01 Jul 2004 john robinson, Subject: chute loads v/s time
(snip..)regardless of speed, and the loads seen are mitigated by the
stretchyness of the nylon system, now we were gathering data at 40 bits a
second/channel and we had enough memory to grab 4 channels for just over 3
minutes, so we could see the entire jump.
I am assuming "40 bits a second" means 40Hz (25 milli seconds) and not 40
bits of resolution (about 1 trillionth of a second). The old 8080 or Z80
just couldn't log data that fast. If John could capture only a 25 milli
second slice of data, and the Yank force was a 15 to 35 milli second event,
it is most likely they never recorder that data.
A few years ago I was involved with a high altitude, high speed, experiment.
At first glance you would assume there would be little force on the chute
since the air was so thin (very few molecules up there). However, that is
not the problem. Even though there are few molecules, the few that are
there, are traveling at a very high rate of speed. The true-air-speed is
what influences the chute opening speed. The RATE of opening is what is
destructive and not the total force after it is fully open.
I agree stretch will attenuate some of the "shock" force of a fully open
chute. However, is those last few milli seconds to full deployment that the
RATE-OF-OPENING is so high that is destructive. The system can't stretch
fast enough. -Elon
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