NOVELTY - A space solar power system comprises transmitter (160), concentrator, and radiant energy receiver. The radiant energy receiver includes microchannel heat exchanger. A powerbeam (120) is directed from transmitter to concentrator. The concentrator intensifies and directs powerbeam to radiant energy receiver. The radiant energy receiver converts powerbeam into heat and an increase in the energy content of a fluid.    USE - Space solar power system for thermochemical processing electrical production.    ADVANTAGE - The system provides solar or other radiant energy to remotely located receiver systems. The system can compensate for the shortcomings of the prior art, and thus effectively make use of solar energy for production of high energy density chemical fuels and other chemicals.    DETAILED DESCRIPTION - The space solar power system can also include powersat (100) producing a powerbeam, two surface structures on a lunar or planetary surface (140), receivers for the production of electricity, and unit to adjust powerbeam to vary the surface flux at surface structures and second surface structures. The concentrator includes two segments. The second segment has an average pore size of greater than or equal to 5 mm. The microchannel heat exchanger includes a catalyst for an endothermic reaction. The powerbeam is in a form of laser energy, microwaves, or millimeter waves. The transmitter is part of a system located at a powersat or on a lunar or planetary surface. The receivers include nested cylinders incorporating manifolds, heat exchange zones, and reaction zones. INDEPENDENT CLAIMS are included for:    (1) operating a space solar power system; and    (2) operating a radiant energy concentrator.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of the powersat directing powerbeam to receiver at the surface of lunar or planetary body.    Powersat (100)    Solar energy (110)    Powerbeam (120)    Ground receiving facility (130)    Lunar or planetary surface (140)    Photovoltaic cell arrays (150)    Transmitter (160)