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#11
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inefficient turbo-pumps and Isp
Ian Woollard wrote:
Zoltan Szakaly wrote: The optimum thrust to weight at takeoff for a rocket is around 1.5, Actually no, it depends on the rocket, mainly on the staging scheme; some rockets (especially two or more stage rockets) can optimise at around 3g takeoff. Gentlemen; Allow me to introduce you to a concept called 'Max Q', or maximum aerodynamic dynamic pressure on a rocket (or generically, air vehicle) as it flies its ascent trajectory. If you accellerate too much, your nice thin payload shroud starts to have to be beefed up structurally and thermally to resist the ascent loading, as do the upper stage structures. Eventually, you need the same sorts of shielding that you need for re-entry, if you keep adding more and more low altitude velocity. There is a reason that most launch vehicles have T/W ratios around 1.25-1.35 at liftoff. -george william herbert |
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