Editing Space Shuttle (section)

==Mission profile==
===Launch preparation===
{{see also|Launch commit criteria}}
[[File:Crawler transporter with Atlantis on the ramp to pad 39A.jpg|thumb|right|alt=The Space Shuttle moving to the launch complex on a crawler-transporter|The crawler-transporter with ''Atlantis'' on the ramp to LC-39A for [[STS-117]]]]

The Space Shuttle was prepared for launch primarily in the VAB at the KSC. The SRBs were assembled and attached to the external tank on the MLP. The orbiter vehicle was prepared at the [[Orbiter Processing Facility]] (OPF) and transferred to the VAB, where a crane was used to rotate it to the vertical orientation and mate it to the external tank.<ref name= shuttle_manual />{{rp|132–133}} Once the entire stack was assembled, the MLP was carried for {{convert|3.5|mi|km|sigfig=2|sp=us|order=flip|adj=off|abbr=on}} to [[Launch Complex 39]] by one of the [[crawler-transporter]]s.<ref name= shuttle_manual />{{rp|137}} After the Space Shuttle arrived at one of the two launchpads, it would connect to the Fixed and Rotation Service Structures, which provided servicing capabilities, payload insertion, and crew transportation.<ref name= shuttle_manual />{{rp|139–141}} The crew was transported to the launch pad at T−3&nbsp;hours and entered the orbiter vehicle, which was closed at T−2&nbsp;hours.<ref name=jenkins2016 />{{rp|III–8}} Liquid oxygen and hydrogen were loaded into the external tank via umbilicals that attached to the orbiter vehicle, which began at T−5&nbsp;hours&nbsp;35&nbsp;minutes. At T−3&nbsp;hours&nbsp;45&nbsp;minutes, the hydrogen fast-fill was complete, followed 15&nbsp;minutes later by the oxygen tank fill. Both tanks were slowly filled up until the launch as the oxygen and hydrogen evaporated.<ref name=jenkins2016 />{{rp|II–186}}

The [[launch commit criteria]] considered precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity.<ref name="weather launch criteria">{{cite web |url=https://www.nasa.gov/centers/kennedy/news/releases/2003/release-20030128.html |last=Diller |first=George |author-link=George Diller |date=May 20, 1999 |url-status=dead |archive-url=https://web.archive.org/web/20200807074521/https://www.nasa.gov/centers/kennedy/news/releases/2003/release-20030128.html |title= Space Shuttle weather launch commit criteria and KSC end of mission weather landing criteria |access-date=May 1, 2020 |work=KSC Release No. 39-99 |publisher=NASA |department=[[Kennedy Space Center]] (KSC) |archive-date=August 7, 2020}}</ref> The Space Shuttle was not launched under conditions where it could have been struck by [[lightning]], as its exhaust plume could have triggered lightning by providing a current path to ground after launch, which occurred on [[Apollo 12#Mission highlights|Apollo&nbsp;12]].<ref name="chaikin">{{cite book |last=Chaikin |first=Andrew |author-link=Andrew Chaikin |title=A Man on the Moon: The Voyages of the Apollo Astronauts |publisher=[[Penguin Group]] |date=2007 |url=https://books.google.com/books?id=E043uAEACAAJ&q=a+man+on+the+moon |isbn=978-0-14-311235-8 |access-date=October 17, 2020 |archive-date=April 17, 2021 |archive-url=https://web.archive.org/web/20210417071628/https://books.google.com/books?id=E043uAEACAAJ&q=a+man+on+the+moon |url-status=live}}</ref>{{rp|239}} The NASA Anvil Rule for a Shuttle launch stated that an [[anvil cloud]] could not appear within a distance of {{convert|10|nmi|km|lk=in|order=flip|abbr=on}}.<ref name="anvil">{{cite web |last=Oblack |first=Rachelle |title=The Anvil Rule: How NASA Keeps Its Shuttles Safe form Thunderstorms |website=Thoughtco.com |date=March 5, 2018 |url=https://www.thoughtco.com/anvil-cloud-rule-3444263 |access-date=September 17, 2018 |archive-date=June 8, 2020 |archive-url=https://web.archive.org/web/20200608064339/https://www.thoughtco.com/anvil-cloud-rule-3444263 |url-status=live}}</ref> The Shuttle Launch Weather Officer monitored conditions until the final decision to scrub a launch was announced. In addition to the weather at the launch site, conditions had to be acceptable at one of the [[Space Shuttle abort modes#Transoceanic abort landing|Transatlantic Abort Landing sites]] and the SRB recovery area.<ref name="weather launch criteria" /><ref name="sts121_blog">{{cite web |title=NASA's Launch Blog – Mission STS-121 |publisher=NASA |date=July 1, 2006 |url=https://www.nasa.gov/mission_pages/shuttle/launch/sts-121/launch-vlcc_070106.html |access-date=May 1, 2020 |archive-date=May 24, 2017 |archive-url=https://web.archive.org/web/20170524123552/https://www.nasa.gov/mission_pages/shuttle/launch/sts-121/launch-vlcc_070106.html |url-status=live}}</ref>

