Editing Space Shuttle (section)

===Re-entry and landing===
[[File:Space Shuttle reentry aboard flight deck.jpg|thumb|alt=A view of the commander and pilot during reentry on STS-42|Flight deck view of ''Discovery'' during [[STS-42]] re-entry]]

Approximately four hours prior to deorbit, the crew began preparing the orbiter vehicle for reentry by closing the payload doors, radiating excess heat, and retracting the Ku&nbsp;band antenna. The orbiter vehicle maneuvered to an upside-down, tail-first orientation and began a 2–4&nbsp;minute OMS burn approximately 20&nbsp;minutes before it reentered the atmosphere. The orbiter vehicle reoriented itself to a nose-forward position with a 40° angle-of-attack, and the forward [[reaction control system]] (RCS) jets were emptied of fuel and disabled prior to reentry. The orbiter vehicle's reentry was defined as starting at an altitude of {{convert|400000|ft|km|abbr=on|sigfig=2|order=flip}}, when it was traveling at approximately Mach 25. The orbiter vehicle's reentry was controlled by the GPCs, which followed a preset angle-of-attack plan to prevent unsafe heating of the TPS. During reentry, the orbiter's speed was regulated by altering the amount of drag produced, which was controlled by means of angle of attack, as well as bank angle. The latter could be used to control drag without changing the angle of attack. A series of roll reversals{{refn|group=lower-alpha|A roll reversal is a maneuver where the bank angle is altered from one side to another. They are used to control the deviation of the azimuth from the prograde vector that results from using high bank angles to create drag.}} were performed to control azimuth while banking.<ref>{{Citation |title=Space Shuttle Reentry In-depth | date=July 25, 2020 |url=https://www.youtube.com/watch?v=lA91evJ-wdk |language=en |access-date=October 24, 2022 |archive-date=January 18, 2023 |archive-url=https://web.archive.org/web/20230118120755/https://www.youtube.com/watch?v=lA91evJ-wdk |url-status=live}}</ref> The orbiter vehicle's aft RCS jets were disabled as its ailerons, elevators, and rudder became effective in the lower atmosphere. At an altitude of {{convert|150000|ft|km|abbr=on|sigfig=2|order=flip}}, the orbiter vehicle opened its [[speed brake]] on the vertical stabilizer. At 8&nbsp;minutes&nbsp;44&nbsp;seconds prior to landing, the crew deployed the air data probes, and began lowering the angle-of-attack to 36°.<ref name=jenkins2016 />{{rp|III–12}}  The orbiter's maximum [[glide ratio]]/[[lift-to-drag ratio]] varied considerably with speed, ranging from 1.3 at [[hypersonic]] speeds to 4.9 at subsonic speeds.<ref name=jenkins2016 />{{rp|II–1}} The orbiter vehicle flew to one of the two Heading Alignment Cones, located {{convert|30|mi|km|sigfig=2|sp=us|order=flip|adj=off|abbr=on}} away from each end of the runway's centerline, where it made its final turns to dissipate excess energy prior to its approach and landing. Once the orbiter vehicle was traveling subsonically, the crew took over manual control of the flight.<ref name=jenkins2016 />{{rp|III–13}}

[[File:Space Shuttle Discovery Landing after STS-124.jpg|thumb|right|alt=Discovery deployed a parachute to slow itself after landing|''Discovery'' deploying its [[Drogue parachute|brake parachute]] after landing on [[STS-124]]]]
The approach and landing phase began when the orbiter vehicle was at an altitude of {{convert|10000|ft|m|sigfig=2|sp=us|adj=off|abbr=on|order=flip}} and traveling at {{convert|300|kn|m/s|sigfig=2|sp=us|order=flip|adj=off|abbr=on}}. The orbiter followed either a {{hyphen}}20° or {{hyphen}}18° glideslope and descended at approximately {{convert|167|ft/s|m/s|sigfig=2|sp=us|order=flip|adj=off|abbr=on}}. The speed brake was used to keep a continuous speed, and crew initiated a pre-flare maneuver to a {{hyphen}}1.5° glideslope at an altitude of {{convert|2000|ft|m|sigfig=2|sp=us|adj=off|abbr=on|order=flip}}. The landing gear was deployed 10&nbsp;seconds prior to touchdown, when the orbiter was at an altitude of {{convert|300|ft|m|sigfig=2|sp=us|adj=off|abbr=on|order=flip}} and traveling {{convert|288|kn|m/s|sigfig=2|sp=us|order=flip|adj=off|abbr=on}}. A final flare maneuver reduced the orbiter vehicle's descent rate to {{convert|3|ft/s|m/s|sigfig=1|sp=us|order=flip|adj=off|abbr=on}}, with touchdown occurring at {{convert|195-295|kn|m/s|sigfig=2|sp=us|order=flip|adj=off|abbr=on}}, depending on the weight of the orbiter vehicle. After the landing gear touched down, the crew deployed a drag chute out of the vertical stabilizer, and began wheel braking when the orbiter was traveling slower than {{convert|140|kn|m/s|sigfig=2|sp=us|order=flip|adj=off|abbr=on}}. After the orbiter's wheels stopped, the crew deactivated the flight components and prepared to exit.<ref name=jenkins2016 />{{rp|III–13}}

====Landing sites====
{{see also|List of Space Shuttle landing sites}}

The primary Space Shuttle landing site was the [[Shuttle Landing Facility]] at KSC, where 78 of the 133 successful landings occurred. In the event of unfavorable landing conditions, the Shuttle could delay its landing or land at an alternate location. The primary alternate was Edwards AFB, which was used for 54 landings.<ref name=jenkins2016 />{{rp|III–18–20}} [[STS-3]] landed at the [[White Sands Space Harbor]] in [[New Mexico]] and required extensive post-processing after exposure to the [[gypsum]]-rich sand, some of which was found in ''Columbia'' debris after [[STS-107]].<ref name=jenkins2016 />{{rp|III–28}} Landings at alternate airfields required the Shuttle Carrier Aircraft to transport the orbiter back to [[Cape Canaveral]].<ref name=jenkins2016 />{{rp|III–13}}

In addition to the pre-planned landing airfields, there were 85 agreed-upon [[emergency landing sites]] to be used in different abort scenarios, with 58 located in other countries. The landing locations were chosen based upon political relationships, favorable weather, a runway at least {{convert|7500|ft|m|sigfig=2|sp=us|adj=off|abbr=on|order=flip}} long, and [[TACAN]] or [[Distance measuring equipment|DME]] equipment. Additionally, as the orbiter vehicle only had UHF radios, international sites with only VHF radios would have been unable to communicate directly with the crew. Facilities on the east coast of the US were planned for East Coast Abort Landings, while several sites in Europe and Africa were planned in the event of a Transoceanic Abort Landing. The facilities were prepared with equipment and personnel in the event of an emergency shuttle landing but were never used.<ref name=jenkins2016 />{{rp|III–19}}