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Re: P3D Launcher Vehicles



Unless you've been following this discussion or doing your homework (you have,
Jon, right?), let me expand on Richard's comments.

   The Ariane 5 delivers the satellite into orbit with more energy that the
Ariane 4. More energy delivered by the 'lift vehicle' means less energy
needs to be delivered by the satellite to reach a target orbit. (Orbits can
be said to have a particular 'energy content'. Higher orbits = more energy.)
The P3D satellite only has so much propulsion fuel = energy *it* can add
to its own orbit. The more it uses to get *into* its target orbit, the less
it has to maintain its orbit, working against drag and other complicated
(to me) jiggling of it out of orbit by other influences (the moon's gravity,
atmospheric drag when it goes by the earth at perigee, or close-point, etc.)
The Ariane 4, when considered, would have required much of the onboard fuel
to just get into the target orbit, from what I understand, and would have
left very little for orbital maintenance.

   I stand open to be corrected but I think this explanation is approximately
correct.

Best 73's
--Paul, wa0rse@amsat.org

At 12:06 -0600 1/19/00, Richard W L Limebear wrote:
 > Jon Ogden writes:
 >
 >> Why is P3D going up on an Ariane 5 and not an Ariane 4?  Wouldn't the 4 have
 >> been more readily available?
 >
 >The -4 only delivers a ~200 Km perigee. With the -5, you get ~500 Km.
 >
 >And we're gonna need every last drop of fuel we can squeeze in.
 >
 >73
 >Richard W L Limebear G3RWL
 >g3rwl@amsat.org
 >FOC # 1188
 >
 >          So many beautiful girls ..... (sob) so little time
 >----
 >Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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