Editing STS-1 (section)

== Mission summary ==
[[File:STS-1 Space Shuttle Columbia discarded external tank.jpg|thumb|upright=1.0|right|The external tank is released from the Space Shuttle orbiter.]]

The first launch of the Space Shuttle occurred on April 12, 1981, exactly 20{{nbsp}}years after the [[Vostok 1|first crewed space flight]], when the [[Space Shuttle orbiter|orbiter]] ''Columbia'' lifted off from Pad A, [[Kennedy Space Center Launch Complex 39A|Launch Complex 39]], at the [[Kennedy Space Center]]. The launch took place at 12:00:04{{nbsp}}[[Coordinated Universal Time|UTC]]. A launch attempt two days earlier was scrubbed because ''Columbia''{{'}}s four primary general purpose [[IBM System/4 Pi]] computers (GPCs) failed to provide correct timing to the backup flight system (BFS) when the GPCs were scheduled to transition from vehicle checkout to flight configuration mode.

{{LaunchAttempt
| date1           = April 10, 1981, 7:00:00
| result1         = Scrubbed
| reason1         = Technical
| decision_date1  = 
| decision_clock1 = −18 minutes
| weathergo1      = 
| notes1          = Timing problem in one of ''Columbia''{{'}}s general purpose [[IBM System/4 Pi]] computers. A software patch was installed to correct.<ref>{{cite web|title=Space Shuttle Mission Summary |url=https://www.jsc.nasa.gov/history/reference/TM-2011-216142.pdf|publisher=NASA Johnson Space Center|access-date=February 4, 2017|archive-url=https://web.archive.org/web/20161222121120/http://www.jsc.nasa.gov/history/reference/TM-2011-216142.pdf|archive-date=December 22, 2016|url-status=dead|date=February 11, 2015}} {{PD-notice}}</ref>
| date2           = April 12, 1981, 7:00:04
| result2         = Success
}}

Not only was this the first launch of the Space Shuttle, but it marked the first time that [[solid-fuel rocket]]s were used for a NASA crewed launch (although previous systems had used solid-fuel motors for their [[Launch escape system|escape towers]] or retro rockets). STS-1 was also the first U.S. crewed space vehicle launched without an [[Uncrewed spacecraft|uncrewed]] powered test flight. The STS-1 orbiter, ''Columbia'', also holds the record for the amount of time spent in the [[Orbiter Processing Facility]] (OPF) before launch – 610 days, the time needed for the replacement of many of its [[Space Shuttle thermal protection system|heat shield tiles]].

The NASA mission objective for the maiden flight was to accomplish a safe ascent into orbit and return to Earth for a safe landing of Orbiter and crew. The only payload carried on the mission was a Development Flight Instrumentation (DFI) package, which contained sensors and measuring devices to record the orbiter's performance and the stresses that occurred during launch, ascent, orbital flight, descent and landing. All 113 flight test objectives were accomplished, and the orbiter's [[spaceworthiness]] was verified.

During the final T−9{{nbsp}}minute holding period, Launch Director George Page read a message of good wishes to the crew from [[President of the United States|President]] [[Ronald Reagan]], ending with, "John, we can't do more from the launch team than say, we wish you an awful lot of luck. We are with you one thousand percent and we are awful proud to have been a part of it. Good luck gentlemen."

Ignition of the three [[RS-25]] main engines was sensed as a sharp increase in noise. The stack rocked "downwards" (towards the crew's feet), then back up to the vertical, at which point both [[Space Shuttle Solid Rocket Booster|Solid Rocket Boosters]] (SRBs) ignited. Crippen likened lift-off to a "steam catapult shot" (such as when an aircraft is launched from an aircraft carrier). The stack's combined northwards translation and climb above the launch tower's lightning rod were readily apparent to Young. After clearing the tower the stack began a right roll (until the +Z axis or vertical fin pointed) to a launch azimuth of 067° True<ref>{{cite report|title=Mission Operation Report Space Shuttle Program STS-1 Postflight Report|publisher=NASA|date=1981}} {{PD-notice}}</ref> (in order to achieve an orbital inclination of 40.30°), and pitched to a "heads down" attitude (to reduce loading on the wings<ref>{{cite report |title=Why The Wings Stay On The Space Shuttle Orbiter During First Stage Ascent |last=Ehrlich |first=C. F. Jr |date= |publisher=AIAA}}</ref>). Simultaneously control was passed from the launch team in [[Florida]] to [[Flight controller|Flight Director]] Neil Hutchinson's Silver team in [[Mission Control Center|Flight Control Room 1]] (FCR 1) in [[Texas]] with astronaut [[Dan Brandenstein]] as their CAPCOM.

