Text 34106, 94 rader
Skriven 2009-07-02 14:01:23 av Roy Witt (1:397/22)
  Kommentar till text 34068 av Ward Dossche (2:292/854)
Ärende: Explosive Decompression Myth        Was: Guns and Banks
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02 Jul 09 15:58, Ward Dossche wrote to Robert Bashe:

 RB>> RW> The boarding of sky marshalls isn't unsafe.
 RB>> The experts seem to disagree. They think a shootout inside a
 RB>> pressurized aircraft at 30,000 feet is rather dangerous.

 WD> As you know as a scientist explosive decompression would occur if a
 WD> bullit pierces the hull. Because of the tiny hole and high pressure
 WD> inside, chances are real the airframe would collapse.

LOL! That whacko wives tale theory has been debunked by engineers who've
actually done their homework.

The Truth About Explosive Decompression

Is it true that if you shoot a bullet through the skin of an airliner in
flight, everyone would get sucked out the little hole? If not, Hollywood
(and Ward Dossche) has a lot of explaining to do.

Adam and Jamie from Mythbusters on the Discovery Channel set out the other
night to find out if this was true. The myth is based on the fact that an
airliner at 35,000 feet is like a ballon flying through the air - the air
pressure on the inside (pushing out against the inside of the plane) is
much higher than the ambient air pressue at that altitude.

When you pierce the skin of a ballon with a pin, the whole thing pops. The
pressurized air inside the ballon rushes out with such force that it
"grabs" the edges of the hole as it leaves and tears the ballon apart in
an instant. The same should be true for an airliner, right? And everything
in the plane should go rushing out the hole, right?

No. Mythbusters proved this wasn't the case, thus proving wrong several
dozen action movies (Ward Dossche and any others who support him) and at
least one James Bond film. And, true to Mythbuster's style, they proved
this point with a veritable tidal wave of geekiness.

They went to an airline graveyard in the Mohave Desert and found an old
Hawaiian Airlines 737. They sealed it up, then brought in a massive air
compressor and pumped the plane full of air until the difference between
the interior of the plane and the air at sea level was the same as it
would be if the plane was flying at 35,000 feet.

Now the cool part - inside the plane, they had parked their crash-test
dummy, Buster, in a window seat. In the aisle, they rigged up a Glock 9mm
to a firing mechanism and pointed it at the hull of the plane. Then, with
the plane fully pressurized, they fired the gun remotely.

What happened? Nothing. Sure, the air rushed out, but even styrofoam
peanuts they had placed in the aisle didn't move, much less Buster. They
did the test a second time, this time firing through the window right next
to Buster. Same result - nothing.

Not satisfied (I love it when they're not satisfied.), they rigged
explosive cord around the window to simulate the window blowing out due to
structural failure. They pressurized the plane again and blew the window.

The results were much more satisying - Buster got his arm yanked out the
window. Crash test dummies aren't designed to come apart, but if he were a
human, I think he would have lost his arm. However, the rest of his body
just wasn't going through the window, no matter what the myth said.

Still not satisifed, Adam and Jamie put a "shaped charge" (whatever that
is) against the hull next to Buster's knee. Plane pressurized once again,
they blew the charge.

Now, I don't know how much damage was from the charge and how much was
from the air rushing out, but the entire roof came off the plane. Buster,
believe it or not, was still belted in his chair, but there was a 20-foot
section of the roof missing. That plane was toast, and it looked eerily
similar to Aloha Airlines flight 243 that lost its roof in mid-flight back
in 1988.

So, myth busted. However, they didn't address one thing: the drop in air
pressure caused by the velocity of the air outside the plane. You see, the
entire concept of flight is based on the fact that air pressure goes down
as the speed of the air goes up.

So when a hole gets blown in the side of the plane, even after all the air
rushes out and the pressue of the plane is equal to the ambient air
pressure at that altitude, you now have 600 m.p.h. air rushing past the
hole, which would have a much lower air pressure than the stationary air
inside the plane. Does this make sense to anyone else?

That question aside, this segment proved, once and for all, that
Mythbusters ranks right up there with Extreme Engineering and Modern
Marvels as God's gift to geeks.

                R\%/itt

Joy lives in the fight, in the attempt, in the suffering involved, not in
the victory itself.

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