusters have taken place. These
can be divided into three categories: electrothermal, electrostatic (ion), and electromagnetic
(plasma).1 Ion seems the most popular of the three, and a great deal of resources have been
poured into it. By the 1980s, two varieties of ion propulsion had emerged. One of these involves
ionizing a fuel (generally Mercury or Xenon) with electrical current run through a coil at high
frequencies. Another bombards the fuel directly with electrons. Both of these approaches were
implemented, and both had wide ranges of effectiveness, with driving force varying from 10-250
mN.2 The key here is that the force is measured in milli-newtons, a very small amount.
How can this prove useful? The answer to this is that, at present, ion propulsion is not effective
as a means of primary thrust off the surface of the planet. It does serve its purposes once in orbit,
or in deeper space, however. Applications in orbit include maintenance and maneuvering. In any
environment beyond removal from the atmosphere, electrical propulsion at present can be used
for attitude control.3 The downside of electrical propulsion is that a great deal of electrical power
is needed even for this small thrust. Thus, unless an alternate power source is implemented
(something surpassing solar and chemically generated electricity), electrical propulsion will only
play this smaller, yet still crucial role. Furthermore, it does so far more efficiently than its
chemical counterparts when doing the same job. For the same amount of fuel, if it is ignited
electrically instead of chemically, the time a thruster can remain active is an order of magnitude
higher for an electrical thruster than it is for a chemical one.4 Furthermore, by its very nature,
electrical propulsion has a greater deal of control post-ignition than chemical propulsion.
46
Adjusting current or rate of bombardment can adjust the potency of an electrical thruster at any
time, while chemical propulsion relies on a prior balance of fuels to deliver the desired amount
of driving force.
Electrical propulsion is already in use and to be used to its fullest potential, new power sources
will be needed. As it is, generating thrust forces measured in mere mN on the mass of a small
satellite would require power along the lines of kW. Barring the restraint of greater electrical
power being required if it is to be used with a driving force beyond a few Newtons, it proves to
be more effective. At present the best that could be put to use would be nuclear power. This
means of power has yet to be implemented in space, so much work in that area would be
required. Time will tell how electrical propulsion can be utilized effectively to replace chemical
propulsion outright. And not much time is needed, at that.
5.8 Space Elevator – A Solution to Escape Velocity?
Another interesting space transportation concept is the ‘space elevator.’ The concept of a space
elevator has been one frequently considered among authors of science fiction, most notably
Arthur C. Clarke’s Fountains of Paradise. The concept has been around for decades – a cable of
some material extending above the Earth in a geosynchronous orbit (actually significantly
longer, as the center of mass is what would be needed to be kept geosynchronous), with a
satellite or facility at the other end for receiving supplies or passengers, is not a very foreign
concept to the collective minds of humanity. However, practicality had always been a hindrance,
largely due to lack of adequate materials to create such a structure. With the advent of carbon
nanotubes (the first material to meet the tensile strength requirements and in fact surpass them)
in recent years, the practicality of such a mechanism has increased by leaps and bounds, and is
47
actually a worthwhile consideration. Why would this be desirable? Launches of crafts from the
Earth’s surface to beyond the reaches of our atmosphere are some of the most costly, risky
aspects of all present space travel. An elevator system, after construction, and would have a
much lower cost of maintenance and operation once the construction is complete. It could even
perhaps lead to habitable public space above the surface of the Earth, or result in being a tourist
attraction on top of the scientific or economic gains received from a low-gravity environment.
Overall, it would be a worthwhile endeavor to pursue.
How it would be accomplished is actually not that complex a process in the grand scheme of
things. It would be perhaps comparable to the building of intricate bridges or skyscrapers in the
past. The first step would be the primary craft, which would remain on the far end of the eventual
cable, to be launched into a geosynchronous orbit. From there the spooled initial cable, only
capable of supporting perhaps just below two metric tons on its own, would be lowered, and the
craft would make its ascent to the required height (roughly 100,000 km). This results in the cable
being held at its required length. After that point, “climbers” would be built to ascend the cable
and either descend or be discarded, each trip upward augmenting the cable with more of the
carbon nanotube material, reinforcing it. Over the course of two years and repeated climber runs,
the cable would be sufficiently strong to allow for its more mainstream uses.1
One of the more pressing issues of design, next to what once was the primary issue of suitable
materials, is the matter of power. Most conventional means of power would either be insufficient
or excessively heavy at first, and new methods would need to be designed. One of the more
promising of these methods would be the use of lasers. Fortunately, this has already been in
development for some time as a possible means of powering satellites in orbit. A company called
Compower has been in development of a system which would utilize a 200 kW laser provided by
48
the University of California at Berkley, directed toward the desired target by an orientation of
mirrors similar to those used by current high-power telescopes. 200 kW was the initial research
level of power. Currently it has reached levels of 350 kW and could ultimately be expected to
supply 1.75 MW. For the application upon the climbers, roughly 2.4 MW would be required, so
either further alterations to the system or simply multiple lasers being emitted from different
locations would be necessary. Far more power would be needed for the final elevator transport
when the cable is complete, but by then either a heavier power supply could be supported or
more research would have to be put into the laser power concept. Still, for the construction of the
structure at the very least, this is sufficient.2
Even though the technology is roughly within our grasp, there are, as always, difficulties posed.
These result from both the Earth’s atmosphere and the rigors of the environment beyond it: wind,
lightning, meteors, corrosive atomic Oxygen, radiation, and lower orbiting objects would all pose
a threat. Each of these can somehow be avoided or the risks greatly reduced, however: Wind
conditions can be minimized by proper placement (low-wind regions), and making the cable as
thin as possible to minimize aerodynamic drag. There are some lightning free locations on the
Earth, or at least locations where lightning is very infrequent. These, or high on the peaks of
mountains, would potentially be suitable locations. One location that meets both low-wind and
low lightning-risk areas is the region west of Ecuador (either on an above-water platform or a
ship), and is proposed as a likely site by Bradley Edwards, in his book regarding the subject.
Meteors and Low Earth objects are perhaps the most potent risk. Meteors are less so as given the
size of the ribbon and density of meteor impacts one is only expected over the course of several
decades, and depending on angle it may not do significant damage whatsoever. However, to
avoid this risk, reinforcing the cable as soon as possible is advised. LEOs pose a much greater
49
risk, as they follow an orbital path which will bring them back to the cable each time they
complete an orbit. However, LEOs are more easily predicted than meteors, and could be avoided
by slightly moving the cable. Atomic oxygen can be remedied by a very thin coating of metal
(such as gold) already known to be resistant to its corrosive properties. Radiation protection
could be kept roughly at the state it currently is for space travel near the Earth.3
So it is clearly not without its risks. However, the concept of a space elevator is not so farfetched
as to be completely discarded. No endeavor is without its risks, and this need not be an
exception. However, the risks are able to be reduced, and the gains are worthwhile. Further
research and development should be made in this field. Feasibility is not too far off, and the
opportunity awaits us.
5.9 Low Energy Trajectories
Aside from new propulsion technologies, future space travel may also require the use of low
energy trajectories. With the first successful moon landing in 1969, the possibilities seemed
endless; however this was just a stepping stone. In order to reach Earth’s largest satellite it took
the best technology of the time and a lot of fuel. Even today, with new technological advances,
space flight is still constrained by fuel. Flight trajectories must be optimized in order to use as
little fuel as possible. Methods of optimization involve using the gravitational pull of the Sun, the
Earth, the other planets, and their moons in order to navigate the solar system. A direct flight
from planet to planet would require a vast amount of fuel, while utilizing gravitational orbits can
reduce that cost.
