Former NASA astronaut Jeffrey A. Hoffman, spoke with Business Insider at BBC FUTURE's World-Changing Ideas Summit, about what it takes to be an astronaut.
Between 1985 and 1996, Hoffman completed five spaceflight missions, flew aboard four of NASA's five space shuttles, and logged over 1,211 hours in space.
When asked what his scariest experience was during all those missions, he noted:
"I never really got scared," Hoffman said. "There's lots of things that can happen that you can't do anything about, so why worry?"
When astronauts climb aboard a spacecraft, they're consciously strapping themselves to, what is in every sense of the word, a rocket. And they know it.
"If sitting down on top of a loaded rocket causes you emotional stress, maybe you're not in the right profession," said Hoffman, who retired from NASA in 1997 and is now a professor of aeronautics and astronautics at MIT.
Hoffman rode his first space shuttle, "Discovery," into space in 1985 — the year before the Challenger disaster.
According to retired Canadian astronaut, Chris Hadfield, during a TED talk in Vancouver earlier this year, the odds of catastrophic failure in 1979 were 1 in 38. The odds were likely similarly bleak when Hoffman fist entered space.