NASA has cost and safety goals of $220/kg to low-earth-orbit and one chance of crew loss in one million manned launch attempts. Published studies favor complex, infant, reusable, air-breathing technologies, assuming that reduced vehicle size results in reduced cost. Rough order of magnitude analysis and historical review do not support this assumption. Low purchase, launch and processing costs and high flight rate are either independent of propulsion mode or better satisfied by rocket propulsion. Nomenclature: ∆V = delta velocity g = standard acceleration of gravity GEO = Geosynchronous earth orbit HL = Horizontal Landing HTO = Horizontal Take-off I sp = Specific Impulse (seconds) kg = kilogram kJ = kilojoule kW-hr = kilowatt-hour km = kilometer lb = pound LEO = Low Earth Orbit m f = Final mass of an aerospace vehicle m 0 = Initial mass of an aerospace vehicle mph = miles per hour NASA = National Aeronautics and Space Administration nmi = Nautical mile psf = lbf per square foot q = dynamic pressure (kPa or psf) ROM = Rough Order of Magnitude RLV = Reusable launch Vehicle SSTO = Single Stage to Orbit TRL = Technology Readiness Level VL = Vertical Landing VTO = Vertical Take-Off
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