An airship, also known as a dirigible or blimp, is a type of lighter-than-air aircraft that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms. Unlike aerodynamic aircraft such as airplanes and helicopters, airships are lifted off the ground by lighter gases, such as helium or hydrogen. Airships were famous in the early 20th century before the development of large airplanes and helicopters. They were often used for long-distance travel, cargo transport, and military surveillance.
There are three main types of airships:
- Non-rigid airships (or blimps), which maintain their shape due to the pressure of the lifting gas within the envelope and lack an internal framework.
- Semi-rigid airships, which have some supporting structure but the shape of the envelope is maintained mainly by the internal pressure of the lifting gas.
- Rigid airships (or Zeppelins), which have an internal framework that maintains the shape of the aircraft, within which the lifting gas is contained in one or more gas bags or cells.
Despite their diminished role today, airships are still used for advertising, sightseeing, surveillance, and research purposes, and ongoing efforts are to revive them for uses such as cargo transport.