CAPE CANAVERAL, Fla. -- His blood could boil. His lungs could overinflate. The vessels in his brain could burst. His eyes could hemorrhage.
And, yes, he could break his neck while jumping from a mind-boggling altitude of 23 miles.
But the risk of a gruesome death has never stopped "Fearless Felix" Baumgartner in all his years of skydiving and skyscraper leaping, and it's not about to now.
Next Monday over New Mexico, he will attempt the highest, fastest free fall in history and try to become the first skydiver to break the sound barrier.
"So many unknowns," Baumgartner says, "but we have solutions to survive."
The 43-year-old former military parachutist from Austria is hoping to reach 690 mph, or Mach 1, after leaping from his balloon-hoisted capsule over the desert near Roswell.
He will have only a pressurized suit and helmet for protection as he tries to go supersonic 65 years after Chuck Yeager, flying an experimental rocket plane, became the first human to go faster than the speed of sound.
Doctors, engineers and others on Baumgartner's Red Bull-sponsored team have spent as much as five years studying the risks and believe they have done everything possible to bring him back alive. He has tested out his suit and capsule in two dress rehearsals, jumping from 15 miles in March and 18 miles in July.
Baumgartner will be more than three times higher than the cruising altitude of jetliners when he hops, bunny-style, out of the capsule and into a near-vacuum where there is barely any oxygen and less than 1 percent of the air pressure on Earth.
If all goes well, he will reach the speed of sound in about half a minute at an altitude of around 100,000 feet. Then he will start to slow as the atmosphere gets denser, and after five minutes of free fall, he will pull his main parachute. The entire descent should last 15 to 20 minutes.
He will be rigged with cameras that will provide a live broadcast of the jump via the Internet, meaning countless viewers could end up witnessing a horrific accident.
Baumgartner is insistent on going live with his flight.
"We want to share that with the world," he says. "It's like landing on the moon. Why was that live?"
His team of experts – including the current record-holder from a half-century ago, Joe Kittinger, now 84 – will convene inside a NASA-style Mission Control in the wee hours Monday for the liftoff of the helium balloon at sunrise.
"All the things that can happen are varying degrees of bad," offers Baumgartner's top medical man, Dr. Jonathan Clark, a former NASA flight surgeon.
Clark was married to space shuttle astronaut Laurel Clark, who was killed aboard Columbia while it was returning to Earth in 2003, and he has dedicated himself to improving astronauts' chances of survival in a high-altitude disaster.
NASA is paying close attention, eager to improve its spacecraft and spacesuits for emergency escape, but is merely an observer; the energy drink maker is footing the bill and will not say how much it is costing.
The No. 1 fear is a breach of Baumgartner's suit.
If it breaks open – if, say, he bangs into the capsule while jumping or supersonic shock waves batter him – potentially lethal bubbles could form in his bodily fluids. That's what's known as boiling blood. A Soviet military officer died in 1962 after jumping from a balloon at 86,000 feet; the visor of his helmet hit the gondola and cracked.
During the descent, the temperature could be as low as minus 70. Baumgartner's suit will be all he has between his body and the extreme cold.
Then there's the risk of a flat spin, in which Baumgartner loses control of his body during the free fall and starts spinning. A long, fast spin, if left unchecked, could turn his eyeballs into blood-soaked, reddish-purple orbs, and he could be left temporarily blind. Also, a massive blood clot could form in his brain.
A small stabilizing chute will automatically deploy if he goes into a flat spin and blacks out or otherwise becomes incapacitated. He also has an emergency chute that will automatically deploy if he is unable to pull the cord on his main chute.
Baumgartner's team has a plan for every contingency but one: If the balloon ruptures shortly after liftoff because of a gust of wind or something else, the capsule will come crashing down with him inside. He won't have time to blow the hatch and bail out.
"I have every expectation that he'll come through this successfully based on our analysis," Clark says, "but you know, it still is an unknown."
Kittinger leapt from an open gondola on Aug. 16, 1960, from an altitude of 19.5 miles and reached 614 mph, or Mach 0.9 – records that stand to this day. He was a captain in the Air Force, and the military's Excelsior project was a test bed for the nation's young space program.
Kittinger has been Baumgartner's mentor, signing on with this new project after decades of refusing others' requests.
Fearless Felix insists he would not attempt the jump if the odds were against him.
"I think they underestimate the skills of a skydiver," says Baumgartner, who has made more than 2,500 jumps from planes, helicopters, landmarks and skyscrapers, with no serious injuries.
