"In early dirigibles the lifting gas used was hydrogen, due to its high lifting capacity and ready availability. Helium gas has almost the same lifting capacity and is not flammable, unlike hydrogen, but is rare and relatively expensive. Significant amounts were first discovered in the United States and for a while helium was only used for airships in that country. Most airships built since the 1960s have used helium, though some have used hot air.[note 1]
The envelope of an airship may form the gasbag, or it may contain a number of gas-filled cells. An airship also has engines, crew, and optionally also payload accommodation, typically housed in one or more gondolas suspended below the envelope." - (en.wikipedia.org 29.02.2020)
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