So what's with this Shuttle mission numbering scheme? It doesn't seem to make sense, does it? If you've studied Shuttle history, you've noticed that the missions back at the beginning of the program were numbered sequentially, starting with STS-1. Up through STS-9, everything was going along okay, but then something happened. There was STS-41B, then several missions with this strange numbering system until STS-51L. Then, it went back to a somewhat recognizable numbering scheme starting with STS-26.Why?

Originally, there were two planned launch sites for the Shuttle: Kennedy Space Center (KSC) on the east coast in Florida, and Vandenburg Air Force Base (VAFB) on the west coast in California. There needed to be a way to quickly tell when and where a given Shuttle mission was scheduled to launch. Using the first mission with the "new" numbering system, STS-41B, as our guide, we can figure out all the information we need from the "41B" part of the mission number. The first digit, 4, was to designate the last digit of the fiscal year in which that particular mission was originally scheduled to launch. (Just to complicate things, remember that the fiscal year starts on October 1!) Thus, STS-41B was initially scheduled to launch in 1984. The second digit, 1, designated which launch site was to be used, 1 for KSC, and 2 for VAFB. Therefore, STS-41B was scheduled to launch from KSC. Finally, the third character denoted the sequential position the launch occupied in the launch schedule: A = 1, B = 2, C = 3, and so on. So, STS-41B was designated as the second launch of the fiscal year. So, there you have it. STS-41B was originally scheduled to be the second Shuttle launch of fiscal 1984, from KSC. The launch occurred on February 3, 1984. STS-9, the previous mission, had launched on November 28, 1983, which made it the first launch of fiscal 1984. Still with us?

Then came STS-51L. After the accident, the new numbering system was abandoned, and we went back to numbering Shuttle missions sequentially, the way we had originally done. We also abandoned the idea of launching from VAFB. STS-51L had been the 25th Shuttle launch of the program, so STS-26 was chosen to designate the Return to Flight launch.

But, you may notice, the missions still don't seem to be numbered sequentially! What's going on? If you've run the S0007 simulation, you've noticed that launches don't always go when they've been scheduled to lift off. Between weather delays, technical glitches, and a host of other issues, missions are often postponed, schedules are shuffled, and we end up with flights going "out of order". Even rocket science has problems that can't always be resolved neatly!

The border of this page is made up of all the mission patches for all the Shuttle launches that have taken place through STS-107. Each patch is a hot link to the NASA information pages on each launch. Just click on any patch, and you'll go to a page where you can learn more details about that particular mission.