This morning Red Bull athlete Felix baumgartner will attempt to break the speed of sound while free falling back to earth from 120,000 ft. To achieve this altitude, a baloon will carry him to this height. There is so little air that planes can't fly that high, hence the baloon. Obviously this is a very cool event and from my prespective as a physiologist and scientist it is totally fascinating. Here are the factors that should play in to the success of the jump:
Before the flight Felix will be given specially designed low fibre foods. The key is to eat foods that are easily digested and leave no residue inside the body. Any foods or residues will cause some gas as the bacteria in our digestive tract tries to digest the nutrients. This isn't a problem at sea level but at the extreme low pressures of 120,000 ft, the effects of internal gas are magnified and could be very uncomfortable and painful.
Also, for 2 hours before the jump Felix will breathe 100% oxygen. Normally the atmosphere is about 79% nitrogen and 21% oxygen. By breathing pure O2 Felix will be able to eliminate nitrogen from his body. This is cititical as he ascends to jump altitude because the nitrogen would otherwise expand and cause bubbles to be formed in his tissues (think of opening up a can of pop). In diving this is known as the bends.
For the jump itself, Felix will leave the capsule at 120,000 ft as I mentioned. This, arguably, is the edge of space. People consider this zone the edge of space as there is minimal discernible atmosphere or air molecules at this height.
The low air pressure is beneficial for Felix's goals of breaking the sound barrier while falling back to earth - low air pressure means low resistance and therefore high speeds. The speed of sound at sea level is 760 miles per hour and it's 450 miles per hour at 120,000 ft. Calculations by Professor Rhett Allain suggest that Felix will exceed the speed of sound for almost 60 seconds and that at one point he will go faster than 760 miles per hour.
The physical effects of breaking the sound barrier at that height will be minimal. The sonic boom that you may have heard of is caused by shock waves formed ahead of an airplane as the plane approaches then exceeds the speed of sound. Since there are so few air molecules at this height shock waves should be minimal. But of course no one has done this before so we will have to wait to hear what it was like from Mr. Baumgartner after his jump...
The final science piece to this awesome puzzle is the suit that Felix will wear while attempting his jump. It is a pretty amazing engineering feat designed to protect him from the triple threat of temperatures well below freezing, very low pressures that would cause the body fluids to boil should the be exposed and low oxygen. You can check out the suit here.
Here's the video from his 96,000 record setting test jump!