Solar Thermal Technologies for Orbit Transfer Vehicles and Space Mobility

Physical Sciences Inc. proposes to develop an innovative solar thermal propulsion system for application to orbit change and mobility for small spacecrafts. In the proposed system solar radiation is collected by the concentrator which transfers theconcentrated solar radiation to the optical waveguide transmission line consisting of low-loss optical fibers. The optical waveguide cable transmits the high intensity solar radiation to the thermal receiver for efficient, high performance thrustgeneration. Part of the solar radiation can be switched to attitude control thruster as necessary.The features of the proposed system are: 1) highly concentrated solar radiation can be transmitted via flexible optical waveguide transmission line to the thruster's absorber cavity; 2) the flexible optical waveguide linkage de-couples the thruster fromthe concentrator to provide freedom from the constraints of previous solar propulsion system designs; 3) the configuration of the solar receiver can be optimized for efficient heat transfer with minimal re-radiation loss; 4) aiming and tracking for theconcentrator become significantly easier by moving the termination of the optical fiber cable to follow the focal point of the concentrator; and 5) high intensity solar radiation can be switched to different receivers to deploy several thermal thrustersas necessary. The product of the proposed research is a unique propulsion system for small spacecrafts. The proposed solar propulsion system will provide the specific impulse, Isp, and thrust levels between the chemical and ion thrusters. When developed to technicalmaturity, the solar thermal propulsion system will fill the need (Isp = 300-800 seconds; Thrust = 0.1-1N) for orbit change, mobility and attitude control for spacecrafts. Its high solar utilization efficiency (about ten times more efficient than that forelectric propulsion systems) will make the proposed system highly competitive against the electrothermal thrusters such as arcjet and resistojet.