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A Propulsive Fluid Accumulator is an artificial Earth satellite which collects and stores oxygen and other atmospheric gases for in-situ refuelling of high-thrust rockets. This eliminates the need to lift oxidizer to orbit and therefore brings significant cost benefits. A major portion of the total world payload sent into low earth orbit each year is either liquid oxygen or water. == Propulsive Fluid Accumulator (PROFAC)== In the period 1956 to 1963, S.T. Demetriades proposed methods of atmospheric gas accumulation by means of a satellite moving in low Earth orbit, at an altitude of around 120 km, or propellant accumulation by stations on the surface of a planet or by gathering and exploiting interstellar matter 〔JBIS, Vol 17, p114, 1959 - 1960; ARS Preprint 2438-62, Part I, 14-16 Mar 1962; Parts II, III and IV not to be found in the open literature; also National Archives ARC Identifier No. 1250057 and 1250058〕〔1963 McGraw-Hill Yearbook of Science and Technology〕. In its simplest form, Demetriades' proposed satellite extracts air from the fringes of the atmosphere, compresses and cools it, and extracts liquid oxygen. The remaining nitrogen is, in part, used as propellant for a nuclear-powered magnetohydrodynamic electromagnetic plasma thruster, which maintains the orbit at about 120 km, or a solar powered thruster (and collection system) for altitudes above 150 km (as stated in the original 1959 JBIS article, p119) compensating for atmospheric drag.〔 〕 This system was called “PROFAC” (PROpulsive Fluid ACcumulator).〔. Several systems were studied, e. g. PROFAC-S for Surface, PROFAC-C for Orbital, PROFAC-A for combination with aerospaceplane making one reusable stage to orbit possible, etc. Several inlets (e. g. conical as in AIEE 10 Aug 1960 San Diego meeting, or funnel) and cryopumps were studied for orbital air collection. The work slowed down in late 1961 although much progress was made in later years on such items as a solar-powered PROFAC. 〕 There are, however, safety concerns with placing a nuclear reactor in low Earth orbit. 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「Propulsive fluid accumulator」の詳細全文を読む スポンサード リンク
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