A body in vacuum: boiling saliva, 14 seconds awake, the human thermos
In 1966, a NASA technician accidentally found himself in a near-total vacuum, and the last thing he remembered before blacking out was the saliva boiling on his tongue. That has to be the most terrifying thing I've ever heard. I'm Salt. I'm Grace. He survived it, surprisingly.
But his accident proves that the movies have been lying to us for decades about what happens if you take off your helmet in space. Right, you either turn into an ice cube instantly and shatter, or you just, um, explode like a balloon. Neither of those happens. You do not explode, and you don't flash freeze. Space is just a ridiculously good insulator.
Wait — what? Yeah. Because a vacuum's empty. Heat needs a physical medium to travel through, say air or water, to do conduction or convection. Out there, there's just no stuff to carry the heat away from you, so you only lose it through thermal radiation.
Okay, so how fast are we talking? It's slow. Your body radiates heat at a rate of about 100 Watts, which is roughly the same as an old incandescent bulb. Forbes ran the math on this in 2019, and it'd take hours for a human body to freeze solid. You're sort of floating in a giant thermos.
That makes sense, but what about the exploding part? If the pressure drops to zero, shouldn't all the gases in your body push outward? You do swell up a bit. The Wikipedia page on ebullism notes you'd puff out to maybe twice your normal size, which sounds bad, but your skin is incredibly tough. It acts like a biological pressure suit that holds your organs together.
And your circulatory system keeps your blood pressurized enough so it doesn't boil inside your veins. But something boils. You mentioned the saliva at the start. Yes. Dr.
Harry G. Armstrong defined this back in 1947. It's called the Armstrong Limit. If pressure drops below 6. 3 kilopascals, any moisture exposed to the vacuum — your eyes, your lungs, your tongue — will boil at normal body temperature.
That sounds awful. So who was the NASA guy who felt this? Jim LeBlanc. December 14, 1966. He was testing a space suit at — he was in a vacuum chamber at NASA's Houston facility, and the pressurization hose disconnected.
Oh, wow. And he was just stuck in the suit with no air? The chamber dropped to 0. 1 psi. Basically a near-vacuum.
He was unplugged from his umbilical, and he said he felt the saliva boil on his tongue, and then he just just lost consciousness in 14 seconds. Fourteen seconds. Is that just how long it takes for the oxygen in your blood to run out? It's how long it takes for the deoxygenated blood to travel from your lungs up to your brain. Which brings us to the one thing you must never do if you're ever thrown out an airlock.
Do not try to hold your breath. Because your lungs would pop. Exactly. The expanding air in your lungs will tear the tissue instantly. It causes fatal pulmonary barotrauma.
You have to exhale. Grace, I gotta ask. You exhale, you pass out in 14 seconds. How long do you have before it's over? The window is, um, surprisingly wide.
In April 1965, the Air Force and NASA published a joint study where they decompressed 126 dogs to a near-vacuum. Seriously? 126 dogs. Yeah. They found that if they repressurized the chamber in under 120 seconds, the dogs survived.
There was, like, no permanent neurological damage. That's — two whole minutes. I'd have guessed ten seconds. Have humans ever been exposed that long? Only once, tragically.
The Soviet Soyuz 11 mission on June 30, 1971. I think I read about this. They were coming back down to Earth, right? Yeah, three cosmonauts. They were descending at 168 kilometers when a cabin valve that was supposed to — a valve that was meant to open much lower down just jolted open in the vacuum of space.
It vented all their air while they frantically tried to find the leak and plug it by hand. And they couldn't reach it? Not in time. As the Russian Space Web archives detail, the decompression took 112 seconds. It was fatal for all three.
So they were right at that two-minute edge from the dog study. They were. But the the difference is, the cosmonauts were awake. They were, you know, exerting themselves trying to close the valve while the pressure dropped, and they couldn't get it shut. That's a rough way to go.
It really is. But it proves the absolute limit. You you have a few seconds of useful consciousness. And there's, uh, a ninety to a hundred second window before the damage is permanent. It makes you respect the human vessel.
Like, we're built to survive on Earth, but our skin and our blood pressure buy us this tiny window in the absolute worst environment possible. They do. And aerospace engineers still study those same limits when designing the emergency protocols for the next generation of space suits. Huh. Thanks a lot for listening to Daybrain.
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