Science Fair Project Encyclopedia
A clanking replicator is an artificial self-replicating system that relies on conventional large-scale technology and automation. The term evolved to distinguish such systems from the microscopic "assemblers" that nanotechnology may make possible. They are also sometimes called "Auxons", from the Greek word auxein which means "to grow", or "von Neumann machines" after John von Neumann, who first rigorously studied the idea. This last term ("von Neumann machine") is less specific and also refers to a completely unrelated computer architecture proposed by von Neumann, so its use is discouraged where accuracy is important. Von Neumann himself used the term "Universal Constructor".
Such a machine violates no physical laws, and we already possess the basic technologies necessary for some of the more detailed proposed designs.
A self-replicating machine would need to have the capacity to gather energy and raw materials, process the raw materials into finished components, and then assemble them into a copy of itself. It is unlikely that this would all be contained within a single monolithic structure, but would rather be a group of cooperating machines or an automated factory that is capable of manufacturing all of the machines that make it up. The factory could produce mining robots to collect raw materials, construction robots to put new machines together, and repair robots to maintain itself against wear and tear, all without human intervention or direction. The advantage of such a system lies in its ability to expand its own capacity rapidly and without additional human effort; in essence, the initial investment required to construct the first clanking replicator would have an arbitrarily large payoff with no additional cost.
History of the concept
The idea of non-biological self-replicating systems was first seriously suggested by mathematician John von Neumann in the late 1940s when he proposed a kinematic self-reproducing automaton model as a thought experiment. See von Neumann, J., 1966, The Theory of Self-reproducing Automata, A. Burks, ed., Univ. of Illinois Press, Urbana, IL.
Advanced Automation for Space Missions
In 1980, NASA conducted a summer study entitled Advanced Automation for Space Missions, edited by Robert Freitas, to produce a detailed proposal for self-replicating factories to develop lunar resources without requiring additional launches or human workers on-site. The proposed system would have been capable of exponentially increasing productive capacity. The design could be modified to build Von Neumann probes to explore the galaxy.
The reference design specified small computer-controlled electric carts running on rails. Each cart could have a simple hand or a small bull-dozer shovel, forming a basic robot.
Power would be provided by a "canopy" of solar cells supported on pillars. The other machinery could run under the canopy.
A "casting robot" would use a robotic arm with a few sculpting tools to make plaster molds. Plaster molds are easy to make, and can make precise parts with good surface finishes. The robot would then cast most of the parts either from nonconductive molten rock (basalt) or purified metals. An electric oven would melt the materials. A carbon dioxide laser cutting and welding system was also included.
A more speculative, more complex "chip factory" was specified to produce the computer and electronic systems, but the designers also said that it might prove practical to ship the chips from Earth as if they were "vitamins."
Much of the design study was concerned with a simple, flexible chemical system for processing the ores, and the differences between the ratio of elements needed by the replicator, and the ratios available in lunar regolith. The element that most limited the growth rate was chlorine, needed to process regolith for aluminium. Chlorine is very rare in lunar regolith, so the design recycled it.
- Freeman Dyson expanded upon Neumann's automata theories, and advanced a biotechnology-inspired theory. See Astrochicken.
- The first technical design study of a self-replicating interstellar probe was published in a 1980 paper by Robert Freitas
- Clanking replicators are also mentioned briefly in the fourth chapter of K. Eric Drexler's 1986 book Engines of Creation.
- Article about a proposed clanking replicator system to be used for developing Earthly deserts in the October 1995 Discover Magazine, featuring forests of solar panels that powered desalination equipment to irrigate the land.
- In 1998, Chris Phoenix suggested a general idea for a macroscale replicator on the sci.nanotech newsgroup, operating in a pool of ultraviolet-cured liquid plastic, selectively solidifying the plastic to form solid parts. Computation could be done by fluidic logic. Power for the process could be supplied by a pressurized source of the liquid.
- In 2004, General Dynamics completed a study for NASA's Institute for Advanced Concepts. It concluded that complexity of the development was equal to that of a Pentium 4, and promoted a design based on cellular automata.
- In 2004, Robert Freitas and Ralph Merkle published the first comprehensive review of the field of self-replication, in their book Kinematic Self-Replicating Machines, which includes 3000+ literature references.
- In 2005, Adrian Bowyer of the University of Bath started a project to develop a rapid prototyping machine which would be able to replicate itself, making such machines cheap enough for people to buy and use in their homes. The project is releasing material under the GNU GPL. 
Clanking replicators in fiction
An early treatment was the short story Autofac by Philip K. Dick, published in 1955, which precedes von Neumann's original paper about self-reproducing machines. Dick also touched on this theme in his earlier 1953 short story Second Variety. Another example can be found in the 1962 short story Epilogue by Poul Anderson, in which self-replicating factory barges were proposed that used minerals extracted from ocean water as raw materials.
In his short story "Crabs on the Island" (1958) Anatoli Dneprov speculated on the idea that since the replication process is never 100% accurate, leading to slight differences in the descendants, over several generations of replication the machines would be subjected to evolution similar to that of living organisms. In the story, a machine is designed, the sole purpose of which is to find metal to produce copies of itself, intended to be used as a weapon against an enemy's war machines. The machines are released on a deserted island, the idea being that once the available metal is all used and they start fighting each other, natural selection will enhance their design. Stanislaw Lem has also studied the same idea in his novel The Invincible (1964), in which the crew of a spacecraft landing on a distant planet finds non-biological life-form, which is the product of long, possibly of millions of years of mechanical evolution.
NASA's Advanced Automation for Space Missions study directly inspired the science fiction novel Code of the Lifemaker (ISBN 0-345-30549-3) by author James P. Hogan. More modern references to this idea can also be seen in the TV show Stargate SG-1 with the race called Replicators, in which self-replication is achieved and enhanced through absorption of raw materials and technology; this however follows the Grey goo scenario.
Other notable works containing clanking replicators
- Autofac by Philip K. Dick
- Berserkers, a series of books and short stories by Fred Saberhagen
- The Forge of God by Greg Bear
- 2010: Odyssey Two by Arthur C. Clarke
- Deus Ex by Ion Storm
- The World at the End of Time by Frederik Pohl
Prospects for implementation
As the use of industrial automation has expanded over time, some factories have begun to approach a semblance of self-sufficiency that is suggestive of clanking replicators. However, it is unlikely that such factories will achieve "full closure" in the near future so long as human labour and external supplies of spare parts remain conveniently available to them; there simply isn't sufficient economic value to be gained in overcoming the remaining dependencies. Fully-capable machine replicators are most useful for developing resources in dangerous environments which are not easily reached by existing transportation systems.
A clanking replicator can be considered to be a form of artificial life. Depending on its design, it might be subject to evolution over long time periods. However, with robust error correction, and the possibility of external intervention, the common science fiction theme of robotic life run amok is unlikely in the near term.
It should probably be noted that clanking is an example of onomatopoeia, understandable to some English speakers, but not to all. The term is meant to evoke the image of a nineteenth century factory, powered by steam, pushing gears and rods, noisy and clamorous.
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