[RocketsNW] Parachute protection options

[Paul Bogdanich]

Finally something I have some experience with.  Having burned in a 
distressingly high proportion of my initial attempts I have learned a few 
things about pistons as that was the cause of one of the failures.  The 
fist thing I learned is watch out for temperature changes across dissimilar 
materials.  Phenolic pistons in quantum tube for example are a 
challenge.  Either too hot or too cold and you are not safe.  Aluminum in 
quantum seems to work without difficulty at all relevant temperatures as 
long as you have .0075 <= X <= .01 clearance a side.  Aluminum in phenolic 
needs to have a longish skirt (>= .75 ID) that is slightly tapered with the 
leading edge relived or chamfered so it doesn't hang on the grooves.  As 
for me I have tired of the whole piston thing and have taken to making 
parachutes directly from 1.9 oz per yard Kevlar.  Just tape the ejection 
charge to the bottom of the parachute (not literally folks) and 
fire.