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Non-rocket space launch refers to concepts for launch into space where some or all of the needed speed and altitude are provided by something other than expendable rockets.〔George Dvorsky, (How Humanity Will Conquer Space Without Rockets ), io9 Dec. 30, 2014 (accessed Jan 3 2015).〕 A number of alternatives to expendable rockets have been proposed. In some systems such as skyhook, rocket sled launch, rockoon and air launch, a rocket is used to reach orbit, but it is only "part" of the system. Present-day launch costs are very high – $10,000 to $25,000 per kilogram from Earth to low Earth orbit (LEO).〔"SpaceCast 2020" Report to the Chief of Staff of the Air Force, 22 Jun 94.〕 As a result, launch costs are a large percentage of the cost of all space endeavors. If launch costs can be made cheaper the total cost of space missions will be reduced. Fortunately, due to the exponential nature of the rocket equation, providing even a small amount of the velocity to LEO by other means has the potential of greatly reducing the cost of getting to orbit. Getting launch costs down into the hundreds of dollars per kilogram range would make many of the proposed large-scale space projects such as space colonization, space-based solar power〔(A Fresh Look at Space Solar Power: New Architectures, Concepts, and Technologies. John C. Mankins. International Astronautical Federation IAF-97-R.2.03. 12 pages. )〕 and terraforming Mars possible. ==Comparison== (a) References in this column apply to entire row unless specifically replaced. (b) All monetary values in un-inflated dollars based on reference publication date except as noted. (c) CY2008 estimate from description in 1993 reference system. (d) Requires first stage to ~ 5 km/s. (e) Subject to very rapid increase via bootstrapping. (f) Requires Boeing proposed DF-9 vehicle first stage to ~ 4 km/s. (g) Based on Gen-1 reference design, (2010 version ). (h) Jules Verne's novel ''From the Earth to the Moon''. Newton's cannonball in the 1728 book ''A Treatise of the System of the World'' was considered a thought experiment. 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「Non-rocket spacelaunch」の詳細全文を読む スポンサード リンク
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