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Mining in 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 EarthUs
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 MoonUs 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 MoonUs soil is rich in oxygen,
which makes up most of the mass of water and rocket propellant. This
oxygen could be RcookedS 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 s 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 Rmass payback ratioS 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 RseedS 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, MaryniakUs primary focus was upon mining
the planets as a source for materials to use in space. Dr. PetersonUs
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
Rneanderthal technology. S Dr. Peterson clearly implied that such
criticism is justified, noting that the sooner or later the philosophy of
not doing what you canUt 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. PetersonUs 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 industryUs 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 RcontinuousS 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 todayUs 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 couldnUt 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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