How does a large aircraft such as a blimp float in air?

Answer 1

Blimps are essentially non-rigid structures, that is they are generally mainly composed

of a single large, flexible gas-bag supporting a gondola with controls and an engine.

The gas-bag is filled with gas, usually helium, to attain flight. This gas can be vented

or increased to change altitude. The Goodyear blimps are a very good example of this

type of aircraft.

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All of the gas-filled flying things ... blimps, zeppelins, dirigibles, hot-air balloons,

party balloons, etc. ... are called "lighter-than-air" craft, and that should be your

first clue. Each of them is lighter than the same volume of air. It floats in air for the

same reason that a lighter-than-water object floats in water ... by being lighter than

an equal volume of whatever substance it's floating in. That's a less scary way of saying

that its aggregate density is less than the density of the surrounding fluid. Any object

surrounded by fluid is held up by a force equal to the weight of the fluid that it pushes

out of the way. If it pushes aside enough fluid to weigh more than the object itself does,

then the object rises, as sure as a beach-ball pops up from the bottom of the pool.

Answer 2

A blimp floats in the air because it is filled with a gas that is less dense than the surrounding air, such as helium. This creates a lifting force that is greater than the weight of the blimp, allowing it to float. The blimp can also control its altitude by adjusting the amount of gas in its envelope.