Status and Issues Related to In-Space Propulsion Systems

In-space propulsion is required for multiple, critical, postlaunch functions for most space missions. The propulsion functions are broadly classiŽ ed as insertion, on-orbit (including stationkeeping, repositioning, constellation management, etc.), and disposal/deorbit (if required). Orbit transfer represents a major additional element of in-space propulsion but only the onboard segment of in-space propulsion is treated herein. It is estimated that the mass of in-space propulsion will represent over 40% of the mass delivered by launchers and upper stages for all unmanned space missions over the next 10 years and, therefore, will exert a predominant in uence on the capability and competitiveness of future space systems. Technical advancements of in-space propulsion are underway and include demonstrations of higher-performance (speciŽ c impulse) chemical and electric rocket systems. This paper will brie y 1) review the stateof-the-art in-space propulsion, 2) discuss some new technologies in advanced development, and 3) present the impact of selected advanced technologies on space missions.