Path: utzoo!attcan!uunet!ksr!clj@ksr.com
From: clj@ksr.com (Chris Jones)
Newsgroups: sci.space.shuttle
Subject: Re: Gallileo vs Ulysses orbits to Jupiter
Message-ID: <808@ksr.com>
Date: 18 Sep 90 02:38:30 GMT
References: <1990Sep16.013630.22643@news.arc.nasa.gov> <15004@burdvax.PRC.Unisys.COM>
Sender: news@ksr.com
Reply-To: clj@ksr.com (Chris Jones)
Organization: Kendall Square Research Corp
Lines: 34
In-reply-to: techpubs@PRC.Unisys.COM (Technical Pub. Vince Short)

In article <15004@burdvax.PRC.Unisys.COM>, techpubs@PRC (Technical Pub. Vince Short) writes:
>In the STS-41 press kit, we find that:
>
>". . .  After being deployed from Discovery . . .  a two-stage Inertial 
>Upper Stage and a single-stage Payload Assist Module will boost Ulysses 
>on a trajectory that will take it to Jupiter in 16 months.  . . ."
>
>This is a direct transfer orbit to Jupiter.  
>
>My question: if this can be done for Ulysses (direct transfer orbit 
>to Jupiter), why couldn't it have been done for Gallileo which 
>was sent to Jupiter via a complex Venus-Earth-Earth gravity assist orbit.
>
>Gallileo was launched via Atlantis during mission STS-34 in October 1989. 
>However, it only used an Inertial Upper Stage (IUS) without the "assist" 
>of a Payload Assist Module (PAM) after the IUS burns.  
>
>Why no PAM on Gallileo? Is Gallileo so much heavier than Ulysses? Anyone 
>have any numbers (masses, delta v's, etc) for the craft and their orbits? 
>Was there just no way to attach a PAM between the IUS and Gallileo? 
>Or what? 

The mass is the thing.  Galileo is "so much heavier than Ulysses", so you've
got to take the gnergy from wherever you can get it.  Galileo has had a
convoluted history, involving almost every permutation of being two spacecraft
or one, launched from either the shuttle or some other (unmanned) booster,
involving the Shuttle-Centaur or not.  Once it was decided to fly it all
together (orbiter and descent package) on the Shuttle-Centaur, its
configuration was pretty well fixed.  Post Challenger, Centaur in the cargo bay
was thought to be a bad idea, so it was launched by an IUS, and it's going to
take this complicated trajectory to get Galileo to Jupiter, only 9 or 10 years
late (but still ahead of anything comparable).
--
Chris Jones    clj@ksr.com    {world,uunet,harvard}!ksr!clj