Mary Roach - Packing for Mars

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.

The piston is off to F’s right; he’ll be impacted along his lateral axis. “Lateral crashes are very deadly because…” Gohmert stops. “I shouldn’t say crash.” “Landing pulse” is the preferred NASA phrasing. (NASCAR is partial to “contact.”) “NASA must train these guys,” Bolte marveled at one point. “You ask them a question and you see them pause and think through their answer.” Bolte isn’t like that. My favorite line of the day so far has been Bolte’s: “Is he leaking badly from anything major?”

What’s so deadly about lateral “pulses”? Diffuse axonal injury. When an unsecured head whips from side to side, the brain gets slammed back and forth against the sides of the skull. The brain is a smushable thing. It alternately compresses and stretches out as this happens. In a lateral impact, as opposed to a head-on, the stretching pulls on the long neuron extensions, called axons, that connect the brain’s circuits across the two lobes. The axons swell, and if they swell too much, you may go into a coma and die.

A similar thing happens to the heart. A heart, when it’s full of blood, can weigh a good three-quarters of a pound. In a side impact, as opposed to a head-on, there’s more room for it to whip back and forth on the aorta. [37] How much does it move? Enough that you can sometimes feel it. In one Apollo-era study of sudden deceleration (stopping fast), five out of twenty-four subjects complained of what the researcher called “abdominal visceral displacement sensation.” If the aorta stretches far enough and the heart is heavy with blood at that moment, the two may part ways. “Aortal severation,” as Gohmert put it. This happens less often in a head-on collision, because the chest is relatively flat in that direction; the heart is more sandwiched in place. Hearts also come off their stalk in longitudinal impacts, like those that happen in helicopter drops, because there’s lots of room for them to pull downward and exceed the limits of the aorta’s stretch.

F is finally ready. We’ve moved upstairs to watch the action from the control room. A bank of overhead lights comes on with a dramatic phumph. The actual impact itself is anticlimactic. Because it is air [38] Does this sound gentle? It is not. Recall Javier Bardem in No Country for Old Men . If you missed the film, think of pork workers described in a MedPage Today article as using jolts of compressed air to force pig brains out of heads. “This ‘emulsifies’ the brain tissue,” explained a source. that’s doing the impacting, sled tests are unexpectedly quiet, crashes without a crash. And they are fast, too fast for the eye to register much of anything. The video is shot at ultrafast speed, so that it can be played back in extremely slow motion.

We all lean in to see the screen. F’s arm bends up underneath the shoulder bolster, the space where the rib bolster had been removed. The arm appears to have an auxiliary joint, bending where arms shouldn’t bend. “That can’t be good,” says someone. This has been a recurring problem. As Gohmert puts it: “Gaps in the seat tend to get filled in by body parts.” (The arm will turn out not to be broken.)

F endured a peak impact of 12 to 15 G’s—right on the cusp of injury. Gohmert explains that the extent of an accident victim’s injuries will depend not only on how many G’s of force there were, but on how long it takes the vehicle to come to rest. If a car stops short the instant it hits a wall, say, the driver may endure a split-second peak load of 100 G’s. If the car has a collapsing hood—a common safety feature these days—the energy of those same 100 G’s is released more gradually, reducing the peak force to maybe 10 G’s—highly survivable.

The longer it takes the car to stop moving, the better—with one dangerous exception. To understand it, you need to understand what is happening to a body during a crash. Different types of tissue accelerate more quickly or slowly, depending on their mass. Bone accelerates faster than flesh. Your skull, in a lateral impact, leaves your cheeks and the tip of your nose behind. You can see this in a freeze-frame of a boxer’s face [39] And in the paper “Voluntary Tolerance of the Human to Impact Accelerations of the Head.” Eleven subjects, at least one of them dressed in a suit and tie, received blows to the head with 9-and 13-pound pendulums. As the authors put it: “Considerable distortion of the face was observed as the bony structure of the head was accelerated away from the softer portions.” We owe these men a debt of thanks. In the early investigations of head impact, a cadaver was of limited help. You couldn’t ask him to count backward by sevens or name the president, and you’d never know what sort of headache he had. as he’s punched in the side of the head. In a head-on, your frame gets moving first. It’s hurled forward until it’s stopped—by the shoulder belt or by the steering wheel—and then it rebounds backward. A fraction of a second later than your frame began moving forward, your heart and other organs depart. This means that as the heart is launched forward, it collides with the ribcage on its journey back the other way. Everything’s moving forward and back at different rates, colliding with the chest walls and rebounding. And all of this is happening within a few milliseconds. So fast that bouncing and rebounding are the wrong words. Things are vibrating in there.

The big danger, Gohmert explains, is if one or more of those organs starts vibrating at its resonant frequency. This will serve to amplify the vibrations. When a singer hits a note that matches the resonant frequency of a wine glass, the glass starts to vibrate more and more energetically. If the note is sung loud enough and sustained for a long enough time, the glass will shake itself apart. Recall, if you are old like me, the Memorex ads with Ella Fitzgerald and the exploding wine glass. The same sort of thing can happen to an organ that hits its resonant frequency in a crash. It can shake itself off its moorings. And worse. “Essentially,” said Gohmert, after repeated wheedling for specifics, “you’re churned to death.”

You may be wondering: Could Ella Fitzgerald explode your liver? She could not. Glass has a relatively high resonant frequency, up in the audible sound wave range. Body parts resonate down in the long, inaudible wavelength range called infrasound. A launching rocket, on the other hand, creates powerful infrasonic vibration. Could those sound waves shake apart your organs? NASA did testing on this back in the sixties, to be sure, as one infrasound expert told me, “that they didn’t deliver jam to the moon.”

Bolte’s students are sliding F onto a stretcher and loading him into the back of a white van. He’s traveling to the OSU Medical Center where he’ll be scanned and X-rayed. The whole procedure will unfold exactly as it would with a live patient, right down to a forty-five-minute wait and a problem with the billing.

Gohmert’s gaze rests on F. It is hard to read his look. Is he uncomfortable with having had to impact a human body? He turns to Bolte. This I didn’t see coming. “Do you ever put ’em in the front seat and take ’em through the HOV lane?”