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From: tneale@aeras.UUCP (Tom Neale)
Newsgroups: sci.space,sci.space.shuttle
Subject: Re: space news from May 1 AW&ST
Message-ID: <332@aeras.UUCP>
Date: 7 Jun 89 01:37:13 GMT
References: <1989May29.032320.2277@utzoo.uucp> <486@cybaswan.UUCP> <1989Jun4.055452.12921@utzoo.uucp>
Reply-To: tneale@aeras.UUCP (Tom Neale)
Organization: Arix Corporation  San Jose, CA.
Lines: 34

In article <1989Jun4.055452.12921@utzoo.uucp> henry@utzoo.uucp
 (Henry Spencer) writes (and correctly I might add):

>If I haven't got the terms mixed up, no, they are not the same thing.
>Rogallo's concept was a flexible wing, with shape held by rigid members
>or shroud lines or both.  Typically it had a single surface and was
>triangular.  A parafoil is a gliding parachute, with two surfaces kept
>apart by ram pressure and a rectangular shape.  Parafoils have largely
>replaced circular parachutes for high-performance sport parachuting.
>They are parachutes first and wings second.
[actually without the lift effect from the wing they are lousy parachutes]

You've got the terms just right, Henry.  I think the technical term
is "ram air inflated, semi rigid airfoil. It was invented and patented
by Domina Jalbert in the 1960s.  Pioneer has been working on
this recovery system for many years.  It is a very, very large ram
air parachute (several thousand sqaure feet I think; sport parachutes
for 1 person are 150-300 sqaure feet). 

The really tricky part is the deployment (reefing) system that allows the 
thing to open slowly so as not to damage the payload or the parachute.
An abrupt opening at high speed will cause the fabric to fail and the
parachute to self destruct, or at least subject the payload to such a
high deceleration force (>>15 G) as to damage it.

Because of the extreme altitudes they can afford to open it very slowly,
like one or two cells (ram air compartments) at a time.  I don't know
how this is accomplished but I'll try to find out from some parachute
designing friends of mine.
-- 
Blue skies,	| ...sun!aeras!tneale	| 
		| in flight:     N2103Q	|         The hurrieder I go
Tom Neale	| in freefall:   D8049	|         the behinder I get.
		| via the ether: WA1YUB	|