Editing Self-replication (section)

===Space exploration and manufacturing===
The goal of self-replication in space systems is to exploit large amounts of matter with a low launch mass.  For example, an [[autotroph]]ic self-replicating machine could cover a moon or planet with solar cells, and beam the power to the Earth using microwaves.  Once in place, the same machinery that built itself could also produce raw materials or manufactured objects, including transportation systems to ship the products. [[Von Neumann Probe|Another model]] of self-replicating machine would copy itself through the galaxy and universe, sending information back.

In general, since these systems are autotrophic, they are the most difficult and complex known replicators.  They are also thought to be the most hazardous, because they do not require any inputs from human beings in order to reproduce.

A classic theoretical study of replicators in space is the 1980 [[NASA]] study of autotrophic clanking replicators, edited by [[Robert Freitas]].<ref>[[Wikisource:Advanced Automation for Space Missions]]</ref>

Much of the design study was concerned with a simple, flexible chemical system for processing lunar [[regolith]], and the differences between the ratio of elements needed by the replicator, and the ratios available in regolith.  The limiting element was [[Chlorine]], an essential element to process regolith for [[Aluminium]].  Chlorine is very rare in lunar regolith, and a substantially faster rate of reproduction could be assured by importing modest amounts.

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 cell]]s 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]] [[molding (process)|mold]]s.  Plaster molds are easy to make, and make precise parts with good surface finishes.  The robot would then cast most of the parts either from non-conductive molten rock ([[basalt]]) or purified metals.  An [[electricity|electric]] [[oven]] melted the materials.

A 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".