From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Explosionless violent reactions...
Date: 15 Nov 1995 09:17:01 GMT
Organization: Consulting Chemist
Lines: 61

In article <48aaib$q3j@unix1.cc.ysu.edu>, jekuhns@unix1.cc.ysu.edu (John
Kuhns) says:

>I tried for five minutes to come up with a title that made sense.
>What I need is a chemical reaction that is violent and produces a
>huge volume increase, without fire or a violent shock wave. I have
>asked into car airbags, and found that they use sodium azide and
>gold-plated surfaces, but the rest of the story is either a trade
>secret or not-known by the person I asked.
>
>What I need is a quick reaction that uses relatively safe reagents
>and produces relatively safe by-products. Any help would be greatly
>appreciated.

You've got a big problem. If you want a lot of gas instantly
you must either use compressed gas or a hot explosive reaction.

You wouldn't want a "cold" explosive reaction, because if the
propagation does not require heat then the activation energy 
must be low and the consequence of low activation energy is
extreme sensitivity.

What you may be able to settle for is a compound gas generator,
not of the explosive kind, which is required for auto air-bags,
which can't wait, but of the controlled rate type such as are
used in the Boeing 707 slide inflator.  

If you can produce a rapid stream of gas by say a whistle mix 
or from a binary hypergollic reaction or from a catalytic 
decomposition, you can use the hot gases to suck a larger 
volume of air into a venturi system and inject the mixed
gas where it is needed.  I report this information
second hand, having never actually worked with such a
system.  When I was with EXCOA, the parent company,
Rocket Research corporation, made such devices.

An example of a catalytic system is that used by Rocket
Research to make attitude control rockets. They merely
metered hydrazine over a catalyst which caused it to 
decompose into its elements and ammonia gas. I was told
that they used the same type of technology to build the
Boeing slide inflator system, except that they added a
venturi device to multiply the gas output and cool it.

Hmmm. I never thought about it before, but I wonder how they
handled the potential hydrogen explosion problem.  Maybe
they let the air react at the venturi and used the steam 
to suck even more air??

Anyway, perhaps one of your deflagrating pyrotechnic mixes
could be harnessed as a super high speed pump.  If a venturi
really can suck multiplied volumes of air, it will not matter
that some of the reaction products condense after doing their
job.

If there are any experienced engineers in this area, I'd 
surely like to hear about the mathematics of venturis.


Jerry 

If you don't like this idea, just wait for a better one
from AOL.