Jim Toomey has a weakness for space memorabilia, but he doesn’t have unlimited funds. So he had to keep his desires in check as he perused an online auction of NASA relics in May 2012. The Bradenton, Florida, entrepreneur mustered the self-discipline to skip the $53,758 baggie from Apollo 15 that had once held lunar dust, as was well the Gemini 5 log book that went for $33,844. He instead scooped up what he terms “a whole bunch of space junk.” His haul included a dented bracket from a Space Shuttle’s tail fin ($240), a spacesuit’s heater cable ($240), and four reels of 16-mm film that were advertised as having something to do with Viking, the 1970s NASA program that landed America’s first two spacecraft on Mars ($360).
Toomey promptly donated all his NASA curios to the South Florida Museum, where he served as a trustee. Though the museum appreciated the gifts, it deemed them too offbeat for public display. Instead they wound up in a box on a backroom storage shelf, amid a sea of other forgotten artifacts.
Toomey didn’t give the space junk another thought until September 2015, when he received an odd phone call from the Boston auction house that had sold him the goods. The caller said the company had been contacted by an engineer from NASA’s Jet Propulsion Laboratory named Rob Manning who was desperate to locate the Viking films. According to Manning, NASA had discarded the reels by accident; they’d been left in a file cabinet marked for sale as government surplus during an office move in 1999.
Toomey agreed to speak to Manning and assured him that the objects had been preserved rather than melted down for their silver. During that conversation, a grateful Manning revealed why he and his JPL colleagues were so eager to view the films: They contained the only surviving footage of the August 1972 qualification test for Viking’s parachute, the contraption responsible for safely decelerating the program’s landers through the Martian atmosphere. Because that atmosphere is 99 percent thinner than Earth’s, Viking’s engineers knew their spacecraft would be plummeting at supersonic speeds as they neared the planet’s surface. The engineers had thus built a novel parachute that could endure such punishing conditions—a 2,200-square-foot expanse of white polyester with braided nylon suspension lines.
The August 1972 test had confirmed their success. A balloon first carried a 1,900-pound capsule to the edge of the stratosphere at New Mexico’s White Sands Missile Range. When the vehicle dropped free from the balloon, it fired rockets that cranked up its speed to nearly 1,600 miles per hour. At that point, a small explosive blasted open the compartment that held the parachute. An on-board camera captured the violence of that moment, as the polyester jerked and shuddered before mellowing into a stable hemisphere. The films that Toomey had bought at auction, and which NASA wished to reclaim, were the sole visual evidence of that engineering triumph.
NASA’s supersonic parachutes have barely evolved in the 46 years since that milestone above the New Mexico desert. The Viking model worked so well that the space agency kept using it for all of its Mars missions, thereby eliminating the need to spend hundreds of million of dollars on new tests. When the Curiosity rover alighted inside the Gale Crater in 2012, for example, it did so with the aid of a parachute that was essentially a larger version of the one that had decelerated the Viking 1 lander 36 years earlier.
But the trusty Viking parachute is finally on the verge of obsolescence. The aging design can’t provide the drag necessary to slow down payloads much heavier than a ton—a significant problem for NASA given that its longterm Martian dreams involve vehicles that will weigh more than 20 Curiosities combined. And so the engineers at JPL have been scrambling to come up with a much tougher replacement, a parachute that can help solve the Martian version of the last-mile problem for decades to come.
Rob Manning went searching for the lost Viking films as part of that crucial effort. He found them right as NASA’s supersonic parachute team was reeling from its second major setback in as many years, failures that underscored the maddening complexities of predicting how cloth and rope will behave at extraordinary speeds.
Parachutes may lack the obvious sex appeal of jets and rockets, but their aeronautical value wasn’t lost on the organizers of Operation Paperclip, the American intelligence venture that brought hundreds of German scientists to the US in the wake of World War II. Among the engineers they chose to spirit out of Germany were Theodor Knacke and Helmut Heinrich, the stars of the parachute section at the Graf Zeppelin Research Institute in Stuttgart. The two men were taken to Wright-Patterson Air Force Base in Ohio and put to work on military projects such as developing the braking parachute for the B-47 bomber. (Before the advent of thrust reversers, the high-speed bombers needed help slowing down when landing.) During the duo’s years at Wright-Patterson, Knacke invented the ringslot, a low-cost parachute that features circular bands of fabric separated by horizontal gaps. Heinrich, meanwhile, won a series of patents for methods of enhancing the stability of parachutes as they unfurl.
