[Bill Moore]

Originally Posted by Roger

Non-rigid airships (Wikipedia)

Blimps don't have a frame holding them together, as opposed to rigid airships. Blimps need a constant internal pressure that is higher than the surrounding air pressure to maintain their shape. The Goodyear Blimp has no frame.

Zeppelins are rigid airships, which means a skin is put over a frame. Because of the frame, they could be built larger and lift heavier loads. A Zeppelin (capital z) is a type of rigid airship (brand name, if you will) created by Ferdinand von Zeppelin.

Dirigibles are steerable airships (from the French dirigeable, "steerable"). Wiki is sort of vague about the differences, and generally thinks dirigibles don't generally refer to blimps.

Hot air balloons use a different method, that of hot air is lighter than cold air. I'm sure there must be an easy science experiment somewhere on the internet.

Don't miss the base link also to Airship, which covers the long history of lighter than air travel, and the U.S. Navy's attempts with its' small fleet of airships in the 20's and 30's. There also is a discussion of current research being done with these vehicles.