The 120,000-Foot Leap
Can space-diver Felix Baumgartner break the sound barrier without breaking his neck?
- By Mark Betancourt
- Air & Space magazine, July 2012
(Page 4 of 5)
Yes, that’s possible. Because the air is so much thinner in the stratosphere, the speed known as terminal velocity—the point at which air friction cancels out gravitational acceleration—is much higher there than it is near the ground. The Stratos team reckons Felix will reach at least 690 mph, somewhere near the 105,000-foot mark. Adjusting for altitude and temperature, that should be just fast enough to break the sound barrier.
According to the Stratos team, as a shock wave builds up on his helmet, Baumgartner might feel a little vibration near his head. Then, as he reaches and surpasses the speed of sound, the sensation will move instantly to his feet and disappear until he slows and goes subsonic again, at which point he might feel another vibration. That’s if everything goes well.
What happens if things don’t go well is the only genuine mystery in this venture. Fifty-two years ago, Kittinger showed that a stratospheric jump was possible, and there should be no real surprises about the leap itself. But no one has ever crossed the sound barrier quite this way before. There’s one possibility in particular that interests Clark, something called shock-shock interaction.
When a fighter goes supersonic, separate shock waves originate from the nose of the airplane and from its other surfaces. If the shock waves intersect, they intensify enough to generate heat. A supersonic aircraft has to be designed to divert those shock waves away from one another, otherwise the heat and force of the interaction could damage or even destroy the airplane.
In theory, something similar could happen to Baumgartner when he reaches Mach 1, as shock waves bounce off of differently angled parts of his body. Clark’s thinking, though, is that because the air up there will be very thin, the shock waves will be weak. And by gradually easing across the threshold, Baumgartner will prevent any serious danger of shock-shock interaction. So for Clark, it’s more a matter of curiosity than real worry.
Clark has a personal reason for working to make Baumgartner, and future astronauts, safer. His wife, Laurel Clark, was one of the crew members lost in the 2003 Columbia accident. But unlike the space shuttle, which broke up going 13,000 mph, Baumgartner will be falling in a stable position at a comfortable Mach 1. The Stratos team suspects he might not notice when he hits the speed of sound.
In fact, during the first few seconds after he jumps from his capsule above 120,000 feet, he won’t even feel like he’s falling. Air resistance will be so minimal that it will seem like he’s simply floating above Earth. As he gains speed and hits denser atmosphere, wind blast forces will kick in and Baumgartner will be on his home skydiving turf, pulling the chute at around 5,000 feet, where there’s enough air for it to fully deploy. By then, it will feel much like a typical skydive, except it will have lasted longer and the view will have been better.
In may 1966, Three months after his failed second try, Nick Piantanida took one more shot at breaking Kittinger’s record. The oxygen hose disconnection problem had been resolved, and he considered the third attempt to be a shoe-in. On May 1, he lounged near his gondola awaiting takeoff, then kissed his wife before closing his helmet visor and sealing his suit. He climbed into the gondola while the balloon filled, then took off. Things went smoothly until he reached around 57,000 feet. At that point, roughly an hour into his flight, Piantanida’s team heard a whooshing sound over the radio. They asked him to respond, but he could only get out part of the word “emergency.”