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Is "Hollywood-style" decompression accurate?

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Don't get me wrong, I like a good decompression scene as much as the next guy: people and garbage flying around, screaming, bodies ejected into space to become Popsicles ... and, if it's a big-budget Hollywood flick, you can bet on some badass CGI.

 

However...

 

Would it really happen that way... really?

 

Wouldn't the difference in pressure be 1 atmosphere to 0 atmospheres?

 

Heck, I'm not the physics guy, but I'd love it if someone could explain to me if what we see all the time on the big screen is even halfway "realistic."

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Re: Is "Hollywood-style" decompression accurate?

 

The scenario you describe is, of course, quite overblown. You'd likely have a similar scenario, only much less dramatic.

 

Of course, it depends on what's causing the decompression. If you have a hole the size of your finger, you'll have a rush of air that should be plugged soon but no real crisis beyond the loss of atmosphere. On the other hand, if half a wall blows out, you'll have everything rushing around like that but it'll only last a second or two.

 

I wrote rules for explosive decompression for The Ultimate Vehicle, though they actually ended up on pages 285-286 of Star Hero (with considerable revision on Steve's part -- I think he took the principles I started with and made the actual rules much smoother and easier to understand).

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Re: Is "Hollywood-style" decompression accurate?

 

Well, about bodies blowing up and blood boiling (I thought thats what the title meant you wanted to know) see http://www.straightdope.com/classics/a3_147.html

 

Read The Straight Dope it'll get a lot of BS out of your head. ;)

 

How fast the wind depends on pressure difference and size of hole, how long it blows depends on wind speed and how much air there is to dump, a BIG space ship or space station could have wind for a long time.

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Re: Is "Hollywood-style" decompression accurate?

 

When I watched the movie Aliens (an excellent film overall), and I got to the decompression scene there, I had some issues with it. The cargo hatch is at least two by two meters, probably more like three by three. Despite this huge hole, the airflow goes on for tens of seconds. I found myself asking, "what, is EVERY SINGLE DOOR AND HATCH on the entire SHIP open?"

 

The speed of air moving through an opening into a vacuum will be about equal to the speed of sound in air of whatever pressure it is. With a barn-door sized opening, you'll run out of air reeeeaal fast. With a pea-sized opening, you'll have plenty of time to fix it, unless you're in a space the size of a closet, I guess. With a pinhole, you won't even notice right away . . . from what I hear, a temperature drop will be your first clue.

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Re: Is "Hollywood-style" decompression accurate?

 

Disclaimer: I'm not an expert on this subject, so don't quote me.

 

Major issue for anyone unlucky enough to be caught in a decompression will be the lack of oxygen. Presuming one had no warning, the victim will have about 15 to 30 seconds of consciousness and mobility before passing out due to oxygen deprivation. If the environment is lower pressure / high oxygen content, opt for the high end of the scale.

 

Next major issue is the bends, especially if it is an earth standard atmosphere. Nitrogen bubbles in the blood will cause debilitating pain (presuming the victim can get oxygen without a suit) long after the decompression (and will have other detrimental effects since most space environments don't have a decompression chamber, though a sophisticated airlock might do).

 

One issue I've always had a problem with is the suction from the blowout lifting people from a full gravity environment (The Black Hole and Total Recall movies were the worst). I think inertia issues, if nothing else, would prevent this from happening.

 

Things turning inside out due to pressure differences? Doesn't happen when we bring stuff up from the bottom of the ocean, so probably doesn't happen in space, either. But death by decompression still would be a lousy way to die (like there are any good ones).

 

My two cents' is now in the ring.

 

Matt "Too-tired-to-be-witty-right-now" Frisbee

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Re: Is "Hollywood-style" decompression accurate?

 

Disclaimer: I'm not an expert on this subject' date=' so don't quote me.[/quote']

 

Too bad.

Nitrogen bubbles in the blood will cause debilitating pain (presuming the victim can get oxygen without a suit) long after the decompression (and will have other detrimental effects since most space environments don't have a decompression chamber, though a sophisticated airlock might do).

