LUNAR LANDING AND SAMPLE RETURN FROM NEAR RECTILINEAR HALO ORBIT USING HIGH-POWERED SOLAR ELECTRIC PROPULSION

In December 2017 the current administration made a single sentence change to US Space Policy Directive-1 which has refocused the country's space explorations efforts on a "return of humans to the Moon for long-term exploration and utilization." With this mandate the National Aeronautics and Space Administration has centered its near-term development activities on a lunar orbiting space station known as the "Gateway". This way-station in deep-space will host astronauts and provide a platform for lunar science. The Gateway sits in a special type of Earth-Moon halo orbit known as a Near Rectilinear Halo Orbit (NRHO) with a proximity that allows for tele-robotics with craft on the surface. It is anticipated that after small commercial landers and payloads begin surface exploration in the early 2020's, government funded or developed mid-sized landers (500-1,000 kg payload) will provide sample return capability. After 2024, it is envisioned that even larger landers (5,000-6,000 kg payload) will be deployed to allow for human return to the surface of the Moon after a 50+ year absence. With reuse and affordability being key to enabling any long-term deep-space campaign, Aerojet Rocketdyne (AR) has studied the use of its highly efficient and high powered solar electric propulsion (SEP) technology to deliver payloads to low lunar orbit (LLO) from the Gateway to reduce the size and cost of Lander systems that use traditional chemical propulsion (LOX/H-2, LOX/CH4, or NTO/MMH). AR is currently working with NASA to develop xenon-fueled SEP systems that would be used in the Gateway's Power and Propulsion Element (PPE) to provide power, thrust, and station-keeping. This paper explores using a SEP tug based on AR's Gateway PPE design to deliver a Lander and/or return a science sample from the lunar surface. This derivative PPE could then be refueled at the gateway and reused to support subsequent exploration activities. Trajectory sensitivities and trades with respect to NRHO departure orbits (i.e. 4:1 Earth Sidereal, 9:2 Lunar synodic), PPE power level, lander mass, and Lander propellant choice are presented to provide estimates for two-way payload capability, xenon utilization, and transfer times to the lunar surface and back.