A Solar Path to Europa: How Solar Electric Propulsion Can Enable Missions to the Outer Solar System

Abstract

The use of Solar Electric Propulsion (SEP) is evaluated in the context of a mission to Europa. It is shown that smaller missions making use of SEP can deliver a larger payload on a smaller launch vehicle than is possible with an all -ch emical mission. Large missions (over ~3700 kg) are possible on existing launch vehicles only with SEP systems. The cruise times for SEP missions are generally longer than for all -chemical missions, but depend on launch date. In examining missions to Europa , future planners would be well advised to include SEP in their trade studies. I. Introduction upiter’s moon Europa is one of the most important places in the solar system for future scientific study. Recent evidence 1-4 suggests that Europa may have beneat h its icy surface an ocean of liquid salt water that could potentially support a biosphere. The confirmation of the existence of such a subsurface ocean, and the detection of signs of life on Europa, are two of the most compelling science objectives in pla netary science. Europa has been designated as the most important destination in the outer planets by the NRC Decadal Survey for planetary science 5 . In this work, we examine mission ideas for the future exploration of Europa, and suggest how such a mission (or set of missions) could be done using proven launch vehicles and existing propulsion and other technologies. In this work, we discuss a number of possible missions to Europa. We start with concepts for small missions which would carry a reasonably limit ed payload and could include a lander. Ideas for the design of these missions are discussed in some detail; mission ideas that use solar electric propulsion (SEP) for part of the cruise to Jupiter are examined, as well as missions that use chemical propuls ion only. The point designs for the smaller missions are then scaled to larger mission ideas, with concomitantly higher payloads and capabilities. We will show that for large missions, only payloads delivered in part by a SEP system can be undertaken with a single launch using existing technology.