page_title: Reentry capsule
section_title: Structure
hierarchical_section_title: Reentry capsule / Structure
caption_attribution_description: English: A North American Rockwell Corporation artist's concept depicting the Apollo Command Module (CM), oriented in a blunt-end-forward attitude, re-entering Earth's atmosphere after returning from a lunar landing mission. Note the change in color caused by the extremely high temperatures encountered upon re-entry.
context_page_description: A reentry capsule is the portion of a space capsule which returns to Earth following a spaceflight. The shape is determined partly by aerodynamics; a capsule is aerodynamically stable falling blunt end first, which allows only the blunt end to require a heat shield for atmospheric entry. Its shape has also been compared to that of an old-fashioned automobile's headlight. A manned capsule contains the spacecraft's instrument panel, limited storage space, and seats for crew members. Because a capsule shape has little aerodynamic lift, the final descent is via parachute, either coming to rest on land, at sea, or by active capture by an aircraft. In contrast, the development of spaceplane reentry vehicles attempts to provide a more flexible reentry profile.
context_section_description: Reentry capsules have typically been smaller than 5 meters (16 feet) in diameter due to launch vehicle aerodynamic requirements. The capsule design is both volumetrically efficient and structurally strong, so it is typically possible to construct small capsules of performance comparable to lifting body or spaceplane designs in all but lift-to-drag ratio for less cost. The Soyuz spacecraft is an example. Most capsules have used an ablative heat shield for reentry and been non-reusable. The Orion Multi-Purpose Crew Vehicle appears likely, as of December 2005, to use a ten-times reusable capsule with a replaceable heat shield. There is no limit, save for lack of engineering experience, on using high-temperature ceramic tiles or ultra-high temperature ceramic sheets on reentry capsules.
  Materials for the capsule are designed in different ways, like the Apollo command module’s aluminum honeycomb structure. Aluminum is very light, and the structure gives the capsule extra strength. The early spacecraft had a coating of glass embedded with synthetic resin and put in very high temperatures. Carbon fiber, reinforced plastics and ceramic are new materials that are constantly being made better for use in space exploration.
caption: Artwork of Apollo command module flying with the blunt end of the heat shield at a non-zero angle of attack in order to establish a lifting entry and control the landing site
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