SOLAR THERMAL THRUSTER MADE OF SINGLE-CRYSTAL MOLYBDENUM

The heart element of solar thermal propulsion (STP) system is a thrust er made of refractory metals such as tungsten, tantalum and molybdenum or advance high temperature ceramics because of the high operating te mperature (1000-2500 K) involved. In this paper, design, fabrication a nd preliminary experimental results in the JSUS Research Plan are pres ented, using 20 mm diameter of thrusters made of single crystal molybd enum which NRIM has patented and is a perfect (non-defect) material, n amely no brittleness due to recrystallization under high operating tem perature conditions. The working gas temperature within the thruster c hamber reached higher than 1850 K (namely, the Isp is approximately 70 0 s for hydrogen gas propellant) at 0.2 MPa of the plenum chamber pres sure, using the small solar concentrator (1.6 m diameter of half parab oloid and 0.65 m of the focal length). (C) 1998 Elsevier Science Ltd. All rights reserved.