Explosive Decompression and Artificial Gravity

[Eternal_Freedom]

So we all know that explosive decompression in a spacecraft or an aeroplane is a very bad thing. All the air rushes out into vaccuum, and so does anything that's not died down, including, potentially, the crew (unless they hold on to something.

But...if a ship has artificial gravity, would the escaping atmosphere have enough force to (as we see in films and TV) lift someone off their feet and launch them into space? I mean, unless the artificial gravity fails when the hull is breached there is still a 1 g force pulling them to the floor. So would you really be sucked/blown out into space?

[Borgholio]

Well people in an airplane can still be sucked out of a big enough hole, despite being under 1g of gravity. I think on a ship / station with artificial gravity, it would depend on how big the hole is and how close you are to it.

[Eternal_Freedom]

True. It came to mind re-watching Star Trek Into Darkness. You see a bunch of crew sucked into space from enemy fire. You also have that security guard in the hanger who is pulled out of a small hatch at the other end of a large hanger as soon as the door opens and is lifted into the air in the process. That seems the most glaring instance I can think of.

[Borgholio]

Yeah that was Hollywood in action. While being in an de-pressurizing shuttlebay would not be a good thing, I don't think it would have fully sucked the guy out. Knocked him down sure, but the wind shouldn't have been THAT strong.

[Lord Revan]

True. It came to mind re-watching Star Trek Into Darkness. You see a bunch of crew sucked into space from enemy fire. You also have that security guard in the hanger who is pulled out of a small hatch at the other end of a large hanger as soon as the door opens and is lifted into the air in the process. That seems the most glaring instance I can think of.

the holes blasted By the Vengence were big enough to drive a shuttle thru them (or at least looked like it) certainly at least the size of a door or a hatch that other hatch seemed too small to suck enough air to pull a fairly large man thru it though.

that said shouldn't 1g AG keep the air on it's place since planets with less then 1g gravity have atmosshares (Venus' being even thicker then Earth's IIRC)

[Borgholio]

It would be a matter of having a pressurized environment at ~14psi vs space at 0psi. I think the pressure gradient would overpower gravity. But maybe one of our resident engineers could run the actual math?

[Darth Nostril]

That said shouldn't 1g AG keep the air in place since planets with less then 1g gravity have atmospheres (Venus' being even thicker then Earth's IIRC)

As Borgholio said explosive decompression in an aircraft can suck people out, even though they are in 1g and the aircraft is not even in a vacuum.
The pressure differential is what counts, never underestimate the sheer power of air moving very fast - tornadoes and hurricanes can literally rip entire buildings from their foundations and smear them across the nearby landscape.

[Darmalus]

Well, according to wikipedia an average man has a surface area of 1.9 square meters, so if they were standing with 1 atm on one side and 0 atm on the other, they'd have a surface area of 1472 square inches with 15 psi on them. That's 22,080 pounds or 11 tons of force. It'd be less under realistic circumstances, but the pressure gradient here isn't anything to be sneezed at.

[Darth Nostril]

Not that it really matters anyway, even if the grav plates magically stick their feet to the floor, because all the breathable air just got sucked out into space and they asphyxiate.

[Broomstick]

It all depends on how fast the air leaves.

Unlike some movies, if there's a small hole all the air can't get out at once and you have a slow decompression. That actually happened to Mir back when it was still orbiting. Everyone survived, no "explosive" force, just a slow, albeit very serious leak.

If you blast something a couple meters across into something the size of a large room or airplane hangar, though, essentially removing a wall, all the air can leave at once, and will. As noted by Darmalus, the force then exerted upon a human body would far exceed the ability of a human being to hold on to something or otherwise resist it.

Gravity, whether due to a large mass or due to controlled spinning, is only going to exert a few tens of kilograms of force onto a human body. We measure that force every time we weigh something. The force exerted by 1 atmosphere of pressure against a human body standing between that air and vacuum is a couple orders of magnitude greater. No, gravity will not save you from being sucked out into space under those circumstances.

