STS-
Mission
Original archive entry. The text, images and links below are kept as they were written.
The baffling shuttle numbering system originated with a desire not to fly an 'unlucky' STS-13 mission.
The first nine shuttle flights were numbered STS-1, -2, -3 etc. Then NASA noticed that they would end up with an STS-13, and after what happened with Apollo 13, they didn't want that. So someone thought up a complex and baffling system. Each flight would have a first digit representing the fiscal year it was expected to launch (4 = 1984; 5=1985; etc). The second digit would represent whether it would launch from Cape Canaveral or Vandenberg (1=Kennedy Space Center; 2=Vandenberg). The final letter would represent the originally planned order of the flight within the calendar year (A=first, B=second, etc). Naturally this numbering quickly got out of sequence as Vandenberg launches were delayed (and finally canceled) and various payloads slipped from month to month or year to year. It baffled everybody. After Challenger blew up on STS-51L, with STS-13 safely behind and the worst thing that could have happened having come to pass, NASA went back to the straight number sequence, beginning with STS-26. At the low post-Challenger flight rate, these stayed pretty much in consecutive order, but occasionally delays in payloads or scheduling changes would result in flights being flown out of order.