When skydiving from 25 miles above Earth, the human body breaks the speed of sound. There is no friction to slow a free-falling body. The air is too thin.

Alan Eustace went supersonic just 31 seconds into his record-breaking free fall from 135,890 feet on Oct. 24, 2014. Twenty seconds later, he reached a maximum speed of 822 miles per hour—Mach 1.22—before the density of the lower atmosphere began to slow him down.

“There’s no sensation when you cross Mach,” Eustace explained in his keynote address to the Smithsonian National Air and Space Museum in 2016. Though his ground crew claims to have heard the sonic boom, “the only way I know that I crossed Mach is because of the GPS traces.”

While others had skydived from the edge of space before Eustace, no one did it quite like him. In fact, little had changed since 1960, when Air Force Col. Joseph Kittinger set the world record for highest-altitude free fall at 102,800 feet, a feat no one would surpass for 52 years. He ascended in an open gondola pulled by a helium balloon. To protect his body from the vacuum of the upper stratosphere, Kittinger wore the same flight suit as U-2 pilots, the David Clark MC-3. The gondola carried enough oxygen to keep the suit pressurized and Kittinger breathing until he reached target altitude, at which point he detached from the oxygen cables tethering him to the gondola and fell back to Earth.

Eustace, however, was wary of the gondola. He preferred to ascend by balloon only, and that would require one hell of a durable spacesuit. So Eustace and his team reached out to ILC Dover in Frederica to design and build the suit that would keep him alive, which would lead to the first major redesign of the spacesuit—the same spacesuit that has kept dozens of American astronauts safe in space—in decades.

“Eustace’s suit had to do a little bit of everything,” says design team member Dave Graziosi. “I would say the problem is actually harder” than keeping an astronaut alive in space. “For me, this was a real paradigm shift.”

ILC Dover designed and built the spacesuit that allowed Alan Eustace to break the world record for highest-altitude free fall.//Photo by Luke Evens

The history

Before Eustace, every high-altitude skydive record attempt had been made from a gondola. In theory, the structure functioned as a redundant safety measure, a protective shell that provided tracking, communications and critical life support systems to a well-suited skydiver. In the event of a suit malfunction, the gondola would become an emergency shelter that would slowly descend to safety.

In practice, however, the gondola increased risk to the pilot. On Kittinger’s first jump, from 76,000 feet in November 1959, he accidentally pulled the timer on his first parachute moments after disconnecting from the gondola’s oxygen tank. The chute deployed prematurely, he broke into an uncontrolled spin, and a line wrapped around his neck as Kittinger lost consciousness. He was saved only by his reserve parachute, which deployed automatically at 10,000 feet.

In 1962, Pyotr Dolgov’s face mask collided with the gondola at 93,970 feet, depressurizing the suit and killing him instantly. During Nick Piantanida’s second balloon flight in 1966, the veteran skydiver was unable to disconnect from the gondola’s oxygen lines. He was forced to abort the jump at 123,500 feet. On Piantanida’s final attempt that same year, his helmet suddenly and mysteriously detached at 57,000 feet. A deafening rush of wind heard over the radio was the only warning to his ground crew that something went horribly wrong. When the gondola returned, Piantanida was found unresponsive. He died in a coma four months later.

A half-century after making his record dive, Kittinger advised Felix Baumgartner on his record-breaking free fall for the Red Bull Stratos project. Like Kittinger, Baumgartner ascended in a gondola wearing a David Clark flight suit, only this time the gondola was basically a pressurized space capsule.

Despite its poor safety record, no one had ever attempted a high-altitude balloon jump without a gondola. There was no protocol. There were no designs or case studies. Without the gondola, Eustace would need all tracking, communications and life support systems housed in a pressurized suit durable enough to fly into the cold vacuum of near-space, fall back faster than the speed of sound, and then withstand a hard landing among brush, rocks and cacti in the desert outside Roswell, New Mexico.

“It’s a unique suit from ILC’s perspective because usually, when they’re working on a spacesuit, they’re working with a spacecraft manufacturer—the suit has to work with an existing craft,” says Cathleen Lewis, space history curator and spacesuit expert at the Smithsonian National Air and Space Museum, where Eustace’s suit is now on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia. “Now here they were creating a suit that, in essence, is a spacecraft. So they’re working with a far more abstract set of goals and ideals in trying to make the suit both a spacecraft and a flight suit.”

Eustace ascended by balloon wearing a suit that, in essence, was a spacecraft.//Photos courtesy of Alan Eustace

The idea

Taber MacCallum thought he had heard it all. As CEO of Paragon Space Development Corporation in Tucson, Arizona, MacCallum was at the helm of a private aerospace company that specialized in technology to keep humans alive in extreme environments, from the depths of the ocean to the vast emptiness of outer space.

Under MacCallum, Paragon developed a reputation as an innovative company where people think outside the box. “So every month or so, someone with an extreme idea would give us a call,” says MacCallum, before joking about one caller’s pitch to descend into a volcano.