If he makes it back in one piece, Baumgartner plans on settling down with his girlfriend and flying helicopters in the U.S. and Austria, performing mountain rescues and firefighting.
"After this," he promises, "I'm going to retire because I've been successfully doing things for the last 25 years and I'm still alive."
Online:GUINNESS WORLD RECORDS
World's Largest Biceps
The largest male bicep belongs to Mostafa Ismail of Egypt. His left arm measures 25.5 inches when flexed and 24.5 inches when non-flexed.
Jyoti Amge and Brahim Takioullah
Jyoti Amge stands just under 25-inches and holds the title of world's shortest woman. Brahim Takioullah is 8-foot-1 and holds the record for the world's biggest feet
World's Longest Snake
Medusa, a 25-foot, two-inch Reticulated Python owned by Full Moon Productions in Kansas City, Missouri is the Longest Snake Ever in Captivity.
Ralph weighs a hopping 55 pounds, and eats about $90 worth of food a week!
World's Largest Mohawk
Kazuhiro Watanabe, a Tokyo-based fashion designer, has been recognized by Guinness World Records for his three-foot, 8.6-inch mohawk.
Largest Barbie Collection
Bettina Dorfmann of Germany has 15,000 different Barbie dolls, as of October 2011. She has been collecting them since 1993.
Largest Drum Kit
The largest drum set is comprised of 340 pieces, and is owned by Dr. Mark Temperato of Lakeville, New York.
Largest Hot Dog Commercially Available
The largest hot dog commercially available weighs seven pounds and and is available from Gorilla Tango Novelty Meats for $40.
In terms of rotor length, the smallest helicopter is the GEN H-4 made by Gen Corporation (Japan) with a rotor length of only 13 feet and a weight of only 154.32 pounds. It consists of one seat, one landing gear and one power unit. Unlike more traditional helicopters, it has two sets of coaxial contra-rotating rotors which eliminate the need for a tail rotor for balancing.
The tallest dog living is "Zeus," a Great Dane measuring 44 inches tall, owned by Denise Doorlag of Otsego, Michigan.
The tallest donkey living is Oklahoma Sam, a 4-year-old American Mammoth Jackstock, who measured 15.3 hands -- or 5-feet, 1 inch tall on 10 December 2011. He is owned by Linda Davis of Watsonville, California.
World's Tallest Cat
The tallest domestic cat ever was Savannah Islands Trouble, aka "Trouble", who was 19 inches tall before his death on August 15, 2012.
Heaviest Rideable Bicycle
The heaviest rideable bicycle weighs 1650 pounds. It was built by Wouter van den Bosch (Netherlands) and ridden in Arnhem, Netherlands, in May 2010.
World's Biggest Cheeseburger
In this Sunday, Sept. 2, 2012 photo provided by by Black Bear Casino Resort, people examine a bacon cheeseburger measuring 10 feet in diameter and weighing more than a ton at Black Bear Casino Resort near Carlton, Minn. The behemoth burger, served up Sunday at the Black Bear Casino Resort tipped the scales at 2,014 pounds. (AP Photo/
Mass-Massage World Record
Thai masseuses perform mass massaging at a sport arena on the outskirts of Bangkok, Thailand Thursday, Aug. 30, 2012. Thailand has long been known as the massage capital of the world. Now, it has a Guinness World Record to prove it when some 641 massage therapists mass-massaged 641 people simultaneously for 12 minutes to win the honor Thursday at an indoor arena in Bangkok. The event was organized by the Health Ministry to promote the Southeast Asian nation's massage and spa industry. (AP Photo/Apichart Weerawong)
Besse Cooper Turns 116
Besse Cooper, the world's oldest living person, marked another milestone as she celebrated her 116th birthday on Aug. 26. Cooper, who is originally from Monroe, Georgia, USA, was first certified as the world's oldest person by Guinness World Records in January 2011.
Farthest Distance Skateboarded By A Goat
The farthest distance skateboarding by a goat was 36 m (118 ft) and was achieved by Happie (USA) of Fort Myers, Florida , USA, on 4 March 2012. The distance was completed in a time of 25 seconds.
World's Largest Shaving Cream Pie Fight
On July 31, 2012, 714 people gathered in Dallas, Texas to participate in the world's largest shaving cream pie fight.