The advent of the American space program in the 1950s gave Knacke and Heinrich the chance to forge prestigious careers beyond Ohio. Though NASA briefly flirted with the idea of using a glider wing to make its manned vehicles steerable as they returned to Earth, parachutes won out as the most dependable and efficient means of slowing down spacecraft prior to splashdown. But there were few American engineers who specialized in parachutes, a technology that was widely thought to lack machismo. “You’d have these mechanical engineering guys look around at all the textiles and the sewing that go into it and they’d say, ‘Well, that’s women’s work,’” says Chuck Lowry, a Kentucky-bred legend of parachute design who cut his teeth on ejection seats and later became a key figure in the Apollo program. “When I was at North American Aviation, we had 100,000 employees and mine was the only badge that said PARACHUTES on it.”
The two German émigrés took advantage of this talent vacuum to become the fathers of American space parachutes. The entrepreneurial Knacke struck out for Southern California, where he founded Space Recovery Systems in 1957; the company manufactured parachutes for experimental rockets such as Blue Scout I, which was used to gauge the stresses of atmospheric re-entry. Five years later he joined Northrop as chief of the division that held the parachute contracts for the Gemini and Apollo programs. It was Knacke who persuaded NASA to select the famous three-parachute cluster for its Apollo capsules; he believed that a single large parachute would take a dangerously long time to open. (Toward the end of his career, which lasted well into the 1990s, Knacke wrote a book, Parachute Recovery Systems Design Manual, that’s acknowledged as the bible of his discipline.)
Heinrich, by contrast, resisted the siren call of industry to enter academia. In 1956 he became a professor of aeronautical engineering at the University of Minnesota, a position he would hold until his death 23 years later. NASA soon began pumping millions of dollars into Heinrich’s lab, much of it earmarked for one blue-sky project in particular: the development of a parachute robust enough to withstand supersonic flight. Though NASA still had yet to loft a human into space, it already had notions that a supersonic parachute might come in handy someday—if not on Earth, then perhaps on Mars or Venus.
The challenge was a daunting one: Parachutes are erratic beasts in even the calmest of conditions. “Parachutes have so much randomness to them,” Lowry says. “It’s not like the wing of an airplane, where it stays the same as it goes up and it goes down. A parachute is stowed in this bag and then it has to assemble itself into this shape. But there are a million other shapes it takes as it does that, and a million variables that affect that process of deployment and inflation. You just never know what’s going to happen as it captures the air.” And when that air is stratosphere-thin and rushing by at supersonic speeds, the list of things that can go wrong gets staggeringly long; there are countless potential pressure spikes that can distort the canopy as it struggles to achieve its final form.
Yet Heinrich was the ideal engineer to work on this problem because he’d solved it once before—albeit on a very small scale. Back in Stuttgart during the war, he’d made a mini parachute that the Luftwaffe used to control the descent of its mines and torpedoes. This so-called guide surface parachute, a dramatically cupped arrangement of eight triangular panels that measured four feet across, was notable for how little it oscillated when buffeted by strong winds. It was so stable, in fact, that it was able to survive wind-tunnel tests that mimicked the effects of traveling at Mach 3—more than 2,300 mph.
Heinrich’s research at the University of Minnesota focused on how the structural elements of parachutes—the vents and the stitching, for example—can be configured to absorb and dissipate the effects of supersonic shock waves. Though his labor would prove invaluable to NASA, he wouldn’t be the engineer to come up with the winning parachute design for Mars. That honor would instead go to one of his star students, a man named Clinton Eckstrom.
Soon after leaving his mentor’s lab, Eckstrom landed a job with G.T. Schjeldahl, a Minneapolis-based manufacturer of Mylar weather balloons. The company asked him to create a parachute for rockets that can reach the mesosphere; Schjeldahl wanted to get into the business of gathering meteorological data at 200,000 feet, where the atmospheric density happens to be similar to that on Mars. In 1964 Eckstrom completed his assignment by patenting what came to be known as the disk-gap-band parachute, or DGB. The design is primarily comprised of just two large swaths of cloth, separated by a sizable gap: a top shaped like an inverted saucer and a lower circular strip.
Impressed by the DGB’s reliability in high-altitude environments, NASA hired Eckstrom to work on its first series of supersonic-parachute tests, the Planetary Entry Parachute Program. Awash in limitless cash thanks to its pivotal role in the Cold War, NASA spent vast sums on the program and two follow-up initiatives. Eckstrom and his fellow engineers enjoyed the freedom to launch as many test vehicles as they wished, so they didn’t sweat their numerous semi-comical failures: In at least two atmospheric tests, for example, the parachutes’ bags, which were supposed to be fired clear during deployment, tore back through the open canopies like bullets.
