section_path: Safety concerns/Equipment hazards/Launch
section_name: Launch
paragraph_text: Launch
  
  Since rockets have the potential for fire or explosive destruction, space capsules 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 Mercury, Apollo, and 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 seats (employed on Vostok and 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 spaceplanes), depending on the location of egress hatch(es). When the single-hatch Vostok capsule was modified to become the 2 or 3-person 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 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 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 broke apart 73 seconds after liftoff, due to the failure of a solid rocket booster seal, which caused the failure of the external fuel tank, resulting in an explosion of the fuel and separation of the boosters. All seven crew members were killed.