The U.S. program for human spaceflight is now roughly following the flexible path defined by the Obama Administration's "Review of U.S. Human Space Flight Plans Committee": a step-by-step approach of human missions going beyond the Moon with intermediate waypoints such as Lagrange Points, Near-Earth Asteroids, and Phobos and Deimos, prior to a Mars landing. The President also set a goal for NASA to send astronauts to a Near-Earth Asteroid (NEA) by 2025. Piloted near-Earth asteroid missions will require 6- to 9-month mission durations, tons of supplies, a deep-space habitat, reliable life support systems, and multiple heavy-lift launches. Projected budgets and development schedules mean that such an expedition is unlikely before 2030. Limiting astronauts to low Earth orbit for another two decades will diminish public interest in human space exploration and perhaps curtail it permanently. An attractive interim solution is a robotic mission, using today's technology, to move a very small asteroid within reach of astronauts. In a preliminary design study, a single Atlas V launch could retrieve a representative NEA, 2008 HU4. There is a high premium on finding suitable candidate asteroids and sufficiently characterizing their physical and orbital properties, enabling development of a practical flight system and mission profile. A carbonaceous asteroid is the most desirable target both for its scientific value and its volatile content, a potential resource. Early search efforts have begun. The preliminary mission design took a dual approach to protecting Earth: a captured asteroid in the right kind of high retrograde lunar orbit, if left untended, will eventually impact the Moon. A small carbonaceous asteroid, with.its low physical strength, would also be destroyed upon atmospheric entry. This paper describes possible astronaut operations and experiments at the NEA, e.g. grappling technologies, sample return, mining experiments, water and metal extraction, and other uses of space resources. The proposed asteroid retrieval and its subsequent human exploration will advance deep space exploration and boosts the potential commercial use of in-situ resources.
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