 

You wouldn't need a decompression chamber unless you intended on hanging out in zero atmosphere conditions. In which case you'd only have a few seconds of consciousness anyway.

 

Bringing someone back into normal Earth atmospheric pressure should take care of the bubbles fairly quickly.

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Re: Is "Hollywood-style" decompression accurate?

 

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

 

 

How long can a human live unprotected in space?

 

If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.

 

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after ten seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes, you're dying. The limits are not really known.

 

You do not explode and your blood does not boil because of the containing effect of your skin and circulatory system. You do not instantly freeze because, although the space environment is typically very cold, heat does not transfer away from a body quickly. Loss of consciousness occurs only after the body has depleted the supply of oxygen in the blood. If your skin is exposed to direct sunlight without any protection from its intense ultraviolet radiation, you can get a very bad sunburn.

 

At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil.

 

Aviation Week and Space Technology (02/13/95) printed a letter by Leonard Gordon which reported another vacuum-packed anecdote:

 

"The experiment of exposing an unpressurized hand to near vacuum for a significant time while the pilot went about his business occurred in real life on Aug. 16, 1960. Joe Kittinger, during his ascent to 102,800 ft (19.5 miles) in an open gondola, lost pressurization of his right hand. He decided to continue the mission, and the hand became painful and useless as you would expect. However, once back to lower altitudes following his record-breaking parachute jump, the hand returned to normal."

 

References:

 

Frequently Asked Questions on sci.space.*/sci.astro

 

The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov 1965).

 

Experimental Animal Decompression to a Near Vacuum Environment, R.W. Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of Aerospace Medicine, Brooks AFB, Texas.

 

Survival Under Near-Vacuum Conditions in the article "Barometric Pressure," by C.E. Billings, Chapter 1 of Bioastronautics Data Book, Second edition, NASA SP-3006, edited by James F. Parker Jr. and Vita R. West, 1973.

 

Personal communication, James Skipper, NASA/JSC Crew Systems Division, December 14, 1994.

 

 

 

--------------------------------------------------------------------------------

 

Henry Spencer wrote the following for the sci.space FAQ:

 

How Long Can a Human Live Unprotected in Space?

 

If you *don't* try to hold your breath, exposure to space for half a minute of so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.

 

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after 10 seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes you're dying. The limits are not really known.

 

References:

 

The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov. 1965)

 

Experimental Animal Decompression to a Near Vacuum Environment, R.W. Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of Aerospace Medicine, Brooks AFB, Texas.

 

 

 

--------------------------------------------------------------------------------

 

You would probably pass out in around 15 seconds because your lungs are now exchanging oxygen out of the blood. The reason that a human does not burst is that our skin has some strength. For instance compressed oxygen in a steel tank may be at several hundreds times the pressure of the air outside and the strength of the steel keeps the cylinder from breaking. Although our skin is not steel, it still is strong enough to keep our bodies from bursting in space.

 

Also, the vapor pressure of water at 37 C is 47 mm Hg. As long as you keep your blood-pressure above that (which you will unless you go deep into shock) your blood will not boil. My guess is that the body seems to regulate blood pressure as a gauge, rather than absolute pressure (e.g. your blood vessels don't collapse when you dive 10 feet into a pool).

 

The saliva on your tongue might boil, however.

 

For more information and references, see http://www.sff.net/people/geoffrey.landis/vacuum.html

 

Hope this helps!

The Ask an Astrophysicist Team

 

 

Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html for help on other astronomy Q&A services.

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Re: Is "Hollywood-style" decompression accurate?

 

So the the exposive decompression scene from 2001: A Space Odyssey is more accurate then from Aliens?

 

(IF you never saw the film Dave Bowman is forced to do a space walk with out a helment to get back into the main ship. He blows the hatch on his repair capsle and propells himself with explosive decopress into the Discovery's Airlock)

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Re: Is "Hollywood-style" decompression accurate?

 

So the the exposive decompression scene from 2001: A Space Odyssey is more accurate then from Aliens?

