Re: Breaking News: US Air Marshalls

Alex Heney 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.

They were 'swept' out according to the accident report rather than sucked out. No passenger was sucked out even those not wearing a seat belt, nor was any other crew member.



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.


Nothing like that. The pressure difference is 8 psi at normal flying altitude. However you will not experience the 8psi difference unless you are actually blocking the hole. What gets blown out are maps, charts, flight logs, and magazines, but if I open a window during a hurricane things do indeed get blown around.

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.

Small holes of 1 sq cm are not significant. Even 10 M^3 space craft with such a hole would take about 6 minutes to drop from 1 atmosphere to 0.5 atmospheres. [*]

[*] Demetriades, S.T., "On the Decompression of a Punctured Pressurized Cabin in Vacuum Flight," Jet Propulsion, January-February, 1954, pp. 35-36.

There are several cases of humans surviving exposure to vacuum.
http://www.sff.net/people/Geoffrey.Landis/vacuum.html
.

Relevant Pages

  • Re: RCR rims, NASACAR SAYS IT DIDNT HAPPEN
    ... The fact that your theory about a small hole just bleeding off air ... sort in place to stop the bleeding once the pressure got to where the CC ... are a different breed of tire from the basic ...
    (rec.autos.sport.nascar)
  • Re: Leak in piping - Boyles law
    ... | small hole. ... | to outside air of 1000mbar pressure ... leave the pipe at double that higher rate. ...
    (sci.physics)
  • Re: Roll your own air compressor?
    ... In the side of the compressor head are two threaded holes. ... I have a plug in the small hole and the outlet tee in the larger one. ... One leg of the tee has a water heater pressure relief, ... have the air valve. ...
    (rec.crafts.metalworking)
  • Re: Breaking News: US Air Marshalls
    ... air pressure on the plane, as the air conditioning pumps it in. ... 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 have passed through it. ... I examine the pressure glove; its air bladder is not inflating. ...
    (uk.legal)
  • Re: How to Lower U.S. Firearm Murder and Suicide Rates
    ... If a bullet were to penetrate a pressurized airplane, ... it is a big hole. ... hole on cabin pressure is not enough to be measurable. ... It's a myth, OK? ...
    (alt.guitar.amps)