If you really want a lesson in what atmospheric pressure differentials can do when cranked up even further check into the 1983 Byford Dolphin Accident. Some of the details are quite gruesome. Well, at least it was quick.

[Sea Skimmer]

Explosive decompression technically means it occurs so fast the lungs can't empty themselves being expanding violently, often causing injury like an explosive blast would, though sort of in reverse in terms of body movement. This is a pretty high threshold, a fraction of a second, and most events called explosive decompression are not. Anything that violent is going to be suck you out the hole level force, no question.

[Lord Revan]

It would be a matter of having a pressurized environment at ~14psi vs space at 0psi. I think the pressure gradient would overpower gravity. But maybe one of our resident engineers could run the actual math?

I now that enough over pressure would over come the force of gravity but considering that Earth itself has nothing but the force of gravity holding the atmosshare in place yet it stays there and at the 1 atmo also I'm pretty sure no starship I know of had signifigantly high internal pressure then the surfuce presure of Earth.

[Broomstick]

If I recall, pressure in real life space ships range from the minimum required pressure to function in a pure oxygen atmosphere, I think something like 3 psi, to 14-15 psi (standard atmosphere). But there's no reason to go higher than that.

[Irbis]

I now that enough over pressure would over come the force of gravity but considering that Earth itself has nothing but the force of gravity holding the atmosshare in place yet it stays there and at the 1 atmo also I'm pretty sure no starship I know of had signifigantly high internal pressure then the surfuce presure of Earth.

You're not thinking three-dimensionally. The atmosphere is kept in place by weight of all the atmosphere above it. That's why it thins, because at the top nothing is keeping it pinned, instead of having straight density through. The 1 atmosphere is just a function of how much gas on Earth there is, nothing more. Titan has much denser atmosphere than ours despite being far smaller.

If I recall, pressure in real life space ships range from the minimum required pressure to function in a pure oxygen atmosphere, I think something like 3 psi, to 14-15 psi (standard atmosphere). But there's no reason to go higher than that.

One reason to keep overpressure can be safety. The higher pressure, the longer time you have to plug the leak. Another - hmm, workout? Bigger pressure means more energy used to move and breathe, maybe someone would find that beneficial?

[Simon_Jester]

Higher pressure means it takes more time for a leak of fixed size to evacuate the entire pressurized volume... but the increase in pressure is likely to produce a less-than-linear response in terms of how long it takes to depressurize, if the partially-helpful equations I've found are correct.

[Could be wrong about this]

One thing I do know is that greatly increasing the internal pressure of a spacecraft means greatly increasing the stress on the hull. Sure, doubling the atmospheric pressure from 50 kPa* to 100 kPa** means it takes less time for all the gas to leak out... but it also means that there's twice as much force being exerted on the hull, pushing it outward. If a crack does start, the increased force on the wall makes it more likely for the crack to spread and cause a catastrophic failure of the hull.

*About half sea level air pressure
**Close to sea level air pressure

[Korvan]

The whole being sucked out into space won't happen as it is depicted in movies. Our local football stadium used to have an inflatable dome and was kept at partial pressure. You'd enter through a system of double doors like an air lock. At the end of a game though, to get people out faster, they'd just open up some large doors. Even a foot away, you don't feel a breeze, but once you step into the threshold, it feels like you're in a car wash dryer and you're pushed out of the building with some force. Now I think we're only talking about a 0.1 atm difference, so a full atmosphere differential could be felt further away, but nothing near like you see in the movies. Probably would make a difference if you're in a narrow corridor as apposed to a large chamber.

[Darth Holbytlan]

A quick check on Wikipedia shows that the extra pressure in a typical inflatable dome doesn't exceed 0.1 psi. The pressure differential between empty space and a fully pressurized capsule is 150x larger than that. Your experience at the local football stadium isn't comparable.