Heaviest Living Athlete
The heaviest living athlete in the world is Sumo wrestler Emmanuel 'Manny' Yarborough, of Rahway, New Jersey, USA. He stands 2m 3cm 6ft 8in tall and weighs a colossal 319.3kg 704lb. He was introduced to Sumo by his judo coach and seven years later, he is ranked number one in the Open Sumo Wrestling Category for Amateurs.
Longest Professional Wrestling Match
The longest professional wrestling match lasted 12 hours and was promoted by Shockwave Impact Wrestling (USA) as the Ultimate Iron Man Match at the Shelby County Fairgrounds in Sidney, Ohio, USA, on November 6, 2010. The match was contested by American Kickboxer II aka Brandon Overholser, Dark Angel aka Mike White, DJ Tom Sharp aka Tom Crone, Logan Cross aka Logan Jones, Sid Fabulous aka Mark Easterday, and "Lightning" Tim Lutz.
Longest Beach Volleyball Marathon
The longest beach volleyball marathon lasted 25 hr 39 min achieved by Mateusz Baca, Sebastian Lüdke, Tomasz Olszak, and Wojciech Kurczyński (all Germany) in Görlitz, Germany, on 3-4 July 2010. The attempt was made at the Rosenhof sports and leisure centre by the four members of sports club VfB Görlitz.
Longest Time Controlling A Football While Lying Down
The record for the longest time controlling a football whilst lying down is 10 min and 4 sec and was achieved by Tomas Lundman (Sweden) at the Nordstan Shopping Mall, in Gothenburg, Sweden on November 24, 2007.
Most Items Kicked Off People's Heads In One Minute
The most items kicked off people's heads in one minute is 43 and was achieved by Zara Phythian (UK) on the set of Guinness World Records Smashed, at Pinewood Studios, UK, on March 25, 2009.
Farthest Throw of a Person
Jonathan Macfarlane (New Zealand) threw Andrew Rainford a distance of 4.87 meters (15 ft 11 in) on the set of NZ Smashes Guinness World Records at the Sylvia Park shopping mall in Auckland, New Zealand, on July 25, 2009.
Most Passes of a Giant Volleyball
The most consecutive passes of a giant volleyball is 582 and was set by Vanessa Sheridan and Paddy Bunce (both UK) during Capital Breakfast with Johnny Vaughan, Capital Radio, London, UK on November 9, 2006 as part of Guinness World Records Day.
Fastest Mile on Spring Loaded Stilts
The fastest mile covered on spring loaded stilts is 7 min 13 sec set by Ashrita Furman (USA) at the TSV 1865 Dachau Sports Club in Dachau, Germany, on March 30, 2008.
World's Oldest Competitive Bodybuilder
Edith Wilma Connor, 77, from Denver, Colorado is the Oldest Female Competitive Bodybuilder, and started pursuing fitness in her late sixties when she realized she wanted more energy. She won her first competition at the age of 65.
Oldest Sisters Celebrate 213 Combined Years
Marjorie Ruddle, 105, and her sister, Dorothy Richards, 108, are officially declared the world's oldest sibling pair.
World's Oldest Yoga Teacher
Yoga teacher Tao Porchon-Lynch, 93, has been teaching yoga for more than 45 years and currently has 400 students in Winchester, N.Y.
Bruschi: Dog With World's Largest Eyes
Bruschi, a four-year-old black and white Boston Terrier, who lives with his owner, Victoria Reed, in Grapevine, Texas, holds the Guinness World Record for "dog with the largest eyes" -- a whopping 1.1 inch in diameter.
Chandra Bahadur Dangi
It's official! Guinness World Records officials have measured Chandra Bahadur Dangi to confirm his height of 21.5 inches (54.6 centimeters). That makes him not only the world's shortest living man but the world's shortest person ever recorded in Guinness' 57-year history.
World's Oldest Twins
Edith Ritchie and Evelyn "Evie" Middleton (née Rennie), born on November 15, 1909, are the world's Oldest Living Twins. The pair from Aberdeenshire, Scotland, celebrated their 102nd birthday in November 2011.
World's Shortest Woman
Guinness World Records Adjudicator Rob Molloy (R) and doctor Manoj Pahukar (2nd L) measure Jyoti Amge (C), 18, during a news conference in Nagpur on Dec. 16, 2011. Amge was officially announced by the Guinness World Records on December 16 the world's "shortest woman living (mobile)" measured as 62.8cm (24.7 inches) and will take the title from US woman Bridgette Jordan, previously held the record at 69.5 cm (27.4 in).
Andy Campbell and Buck Wolf of The Huffington Post's Weird News team took part in the Guinness World Record for Longest Curtsey Relay in 5 Minutes in January, 2012.
