Felix Baumgartner, the daredevil who stunned the world this weekend with a 23-mile skydiving free fall, could handle the height, just not the tight, pressurized suit.
Like millions of others, the 43-year-old Austrian suffers from claustrophobia. His feat, leaping from 102,800 feet and breaking the unofficial record set by Col. Joe Kittinger in 1960, almost never happened.
"Go figure," said Reid Wilson, director of the Anxiety Disorders Treatment Center in Chapel Hill, N.C., and founder of self-help website Anxieties.com.
"He is basically in open space and not wrapped up that way," Wilson said of Baumgartner's previous jumps from the Petronas Towers and the Taipei 101 skyscraper.
Wilson said it was not at all odd for a person to fear the suit more than the height. He noted that half of all pilots are actually afraid of heights. He advised American Airlines when it created its fear-of-flying programs and noted that phobic pilots say they feel shielded in the cockpit.
An estimated 11 million Americans suffer from phobias, and the fear of closed-in spaces is one of the top five, Wilson said, citing worries about being trapped or suffocating. But that is "totally different" from acrophobia, or fear of heights, which is among the top-10 fears but not an issue for Baumgartner.
The former paratrooper said he was nearly paralyzed getting ready for his latest stunt, one that broke world records and the sound barrier.
In an interview with Red Bulletin magazine earlier this year, he said, "...We carried out the last major tests with the space suit and it was clear to me that I had a problem -- one I never thought I'd have -- with my psyche. I had trouble putting on my space suit, and it got worse and worse. I could barely stand a couple of minutes in it."
Baumgartner's customized space suit and helmet are typically worn by high-altitude pilots and can constrict movement and vision.
They were described by his team as "his personal life-support system," according to a report in the Guardian newspaper. It had four layers, a "comfort liner," a gas layer that retained air pressure, the restraining layer to keep the suit's shape and an external layer made of fire-prevention material.
The suit was designed to protect him from ebullism, the biggest medical danger in skydiving. When the body is exposed to a vacuum, even for a short period of time, the blood can literally boil, causing the body's fluids to turn to gas.
The low pressure can also cause gas to seep into the body and, like skin diving, cause decompression sickness or the "bends." Gas bubbles in an artery can also stop blood flow.
"As soon as the visor closes, there's this nightmarish silence and loneliness," Baumgartner told Red Bulletin. "The suit signifies imprisonment.
"We'd never thought of a test that confined me in the suit for five hours -- that's how long the entire mission should take -- with the visor closed. After all my past exploits, all the extreme things I've done in my career, nobody would have ever guessed that simply wearing a space suit would threaten the mission. Me included. In the end, it turned into panic attacks."
Baumgartner said he was prepared to give up and left the United States where he had been training in 2010.
"I wept on the phone," he said. "It was the worst moment of my life. Until that point, I'd always known how to solve all my own problems. This time, in front of everyone, I'd found my limit."
He overcame his phobia with the help of his sponsor, Red Bull. It called Michael Gervais, a psychologist whose specialty is extreme sports, according to The New York Times. He has consulted with NFL athletes and surfers.
"Claustrophobia is quite common and people get it in any kind of tight spaces," anxiety psychologist Wilson said. "Early on, when the MRIs came out and they put people in those tubes, they lost about one-third of them who got panicked inside the machine.
"Quite often, they feel hot and stuffy and don't necessarily have a full-blown panic attack, but have the typical fight-or-flight urge to escape," he said.
Wilson said that like the fear of heights, claustrophobia is a "natural" fear that has evolutionary roots. But some people find it more disabling than others, probably a result of to genetic vulnerabilities.