h a l f b a k e r yRecalculations place it at 0.4999.
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I havent thought through all the details, but then again, thats what half-bakery is all about. Now imagine this: a large ship (barge maybe) leaves port with a space craft (We'll call it Dutch Oven) of some kind on it. It goes out to sea, or maybe even a large lake and a crane from the barge sets the
bottom of Dutch Oven just below the water level. As it is doing this counter weights extend out the opposite side of the ship to preclude any dangerous tipping of the ship.
At the bottom of our beloved Dutch Oven is the first stage of the craft. This stage is then filled with water so the craft sinks into the sea. This is all carefully coordinated with divers and the crane operater on the ship. When Dutch Oven reaches the desired depth (I havent really researched this, so I'm not sure what the optimal depth is. Maybe I'm hoping someone will do it for me =} ) It is chained to the bottom with *very* strong chain of some sort. This chain will be attached to Dutch Oven with explosive clamps, not unlike the Saturn V mechanism.
Our trusty barge has another trick up its sleeve: a really good air pump. This will pump air into the first stage of Dutch Oven while it is securely fastened to the bottom of the sea. When it has been fully filled with air, and everyone takes a few steps back, the explosive clamps get E><p|_()Ded and SHWOOM goes our precious Dutch Oven.
Now, breaking the water surface will slow us down a little, but the area will be surrounded by a floating ring and a substance like soap will be mixed with the water to aid the couragous Dutch Oven on its expedition. After Dutch Oven has been succesfully launched, the conventional rockets will kick in.
(edited into paragraphs)
The Trident missile is launched underwater with compressed air.
http://www.chinfo.n...issiles/wep-d5.html
There’s no advantage to doing that, however, except for stealth. [ldischler, Aug 30 2005]
Proper Bouancy Equations
http://www.mfg.mtu..../forces/forces.html
I never was much cop at mathematics anyway. [zen_tom, Aug 30 2005]
[link]
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[marked–for–deletion] bad science. |
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Go to the swimming pool. swim down as deep as you can and let go of the ping pong ball. Watch as it does not lift more then a couple of inches above the surface. |
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I agree that the ideas at the halfbakery are not perfectly thought out as in: nice swing, no follow through. But this is just plain lazyness. |
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//Go to the swimming pool. swim down as deep as you can and let go of the ping pong ball. Watch as it does not lift more then a couple of inches above the surface.// This is not a system to launch it into space, this is just to give a space craft momentum so the conventional rockets can pull it up instead of struggling with the inertia of the ship to get it going. |
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zeno: the pingpong ball is suffering from being small and spherical - the surface tension is negating the lift. Try it with a larger missle-shaped object, and you'll get significant heights. |
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I mark that "marked-for-deletion" for deletion: loopy science, maybe, but not bad. |
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[Having spent many a happy hour launching paddle boards and other hydrodynamic objects into space.] [And you don't need to swim down as far as you can: merely stand on them.] |
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//(edited into paragraphs)// bun for consideration... |
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I lied, your user name sucks big time. |
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ha, yeah it does.
My bro had a site with his friends known as drunkbob.com, my e-mail used to me sober@drunkbob.com. I just shortened it. |
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<holds out sick bag at distance if you're wondering> |
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[DrCurry] I have never seen any kind of streamlind thing be it an empty bottle or a surfboard or what have you go up out of the water higher then it's own length, maybe a little. At the highest point it will still not be enough to aid in lift off. |
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Objects under water, floating to the top, do not acchieve sufficient speed to make any significant difference. |
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I must declare myself on the side of the bouyancists - where is HBman when you need him? <switches on croissant shaped searchlight> |
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I can't agree with Zeno's MFD, as the Trident missile is launched underwater, even if for a different reason. Generally, the science has to be much worse than this to be deleted. |
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Let us say that a spaceship is 2.0 million kilograms and is sent to the bottom of an ocean trench at a depth of say, 20,000 feet or 6096 metres. |
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Now let us assume that this spaceship is aero/hydro dynamic to some degree - so the friction coefficient in water might be something like C = 0.1, while in air, it may be more like C = 0.0001 (assuming density and resistance are analagous) |
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Now let's pump in a large volume of gas, or release some ballast, or whatever it is we need to do to make our spacecraft bouyant. |
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How bouyant? - let's go for a relative density of 0.5. |
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So, a 2.0 million kg craft, is now being displaced by 4.0 million kgs of water. What force would this impart on the vehicle? |
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Gravity remains at 1g or 10Nm/s and is a constant downforce - however, it is balanced out by the water, which is also working under gravity's pull, so I think we can keep that out of the equation for now. |
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So we have a net total of 4million kgs of thrust working on our craft for as long as it takes to travel 6000metres. |
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Since F = MA and A = F/M then |
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A = 4million/2millionkg
. = 2m/s/s |
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After travelling 6000 metres, accelerating at 2 m/s/s (allowing for our coefficient of friction) our rocket ship should be clocking something like 145 m/s by the time it reaches the surface! |
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Even at a more sedate accelaration rate of 0.1m/s/s, our craft will be hurtling upwards at 32m/s - which is quite a lot of momentum for 2 million kilgrams. |
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How strong would surface tension need to be in order to stop that? |
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[edit]I've just found some real bouyancy equations (yes, I've been making these up as I go along) unfortunately they are written in proper mathematical notation, including squiggles I don't understand. They may or may not agree with what I've just said - but someone should be able to make sense of them...[linky] |
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I dont care about bouncy equations --- perhaps if you sunk the entire ship and re-floated that there would be some advantage.... |
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Ever seen that movie with the funny storms that create a hole in the atmosphere --- that would reduce friction... |
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- Depth at 45 hundred feet, 48 hundred, 50 hundred! 5000 feet!
- Dear Lord, that's over 150 atmospheres of pressure.
- How many atmospheres can this ship withstand?
- Well it's a spaceship so I'd say anywhere between zero and one.
Futurama. |
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Just noting, for the benefit of future searchers, that a
buoyant buoy has buoyancy. |
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