Re: Breaking News: US Air Marshalls

MM wrote:
On Fri, 11 Aug 2006 15:38:56 +0100, Alex Heney <me8@xxxxxxxxxxx>
wrote:


On Fri, 11 Aug 2006 14:57:09 +0100, Scott <blackhole@xxxxxxxxxxx>
wrote:


Alex Heney wrote:

On Fri, 11 Aug 2006 13:06:32 +0100, Scott <blackhole@xxxxxxxxxxx>
wrote:



Alex Heney wrote:


On Fri, 11 Aug 2006 09:12:16 +0100, "M.I.5¾"
<no.one@xxxxxxxxxxxxxxxxxxxxxx> wrote:




"Ian Stirling" <root@xxxxxxxxxxxxxxxxx> wrote in message news:44db697d$0$18079$ed2619ec@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx



"M.I.5?" <no.one@xxxxxxxxxxxxxxxxxxxxxx> wrote:
<snip>

An excellent move, though unadviseable in a pressurised aeroplane.

Now work out the airflow out of a 9mm hole.
2/3 bugger all.
There is a big 4" or so valve, that's mostly open in flight, to regulate
air pressure on the plane, as the air conditioning pumps it in.
Hitting something vital is a slightly bigger concern.

The pressure differential at 35,000 feet is such that anyone sitting near that 9mm hole will fit through it without any trouble at all. But as someone noted, the pressure differential; is such that it won't stay a 9mm hole for very long, especially once a couple of passengers (complete with seats) have passed through it.



Even allowing for the suction effects caused by airflow over the hole,
the pressure differential is unlikely to be more than 1 bar (there
will be *some* air pressure outside, so the "static" differential will
be less than that). (I'm not even sure it is *possible* for it to be
more than that)

A circle 9mm in diameter is approximately ½ sq inch in area. So that
means there is a *maximum* pressure outwards of approximately 7½ lbs
(1 bar is about 15psi).

You can hold a weight of 7½ lbs with one finger, and most newborn
babies weigh around that much, so it seems rather unlikely that
anybody (even a small baby) could be sucked out through the hole.

On the other hand, if a door blew off, for instance, lets say 6' by
2', that would give an area of 1728 sq inches - which would equate to
a total outward pressure of almost 26,000 lbs (assuming 1 bar pressure
differential) - which would obviously suck out anybody close by. That
is over 10 *tons* of total pressure.

Rubbish, pressure is not measured in lbs but (if you have to use imperial units) lbs/sq inch. The pressure is exactly the same. The whole notion of being sucked out of an aircraft through a bullet hole is an urban myth. It started as a result of a James Bond novel and has been propagated by films ever since.


Try reading what I wrote before calling it rubbish and then proceeding
to say the same.

OK, So I should have said the total *force* applied, rather than total
pressure, but I am sure most people knew what was meant.

And it was absolutely obvious to anybody reading it that I knew
perfectly well that it is psi that matters, and that there is no
chance pf being sucked out like that.

There no such thing as 10 tons of total pressure, an error you repeated twice (and I see you have acknowledged). You also say 'which would obviously suck out anybody close by' you are trying to equate the total maximum force over a large hole with the force which any passenger would experience. It is nonsense, as a moments consideration will show; the air pressure will equalize in a fraction of a second meaning a force experienced amounts to no more than a momentary impulse, easily resisted if it's even noticed.

Yes, it will equalize quickly.

But anybody close to the hole *may* experience sufficient suction to
pull them out of the hole, if it is the right (or wrong!) size.

As happened to the one person who died when that airliner lost its
roof.

If they happen to be smaller than or the same size as the hole, and
standing right next to it, then they will experience the full force of
the air trying to equalize that pressure differential. Which could be
15psi on every sq inch of the side of their body away from the hole.

But the further away they are, the less that effect will be, to the
extent that 2-3 feet away will be sufficient in most cases, and being
in a seat will also significantly reduce the overall force acting on
them.


Even if they didn't get sucked out in entirety, could any exposed body
parts have been sucked off, so to speak? I mean, supposing one's nose
was close to the hole (one is asleep and lying in that direction),
could you lose the tip?

MM

Only in Hollywood movies. Even extreme vacuum has been survivable:

"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 concious 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 conciousness 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."

http://www.sff.net/people/Geoffrey.Landis/vacuum_jsc.html

"In 1960, during a high-altitude balloon parachute-jump, a partial-body vacuum exposure incident occurred when Joe Kittinger, Jr. lost pressurization in his right glove during an ascent to 103,000 ft (19.5 miles) in an unpressurized balloon gondola, Despite the depressurization, he continued the mission, and although the hand became painful and useless, after he returned to the ground, his hand returned to normal. Kittinger wrote in National Geographic (November 1960):

"At 43,000 feet I find out [what can go wrong]. My right hand does not feel normal. I examine the pressure glove; its air bladder is not inflating. The prospect of exposing the hand to the near-vacuum of peak altitude causes me some concern. From my previous experiences, I know that the hand will swell, lose most of its circulation, and cause extreme pain.... I decide to continue the ascent, without notifying ground control of my difficulty."
at 103,000 feet, he writes:
"Circulation has almost stopped in my unpressurized right hand, which feels stiff and painful."
But at the landing:
"Dick looks at the swollen hand with concern. Three hours later the swelling will have disappeared with no ill effect."

Also:

"A suit puncture has occurred on a Shuttle flight. On STS-37, during flight experiments, the palm restraint in one of the astronaut's gloves came loose and migrated until it punched a hole in the pressure bladder between his thumb and forefinger. It was not explosive decompression, just a little 1/8 inch hole, but it was exciting down here in the swamp because it was the first injury we've ever head from a suit incident. Amazingly, the astronaut in question didn't even know the puncture had occured; he was so hopped on adrenalin it wasn't until after he got back in that he even noticed there was a painful red mark on his hand. He figured his glove was chafing and didn't worry about it.... What happened: when the metal bar punctured the glove, the skin of the astronaut's hand partially sealed the opening. He bled into space, and at the same time his coagulating blood sealed the opening enough that the bar was retained inside the hole."
.

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