Editing Space capsule (section)

===Vostok===
[[File:Vostok_Spacecraft_Diagram.svg|thumb|right|The Vostok space capsule|link=Special:FilePath/Vostok_spacecraft_diagram.svg]]
{{Main|Vostok (spacecraft)}}
The Vostok was the [[Soviet Union]]'s first crewed space capsule. The first [[human spaceflight]] was [[Vostok 1]], accomplished on [[Cosmonautics Day|April 12, 1961]] by [[cosmonaut]] [[Yuri Gagarin]].

The capsule was originally designed for use both as a camera platform for the Soviet Union's first spy satellite program, [[Zenit spy satellite|Zenit]] and as a crewed spacecraft. This [[dual-use]] design was crucial in gaining [[Communist Party of the Soviet Union|Communist Party]] support for the program. The design used a spherical reentry module, with a biconic descent module containing [[Spacecraft attitude control|attitude control]] thrusters, on-orbit consumables, and the retro rocket for orbit termination. The basic design has remained in use for some 40 years, gradually adapted for a range of other uncrewed [[satellite]]s.

It was a single-seat capsule that was 4.4 meters long and 2.4 meters in diameter, weighing 4.73 tonnes at launch.<ref>{{Cite book |title= Spacecraft Systems Engineering|url=https://search.ebscohost.com/login.aspx?authtype=ip,guest&custid=s4858255&groupid=main&profile=eds&direct=true&db=cat05987a&AN=unm.31514445&site=eds-live&scope=site |isbn=9780471952206 | last1=Fortescue | first1=Peter | last2=Stark | first2=John | date=13 September 1995 | publisher=Wiley }}</ref> The reentry module was completely covered in ablative heat shield material, {{convert|2.3|m|ft|sp=us}} in diameter, weighing {{convert|2460|kg|lb}}. The capsule was covered with a [[nose cone]] to maintain a low-drag profile for launch, with a cylindrical interior cabin approximately {{convert|1|m|ft|sp=us}} in diameter nearly perpendicular to the capsule's longitudinal axis. The cosmonaut sat in an ejection seat with a separate parachute for escape during a launch emergency and landing during a normal flight. The capsule had its own parachute for landing on the ground. Although official sources stated that Gagarin had landed inside his capsule, a requirement for qualifying as a first crewed spaceflight under [[International Aeronautical Federation]] (IAF) rules, it was later revealed that all Vostok cosmonauts ejected and landed separately from the capsule. The capsule was serviced by an aft-facing conical equipment module {{convert|2.25|m|ft|sp=us}} long by {{convert|2.43|m|ft|sp=us}}, weighing {{convert|2270|kg|lb}} containing nitrogen and oxygen breathing gasses, batteries, fuel, [[Spacecraft attitude control|attitude control]] thrusters, and the retrorocket. It could support flights as long as ten days.<ref>{{cite web|url = http://www.braeunig.us/space/specs/vostok.htm |title = Vostok Specifications|website = braeunig.us}}</ref> Six Vostok launches were successfully conducted, the last two pairs in concurrent flights. The longest flight was just short of five days, on [[Vostok 5]] on June 14–19, 1963.<ref>{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-020A |title= NASA - NSSDCA - Spacecraft - Trajectory Details|website=nssdc.gsfc.nasa.gov|access-date=2018-05-02}}</ref>

Since the attitude control thrusters were located in the instrument module which was discarded immediately prior to reentry, the reentry module's path and orientation could not be actively controlled. This meant that the capsule had to be protected from reentry heat on all sides, determining the spherical design (as opposed to [[Project Mercury]]'s conical design, which allowed for maximum volume while minimizing the heat shield diameter).{{Citation needed|date=December 2019}} During reentry, the heat of atmospheric friction is so great that air molecules around the capsule are ionized, creating a layer of plasma around the capsule which blocks radio communication with the ground. However, ionized gases in the plasma layer can also be used to create an artificial radio window, allowing communication signals to be transmitted and received despite the interference.<ref>{{Cite book |title=Aeronomy |url=https://www.sciencedirect.com/book/9780120778027/aeronomy |access-date=2023-03-08 |isbn=9780120778027 |language=en |last1=Banks |first1=Peter M. |last2=Kockarts |first2=G. |year=1973 |publisher=Academic Press }}</ref> Some control of the capsule's reentry orientation was possible by offsetting its center of gravity. Proper orientation with the cosmonaut's back to the direction of flight was necessary in order to best sustain the which also maximized the  8 to 9 [[g-force]].