will verify the AGT technology developments by conducting 400 hours of testing on the engine at temperatures up to 1644K (2500F). An additional indication of the state of ceramic turbomachinery technology is the availability in production of ceramic turbochargers. At the higher temperatures which are made possible by these new materials, dramatic increases in the performance of the closed Brayton cycle can be realized. For instance, as illustrated in Fig. 13, increasing the turbine inlet temperature (TIT) of a space-station-size CBC system from 1033K (1400F) to 1589K (2400F), while maintaining compressor inlet temperature at 383K (50F), can increase efficiency 10 points, decrease weight by 30%, and decrease radiator area by almost 50%. Studies also indicate that an increase in the TIT of a nuclear-reactor-based, 1 MW CBC system from 1089K (1500F) to 1500K (2240F) can reduce specific mass from 12.5 to 4.5 kg/kW and specific radiator area from 1.3 to 0.3 m2/kW. The future of closed Brayton cycle space power systems is also tied to developments in the field of heat sources such as solar, nuclear reactor, and radioisotope energy sources, which are the primary candidates currently envisioned for use in space power systems. Promising work is underway by NASA in the development of higher performance solar collectors and receivers for the closed Brayton cycle, which will allow the higher temperature capability of CBC systems incorporating advanced materials to be realized. The SP100 nuclear reactor (MOOK) is under development with excellent progress reported. Other liquid metal cooled reactors as well as gas cooled reactors such as the NERVA (Nuclear Engine for Rocket Vehicle Application), particle bed, and cermet types are being investigated for future space power applications. Closed Brayton cycle conversion systems are adaptable to all of these reactor types. The gas cooled reactors are particularly attractive because the working fluid gas, such as helium, can be directly heated in the nuclear core, thus eliminating an intermediate heat exchanger and making it possible to achieve higher temperatures and simpler, lighter systems.
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