STS-41-B was the tenth NASA Space Shuttle mission and the fourth flight of the Space Shuttle Challenger. It launched on February 3, 1984, and landed on February 11 after deploying two communications satellites. It was also notable for including the first untethered spacewalk.
Following STS-9, the flight numbering system for the Space Shuttle program was changed. Thus, the next flight, instead of being designated STS-11, became STS-41-B; the original successor to STS-9, STS-10, was cancelled due to payload delays. This was done due to fears that a flight numbered STS-13 could suffer a mishap as Apollo 13 did.