Date:         Tue, 1 Nov 1994 14:39:09 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         shibumi@cisco.com (Kenton A. Hoover)
Subject:      Re: for campers: Propane Safety

At 13:46 1/11/94, J. Walker wrote:
>1) a house trailer near here, and an area about 50 yards in radius, was
>   destroyed by a propane cylinder explosion. at least that's what the fire
>   department finally decided. they never did figure out what set it off.
>   but it completed obliterated the trailer and everything within that 50
>   yard circle ... the only thing left of the trailer was the frame ... and
>   it was pretty mangled.

A known mode of sailboat death is a propane cylinder left open when the
owner docks the boat for a few weeks.  The propane fills the bilges of the
boat (being heavier than air, it sinks to the bottom), and at some point
enough water leaks in via thru-hulls to trip the electric bilge pump.  This
provides an ignition source for the propane, which converts the sailboat to
a sailboat hull and scrap wood.

Its an impressive effect.

>2) the u.s. air force had a propane (or was it butane?) bomb that worked with
>   rather terrible efficiency. rather like napalm, but without the flames and
>   the lingering fires. one detonator ruptured the propane tank, which caused
>   the gas to disperse over the target area ... then a delayed 2nd detonator
>   ignited the mess. really bad shock waves, doing serious damage.
>
>    but i think they gave up on it because it was a bit unpredictable ...
>    rather dependent on the weather conditions at the target.

BLU-82, a 12,000lb bomb that works roughly along the lines you sketch out.
However, the burster charge pushes the gas out at high speeds, so its not
that vulnerable to weather effects.  The detonator doesn't ignite the gas,
it creates a pressure wave which both compresses and explodes the gas,
causing a shockwave that actually accellerates as it progresses thru the
gas cloud.  There is a fascinating paper on the principles behind this
device in one of the AIAA compendiums on ordinance technology (you need to
read between the lines a bit in the paper).

The reason that they don't use it very often is that you can't put this
thing in the bomb bay or on the wing pylon of any bomber we've got.
Rather, you load it into the cargo bay of a C-130, and push it off the
loading ramp over the target.  In Vietnam, it was used to instantly turn
forests into helecopter landing fields covered with toothpicks and to
convert live people into seemingly physically intact dead people.  There
were two smaller devices based on the same principle that were designed to
be delivered by smaller aircraft, but it turns out that the mechanics of
the explosion work well only on a very large scale (thus a 500lb device
would not be just 1/24 the effect of the large device, unlike conventional
explosives).


| Kenton A. Hoover                                     |  shibumi@cisco.com |
| Engineering Computer Services                        |                    |
| Cisco Systems, Inc.                                  |    +1 415 324 5249 |
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