 

(IF you never saw the film Dave Bowman is forced to do a space walk with out a helment to get back into the main ship. He blows the hatch on his repair capsle and propells himself with explosive decopress into the Discovery's Airlock)

Yes, 2001 was pretty accurate in that regard (as it was with pretty much everything else regarding space travel).

 

Like Zeropoint said, unless it was sucking the atmosphere from the entire ship, or unless the Sulaco's life support systems were trying to pump air into the cargo bay as an emergency measure to give anyone in the cargo bay some extra breathing time (at the expense of rapidly depleting the ship's reserve air supply), yeah, the decompression in Aliens should not have taken so long.

 

And then, of course, there's the exploding bodies :eek: in the movie Outland... awesome movie, but COMPLETELY UNREALISTIC when it comes to decompression, as is now pretty clear from the above posts.

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Re: Is "Hollywood-style" decompression accurate?

 

I loved the 'Eyes balooning up to the size of grapefruit' bit in Total Recall myself. Followed by them shrinking back down to normal size with the return of pressure, and everyone being apparently perfectly OK then!

 

That, and the rapidity with which the air-generator gave mars a near-earth pressure atmosphere in 15 seconds, is what tipped be towards the 'Its all a computer game' side, rather than the 'its real' side. Of course, it could just be abysmal science on the part of the writers and it -was- supposed to be real.

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Re: Is "Hollywood-style" decompression accurate?

 

I don't think the alien device made the whole planet's atmosphere rise that fast, but it could have a big effect quickly in the local area right around the mountain which is what the movie showed.

 

As for the eyes popping out, well, that is hollywood for you. They have to make it dramatic and scary. Same with why cars in car crashes always seem to jump over what they are about to hit.

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Re: Is "Hollywood-style" decompression accurate?

 

I had assumed the whole planet's atmosphere rose that fast because otherwise there would be considerable movement in the air as it moved from the high pressure area around the device toward the much lower (near vacuum) pressure areas elsewhere.

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Re: Is "Hollywood-style" decompression accurate?

 

Ummm, don't think about Total Recall or you'll wind up with an aneurism. Remember that in just about any model of a stable atmosphere for Mars the top of Olympus Mons is still above it. That means that you just fired a bunch of atmosphere out the top of a volcano that would, by definition, have put that atmosphere at escape velocity... Oops.

 

They *did* have a bunch of high winds while the generator was working as I recall, but they died down fairly quickly which would imply they wanted to produce a complete planetary atmosphere in the few seconds that they showed... Although I have not done the math, that should result in some really nasty wind-speeds well above and beyond what they showed but then again maybe you just need a much longer scene (I forget off the top of my head gasses expansing into a vacuum).

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Re: Is "Hollywood-style" decompression accurate?

 

I guess the alien device also produced ozone to block UV rays and in sufficient quantities to provide immediate protection. Also, it produced a pressure wave of oxygen sufficient to displace or mix with the existing Martian atmosphere (and the Venusville habitat, where the oxygen levels were "bottoming out") without immediately setting anything flammable with an ignition source on fire -- a common condition when a blast/pressure wave passes through an enclosed space and breaks stuff and/or knocks it over.

 

Yeah, it was a fun movie in that Hollywood "whatever-makes-the-most-impressive-special-effect-and-to-hell-with-reality" sort of way.

 

Matt "Curmudgeon-with-a-tub-of-buttery-popcorn" Frisbee

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Re: Is "Hollywood-style" decompression accurate?

 

You wouldn't need a decompression chamber unless you intended on hanging out in zero atmosphere conditions. In which case you'd only have a few seconds of consciousness anyway. Bringing someone back into normal Earth atmospheric pressure should take care of the bubbles fairly quickly.

 

Yes, that's right -- thanks for pointing that out. Bully and a tiger for you! :)

 

Matt "I-stand-corrected" Frisbee

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Re: Is "Hollywood-style" decompression accurate?

 

I loved the 'Eyes balooning up to the size of grapefruit' bit in Total Recall myself. Followed by them shrinking back down to normal size with the return of pressure' date=' [i']and everyone being apparently perfectly OK then[/i]!