The pitches rarely worked out, though not for lack of imagination. MacCallum loved crazy ideas. He was a crew member of the Biosphere 2 project, where he lived in an artificial environment isolated from the outside world for more than two years. For the next 20 years, MacCallum was at the helm of Paragon, guiding the company through multiple spacesuit projects for NASA. Paragon was also developing spacesuit technology for a mission to Mars.

But crazy ideas, however exciting, usually cost boatloads of money, and none of the callers had the kind of cash needed to finance dreams straight out of science fiction.

“Ninety-nine percent of them never panned out,” MacCallum says. Nevertheless, he remained optimistic that, one day, one of those random calls would turn into something amazing.

Enter: Alan Eustace. There was something different about Eustace. For one, he didn’t make the initial call himself. He reached out to Peter Diamandis, founder of the XPrize Foundation, who made the introduction and explained to MacCallum that Eustace wasn’t some daredevil looking to make a name for himself; this wasn’t going to be like Red Bull Stratos. Eustace was a Silicon Valley executive, the senior vice president of knowledge at Google. He had a Ph.D., and it was clear that Eustace had been developing the idea for years.

When they first spoke over the phone, MacCallum was impressed. Eustace thought like an engineer. He approached problems with an open mind and was more interested in technological advancement than having his face on the front of a magazine. Eustace also had the financial means to support the project, named StratEx, short for Stratospheric Exploration.

By the end of the call, Eustace had sold MacCallum on the idea: Get rid of the gondola and integrate all life support directly into the jump suit. Of course, this would add hundreds of extra pounds to the suit, making it more difficult for Eustace to maintain control during free fall—and all but impossible to stick the landing. Nevertheless, in theory at least, this would be very similar to a tandem jump, only instead of another skydiver strapped to his chest, Eustace would have oxygen tanks and computers.

“SCUBA diving in the stratosphere,” Eustace called it. The more MacCallum listened, the more he believed it could be done.

“Often, the simplest solution is the safest solution because accidents are born out of complexity,” says MacCallum. “Why do we need a capsule? Just make a really good spacesuit, and if the spacesuit is good enough for the dive back, then it has to be good enough for two hours up.”

There are a lot of companies that make the kinds of pressurized spacesuits needed for such a jump, but MacCallum wanted ILC Dover. “ILC comes with this huge variety of subsystems and components,” he says, and this allowed StratEx to build a custom-made spacesuit specifically for this project, specifically for Eustace. MacCallum was also confident that ILC had the expertise StratEx would need for a successful mission. “They build the really hard suits. They’re the bedrock company of really, super, hard problems.”

So by December 2011, MacCallum began reaching out to suit manufacturers across the country, purposefully saving ILC for last. Two days before Christmas, he sealed the deal.

ILC normally turns down extreme skydiving projects because the risk and reward don’t work out, says Graziosi, who was chief engineer at ILC during the StratEx project, on which he also worked as program manager. Up until then, ILC had built spacesuits exclusively for governments and a few select commercial operations. If something were to go wrong and Eustace died, the optics of outfitting a private individual with a spacesuit would have reflected poorly on ILC. But MacCallum sold them on the science. Fewer humans had explored the stratosphere than had landed on the moon. StratEx was about exploration and the advancement of science.

“Eustace wasn’t doing this to break records,” says Graziosi. And for ILC, these are the types of projects that keep engineers sharp. “It allowed our engineers to do something they wouldn’t normally be able to do. It allowed us to push the envelope.”

“I left that meeting and called Alan,” MacCallum recalls saying to Eustace, “I have a Christmas present for you. It’s a spacesuit.”

The StratEx team that built the super suit included engineers from ILC Dover in Frederica.//Photo by J. Martin Harris Photography

The suit

ILC Dover has built pressurized spacesuits for NASA since the Apollo program. In the industry, pressurized spacesuits are called extravehicular mobility units, or EMUs. In the vacuum of space, the suits provide astronauts with an atmosphere to breathe and basically keep bodily fluids from evaporating. ILC manufactured Neil Armstrong’s EMU for the moon landing. For every spacewalk since, from the Space Shuttle to the International Space Station, astronauts have explored the cosmos in suits manufactured in Kent County.

“You can draw a straight line from the suit used on the moon to the current EMU,” says MacCallum. And though NASA and ILC have developed EMU prototypes for future missions to the moon and Mars, none were put through the same rigorous flight testing as the StratEx suit. “This may be the first new design of a suit in the world that a person flies in, in like 40 years. It was never rethought from scratch, and we were rethinking from scratch how to do a suit.”

Some of the parts needed for the StratEx suit were specialized hardware, like the helmet, visor, bearings and various other doohickeys. These were manufactured in Delaware, but the rest of the suit was designed and manufactured in Houston at a small satellite campus ILC opened near the Johnson Space Center while building spacesuits for the Constellation Program, which promised to return us to the moon no later than 2020. After Constellation was scrapped in 2009, the Houston team continued to spearhead research and development in advanced spacesuit designs.

ILC’s Houston lab was well-suited for this kind of project. The crew there was small, just a few dozen engineers and support staff, which would allow ILC to keep the project a closely guarded secret until the final jump. Moreover, the Houston team was experienced in developing advanced spacesuit prototypes. Graziosi had worked at ILC for more than 20 years. Hired fresh out of college, he has designed all kinds of spacesuits, including the Constellation EMU.