The earliest space missions utilized trajectories called Hohmann transfers, named after Walter
Hohmann, a principal contributor to early orbital dynamics. The basic method of this type of
50
transfer is piecing together several conic section orbits determined by which celestial body is
dominating the force experienced by the spacecraft. These transfers rely on several spacecraft
maneuvers that provide a thrust force to alter the spacecraft’s acceleration. Typically these
transfers are direct shots; the spacecraft is sent at a significant velocity to towards its target. It
must then decrease its velocity sufficiently enough to be placed into orbit around its target. This
drastic change in velocity consumes a large amount of fuel. The problem that arises when
planning a successful trajectory in terms of fuel budget is to minimize the change in velocity.41
Lagrange points are one solution to that problem. These are five points associated with a basic
three body gravitational problem, such as a satellite and the moon and the Earth or the Earth and
the sun. At these points particles remain relatively stationary with respect to the two body
reference frame. The Lagrange points mark where combined gravitational forces provide the
exact centripetal force in order for an object to rotate with the two larger bodies. The distance of
the first and second Lagrange point can be determined from
where M is the mass of
the Earth and m is the mass of the moon, by solving for r. The other three can be derived using
the more general set of equations,
and
where M1 and M2 are the masses of the moon and
the Earth, m is the mass of the object at the Lagrange point, and r, r1, and r2 are position vectors
that are a function of time. L4 and L5, discovered by Joseph-Louis Lagrange, are located sixty
degrees behind and in front of the smaller body, while L1, L2, and L3 lie in line with the two
bodies.
51
The first three points are unstable; after a short period of time the orbits spiral away from these
points. Not only do the particles spiral away but they also spiral towards these stationary points.
Particles can drift into these points and collect there for a period of time. The spiraling orbits that
lead towards and away from these points map about manifolds or ‘tubes’ that can be traversed
without changing energy.
These manifolds, discovered by Poincare, are based in a six dimensional frame. This involves the
three Euclidean dimensions as well as the particles velocity in each direction. A particle traveling
in one of these unstable periodic orbits will travel out along the surface of one of these tube-like
manifolds as long as it stays at the same energy. It just so happens, if you consider two three
body systems with overlapping bodies you can find intersecting manifolds that will connect, say
Mars’ L2 point with Earth’s L1 point. This would allow a spacecraft to travel between these two
points without using as much fuel as it would take to take a direct route. This method would
sacrifice time, instead of fuel. It is similar to taking the long scenic route instead of taking the
freeway.
As the demand for understanding of our universe grows, so does the complexity of our questions.
Advancement in mathematical methodology is needed to attempt to find answers for these
questions. The study of the motion of objects in space, dynamic astronomy, and the study and
development of space mission trajectories, astrodynamics, rely heavily on the mathematical
analysis of the challenging N-body problem. This problem can be simplified in order to yield
rough solutions; however in order to obtain a in depth understanding of celestial motion
advanced techniques and computations from other disciplines, which share the mathematical
basis, must be employed.
52
By studying the motion of celestial bodies and using the laws of gravitational attraction an
ephemeris is produced listing the positions and velocities of the N bodies with respect to time.
The accuracy and breadth of this solution is dependent upon the number of assumptions made in
order to analyze the problem. This accuracy is dependent upon the goal of the analysis or space
mission. One of the earliest methods in mission design was utilizing the well understood two
body solution and a patched conic solution. A three body problem can be approached by linking
two two-body solutions. An example of this would be a system involving a spacecraft, the moon,
and Earth. A trajectory could be designed by combining the solution of the Moon-spacecraft
problem and the Earth-spacecraft problem. The two body solutions are basic conic section
trajectories that do not account for other gravitational attractions outside of the limited system.
Design criterion, such as minimal fuel consumption and transit time, determine the accuracy of
the trajectory design. The goal is to minimize the total change in velocity due to spacecraft
maneuvers while maintaining a certain transit time. By increasing the complexity of the analysis
from a patched conic approximation to the patched three-body problem, low energy, low fuel,
transfers can be obtained. This veers away from the simplified trajectories of the Voyager and
Galileo missions, to the more complex trajectories of Japan’s Hiten and ESA’s SMART-1
spacecraft trajectories. Due to the high change in velocities of the simplified trajectories, the
spacecrafts are not as perturbed by the gravitational attraction of bodies not being considered in
the system. More complex trajectories are low energy, low relative velocities, which take better
advantage of the N-body dynamics, a method originally discovered by Belbruno.
By using Belbruno’s low energy trajectories, two link three-body solutions are used as an initial
guess for a more accurate four-body solution that can reduce the energy consumption by at least
half. Using an analysis of a spacecraft’s kinetic and potential energy with respect to the other
53
bodies in the system, region called Hill’s region can be determined. This region is where the
spacecrafts motion is restricted to, that is, where the difference between the ship’s energy and
effective potential is greater than or equal to zero. These regions are connected to the Lagrange
points of the system. The invariant manifolds produced by the periodic orbits around these points
create an opportunity to insert a spacecraft into orbit around a new body outside of the original
system.
In order to further analyze these tubes and trajectories, techniques for other fields are used.
Techniques from molecular systems as well as software designed for fluid systems have share
the same mathematical basis with celestial mechanics. This leads to successful missions, such as
NASA’s Genesis Discovery Mission. This four year mission, launched in 2001, sent a vessel to
orbit the Sun-Earth L1 point in order to collect debris from solar winds. The vessel was in the
halo orbit around this point for two years before returning to Earth with its solar wind payload.
This trajectory had a zero change in velocity; it relied entirely on the low energy manifolds to
guide it through its mission.
The possibilities of these equilibrium points are endless. As new techniques are developed and
new software is created to help understand the motion of the celestial bodies, new missions such
as manned planetary missions will be tangible. By relying on computers to do the heavy
computations, celestial motion can be relatively easy to predict. The probability of an asteroid
riding a low energy manifold from beyond Jupiter to Earth can be found. These new methods
and techniques, with their mathematical basis, can help understand the formation of not only our
solar system but entire galaxies.
54
Although this method is not direct it still has various applications. By studying these ‘tubes’
astronomers can trace the routes of nearby comets and asteroids and predict how close these will
come to Earth. This method would give ample warning of an impending collision. Another
application is human travel and shipping. Although some trajectories take decades, even
millennia, they could be used to ship supplies to far off colonies or even from the Earth-Moon L2
point to a colony on the moon. If some people do not mind taking a ten year tour of through the
solar system then this method can be used to travel to nearby planets.
Using these special trajectories make a lunar colony more feasible. An important issue with the
formation of a lunar colony is the limited amount of resources on the moon. Utilizing these tubelike highways in space offers a solution for obtaining some scarce resources such as water. A
comet is a very good source of useable H2O; several of these giant balls of ice come relatively
close to our moon-Earth system. By gently altering the trajectory of a comet with very little, it
can be forced to travel along these tubes and aimed at the moon. The collision would supply the
lunar base with a useable amount of ice. Using these energy cost efficient trajectories is viable
way to supply a lunar colony with resources. Advances in technology and further computational
analysis will give a better idea of how these trajectories behave, and more importantly where
they lead.
5.9.1 Simulating Low Energy Trajectories
All massive celestial bodies warp the empty space through gravity. This idea was first
introduced into mainstream by Albert Einstein in the early twentieth century. Due to curved
space the simplest trajectories are no longer straight lines; gravity must be taken into account
when planning a mission trajectory. Computer software aids the design of space missions by
55
using unique and novel algorithms to help find paths of least resistance through space, or low
energy trajectories.
Although computers are a tremendous advantage it is still immensely difficult to plan a mission
trajectory that takes into account all of the celestial bodies in the universe. Even limiting the
problem to just the planets and sun close to Earth is challenging. Therefore, assumptions must
be made to find approximate solutions.
MATLAB is a useful programming language that allows for easy modeling space trajectories
with certain assumptions. By considering the problem of launching a rocket to the moon,
MATLAB is used to find an optimal launch angle. In order for this program to have a
reasonable run time several assumptions must be made. The problem is simplified from an Nbody gravitational problem in three dimensions to a three body problem in two dimensions. The
rocket is launched from the Earth, experiencing the gravitational forces of the Earth, the moon,
as well as the Sun. By considering the sun as fixed, the trajectories simulated are heliocentric.
This allows for easy determination of the Earth’s orbit, which can be simplified to circular or
kept as elliptical.
The overall shape of the Earth’s and the moon’s orbit depends on the initial velocities. The
initial positions are chosen such that they all lie in line with each other with the Earth at its
maximum distance from the Sun and the moon the maximum distance from the Earth. The
trajectory that the rocket takes after launch is calculated by numerically solving the basic
gravitational integrals of motion. By using Euler’s method for solving the system of second
order differential equations an approximate trajectory is formulated that has relatively small error
than an actual trajectory due to the time step chosen. In order to find a launch angle that will
56
lead to lunar contact several iterations are performed with different angles chosen. After the
second iteration is completed a new angle is interpolated from the first to so that the rocket will
be closer to the moon after the allowed two days have progressed. After several more iterations,
the interpolations converge on a successful launch angle, which is then reported with the
trajectory model.
