[PSAS] Deployment charge at altitude

rq17zt rq17zt at q7.com
Thu Nov 3 00:48:24 PST 2005

jay at BeckFamily.com wrote:

 > Most people use black powder to deploy their parachutes . but when you are going for
 > 30,000 ft or more, there is not enough oxygen up there and you just get a  'pop', so we
 > are using a CO2 system to push out the parachute.

We've thought about this some. The lack of oxygen can not be the
technically correct (i.e. correct) explanation. All fast-burning
materials including black powder are self-oxidizing. (Consider the
rate of O2 diffusion required to maintain combustion under what are
basically explosive conditions.)

Since altitude has often been reported to effect the combustion of
black powder, we think the explanation may be in the transfer of heat
between the powder grains. Particularly if the powder charge becomes
dispersed, the conduction of heat may be strongly effected by the
atmospheric density.

Previously Brian was interested in a cold-gas separation system for
high-altitude deployment. I personally would prefer to avoid the
complexity of a cold gas system. Clearly further use of any system at
high altitudes requires some testing. To this end we have started to
think about a vacuum test chamber.

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