Editing Human spaceflight (section)

==== Launch ====
{{See also| Launch escape system}}
[[File:Sts33-e204.jpg|thumb|There was no practical way for the {{OV|99}}'s crew to safely abort before the [[Space Shuttle Challenger disaster|vehicle's violent disintegration]]]]

Since rockets have the potential for fire or explosive destruction, [[space capsule]]s generally employ some sort of [[launch escape system]], consisting either of a tower-mounted solid-fuel rocket to quickly carry the capsule away from the [[launch vehicle]] (employed on [[Project Mercury|Mercury]], [[Apollo (spacecraft)|Apollo]], and [[Soyuz spacecraft|Soyuz]], the escape tower being discarded at some point after launch, at a point where an abort can be performed using the spacecraft's engines), or else [[ejection seat]]s (employed on [[Vostok spacecraft|Vostok]] and [[Project Gemini|Gemini]]) to carry astronauts out of the capsule and away for individual parachute landings.

Such a launch escape system is not always practical for multiple-crew-member vehicles (particularly [[spaceplane]]s), depending on the location of egress hatch(es). When the single-hatch Vostok capsule was modified to become the 2 or 3-person [[Voskhod (spacecraft)|Voskhod]], the single-cosmonaut ejection seat could not be used, and no escape tower system was added. The two Voskhod flights in 1964 and 1965 avoided launch mishaps. The [[Space Shuttle]] carried ejection seats and escape hatches for its pilot and copilot in early flights; but these could not be used for passengers who sat below the flight deck on later flights, and so were discontinued.

There have been only two in-flight launch aborts of a crewed flight. The first occurred on [[Soyuz 7K-T No.39|Soyuz 18a]] on 5 April 1975. The abort occurred after the launch escape system had been jettisoned when the launch vehicle's spent second stage failed to separate before the third stage ignited and the vehicle strayed off course. The crew finally managed to separate the spacecraft, firing its engines to pull it away from the errant rocket, and both cosmonauts landed safely. The second occurred on 11 October 2018 with the launch of [[Soyuz MS-10]]. Again, both crew members survived.

In the first use of a launch escape system on the launchpad, before the start of a crewed flight, happened during the planned [[Soyuz 7K-ST No. 16L|Soyuz T-10a]] launch on 26 September 1983, which was aborted by a launch vehicle fire 90 seconds before liftoff. Both cosmonauts aboard landed safely.

The only crew fatality during launch occurred on 28 January 1986, when the [[Space Shuttle Challenger disaster|Space Shuttle ''Challenger'']] broke apart 73 seconds after liftoff, due to the failure of a [[Space Shuttle Solid Rocket Booster|solid rocket booster]] seal, which caused the failure of the [[Space Shuttle external tank|external fuel tank]], resulting in an explosion of the fuel and separation of the boosters. All seven crew members were killed.