The use of MATLAB and other powerful math languages to model trajectories is essential for
space mission success. By analyzing the paths a rocket will take, new methods can be
discovered to study comets, and other near Earth objects. This will give a better understanding
of the infinite amount of low energy trajectories that connect all of the planets. By increasing the
complexity of the MATLAB code a more applicable model can be used to find these trajectories
from the Earth to the moon. This will lead to a drastic decrease in the cost of a flight to the
moon, increasing the feasibility and success rate of a lunar colony.
For the purpose of demonstration, the following code was written by Matthew Silva Sa:
% function RelD= SEMsim2(Theta,deltaTheta,N)
Theta=0;
deltaTheta=0.5;
N=10;
% SEMsim is used to find a successful rocket trajectory from the surface of
%
the Earth to the surface of the Moon within a time period of 3 days. The
%
rocket is launched with an initial magnitude of 11.34km/s relative to the Earth.
%
%
This function assumes:
%
(1) a heliocentric two-dimensional system, with the Sun's position
%
fixed at the origin.
%
(2) the Sun, Earth, and Moon are perfectly spherical with uniform
%
densities and are the only bodies in the system.
%
(3) the rocket only experiences gravitational forces.
%
(4) the Euler method of numeric integration is sufficiently
%
accurate to approximate the motion of the Earth, Moon, and rocket.
%
(5) the Earth's orbit around the Sun is elliptic with slight
%
perturbations due to the Moon's gravitational force.
%
(6) the Earth and the Moon are in an elliptical binary orbit with
%
slight perturbations due to the Sun's gravitational force.
%
%Input:
%
Theta: the launch angle of rocket in radians between 0 and pi/4.
%
0 radians point straight at the Moon a initial conditions.
%
deltaTheta: an angle in radians between 0 and pi/4.
%
N: Maximum number of iterations.
%
%Output:
57
%
RelD: Three element row vector of the distances between the
%
Center of the Earth to the rocket,
%
Center of the Moon to the rocket,
%
Center of the Earth to the center of the Moon.
%
Figure(1): Plot of the trajectories of the Earth's
%
center of mass in blue, Moon's center of mass in green, and rocket in red.
%
%Program runs until a successful trajectory is found or maximum number of
%
iterations is reached.
%
%Sun radius 695500km
%Earth radius 6371km
%Moon radius 1737km
format long %Prevents significant error in accuracy.
% Reads Earth and Moon Trajectory for 3 days.
Ex=dlmread('RexEllip.txt'); % x-coordinates for
Ey=dlmread('ReyEllip.txt'); % y-coordinates for
Mx=dlmread('RmxEllip.txt'); % x-coordinates for
My=dlmread('RmyEllip.txt'); % x-coordinates for
the
the
the
the
Earth.
Earth.
Moon.
Moon.
% Sets constants.
G=6.67428*10^-20; % Gravitational constant.
Rs=[0,0]; % Heliocentric model.
Ms=1.9891*10^30; % Mass of the Sun.
Me=5.9736*10^24; % Mass of the Earth.
Mm=7.3477*10^22; % Mass of the Moon.
totalT=172800; % Maximum time in seconds, do not exceed 3 days.
deltaT=30; % Time step in seconds, 30sec matches time step of the text files.
n=floor(totalT/deltaT); % Total number of steps.
% Initialize variables.
Ang=zeros(1,N); % Initializes vector for launch angles of each iteration.
DMR=zeros(1,N); % Initializes vector for distance between Moon and the rocket for each iteration.
I=0; % Initializes iteration count variable for While loop(1).
Dmr=1800; % Initialize distance between Moon and rocket with false constant to start while loop.
% While loop(1) continues as long as the distance between the center of the
%
moon and the rocket is greater than the radius of the Moon and as long
%
as the number of iterations is less than or equal to N.
while and(Dmr>1737,I<=N) % While loop(1)
I=I+1; % Counts each iteration of while loop(1).
% Set initial variables.
T=0; % Initial time.
Ang(I)=Theta; % Inputs Theta values into vector Ang for each iteration.
Rr=[149604371,0]; % Initial rocket coordinate, surface of the Earth.
% Initial distance between the center of the Moon and the rocket.
Dmr=sqrt(sum((Rr-[Mx(1),My(1)]).^2));
% Initial velocity of the rocket, includes orbital velocity of the Earth around the Sun
% Initial velocity of the rocket, includes orbital velocity of the Earth around the Sun
Vr=[0,sqrt(G*Ms/149598000)]+11.34*[cos(Theta),sin(Theta)];
and a launching velocity with fixed magnitude.
i=0; % Initializes iteration count variable for While loop(2).
% Initialize trajectory vectors.
Rex=zeros(1,n); % Initializes x-coordinates
Rey=zeros(1,n); % Initializes y-coordinates
Rmx=zeros(1,n); % Initializes x-coordinates
Rmy=zeros(1,n); % Initializes y-coordinates
Rrx=zeros(1,n); % Initializes x-coordinates
Rry=zeros(1,n); % Initializes y-coordinates
of
of
of
of
of
of
the
the
the
the
the
the
Earth's center.
Earth's center.
Moon's center.
Moon's center.
rocket.
rocket.
% While loop(2) builds the Earth's and the Moon's trajectories, while
%
calculating the trajectory of the rocket in steps of deltaT. Loop
%
continues while the time progressed, T, is less than totalT. Loop
%
breaks if the rocket is within 1737km of the moon, or the distance
%
from the Earth to the rocket exceeds that from the Earth to Moon.
58
while T<=totalT
i=i+1; % Counts each iteration of while loop(2).
% Build Trajectory vectors for plotting.
Rex(i)=Ex(i); % Inserts ith x-coordinate
Rey(i)=Ey(i); % Inserts ith y-coordinate
Rmx(i)=Mx(i); % Inserts ith x-coordinate
Rmy(i)=My(i); % Inserts ith y-coordinate
Rrx(i)=Rr(1); % Inserts ith x-coordinate
Rry(i)=Rr(2); % Inserts ith y-coordinate
for
for
for
for
for
for
the
the
the
the
the
the
Earth's center of mass.
Earth's center of mass.
Moon's center of mass.
Moon's center of mass.
rocket.
rocket.
% Calculate acceleration of the rocket.
As=-G*Ms*(Rr-Rs)/sqrt(sum((Rr-Rs).^2))^3; % Acceleration due to the Sun.
% Acceleration due to the Earth.
Ae=-G*Me*(Rr-[Ex(i),Ey(i)])/sqrt(sum((Rr-[Ex(i),Ey(i)]).^2))^3;
% Acceleration due to the Moon.
Am=-G*Mm*(Rr-[Mx(i),My(i)])/sqrt(sum((Rr-[Mx(i),My(i)]).^2))^3;
Ar=As+Ae+Am; % Sums all of the acceleration to find the total acceleration.
% Integrals of motion.
% Uses Euler method of numerical integration to find the rockets velocity.
Vr=Vr+deltaT*Ar;
Rr=Rr+deltaT*Vr;
% Uses Euler method of numerical integration to find the rockets position vector.
% Distances
% Distance between the rocket and the center of the Moon.
Dmr=sqrt(sum((Rr-[Mx(i),My(i)]).^2));
% Distance between the rocket and the center of the Earth.
Der=sqrt(sum((Rr-[Ex(i),Ey(i)]).^2)); % Distance between the center of the Earth and the
center of the Moon.
Dem=sqrt(sum(([Mx(i),My(i)]-[Ex(i),Ey(i)]).^2));
RelD=[Der,Dmr,Dem]; % Groups the distances for output.
% If statement(1) stops while loop(2) if the rocket is within 1737km from the center of the Moon.
if Dmr <= 1737
for k=0:n-(i+1)
Rrx(n-k)=[]; % Trims x-coordinate vector of the rocket.
Rry(n-k)=[]; % Trims y-coordinate vector of the rocket.
Rex(n-k)=[]; % Trims x-coordinate vector of the center of the Earth.
Rey(n-k)=[]; % Trims y-coordinate vector of the center of the Earth.
Rmx(n-k)=[]; % Trims x-coordinate vector of the center of the Moon.
