HET systems are well suited for interplanetary transfers, supporting exploration and science missions. Throttling ability is important for a thruster that might be called upon to propel a spacecraft from Earth to Mars, which orbits at 1.52 AU and reduces the solar constant to 43% of the value at Earth. The Outer Planet Assessment Group has called out high power density/high efficiency power electronics as needs for the Titan/Enceladus Flagship and planetary exploration missions. These types of missions, including Mars Sample Return using Hall thrusters and PPUs, require advancements in power electronics to improve efficiency, reduce mass and volume, and to develop systems beyond the state-of-the-art. A HET system that provides efficient and affordable transportation to, from and around space destinations is one of NASA Grand Challenges. NASA has identified 30kW-class SEP systems as a high-value intermediate step toward higher power systems due to broad cross-cutting capability. The proposed modular discharger is easily scalable, providing NASA with greater mission flexibility over any target SEP power level.
Electric propulsion systems have been identified as a key technology for transportation of DoD space assets. The AFRL IHPRPT Program continues to invest in the development of HET systems. Hall Effect thruster propulsion systems can serve DoD space needs by the in-space transportation of DoD space assets and commercial communication satellites for both orbit transfer and station keeping. The PPU for such a thruster system could enhance many missions for satellite orbit maintenance, orbit changes, and repositioning. The PPU is also compatible with Hall thruster operating on alternate propellants such as krypton and/or iodine. High power density EP systems are also identified in the IHPRPT RP21 goals for spacecraft propulsion. For commercial applications dominated by communications GEOsats, the proposed universal, rugged converter could significantly reduce the cost of current PPU. Because of its wide input voltage range and IPOS and IPOP operation such converter could capture significant fraction of the commercial market further reducing cost and delivery time. A high power density modular PPU could also find near term application on an all-electric upper stage derived from Busek/ULA ESPA orbit maneuvering system (OMS), a free flying S/C based on the ESPA ring. The low power ESPA system presently utilizes four BHT-1500 Xe Hall effect thrusters and is capable of delivering up to five secondary payloads to diverse earth orbits.