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From: nraoaoc@nmt.edu (Daniel Briggs)
Newsgroups: rec.skydiving
Subject: Re: High altitude landings
Message-ID: <1991May28.201057.12714@nmt.edu>
Date: 28 May 91 20:10:57 GMT
References: <6138@ptsfa.PacBell.COM> <1991May24.195359.8410@cc.curtin.edu.au> <918@lhdsy1.chevron.com>
Reply-To: dbriggs@nrao.edu (Daniel Briggs)
Organization: National Radio Astronomy Observatory, Socorro NM
Lines: 27

In article <918@lhdsy1.chevron.com> yzarn@lhdsy1.chevron.com (Philip Yzarn de Louraille) writes:
>Yes, the calculations shown by the MIT guy seemed correct but an
>increase of only 25% in landing speed at 9000' is wrong. It is not
>enough and plenty of people have experienced it. Maybe the velocity
>square law does not apply and the velocity law in a linear fashion
>applies, in this case, the predicted landing speed is about 50-60%
>faster (at 9000') than at sea level. This seems more like it.

Geez, this seems to be getting into the realm where some real data
would help.  You know, we all go through a good ten grand altitude
differential or more, nearly every time we jump.  Why doesn't someone
borrow a couple of hang glider instruments and take along a recording
walkman.  Hop and pop at ten grand, and read off the altitude, sink
rate, and temperature all the way down.  Thermals and wind will be a
problem, I grant you, but maybe on a calm day at a flat drop zone we
can tell the difference between 25% and 50% increase in sink rates.
Anyone got any good ideas on how best to minimize the contaminants?
Carry a wind speed sensor, and only compare comparable points?  Ignore
it, and model fit to the whole data set?  Whatever, I think something
useful might come out of it.

Just a thought,

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