From the start, Graziosi could see that Eustace and MacCallum weren’t looking for a standard EMU. It wouldn’t have worked well in the stratosphere. Spacesuits are designed to operate in a very specific environment that never changes. Because there is no air in outer space, there is also no convection to carry heat away from the body. This creates an overheating problem inside spacesuits, so astronauts wear special undergarments, called tube suits, that circulate cold water around the body.

Eustace wasn’t going to be in danger of overheating. At 35,000 feet, the suit would need environmental controls to keep him from freezing to death in temperatures that drop to roughly negative 70 degrees Fahrenheit. “It’s more like a Martian environment, where you have some convection and some really cold temperatures,” says Graziosi.

“It was unique to this suit as compared to any other suit we’ve done before, because we were actually in the atmosphere, so it was a whole different kind of insulation than what we normally fly in space,” says Ryan Lee, a senior spacesuit designer at ILC who also worked on the StratEx project. “So we actually had to use lofted insulation, like you find in a jacket or a coat, and build our insulation layers like that.” Eustace wore a tube suit, but his circulated warm water to help maintain his body temperature.

Around 70,000 feet, however, something peculiar happens: The temperature begins to warm again. This is called temperature inversion—as the atmosphere thins, convection dissipates, and ozone absorbs the sun’s ultraviolet radiation, causing the temperature to warm back to a smidge below freezing—warm enough for Eustace to survive, were it not for the lack of oxygen. To protect Eustace from harmful levels of radiation, the outer layer of the suit is Ortho-Fabric, a durable woven material made with a blend of Gore-Tex (also from Delaware), Kevlar and Nomex. This is the white fabric that people usually associate with spacesuits.

Ortho-Fabric was ideal for Eustace’s suit because it proved durable enough to withstand hard landings in the New Mexico desert. Eustace was never able to stick a smooth landing. Weighing in at over 400 pounds, the entire spacesuit assembly, including Eustace’s body weight, was far too heavy. The best Eustace could do was lean into his descent and hope to skid across the ground, as opposed to tumbling head over heels.

So over the course of about six months in 2012, the ILC team in Houston built a different kind of spacesuit, and they did it from scratch, measuring, cutting and stitching one layer of fabric at a time.

The tests

​ILC delivered the suit in December 2012, but it was far from finished. Lee and Graziosi continued working with StratEx through hundreds of tests, including the final jump.

Photo courtesy of Alan Eustace

The StratEx team expected things to go wrong. After all, that’s the point of rigorous testing—every time something breaks, or malfunctions, the team gets one step closer to working the bugs out. Things went wrong from the start. The oxygen-delivery system designed by Paragon didn’t work on the first test, and the system’s designer, Jared Leidich, nearly suffocated in the suit as the team scrambled to pry the helmet away from the suit. Then there was the tube suit, which wasn’t circulating warm water as it should have. Placement of the life support system on the front of the suit needed to be just right, as they learned during wind tunnel testing, otherwise Eustace could be thrown into a violent spin.

Over time, however, more things started going right than wrong, and the team became more confident in their ability to conduct a successful jump. Soon, they would need to start pushing stuff out of an airplane to see what worked and what failed.

Of course, the one thing that needs to work every single time, without exception, is the parachute. Despite extensive computer modeling, no one was quite sure what would work. They needed a parachute that wasn’t going to fail on Eustace as he plunged faster than the speed of sound.

So Leidich started pushing concrete missiles out of an airplane over Coolidge, Arizona. He calls them ballistic darts— 10-foot-long cylinders of concrete that weigh 600 pounds. The first missile snapped the parachute line and hit the ground at 700 miles per hour, which instantaneously liquefied the desert floor around the impact site and swallowed all the debris. Leidich had to dig down six feet just to reach the tail, where computers and other sensitive equipment were housed.

After a few more failures, and a few more lost missiles, the parachute was ready to go, and the team began pushing Eustace out of the back of an airplane. Over the course of several months, the StratEx team slowly increased the altitude and difficulty of the jumps. With one exception—when Eustace drifted off course and the team had to race across the desert to find him—the jumps went off without a hitch.

By December 2014, almost four years after Eustace first reached out to MacCallum, the StratEx team was ready for the final jump. Every system had been tested extensively. The suit had been rebuilt four times. Every wire and tube were perfectly assembled. Every member of the team knew where he was supposed to be and what he was supposed to do.

Eustace looked relaxed as the StratEx team attached him to a balloon, then cut him loose from the tarmac. Seconds later, he was gone, floating upward at 1,000 feet per minute for the next two hours until he came booming back to Earth. He was back at work the following Monday. “Who would have thought that all by themselves, a team of maybe 20 people or less could basically build everything necessary to get somebody up to above 99.5 percent of Earth’s atmosphere, see the curvature of the Earth and the darkness of space, and return to ground safely in a means that no one has ever tried before,” Eustace told the Smithsonian. “For me, that’s the exciting part.”