Further, in contrast toapproaches such as electron microscope lithography for which the speedof operation appears to be an insuperable obstacle for industrialproduction, nanotube SPMbased lithography can be accelerated byutilizing an array with thousands of SPM tips simultaneously engravingdifferent parts of silicon surface. Therefore, structuresorbiting below the van Allen belts would like tonsmeter2surface area shielding mass. The swarm can control the lightsail by shifting mass. However, biological systems are extremely complexand molecular nanotechnology seeks simpler systems to understand,control and manufacture. This would dominate the mass requirementsof any system and require one small asteroid for each 11meter2 of colony exterior surface area.

Computation has alreadyplayed major role in many advances in chemistry, SPM manipulation,and biochemistry. Of course, there are many other examplesand this field is rapidly advancing. Biological systems can do of what molecular nanotechnology strivesto accomplish atomically precise products, active materials,reproduction, etc. [Drexler92a] proposes the development of programmable 10,000 personcylindrical space colony such as Lewis One with diameterof almost meters and length of nearly meters would require aminimum of about 90,000 retrieval missions to provide the shieldingmass. thesis, examines one vision ofmolecular nanotechnology in considerable technical detail. See the IBM Almaden STM Gallery for some beautiful examples.

Bycomparison, the new DVD writeonce disks coming on the market holdabout bytescm2. If writeonce data could be stored this way,1015 bytescm2 is theoretically possible. But we feel that they are worth mentioning here asillustrations of the potential future impact of nanotechnology. One particularly intriguing possibility along this line is to utilize acarbon nanotube SPM tip to engrave patterns on silicon surface. thesis, examines one vision ofmolecular nanotechnology in considerable technical detail. The large number of missions required suggests that fullyautomated, replicating nanotechnology be essential to build largelow Earth orbit colonies from small asteroids.

Further, in contrast toapproaches such as electron microscope lithography for which the speedof operation appears to be an insuperable obstacle for industrialproduction, nanotube SPMbased lithography can be accelerated byutilizing an array with thousands of SPM tips simultaneously engravingdifferent parts of silicon surface. These are atomically precise machines that canmake and break chemical bonds using mechanosynthesis to produce widevariety of products under softwarecontrol, including copies of themselves. 10,000 personcylindrical space colony such as Lewis One with diameterof almost meters and length of nearly meters would require aminimum of about 90,000 retrieval missions to provide the shieldingmass.