(Reuters) - Austrian skydiver Felix Baumgartner faces a slew of dangers during his attempt to break the altitude record for a freefall jump on Sunday.
Here is a look at some of the risks:
Colliding shock waves, triggered by a human body moving faster than the speed of sound, could hit with the force of an explosion, though the risk of this is much less likely in the stratosphere, where the air is extremely thin.
The low-pressure environment could cause Baumgartner to go into a flat spin. If a spin lasts for too long, he could lose consciousness and injure his eyes, brain and cardiovascular system.
Exposure to vacuum, even for a short period of time, could cause Baumgartner's blood to literally boil. The condition, known as ebullism, causes fluids in the body to turn to gas.
Gas seeping into the body due to a relatively rapid exposure to low pressure can cause decompression sickness, or "the bends."
As pressure decreases, trapped gas in the body can cause ear blockages, dizziness and acute tooth, sinus and gastrointestinal pain. When decompression is sudden, lungs can over-inflate and collapse. A gas bubble in an artery could stop blood flow.
Extremely cold temperatures pose a threat to Baumgartner and his equipment. Excessive heat from the sun is also a risk.
Ultraviolet radiation is more than 100,000 times as strong at 120,000 feet, where Baumgartner plans to begin his jump, as it is at ground level, but Baumgartner should have a very short exposure time.
Wind shear could make Baumgartner nauseous and could destroy his balloon.
A breach in Baumgartner's protective spacesuit or the accidental deployment of a parachute are considered the biggest safety concerns.
(Source: Red Bull Stratos)
(Reporting by Irene Klotz; Editing by David Brunnstrom and Todd Eastham)