NASA is refocusing its Project Prometheus nuclear initiative on meeting the surface-power needs of astronauts sent to the Moon and Mars for extended stays. The shift amounts to a fundamental restructuring of a program initiated in 2002 expressly to develop nuclear power and propulsion systems for unmanned missions to the outer reaches of the solar system. NASA had intended to try out those systems for the first time on a multibillion-dollar orbiter it planned to launch by 2015 for a lengthy tour of Jupiter's icy moons. Under the new plan, development of the nuclear electric propulsion system needed for the Jupiter Icy Moons Orbiter (JIMO) mission becomes NASA's lowest nuclear priority, superseded by surface-power generation and nuclear thermal propulsion.
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