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Had earth have been denser planet than it is...
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! | |
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Had earth have been denser planet than it is...
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. |
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