Source: NASA Announcement
NASA issued a Broad Agency Announcement (BAA) seeking proposals for mission concept studies of a solar electric propulsion system demonstration to test and validate key capabilities and technologies for future exploration missions.
Multiple studies have shown the advantages of using solar electric propulsion to efficiently transport heavy payloads from low Earth orbit to higher orbits. This concept enables the delivery of payloads to low Earth orbit via conventional chemical rockets. The use of solar electric propulsion could then spiral payloads out to higher energy orbits, including Lagrange point one, a potential assembly point in space between Earth and the moon. This approach could facilitate missions to near Earth asteroids and other destinations in deep space. (read announcement)