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.
3.14 Freitas Atomic Separator Replicator (1981)
Following in the tradition of Shoulders (Section 4.7) and Taylor (Section 3.10), in 1981 Freitas  privately circulated an unpublished basic technical analysis of the potential problems and performance characteristics of a space-based solar-powered “atomic separator” replicator using a fully-dissociated materials input beam, laser separation of isotopes, and raster-scan production of parts. This analysis was intended as a simple scaling study, not as a full systems design.
In this scenario, raw lunar or asteroidal material is delivered to a parabolic solar furnace where it is heated to ~5000 K at the focus, irradiated by a pulsed-mode laser and electron gun raising the vapor temperature to ~6 eV, collimated and accelerated through metal plates, then passed through bending magnets which remove ionized species for recycling, leaving a collimated hot neutral atomic beam. This beam enters a linear laser isotope separation  chamber in which a series of magnets and tunable excitation lasers allow atoms of selected pure elements to be picked out of the beam and diverted to collectors, with a beam dump at the far end that collects unused material for reuse or disposal. Collected atoms, thus sorted, can then be employed in a beam-deposition scheme in which pure elemental feedstock is ionized and electrostatically delivered to a workpiece, building up parts and larger systems by a raster-scan type deposition process similar to processes which in later years have become known as stereolithography [1110-1119], fused deposition modeling (FDM) [933-935], electrodeposition microfabrication (EFABTM) [1122-1124], gas phase solid freeform fabrication (SFF) [1125-1127], and so forth, as briefly reviewed in Section 3.20.
The main device (Figure 3.50) is a cylinder averaging ~5 meters wide and ~20 meters long, not counting 1100 m2 of waste heat radiators and 76,400 m2 of solar power panels producing 11 MW of power. The estimated net mass throughput of atomically sorted atoms is ~0.00125 kg/sec. Assuming mean system density is ~100 kg/m3 (it is mostly vacuum) and the panels and radiators are 1 cm thick in the complete system deployed in lunar orbit (Figure 3.51), then the atomic separator replicator has a mass of ~120 tons and a net production rate of ~40 tons/year, hence can process its own mass of materials in ~108 sec, a ~3 year replication time.
Last updated on 1 August 2005