Red Bull Stratos Science Team Reveals How Felix Baumgartner Will Try to Achieve Supersonic Freefall -- and What They Hope to Learn

Today the Red Bull Stratos science team released the first new information available since Felix Baumgartner's mission to the edge of space was announced to the public on January 22, 2010. The detail offered provides deeper insight into how and why Baumgartner hopes to become the first person ever to "go supersonic" in freefall as he attempts a skydive from a stratospheric balloon.

Potential Hazards

The speed of sound varies according to altitude and temperature. The Red Bull Stratos science team estimates that -- after only about 35 seconds of freefall -- Baumgartner will break through the sound barrier and "catch up with" the speed of sound, which is likely to be about 690 miles per hour at the predicted altitude of 100,000 feet. Known hazards at such altitudes include temperatures well below zero; an environment with too little oxygen to sustain human life; the tendency to spin uncontrollably (to the point of unconsciousness or worse); and air pressure so low that without a pressure suit blood is said to "boil" with life-threatening vapor bubbles. Unpredictable factors compounding those dangers include sudden changes in air pressure and resulting instability in the "transonic" zone (speeds approaching supersonic velocity), which in the mid-twentieth century caused aircraft to go out of control or break up and resulted in the concept of a sound "barrier." Of particular interest is the "shock-shock interaction," a condition in which shock waves collide and create a reaction not unlike an explosion's blast wave.

"Our biggest concern is that we don't know how a human unencumbered by an aircraft is going to transition through this," says Dr. Jonathan Clark, the mission's Medical Director. "But it's also exactly what we're hoping to learn, for the benefit of future space flights."

Einar Enevoldson, who set eight world records during his own career as a research pilot and is now the Red Bull Stratos Mission Analyst and Safety Advisor, adds, "One of our primary goals is to determine a test and safety plan that will protect Felix Baumgartner from the effects of extreme pressures or temperatures, yet will result in a very valuable step toward predicting the character of these effects in potential future higher and faster jumps."

Mission Strategies to Achieve Supersonic Flight in Freefall

The Red Bull Stratos mission plan to achieve supersonic flight in freefall considers a wide range of factors, including "terminal velocity" (a concept familiar to skydivers at moderate altitudes), which can be explained in an elementary fashion as the speed at which the wind resistance on a jumper equals his or her weight, halting further acceleration. Jumping from an altitude of 120,000 feet, in very thin air (less than 1 percent of the density on the ground), the level of wind resistance on Baumgartner should be extremely small, and calculations indicate that if he can reduce drag by streamlining his body position, attaining the speed of sound is possible. Strategies to aid and protect him in the effort include:

- Graduated, multi-stage test program: Besides working in wind tunnels and low-pressure chambers, Baumgartner will jump in his pressure suit from successively higher outdoor altitudes, allowing him and analysts on the mission team to assess the effect of the surrounding conditions -- and his body's reactions -- to make necessary adjustments.

- Choreographed step-off: For the first 25 to 30 seconds of his flight, the thin air will offer Baumgartner so little resistance that he will not be able to adjust his position using air flow. This means he must "choreograph" his movements to step off the capsule in an optimal position, an endeavor complicated by his bulky full-pressure suit and by the fact that the capsule is not fixed rigidly to the balloon and thus can react to his motion. Part of Baumgartner's training is dedicated to honing this "choreography."

- Full-pressure suit and helmet: Baumgartner's full-pressure ("space") suit and helmet are designed to provide oxygen, protection from the extreme cold, and also a certain amount of rigidity and support in the potentially difficult transonic zone as he approaches the speed of sound. This state-of-the-art gear incorporates added features to afford Baumgartner advantages

- hence protection

- never before available.

- Drogue parachute: Although he may not need or use it, a special "drogue" parachute has been developed and tested for deployment even at the extreme of supersonic speed. This drogue chute will be available to stabilize Baumgartner if necessary to avert the potentially fatal tendency for falling objects to spin uncontrollably at high altitudes.

Clark comments, "What we're counting on is that, while the high altitude presents many challenges, the air will also be rarified, so shock waves won't have the same detrimental, concussive effect as they would down low. But ultimately, this mission is a test flight, so we'll know a lot more afterward than we'll know beforehand." He adds, "We expect the unexpected."