Packing For Mars (10 page)
The commanders were not simply entertaining themselves. The early aeromedical scientists studied the human tolerance limits for excess gravity in order to learn how to protect fighter pilots and, later, astronauts. Jet pilots are subject to as many as 8 or 10 G’s as they pull out of steep dives and execute other high-speed maneuvers. Astronauts endure a few seconds of double or triple gravity during liftoff, and as many as four and sometimes more extra G’s when their spacecraft reenters Earth’s atmosphere on the way down. Going from the airless vacuum of space into a wall of air molecules slows their craft from 17,500 to a few hundred miles per hour. As in any abruptly slowed vehicle, the occupants are hurled forward in the direction of travel. What’s dangerous about reentry is that the hurling—the period of doubled or quadrupled G forces—lasts for up to a minute, as opposed to the split-second duration of a car crash.
How many excess G’s the human body can tolerate without injury depends upon how long it’s exposed. For a tenth of a second, people can typically hack between 15 and 45 G’s, depending on what position they’re in relative to the force. When you get up into the range of a minute or more, tolerance drops alarmingly. Your heavy blood has enough time to pool in your legs and feet, depriving your brain of oxygen, and you black out. If it goes on long enough, you die. At 16 G’s, wrote John Glenn of his flight-training experience on the NASA centrifuge, “it took just about every bit of strength and technique you could muster to retain consciousness.” This is why astronauts lie down during reentry—so the blood doesn’t pool in their legs and feet. But on your back, you are the whale on the beach. There is pain beneath the breast-bone. Inhaling is a struggle. During a Soyuz reentry that went awry, ISS Expedition 16 commander Peggy Whitson endured an overly steep, overly fast reentry and a full minute in 8 G’s, about double the normal hypergravity of reentry. Astronauts are taught, on the centrifuge, how to deal with this—to take quick, shallow panting breaths so the lungs never fully deflate and to inhale using the stronger muscles of the diaphragm, not the smaller muscles attached to the ribs. Even then, Whitson found it a struggle.
The human arm weighs, on average, nine pounds. That means that for the duration of reentry, Peggy Whitson’s arm weighed 72 pounds. In the words of aerospace medicine pioneer Otto Gauer, “In general, only wrist and finger movements are possible above 8 G’s.” Meaning that an astronaut could perish because she can’t raise an arm to reach a control panel. Whitson plays down the dangers. But a few weeks after I spoke to her, I met a flight surgeon who showed me photographs taken shortly after the incident. She looked, to use his word, “wasted.” The next photo he showed me was of the crater in the dirt where the Soyuz capsule hit the ground. It looked like someone had tried to build a swimming pool out in the middle of the Kazakh Steppe.
Coming down is as scary as going up.
SPLASHDOWN
NASA Visits the Crash Test Lab
Crash simulation is a world comprised largely of metal and men. The simulator at Ohio’s Transportation Research Center resides in a clanging, hangar-sized room with few places to sit, and none of them upholstered. The room holds little beyond the crash sled, on a track down the middle, and a few engineers in safety goggles, forever walking back and forth with coffee mugs. Other than the reds and oranges of warning lights and hazard signs, color is hard to find.
The cadaver seems almost a homey touch. Subject F wears blue Fruit of the Loom underpants and no shirt, as though he were lounging around in his own apartment. He looks deeply relaxed. As dead men do. Are. He slumps slightly in his chair and his hands rest on his thighs. Were F alive, he would not be so relaxed. In a few hours, a piston as fat as a redwood will shoot a slug of pressurized air at the seat in which he’ll be strapped. Both the force of the impact and the position of the seat can be adjusted to create whatever crash scenario a researcher requires: a head-on into a wall at 65 miles per hour, say, or one car broadsiding another going 40. Today it’s NASA’s new Orion capsule, dropping from space onto the sea. F gets to play astronaut.
