Solar Electric Propulsion for Discovery-Class Missions

This paper offers a user-centric consolidation and comparison of the full range of government and commercial solar electric propulsion options available in the near term for primary propulsion on deep-space science missions of the class commonly proposed to NASA's Discovery program. Unlike previous papers, this work does not emphasize feasibility from a mission-analysis perspective. Rather, it emphasizes requirements uniquely imposed by competitively reviewed cost-capped mission proposals, for which system-level flight heritage and cost credibility can trump sheer performance and mission capture. It describes criteria that mission architects and review boards can use to select and evaluate electric propulsion systems, provides descriptions of viable government and commercial electric propulsion system options, describes the modifications needed to adapt commercial electric propulsion systems to deep space, and discusses appropriate methods for costing commercial-based electric propulsion systems. It concludes that the solar electric propulsion systems best suited for Discovery missions have a solid system flight heritage that can meet the requirements for deep space with minimal modifications. Commercially developed electric propulsion systems offer significant heritage potential and, in many cases, the required changes for deep-space application introduce comparatively low technical and cost risk.