Propulsion Technologies for Microsatellite Missions

摘要

Many near, to mid-term satellite missions have been identified for 200 kg class spacecraft. For many of these applications, significant delta-v capability is desired in order to perform orbit transfer, on-orbit repositioning and formation flying. Several of these systems are in advanced engineering development and could be ready to support flight opportunities as early as summer 2004. A 200 W Hall Effect Thruster (RET) system is being developed to satisfy traditional high specific impulse (Isp) missions such as stationkeeping and orbit transfer, and has demonstrated Isp of 1,370 sec, thrust of 12.2 mN and 35% total efficiency. This system, however, has also demonstrated the ability to produce very small impulse bits, as low as 1.5 mN-sec, for formations flying applications that require precise maneuvers. To complement this system, a suite of miniaturized sensors is also in development that will enable a full description of the integration impacts of METs on Department of Defense (DoD), National Aeronautic and Space Administration (NASA), and commercial satellites. This instrumentation package consists of a xenon ion energy analyzer, electron (Langmuir) probes, radiometric and photometric sensors, and a solar array experiment. The combined package, including the instruments, electronics, harness, chassis, etc., is less than 2 kg total mass - representing a significant improvement in capability vs. mass and cost. The third system in advanced development is a micro pulsed plasma thruster (MPPT) for applications in propulsive attitude control, which can reduce a l50-kg class microsatellite's attitude control system mass by 90%. This thruster, based on traditional pulsed plasma thrusters, weighs approximately 1.5 kg, and has three orthogonal thrust axes, each of which can be fired to produce impulse about any spacecraft axis. MPPT performance is now being optimized, but is expected to be from 25-100 microN, with an estimated Isp of 500-800 sec.