In a space capsule, every landing is something of a crash landing. Unlike a plane or the Space Shuttle, a capsule has no wings or landing gear. It doesn’t fly back from space; it falls. The Orion space capsule has thrusters that can correct its course or slow it down enough to drop it from orbit, but not the kind that can be fired to soften a landing. As a capsule reenters the Earth’s atmosphere, its broad bottom plows into the thickening air; the drag slows it down to the point where a series of parachutes can open without tearing. The capsule drifts down to the sea, and if all goes well, the touchdown will feel like a mild fender-bender—2 to 3 G’s, 7 at most.
Touching down on water rather than earth makes for a gentler landing. The trade-off is that oceans are unpredictable. What if a cresting wave slams into the capsule as it’s coming down? Now the occupants need restraints that protect them not only against the forces of being dropped straight down, but also against a sideways or upside-down landing impact.
To be sure Orion’s occupants are unhurt no matter what wild card the seas present, crash test dummies and, lately, cadavers have been taking rides in an Orion seat mock-up here at the Transportation Research Center. The landing simulations are a collaboration involving the Center, NASA, and Ohio State University’s Injury Biomechanics Research Laboratory.
F sits on a tall metal chair beside the piston track. Graduate student Yun-Seok Kang stands at his back, using an Allen wrench to mount a wristwatch-sized block of instrumentation on an exposed vertebra. Along with strain gauges glued to various bones on the front of the body, these instruments will measure the forces of the impact. Scans later this evening and an autopsy will reveal any injuries caused by that force. Kang was up late with yesterday’s cadaver and in early this morning, but he’s alert and cheerful. He has one of those happy, high-achieving personalities that self-help programs promise but rarely manage to create. He wears rectangular glasses and long bangs that march around to the sides of his head. His gloved fingers are glossy with fat. The fat—because it’s slippery and because there’s a fair amount of it—makes Kang’s task difficult. He has been working on this mount for more than half an hour. The dead are infinitely patient.
F will be taking a hit on his lateral axis. Picture a foosball figurine—the little wooden soccer player with the skewer run sideways through his rib cage. That skewer is the body’s lateral axis. Say the foosball man goes for a drive, and another car T-bones his car at an intersection. His body and organs, if he had any, would be accelerated to the left or right along that skewer. In a head-on crash or a rear-ender, they’d be accelerated along the transverse axis: from front to back, or vice versa. The third axis that researchers consider is the longitudinal—along the spine. Here the foosball player is operating a helicopter. It stalls and drops straight down to the ground. Foosball man’s heart stretches down on its aorta like a bungee jumper. Should have stuck to sports.
Because astronauts are reclining on their backs during touchdown, a space capsule hitting the ocean in calm conditions creates a force on the transverse axis—front to back—by far the body’s most durable. (Lying on their backs, fully supported and restrained, they can tolerate three to four times as much G force—a tenth of a second of up to 45 G’s—as they could seated or standing, wherein the more vulnerable longitudinal axis takes the strain.)*
Crashes often involve forces along not just one axis, but two or three of them. (Though simulations study just one at a time.) Add high seas to the capsule touchdown equation, and now you have to consider forces along multiple axes. A useful model for the kind of impact NASA must plan for—multiaxis and unpredictable—is the race-car crash. The week I visited Ohio, NASCAR’s Carl Edwards, traveling at close to 200 miles per hour, slammed another car, launching his own high into the air, where it spun like a flipped quarter before slamming down into the wall. Whereupon Edwards casually got out and jogged away from the wreckage. How is this possible? To quote a recent Stapp Car Crash Journal paper, “a very supportive and tight-fitting cockpit seating package.” Note the word choice: package. Safeguarding a human for a multiaxis crash is not all that different from packing a vase for shipping. Since you don’t know which side the UPS guy’s going to drop it on, you need to stabilize it all around. Race-car drivers are strapped tightly into custom-fitted seats with a lap belt, two shoulder belts and a crotch strap to keep them from sliding down under the lap belt. A HANS (Head and Neck Support) device keeps the head from snapping forward, and vertical bolsters along the sides of the seat keep the head and spine from whipping left or right.
