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Boost-glide trajectories are a class of spacecraft guidance and reentry trajectories that extend the range of suborbital spaceplanes by employing aerodynamic lift in the high upper atmosphere. In most examples, boost-glide roughly doubles the range over the purely ballistic trajectory. In others, a series of ''skips'' allows range to be further extended, and leads to the alternate term skip-glide. The concept was introduced as a way to extend the range of ballistic missiles, but has not been used operationally in this form. The concepts have been used to produce maneuverable reentry vehicles, or MARV, to increase the accuracy of some missiles. More recently the traditional form with an extended gliding phase has been considered as a way to reach targets while flying below their radar coverage. ==Early concepts== The conceptual basis for the boost-glide concept was first noticed by German artillery officers, who found that their ''Peenemünder Pfeilgeschosse'' arrow shells travelled much further when fired from higher altitudes. This was not entirely unexpected due to geometry and thinner air, but when these factors were accounted for they still could not explain the much greater ranges being seen. Investigations at Peenemünde led them to discover that the longer trajectories resulted in the shell having an angle of attack that produced aerodynamic lift. At the time this was considered highly undesirable because it made the trajectory very difficult to calculate, but its possible application for extending range was not lost on the observers. In June 1939, Kurt Patt of Klaus Riedel's design office at Peenemünde proposed wings for converting rocket speed and altitude into aerodynamic lift and range. He calculated that this would roughly double range of the A-4 rockets from to about . Early development was considered under the A-9 name, although little work other than wind tunnel studies at the Zeppelin-Staaken company would be carried out for the next few years. Low-level research continued until 1942 when it was cancelled. The earliest known use of the boost-glide concept for truly long-range use dates to the 1941 ''Silbervogel'' proposal by Eugen Sänger for a rocket powered bomber able to attack New York City from bases in Germany and then fly on for landing somewhere in the Pacific Ocean held by the Empire of Japan. The idea would be to use the vehicle's wings to generate lift and pull up into a new ballistic trajectory, exiting the atmosphere again and giving the vehicle time to cool off between the skips. It was later demonstrated that the heating load during the skips was much higher than initially calculated, and would have melted the spacecraft. In 1943 the A-9 work was dusted off again, this time under the name A-4b. It has been suggested this was either because it was now based on an otherwise unmodified A-4, or because the A-4 program had "national priority" by this time, and placing the development under the A-4 name guaranteed funding. A-4b used swept wings in order to extend the range of the V2 enough to allow attacks on UK cities in The Midlands or to reach London from areas deeper within Germany. The A-9 was originally similar, but later featured long ogive delta shaped wings instead of the more conventional swept ones. This design was adapted as a manned upper stage for the A-9/A-10 intercontinental missile, which would glide from a point over the Atlantic with just enough range to bomb New York before the pilot bailed out. 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「Boost-glide」の詳細全文を読む スポンサード リンク
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