Rmy(n-k)=[]; % Trims y-coordinate vector of the center of the Moon.
end
display('Success, you hit the Moon.'); % Outputs success message.
display(Theta); % Outputs successful launch angle.
break
end
% If statement(2) stops while loop(2) if rocket is farther from Earth than Moon.
if Der>Dem
for k=0:n-(i+1)
Rrx(n-k)=[]; % Trims x-coordinate vector of the rocket.
Rry(n-k)=[]; % Trims y-coordinate vector of the rocket.
Rex(n-k)=[]; % Trims x-coordinate vector of the center of the Earth.
Rey(n-k)=[]; % Trims y-coordinate vector of the center of the Earth.
Rmx(n-k)=[]; % Trims x-coordinate vector of the center of the Moon.
Rmy(n-k)=[]; % Trims y-coordinate vector of the center of the Moon.
end
display('Sorry, you missed the Moon.'); % Outputs failure message.
break
end
T=T+deltaT; % Adds time step to total time progressed.
end % Ends while loop(2)
DMR(I)=sign(-Rr(1)+Mx(i))*Dmr; % Builds vector of Moon to rocket distances. A negative sign
means the rocket is to the left of the Moon with respect to x-axis.
% If statement(3) determines the value of the launch angle, Theta, for
%
the next iteration.
if I==1
% If the first iteration does not yield a success the angle is increased or decreased
depending on the sign.
59
Theta=Theta-sign(-Rr(1)+Mx(i))*deltaTheta;
else
% After two iterations, a successful angle is approximated using a line interpolating the
data from the last two iterations.
Theta=(Ang(I)-Ang(I-1))/(DMR(I)-DMR(I-1))*(1737-DMR(I))+Ang(I);
end
end % Ends while loop(1)
% Plots the Earth's trajectory in blue, the Moon's trajectory in green, and the rocket's in red.
plot(Rex,Rey,'b',Rmx,Rmy,'g',Rrx,Rry,'r');
legend('Earth','Moon','Rocket');
Resulting low-energy trajectory of Matlab program from Earth to Moon
6 Moon Colonization
6.1 Introduction
Orchestrating a colonization program with regard to the moon is a multi-faceted process. There
are many economic burdens placed upon nations that seek to pursue it; the amount of equipment,
resources, and manpower required would be tremendous. Resources in particular would be a key
issue, one which could not be resolved with a single shipment of supplies. Materials and
equipment would be required in regular shipments, in addition to being acquired from the moon
itself when possible. This can be in the form of mining metals, or recovering lunar ice to
augment or replace shipments from Earth. Staff would have to be carefully selected, as
60
requesting additional personnel would be a serious undertaking once the selected population had
already arrived. Resources are also needed in another sense – a means of electrical power. This
can be satisfied by solar power, if the time is taken to establish a power infrastructure. Also, once
the basic needs of survival are met, a lunar colony would require a great deal of attention and
reform to be brought to our legal systems with regard to places beyond our planet.
Constructing a permanent base on the moon is not going to be an easy task for humanity, yet it is
a necessary step if mankind is to take its next step toward further exploring the solar system and
beyond. The processes and timelines for the establishment of a lunar base need to be thoroughly
researched and carefully constructed if mankind is to return to the moon in 2020 with the
intention of staying. For this project of humanity to get off the ground we must accept the
staggering costs that come with the development, construction and supplying of a permanent
lunar base. The establishment of a moon base involves 4 stages: unmanned exploration, manned
prospecting and surveying, base construction, and base operation, upgrading, and expansion.
Stage one in the establishment of a lunar outpost involves the use of unmanned reconnaissance
probes. The use of unmanned probes on the moon is nothing new and this stage of setting up the
outpost has been going on for a good number of years. The knowledge we have gained about the
moon over the past 50 years has been very extensive and it is safe to say that the data points to
either of the moon’s poles as being a suitable spot for a lunar outpost. This is a key point because
it will enable NASA or any other space agency to rely on solar energy to power the outpost,
instead of using nuclear power which would be highly controversial.
A good number of unmanned missions have surveyed and mapped the moon over the years but
in the next decade a number of new probes critical to the establishment of a lunar outpost will be
61
sent to the moon. Some examples of probes being sent to the moon are the Lunar
Reconnaissance Orbiter and its child probe LCROSS. The Lunar Reconnaissance Orbiter is
500kg lunar orbiter slated for launch in the fall of 2008. This orbiter is being sent to characterize
deep space radiation in lunar orbit, map the topography in selenodetic global topography, 0.5mm
maximum high resolution mapping to assist in the selection of future landing zones and the
probe will attempt to confirm the existence of lunar ice at the poles.
LCROSS, or Lunar Crater Observation and Sensing Satellite, will be launching with the Lunar
Recon Orbiter and the objective of this mission is for the probes centaur upper stage rocket to
impact the side of a permanently dark crater and analyze the plume of debris for any sign of the
lunar ice that was possibly discovered by the Clementine mission of 1994. Following this stage
the mission will end with LCROSS itself impacting on another part of the crater four minutes
after the other impact.
NASA's Robotic Lunar Exploration Program, which encompasses the LCROSS and LRO is
NASA’s first step toward establishing a lunar outpost and it is the correct first step in the
process. After LRO and LCROSS, NASA is planning on a robotic lunar lander mission in 2009
or 2010 and on having continuous lunar orbiters and surface probes until humans can arrive back
on the moon in 2020.
The next step toward the establishment should involve the use of four person teams of astronauts
engaging in reconnaissance trips to each of the lunar poles to further study sites selected through
the analysis of the information gathered from a decade of unmanned probes. For a period of a
year or two astronaut missions, through hands on analysis and further research on Earth a
suitable site should be able to be decided either at the north or south lunar pole.
62
Following the selection of the site for a lunar outpost pre-planned construction plans can be put
into action and construction of it can begin. For the initial construction stages of the base an
agency should maximize the capacity of the Orion spacecraft and send six astronauts up instead
of four, although the six man capacity is supposed to be reserved for any future Martian
expeditions. The first priority of construction crews should be the establishment of a solar power
array and the installation of communications equipment. The next mission should focus on
setting up the habitat which astronauts will be able to call home. This step is the most important
and will require the most missions in order to get life support, electronics, and filtration systems
online and in working order. More missions will be required to fix any bugs that may arise and
install scientific equipment. Eventually after about ten to fifteen missions varying in length
between one and two weeks the outpost should be able to sustain a crew of 10-12 for up to sixmonth long deployments.
After four to five years back on the moon humanity will have constructed a lunar base at either
the southern or northern lunar pole. The dimensions of the base that NASA is considering to
build will make it about the size of the Washington Mall (309.2 acres), this dimension includes
the landing zone and all other facilities required at the outpost. It is feasible to have crews of 1012 crew members serve at least six-month long tours at the lunar outpost. Ten crew members
would use the current capacity of two Orion Spacecraft, while twelve would need to use two of
the planned six-man version of the Orion, which at this point is only planned for use on a
mission to Mars. Since the six-man version of Orion probably will not be used then it would be
a crew of ten calling the moon home. This crew would have to be hand picked by a review board
to monitor several factors including age, sex, the ability to cope with isolation, and the ability to
work as a team for six-months or more.
63
The constitution of the ten man crew needs to be carefully though out, yet it is safe to say who
should go on a mission to the moon based on common sense. A crew of ten should consist of two
medical doctors, three engineers, three scientists, a mission commander, and a psychologist. The
two medical doctor system is the most important feature in the team because they will provide
for the physical well being of the crew and quickly diagnose any medical threats that could
damage the mission. Why not use one? In the event one medical doctor is incapacitated, it is
always prudent to have a back-up, especially in the harsh environment on the moon. Engineers
and scientists are always a good choice when assembling a team to live on and study the moon.
The engineers can work to make devices more efficient and fix problems that might arise. The
science team could run experiments much like on the ISS and space shuttle. For an effective
team of engineers and scientists, the selection criteria for a lunar outpost should include
engineers in the mechanical, aerospace, and the electrical and computer fields, as well as
scientists in the fields of physics, chemistry, and biology. The need for a psychologist arises out
of the fact that an agency running the outpost needs to make sure everything runs smoothly
among the crew in all situations regarding stress, home sickness, and overall tension that arises
from a small group confined to an area for a long period of time. The mission commander role is
necessary because someone needs to direct and remain in control of whatever situations may
arise. The constitution of the crew is probably the single most important issue facing any nation
or group of nations planning on setting up a permanent outpost on the moon.
