Thermal airship
From Wikipedia, the free encyclopedia
A thermal airship is an airship that generates its lift via a temperature differential between the gas inside its envelope and the ambient air. (This is in contrast to the more common use of Helium to provide lift.) Currently all thermal airships use hot air, as used in a hot air balloon, as their lifting gas. However, an airship that uses steam would also qualify as a thermal airship.
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[edit] Advantages/Disadvantages
Thermal airships have the advantage of being less expensive than helium-based airships. They are also routinely deflated after each flight and can be readily packed for storage and/or transport.
To date, there have been four major disadvantages when compared to helium-based airships. First, they have lower airspeeds. Second, they are difficult to handle on the ground if the ground wind is above 5 knots. Third, they have been difficult to steer -- particularly at low airspeeds. Fourth, they have typically lacked elevator (pitch) control so have tended to pitch upward/downward with changes in the throttle (a motion called 'porpoising').
In recent years, steering of these ships has improved somewhat. The most successful approaches have been to use a higher pressure the tail fin structures than in the rest of the envelope or to use an internal structure (see below.)
[edit] History
The first public flight of a hot air airship was made by Don Cameron (UK) of Cameron Balloons at the public at the Icicle Meet in January 1973. The aircraft reported took 3 years to develop.
[edit] Envelope structures
Most thermal airships are non-rigid. Some are pressurized. In some cases, the pressurized air is taken from a duct located behind the propeller. In other cases, the pressurized air comes from a separate fan.
In 2006, a new type of envelope employing a tensile membrane structure was developed by Skyacht Aircraft. This design uses an unpressurized envelope and an internal structure that uses ribs made of aluminum to keep the envelope in shape. When not in use, the structure folds up in a manner similar to an umbrella. The structure also permits the mounting of a steerable engine/propeller on the tail of the aircraft. The tail-mounted enables vectored thrust steering allowing a much tighter turns.
[edit] Operation
Like hot air balloons, thermal airships are first inflated partially with cold (ambient temperature) air. Once the envelopes are filled enough, a propane burner is ignited and the inflation is completed using heated air.
[edit] External links
- Hot air airship site
- The Flying Kettle Steam Balloon Project
- Gefa-Flug Hot Air Airships -- commercial aircraft company
- Cameron Hot Air Airships -- commercial aircraft company
- Lindstrand Hot Air Airships -- commercial aircraft company
- Skyacht Personal Blimp -- company developing a hot air airship
- World Championships -- Sixth World Airship Championships held in Gatineau, Quebec on the 3rd of September, 1998.
