Mining In Space
On December 10, 1986 the Greater
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, 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 solar power and potential surface mines on the Moon and 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 from 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 USSR, 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, 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. Part of the mining industry's difficulty, according to Dr. Peterson, is that it 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 are left unanswered. 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: 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.