Fall 2006 - Air & Space Power Chronicle - Air Force Link

98 AIR & SPACE POWER JOURNAL FALL 2006design. Original MNT concepts envisionedthe use of free-floating, self-contained microscopicrobots called assemblers, which wouldbe able to self-replicate.Assemblers, much more complex than fabricators,require not only their own molecularfabricator tools, but also the associated control,propulsion, communications, and navigationsystems necessary to coordinate withother assemblers on production tasks. The inherentreplication ability of assemblers alsomakes them a potential danger (see the discussionof gray goo below), and more recentMNT theories focus on the use of fabricatorsas an intrinsically less complex, more efficient,and less dangerous solution. 9 The final key capabilityis convergent assembly, which enablesthe mass of fabricators to build large objectsby first building tiny parts, putting those tinyparts together to build larger parts, and thenrepeating the process until a complete, humanscaleproduct has been constructed. By someestimates, if the size of the parts doubles ateach stage, it will take only 30 such stages togo from parts just a few atoms in size to objectsas big as a meter. 10Thus, the MNT fabrication process will firstrequire the production of at least one fabricator,an environmental system conducive to itsoperation, and a control system. The first fabricatorswill begin to construct copies of themselves,helped along by the externally controlledfeed-and-control systems, exponentiallygrowing their number as necessary. The finalmass of fabricators will then create progressivelymore complex molecular building blocks,ultimately assembling them into the final desiredproduct. In contrast to even today’s microtechnology—which,as advanced and impressiveas it seems, still handles atoms “in unrulyherds” of billions or trillions—molecular fabricatorswill permit (and likely demand) molecularlyprecise engineering, which accountsfor each atom or molecule and places it in aspecific location. 11 Because of this increasedprecision, nano-fabricated materials can bedesigned to be simultaneously stronger, lighter,and more feature dense—that is, capable ofcarrying out multiple functions due to fewer“wasted atoms.” For example, rather than havea steel girder that only provides structural supportin a building, a girder could be createdthat is not only lighter and stronger than itssteel counterpart, but also infused with stresssensors or even computer processing capability.The combination of exponential manufacturingand the more efficient use of a product’sphysical structure will also allow for the rapidcreation of prototypes; follow-on manufacturingcan then begin at any time, as the assemblyprocess is the same as for the prototype. 12Possible applications of MNT are potentiallylimitless. Virtually every aspect of humanlife would be affected: for example, tiny robotscould be sent into the human body to locateand destroy cancerous cells or viruses, or evencorrect failing organs at the cellular level,leading to indefinite extension of the humanlife span. Dangers posed by MNT are alsonearly limitless: cheap, fast mass productionwould enable spasmodic arms races, and improvedsmart materials could make currentweapons systems much more capable—or permitcreation of entirely new classes of weapons.Perhaps the most publicized danger fromMNT is the so-called gray-goo problem, wherebyself-replicating nanomachines essentially overwhelmEarth’s naturally occurring life forms.First postulated by Drexler in his 1986 bookEngines of Creation, the gray-goo scenario describesthe release (either accidental or deliberate)of a resilient, omnivorous, artificial“bacteria” that is able to outcompete all life onEarth and which subsequently “reduce[s] thebiosphere to dust in a matter of days,” leavingbehind only a worldwide mass—or gray goo—of microscopic replicators. 13 Drexler himselfhas since repeatedly asserted that such anevent is extremely unlikely to happen accidentally,particularly with the MNT community’sconceptual shift away from assembler-basedproduction, and would be a tremendously difficultundertaking in any case.Not surprisingly, however, dramatic possibilitieslike this have exerted an overshadowingand somewhat hysterical influence onpublic perception. 14 This “science fiction” perceptionof MNT—plus the lack of a workingmolecular fabricator—has prompted themainstream nanotech community to down-