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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Boost-glide | 1/3 | https://en.wikipedia.org/wiki/Boost-glide | reference | science, encyclopedia | 2026-05-05T12:33:15.179305+00:00 | kb-cron |
Boost-glide, or skip-glide, is a class of atmospheric entry trajectories that follow a non-ballistic trajectory by employing aerodynamic lift in the high upper atmosphere. The term is mostly used to refer to a number of designs that used lift to extend the range of an otherwise shorter-ranged rocket.
Skip is a flight trajectory where the spacecraft goes in and out the atmosphere. Glide is a flight trajectory where the spacecraft stays in the atmosphere for a sustained flight period of time. In most examples, a skip reentry roughly doubles the range of suborbital spaceplanes and reentry vehicles over the purely ballistic trajectory. In others, a series of skips allows the range to be further extended.
Boost-glide entry was first seriously studied as a way to extend the range of ballistic missiles, but was not used operationally in this form as conventional missiles with extended range were introduced. The underlying aerodynamic concepts have been used to produce maneuverable reentry vehicles (MARV), to increase the accuracy of some missiles like the Pershing II. More recently, the concepts have been used to produce hypersonic glide vehicles (HGV) to avoid interception as in the case of the Avangard. The range-extension is used as a way to allow flights at lower altitudes, helping avoid radar detection for a longer time compared to a higher ballistic path.
The concept has also been used to extend the reentry time for vehicles returning to Earth from the Moon, which would otherwise have to shed a large amount of velocity in a short time and thereby suffer very high heating rates. The Apollo Command Module also used what is essentially a skip re-entry, as did the Soviet Zond and Chinese Chang'e 5-T1.
== History ==
=== Early concepts === The conceptual basis was first noticed by German artillery officers, who found that their Peenemünder Pfeilgeschosse arrow shells traveled 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 in the thinner high-altitude air resulted in the shell having an angle of attack that produced aerodynamic lift at supersonic speeds. 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. The earliest known proposal for the boost-glide concept for truly long-range use dates to the 1941 Silbervogel, a proposal by Eugen Sänger for a rocket powered bomber able to attack New York City from bases in Germany 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 ogival delta shaped wings instead of the more conventional swept ones. This design was adapted as a crewed 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.
=== Post-war development ===