Generally , they have to be light and strong materials .
In airships , aluminum is used because it's light, strong and resistant to corrosion.
In air balloons , i think strong rubber made of a material with a high melting point so that it doesn't melt at high temperatures inside the balloon is used, as well as fabric ouside.
Hydrogen used to be used in airships.
gas is still used in airships to provide lift.
Hydrogen was once used to fill airships. Quite dangerous due to how flammable it is.
Hydrogen and helium are two elements that are kinda-sorta interchangeable in airships.
Hydrogen
Helium
because hydrogen used to be in those airships and since hydrogen is flammable it was very dangerous
Modern airships use Helium for lift which is non-combustible whereas in the past airships such as the Hindenburg used Hydrogen for lift which is highly combustible. In addition, modern airships take advantage of new alloys and polymers which give them a much stronger airframe.
Airships were often used to carry freight and passengers. But became unpopular after the advent of jets and other types of aircraft because they are slow. Initially they used fuel which made them highly flammable when accidents occured.
Hydrogen was the gas that was once used to filled airships. It is extremely plentiful and easy to produce. However, it is also extremely flammable and caused a few accidents. Helium is now used.
Zepplin
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