Returning an Entire Near-Earth Asteroid in Support of Human Exploration Beyond Low-Earth Orbit

Abstract

This paper describes the results of a study into the feasibility of identifying, robotically capturing, and returning an entire
\nNear-Earth Asteroid (NEA) to the vicinity of the Earth by the middle of the next decade. The feasibility of such an asteroid
\nretrieval mission hinges on finding an overlap between the smallest NEAs that could be reasonably discovered and
\ncharacterized and the largest NEAs that could be captured and transported in a reasonable flight time. This overlap appears to
\nbe centered on NEAs roughly 7 m in diameter corresponding to masses in the range of 250,000 kg to 1,000,000 kg. The study
\nconcluded that it would be possible to return a ~500,000-kg NEA to high lunar orbit by around 2025. The feasibility is
\nenabled by three key developments: the ability to discover and characterize an adequate number of sufficiently small nearEarth
\nasteroids for capture and return; the ability to implement sufficiently powerful solar electric propulsion systems to
\nenable transportation of the captured NEA; and the proposed human presence in cislunar space in the 2020s enabling
\nexploration and exploitation of the returned NEA. Placing a 500-t asteroid in high lunar orbit would provide a unique,
\nmeaningful, and affordable destination for astronaut crews in the next decade. This disruptive capability would have a
\npositive impact on a wide range of the nation’s human space exploration interests. It would provide a high-value target in
\ncislunar space that would require a human presence to take full advantage of this new resource. It would offer an affordable
\npath to providing operational experience with astronauts working around and with a NEA that could feed forward to much
\nlonger duration human missions to larger NEAs in deep space. It represents a new synergy between robotic and human
\nmissions in which robotic spacecraft would retrieve significant quantities of valuable resources for exploitation by astronaut
\ncrews to enable human exploration farther out into the solar system. The capture, transportation, examination, and dissection
\nof an entire NEA would provide valuable information for planetary defense activities that may someday have to deflect a
\nmuch larger near-Earth object. Transportation of the NEA to lunar orbit with a total flight time of 6 to 10 years would be
\nenabled by a ~40-kW solar electric propulsion system with a specific impulse of 3,000 s. The flight system could be launched
\nto low-Earth orbit (LEO) on a single Atlas V-class launch vehicle, and return to lunar orbit a NEA with at least 28 times the
\nmass launched to LEO. Longer flight times, higher power SEP systems, or a target asteroid in a particularly favorable orbit
\ncould increase the mass amplification factor from 28-to-1 to 70-to-1 or greater. The NASA GRC COMPASS team estimated
\nthe full life-cycle cost of an asteroid capture and return mission at ~$2.6B.