In the 1950s, the US Air Force was worried about the survival of their pilots if forced to eject at high altitude. Tests with dummies didn’t go so well, so they worked on developing a new parachute design that wasn’t so likely to kill its wearer. But eventually, a human being had to test it. That was Project Excelsior: get Joseph Kittinger to jump from progressively higher balloons. Kittiger’s final jump, in 1960, set records that lasted for decades: a 102,800 feet (31,333 m) descent and falling for 4:36 minutes before opening his parachute. He came close to the speed of sound, but didn’t quite make it (614 miles per hour or 988 km/h). (It’s worth reading the linked references: Kittiger’s jumps were incredibly risky, and nearly failed.)

Several of those records were broken yesterday. Felix Baumgartner stepped out of a balloon at 128,100 feet (39,044 m), and spent 4:20 in free fall (Kittinger still holds the time record). He hit 833.9 miles per hour (1342 kph) on his way down, exceeding the local speed of sound: it gets complicated because the speed of sound varies with altitude, mostly due to changes in atmospheric temperature. Kittinger was part of Baumgartner’s team.

Dr. Jon Clark was also a member of the prep team. Dr. Clark, a former NASA space shuttle crew surgeon, has become increasingly interested in high altitude human survival since his wife Laurel Clark died aboard Columbia in 2003. One of the fascinating things about this high-altitude human descent: nobody knew what would happen to the human body when it exceeded the speed of sound.

Since Baumgartner landed safely, fears that he would be battered to death as parts of him went supersonic or subsonic at different times were apparently unfounded. It will be fascinating to see what kind of new scientific and medical insights come from his telemetry. Even with all we know about human physiology and all the places we’ve sent human beings, from the Moon to the bottom of the ocean, there’s still plenty we don’t know.

“Usually when a doctor shows up to a press conference, we’re having a bad day,” said mission medical director Jonathan Clark. The data from Baumgartner’s jump has yet to be fully analyzed, but Clark said the data collected “is going to break incredible new ground.”

Incidentally, the first human creation to break the sound barrier? The bullwhip.

(Thanks to Micah Joel for the idea for this post.)

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