Mythbusters Explosive Decompression Experiment

"C J Campbell" wrote in message
...
I think the people who worry about getting sucked out of an airplane by
decompression are the same sort of people who had childhood fears about
being sucked down by the bathtub drain or getting sucked up by the vacuum
cleaner. Such fears are irrational, Hollywood plays up to them, but they
are
there nonetheless.

Hey, not so fast!

MB only proved that a bullet through an aircraft fuselage, aircraft window,
or even losing an entire window wouldn't cause explosive decompression. They
didn't cover getting sucked down a bathtub drain or sucked up by a vacuum
cleaner yet. Maybe next episode =D

Eric

On Mon, 12 Jan 2004 23:37:03 -0800 "C J Campbell" wrote:


"R.Hubbell" wrote in message
...
| On Sun, 11 Jan 2004 21:13:28 -0800 "C J Campbell"
wrote:
|
| Now, that was cool!
|
| Mythbusters pressurized an old DC-9 and fired a bullet through the wall
to
| see if it would cause an explosive decompression. It didn't. Then they
fired
| a bullet through the window to see if the window would shatter and cause
an
| explosive decompression. The bullet only made a small hole in the window
| because the windows are made of shatter-proof plastic. No explosive
| decompression.
|
| I don't watch much TV but I admit I would have liked to have seen this.
|
| Can you provide more detail on how they setup the test?

They took a derelict DC-9 at an aircraft graveyard and plugged up the holes.
They had real trouble with the cockpit because the windows had been removed.
They tried to replace the windows with plywood cemented in with foam, but
the plywood proved to not be strong enough to allow pressurization of the
aircraft. It kept blowing out, sometimes spectacularly.

The pistol was mounted on a stand in the cabin and fired by remote control
using a servor cannibalized from a vending machine, of all things. The
handgun was a 9 mm automatic; it looked like a Glock.

The aircraft was pressurized using one of those giant ground starter units
designed for 747s, a huffer. They dumped huge sacks full of packing peanuts,
scattering them around the cabin to so that the airflow inside the cabin
would be visible. The bullet holes disturbed the airflow so little that even
the packing peanuts stayed where they were.

|
| What was the cabin pressure? What was the pressure external to the
| DC-9? Did they have a huge pressure chamber?

They calculated the pressure differential at 35,000 feet to be 8 lbs psi, so
they pressurized the interior to 8 lbs psi. As mentioned, they had trouble
doing this. The plywood in the cockpit could only stand about 6 lbs psi. At
one point the plywood blew out and ejected a cushion from the pilot seat
more than 125 yards. They finally ended up reinforcing it enough to
withstand the 8 lbs psi differential. I guess the lesson there is that if
you ever lose a cockpit window you can forget about restoring cabin pressure
by plugging it up with plywood.

|
| What about the temperature differentials? There's also a pressure
| differential from the flow of air over the fuselage. Correct?
| How did they simulate that?

The 8 lbs psi differential comes pretty close to the pressure differential
for an aircraft pressurized to 6,500 feet flying at 35,000 feet. After all,
the total weight of the entire atmosphere is only 15 lbs psi. If anything,
they erred on the side of increased pressure differential. A pound of air
psi is a pound of air psi, no matter what the source.

One thing I found interesting which they did not talk about was watching the
skin of the airplane inflate and become taught as the airplane was
pressurized.



That brings up another question (don't have to answer, just food for thought)
How many pressurization cycles did the DC-9 experience over its lifespan?




Once they managed to induce an explosive decompression using the shaped
charge, the damage was incredible. The whole top of the fuselage was ripped
off and big chunks of the wall where the explosion was were missing. It
looked like those photos of the Hawaiian Airlines incident, only much worse.
I think it might have been possible to continue to fly the aircraft, but it
would have been very difficult, depending on how much damage the debris did
to wings, tail, engines and control surfaces.