With a lunar base set up and running smoothly, a space agency could have many options on how
to move forward. They could choose to expand and upgrade the current station or work to set up
more stations elsewhere. With the plans of multiple nations, including China, Japan, NASA,
India and Russia, and even private companies, Virgin Galactic and Bigelow Aerospace, either to
64
go to or to establish outposts on the moon in the next twenty years, the moon promises to
become an even hotter topic. At this point in time it is tough to imagine the conflicts that could
arise over Helium-3, lunar ice, and laws governing the moon.
The plan of a moon base should not be to just stay put with what is initially built but to
eventually upgrade and expand to open up the moon to more and more people. In the next fifty
years it is foreseeable that there will be a good number of lunar outposts as well as tourist resorts
on the moon. In a hundred years, if technology permits, we may see the formations of colonies of
people in the thousands on the lunar surface.
6. 2 Energy
If a lunar base is to be developed, one of the main concerns would be the way in which the base
would be powered. Many theories exist, but two of the most promising are the use of solar and
nuclear energy.
The creation of solar power plants remains one of the most feasible means of providing both
electrical and thermal energy. The technology for this method already been demonstrated here
on Earth and in space, such as on the Mir space station and the Hubble telescope.
A lunar day and a lunar night each lasts 336 hours, so for 336 hours in each of these cycles, there
needs to be a way of providing energy, even when a lunar base is receiving no direct sunlight.
One possibility is several “solar farms” placed at certain increments around the equator to
increase the amount of time that solar energy could be collected. A distance of 1500 km between
each plant, for example, would increase availability of solar energy by 24 hours, meaning that 14
plants at these distances would provide constant access to the sun’s energy. 42
65
Each of these plants would require about 50 to 100 square kilometers in order to produce roughly
10 gigawatts of power. The energy collected and stored at these plants could be transmitted back
to the lunar base either through power lines or wirelessly, using microwaves. There exist DC to
RF (Direct Current to Radio Frequency) converters that are 83% efficient, and once the
microwaves reach their destination, rectennas convert the microwave beam into electricity.
Current rectennas operate at more than 85% efficiency. In addition, microwaves at
approximately 2.45 GHz experience less than 1% attenuation while traveling through the Earth’s
atmosphere and normal precipitation and about 30% while traveling through heavy rain. On the
moon, such environmental factors would not even exist, and attenuation would be even less. The
photovoltaic panels themselves have about a 5% conversion rate. 43 The energy from photons
hitting the cells knocks loose electrons, and the remaining positive charges and electrons repel
each other, flowing through the semiconducting material, like silicon, creating an electric
current.
Alternatively, if a polar base site is chosen, solar power is by far the most easily implemented
long-term power source possible for a lunar base. With no atmosphere, there are no
environmental obstructions to getting sunlight save for the orbit of the moon itself. Solar cells, or
more specifically a “solar film”, can eventually provide up to a megawatt of power over several
years.44 This provides sufficient power to suit the needs of future colonists, at the very least
temporarily.
The state of present solar technology makes it practically ideal for not only use on the moon, but
manufacture there as well.45 This means that in addition to potentially meeting all the power
needs of a colony, the equipment would not need to be brought along in its entirety. The extra
66
space resulting from having only necessary parts to assemble power supplies on the moon, and
enough power resources to last until those were established would be invaluable.
Two features of the moon make construction of a film of solar cells possible: a vacuum
environment and the presence of the prerequisite materials in abundance on the surface. These
materials include iron, silicon, magnesium, calcium, aluminum, etc. Solar cell manufacture
requires a vacuum to take place, and is accomplished by laying down the required materials in
five layers: the substrate, the bottom electrode, N-type silicon, P-type silicon, antireflective
coating, and the top electrode.46
The moon’s environment is not without its drawbacks regarding construction, but much of this
can be resolved using robotics. Research into the specifications of this equipment has yet to be
fully investigated, but ultimately it would have to accomplish two tasks. Apparently, it would
need to be able to assemble the layers of the solar cells autonomously on the moon’s surface. In
addition to that, it would have to do any necessary resource gathering and purification.47
Furthermore, the environment after construction poses risks as well; with no atmosphere, the
moon is under a persistent bombardment of meteorites. A solar power network would have to
sprawl across large areas in order to not be critically damaged by this threat at any one time, and
damage would have to be regularly repaired. Were the same robots assigned to construct the
solar cells also designed with the ability to autonomously repair them, as well as the cells
themselves being distributed on varying areas of the moon, the risk would be greatly reduced. If
such technology is developed, and current knowledge of solar energy is implemented, solar
power on the moon is already in our grasp.
67
Nuclear power also remains promising, especially given the relative abundance of helium-3, a
relatively clean nuclear fusion reactant, on the moon. In addition, nuclear power would be
available at all times, not just during the day.
The reasons for an attraction to helium-3 for this use are many. Helium-3 is an isotope of helium
containing two protons and one neutron. In a fusion reaction involving helium-3 and deuterium,
a high-energy proton and alpha particle (a helium-4 ion), are produced. As a charged particle,
that proton could be contained in electric and magnetic fields, directly providing electrical
power. In addition, due to the structure of helium-3, these reactions produce few loose neutrons
that would activate materials in the structure of the power plant.
The idea of a fusion reaction has to do with the binding energies of the reactants involved. In the
case of He-3 and deuterium, the following reaction occurs:
2
1H
+ 32He -> 42He + 11p 48
After this reaction occurs, the resulting sum of masses is slightly less than thes sum of masses of
the reactants. This difference in mass is known as the mass defect, and it is accounted for by a
release of energy, given by Einstein’s famous equation, E = mc2, which can be re-written using
conversion factors to obtain:
Eb = (Z * mH + N * mn – misotope) * 931.5 MeV / amu
Where:
Eb = binding energy, in MeV
Z = number of protons
mH = mass of a hydrogen atom, in amu
N = number of neutrons
68
mn = mass of a neutron, in amu
misotope = mass of the isotope
In the case of the above reaction, the amount of energy produced is about 18.4 MeV, meaning
that there is a mass defect of 18.4 MeV / (931.5 MeV / amu) = 0.0198 amu. 49
A large-scale mining operation would be necessary to make use of this valuable resource. There
are several favorable locations for this, such as at the poles, on the far side of the moon, or in the
Mare Tranquillitatis.
The reasoning for favoring the far side of the moon is that the Earth's magnetotail shields the
moon's near side for about a week per month, resulting in less depositing of solar-windimplanted gases, or SWIs, on the near side. The far side, then, experiences a larger average flux
of solar wind, which results in a greater amount of SWIs. 50
The poles are also a good candidate for location because temperatures there are more constantly
lower than at other locations on the moon, and the desorption rate of implanted gases is directly
proportional to the expression exp(-U/kt), where U is the activation energy, the energy that must
be overcome for a reaction to occur, to k is the Boltzmann constant, and t is the temperature.
This means that as temperature decreases, desorption dramatically decreases, meaning that SWIs
like helium-3 have a longer surface residence time in colder temperatures. 51
And the Mare Tranquillitatis is a good candidate because there is a direct correlation between
titanium concentration and helium-3, and the Apollo 11 and 17 missions demonstrated the
abundance of titanium-rich mare in the southern and northern regions, respectively, of this Sea of
Tranquility.
69
Even though there is much more helium-3 on the moon than here on Earth, the concentration of
helium-3 on the moon is still quite small. This means that millions of tons of regolith would need
to be processed in order to extract a decent amount of helium-3. Whether or not this is
economically feasible might have to depend on whether the mining of helium-3 "piggybacks" on
mining operations for other resources on the moon. In addition, the technology for all of this,
especially fusion technology such as inertial electrostatic confinement, the use of an electrostatic
field to contain plasma during a fusion reaction, still needs to be further developed.
The most feasible method of providing energy is through solar power. Perhaps one day we will
have the technology to mine He-3 on the moon and harvest its energy from fusion reactions, but
as of now, the technology simply does not exist, while the technology for solar power both exists
and is widely used. If we are to see a lunar base happen in our lifetime, we need to make use of
what we already know to be effective, and take relatively unnecessary technological risks later.
