Compact Low Mass Propulsion for Responsive Space

The Hall thruster propulsion system consists of the thruster/cathode, propellant system and the power electronics. The power processing unit (PPU) represents the largest fraction of the system dry mass. In addition, the delivery time, cost of radiation hard electronics and issues regarding pre-launch fuel storage make it difficult for electric propulsion systems to meet the needs of responsive space missions. In Phase I we addressed the Air Force need for a propulsion system that is both operationally responsive to a launch command and operationally responsive on-orbit. Busek demonstrated the feasibility of a shift from the traditional architecture of electric propulsion systems. The approach leverages our flight qualified low power Hall thruster technology and a simplified power processing architecture using a multi-functional auxiliary power converter. In Phase I we also investigated the technical feasibility of an iodine fueled thruster as a means of reducing the stored propellant tank mass and volume. Iodine is stored at atmospheric pressure in solid form at three times the density of xenon. In Phase II we will conduct a comprehensive electronics design and packaging study and build a proto-flight level PPU. The PPU will be integrated into a flight like system with an exiting thruster and flow control valve. A hot fire system demonstration will be performed. In Phase II we will also conduct additional proof of concept tests using iodine propellant. At the conclusion of the program the integrated system will be delivered to AFRL for extended duration testing. BENEFIT: The AFRL IHPRPT Program is investing in the development of long life low power HET systems. A key technology identified in the Beyond IHPRPT study is an extremely long life, low mass variant of the BHT-200 and BHT-600 HET systems. The multi-functional converter concept is attractive for its reduction in overall propulsion system mass complexity and cost. Hall thrusters have also been identified as a key technology for NASA"s vision of space exploration. NASA missions beyond Earth orbit can be enabled by the wide throttle range and broad Isp-thrust operation of Hall thrusters. A study conducted by the SMD ISPT Project in 2004 confirmed the significant potential of EP for space science missions, including orbiters about Pluto, Neptune, and Uranus; rendezvous/return with Kuiper Belt Objects and primitive bodies in the outer Solar System; and extensive surveys of major asteroid groups. Commercial satellite manufacturers; SS/L, Boeing, Lockheed Martin and Orbital Sciences have all shown a strong interest in low power HET systems for primary propulsion on LEO spacecraft and station keeping on GEOSats.