Reaching the Outer Planets with Nuclear Electric Propulsion: Trades, Sensitivities and the Case for a Neptune System Explorer

Abstract. Over the last year, a large effort that involved several NASA agencies and DOE was initiated to evaluate the mission benefits and understand the sensitivities of Nuclear Electric Propulsion (NEP). This paper first describes the sensitivities of the mission design parameter space (i.e. the trades between propulsion system characteristics, power level, system efficiencies, and flight times). It also illustrates the findings for a conceptual Neptune System Explorer mission. A point design for this mission is presented, using a 100-kWe Power and Propulsion Module (designed in parallel by a NASA MSFC led effort) along with a representative science payload. This mission features a fly-by of Nereid, a capture and IO-month stay around Triton, a transfer to an elliptical polar orbit around Neptune and science in this orbit for 12 months. The system features a very high downlink data rate from Neptune (several 1 Os of Mbps), and a comprehensive suite of science instruments. Variations in power levels around the design point are investigated. This analysis shows where technology development should be directed to fully take advantage of the NEP capabilities