Applications of Brayton cycle technology to space power

Abstract

The Closed Brayton Cycle (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat sources include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turboalternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration. applications. The CBC consists of a heater, turboalternator compressor (TAC), cooler, and recuperator. A mixture of He and Xe is used as the working fluid in the CBC system. The He provides superior heat transfer characteristics in the heater, cooler, and recuperator. The Xe adjusts the molecular weight to provide superior aerodynamic performance for maximized turbine and compressor efficiency. Cycle studies are performed to select the optimum He/Xe molecular weight or He to Xe mixture ratio. The following presents the characteristics and advantages of using the CBC for space power applications, CBC development status, characteristics and applications of the CBC with each of the heat sources, and finally performance projections. >