Editing Space Shuttle (section)

=== Development ===
[[File:566175main columbia-opf.jpg|thumb|right|alt=The Space Shuttle Columbia under construction|[[Space Shuttle Columbia|''Columbia'']] undergoing installation of its ceramic tiles]]

On June 4, 1974, Rockwell began construction on the first orbiter, OV-101, dubbed Constitution, later to be renamed [[Space Shuttle Enterprise|''Enterprise'']]. ''Enterprise'' was designed as a test vehicle, and did not include engines or heat shielding. Construction was completed on September 17, 1976, and ''Enterprise'' was moved to the [[Edwards Air Force Base]] to begin testing.<ref name="dev_space_shuttle" />{{rp|173}}<ref name="enterprise_overview">{{cite web |last= Howell |first= Elizabeth |title= Enterprise: The Test Shuttle |publisher= Space.com |date= October 9, 2012 |url= https://www.space.com/17983-space-shuttle-enterprise.html |access-date= April 24, 2019 |archive-date= August 6, 2020 |archive-url= https://web.archive.org/web/20200806144504/https://www.space.com/17983-space-shuttle-enterprise.html |url-status= live}}</ref> Rockwell constructed the [[MPTA-098|Main Propulsion Test Article (MPTA)-098]], which was a structural truss mounted to the ET with three RS-25 engines attached. It was tested at the [[Stennis Space Center|National Space Technology Laboratory]] (NSTL) to ensure that the engines could safely run through the launch profile.<ref name=jenkins2016 />{{rp|II-163}} Rockwell conducted mechanical and thermal stress tests on Structural Test Article (STA)-099 to determine the effects of aerodynamic and thermal stresses during launch and reentry.<ref name=jenkins2016 />{{rp|I-415}}

The beginning of the development of the RS-25 Space Shuttle Main Engine was delayed for nine months while [[Pratt & Whitney]] challenged the contract that had been issued to Rocketdyne. The first engine was completed in March 1975, after issues with developing the first throttleable, reusable engine. During engine testing, the RS-25 experienced multiple nozzle failures, as well as broken turbine blades. Despite the problems during testing, NASA ordered the nine RS-25 engines needed for its three orbiters under construction in May 1978.<ref name=dev_space_shuttle />{{rp|174–175}}

NASA experienced significant delays in the development of the Space Shuttle's [[Space Shuttle thermal protection system|thermal protection system]]. Previous NASA spacecraft had used [[Atmospheric entry#Ablative|ablative]] heat shields, but those could not be reused. NASA chose to use ceramic tiles for thermal protection, as the shuttle could then be constructed of lightweight [[aluminum]], and the tiles could be individually replaced as needed. Construction began on [[Space Shuttle Columbia|''Columbia'']] on March 27, 1975, and it was delivered to the KSC on March 25, 1979.<ref name=dev_space_shuttle />{{rp|175–177}} At the time of its arrival at the KSC, ''Columbia'' still had 6,000 of its 30,000 tiles remaining to be installed. However, many of the tiles that had been originally installed had to be replaced, requiring two years of installation before ''Columbia'' could fly.<ref name=shuttle_manual />{{rp|46–48}}

On January 5, 1979, NASA commissioned a second orbiter. Later that month, Rockwell began converting STA-099 to OV-099, later named [[Space Shuttle Challenger|''Challenger'']]. On January 29, 1979, NASA ordered two additional orbiters, OV-103 and OV-104, which were named [[Space Shuttle Discovery|''Discovery'']] and [[Space Shuttle Atlantis|''Atlantis'']]. Construction of OV-105, later named [[Space Shuttle Endeavour|''Endeavour'']], began in February 1982, but NASA decided to limit the Space Shuttle fleet to four orbiters in 1983. After the [[Space Shuttle Challenger disaster|loss of ''Challenger'']], NASA resumed production of ''Endeavour'' in September 1987.<ref name=shuttle_manual />{{rp|52–53}}