Challenger. It guarnteed that I would not make it in to space in my lifetime, a dream I had held since my dad let me stay home from school to watch every single Mercury, Gemini, and Apollo launch, and recovery.
If, I may ask, how old are you?
I ask because I read somewhere that Richard Branson of Virgin Air is going to have some sort of passenger aircraft - within 10 years - to go into space (but at the tune of $25,000 per passenger). There’s still hope.