''Columbia'''s main engines were throttled down to 65% thrust to transit the region of [[Max q|Max Q]], the point during ascent when the shuttle undergoes maximum aerodynamic stress. This occurred 56 seconds into the flight at [[Mach Number|Mach]]{{nbsp}}1.06.<ref>{{cite web |author=Bennett |first=Floyd V. |last2=Legler |first2=Robert D. |date=2011 |title=Space Shuttle Missions Summary, NASA TM-2011-216142 |url=https://spaceflight.nasa.gov/outreach/SignificantIncidents/assets/space-shuttle-missions-summary.pdf |url-status=dead |archive-url=https://web.archive.org/web/20170126160832/https://spaceflight.nasa.gov/outreach/SignificantIncidents/assets/space-shuttle-missions-summary.pdf |archive-date=January 26, 2017 |publisher=NASA}} {{PD-notice}}</ref> The wind corrected value was {{cvt|29|kPa}} (predicted {{cvt|28|kPa}}, limit {{cvt|30|kPa}}). The two SRBs performed better than expected causing a [[lofted trajectory]], and were jettisoned after burnout at 2 minutes and 12 seconds (at {{cvt|53000|m}} altitude, {{cvt|2800|m}} higher than planned). After 8 minutes and 34 seconds [[Mission Elapsed Time]] (MET), the main engines were shut down (MECO, at altitude {{cvt|118000|m}}) and the external tank was jettisoned 18 seconds later to eventually break up and impact in the [[Indian Ocean]]. Two twin-engined [[Orbital Maneuvering System]] (OMS) engine burns of 86 seconds duration initiated at 10 minutes and 34 seconds MET and 75 seconds duration at 44 minutes 2 seconds MET inserted ''Columbia'' into a {{cvt|246|xx|248|km}} orbit. This subtle deviation from the original plan<ref>{{cite report|title=Mission Operation Report Space Shuttle Program STS-1 Launch |publisher=NASA|date=1981}} {{PD-notice}}</ref> of {{cvt|240|km}} circular went largely unnoticed. In fact, it adjusted the spacecraft's orbital period to take account of the April 10, 1981, scrub, so that attempts could still be made to use [[KH-11 Kennen|KH-11]] [[reconnaissance satellite]]s to image ''Columbia'' on orbit.<ref name="White">{{cite book |last1=White |first1=Rowland |url=https://books.google.com/books?id=R370CwAAQBAJ&pg=PA243 |title=Into the Black: The Extraordinary Untold Story of the First Flight of the Space Shuttle Columbia and the Astronauts Who Flew Her (revised) |last2=Truly |first2=Richard |author-link2=Richard H. Truly |date=2017 |publisher=Touchstone |isbn=9781501123634 |page=243}}</ref> Overall Young commented that there was a lot less vibration and noise during launch than they had expected. However, the sensations accompanying the first firing of the large [[Reaction control system|Reaction Control System]] (RCS) jets surprised the crew. Crippen commented "it's like a big cannon just fired ... you don't like them the first time you hear them". Young reported that "the entire cabin vibrates ... it felt like the nose was being bent".

Once on-orbit both crew members safed their ejection seats and unstrapped. The next critical event was payload bay door opening. This was essential to allow heat rejection from ''Columbia''{{'}}s systems via the doors' space radiators. Failure to open these by the end of the second orbit would have resulted in a return to Earth at the end of the fifth orbit, before the limited capacity of the flash evaporator cooling system was exceeded. As they opened the doors the crew noticed that they had sustained damage to [[thermal protection system]] (TPS) tiles on the OMS pods. This was televised to the ground. Shortly afterwards Young, then Crippen doffed their emergency ejection suits.