6.3 Personnel
The number of people we send to the moon at first needs to be a balance between the human
resources available to construct and run the moon and resources necessary to sustain those
humans. While people could perform multiple tasks, certain tasks are specialized or timeconsuming and would require one person to dedicate all his time to it.
There would be many opportunities for work on a lunar base, whether they are in the
government, law enforcement, sanitation, operation of facilities for an energy source, such as a
fusion reactor or maintenance of solar panels, geology for the study of the moon, and astronomy
for the observation of near-Earth objects.
70
One of the most critical parts of the colony’s personnel would be two or more doctors to take
care of emergencies and medical check-ups, and to ensure that the crew is in good health and that
the physiological effects of living on the moon – muscle atrophy, radiation, etc. – are within
normal limits. While not working as doctors, they could perform as “farmers”, cultivating plants
using hydroponics as a secondary food source and lightening the load of cargo sent from Earth.
There should be several engineers to control robots that would do a large portion of construction
and excavation. Geologists would be required to explore the landing site for materials that can be
mined. All in all, the crew of the lunar base could contain about ten people and still address the
main necessities of the base – construction, food, and medical care. Anything else would be, at
first, an unnecessary luxury.
People that should not be sent to the moon, at least until a well-developed society with full
medical supplies is in place – are fertile women. The possibility of babies being conceived or
even born in space is too much of a risk, both to the child and to the rest of the crew. Babies are
especially susceptible to prenatal radiation exposure. When the unborn child is only a cluster of
cells, damage to a cell can cause death of the embryo. In addition, if a child is brought to term
and born, the child would require constant attention, special dietary restrictions, frequent medical
care, and other supplies not readily available if not prepared for.
6.4 Resources
There are many technical and economic challenges associated with a lunar base. It would cost
about $25,000 per pound to ship materials to the moon. This extensive cost will make it a
necessity to either mine or manufacture most of the materials needed for an outpost on the moon.
In a crater basin it might be possible to extract water for drinking and farming as well as oxygen
71
from ice crystals deposited by comets or asteroids. Some data suggests that some craters could be
holding hundreds of millions of metric tons of water ice. This ice has been deposited there from
billions of years of comet impacts.
Strip-mining regolith could be used to get calcium, nitrogen and hydrogen-free silicon. Calcium
can be used to make cement, nitrogen can be used for farming and hydrogen-free silicon can be
used to make glass and ceramics whose crystal structures are potentially structurally superior to
those made on Earth. Silicon can be passivated by hydrogen and this can cause light induced
degradation of the material. The lunar soil also contains useful elements like titanium, iron and
aluminum.
In order to take care of food and water, at first supplies would likely have to be delivered directly
from Earth. Later, though, there is the possibility of growing vegetables in a greenhouse and
using hydroponics and a blend of incandescent and fluorescent lights, and breeding animals for
food.
Another way to help reduce the amount of outside resources needed to be shipped from Earth is
an efficient recycling system. Once water is delivered from Earth, much of it can be recycled at
about 97% efficiency from urine and water vapor exhaled by human inhabitants and the possible
animals, much like it is on the International Space Station (ISS). Over time, human water output
is roughly 0.1% less than water input. In one day, a human consumes roughly 1000 mL of water
by drinking, 1200 mL from food, and 300 mL from metabolizing food. Humans excrete roughly
1650 mL, sweat 500 mL, and exhale 350 mL. 52 Daily, each human would require 2500 mL of
water, from which slightly less than 2422.6 mL can be recovered, with a loss of more than 77.4
mL per person per day. Therefore, eventually, water would have to be either delivered or mined
72
from somewhere else. However, any future transfer of water would be in far smaller quantity
than the initial transfer.
One such alternative location for acquiring water would be from the moon itself, in the form of
lunar ice. Scientist Harrison Brown and his associates first brought up polar ice in early 1960.
On the lunar surface, the bottoms of some polar meteor craters never receive any sunlight—the
moon has an estimated 14,000 km2 of these areas. Brown reasoned that when a meteor
containing ice hits the lunar surface, most water molecules would vaporize but some would get
trapped in these permanently dark areas. These molecules build up over the moon’s long, multibillion year history, and may have amassed into a large quantity of collectable ice.
For safety reasons, the Apollo missions were performed near the moon’s equator. Samples of
lunar rock that were brought back to Earth were completely dry. A Lunar Polar Orbiter was
planned that would map the chemical composition of the lunar surface. However, this was later
canceled and public interest in the possibility of lunar ice died out. Under the Reagan
administration, public interest again waned toward space exploration, this time in the form of
developing technology for ballistic defense.
In 1998, NASA sent the unmanned Clementine Lunar Prospector to orbit our moon for 18
months. Clementine found large amounts of hydrogen in the moon’s south pole by bouncing
radio waves off of the lunar surface and comparing the bounced waves with those from ice. This
may indicate that hundreds of millions of tons of ice are available for mankind to harvest. Since
then, there has been no new information concerning lunar ice—whether or not there is ice on the
moon and if it exists in usable quantities.
73
NASA is currently planning to send the Lunar Reconnaissance Orbiter (LRO) in October of
2008. This is, according to NASA, the best chance we will have to resolve the lunar ice debate
from orbit. If the LRO has positive results, it could pave the way for a robotic expedition on the
surface. The French currently have the SMART-1 orbiting the moon, armed with an infrared
spectrometer to try to gather more evidence for the existence of ice. However, if the ice is
sparsely embedded in layers of dry rock, a sample taken from the surface will be necessary.
So far, all that can be confirmed is the existence of hydrogen. This can either be ice trapped in
dark areas of the moon, as described earlier, or the hydrogen can be fixed to the surface from
billions of years of solar wind. Either way, NASA will be able to make use of the hydrogen. If
it exists in the form of water, oxygen and hydrogen can be extracted using electrolysis.
Hydrogen is highly valuable to NASA’s efforts and the prospect of lunar colonization because it
is an essential ingredient in rocket fuel. If hydrogen could be collected, in one way or another,
directly from the moon instead of bringing it all from Earth, not only would the moon be more
independent of Earth’s resources, but also it would be able to be a launching point – promoting
more effective and profitable space exploration beyond the moon itself.
6.5 Location
A suitable location for a lunar base must be chosen. Some areas have advantages over others.
The poles of the moon show the most promise. One advantage of the poles is the temperature
varies moderately ranging from negative 30 degrees Celsius to negative 50 degrees Celsius,
compared to the high temperature at the equator of 132 degrees Celsius. A greater advantage the
poles have is its resources. Near the south pole, there are high crater rims that are almost
continuously exposed to sunlight. This would serve as an excellent place to construct sun-
74
tracking solar arrays that could provide nearly constant power. In addition, if some of this power
was stored in batteries then they could be relied on during the short periods of darkness.
6.6 Law
There are laws that various governments have already agreed upon regarding space travel. They
have suited us well when there have not been permanent residents of space, but when that comes
about they may become antiquated and require revision. Case in point, there is no distinct
provision for land ownership on the moon. Although some have tried to cash in selling land on
the moon, no one can technically own any celestial body or any part of space. In 1955, Robert
R. Coles sold acres at one dollar a piece, and in 1966 the town council of Geneva, Ohio created a
Declaration of Lunar Ownership, where they take “full possession and responsibility” of the
moon. However, the United Nations (UN) outlined rules and regulations regarding the
exploration of space long ago.
There are numerous other treaties that govern nations’ ability to explore the stars. The United
Nations Office for Outer Space Affairs (UNOOSA) was formed to promote international
cooperation between different nations in using outer space for peaceful and beneficial purposes.
In 1962, UNOOSA wrote the Declaration of Legal Principles Governing the Activities of States
in the Exploration and Use of Outer Space. Regarding the ownership of space, it states that
“outer space, including the moon and other celestial bodies, is not subject to national
appropriation by claim of sovereignty, by means of use or occupation, or by any other means.”
UNOOSA, under the Convention on the Registration of Objects Launched into Outer Space (The
Registration Convention) of 1974, distributes studies and research publications on space travel
and the technology surrounding it, making information available to smaller countries looking to
75
join in the arms race. They also maintain and monitor an index of all objects launched into outer
space since 1957. Companies or individuals wishing to place a satellite in orbit need to be able
to put it in a place that is not only useful to them, but is free of other satellites in the immediate
area and their orbital paths. This information is made freely available over the internet, indexed
by factors such as launch date, whether it is nuclear powered and the type of orbit it has, for
example.
