[Eli5] Why do planes need huge wings but space rockets don’t ?
In: Physics
Planes use wings to generate lift from forward flight; as the plane moves forwards through the air, some of the air is deflected downwards by the wing. Given the conservation of momentum, the force that the plane pushes down on the deflected air is equal and opposite to the amount of force that the air pushes back on the plane, thus if you deflect *enough* air such that the force is at least equal to the weight of the plane, the plane will remain in the air.
Rockets don’t care about lift, because there is no air in space, and because the part of the atmosphere that they do most of their flying in has very little air in it. This is deliberate because the same air that can be used to generate lift will also generate drag, and enough drag can actually seriously damage the rocket. Thus, a rocket will generally shoot straight up relatively slowly until it clears the thicker part of the atmosphere, and then tip over and throttle up to full power in order to get up to orbital velocity.
Ones going vertical, the other horizontal. One is breaking free of gravity and air. The other balancing lift against gravity.
Space rockets do not intend to generate lift with the wings. Where rockets do have wings it is mostly to help control it through the atmosphere. The exception to this was the Space Shuttle which had rather large wings as the Air Force wanted it to be able to glide for long distances so they could perform certain mission profiles which would have made it reenter the atmosphere far from any landing site. They never performed any of these mission profiles. The wings were however quite small compared to airplanes as they had a lot of height to use when gliding meaning that they had no issue doing more falling then gliding.
The wings provide lift through a pressure differential. Something that blew my mind when I really thought about it is that the entire weight of the plane is supported by the wings. You can pick up a plane by the wings theoretically.
Rockets don’t need lift to stay in the air. They have rocket fuel and go more or less straight up for a lot of the flight. They do spiral though.
Planes and rockets fly using different principles.
Planes take advantage of aerodynamics, they use wings that create lift when air moves over them. This allows a plane to fly without needing to use a tremendous amount of force to counter gravity. You only need thrust to push the aircraft forward fast enough to generate lift.
Rockets meanwhile are purely brute force. Chemical propellants create thrust to counter gravity and accelerate them into space. Rockets need to do this because there is no air in space to generate lift, and having wings at some point actually only creates drag and slows the rocket down.
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