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Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!decvax!bellcore!petrus!karn
From: karn@petrus.UUCP (Phil R. Karn)
Newsgroups: net.space
Subject: Re: communications satellite insurance rates
Message-ID: <563@petrus.UUCP>
Date: Tue, 17-Sep-85 23:47:17 EDT
Article-I.D.: petrus.563
Posted: Tue Sep 17 23:47:17 1985
Date-Received: Fri, 20-Sep-85 04:48:17 EDT
References: <536@petrus.UUCP> <528@riccb.UUCP> <539@petrus.UUCP> <530@riccb.UUCP>
Organization: Bell Communications Research, Inc
Lines: 45

> Right, but the vast majority of failures to get satellites on station are
> due to a problem while the payload is still within the launcher.

True. What do you consider to be the "launcher"? Does this include problems
with the AKMs? My point was just that you should compare apples with apples
by considering the PAMs to be part of the "shuttle launcher" when comparing
it to Ariane.

> Only to a limit.  There are a lot of satellites that simply cannot be lifted
> (to GEO transfer orbit) by Ariane, Delta, Atlas, or even Titan because of
> their maximum capacity.  But since you were probably intending this to apply
> strictly to communications satellites (of which the HS-376 type is typical)
> this point is moot.

F'rinstance? Both Shuttle and Ariane (with its "SYLDA" - SYsteme Lancement
Duel Ariane) are usually flown these days with multiple payloads. Very few
communications satellites require (or can afford!) the full capacity of
either a Shuttle or Ariane.

> You don't need it when you're safely tucked away in the womb of the shuttle
> cargo bay.  Ariane can do no such thing because it does not provide as
> "friendly" an environment as the shuttle does.

Not quite. Read some of the back issues of AW&ST regarding the hassles SBS
went through as the pioneer Shuttle customer.  A major problem was the
nasty thermal environment in the cargo bay. A payload like a communications
satellite can withstand only brief periods (minutes to hours) in continuous
shadow or sunlight. Beyond that, you start melting solar arrays or freezing
batteries. The "baby buggy" shade now used with all HS-376-class payloads
was the result. It has to be opened for the bay doors to close (i.e., during
launch), but then it has to be closed quickly after achieving orbit in order
to protect the payload. As you know, this was a problem on the last flight
with the Australian satellite and it had to be deployed early. My question
is, why can't they just plan to deploy satellites early in the first place
and get it over with? Once a satellite like the HS-376 is spun up and
deployed (with the proper attitude) it is quite able to take care of itself.

Ariane gets you spun up and deployed at the proper attitude (e.g., normal
to the sun line) within 15 minutes of leaving the pad, and by then the
satellite temperature has hardly had a chance to change much from the
nice 20C given it by the ground purge system.

(more to follow)

Phil