 

That, and the rapidity with which the air-generator gave mars a near-earth pressure atmosphere in 15 seconds, is what tipped be towards the 'Its all a computer game' side, rather than the 'its real' side. Of course, it could just be abysmal science on the part of the writers and it -was- supposed to be real.

 

I've always come down on the side that it was all just his awesome vacation memories. :thumbup:

 

When they are prepping Arnold for his "trip" in the Recall office the final woman displayed on the video monitor during his sexual preference quiz is the actress who plays the Mars prostitute/rebel.

 

And the young assistant even looks at some computer discs and mumbles to himself, "blue sky on Mars, hmm."

 

That added to all the scientific imposibilities has always made me think it was all just a wild memory implant.

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Re: Is "Hollywood-style" decompression accurate?

 

So is he a replicant or a replicant hunter?

 

Hollywood loves to ask questions like that and leave it open for the audience but in this case you have to have suspension of disbelief and accept the cartoon science for the question to hold.

 

The fact that they ask the question implies that they want to think that it is ambiguous and that means they were ignoring the right physics. At least that's my $0.02.

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Re: Is "Hollywood-style" decompression accurate?

 

Of course' date=' accurate tends to be cinematically boring.[/quote']

 

Won't argue with that!

 

And for the record Total Recall is awesome! Arnie at the top of his over the top game!

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Re: Is "Hollywood-style" decompression accurate?

 

Also, to save future time and effort, if anyone is thinking of asking "Is 'Hollywood-style' (fill in the blank) accurate?" here's the answer...

 

NO.

 

Agreed.

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Re: Is "Hollywood-style" decompression accurate?

 

Of course' date=' accurate tends to be cinematically boring.[/quote']

Well, truth is stranger than fiction... but not nearly as entertaining. ;)

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Re: Is "Hollywood-style" decompression accurate?

 

Of course' date=' accurate tends to be cinematically boring.[/quote']

Depends, of course. As noted, the 2001 scene, where Dave frantically works with controls while in vacuum, is riveting. The Aliens extended-decompression sequence, after a few seconds, passes my threshold of 'no, well, now everyone's dead' and ceases to be entertaining. Much better was the equivalent scene in the first film -- the entire cabin empties in under a second, leaving the alien still in the door, whereupon Ripley shoots it with a grappling hook and knocks it out into space (it must have only just been hanging on).

 

In Die Hard 4, one bad guy gets shot two or three times by McClane, but doesn't die (not from gunshots, anyway). Quite realistic. Dying immediately is also realistic, though every bad guy dropping dead after a single shot is not so realistic -- and films that have bad guys flop around wounded, or take a few hits before going down, tend to be a little more tense.

 

The same argument gets used for historical accuracy -- 'we can make it more exciting than real history! What's real history, anyway? It's all stories, so ours is just as valid!' (Paraphrase from the writer of Braveheart). Not only does real history give us some excellent stories, the idea that changing it makes things more exciting is... hubris. These stories were good enough to get the writers' attention in the first place, and in my opinion, the real history is usually better than what gets put on screen.

 

Ditto with science. Computers, rockets, decompression... they may not be as visually exciting as Hollywood's versions, but they certainly suit the more serious films... and the entry of Hollywood's versions into serious drama is guaranteed to throw me out. 'Zoom in and enhance' on a video does NOT fit in something like Prison Break. That particular scene was very off-putting to me in a way that it wouldn't be in cheeseball stuff.

 

But most writers aren't that skilled, so they mistake 'big' for 'good' and 'like it's usually done' for 'how it should be done' (or 'like modern stories' for 'interesting' in the case of historicals).

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Re: Is "Hollywood-style" decompression accurate?

 

Well' date=' truth is stranger than fiction... but not nearly as entertaining. ;)[/quote']

As I said, it really depends on the film and how skilled the director is. 'Big explosion' isn't necessarily the mark of a bad director... but it's the first fallback of the lame one.

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Re: Is "Hollywood-style" decompression accurate?

 

Also, to save future time and effort, if anyone is thinking of asking "Is 'Hollywood-style' (fill in the blank) accurate?" here's the answer...

 

NO.

 

Hey, even a stopped clock is right... blah, blah, blah...

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