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RE: Parachute Deployment Load Rates...

To: "'Bryan Savage'" <basavage@earthlink.net>
Subject: RE: Parachute Deployment Load Rates...
From: "Albaugh, Neil" <albaugh_neil@ti.com>
Date: Mon, 28 Oct 2002 10:28:03 -0600
Bryan;

Thanks for that interesting Russian parachute link. I wish they had included
timing markers on the canopy inflation photos so that the opening "snap" of
those different designs (balloon, ring, cross, etc) could be compared.

FYI, the last climbing rope I owned was rated at 5400lbs breaking (tensile)
strength at 50% elongation. That's beaucoup stretch!

Regards, Neil     Tucson, AZ


-----Original Message-----
From: Bryan Savage [mailto:basavage@earthlink.net]
Sent: Sunday, October 27, 2002 11:13 AM
To: Albaugh, Neil
Cc: 'DrMayf'; land-speed@autox.team.net
Subject: Re: Parachute Deployment Load Rates...



Neil,

I have discovered an amazing  amount of  military parachute R & D going 
on today.
One project is even trying to  integrate CFD and FEA systems with the goal
of  reducing testing expense. The impression that I get is that every 
initial deployment of
any new parachute is part R & D.
They even analyze the effect of the wrinkles caused by packing!

One way to deal with the chute opening shock load is to slow the chute 
opening.
A bag is the most accepted method to start out with. There a method 
called "reefing"
 that can cause the chute to open in stages, drastically slowing the 
opening time.

Your statement:

Parachute tether line seems to have similar requirements to climbing rope--
it needs to stretch and absorb energy.

is absolutely correct. The material selection is critical. Two identical 
appearing pieces of
nylon tow line can have much different mechanical characteristics. Under 
the same load one
may stretch 5% and the other 20%..
If you don't mind getting buried in data, you can check this out:
http://www.mtu-net.ru/mosseev/pl/paralab.htm 

Finally, your reference to accident information is valid. One thing I 
know for sure,
ignorance kills.

Bryan

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