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A blimp or zeppelin can fly without using energy. If it's engines are turned off, it can travel with the wind. I think you're asking - can it be done while having control over where you go, or how fast, while using arbitrarily little fuel? This is an old idea, and it has been tried. It is possible, but so far not practical. To find out more, just Google ...


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The aileron will point in the direction that would cause the most drag, it will also flutter a bit. And if by increased alpha you mean the aircraft is flying with high alpha like a jet going super slowly forward at a constant altitude with the nose pointing way up into the air at a high angle, then technically the ailerons would go up in relation to their ...


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Wings provide lift because they direct air downwards. They direct air downwards in two ways. In part, the bottom of the wing slopes downward a bit and just pushes the air down as it moves forward through the air. But this is a small effect. The top of the wing is more important. The top of the wing pulls the air down partially by providing a ramp. The rear ...


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The Solar Impulse flies without fuel, so the answer to the question in your title is yes. In theory you could design an airship that used very little energy. It would have to become lighter than air to take off, say by shedding some ballast, fly to where it is going, and become heavier or catch a landing rope to land. If that sounds like a helium balloon, ...


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It's a hoax. Think of a submarine—it can go towards and away from the center of the Earth due to gravity and buoyancy respectively, but it cannot do this without changing its density. And it cannot change its density without fuel. From the U.S. Office of Naval Research: To descend, water is allowed to flow in through the bottom of the submarine: To ...


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Essentially a fixed-wing aircraft flies because it moves through the air and has a fixed wing which is angled to the direction of airflow. A component of the drag force acting on the wing acts in the direction (up) opposite to the direction (down) of the aircraft's weight force. An aeroplane wing acts like a weather vane responding to the relative flow of ...


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The answer to the main question is no. The reason it is no, is because your reasoning is flawed. In addition to the vacuum created in front of the propeller, there is the impulse applied to the propeller by the reaction to the air being pushed away from the propeller. Although the force due to the vacuum reaches a limit, the one due to the impulse does not. ...


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Not physically, but practically there are (currently) better alternatives. The limiting issue with propellers is similar to the limiting issue with helicopters: propellers work like wing sections in that they must accelerate flow to work; when you're near the speed of sound, this means you are going to cause shocks to form, and this issue is particularly ...


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Your question, the way it is put, allows one fast answer: No, in principle, this airplane can fall with higher velocity then 1M. However - what only you need is to accelerate the air molecules around so that you gain momentum (and speed). (1) In principle, it is not forbidden to invent such a propeller. But normally, with a classical design, you will have ...


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Don't forget that the aeroplane will be moving forward, so it's not relying on a vacuum filling ahead of the propellor to supply the latter with air. Now I daresay there are good engineering reasons why propellors are not efficient and even impracticable for supersonic flight, but I don't think there is a fundamental physics theoretical reason ruling them ...


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A propeller can work at supersonic speeds because as it approaches those speeds it is catching up with the air molecules as it moves. So you don't have to "wait" for the molecules to move into the vacuum you create. In other words the thrust of a propeller does not go to zero just because the plane reaches a certain speed. But it is not enough to have ...


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There is a difference - but not exactly why you think. There are prevailing winds around the earth - these used to be called the "Trade Winds" because traders, knowing the direction of the wind, knew how best to navigate the globe. Basically, on the equator (in the tropics) they flow from east to west, and at higher latitudes they flow from west to east: ...



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