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human
Eli5: why are submarines cigar shaped but jets pointy?

Both water and air are fluids but jets and missiles are pointy whereas submarines and torpedoes are cigar shaped. Why is that?

Edit: Grammar

Edit2: why is pointy better for supersonic? Why is round better for subsonic?
gpt
Air is a compressible gas whereas water is usually a non compressible fluid. The air density vs water density is also very different. With those two variables the dynamics at each medium are widely different, and hence you have the hydrodynamics and the aerodynamics.

Making a submarine very pointy creates a weak structure that will not be able to whitstand the compression deep under the sea, and it will also make the submarine hard to steer because of its relatively slow speed (compared to airplanes).

An airplane with a cigar shape is actually possible (as long as it has wings) and those type of designs are used for slower and bigger cargo planes. High speed jets require a geometry that allows them to break the sound barrier more easliy, and thats the main reason for the pointy geometry. Air is usually considered uncompressible at subsonic speeds, once the speed of sound is reached, the air resistance becomes exponentially more "thick" and the calculations for the aerodynamics start considering air as a compressible fluid. A plane can be made to be good at subsonic speed or good at supersonic speed, but not the two at the same time. Pointy geometry is good at supersonic speed.