The majority of the crew's approximately 53{{nbsp}}hours in [[low Earth orbit]] was spent conducting systems tests. Despite the scheduling impact of efforts to image ''Columbia''{{'}}s TPS by utilizing external assets, these were all accomplished. They included: Crew Optical Alignment Sight (COAS) calibration, star tracker performance, [[Inertial measurement unit|Inertial Measurement Unit]] (IMU) performance, manual and automatic RCS testing, radiation measurement, propellant crossfeeding, hydraulics functioning, fuel cell purging, and photography. The OMS-3 and OMS-4 burns at 006:20:46 and 007:05:32 MET respectively raised this orbit to {{cvt|273.9|xx|274.1|km}} (compared to a planned {{cvt|280|km|sigfig=3}} circular). These two firings were single engined utilizing the crossfeed system.<ref>{{cite book |author=A. |first=Cohen |url=https://ia803001.us.archive.org/21/items/48011357STS1OrbiterFinalMissionReport/48011357-STS-1-Orbiter-Final-Mission-Report.pdf |title=STS-1 Orbiter Final Mission Report |date=1981 |publisher=NASA JSC Mission Evaluation Team |pages=7 to 10}} {{PD-notice}}</ref> The crew reported a cold first night on board despite acceptable temperature indications. They found the second night comfortable after settings were adjusted.

During the second day of the mission, the astronauts received a phone call from [[Vice President of the United States|Vice President]] [[George H. W. Bush]]. [[President of the United States|President]] [[Ronald Reagan]] had originally intended to visit the [[Christopher C. Kraft Jr. Mission Control Center|Mission Control Center]] during the mission, but at the time was still recovering from an [[Attempted assassination of Ronald Reagan|assassination attempt]] which had taken place two weeks before the launch (Reagan had only returned home to the [[White House]] the day prior to the launch).

The crew awoke from their second sleep period earlier than planned. Preparations for return to Earth began with breakfast. Stowing of cabin items, flight control system checkout, data processing system reconfigurations, and then ejection suit donning followed. In Houston, the Crimson team headed by their [[Flight controller|Flight Director]] [[Don Puddy]] came on duty in FCR{{nbsp}}1 for the mission's final shift. His CAPCOM was astronaut [[Joseph P. Allen]] with [[Frederick Hauck]] assisting. Payload bay door closing was a critical milestone to ensure vehicle structural and thermal integrity for re-entry. If power closing had failed, Crippen was trained to conduct a one-man [[extravehicular activity]] (EVA) to manually winch them closed. With cabin switch positions verified, the crew strapped into their ejection seats. Meanwhile, [[Johnson Space Center]] (JSC) pilots Charlie Hayes and Ted Mendenhall were airborne over [[California]]'s [[Edwards Air Force Base]] area in a [[Shuttle Training Aircraft]] (STA) performing a final check of landing weather conditions.

[[Auxiliary power unit|Auxiliary Power Unit]]s (APUs) 2 and 3 were started (to provide flight control hydraulic pressure). The 160-second twin-engine OMS de-orbit burn took place during the 36th orbit over the southern Indian Ocean and changed the orbital parameters from {{cvt|270|xx|274|km}} to {{cvt|270|xx|0|km}}. This ensured atmospheric capture of the spacecraft close enough to the planned landing site to have sufficient energy for a controlled glide landing, but not so close that energy would have to be dissipated at a rate exceeding its structural capability. Young then slowly pitched ''Columbia'' up to the wings level nose high entry attitude. Both crew members armed their ejection seats during this pitch around. Nearly half an hour later APU 1 was started as planned. Shortly afterwards, ''Columbia'' entered an approximately 21-minute long communications blackout. This was due to a combination of ionization (16 minutes) and lack of ground station coverage between [[Guam]] and Buckhorn Tracking Station at Dryden Flight Research Facility.<ref>{{cite report |title=Tracking and Data Acquisition/Space Operations |publisher=NASA |series=NASA Historical Data Books |number=SP-4012 |url=https://history.nasa.gov/SP-4012/vol6/vol_vi_ch_4.pdf |access-date=April 20, 2022}}</ref> Entry Interface (EI) was reached over the eastern [[Pacific Ocean]] {{cvt|8110|km}} from the landing site at a speed of around {{cvt|28240|km/h}}. EI is merely an arbitrarily defined geodetic altitude of {{cvt|120000|m}} employed by NASA for the purposes of trajectory computations and mission planning. Above this altitude, the spacecraft is considered to be outside the "sensable atmosphere".<ref>{{cite book |author=Woods |first=W. David |title=How Apollo Flew to the Moon |date=2011 |publisher=Springer-Praxis |isbn=978-1-4419-7178-4 |page=469}}</ref>