===Launch===
[[File:ShuttleLaunch.gif|thumb|Early ignition and lift-off view of main-engines and SRB (ground-camera view)]]
The mission crew and the Launch Control Center (LCC) personnel completed systems checks throughout the countdown. Two built-in holds at T−20&nbsp;minutes and T−9&nbsp;minutes provided scheduled breaks to address any issues and additional preparation.<ref name=jenkins2016 />{{rp|III–8}} After the built-in hold at T−9&nbsp;minutes, the countdown was automatically controlled by the Ground Launch Sequencer (GLS) at the LCC, which stopped the countdown if it sensed a critical problem with any of the Space Shuttle's onboard systems.<ref name="sts121_blog" /> At T−3&nbsp;minutes&nbsp;45&nbsp;seconds, the engines began conducting gimbal tests, which were concluded at T−2&nbsp;minutes&nbsp;15&nbsp;seconds. The ground [[Launch Processing System]] handed off the control to the orbiter vehicle's GPCs at T−31&nbsp;seconds. At T−16&nbsp;seconds, the GPCs armed the SRBs, the sound suppression system (SPS) began to drench the MLP and SRB trenches with {{convert|300000|USgal|L|sigfig=2|order=flip|sp=us|abbr=on}} of water to protect the orbiter vehicle from damage by [[acoustical]] energy and rocket exhaust reflected from the flame trench and MLP during lift-off.<ref name="sound_suppression">{{cite web |url=http://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html |title=Sound Suppression System |date=November 23, 2007 |last=Ryba |first=Jeanne |publisher=NASA |access-date=March 22, 2020 |archive-date=June 29, 2011 |archive-url=https://web.archive.org/web/20110629143632/http://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html |url-status=live}}</ref><ref name="sps">{{cite web |title=Sound Suppression Water System |publisher=NASA |date=August 28, 2000 |last=Grinter |first=Kay |url=http://www-pao.ksc.nasa.gov/kscpao/nasafact/count4ssws.htm |archive-url=https://web.archive.org/web/20140313042409/http://www-pao.ksc.nasa.gov/kscpao/nasafact/count4ssws.htm |archive-date=March 13, 2014 |url-status=dead |access-date=April 9, 2020}}</ref> At T−10&nbsp;seconds, hydrogen igniters were activated under each engine bell to quell the stagnant gas inside the cones before ignition. Failure to burn these gases could trip the onboard sensors and create the possibility of an overpressure and explosion of the vehicle during the firing phase. The hydrogen tank's prevalves were opened at T−9.5&nbsp;seconds in preparation for engine start.<ref name=jenkins2016 />{{rp|II–186}}

