page_title: Soyuz (spacecraft)
section_title: Descent module
hierarchical_section_title: Soyuz (spacecraft) / Design / Descent module
caption_attribution_description: This graphic highlights the Soyuz spacecraft's Descent Module.
context_page_description: Soyuz is a series of spacecraft designed for the Soviet space program by the Korolev Design Bureau in the 1960s that remains in service today, having made more than 140 flights. The Soyuz succeeded the Voskhod spacecraft and was originally built as part of the Soviet crewed lunar programs. The Soyuz spacecraft is launched on a Soyuz rocket, the most reliable launch vehicle in the world to date. The Soyuz rocket design is based on the Vostok launcher, which in turn was based on the 8K74 or R-7A Semyorka, a Soviet intercontinental ballistic missile. All Soyuz spacecraft are launched from the Baikonur Cosmodrome in Kazakhstan. After the retirement of the Space Shuttle in 2011, the Soyuz served as the only means for Americans to make crewed space flights until the first flight of VSS Unity in 2018, and the only means for Americans to reach the International Space Station until the first flight of Dragon 2 Crew variant on May 30, 2020. The Soyuz is heavily used in the ISS program.
context_section_description: The descent module (Russian: Спуска́емый Аппара́т, tr. Spuskáyemy Apparát), also known as a reentry capsule, is used for launch and the journey back to Earth. Half of the descent module is covered by a heat-resistant covering to protect it during reentry; this half faces forward during reentry. It is slowed initially by the atmosphere, then by a braking parachute, followed by the main parachute which slows the craft for landing. At one meter above the ground, solid-fuel braking engines mounted behind the heat shield are fired to give a soft landing. One of the design requirements for the descent module was for it to have the highest possible volumetric efficiency (internal volume divided by hull area). The best shape for this is a sphere – as the pioneering Vostok spacecraft's descent module used – but such a shape can provide no lift, which results in a purely ballistic reentry. Ballistic reentries are hard on the occupants due to high deceleration and cannot be steered beyond their initial deorbit burn. That is why it was decided to go with the "headlight" shape that the Soyuz uses – a hemispherical forward area joined by a barely angled (seven degrees) conical section to a classic spherical section heat shield. This shape allows a small amount of lift to be generated due to the unequal weight distribution. The nickname was thought up at a time when nearly every headlight was circular. The small dimensions of the descent module led to it having only two-man crews after the death of the Soyuz 11 crew. The later Soyuz T spacecraft solved this issue. Internal volume of Soyuz SA is 4 m³ (141 cu ft); 2.5 m³ (88 cu ft) is usable for crew (living space).
caption: Soyuz spacecraft's descent module
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