NASA has built six different space shuttles.
Challenger, Enterprise, Columbia, Discovery, Atlantis, and Endeavor.
Only 5 of them were actually space worthy.
4 of them are still around today in space museums, the Enterprise, Discovery, Atlantis and Endeavor.
Challenger exploded after launch, killing all seven on board.
The Columbia also exploded during reentry, killing all seven on board.
Hope this helps :)
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