In addition, UNOOSA declared a series of legal principles that outline the attitudes nations and
companies must have while exploring the depths of space. This is known as space law, and is
defined by five core principles and five international treaties. Principles and treaties being that
the treaties are binding to the countries that ratified them, while the principles tend to shape the
treaties and procedures employed. As UNOOSA says on their website, “The primary goals of
space law are to ensure a rational, responsible approach to the exploration and use of outer space
for the benefit and in the interests of all humankind.”
The Declaration of Legal Principles Governing the Activities of States in the Exploration and
Use of Outer Space states that all exploration should be done for the benefit of all counties. This
includes using any sort of nuclear or weaponized satellite, as well as not using any natural
satellites (the moon) for anything but peaceful purposes. The Principles Governing the Use by
States of Artificial Earth Satellites for International Direct Television Broadcasting of 1982
takes care of international conflicts and rights of countries concerning TV satellites, as well as
mandating that the UN be notified for any object to be sent into space. Principles Relating to
Remote Sensing of Earth from Outer Space says that remote sensing, which includes using the
properties of electromagnetic waves emitted or reflected from the planet’s surface, “shall be
carried out for the benefit and in the interests of all countries, irrespective of their degree of
76
economic, social or scientific and technological development, and taking into particular
consideration the needs of the developing countries.” There is also principle concerning the use
of nuclear power on satellites, making a clear distinction between nuclear power and nuclear
weapons, and a principle outlining international cooperation. The latter is more fully explained
in the treaties UNOOSA has put forward.
The Treaty on Principles Governing the Activities of States in the Exploration and use of Outer
Space, Including the Moon and Other Celestial Bodies (The Outer Space Treaty) calls out to
different nations to help each other in an effort to bring together as much help as possible in
order to develop the technology needed for space travel. They go as far as mandating that “in
order to promote international co-operation… [Other nations shall] be afforded an opportunity to
observe the flight of space objects launched by those States.” In the Agreement on the Rescue of
Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space,
UNOOSA mandates that in times of emergency one nation should do everything in its power to
help astronauts of a different nation, reasoning that astronauts are “envoys of mankind” and must
be highly regarded as such. In cases of emergency, astronauts and space objects recovered on
foreign soil must be returned to their original owners with full cooperation.
The Convention on the International Liability for Damage Caused by Space Objects takes into
account any international conflict that could occur from space exploration in lower Earth orbits.
For example, if a satellite were to crash into Earth and land on foreign soil, the original owners
of that equipment have a right to collect it. The fact that a craft has traveled and left a nation or
gone through space does not change its ownership. If said equipment damages property in
foreign land, the nation that own the equipment must take responsibility for damages. “Each
State… that launches…an object into outer space… is internationally liable for damage to
77
another State Party to the Treaty…in air or in outer space, including the moon and other celestial
bodies.”
The creation of such a document seems so useless, as only a select few nations have put anything
in space, and even fewer put something manned in space. With the exception of certain specific
issues with communication satellites, many of the articles they lay out do not apply to anything.
Like most UN treaties, countries are free to drop out with no real consequences (since the UN
has limited resources for enforcing the regulations it creates). It is easy for a country to ratify a
treaty that will have no effect on them, but as space exploration becomes more relevant to
smaller countries, their participation in UN space law may change.
However, the UN has looked past that and has prepared for the future of space travel and the
political and environmental hazards that may come about as a result. Meetings are regularly
called in, usually concerning communications satellites. However, as technology improves and
space activity becomes more relevant, international space law will be updated to reflect such
change. States effected by UNOOSA’s principles and regulations include The US, The UK,
France, Germany, Japan, Russia, Argentina, Australia, Canada, Finland, Hungary, Indonesia,
New Zealand, Philippines, Korea, Slovakia, Sweden, South Africa, Tunisia, and Ukraine.
However, some countries will only ratify one of the five treaties, for example. The Outer Space
Treaty has been ratified by 98 countries, while The Registration Convention has only been
ratified by 46 countries. Space exploration that may be done in the future by private companies
are subject to the regulations that the particular country signed to.
78
Conclusions
The exploring spirit has historically led mankind to conquer and inhabit uncharted territory.
While humankind has shown its dominance on Earth, there still remains the impossibly large
final frontier of space. The first steppingstone to inhabiting space is the colonization of our
closest celestial body, the Moon. With current technology and appropriate funding, a lunar base
could already exist. To accomplish this on a more realistic budget, further development is
needed in protecting humans from the dangers of space, artificial intelligence, robotics and longdistance transportation. Also required is an understanding of the psychological and humanitarian
aspects of space travel. A fully functioning Moon base would fully disclose its benefits for
humanity as a near-Earth object detection post, spaceport to the planets, and a helium-3 mining
operation—something that may eventually bring an end to our planet’s energy crisis. The future
is ripe with the endless applications a functioning Moon base could enable. This is an essential
step and learning opportunity that will be relied upon to prepare for more ambitious endeavors to
Mars and beyond. While what the future holds may be unknown, it is decidedly certain that the
future will entail humanity in space.
Recommendations for future IQPs
After completing our IQP on humanity and space it is easy to see several areas that a future
project could build on. Taking into account areas of our IQP namely moon colonization and
transportation technology it is clear that each section could in fact be expanded into more
detailed IQPs. The humanity and space project was a broad survey into all the aspects of getting
to and colonizing the moon and not focused on a specific sub-topic.
79
In further studies of space transportation technologies it is recommended that groups engage in
projects focusing less on current and near-future NASA technology for space exploration and
look into alternative technologies that are possible and technologies contemplated for use by
other nations. In regards to alternative technologies nuclear pulse propulsion and the use of
nuclear power on spacecraft should be looked at on all levels legally, socially, and economically
to see whether or not humanity could live with sanctioning the use of nuclear technology and
allowing it to circumnavigate the test ban treaty of 1963. The space elevator could also be
studied further and developed into another IQP focusing on the economic and social impacts of
constructing the elevator.
In regards to moon colonization future IQPs can easily build upon a large number of areas in the
sub-sections dealing with this topic. In a future project a group of students could create a more
detailed mapping of how a moon base would be set up and calculate what methods would be the
most economical. If the sole objective of an IQP was to establish a complete and detailed
blueprint for the establishment of a colony on the moon it would be able to go into a lot more
detail than our project was able to. This project attempts to give a broad and lightly detailed
perspective on the requirements for the establishment of a lunar outpost. A future project should
and can easily build upon this by further establishing more refined blueprints for the
establishment of a lunar base.
80
Bibliography
1
Zubrin, Robert. Entering Space: Creating a Spacefaring Civilization. New York: Putnam Books, 1999, p. 131.
2
Zubrin, Robert. Entering Space: Creating a Spacefaring Civilization. New York: Putnam Books, 1999, pp. 128-129.
3
Zubrin, Robert. Entering Space: Creating a Spacefaring Civilization. New York: Putnam Books, 1999, p. 136.
4
Morrison, David. "Congressional Bills Supporting NEO Surveys." Asteroid and Comet Impact Hazards, 26 Mar 2004 07 Oct
2007 <http://impact.arc.nasa.gov/news_detail.cfm?ID=138>.
5
"Global dimming." Wikipedia, The Free Encyclopedia. 6 Sep 2007, 19:44 UTC. Wikimedia Foundation, Inc. 6 Sep 2007
<http://en.wikipedia.org/w/index.php?title=Global_dimming&oldid=156116006>
6
Appell, David. "The Darkening Earth Less sun at the Earth's surface complicates climate models", Scientific American, 200408-02 <http://www.sciam.com/article.cfm?articleID=000C3AAE-D82A-10F9-975883414B7F0000>
7
Adam, David. "Goodbye Sunshine", The Guardian, 2003-12-18
http://www.guardian.co.uk/science/2003/dec/18/science.research1
8
Travis, D.J., Carleton, A.M., DeGrand, J.Q., and J.S. Johnson (2005). "U.S. Jet Contrail Frequency Changes: Influences of Jet
Aircraft Flight Activity and Atmospheric Conditions." The International Journal of Climate, Submitted.
