Hypersonic glide vehicle

Boost-glide trajectories are a class of spacecraft guidance and reentry trajectories that extend the range of suborbital spaceplanes and reentry vehicles 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 first seriously studied as a way to extend the range of ballistic missiles, but has not been used operationally in this form. The underlying aerodynamic 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.

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 275 kilometres (171 mi) to about 550 kilometres (340 mi). 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 during the next few years. Low-level research continued until 1942 when it was cancelled.

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