Re: Had earth have been denser planet than it is...

[Henry Spencer]

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.

>...the rocket after
>the probe has been uncoupled could be sent on a crash course with
>Jupiter or Saturn or Uranus or Neptune, so their isn't an old reactor
>floating around in solar orbit, as a future menace.

As has already been noted, it's very unlikely that there would be a planet
in a convenient position for this, and in any case the reactor (like the
probe) would be far beyond solar escape velocity by cutoff. It would end
up in interstellar space, far away from anything that might be harmed.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Jordin Kare]

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.