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Mining Space
On December 10, 1986 the Greater New York Section of the
American Institute of Aeronautics and Astronautics (AIAA) and the
engineering section of the New York Academy of Sciences jointly
presented a program on mining the planets. Speakers were Greg
Maryniak of the Space Studies Institute (SSI) and Dr. Carl
Peterson of the Mining and Excavation Research Institute of
M.I.T.
Maryniak spoke first and began by commenting that the
quintessential predicament of space flight is that everything
launched from Earth must be accelerated to orbital velocity.
Related to this is that the traditional way to create things in
space has been to manufacture them on Earth and then launch them
into orbit aboard large rockets. The difficulty with this
approach is the huge cost-per-pound of boosting anything out of
this planet's gravity well. Furthermore, Maryniak noted, since
(at least in the near to medium term) the space program must
depend upon the government for most of its funding, for this
economic drawback necessarily translates into a political
problem.
Maryniak continued by noting that the early settlers in
North America did not attempt to transport across the Atlantic
everything then needed to sustain them in the New World. Rather
they brought their tools with them and constructed their habitats
from local materials. Hence, he suggested that the solution to
the dilemma to which he referred required not so much a shift in
technology as a shift in thinking. Space, he argued, should be
considered not as a vacuum, totally devoid of everything.
Rather, it should be regarded as an ocean, that is, a hostile
environment but one having resources. Among the resources of
space, he suggested, are readily available solar power and
potential surface mines on the Moon and later other celestial
bodies as well.
The Moon, Maryniak stated, contains many useful materials.
Moreover, it is twenty-two times easier to accelerate a payload
to lunar escape velocity than it is to accelerate the identical
mass out of the Earth's gravity well. As a practical matter the
advantage in terms of the energy required is even greater because
of the absence of a lunar atmosphere. Among other things this
permits the use of devices such as electromagnetic accelerators
(mass drivers) to launch payloads from the Moon's surface.
Even raw Lunar soil is useful as shielding for space
stations and other space habitats. At present, he noted,
exposure to radiation will prevent anyone for spending a total of
more than six months out of his or her entire lifetime on the
space station. At the other end of the scale, Lunar soil can be
processed into its constituent materials. In between steps are
also of great interest. For example, the Moon's soil is rich in
oxygen, which makes up most of the mass of water and rocket
propellant. This oxygen could be "cooked" out of the Lunar soil.
Since most of the mass of the equipment which would be necessary
to accomplish this would consist of relatively low technology
hardware, Maryniak suggested the possibility that at least in
the longer term the extraction plant itself could be manufactured
largely on the Moon. Another possibility currently being
examined is the manufacture of glass from Lunar soil and using it
as construction material. The techniques involved, according to
Maryniak, are crude but effective. (In answer to a question
posed by a member of the audience after the formal presentation,
Maryniak stated that he believed the brittle properties of glass
could be overcome by using glass-glass composites. He also
suggested yet another possibility, that of using Lunar soil as a
basis of concrete.)
One possible application of such Moon-made glass would be in
glass-glass composite beams. Among other things, these could be
employed as structural elements in a solar power satellite (SPS).
While interest in the SPS has waned in this country, at least
temporarily, it is a major focus of attention in the U.S.S.R.,
Western Europe and Japan. In particular, the Soviets have stated
that they will build an SPS by the year 2000 (although they plan
on using Earth launched materials. Similarly the Japanese are
conducting SPS related sounding rocket tests. SSI studies have
suggested that more than 90%, and perhaps as much as 99% of the
mass of an SPS can be constructed out of Lunar materials.
According to Maryniak, a fair amount of work has already
been performed on the layout of Lunar mines and how to separate
materials on the Moon. Different techniques from those employed
on Earth must be used because of the absence of water on the
Moon. On the other hand, Lunar materials processing can involve
the use of self-replicating factories. Such a procedure may be
able to produce a so-called "mass payback ratio" of 500 to 1.
That is, the mass of the manufactories which can be established
by this method will equal 500 times the mass of the original
"seed" plant emplaced on the Moon.
Maryniak also discussed the mining of asteroids using mass-
driver engines, a technique which SSI has long advocated.
Essentially this would entail a spacecraft capturing either a
sizable fragment of a large asteroid or preferably an entire
small asteroid. The spacecraft would be equipped with machinery
to extract minerals and other useful materials from the
asteroidal mass. The slag or other waste products generated in
this process would be reduced to finely pulverized form and
accelerated by a mass driver in order to propel the captured
asteroid into an orbit around Earth. If the Earth has so-called
Trojan asteroids, as does Jupiter, the energy required to bring
materials from them to low Earth orbit (LEO) would be only 1% as
great as that required to launch the same amount of mass from
Earth. (Once again, moreover, the fact that more economical
means of propulsion can be used for orbital transfers than for
accelerating material to orbital velocity would likely make the
practical advantages even greater.) However, Maryniak noted that
observations already performed have ruled out any Earth-Trojan
bodies larger than one mile in diameter.
