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OCR for page 49
Acronyms, Abbreviations, and Technical Terms ALS ESA EVA g;l-g GNP HEI LEO NASA NASP NRC NSC SEALAR SSF SSME STS aerobraking cross range capability Advanced Launch System European Space Agency extra vehicular activity gravity; equivalent to one times the acceleration of gravity Gross National Product Human Exploration Initiative low Earth orbit National Aeronautics and Space Administra- tion National Aerospace Plane National Research Council National Space Council Sea Launch and Recovery vehicle Space Station Freedom Space Shuttle Main Engine Space Transportation System Use of a planet's upper atmosphere as a brake to slow the entry of a spaceship, rather than braking by propulsive methods. The maneuvering capability of a spacecraft in orbit as well as after reentering the Earth's atmosphere. The shuttle, for example, has rea- sonably good cross range capability, due largely 49

OCR for page 49
50 ACRONYMS, ABBREVL4TIONS, ED TECHNICS TEES to having wings, while the reentry capsules em- ployed in the early US space program had lit- tle maneuverability and were dependent on the trajectory of their orbit. cryogenic fuels Fuels stored at very low temperatures to max- imize the energy density per unit volume of storage capacity. The fuels typically are gases at room temperature, but are stored at temper- atures at which they are liquids. specific impulse The measure of an engine's efficiency; the ratio of pounds of thrust produced per pounds of fuel flowing through the engine each second.