[[File:STS 135 Launch.gif|thumb|Shuttle lift-off via on-board camera view.]]
Beginning at T−6.6&nbsp;seconds, the main engines were ignited sequentially at 120-millisecond intervals. All three RS-25 engines were required to reach 90% rated thrust by T−3&nbsp;seconds, otherwise the GPCs would initiate an [[RSLS Abort|RSLS abort]]. If all three engines indicated nominal performance by T−3&nbsp;seconds, they were commanded to gimbal to liftoff configuration and the command would be issued to arm the SRBs for ignition at T−0.<ref name="countdown101">{{cite web |last=Ryba |first=Jeanne |title=Countdown 101 |publisher=NASA |date=September 17, 2009 |url=http://www.nasa.gov/mission_pages/shuttle/launch/countdown101.html |access-date=March 22, 2020 |archive-date=January 26, 2020 |archive-url=https://web.archive.org/web/20200126124224/https://www.nasa.gov/mission_pages/shuttle/launch/countdown101.html |url-status=live}}</ref> Between T−6.6&nbsp;seconds and T−3&nbsp;seconds, while the RS-25 engines were firing but the SRBs were still bolted to the pad, the offset thrust would cause the Space Shuttle to pitch down {{convert|25.5|in|abbr=on|order=flip}} measured at the tip of the external tank; the 3-second delay allowed the stack to return to nearly vertical before SRB ignition. This movement was nicknamed the "twang." At T−0, the eight [[Pyrotechnic fastener|frangible nuts]] holding the SRBs to the pad were detonated, the final umbilicals were disconnected, the SSMEs were commanded to 100% throttle, and the SRBs were ignited.<ref name=nuts0>{{cite web |url=http://www.nasa.gov/centers/marshall/pdf/290339main_8-388221J.pdf |title=Space Shuttle Solid Rocket Booster |access-date=March 22, 2020 |publisher=NASA |date=November 2008 |last=Roy |first=Steve |archive-date=November 13, 2018 |archive-url=https://web.archive.org/web/20181113090531/https://www.nasa.gov/centers/marshall/pdf/290339main_8-388221J.pdf |url-status=live}}</ref><ref name="frang_nut_liftoff">{{cite web |title=Solid Rocket Boosters |date=August 31, 2000 |last=Dumoulin |first=Jim |url=http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/srb.html |publisher=NASA |access-date=March 22, 2020 |archive-date=February 16, 2012 |archive-url=https://web.archive.org/web/20120216005534/http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/srb.html |url-status=live}}</ref> By T+0.23&nbsp;seconds, the SRBs built up enough thrust for liftoff to commence, and reached maximum chamber pressure by T+0.6&nbsp;seconds.<ref>{{cite web |title=Shuttle Crew Operations Manual |url=http://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf |publisher=NASA |access-date=May 4, 2018 |archive-date=December 16, 2017 |archive-url=https://web.archive.org/web/20171216034929/https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf |url-status=live}}</ref><ref name=jenkins2016 />{{rp|II–186}} At T−0, the JSC [[Mission Control Center]] assumed control of the flight from the LCC.<ref name=jenkins2016 />{{rp|III–9}}

[[File:STS135 SRB Separation.gif|thumb|On-board camera-view of SRB separation.]]
At T+4&nbsp;seconds, when the Space Shuttle reached an altitude of {{convert|73|ft|m|sigfig=2|sp=us|order=flip|adj=off}}, the RS-25 engines were throttled up to 104.5%. At approximately T+7&nbsp;seconds, the Space Shuttle rolled to a heads-down orientation at an altitude of {{convert|350|ft|m|sigfig=2|sp=us|order=flip|adj=off}}, which reduced aerodynamic stress and provided an improved communication and navigation orientation. Approximately 20–30&nbsp;seconds into ascent and an altitude of {{convert|9000|ft|m|sigfig=2|sp=us|order=flip|adj=off}}, the RS-25 engines were throttled down to 65–72% to reduce the maximum aerodynamic forces at [[Max Q]].<ref name=jenkins2016 />{{rp|III–8–9}} Additionally, the shape of the SRB propellant was designed to cause thrust to decrease at the time of Max Q.<ref name=jenkins />{{rp|427}}  The GPCs could dynamically control the throttle of the RS-25 engines based upon the performance of the SRBs.<ref name=jenkins2016 />{{rp|II–187}}

[[File:Shuttle ET Separation STS-135.gif|thumb|On-board camera-view of external-tank separation]]
At approximately T+123&nbsp;seconds and an altitude of {{convert|150000|ft|m|sigfig=2|sp=us|order=flip|adj=off}}, pyrotechnic fasteners released the SRBs, which reached an [[apogee]] of {{convert|220000|ft|m|sigfig=2|sp=us|order=flip|adj=off}} before parachuting into the [[Atlantic Ocean]]. The Space Shuttle continued its ascent using only the RS-25 engines. On earlier missions, the Space Shuttle remained in the heads-down orientation to maintain communications with the [[tracking station]] in [[Cooper's Island, Bermuda|Bermuda]], but later missions, beginning with [[STS-87]], rolled to a heads-up orientation at T+6&nbsp;minutes for communication with the [[tracking and data relay satellite]] constellation. The RS-25 engines were throttled at T+7&nbsp;minutes&nbsp;30&nbsp;seconds to limit vehicle acceleration to 3 ''g''. At 6&nbsp;seconds prior to main engine cutoff (MECO), which occurred at T+8&nbsp;minutes&nbsp;30&nbsp;seconds, the RS-25 engines were throttled down to 67%. The GPCs controlled ET separation and dumped the remaining liquid oxygen and hydrogen to prevent outgassing while in orbit. The ET continued on a ballistic trajectory and broke up during reentry, with some small pieces landing in the Indian or Pacific Ocean.<ref name=jenkins2016 />{{rp|III–9–10}}