World's Smallest Working Dog
Lucy, a mini Yorkshire terrier from Absecon, New Jersey, is now in the Guinness Book of World Records. Weighing just 2 1/2 pounds, Lucy was named the world's smallest working dog last week, bumping out a 6.6-pound police dog in Japan.
102 year-old Twins
Sisters Ena Pugh (pictured right) and Lily Millward who have just celebrated their 102 birthday. They are officially the oldest twins in the world. The pair both live near Brecon, South Wales
Most Diamonds Set In One Ring
The Lobortas Classic Jewelry House in Ukraine created this record-setting ring -- the "Tsarevna Swan" -- containing an incredible 2,525 cut diamonds.
A volunteer lines up 25-Centavo coins on the pavement in an attempt to break the Guinness World Record currently being held by the United States at the Rizal Park in Manila, Philippines Wednesday Nov. 30, 2011. More than three million pieces are lined up for hours Wednesday to a stretch of 70 kilometers to break the 64.8 kilometers set by the United States. Proceeds of the campaign will help build classrooms in the country, according to the Central Bank, one of the organizers.
World's Smallest Living Cat
Fizz Girl, a Munchkin Cat from San Diego, California, has grabbed the record title for 'Shortest Living Cat'. Measuring in at just 6 inches tall from floor to shoulder, Fizz Girl weighs 4 pounds, 2.3 ounces. Munchkin cats are a special breed that have little legs caused by a naturally occurring genetic mutation.
Guinness World Records
Bridgette Jordan, 22, a college student in Centralia, Illinois, has just been declared the "World's Shortest Woman" by Guinness World Records. She stands 2 feet, 3 inches, 1.5 inches shorter than the previous record holder.
Guinness World Records
Bridgette Jordan, 22, is not only the current "World's Shortest Woman," but she shares the title of "World's Shortest Siblings" with her 20-year-old brother Brad. Bridgette stands 27 inches while Brad is who stands 38 inches high.
Guinness World Records
The Berghoff, a German restaurant in Chicago, wanted a world record in the "wurst" way -- and they succeeded -- with a 47-foot, three-inch bratwurst. The record-breaking brat weighed more than 40 pounds and needed a bun that was 50-feet long.
Chanel Tapper - Longest Tongue
Chanel Tapper has a tongue that measures a whopping 3.8 inches, from tip to top lip. However, British citizen Stephen Taylor's lengthy licker stretches 3.86 inches.
Sarwan Singh - Longest Beard
Sarwan Singh of Canada holds the record for longest beard: 7 feet, 9 inches.
Rolf Buchholz - Most Pierced Man
The world's most pierced man, Rolf Buchholz, of Dortmund, Germany, has 453 studs and rings all over his body, including 94 piercings in and around his lips, 25 in his eyebrows, eight in his nose and 278 in his genital area.
Aevin Dugas - Largest Afro
Aevin Dugas of New Orleans, La., is the proud owner of a record-breaking afro. It has a circumference of 4 feet, 4 inches. She trims her afro two or three times a year, and uses up to five conditioners at once when she washes it.
Pauline Potter, a 47-year-old, 643-pound Californian, has earned a spot in the 2012 Guinness World Records 2012 record book as the World's Heaviest Woman. She weighs 643 pounds.
World's Oldest Person
Besse Cooper, recognized as the world's oldest person, will turn 116 on Aug. 26, 2012. Cooper, pictured in her room in a nursing home on Feb. 1, 2011 in Monroe, Ga., was born in 1896.
World's Largest Fishing Lure
Guinness World's Records confirmed on August 10, 2011 a new world record and the debut of the World's Largest Fishing Lure, weighing more than 355 pounds and measuring more than 12 feet. The home of this giant lure is Sandestin Golf and Beach Resort and the SS Spitfire Mercantile, near Destin Florida.
Amazing Guinness World Records
Lu Zhi-hao is believed to be the world's fattest 4-year-old. The obese boy from China's Guangdong province weighs a stunning 136 pounds -- posing a major health risk, according to doctors. A health clinic in Hong Kong has offered free weight-loss treatment for the child.
World's Tallest Teen Girl
Malee Duangdee, 18, stands outside her home with her relatives Mai Khosod, 37, and A Khosod, 24, who are holding her arms up on April 7, 2011, in Trat Province, Thailand. Towering head and shoulders above her own parents this giant teenager -- at 6 feet 10 inches -- is the tallest in the world and could still be growing.