Dustin Gohmert, a NASA crew survivability expert, has spent a lot of time talking to the people who design restraint systems for race cars. He and two colleagues have traveled from the Johnson Space Center to oversee the simulations this week. Gohmert has agreed to answer some questions while Kang and three other students finish instrumenting F. Gohmert has blue eyes and black hair and a lively Texas wit that he mostly sets aside while speaking into a tape recorder. He sits straight-backed and motionless while answering my questions, as though merely talking about upper torso restraints is holding him still in his chair.
Early on, NASA had dismissed race-car seats as models for Orion. For one thing, race-car drivers are sitting up, not reclining. Bad idea for astronauts who’ve been in space for a while. Lying down is not only safer (provided you don’t have to steer); it keeps astronauts from fainting. Veins in the leg muscles normally constrict when we stand, to help keep blood from pooling in our feet. After weeks without gravity, this feature stops bothering to work. Compounding the problem is the fact that the body’s blood volume sensors are in the upper half of the body. Where, without gravity, more of the body’s blood tends to pool; the sensors misinterpret this as a surplus of blood, and word goes out to cut back on production. Astronauts in space make do with 10 to 15 percent less blood than they have on Earth. The combination of low blood volume and lazy veins makes astronauts lightheaded when they return to gravity after a long stay in space. It’s called orthostatic hypotension, and it can be embarrassing. Astronauts have been known to faint during postmission press conferences.
There is a problem with lying on your back in a spacesuit in a very safe seat: “We threw a racing seat on its back, put a guy in it, and said, ‘Can you get out?’” recalls Gohmert. “It was like putting a turtle on its back.” Some months back, I watched a horizontal egress (getting out of the capsule) test of a suit prototype at Johnson Space Center. The verb “to turtle,” as in “I’m kind of turtling out,” was in fact used.
Getting out fast is mainly a concern when something goes wrong: The capsule is sinking, say, or it’s on fire. The last time things went wrong aboard a space capsule, it was the Soyuz capsule, returning to Earth with members of the ISS Expedition 16 and 17 crews, in September 2008. (NASA has been paying the Russian Federal Space Agency to fly ISS crews home when no space shuttle is available.) The Soyuz module entered the atmosphere out of position—as it had with Boris Volynov aboard in 1969. This interfered with the aerodynamic lift that normally helps flatten its course and gentle its reentry and landing. Reentry subjected the crew to a full minute of 8 G’s—rather than the customary peak of 4 G’s—and a landing bump of 10 G’s. The capsule landed far afield of its targeted landing site, in an empty field on the Kazakh Steppe, where sparks from the impact started a grass fire.
The Soyuz seats, like race-car seats, have side restraints along the head and the length of the torso. Which makes them safer, unless you need to get out in a hurry. “I had it all planned out,” Expedition 16 commander Peggy Whitson told me in a phone interview. “I’m thinking, ‘I’m going to unstrap and brace my hand here, and then lower my feet,’ and of course none of that worked out. I just fell to the bottom with my head and shoulders in So-yeon’s seat and my legs up and across the hatch.” Gravity was not helping. “After six months, you forget how heavy things are. Like, yourself.” You also, after months of weightlessness, forget how to use your legs. “Your muscles don’t remember what to do.” And astronauts have no pit crew to rush over and help them free of the wreckage.* Fortunately, the wind was blowing away from them and the grass fire soon burned itself out.
Worried that NASCAR-style shoulder bolsters might dangerously extend the time it takes an astronaut to get out of the capsule, Gohmert and his colleagues ran some simulations with head bolsters only. For these they used crash test dummies—or “mannequins,” as Gohmert calls them, causing me to picture them taking their hits in department store outfits. It was a bad business. Gohmert described the slow-motion video footage to me. “The head stayed stationary and the body kept moving. We were actually concerned about the mannequin being okay.” As a compromise scenario, the shoulder bolsters are still there but have been scaled down.
