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Those of us that still remember the shock and exhilaration of Sputnik may find it more astonishing than younger people that there is a serious inquiry underway today to determine the best way to construct buildings for the colonization of the moon and Mars. Rapid prototyping is becoming recognized as one of the few ways of accomplishing that task, and Contour Crafting, under development for several years by Behrokh Khoshnevis' group at the University of Southern California is a leading RP contender. Contour Crafting uses extruded materials to build structures layer-wise under computer control. Basically the system deposits a large bead of building material and shapes the surface using a pair of guided, controllable trowels. It's not unlike fused deposition modeling (FDM), but potentially on a huge scale and using a material mixture that hardens chemically rather than being thermoplastic. The system also has the ability to fill between these extruded walls with a second material such as concrete to provide added strength and speed. Close-up of the guided trowels. The advantages for construction on other planets are fairly obvious: Large construction gangs and heavy materials can't easily be transported into space. The machine replaces their labor and can use local materials. Utility conduits and reinforcement members can automatically be built right into the structure. The drawing above shows an earth-bound building being constructed by a Contour Crafting machine combined with a robotic system to place structural members such as support beams. Walls and other surfaces can be fabricated in a virtually finished state, ready to be painted or otherwise decorated. Of course, the typical RP advantages of geometric freedom and multiple materials are also available, as well. The top row of photos shows the construction of various concrete-filled sections. The bottom row gives an idea of the range of geometries possible. Note especially the vaulted shapes that can become roofs. All photos courtesy Dr. Behrokh Khoshnevis, University of Southern California.   The USC group has built several scaled-down versions of the system over the years. They can produce a wide range of geometries. The group is now working on new systems which will allow them to build full-scale building sections which can be tested and analyzed. This is space technology that has a good chance of trickling down to its roots here on earth long before it's ever used in space. The advantages for construction here on earth are almost the same as for space as itemized above. If substantial automation ever becomes part of the building trades, it may well look like Contour Crafting. For more info contact: Behrokh "Berok" Khoshnevis, Professor D. J. Epstein Department of Industrial & Systems Engineering University of Southern California Los Angeles, CA 90089-0193 213-740-4889 213-740-1120 FX http://www-rcf.usc.edu/~khoshnev Learn more details on the web site. You can also download an animation of a house being built by the Contour Crafting process.