Henry Spencer wrote:

In article ,
Christopher wrote:
(The archetypal example of big rocket with tiny payload because of high
delta-V requirement was the original Pluto Fast Flyby proposal...

For a Pluto Fast Flyby wouldn't it be more feasable to have a small
nuclear thermal rocket sent on its way from LEO...

There was no possibility of such a thing being available -- and thus
feasible in any practical sense -- for the mid-90s launch that PFF wanted.
The Titan IV plus upper stages was perfectly feasible, essentially off
the shelf... just horribly expensive, at a time when spending the better
part of a billion on one planetary mission simply wasn't in the cards.


I was on the PFF mission team, as a liaison with DOE/LLNL (because the
PFF group wanted to use Clementine-type sensors and guidance). No one
really liked the multiple stages, but the only alternative seemed to be
a series of planetary flyby maneuvers, which, because of the
requirements on the position of Jupiter, couldn't be done until several
years after the planned launch of PFF.

I proposed to the team that they consider a very modest "quick and
dirty" solar thermal stage -- roughly 10 kW thermal power, 800 s Isp, as
I recall -- as an alternative to the stacked solids. Such a stage would
normally be pretty useless, but for this particular mission, it made
sense. In particular, given the huge Titan shroud, there was plenty of
room for a rigid 3+ meter mirror as a solar collector, and for a large
LH2 tank. Also, the delta-V requirements were so high that even given
the inefficiency of a several week long Solar-thermal burn compared to a
short deep-in-Earth's-gravity-well solid motor burn, the Solar-thermal
stage was a lot lighter.

Hoppy Price, the system engineer, liked the idea and wanted to pursue
it, at least a little, but it was too unproven for the rest of the team
(and especially the higher-up JPL management) so it never went anywhere.

--
Jordin Kare

"Point and click" means you're out of ammo.