Of course, to do that kind of damage a terrorist would have to somehow get a
shaped charge the size of a basketball onto the airplane, place it properly
up against the wall of the fuselage, and detonate it, all without being
noticed. In any event, a bullet will not do that kind of damage, unless the
bullet is some kind of anti-tank artillery round. It was obvious that any
handgun bullet is too small by several orders of magnitude to do any
significant damage. You could have pressurized that plane for space flight
and the result would have been the same. Well, no it wouldn't. That much
pressure would have started popping windows or something long before they
would have had a chance to fire their gun or set off their explosives. But a
bullet hole would not have made a measurable difference even then.




They did a reasonable job of recreating the environment but we all know
how hostile things are at 35,000 and 600 mph and -35 degrees, where air is
less dense.


So the question is would any of us be willing to head up to 35,000, crank her
up to mach .76 and get out the Glock and let loose a few rounds??

Also suppose the bullet hits some wiring or hydraulics or fuel line, etc.


Not me.


R. Hubbell

"R.Hubbell" writes:

So the question is would any of us be willing to head up to 35,000, crank her
up to mach .76 and get out the Glock and let loose a few rounds??

Also suppose the bullet hits some wiring or hydraulics or fuel line, etc.


Not me.

I woudln't do it in a *car* either, though. It comes under the
heading of "negligible risk, *zero* gain" -- so why risk it?

Shooting through the wall between windows pretty much guarantees I
won't hit hydraulics, fuel line, etc.
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
RKBA: http://noguns-nomoney.com http://www.dd-b.net/carry/
Photos: dd-b.lighthunters.net Snapshots: www.dd-b.net/dd-b/SnapshotAlbum/
Dragaera/Steven Brust: http://dragaera.info/

"Bill Denton" writes:

A couple of notes/questions...

Given that it is fairly rare for someone to only fire a single shot under
these circumstances, shouldn't the effect of the typical three shots have
been considered? While a single shot to the window only created a single
hole, would it not be possible for three shots into that same window to
compromise the window structure resulting in the entire window failing and
coming out of the aircraft?

Could well be an issue of their mechanism holding the pistol too
firmly -- so further shots would have hit the same place. And they
didn't want to go to the next level of complexity. I do agree that
multiple shots to the same window is a case worth investigating.
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
RKBA: http://noguns-nomoney.com http://www.dd-b.net/carry/
Photos: dd-b.lighthunters.net Snapshots: www.dd-b.net/dd-b/SnapshotAlbum/
Dragaera/Steven Brust: http://dragaera.info/

"Ben Jackson" wrote

Are you sure the instruments aren't just calibrated for the error?


--
Ben Jackson

Ahhh, yea!?!!!!!

Haven't been around much, have you?
--
Jim in NC

"Bill Denton" wrote

.. Try this experiment: Drive down the road in
your car at highway speed, with all of the windows closed except the
driver's. Then take an ordinary tissue and release it about a foot away
from
the window. Voila, it will be "sucked" out of the window.


Different than an airliner fuselage. There is slightly higher pressure in
font of the windshield, and low pressure slightly behind the windshield,
where the window is. A cylindrical fuselage has few changes such as that,
has few pressure changes along its length.
--
Jim in NC

"R.Hubbell" wrote in message |
|
| They did a reasonable job of recreating the environment but we all know
| how hostile things are at 35,000 and 600 mph and -35 degrees, where air is
| less dense.
|
|
| So the question is would any of us be willing to head up to 35,000, crank
her
| up to mach .76 and get out the Glock and let loose a few rounds??
|
| Also suppose the bullet hits some wiring or hydraulics or fuel line, etc.

The air pressure in an airliner is less than one atmosphere, no matter what.
At 35,000 feet you are talking half an atmosphere. Compare that to the tires
in your car. The airliner produces all of 8 lbs psi, less than a third of
the inflation of an automobile tire. All of this other stuff, 600 mph or
slight variations of air pressure along the fuselage, etc., is minuscule.