A test vehicle from the Planetary Entry Parachute Program.||||
By the early 1970s, NASA had narrowed its field of potential supersonic parachutes to two finalists. One was a fortified version of Eckstrom’s DGB, which had gained a reputation for orderly inflation; the other was a ringsail, a more elaborate successor to Knacke’s ringslot, which produced superior drag. NASA ultimately decided to play it safe and opt for the less complicated design: It was a DGB that passed muster at the White Sands Missile Range in August 1972, and it’s been part of all seven NASA missions to the Martian surface.
Despite the DGB’s spotless service record, there remain skeptics who believe the ringsail should have prevailed in the Viking competition. Their arguments resonate with the young engineer who’s been entrusted to create NASA’s next supersonic parachute, an endeavor he describes as “playing chess with the laws of physics.”
Within minutes of welcoming me into his office at JPL in Pasadena, California, Ian Clark has a swatch of ripstop nylon dangling from the corner of his mouth. “I’m going to have to go Hulkmania on this,” he says as he strains to tear the hardy fabric with his teeth. Once he finally manages to shred it, he hands me a fragment so I can examine the fibers that dangle from its edge—the matrix of a modern space parachute, which use ultra-light nylon in lieu of heavy Dacron polyester.
Clark knew next to nothing about parachutes when he started at JPL in 2009. As a doctoral student at Georgia Tech, he’d become an authority on so-called inflatable aerodynamic decelerators—giant inner-tube-like devices that are meant to be placed on the undersides of supersonic spacecraft, and which should theoretically act as brakes when they’re inflated in the atmosphere. (When fully filled with air, they resemble Victorian hoop skirts.) His original marching orders at NASA were to build an inflatable decelerator so effective that it could slow a Mars-bound vehicle to less than the speed of sound in a matter of minutes. Once that goal was reached, a supersonic parachute wouldn’t be necessary; a run-of-the-mill subsonic parachute would suffice to finish the braking job and prepare the spacecraft for landing.
But Clark wasn’t at JPL long until he realized that his plan to use inflatable decelerators instead of supersonic parachutes had been wildly optimistic. “You ran the math on trying to bump the parachute down to subsonic, and the inefficiencies associated with that started to manifest very quickly,” says Clark, a wiry 37-year-old who radiates a cheerful yet manic intensity. “You would need just these enormous inflatable drag devices, so enormous there’s no way they could ever be efficient.” By his second year at NASA, then, he became committed to a new strategy for slowing down future multi-ton—and perhaps manned—spacecraft as they approach Mars: coupling his inflatable decelerator with a revamped supersonic parachute.
Clark’s two-part concept became the foundation for the $200 million Low-Density Supersonic Decelerator project, which he was tapped to lead as principal investigator. In addition to building a 6,800-pound UFO-like vehicle equipped with one of Clark’s inflatable skirts, the supersonic decelerator team would also prototype a replacement for the Viking parachute. The plan was to fly the system three times at the Pacific Missile Range Facility in Kekaha, Hawaii. Those tests would be the first since 1972 to attempt to deploy full-scale supersonic parachutes in the Earth’s atmosphere.
Since supersonic-parachute research had been stagnant for 40 years, the team had to get creative when recruiting talent. One of the project’s unconventional hires was a Clara O’Farrell, an Argentinian engineer who spent her graduate career at Caltech studying jellyfish locomotion—specifically how the creatures propel themselves by squeezing out vortex rings. Though she’d long yearned to work on spaceflight, she feared there would be little demand for her arcane expertise. “When I graduated and started looking for a job in the industry, my background in fluid dynamics didn’t seem too useful since there aren’t many areas of space with fluids,” she says. “The whole space-being-a-vacuum thing sort of got in my way.” But O’Farrell found a home at JPL analyzing the physics of the supersonic decelerator’s parachute, a structure with many of the same amorphous qualities as a jellyfish’s body.
Clark and his team tested 55 potential parachutes in a wind tunnel. They were able to weed out some of the candidates by attacking them with scisssors and then testing them anew; if a parachute couldn’t continue to perform after receiving a few slashes from a handheld blade, it stood no chance in the unforgiving Martian atmosphere. As worthy contenders emerged from the pack, Clark also dove into the literature on supersonic parachutes from NASA’s Nixon-era heyday. His archival research led him to admire the ringsail, the runner-up in the Viking contest. He liked that the design used thousands of stitched-together panels in its canopy, as opposed to the DGB’s reliance on a solid disk of cloth. Clark hypothesized that the ringsail’s more complex arrangement would make it less susceptible to failure, since tears can’t easily propagate from one isolated panel to the next. “The analogy I use is that the DGB is like a Toyota Camry—it’s very simple, but seemingly very reliable,” says Clark. “Whereas the ringsail, it’s much more finely tuned.”
