Fabbers in Space

by Marshall Burns, Ph.D.
Copyright © 1999, Ennex Corporation

     If the European settlers had had to bring with them the lumber from which to build their homes and factories, the American colonies would never have been feasable. The United States was able to get started because the continent was carpeted with the most important raw material needed for construction: wood. The settlers brought with them axes and saws and hammers and barrels of nails, the tools and supplementary materials that were used to shape the forests of America into buildings, towns, and ultimately a powerful nation.

     People wonder why, after more than a dozen successful Apollo missions, NASA didn’t continue to send more people to the moon and eventually build a colony and a civilization there. But the reason is easy to see. The Apollo missions were self-contained living stations, like the ships that carried the explorers and later the settlers to America. In order to advance beyond temporary missions, we would have needed to build permanent homes, laboratories, observatories, and the rest of a productive infrastructure.

     Ironically, however, just as America was rich in the raw materials needed for growth, the moon also is blanketed with the most important raw materials needed for construction — iron and aluminum. The lunar soil consists largely of a fine powder of pulverized rocks rich in these and other important minerals. The problem was that in 1969, as the world waited to see what NASA would do to carry on its extraterrestrial magic, there existed no analog for the European settlers’ axes and saws and hammers.

     NASA had no way to work the lunar soil as a construction material without transporting huge smelters and mills that could transform those raw minerals and give them useful shape and structure. The transportation costs of such massive equipment were prohibitive, as were the costs of transporting adequate construction materials to build a colony. So the dream of inhabiting our celestial neighbor slipped through our fingers.

     What we lacked in 1969, however, we have in 1999. The key enabling technology that has been created in the meantime is the fabber, or rapid prototyping machine. As the European settlers’ axes and saws and hammers allowed them to shape the raw materials at hand, fabbers, properly designed and configured to work with the indigenous lunar regolith, could take the soil and form it into blocks, pipes, and hand tools that would allow astronauts to build their homes, laboratories, observatories, and other structures needed to sustain life and initiate lunar commerce.

Figure 9.4. Four possible concepts for a lunar fabber, which may be used to make tools, construction elements, and other necessities of life from native lunar soil. Focused sunlight provides the process energy. These concepts are adapted from processes currently used on Earth, shown counter-clockwise from top-left: • selective sintering of powder deposited on a descending bed, • deposition of molten droplets, • selective sintering on an uncontained powder bed. and • melting in place of an aimed powder stream. [Illustration from Using Fabricators to Reduce Space Transportation Costs]

     In a paper that Dave McKay, Hu Davis (both NASA legends), and I wrote for the 1996 Austin Solid Freeform Fabrication Symposium, we laid out four possible technology concepts for a lunar fabber. All used concentrated solar energy to provide the heat necessary to melt the regolith. Two were based on selective sintering, similar to a DTM Sinterstation, in which the laser is replaced by a solar collector. One worked by extruding a bead of molten material in a fashion similar to a Stratasys fused deposition modeler (FDM) or Genisys. And the fourth concept involved in-beam melting of a powder stream, similar to technologies now under development by Sandia National Laboratories, the University of Michigan, and Germany’s Fraunhofer Institute.

     This paper paid special attention to the question of what could be usefully made by a lunar fabber. The answer that evolved was:

• Construction elements, such as posts, beams, and bricks, individually designed for mating to neighbors.
• Conduits for plumbing, air management, and space radiators.
• Fixtures and fittings, such as brackets, joints, etc.
• Large vehicle elements, such as frame members and wheels, as well as replacement parts for complex vehicle systems, such as engines and brakes.
• Hand tools, such as mallets and wrenches, as well as parts and fittings for power tools, including bases for heavy machinery.
• Structural and functional elements of technology projects, such as solar power collectors, telescopes, transmitters, etc.

     Everyone in the RP industry has seen components like these made out of plastic by today’s Sinterstations and FDMs. And we’ve seen the Sinterstation and other systems make primitive objects directly out of metals. Is it therefore difficult to foresee fabbers, with some more work and development, making such components as these directly in metals derived from lunar raw materials?

     The other articles in the New Millennium series are:

• Professional Fabbing at Home
• UPS Foretells the Fabber Revolution

     If you found this interesting, you’ll also want to read:

• Using Fabricators to Reduce Space Transportation Costs, explains how fabbers are the critical element that will finally make space habitation feasible for the first time in history.