h a l f b a k e r y"This may be bollocks, but it's lovely bollocks."
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[marked for a jelly] [marked for a prototype][marked for ...] |
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So when do I get to see the nomoreatmosphere on utube? |
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You would need a very high obtain fuel... |
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...... and a suitably refractory material for the wings. |
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This is quite bizarre! I simultaneously like and dislike this idea. For that you get a bun! [+] |
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It absolutely won't work on one plane, and absolutely will on a plane perpendicular to it. There is a certain argument that space-time is not quite euclidian. I.e. the planes are curved and are curved against one another, not at 90 deg to each other. This could result in motion in the intended direction. |
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I seem to remember an anecdote of a spaceman swimming through gravity towards his spaceship. Entirely supported by Einstein's theory of general relativety. Of course, it did take him a while. And possibly longer than the energy or information he could have stored. Therein lies the rub. |
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That roar I just heard was the relativity plane flying way over my head. |
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I don't understand what this has to do with Bernoulli, and I find things much easier to understand with a visual, so I did up a little photoshop of what I think you mean, [link]. |
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//I don't understand what this has to do with Bernoulli// Mel Brook's Space Balls? |
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// helicopter variant would make much more sense // |
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But also be far too loud and expensive. |
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[two fries], I just came from watching a set of Firefly vids. That looks like their generation of tech. Nice work. |
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//Amount of lift is greater than amount of drag// |
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I am somewhat suspicious of this assertion. |
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[bs] given the velocity of the exhaust I don't think a helicopter would make any sense at all, actually. Picture a spaceplane flying almost straight up at say 15deg from vertical. Alternatively flying horizontal and gradually increasing it's speed to requisite 7mi/s without as much of the also requisite 10m/s2 downwards thrust. |
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//I am somewhat suspicious...//
[insert paragraph explaining how an 11 hp engine can keep a half ton aircraft aloft at 100mph with almost negligible thrust, whereas a 29,000 lb-thrust rocket motor won't do you a damn bit of good if your wingless rocketship weighs 29,001 lbs] |
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The rocket exhaust increases the air pressure around the wings allowing it to fly: not a miracle: obviously you're not going to get much closer to the total energy released by combustion, but it should be more efficient. |
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This won't work. Thrust is given by mass * velocity / time. Passing your rocket exhaust over a wing will not favourably change any of these variables. A wing in an atmosphere is able to generate more lift than the thrust of the motor propelling the 'plane by deflecting a much larger mass of atmosphere in a downward direction than the propellor or jet deflects in a rearwards direction. |
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//A wing in an atmosphere...//
The exhaust plume *is* an atmosphere, albeit a rather thin one. |
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Yes, but there is no extra reaction mass to accelerate, and there's the rub. After passing over the wing the exhaust will be at best at the same velocity as before, but in a different direction, with nothing gained, and in practice will be slower than before, with a loss of thrust. |
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You may have been exposed to a common but incorrect explanation of lift, as suggested by your use of the word 'Bernoulli'. Wings produce lift by deflecting air downwards. Well designed aerofoils do so while minimising drag. Yes, they largely obey Bernoulli's equations, but so do all non-turbulent low viscosity flows. |
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Ummm to be honest there are two different types of lift and drag... |
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1) the ones that deflect air under the wing(increasing air pressure under the wing) |
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2) the ones that increase the path length over the top of the wing (decreasing air pressure on top of the wing) |
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//2) the ones that increase the path length over the top of the wing (decreasing air pressure on top of the wing)// Bingo! That's the incorrect explanation to which I was referring. |
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Both surfaces of the wing contribute to deflecting air downwards; the bottom in a direct way (the air has nowhere else to go), the top by the Coanda effect (which prevents the flow from separating). Pressure is higher than ambient on the bottom, and lower than ambient on the top, per Newton; flow is slower on the bottom than the top, per Bernoulli. Path length doesn't enter into it, as evidenced by the very good efficiancy of arbitrarily thin, but appropriately curved, wings (which are not used because they are not versatile w.r.t. angle of attack and are structurally weak). |
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The reason aerofoils produce lift is that they deflect a mass of air around a radius. There are some sums you can do to show that the pressure increases towards the outside of the radius, meaning that the top surface of the aerofoil will be at a lower pressure than Patm, and the lower surface, being at the outside of the lower radius will be at a higher pressure than Patm. The net result of this is a clever way of deflecting a large amount of air downwards in a more subtle way than used on the harrier jump jet. Also the reason helocopters have a downdraft. |
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If there isn't enough atmosphere to give lift normally, then the extra mass flow of your rocket fuel may allow a little more lift, but to be honest you're trying to create an oversized leaky directional exhaust nozzle for the rocket motor, which would be better used simply pointing further down. |
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Sorry, but fluid mechanics says no! |
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What Skrewloose is saying can be understood by moving FlyingToaster's spacecraft far away from the earth. The momentum change of the spacecraft has to balance the momentum change of the rocket exhaust, so if the spacecraft moves "up," then the center of mass of the exhaust has to be deflected in the opposite direction--"down". Much better to do this by using control jets to rotate the spacecraft. |
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It would make a good Catherine Wheel - the wing would make lift, and then pivot around the rocket. |
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