Despite Clark’s enthusiasm for the ringsail, he wasn’t quite ready to ditch the disk-gap-band parachute entirely for the first supersonic decelerator test in June 2014. He instead settled on a hybrid: The lower portions of the parachute were constructed from small individual panels, but the top was a shallow broadcloth disk. Clark dubbed his invention the disk sail.
Though appealing on paper as a best-of-both-worlds solution, the disk sail fared poorly in Hawaii. The trial started off well, at least: The test vehicle reached an altitude of 120,000 feet while tethered to a balloon, then cut free and used its rockets to climb another 70,000 feet. At a speed of more than 2,800 miles per hour, the inflatable decelerator—the hoop-skirt contraption—expanded to its full girth in less than a second; the drag it produced cut the vehicle’s speed by around 30 percent. But when the mortar fired to open the parachute compartment, everything went awry: The Technora suspension lines didn’t even get a chance to straighten before the parachute was cut to smithereens by the environmental forces.
The test data convinced Clark that the disk sail’s top was doomed to become as flat and tight as a snare drum’s head when pelted with fantastic amounts of pressure. And so for the second test, scheduled for June 8, 2015, he elected to go full ringsail: He replaced the disk with a slew of bulbous panels that gave the parachute a more intricate, rounded shape.
To make sure they were on the right track, the team attached the ringsail to a rocket-powered sled—essentially just a quartet of high-powered engines affixed to a rail track—at Naval Air Weapons Station China Lake in California’s Mojave Desert. The parachute showed no signs of being fazed when the moving sled subjected it to 120,000 pounds of force—40,000 more pounds than the balloon test was anticipated to create. Clark was confident all would go smoothly on the next flight, and that his project would pull off a feat that hadn’t occurred on Earth in 43 years.
The second test once again began with a flawless performance by the airbag. The parachute’s white-and-orange fabric came gushing out as the vehicle hit Mach 2.4. For a few hundredths of a second, the ringsail opened just as everyone had hoped, with billowing edges that betrayed no hint of being warped by abnormal pressure. But when the parachute was 98 percent of the way to full inflation, a triangular slice of the canopy peeled away. The parachute hung there for a moment, taunting the engineers in the control room with its missing portion, before disintegrating into a jumble of flaccid ribbons.
As he watched the culmination of a half-decade’s worth of work turn into something that resembled used Kleenex, Clark vacillated between numbness and self-flagellation. The computer models, the wind-tunnel tests, the rocket sled—all of his team’s preparations had pointed toward a positive result. Yet there it was on the control-room screen, impotently flapping in the supersonic breeze. Clark knew then that he’d placed too much faith in math.
Four months after the second supersonic parachute disappointment, Rob Manning lifted Clark’s spirits with some good news: By sleuthing around the internet, he’d finally located the long-lost films of the last Viking parachute test. The South Florida Museum had agreed to give the priceless footage back to NASA, but Clark would have to pick them up himself and, as small recompense, deliver a public lecture at the museum’s planetarium.
As soon as he touched down back in California, Clark took the reels to a Hollywood company that restores damaged movies. The films were in surprisingly decent shape and the restorer was able to play them on a projector with minimal effort. Elated, Clark took an iPhone video of a segment that shows the parachute’s inflation in slow motion. That clip was what he’d been seeking ever since the last misfortune in Hawaii: visual evidence of what a supersonic parachute should look like when things go right.
Clark craved such evidence because he’d concluded that, despite his exhaustive research, the physics of supersonic parachutes are still too poorly understood to be of much use to an engineer. He had assumed he could predict how those parachutes would behave based on existing data from the 1960s and early 1970s. But the bewildering supersonic decelerator experience had taught him that there just haven’t been enough real-world tests to build an effective model. He thus realized that, at least until there are many more tests on the books, he must rely less on raw numbers and more on intuition—something that left-brained engineering types are typically loath to do. Picking apart the Viking films frame-by-frame was one of the few ways he could hone that sixth sense.
