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NASA has sought to utilize high-power solar electric propulsion as means of improving the affordability of in-space transportation for almost 50 years. Early efforts focused on 25 to 50 kilowatt systems that could be used with the Space Shuttle, while later efforts focused on systems nearly an order of magnitude higher power that could be used with heavy lift launch vehicles. These efforts never left the concept development phase in part because the technology required was not sufficiently mature. Since 2012 the NASA Space Technology Mission Directorate has had a coordinated plan to mature the requisite solar array and electric propulsion technology needed to implement a 30 to 50 kilowatt solar electric propulsion technology demonstration mission. Multiple solar electric propulsion technology demonstration mission concepts have been developed based on these maturing technologies with recent efforts focusing on an Asteroid Redirect Robotic Mission. If implemented, the Asteroid Redirect Vehicle will form the basis for a capability that can be cost-effectively evolved over time to provide solar electric propulsion transportation for a range of follow-on mission applications at power levels in excess of 100 kilowatts.

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Multiple Solar Electric Propulsion Technology Demonstration Mission were developed to assess vehicle performance and estimated mission cost. Concepts ranged from a 10,000 kg spacecraft capable of delivering 4000 kg of payload to one of the Earth Moon Lagrange points in support of future human-crewed outposts to a 180 kg spacecraft capable of performing an asteroid rendezvous mission after launched to a geostationary transfer orbit as a secondary payload. Low-cost and maximum Delta-V capability variants of a spacecraft concept based on utilizing a secondary payload adapter as the primary bus structure were developed as were concepts designed to be co-manifested with another spacecraft on a single launch vehicle. Each of the Solar Electric Propulsion Technology Demonstration Mission concepts developed included an estimated spacecraft cost. These data suggest estimated spacecraft costs of $200M -$300M if 30 kW-class solar arrays and the corresponding electric propulsion system currently under development are used as the basis for sizing the mission concept regardless of launch vehicle costs. The most affordable mission concept developed based on subscale variants of the advanced solar arrays and electric propulsion technology currently under development by the NASA Space Technology Mission Directorate has an estimated cost of $50M and could provide a Delta-V capability comparable to much larger spacecraft concepts.Nomenclature ACS = Attitude Control System ARRM = Asteroid Redirection Robotic Mission ATK = Alliant Techsystems Inc. AU = Astronomical Unit BOL = Beginning of Life DDU = Direct Drive Unit DSS = Deployable Space Systems EELV = Evolved Expendable Launch Vehicle EM-L2 = Earth Moon Lagrange point two EOL = End of Life EP = Electric Propulsion EPS = Electric Power System 2 Isp = Specific Impulse L2 = semi-stable second Lagrange Point LEO = Low Earth Orbit LGA = Lunar Gravity Assist LLO = Low Lunar Orbit MEL = Master Equipment List MGA = Mass Growth Allowance MLI = Multi-Layer Insulation NEA = Near Earth Asteroid NEAR = Near Earth Asteroid Rendezvous NEXT = NASA Evolutionary Xenon Thruster PPU = Power Processing Unit RCS = Reaction Control System ROSA = Roll Out Solar Array SADA = Solar Array Drive Assembly SAS = Solar Array System SEP = Solar Electric Propulsion SIP = Spiral In Phase SOP = Spiral Out Phase SMA = semi-major Axis STMD = Space Technology Mission Directorate TDM = Technology Demonstration Mission Xe = Xenon µSEPSAT = micro solar electric propulsion satellite ΔV = Delta V (change in velocity)

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