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#181
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Soyuz TMA-12 faulty
Jochem Huhmann wrote:
(Derek Lyons) writes: At the most important moments of successful takeoff and landing the velocities are the same, being zero. It must, therefore, be possible to use the jets at the point of liftoff. The problem isn't that short period when the velocity is zero, but the rather much longer period when the velocity in nonzero. The terminal velocity of a blunt vehicle consisting mainly of empty tanks isn't that high, though. Still, making it work in both cases wouldn't be exactly easy, I think. Just to be more precise. It wouldn't be very difficult to make it work in both cases in the sense that it wouldn't be very difficult to have the jet engine provide lift in both case. But you don't just want it to work, you want it to be useful, meaning you want it to be better than just using the rocket engine that you already have. I think it is unlikely that it would be worth it to carry a jet engine all the way to space just so you can have it for a few seconds at landing. The extra rocket fuel needed to carry it to orbit would probably be more than what it saves at landing. And if you do build a rocket landing vertically using a jet engine, you would probably want to optimize it for landing, if you want to use it for both take off and landing you might end up making heavier to the point that it again increases the overall cost. If you are carrying a jet engine at take off it might very well be wise to use it, but it isn't obvious to me that it is. Note that there are some drawbacks in using the rocket engine for landing also. For landing you need an engine capable of giving about a 1 g push to the mostly empty rocket. That is much less than a rocket giving a, let's say, 3 g push to the fully loaded rocket. Deep throttling of rocket engines have their own complications. But I think that for the rocket engine case, it is much easier to solve the problem. You would probably want to have several engines, one of which is optimized for landing and the other main engines being shutdown at landing. Alain Fournier |
#182
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Soyuz TMA-12 faulty
David Lesher wrote: Were they from Kansas? Like Hobbits, Munchkins were far too fond of food to fit through 9" wide intake openings. Now you got me started on doing "The Wizard Of Skunk Works" songs: "Come out, come out, wherever you are, and meet the team that built the Shooting Star." "The Northrop "Fang" is not merely dead, it's really most sincerely dead." "We represent the RCS cross-section team, the RCS cross-section team, the RCS cross-section team.... and in the name of the RCS cross-section team...we want you to see our new Have Blue." "Let the word be quickly spread, that evil old empire is finally dead!" "Hi-ho, the empire's dead! Which old empire - the Soviet empire! Hi-ho, the Soviet empire is dead! It's gone where the commies go, below...below...below...below...straight to hell, that's where they go! Hi-ho, the USSR is dead!" "You've always had the power to get back home again; just click those Hopeless Diamond slippers together and say 'There's no place like Nellis...there's no place like Nellis'." :-D Pat |
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