Clark also sought advice from several parachute graybeards, engineers who’d trained under Theodor Knacke and Helmut Heinrich and who still possessed an instinctive feel for how fabric reacts to extreme stress. Chuck Lowry, for example, counseled Clark to stick with the ringsail and use a webbing to reinforce the areas where the tear had occurred in the 2015 test. But Clark decided that he needed to maximize the odds that his next test would be a success; his top priority had to be accumulating fresh footage to analyze, as a small step toward making parachute design a more objective enterprise. And that meant accepting that his team should turn conservative and make their next parachute a DGB.
Clark would have to wait longer than expected to make and test that parachute. Citing a need to reallocate money to a program that repairs satellites, NASA slashed the supersonic decelerator’s funding by 85 percent in early 2016—a decision that led to the shuttering of the project before its planned third test. But Clark received a lifeline from Mars 2020, an upcoming mission to deliver a Curiosity-style rover to the Red Planet’s surface. The mission’s leaders were intent on sticking with the basic Viking design for their parachute, but they offered Clark the chance to fabricate his own version and, most important, test it in the atmosphere—an endeavor that would come to be known as the Advanced Supersonic Parachute Inflation Research Experiment, or Aspire.
Before Clark and a few handpicked collaborators got to fiddling with the Viking DGB, however, Mars 2020 wanted them to attempt something much more basic: Conduct an atmospheric test of the exact same parachute that Curiosity had used in 2012. If they could pull off that task, and thus end their two-test losing streak, they would then be given the resources to repeat the experiment with their own take on the design.
The first Aspire test—and perhaps Clark’s last shot at proving he could deploy a supersonic parachute—took place on October 4, 2017, at the Wallops Flight Facility, on the easternmost stretch of Virginia’s coastline. When a Black Brant IX sounding rocket reached an altitude of around 26 miles while screaming along at Mach 1.8, a built-to-print version of the Curiosity DGB came bursting out of its bag. The canopy snapped into shape and twisted counterclockwise in the ferocious wind. None of the engineers dared jinx the promising moment by celebrating prematurely, or even making the slightest sound.
“There was a lot of pressure on us to get this right,” Clara O’Farrell says. “The last time, it had been heartbreaking—we’d put all this effort into making changes, making the best parachute possible, and everyone’s hopes had gotten up before it failed.” This time, 20 seconds of silence passed before anyone in the control room felt comfortable enough to cheer.
It was by no means the glorious achievement the engineers had envisioned for themselves during the headiest days of the supersonic decelerator project; this DGB was just a retread from a past mission, not the parachute that would help land 10-ton vehicles safely on Mars. But they took pride in having accomplished something that hadn’t been done since before most of them were born. After so much frustration, they were finally a few inches past the starting line.
The next Aspire test, scheduled for March 20 at Wallops, will be far more ambitious than its predecessor. Clark and his colleagues have come up with a DGB that conforms to the basic Viking design but also features numerous clever tweaks that will hopefully increase drag without also increasing the odds of a catastrophe. The engineers worked with the company that sewed the parachute, Airborne Systems, to incorporate a new nylon that is three times stronger but only 50 percent heavier than the one Clark tore apart with his teeth for my benefit. And they also fortified the Technora suspension lines by changing the way their fibers are braided.
The footage that the forthcoming Aspire tests yield, shot by digital cameras capturing 1,000 frames per second at 4k resolution, could provide Clark with more insight into supersonic-parachute dynamics than the sum of all the vintage NASA documents he’s ever read. “At that level of detail I can see the entirety of the suspension lines, I can see inflections in the broadcloth, I can see shadows in the areas where the parachute is under stress and beginning to stretch out a little bit,” he says. (The 16-mm Viking films were shot at just 30 frames per second.)
Clark accepts that his efforts to comprehend the physics of supersonic parachutes could ultimately be for naught. Years of fleshing out his knowledge with increasingly expensive tests may lead him to conclude that decelerating, say, a 20-ton spacecraft full of astronauts on Mars requires a braking technology that doesn’t involve fabric—perhaps some combination of his inflatable decelerator and a fuel-powered engine. There are already some engineers who seem to be betting that the next age of Martian exploration will be parachute-free: SpaceX, for example, has discussed vague plans to use thrusters to land a large vehicle on Mars.
But supersonic parachutes will be given every chance to prove their viability for Mars because their efficiency cannot be beat. In the simplest terms, a hundred pounds of fabric will always provide exponentially more braking power than a hundred pounds of rocket fuel. And when designing a vehicle to make the 33.9-million-mile journey to Mars, saving half a ton of weight could spell the difference between a mission that ends in triumph and one that ends with a heap of twisted wreckage atop Olympus Mons.
Brendan I. Koerner (@brendankoerner) is a WIRED contributing editor. He wrote about theft from a Silicon plant in September.