Early missions used two firings of the OMS to achieve orbit; the first firing raised the apogee while the second circularized the orbit. Missions after [[STS-38]] used the RS-25 engines to achieve the optimal apogee, and used the OMS engines to circularize the orbit. The orbital altitude and inclination were mission-dependent, and the Space Shuttle's orbits varied from {{convert|120|to|335|nmi|km|sigfig=2|sp=us|adj=off|abbr=on|order=flip}}.<ref name=jenkins2016 />{{rp|III–10}}

===In orbit===
[[File:Endeavour docked to ISS.jpg|thumb|right|alt=The Space Shuttle Endeavour docked with the International Space Station|''Endeavour'' docked at ISS during the STS-134 mission]]

The type of mission the Space Shuttle was assigned to dictate the type of orbit that it entered. The initial design of the reusable Space Shuttle envisioned an increasingly cheap launch platform to deploy commercial and government satellites. Early missions routinely ferried satellites, which determined the type of orbit that the orbiter vehicle would enter. Following the ''Challenger'' disaster, many commercial payloads were moved to expendable commercial rockets, such as the [[Delta II]].<ref name=jenkins2016 />{{rp|III–108, 123}} While later missions still launched commercial payloads, Space Shuttle assignments were routinely directed towards scientific payloads, such as the [[Hubble Space Telescope]],<ref name=jenkins2016 />{{rp|III–148}} Spacelab,<ref name=jenkins />{{rp|434–435}} and the [[Galileo (spacecraft)|Galileo spacecraft]].<ref name=jenkins2016 />{{rp|III–140}}  Beginning with [[STS-71]], the orbiter vehicle conducted dockings with the [[Mir space station]].<ref name=jenkins2016 />{{rp|III–224}} In its final decade of operation, the Space Shuttle was used for the construction of the [[International Space Station]].<ref name=jenkins2016 />{{rp|III–264}} Most missions involved staying in orbit several days to two weeks, although longer missions were possible with the [[Extended Duration Orbiter]] pallet.<ref name=jenkins2016 />{{rp|III–86}} The 17 day 15 hour [[STS-80]] mission was the longest Space Shuttle mission duration.<ref name=jenkins2016 />{{rp|III–238}}

===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}}

===Post-landing processing===
{{main|Orbiter Processing Facility}}
[[File:Discovery mission completed q.jpg|thumb|alt=The Space Shuttle Discovery on the runway as ground crews work to get the crew out of the orbiter|''Discovery'' being prepared after landing for crew disembarkment following [[STS-114]]]]

After the landing, ground crews approached the orbiter to conduct safety checks. Teams wearing self-contained breathing gear tested for the presence of [[hydrogen]], [[hydrazine]], monomethylhydrazine, [[nitrogen tetroxide]], and [[ammonia]] to ensure the landing area was safe.<ref name=afterlandingpao>{{cite web |title=From Landing to Launch Orbiter Processing |url=http://www-pao.ksc.nasa.gov/kscpao/nasafact/pdf/orbiterprocessing2002.pdf |publisher=NASA |access-date=June 30, 2011 |date=2002 |url-status=dead |archive-url=https://web.archive.org/web/20110721053142/http://www-pao.ksc.nasa.gov/kscpao/nasafact/pdf/orbiterprocessing2002.pdf |archive-date=July 21, 2011}}</ref> Air conditioning and Freon lines were connected to cool the crew and equipment and dissipate excess heat from reentry.<ref name=jenkins2016 />{{rp|III-13}} A [[flight surgeon]] boarded the orbiter and performed medical checks of the crew before they disembarked. 
Once the orbiter was secured, it was towed to the OPF to be inspected, repaired, and prepared for the next mission.<ref name=afterlandingpao/> The processing included:
* removal and installation of mission-specific items and payloads
* draining of waste and leftover consumables, and refilling of new consumables
* inspection and (if necessary) repair of the thermal protection system
* checkout and servicing of main engines (done in the [[Main Engine Processing Facility]] to facilitate easier access, necessitating their removal from the orbiter)
* if necessary, removal of the [[Orbital Maneuvering System]] and [[Reaction Control System]] pods for maintenance at the [[Hypergol Maintenance Facility]]
* installation of any mid-life upgrades and modifications