Electric Propulsion for Solar System Exploration

The use of ion propulsion for deep-space missions will become a reality in 1998 with the  ight of the ion-propelled, New Millennium Deep Space 1 (DS1) spacecraft. The anticipation of this event is stimulating the call for improved ion propulsion technologies, a trend that is expected to continue. This paper describes the evaluation of possible advanced solar electric propulsion technologies and their potential beneŽ ts to projected near-term and midterm solar system exploration missions. The advanced technologies include high-performance derivatives of the DS1 ion propulsion technology, scaled-down DS1 systems, and direct-drive Hall-effect thruster systems. The results of this study indicate that signiŽ cant near-term beneŽ ts can be obtained by the development of improved versions of the DS1 ion propulsion system (IPSs) components. In addition, if the current trend to smaller planetary spacecraft continues, then missions  ying these smaller future spacecraft will beneŽ t substantially from the development of scaled-down IPSs that incorporate advanced technologies in the ion engines and the propellant feed systems. The performance of the direct-drive Hall thruster systems is potentially superior to that of all other midterm options, but this technology has the highest development risk. SigniŽ cantly reduced trip times to small bodies and the outer planets may be possible if technology programs work to retire these risks.