Mythbusters gave the hyperventilating pants wetters a bit of a reality
check -- and all they can talk about are minor factors that will not change
the results in any significant way. I don't care if you empty the entire
magazine into a window, you are not going to suck people out of the
airplane, the airplane is not going to go into some kind of dive, people are
not going to fly all over the interior of the airplane, the seats are not
going to be ripped from the floor, or any other Hollywood bull**** like
that.

I used the automobile as a simple example; you would also observe the same
phenomena at the middle or rear of a school bus. And most of us have heard
of situations where a sectional was "sucked" out the window of a J3 Cub or
similar aircraft with larger, operable windows.

Again, I am not an engineer and I don't know the correct terms for all of
this.

Obviously you will see position-dependent variances, but if you take a large
aircraft, remove one of the windows, and fly the aircraft unpressurized, the
movement of air along the fuselage will "draw" air from inside the cabin out
through the window opening.

And until a PE tells me otherwise, that's my story and I'm sticking to it!
GBG


"Morgans" wrote in message
...

"Bill Denton" wrote

. Try this experiment: Drive down the road in
your car at highway speed, with all of the windows closed except the
driver's. Then take an ordinary tissue and release it about a foot away
from
the window. Voila, it will be "sucked" out of the window.


Different than an airliner fuselage. There is slightly higher pressure in
font of the windshield, and low pressure slightly behind the windshield,
where the window is. A cylindrical fuselage has few changes such as that,
has few pressure changes along its length.
--
Jim in NC

"C J Campbell" wrote in message
...

"R.Hubbell" wrote in message |
|
| They did a reasonable job of recreating the environment but we all know
| how hostile things are at 35,000 and 600 mph and -35 degrees, where air
is
| less dense.
|
|
| So the question is would any of us be willing to head up to 35,000,
crank
her
| up to mach .76 and get out the Glock and let loose a few rounds??
|
| Also suppose the bullet hits some wiring or hydraulics or fuel line,
etc.

The air pressure in an airliner is less than one atmosphere, no matter
what.
At 35,000 feet you are talking half an atmosphere. Compare that to the
tires
in your car. The airliner produces all of 8 lbs psi, less than a third of
the inflation of an automobile tire. All of this other stuff, 600 mph or
slight variations of air pressure along the fuselage, etc., is minuscule.

Mythbusters gave the hyperventilating pants wetters a bit of a reality
check -- and all they can talk about are minor factors that will not
change
the results in any significant way. I don't care if you empty the entire
magazine into a window, you are not going to suck people out of the
airplane, the airplane is not going to go into some kind of dive, people
are
not going to fly all over the interior of the airplane, the seats are not
going to be ripped from the floor, or any other Hollywood bull**** like
that.

Yes, but evidently Hubbel is stuck on his Hollyweird delusions.

"C J Campbell" wrote in message
...

"R.Hubbell" wrote in message |
|
| They did a reasonable job of recreating the environment but we all know
| how hostile things are at 35,000 and 600 mph and -35 degrees, where air
is
| less dense.
|
|
| So the question is would any of us be willing to head up to 35,000,
crank
her
| up to mach .76 and get out the Glock and let loose a few rounds??
|
| Also suppose the bullet hits some wiring or hydraulics or fuel line,
etc.

The air pressure in an airliner is less than one atmosphere, no matter
what.
At 35,000 feet you are talking half an atmosphere. Compare that to the
tires
in your car. The airliner produces all of 8 lbs psi, less than a third of
the inflation of an automobile tire. All of this other stuff, 600 mph or
slight variations of air pressure along the fuselage, etc., is minuscule.

Mythbusters gave the hyperventilating pants wetters a bit of a reality
check -- and all they can talk about are minor factors that will not
change
the results in any significant way. I don't care if you empty the entire
magazine into a window, you are not going to suck people out of the
airplane, the airplane is not going to go into some kind of dive, people
are
not going to fly all over the interior of the airplane, the seats are not
going to be ripped from the floor, or any other Hollywood bull**** like
that.

How much more clearly can things be explained...to a troll?