NASCAR seats are fitted to each driver, but that’s too expensive to do for each astronaut. The Soyuz seats employ a compromise: a molded seat insert fit to each cosmonaut’s body. But the mold still has to fit inside the seat, which ultimately limits the size of the cosmonaut. “The Russians have a much narrower range of crew sizes,” Gohmert says wistfully. At the time we spoke, seats (and suits) were required to fit bodies that fall anywhere between 1st percentile female to 99th percentile male. That’s 4 feet 9 to 6 feet 6, though standing height is the least of it. A seat system that supports and restrains the entire seated body has to fit buttock-knee lengths from 1st to 99th percentile, and ditto seated chest heights, foot lengths, hip breadths, and seventeen other anatomical parameters.*
This wasn’t always the case. Apollo astronauts had to be between 5 feet 5 and 5 feet 10. It was a simple, inflexible cutoff, the governmental version of the sign by the amusement park ride: MUST BE THIS TALL TO RIDE. That meant that a lot of otherwise qualified candidates were kept out of the space program because of their stature. To today’s PC-sensitized mind, that smacks of discrimination.
To Dustin Gohmert, it smacks of common sense. As things stand, NASA has to spend millions of dollars and man-hours making seats lavishly adjustable. And the more adjustable the seat, generally speaking, the weaker and heavier it is.
A further complication for the astronaut, as opposed to the race-car driver: He’s got vacuum cleaner parts attached to his suit*—hoses, nozzles, couplings, switches. To be sure the hard parts of a suit don’t injure the soft parts of an astronaut in a rough landing, F will be wearing a suit simulator: a set of rings duct-taped in place around his neck, shoulders, and thighs. The rings are facsimiles of the mobility bearings, or joints, of a spacesuit. (Tomorrow’s cadaver, presently thawing,† will be wearing a vest with “umbilicals”—life support hoses and couplings—mounted on it.) One specific concern today is whether, on a sideways touchdown, a mobility bearing might collide with the seat’s shoulder bolster and be driven into the astronaut’s arm with enough force to break a bone.*
Gohmert explains how ring joints work, how they enable an astronaut to raise an arm. A pressurized spacesuit is a heavy-duty body-shaped balloon—almost more of a tiny inflated room than an article of clothing. Fully pressurized, it’s all but unbendable without some sort of joints. The current suit prototype has metal shoulder rings that twist back and forth against each other, enabling astronauts to rotate their entire arm up and down, like old-fashioned doll arms. This is my analogy, not Gohmert’s. Earlier in the conversation, I likened NASA’s differently sized, individually selected spacesuit components to the recent development of mix-and-match bikini bottoms and tops. “I haven’t bought one,” Gohmert was careful to point out, “but that sounds right.”
JOHN BOLTE ISN’T 99th percentile, but he’s pretty big. When he drove my crappy little rental car, I swear he had to hunch forward over the steering wheel to fit in it. He was reading texts as he drove, getting updates on the score of his older son’s ball game. I was relatively certain that if he ran off the road, the car would crumple around him and he’d step from the wreckage unfazed, going “Bottom of the eighth, nine to three!”
Bolte has just arrived from OSU, where he runs the Injury Biomechanics Research Laboratory. He’s here to check his students’ work and to help with last-minute preparations before the piston fires. He wears hospital scrubs and a backward baseball cap. He is helping to dress F, pushing the dead man’s fist through the bunched-up sleeve of a long-underwear shirt, a task he likens to dressing his five-year-old.
Now the challenge is to get F into the seat on the sled. Think of wrestling a comatose drunk into a taxicab. Two students hold F’s hips, and Bolte has his hands beneath F’s back. F lies on his back with his bent legs raised, like a man whose dinner chair has tipped over.