posted
Okay, I've got a bit of a science question for those more knowledgable than myself. (It actually has to do with a Trek story that I'm writing, but I figure on getting some real science figures if possible. )
I've got a closed shell, at least 650 meters long and 300 meters in diameter, filled with a breathable atmosphere at normal pressure... (The concept is an enclosed, pressurized drydock for starships, so that engineers can work without spacesuits.)
The question is, if the doors open with the air still inside, what kind of danger would the explosive decompression pose to the structure itself? I'm thinking that it would (at the least) act like a kind of rocket, propelling the structure in the opposite direction of the escaping air. But if you're considering such a huge volume of air (more than a cubic kilometer), would the sudden escape actually pose a risk of breaking the shell itself? I'm thinking of unequal forces or something of that regard... but I'm not familiar enough with the principles to know for certain.
If anyone knows more about this, could I have a few pointers?
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Registered: Nov 2000
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Cartman
just made by the Presbyterian Church
Member # 256
posted
How large are the doors? And what is the tensile strength of the shell's hull material?
Registered: Nov 1999
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posted
Doesn't really matter. If your structure is sufficiently designed to contain the pressures inside, it shouldn't cause a problem with all the flow exiting through the door. "Theoretically" the velocity of the flow at the door frame would be 0 anyway.
Registered: Mar 1999
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posted
Well, how strong is the shell? If it's strong enough, it won't break. If it's not, it will. If I were going to work inside the thing, I would hope it would be strong enough.
As for movement, IIRC, the force of the air going out would create an equal force pushing the structure the opposite way. However, depending upon the mass of the structure, and what motion it already has, the effect may or may not be negligible.
Registered: Mar 1999
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posted
Also you'd have to secure any loose objects... (not really answering the question, I know but still). Heavy items of eqipment could cause some damage, I'd imagine.
-------------------- "I am an almost extinct breed, an old-fashioned gentleman, which means I can be a cast-iron son-of-a-bitch when it suits me." --Jubal Harshaw
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OnToMars
Now on to the making of films!
Member # 621
posted
C.
Always pick C when you have no idea.
-------------------- If God didn't want us to fly, he wouldn't have given us Bernoulli's Principle.
Registered: Jun 2001
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Since this is a Trek setting, I guess we can say that it's transparent aluminum or something equivalent.
I figured the doors would be as large as the end of the shell itself, since a ship needs to fit in, and it would be rather counterproductive to have a ship that could fit inside but can't get through the doors.
I suppose the structure would be strong enough -- after all, most doorways don't break when there's a hull breach or something; in all the shows we just see the air rushing through the available space.
I'm mainly wondering because it's such a large volume of air, and is sealed against a vacuum. I guess it's like letting the air out of a balloon -- it might pop outright, or it might just let the air out. I'm thinking that some damage could be done given such a huge volume of air, even if it's a metal frame.
-------------------- “Those people who think they know everything are a great annoyance to those of us who do.” — Isaac Asimov Star Trek Minutiae | Memory Alpha
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Movies would have us believe that an airplane cabin pressurized to 1 atm would suddenly be sucked out (along with the entire contents of the cabin) when a hole the size of a dinner plate is suddenly opened to the outside air at 30,000 feet. The effects are shown to be even worse if the outside atmosphere is zero pressure.
But does this really happen? Intuitively, the pressure of 1 atm (14.7 pounds per squre inch or 101,325 pascals, or newtons per square meter) is applied equally to the entire surface of the structure. When a hole is opened, the air is pushed out at a pressure of 1 atm. Movies show the effects to be much worse, but in airplanes I think that has a lot to do with the fact that the plane is moving at a couple hundred miles per hour. If it's vessel is not moving relative to the outside, how bad is it?
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Registered: Oct 1999
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posted
No, the air wouldn't escape, since a force field would hold it in ala shuttle bay....
-------------------- "You are a terrible human, Ritten." Magnus "Urgh, you are a sick sick person..." Austin Powers A leek too, pretty much a negi.....
Registered: Sep 2000
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Ritten, I suppose a forcefield is possible (after all, this is a fictional universe!) but I think that given the TNG-era technology, flying an entire starship through a forcefield is kinda unlikely. Or at the very least, impractical due to power requirements.
(Besides, I'm actually TRYING to create problems here. It's really just a small point in the story, but the point is that the ship inside the drydock is getting its hull repaired/upgraded and they're using a specialized enclosed/pressurized facility to speed up the process. The problem, though, is when an emergency occurrs and they need to leave the dock ASAP. I'm trying to consider the potential consequences of rapid depressurization -- forcing the ship to hold off the launch until it's safe to open the doors. But I'm not too attached to the idea, so I wanted to try to get some of the facts to make it more believable.)
-------------------- “Those people who think they know everything are a great annoyance to those of us who do.” — Isaac Asimov Star Trek Minutiae | Memory Alpha
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