Parachuting from 20 miles altitude

[Rothiemurchus]

The guy who parachuted from 20 miles up in the atmosphere - did he heat up significantly through friction with the air and how fast was he moving?

 

[mgb_phys]

At 20mi the air is rather thin. I imagine the limit would be the speed of sound - which is rather lower at 20mi than at sea level.
As you reach denser lower levels of the atmosphere you will slow down as you encounter more friction - if you designed the aerodynamics correctly you should be able to slow at a rate so that you don't heat too much. In fact with a temperature n the stratosphere of <-50degC, cooling would be more of a problem.
I think the USAF record only used a stabiliser parachute to prevent spin - it relied on drag on the body to slow down to a point that the main chute could open safely.

I think the experiment that

 

[russ_watters]

Good answer. Here's the guy, Joseph Kettinger: http://www.centennialofflight.gov/essay/Dictionary/kittinger/DI29.htm

The third flight, on August 16, 1960, broke records. The Excelsior III climbed to 102,800 feet (31,333 meters), and on his descent, Kittinger freefell at speeds up to 614 miles per hour, approaching the speed of sound without the protection of an aircraft or space vehicle and experiencing temperatures as low as minus 94 degrees Fahrenheit (minus 70 degrees Celsius).

No, frictional heating is not a significant issue here.

 

[Mk]

Instead of frictional heating, heating up from (re)entry into the Earth's atmosphere is from ram pressure.
http://en.wikipedia.org/wiki/Ram_pressure

 

[mgb_phys]

Interesting point - I suppose you could argue there is no such thing as air-friction. It is only the momentum of air molecules hitting you in the direction you are travelling.