In addition to the previously mentioned SPS, another
possible use for materials mined from planets would be in the
construction of space colonies. In this connection Maryniak
noted that a so-called biosphere was presently being constructed
outside of Tucson, Arizona. When it is completed eight people
will inhabit it for two years entirely sealed off from the
outside world. One of the objectives of this experiment will be
to prove the concept of long-duration closed cycle life support
systems.
As the foregoing illustrates, Maryniak's primary focus was
upon mining the planets as a source for materials to use in
space. Dr. Peterson's principal interest, on the other hand, was
the potential application of techniques and equipment developed
for use on the Moon and the asteroids to the mining industry here
on Earth. Dr Peterson began his presentation by noting that the
U.S. mining industry was in very poor condition. In particular,
it has been criticized for using what has been described as
"neanderthal technology." Dr. Peterson clearly implied that such
criticism is justified, noting that the sooner or later the
philosophy of not doing what you can't make money on today will
come back to haunt people. A possible solution to this problem,
Dr. Peterson, suggested, is a marriage between mining and
aerospace.
(As an aside, Dr. Peterson's admonition would appear to be
as applicable to the space program as it is to the mining
industry, and especially to the reluctance of both the government
and the private sector to fund long-lead time space projects.
The current problems NASA is having getting funding for the space
station approved by Congress and the failure begin now to
implement the recommendations of the National Commission on Space
particularly come to mind.)
Part of the mining industry's difficulty, according to Dr.
Peterson is that is represents a rather small market. This tends
to discourage long range research. The result is to produce on
the one hand brilliant solutions to individual, immediate
problems, but on the other hand overall systems of incredible
complexity. This complexity, which according to Dr. Peterson has
now reached intolerable levels, results from the fact that mining
machinery evolves one step at a time and thus is subject to the
restriction that each new subsystem has to be compatible with all
of the other parts of the system that have not changed. Using
slides to illustrate his point, Dr. Peterson noted that so-called
"continuous" coal mining machines can in fact operate only 50% of
the time. The machine must stop when the shuttle car, which
removes the coal, is full. The shuttle cars, moreover, have to
stay out of each others way. Furthermore, not only are
Earthbound mining machines too heavy to take into space, they are
rapidly becoming too heavy to take into mines on Earth.
When humanity begins to colonize the Moon, Dr. Peterson
asserted, it will eventually prove necessary to go below the
surface for the construction of habitats, even if the extraction
of Lunar materials can be restricted to surface mining
operations. As a result, the same problems currently plaguing
Earthbound mining will be encountered. This is where Earth and
Moon mining can converge. Since Moon mining will start from
square one, Dr. Peterson implied, systems can be designed as a
whole rather than piecemeal. By the same token, for the reasons
mentioned there is a need in the case of Earthbound mining
machinery to back up and look at systems as a whole. What is
required, therefore, is a research program aimed at developing
technology that will be useful on the Moon but pending
development of Lunar mining operations can also be used down here
on Earth.
In particular, the mining industry on Earth is inhibited by
overly complex equipment unsuited to today's opportunities in
remote control and automation. It needs machines simple enough
to take advantage of tele-operation and automation. The same
needs exist with respect to the Moon. Therefore the mining
institute hopes to raise enough funds for sustained research in
mining techniques useful both on Earth and on other celestial
bodies as well. In this last connection, Dr. Peterson noted that
the mining industry is subject to the same problem as the
aerospace industry: Congress is reluctant to fund long range
research. In addition, the mining industry has a problem of its
own in that because individual companies are highly competitive
research results are generally not shared.
Dr. Peterson acknowledged, however, that there are
differences between mining on Earth and mining on other planetary
bodies. The most important is the one already mentioned-heavy
equipment cannot be used in space. This will mean additional
problems for space miners. Unlike space vacuum, rock does not
provide a predictable environment. Furthermore, the constraint
in mining is not energy requirements, but force requirements.
Rock requires heavy forces to move. In other words, one reason
earthbound mining equipment is heavy is that it breaks. This
brute force method, however, cannot be used in space. Entirely
aside from weight limitations, heavy forces cannot be generated
on the Moon and especially on asteroids, because lower gravity
means less traction. NASA has done some research on certain
details of this problem, but there is a need for fundamental
thinking about how to avoid using big forces.
One solution, although it would be limited to surface
mining, is the slusher-scoop. This device scoops up material in
a bucket dragged across the surface by cables and a winch. One
obvious advantage of this method is that it by passes low gravity
traction problems. Slushers are already in use here on Earth.
According to Peterson, the device was invented by a person named
Pat Farell. Farell was, Peterson stated, a very innovative
mining engineer partly because be did not attend college and
therefore did not learn what couldn't be done.
Some possible alternatives to the use of big forces were
discussed during the question period that followed the formal
presentations. One was the so called laser cutter. This,
Peterson indicated, is a potential solution if power problems can
be overcome. It does a good job and leaves behind a vitrified
tube in the rock. Another possibility is fusion pellets, which
create shock waves by impact. On the other hand, nuclear charges
are not practical. Aside from considerations generated by
treaties banning the presence of nuclear weapons in space, they
would throw material too far in a low gravity environment.
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