Most of this first orbiter entry was flown automatically. An initial [[angle of attack]] of 40° had to be maintained until through the most severe aerodynamic heating after which it was gradually reduced. At about {{cvt|100000|m}} altitude a light pink air glow caused by entry heating became visible, and both crew members lowered their visors. ''Columbia'' had to maneuver {{cvt|583|km}} "cross range" of its orbital ground track to reach the planned landing site during the entry. Consequently, a roll into a right bank was flown when the air density had increased sufficiently to raise dynamic pressure to {{cvt|570|Pa}} (with speed still in excess of [[Mach number|Mach 24]] and approximately {{cvt|78000|m}} altitude). Automatic roll reversals to control energy dissipation rate and cross range steering were performed at around Mach 18.5 and Mach 9.8.<ref>{{cite book |author=J. |first=James |title=Entry Guidance Training Manual |date=1988 |publisher=NASA JSC Mission Operation Directorate}} {{PD-notice}}</ref> The crew clearly observed the coast of [[California]] as ''Columbia'' crossed it near Big Sur at Mach 7 and {{cvt|41000|m}}. Both the Mach 4.8 and Mach 2.8 roll reversals were automatically initiated and manually completed by John Young. The last RCS jet firing took place at an altitude of {{cvt|17000|m}} — {{cvt|4300|m}} lower than desired (due to a predicted risk of combustion chamber explosion).

Young again took manual control for the remainder of the flight as they went subsonic approaching the Heading Alignment Circle (HAC). A wide left turn was flown to line up with lake bed runway{{nbsp}}23, whilst [[Northrop T-38 Talon|T-38]] "Chase{{nbsp}}1", crewed by astronauts [[Jon McBride]] and [[George Nelson (astronaut)|"Pinky" Nelson]] joined formation. Main gear touch down occurred on runway{{nbsp}}23 at Edwards Air Force Base, at {{cvt|339|km/h}} [[equivalent airspeed]], slightly slower and around {{cvt|800|m}} further down the runway than planned. This was the result of a combination of better than predicted Orbiter lift-to-drag ratios and tail wind. Touch down time was 18:21{{nbsp}}UTC on April 14, 1981.<ref name=scienceksc>{{cite web|url=http://science.ksc.nasa.gov/shuttle/missions/sts-1/mission-sts-1.html|title=STS-1 Overview|publisher=NASA|access-date=August 22, 2010|archive-date=August 23, 2010|archive-url=https://web.archive.org/web/20100823203017/http://science.ksc.nasa.gov/shuttle/missions/sts-1/mission-sts-1.html|url-status=dead}} {{PD-notice}}</ref> As they rolled to a stop, Young remarked over the radio, "This is the world's greatest all electric flying machine. I'll tell you that. That was super!"

''Columbia'' was returned to Kennedy Space Center from California on April 28, 1981, atop the [[Shuttle Carrier Aircraft]]. The 36-orbit, {{cvt|1729348|km}} flight lasted 2{{nbsp}}days, 6{{nbsp}}hours, 20{{nbsp}}minutes and 53{{nbsp}}seconds.<ref name=scienceksc/>

=== Mission anomalies ===
[[File:EM-0084-01.ogg|thumb|upright=1.0|right|STS-1 touches down at [[Edwards Air Force Base]],]]
[[File:Columbia STS-1 training.jpg|thumb|upright=1.0|right|STS-1 crew in Space Shuttle ''Columbia''{{'}}s cabin. This is a view of training in 1980 in the [[Orbiter Processing Facility]].]]

STS-1 was the first orbital test flight of what NASA claims was, at the time, the most complex flying machine ever built.<ref name="NASAOkolski">{{cite web |url=https://history.nasa.gov/sts25th/tech.html|publisher=NASA|title=Shuttle Technology|first=Gabriel|last=Okolski}}</ref> Roughly 70 anomalies were observed during and after the flight, owing to the many components and systems that could not otherwise be adequately tested. These included:

* Similar to the [[Apollo 4|first Saturn V launch]] in 1967, engineers underestimated the amount of noise and vibration produced by the Space Shuttle.<ref name=drop/> Shock waves from the SRB thrust were deflected up into the orbiter's tail section, which flexed the wing flaps and bent several fuel tank supports; Columbia could have had trouble landing if the flaps had been damaged.<ref>{{cite news |title=Cushioning System Tested for Space Shuttle |url=https://www.nytimes.com/1981/09/18/us/cushioning-system-tested-for-space-shuttle.html |work=The New York Times |issue=45075 |volume= 131|date=18 September 1981 |archive-url= https://web.archive.org/web/20180125053119/https://www.nytimes.com/1981/09/18/us/cushioning-system-tested-for-space-shuttle.html |archive-date=25 January 2018}}</ref> An improved [[sound suppression system]] was later installed in LC-39A to damp vibrations.<ref name=drop>{{cite web |url=http://quest.nasa.gov/qna/questions/FAQ_Shuttle_Launch.htm|title=FAQ: Why do you drop water under the shuttle as the engines start?|publisher=NASA|date=January 5, 1999|url-status=dead|archive-url=https://web.archive.org/web/20130515113630/http://quest.nasa.gov/qna/questions/FAQ_Shuttle_Launch.htm|archive-date=May 15, 2013}} {{PD-notice}}</ref>
* Pilot Crippen reported that, throughout the first stage of the launch up to SRB separation, he saw "white stuff" coming off the External Tank and splattering the windows, which was probably the white paint covering the External Tank's thermal foam.<ref name="STS-1 Technical Crew Debriefing page 4-4"/>
* The astronauts' on-orbit visual inspection showed significant damage to the thermal protection tiles on the [[Orbital Maneuvering System|OMS/RCS]] pods at the orbiter's aft end, and John Young reported that two tiles on the nose looked like someone had taken "big bites out of them".<ref name="STS-1 Technical Crew Debriefing page 4-4">STS-1 Technical Crew Debriefing, page 4-4</ref> The [[United States Air Force|U.S. Air Force]] also photographed the orbiter's tiles using a secret KH-11 KENNEN reconnaissance satellite controlled by [[Blue Cube]]. Only the prime and backup crews and a few other NASA employees were aware of this. Young and Crippen were instructed to perform maneuvers to align ''Columbia'' so that the KH-11 could photograph it; because of the preplanned required trajectory, the launch window was far narrower than the publicized six hours.<ref name="white20170412">{{Cite magazine |last=White |first=Rowland |date=2017-04-12 |title=The Spysat and the Shuttle |url=https://www.smithsonianmag.com/air-space-magazine/spysat-and-shuttle-180962872/ |access-date=2024-12-02 |magazine=Air & Space |language=en}}</ref> Images obtained confirmed that damage to ''Columbia'' was not serious.<ref>{{cite web|url=http://www.thespacereview.com/article/3219/1|title=The Space Review: Passing in silence, passing in shadows|website=thespacereview.com}}</ref><ref name="king19810413">{{cite news |url=https://news.google.com/newspapers?id=4rRkAAAAIBAJ&pg=5544%2C1256886|title=NASA says missing tiles no threat to shuttle|newspaper=The Madison Courier|date=April 13, 1981|agency=Associated Press|access-date=January 22, 2013|author=King, James R.}}</ref> Post-flight inspection of ''Columbia'' confirmed that approximately 16 undensified tiles near the OMS pod had been lost during ascent.<ref name=STS-1-AR>{{cite news|url=http://www.jsc.nasa.gov/news/columbia/anomaly/STS1.pdf|title=STS-1 Anomaly Report|date=February 27, 2003|publisher=NASA|access-date=July 14, 2006|archive-url=https://web.archive.org/web/20061007035617/http://www.jsc.nasa.gov/news/columbia/anomaly/STS1.pdf|archive-date=October 7, 2006|url-status=dead}} {{PD-notice}}</ref>
* ''Columbia'''s aerodynamics at high [[Mach number]]s during reentry were found to differ significantly in some respects from those estimated in pre-flight testing. A misprediction of the [[Atmospheric reentry#Real (equilibrium) gas model|location of the center of pressure]] (due to using an [[ideal gas]] model instead of a [[real gas]] model) caused the computer to have to extend the body flap by sixteen degrees rather than the expected eight or nine. The first roll maneuver resulted in lateral and directional oscillations during which side slip angles of up to 4° were reached, twice as high as predicted.<ref name=STS-1-AR/><ref>{{cite web|url=https://docs.google.com/viewer?a=v&q=cache:4E51uFAP7IQJ:ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940006365_1994006365.