User:Andrew Gray/NASA naming conventions

NASA, the National Aeronautics and Space Administration of the United States, has used several different naming conventions to refer to its manned spaceflights. Many of these are somewhat confusing, and occasionally several have been in use simultaneously.

Mercury
The earliest manned spaceflights were those of the Mercury program, which used a manned capsule on top of a rocket. The capsule itself was "Mercury"; the rockets were, at varying stages of the program, Little Joe (test suborbital flights only), Redstone and Atlas (for manned flights).

The missions were referred to by the program name plus the name of the booster, with a number - so the third flight using a Redstone booster would be "Mercury-Redstone 3", or MR-3, whilst the fifth Atlas mission would be "Mercury-Atlas 5" or MR-5. Capsules were individually numbered, for example as "Mercury #7"; the boosters were likewise numbered, but again this was for internal administrative purposes and neither serial number was reflected in the mission name.

However, these flight numbers were overshadowed by the call signs of the individual flights; when Alan Shepard flew Mercury-Redstone 3 in capsule number 7, on booster #7, he used the call sign Freedom 7, establishing a pattern that remained in place. Future Mercury flights would adopt a call-sign, appended with "7" - Liberty Bell 7 (MR-4), for example, or Sigma 7 (MA-8)

Gemini
The official numbering system used for the Gemini program was reminiscent of that used for Mercury, but was simplified by the fact that only one type of launch vehicle was used. All the missions were numbered GT-#, from flight 1 through to 12; GT stood for Gemini-Titan. (Only flights 3-12 were manned).

However, NASA instituted a simpler public numbering system; press releases referred to "Gemini 4" rather than "GT-4", for example. These numbers were consistent with the GT- numbering, which prevented confusion.

There were small glitches in the sequence; Gemini 6 was unable to be flown, as the booster stage it was intended to dock with failed to reach orbit. Another mission plan was substituted (involving a rendevous with Gemini 7), and the new mission flown as Gemini 6A. Likewise, the docking target for Gemini 9 was unavailable due to launch problems; a replacement was launched, and the mission modified to suit it. The modified mission was known as Gemini 9A. These changes ensured that planning documents and other material did not get confused between the old and new mission plans.

Apollo
By the time of the Apollo program, the public numbering system was well understood - generally, only technical documentation referred to the manned flights as anything other than "Apollo #".

However, there was still a formal numbering system; this used SA-#, or AS-#, standing for "Saturn-Apollo" or "Apollo-Saturn". The numbers were the same for each; different NASA centres used different prefixes. (As a general rule, AS- was used when discussing the mission, SA- when discussing the launch)

The numbers, however, were complex; the manned Apollo flights used two different launch vehicles, the Saturn IB and the Saturn V. As both of these had the same name, a way was needed to distinguish