Kinematic Self-Replicating Machines
© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.
Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.
3.13.2 Self-Replicating Lunar Factories
Working from von Neumann’s clue  that “you may break a self-reproductive system into parts whose functioning is necessary for the whole system to be self-reproductive, but which are not themselves self-reproductive,” the RSC Team identified two distinct approaches to machine replication. The first approach may be called the “unit replication” or organismic model, in which the replicator is an independent unit which employs the surrounding substrate to directly produce an identical copy of itself. Both the original and the copy remain fertile and may replicate again, thus exponentiating their numbers. The second approach may be called the “unit growth” or factory model, in which a population of specialist devices, each one individually incapable of self-replication, can collectively fabricate and assemble all necessary components comprising all specialist devices within the system. Hence the factory is capable of expanding its size up to the limits of available resources in an appropriate environment. The factory model is often employed in discussions of “bootstrapping,” which is the creation of more productive capacity, from less, using the original capacity. In early systems, control signals could provided from outside, yielding a purely teleoperated replicator; in more mature systems, control could be increasingly internalized, possibly leading to full control autonomy (Section 5.1.9 (A1)).
Note that either type of machine replicator, in order to be useful, must be capable of manufacturing useful non-self product. The scheduling of lunar factory operational phases (Figure 3.39) was regarded as flexible and subject to optimization for different missions. As Merkle  reiterated more eloquently a decade later: “An important point to notice is that self-replication, while important, is not by itself an objective. A device able to make copies of itself but unable to make anything else would not be very valuable. Von Neumann’s proposals centered around the combination of a Universal Constructor, which could make anything it was directed to make, and a Universal Computer, which could compute anything it was directed to compute. This combination provides immense value, for it can be re-programmed to make any one of a wide range of things. It is this ability to make almost any structure that is desired, and to do so at low cost, which is of value. The ability of the device to make copies of itself is simply a means to achieve low cost, rather than an end in itself.”
Last updated on 1 August 2005