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESjwyAKkS0Wa0VG5mRVHma6eLMmiDlY0K-rMbA2v4A9nbj4mp-3H5Sulcz4xbKV7nHIurn6w8bqFjEgJpKcRkTUZeJP7GAmPB36OxGpaJCNtFDmDaRwsgtmH5z1XpHp6OGHFGuco&sig=AHIEtbTZaunOq2H9MFtGoFCgmN6sMxN0Jw|title=Space Shuttle Hypersonic Aerodynamic and Aerothermodynamic Flight Research and the Comparison to Ground Test Results|first1=Kenneth|last1=Iliff|first2=Mary|last2=Shafer|pages=5–6|date=June 1993|access-date=February 16, 2013|publisher=Google Docs}} {{PD-notice}}</ref> Analysis attributed the cause to unexpectedly large rolling moments due to yaw RCS jet firings. During the early stages of entry, orbiter roll control is achieved as a result of [[Slip (aerodynamics)|sideslip]] modulation.
* The orbiter's heat shield was damaged when an [[overpressure]] wave from the [[Space Shuttle Solid Rocket Booster|solid rocket booster]] caused a forward RCS oxidizer strut to fail.<ref name=STS-1-AR/>
* The same overpressure wave also forced the [[orbiter body flap]] – an extension on the orbiter's underbelly that helps to control pitch during reentry – into an angle well beyond the point where cracking or rupture of its [[hydraulic]] system would have been expected. Such damage would have made a controlled descent impossible, with John Young later admitting that had the crew known about this, they would have flown the shuttle up to a safe altitude and ejected, causing ''Columbia'' to be lost on the first flight. Young had reservations about ejection as a safe abort mode due to the fact that the SRBs were firing throughout the ejection window, but he justified taking this risk because, in his view, an inoperative body flap would have made landing and descent "extremely difficult if not impossible."<ref name="boyle">{{cite news|author=Boyle, Alan (quoting a recollection of James Oberg)|title=Cosmic Log: April 8-14, 2006|url=https://www.nbcnews.com/id/wbna12243173|access-date=January 8, 2018|agency=NBC News|quote=After the flight, mission commander John Young was shown those videos. His reaction was severe. 'Had I known the body flap had been deflected so far off position', he told associates, 'I'd have concluded the hydraulic lines had been ruptured and the system was inoperative'. Without a working body flap, a controlled descent and landing would have been extremely difficult if not impossible. The pitch control thrusters might or might not have been enough to provide control. The shuttle might have tumbled out of control and disintegrated at very high speed and altitude ... 'I'd have ridden the vehicle up to a safe altitude', he later stated, 'and while still in the ejection envelope [the range of speed and altitude for safely firing the ejection seats] I'd have pulled the ring'.}}</ref><ref>{{cite web|url=http://www.collectspace.com/news/news-041006a.html|title=L+25 Years: STS-1's Young and Crippen |publisher=collectSPACE}}</ref>
* The strike plate next to the forward latch of ''Columbia''{{'}}s [[external tank]] door was melted and distorted due to excess heat exposure during reentry. This heat was attributed to an improperly installed tile adjacent to the plate.<ref name=STS-1-AR/>
* During remarks at a 2003 gathering, John Young stated that a protruding tile gap filler ducted hot gas into the right main landing gear well, which caused significant damage, including the buckling of the landing gear door.<ref>{{cite web |author=Foust |first=Jeff |date=April 14, 2003 |title=John Young's shuttle secret |url=http://www.thespacereview.com/article/15/1 |access-date=August 22, 2010 |publisher=Space Review}}</ref> He said that neither he nor Crippen were told about this incident and he was not aware that it had happened until reading the postflight mission report for STS-1, also adding that the gas leak was noted in the report, but not the buckling of the landing door. (The buckling of the door is in fact in the anomaly report, anomaly STS-1-V-49).<ref name=STS-1-AR/>

Despite these problems, the STS-1 mission was completed successfully, and in most respects ''Columbia'' performed optimally. After some modifications to the Shuttle and to the launch and reentry procedures,<ref>{{cite book |author=A. |first=Cohen |title=STS-1 Orbiter Final Mission Report |date=1981 |publisher=NASA JSC Mission Evaluation Team |pages=152–237}} {{PD-notice}}</ref> ''Columbia'' flew the next four Shuttle missions.