Naked Science Forum
General Science => General Science => Topic started by: arumalpra on 05/07/2016 06:26:57
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About floaitng runaway..
Land the plane in a samall floting runaway - say 500m - , lock the plane in the floting platform and driff forward untill it stops.
Any thoughts?
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You need to work out the effective inertia of the platform - mass inertial + water resistance - and then calculate the force on the landing gear when it is locked on.
Thinking about current aircraft I suspect the gear will take significant vertical jolt, but not a lot of backwards force.
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If the runway is not long enough fo rthe plane to stop it's not going to be long enough for the plane to take off again.
The runway will be very massive compaired to the plane. It will not accelerate to accomodate the movement of the plane much at all and if it did anything on it would be thrown about all over the place. Your truck with the steps on and the baggage waggons will be scattered into the sea. Not a good idea.
Why not just have a long enough runway in the first place?
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Idea is for low cost air craft carrier. Catapult launching system can be used for the take off.
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What deceleration force do you envisage for the passengers?
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What deceleration force do you envisage for the passengers?
Why won't this thing let me post a video link?
Is it just being awkward?
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The proposal was seriously made by Magnus and Geoffrey Pyke during WWII. They invented a material called Pykrete, composed of frozen sawdust and water - a cheap, simple composite that floats and is extremely strong. They envisaged enormous solid Pykrete aircraft carriers to be made in Canada and floated into the war theatres, with tugs or regular engines, and freezer units to maintain the hull shape. If bombed or torpedoed, they could be repaired by simply pouring water on the deck and turning up the freezer power. The deck could be surfaced with rubber or tarmac and used as a simple fighter base with a much longer runway than a conventional steel carrier, so landplanes (cheaper, simpler, bigger armament load, and easier to fly than naval aircraft) could be armed and fuelled in the front line.
There were some experiments at a few Canadian lakes but I don't think any were put into service.
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The idea is not to build long runaways. Short platform (could be even 100m) which works like the water rudder of a see plane. In other words the plane drift with the platform until stops.
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Time for some maths. You need to approach at 50 m/s to avoid stalling. Max final rate of descent is 10 ft/sec to avoid breaking the plane on touchdown (3 ft/sec to avoid passenger complaints). Assume a 10 ft swell. Aim for the threshold at the top of the swell so you don't crash into the stern of the ship. But when you arrive, it is at the bottom of the swell, so you won't touch down until you are at least halfway down the track.....
You can indeed get away with 100m runways, but only for microlights or fully navalised fighters with hefty undercarriages, arrester hooks, and certified insane pilots.
Sharing momentum with the ship is fine, but if the ship is too light, it will hurtle backwards as you catapult the plane forwards, and you may not reach flying speed before you fall off the deck.
Give me 1000m of pykrete any day!
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After a few failed attempts, SpaceX managed to do just such a thing...
See: (the landing starts at about the 2/3 position.)
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The idea is not to build long runaways. Short platform (could be even 100m) which works like the water rudder of a see plane. In other words the plane drift with the platform until stops.
A unique idea that just might work, if I read you right the floating platform should accelerate or synchronise with the of the airplane until it can gently touch down on it.
The atmosphere then becomes the runway or am I getting it wrong?
Alan
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I though touch down and then accelarate. your idea is kind of improvement or perhaps solving problems in what I sugested.
Accelerating, syncing, touchingdown and stops, really interesting.
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The idea is not to build long runaways. Short platform (could be even 100m) which works like the water rudder of a see plane. In other words the plane drift with the platform until stops.
A unique idea that just might work, if I read you right the floating platform should accelerate or synchronise with the of the airplane until it can gently touch down on it.
The atmosphere then becomes the runway or am I getting it wrong?
Alan
Alan Calverd suggests an approach speed of 50m/s, that's around 98 knots.
Large container ships can achieve 25kn, specialist racing power boats 50-80kn depending on sea state.
Probably worth working on 20kn as an achievable speed and calculating reduction in you runway length.
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Tailhooks stops planes in carriers. This floating platform does the same thing.
Pilot's aim is to snag the tail hook to arresting wires. In this case arresting wire is the floating platform.
Stability of the platform is a different matter.
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Tailhooks stops planes in carriers. This floating platform does the same thing.
Pilot's aim is to snag the tail hook to arresting wires. In this case arresting wire is the floating platform.
The inertia of the platform will mean rapid deceleration unless the arrest wire runs out to slow the plane down, you need to work out what distance you need to allow a reasonable deceleration.
I don't think commercial passengers will accept the G force that military pilots are used to.