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Also known as nuclear electric propulsion and space nuclear fission electric power systems,〔David Buden (2011), (''Space Nuclear Fission Electric Power Systems: Book 3: Space Nuclear Propulsion and Power'' )〕〔Joseph A. Angelo & David Buden (1985), (''Space Nuclear Power'' )〕〔NASA/JPL/MSFC/UAH 12th Annual Advanced Space Propulsion Workshop (2001), (''The Safe Affordable Fission Engine (SAFE) Test Series'' ))〕〔NASA (2010), ''(Small Fission Power System Feasibility Study Final Report )''〕〔Patrick McClure & David Poston (2013), ''(Design and Testing of Small Nuclear Reactors for Defense and Space Applications )〕〔Mohamed S. El-Genk & Jean-Michel P. Tournier (2011), ''(Uses of Liquid-Metal and Water Heat Pipes in Space Reactor Power Systems )''〕〔U.S. Atomic Energy Commission (1969), ''(SNAP Nuclear Space Reactors )''〕 in a nuclear electric rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies.〔Space.com (May 17, 2013), ''(How Electric Spacecraft Could Fly NASA to Mars )''〕 Technically the powerplant is nuclear, not the propulsion system, but the terminology is standard. A number of heat-to-electricity schemes have been proposed: Rankine cycle, Brayton cycle, Stirling cycle, thermoelectric (including graphene-based thermal power conversion〔Technology Review, March 5, 2012: ''(Graphene Battery Turns Ambient Heat Into Electric Current )''〕〔Scientific Reports, Aug. 22, 2012: ''(Graphene-based photovoltaic cells for near-field thermal energy conversion )''〕〔MIT News, Oct. 7, 2011: ''(Graphene shows unusual thermoelectric response to light )''〕), pyroelectric, thermophotovoltaic, thermionic and magnetohydrodynamic type thermoelectric materials. ==Possible uses== One of the more practical schemes is a variant of a pebble bed reactor. It would use a high mass-flow nitrogen coolant near normal atmospheric pressures. This would take advantage of highly developed conventional gas turbine technologies. The fuel for this reactor would be highly enriched, and encapsulated in low-boron graphite balls probably 5–10 cm in diameter. The graphite serves to slow, or moderate, the neutrons. This style of reactor can be designed to be inherently safe. As it heats, the graphite expands, separating the fuel and reducing the reactor's criticality. This property can simplify the operating controls to a single valve throttling the turbine. When closed, the reactor heats, but produces less power. When open, the reactor cools, but becomes more critical and produces more power. The graphite encapsulation simplifies refueling and waste handling. Graphite is mechanically strong, and resists high temperatures. This reduces the risk of an unplanned release of radioactives. Since this style of reactor produces high power without heavy castings to contain high pressures, it is well suited to power spacecraft. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nuclear electric rocket」の詳細全文を読む スポンサード リンク
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