9
Spinoff 1996. Retrieved November 12, 2007, from http://www.sti.nasa.gov/tto/spinoff1996/contents.html
10
Mangir, Tulin E.. "The Future of Public Satellite Communications.” Aerospace Application Conference Proceedings (1996):
398-399.
11
Mangir, Tulin E.. "The Future of Public Satellite Communications." Aerospace Application Conference Proceedings (1996):
397-398.
12
Yen, Les. "Satellite Communications for the Millenium." Antennas and Propagation Society International Symposium (2000):
530.
13
Landis, Geoffrey A.. "Reevaluating Satellite Power Systems for Earth." Conference Record of the 2006 IEEE 4th World
Conference on Photovoltaic Energy Conversion (2006): 1940.
15
Cahill, Daniel F.. "An Overview of Satellite Power Systems -- Microwave Health and Ecology Program." MTT-S International
Microwave Symposium Digest (1979): 35-36.
16
Buhler, Charles. “Analysis of a Lunar Base Electrostatic Radiation Shield Concept” ASRC Aerospace Corporation Phase I.
April 28, 2005 http://www.niac.usra.edu/files/studies/final_report/921Buhler.pdf
17
Malik, Tarig. “NASA Researchers Say Space Radiation a Top Concern for Future Manned Missions.” Business Technology 17
May 2004 Space.com Sept. 2007. <http://www.space.com/scienceastronomy/radiation_risk_040517.html>
18
Donald, James. "The Space Shuttle Extravehicular Mobility Unit (EMU)." NASA Quest. NASA. 20 Feb 2008
<http://quest.nasa.gov/space/teachers/suited/5emu1.html>
19
Buhler, Charles. “Analysis of a Lunar Base Electrostatic Radiation Shield Concept” ASRC Aerospace Corporation Phase I.
April 28, 2005 <http://www.niac.usra.edu/files/studies/final_report/921Buhler.pdf>
20
Tripathi, Ram K.. "Electrostatic Active Radiation Shielding - Revisited." Aerospace Conference, 2006 IEEE (2006): 5.
21
Tripathi, Ram K.. "Electrostatic Active Radiation Shielding - Revisited." Aerospace Conference, 2006 IEEE (2006): 5.
22
Buhler, Charles. “Analysis of a Lunar Base Electrostatic Radiation Shield Concept” ASRC Aerospace Corporation Phase I.
April 28, 2005 <http://www.niac.usra.edu/files/studies/final_report/921Buhler.pdf>
81
23
"Possible effects of Electromagnetic Fields (EMF) on Human Health." EUROPA - European Commission. 21 Mar 2007.
Scientific Committee on Emerging and Newly Identified Health Risks. 6 Oct 2007
<http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_007.pdf>.
24
Malik, Tarig. “Shields Up! New Radiation Protection for Spacecraft and Astronauts.” Business Technology 27 May 2004
Space.com Sept. 27 2007 <http://www.space.com/businesstechnology/technology/rad_shield_040527.html>
25
Malik, Tarig. “Shields Up! New Radiation Protection for Spacecraft and Astronauts.” Business Technology 27 May 2004
Space.com Sept. 27 2007 http://www.space.com/businesstechnology/technology/rad_shield_040527.html
26
Barry, Patrick. "Plastic Spaceships." SCIENCE@NASA. 25 August 2005. NASA. 29 Jan 2008
<http://science.nasa.gov/headlines/y2005/25aug_plasticspaceships.htm>
27
Buchanan, Bruce G. (2005), "A (Very) Brief History of Artificial Intelligence", AI Magazine: 53-60,
<http://www.aaai.org/AITopics/assets/PDF/AIMag26-04-016.pdf>. Retrieved on 30 August 2007
28
NASA Develops Robust Artificial Intelligence for Planetary Rovers. Sept 8, 2004.
<http://www.nasa.gov/vision/universe/roboticexplorers/robust_artificial_intelligence_jb.html>
29
Collaborative Decision Systems Shown. October, 2005 <http://ase.arc.nasa.gov/news/story.php?id=301>
30
“Adaptive Control and Evolvable Systems” <http://ase.arc.nasa.gov/tech/groups/index.php?gid=16&ta=2>
31
“’Borg’ Computer Collective Designs NASA Space Antenna.” February 16, 2006.
<http://www.nasa.gov/centers/ames/research/exploringtheuniverse/borg.html>
32
NASA Evolutionary Software Automatically Designs Antenna
<http://www.spaceref.com/news/viewpr.html?pid=14394>
33
Thompson, Adrian. Evoltionary Electronics at Susses. <http://www.cogs.susx.ac.uk/users/adrianth/>
34
Bellows, Alan. On the Origin of Circuits. June 27th, 2007. <http://www.damninteresting.com/?p=870>
35
Baard, Erik. "Robotic Pair Planned as First Lunar Colonists." Space.com Sep 2000. 4 Oct 2007
<http://www.space.com/missionlaunches/missions/moon_doggies_000918.html>.
36
Robonaut ed. Ryan Necessary. 04 Oct. 2004. 04 Oct. 2007. <http://robonaut.jsc.nasa.gov/robonaut.html>
37
"Ares I." Wikipedia, The Free Encyclopedia. 14 Sep 2007, 05:36 UTC. Wikimedia Foundation, Inc. 21 Sep 2007
<http://en.wikipedia.org/w/index.php?title=Ares_I&oldid=157790809>
38
"Ares V." Wikipedia, The Free Encyclopedia. 18 Sep 2007, 23:37 UTC. Wikimedia Foundation, Inc. 21 Sep 2007.
<http://en.wikipedia.org/w/index.php?title=Ares_V&oldid=158837740>
39
"Orion (spacecraft)." Wikipedia, The Free Encyclopedia. 17 Sep 2007, 20:40 UTC. Wikimedia Foundation, Inc. 21 Sep 2007
<http://en.wikipedia.org/w/index.php?title=Orion_%28spacecraft%29&oldid=158573222>
40
"Lunar Surface Access Module." Wikipedia, The Free Encyclopedia. 14 Sep 2007, 19:39 UTC. Wikimedia Foundation, Inc. 21
Sep 2007 <http://en.wikipedia.org/w/index.php?title=Lunar_Surface_Access_Module&oldid=157908872>
41
Frank, Adam. "Gravity's Rim." Discover Magazine oct 1994. 09 Dec 2007
<http://discovermagazine.com/1994/sep/gravitysrim419/article_view?b_start:int=0&-C=>
42
Koelle, H., & Lo, R. (1997). Strategies of developing advanced lunar power systems. Acta Astronautica, 41(12), 817-823.
43
Dickinson, R. M. (2003). Wireless power transmission technology state of the art the first bill brown lecture. Acta
Astronautica, 53(4-10), 561-570
82
44
Ignatiev, A.. " In-situ electric power generation to support solar system exploration and colonization: manufacture of thin film
silicon solar cells on the Moon." Aerospace Conference, IEEE proceedings (2001): 1.
45
Ignatiev, A.. " In-situ electric power generation to support solar system exploration and colonization: manufacture of thin film
silicon solar cells on the Moon." Aerospace Conference, IEEE proceedings (2001): 1.
46
Ignatiev, A.. " In-situ electric power generation to support solar system exploration and colonization: manufacture of thin film
silicon solar cells on the Moon." Aerospace Conference, IEEE proceedings (2001): 2.
47
Ignatiev, A.. " In-situ electric power generation to support solar system exploration and colonization: manufacture of thin film
silicon solar cells on the Moon." Aerospace Conference, IEEE proceedings (2001): 1.
48
Cramer, G. There's helium-3 in them there moon hills. Retrieved January 15, 2008, from
http://www.direct.ca/trinity/helium3.htm
49
Fusion: Binding energy. October 5, 2007. <http://library.thinkquest.org/17940/texts/binding_energy/binding_energy.html>
50
Fa, W., & Jin, Y. (2007). Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer. Icarus, 190(1), 1523.
51
Starukhina, L. V. (2006). Polar regions of the moon as a potential repository of solar-wind-implanted gases. Advances in Space
Research, 37(1), 50-58.
52
Water input and output. Retrieved November 20, 2007, from http://www.healthyeatingclub.com/info/booksphds/books/foodfacts/html/maintext/fig18.html
83

Similar documents

×

Report this document