Editing Project Mercury (section)

===Development and production===
[[File:Technicians working in the McDonnell White Room on the Mercury-crop.jpg|thumb|upright|Spacecraft production in clean room at [[McDonnell Aircraft]], St. Louis, 1960]]
The Mercury spacecraft design was modified three times by NASA between 1958 and 1959.{{sfn|Catchpole|2001|p=152}} After bidding by potential contractors had been completed, NASA selected the design submitted as "C" in November 1958.{{sfn|Catchpole|2001|p=153}} After it failed a test flight in July 1959, a final configuration, "D", emerged.{{sfn|Catchpole|2001|p=159}} The heat shield shape had been developed earlier in the 1950s through experiments with ballistic missiles, which had shown a blunt profile would create a shock wave that would lead most of the heat around the spacecraft.{{sfn|Catchpole|2001|p=149}} To further protect against heat, either a [[heat sink]], or an ablative material, could be added to the shield.{{sfn| Alexander & al.|1966|p=63}} The heat sink would remove heat by the flow of the air inside the shock wave, whereas the ablative heat shield would remove heat by a controlled evaporation of the ablative material.{{sfn| Alexander & al.|1966|p=64}} After uncrewed tests, the latter was chosen for crewed flights.{{sfn| Alexander & al.|1966|p=206}} Apart from the capsule design, a [[rocket plane]] similar to the existing [[X-15]] was considered.{{sfn| Alexander & al.|1966|pp=78–80}} This approach was still too far from being able to make a spaceflight, and was consequently dropped.{{sfn| Alexander & al.|1966|p=72}}{{refn|group=n|The rocket plane approach to human space flight was pursued by the Air Force with their [[Boeing X-20 Dyna-Soar|Dyna-Soar]] project, which was canceled in 1963.{{sfn|Catchpole|2001|pp=425, 428}} Toward the end of the 1960s, NASA began the development of a reusable space plane, which was ultimately developed into the [[Space Shuttle]] program.<ref>{{cite web|title=Introduction to future launch vehicle plans [1963–2001]. 3.The Space Shuttle (1968–72)|url=http://www.pmview.com/spaceodysseytwo/spacelvs/sld001.htm|access-date=3 February 2014}}</ref> The first rocket plane to enter space was an X-15 in 1963.<ref>{{cite web|last1=Garber|first1=Steve|title=X – 15 Hypersonic Research at the Edge of Space|url=https://history.nasa.gov/x15/cover.html|website=NASA History Homepage|publisher=NASA|access-date=18 July 2015}}</ref>}} The heat shield and the stability of the spacecraft were tested in [[supersonic wind tunnel|wind tunnels]],{{sfn|Alexander & al.|1966|p=88}} and later in flight.{{sfn|Catchpole|2001|p=229}} The launch escape system was developed through uncrewed flights.{{sfn|Catchpole|2001|p=196}} During a period of problems with development of the landing parachutes, alternative landing systems such as the [[Rogallo wing|Rogallo glider wing]] were considered, but ultimately scrapped.{{sfn| Alexander & al.|1966|p=198}}

The spacecraft were produced at [[McDonnell Aircraft]], [[St. Louis, Missouri|St. Louis]], Missouri, in clean rooms and tested in vacuum chambers at the McDonnell plant.{{sfn|Catchpole|2001|pp=132, 159}} The spacecraft had close to 600 subcontractors, such as [[Garrett AiResearch]] which built the spacecraft's environmental control system.{{sfn| Alexander & al.|1966|p=137}}{{sfn|Catchpole|2001|p=138}} Final quality control and preparations of the spacecraft were made at Hangar S at Cape Canaveral.{{sfn|Catchpole|2001|pp=184–188}}{{refn|Test and rework of Mercury-Redstone 2 at the Hangar required 110 days.{{sfn|Alexander & al.|1966|p=310}} Hangar S was also the place where the chimpanzees were trained.{{sfn|Alexander & al.|1966|p=312}}|group=n}} NASA ordered 20 production spacecraft, numbered 1 through 20.{{sfn|Alexander & al.|1966|p=137}} Five of the 20, Nos. 10, 12, 15, 17, and 19, were not flown.{{sfn|Grimwood|1963|pp=235–238}} Spacecraft No. 3 and No. 4 were destroyed during uncrewed test flights.{{sfn|Grimwood|1963|pp=235–238}} Spacecraft No. 11 sank and was recovered from the bottom of the Atlantic Ocean after 38 years.{{sfn|Grimwood|1963|pp=235–238}}{{sfn|Catchpole|2001|pp=402–405}} Some spacecraft were modified after initial production (refurbished after launch abort, modified for longer missions, etc.).{{refn|They received a letter designation after their number, ''e.g.'', 2B, 15B.{{sfn|Grimwood|1963|pp=216–218}} Some were modified twice: for example, spacecraft 15 became 15A and then 15B.{{sfn|Grimwood|1963|p=149}}|group=n}} A number of Mercury [[Boilerplate (spaceflight)|boilerplate spacecraft]] (made from non-flight materials or lacking production spacecraft systems) were also made by NASA and McDonnell.{{sfn|Alexander & al.|1966|pp=126 & 138}} They were designed and used to test spacecraft recovery systems and the escape tower.{{sfn|Alexander & al.|1966|pp=96, 105}} McDonnell also built the spacecraft simulators used by the astronauts during training,{{sfn|Catchpole|2001|p=107}} and adopted the motto "First Free Man in Space".<ref name="logo_history">{{citation |url= http://www.mdc.com/version2/history/logo.htm |publisher= McDonnell Douglas |title= McDonnell Douglas Logo History |access-date= 29 November 2020 |archive-url= https://web.archive.org/web/19970605044807/http://www.mdc.com/version2/history/logo.htm |archive-date= 5 June 1997 |url-status= dead }}</ref>

<gallery mode="packed">
Heatshield-test3.jpg|[[Shadowgraph]] of the reentry [[shock wave]] simulated in a [[supersonic wind tunnel|wind tunnel]], 1957
Mercury-design.png|Evolution of capsule design, 1958–59
Mercury Space Capsule-wind-tunnel.jpg|Experiment with boilerplate spacecraft, 1959
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Mercury-project-earth-landing-system-test.png|Drop of boilerplate spacecraft in training of landing and recovery. 56 such qualification tests were made together with tests of individual steps of the system.{{sfn|Catchpole|2001|pp=172-173}}
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