Ballonet
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A ballonet is an inflatable bag inside the outer envelope of an airship which, when inflated, reduces the volume available for the lifting gas, making it more dense. Because air is also denser than the lifting gas, inflating the ballonet reduces the overall lift, while deflating it increases lift. In this way, the ballonet can be used to adjust the lift as required.
Ballonets may typically be used in
The image illustrates the principle of a balloon within a balloon. The outer balloon represents the airship's outer envelope or gasbag, while the red inner balloon represents the ballonet. In an airship the ballonet would be much smaller relative to the size of the gasbag; for example, in the French airship
History
The ballonet was first described in 1783 by Jean Baptiste Meusnier, then a lieutenant in the French Army. However his own airship project was unsuccessful.
In 1784 professor
It was not until after Meusnier's death that the first successful application took flight. On 8 August 1884 the first practical airship, La France, flew for the first time.[4]
Ballonet air valves were originally of a butterfly type, actuated by springs. If pressure rose in the ballonet, a spring would pressure the spindle of the butterfly valve to turn, relieving the pressure. In more recent implementations, the valves are actuated electrically either by a linear actuator (driven open/closed) or a linear solenoid (spring return), the latter being the favored fail-to-safe arrangement.[citation needed]
References
- ISBN 978-0-203-02829-2.
- ^ Federal Aviation Administration - F.A.Aviation News, October 2001, Balloon Competitions and Events Around the Globe, Page 15
- ^ Federation Aeronautique Internationale, Ballooning Commission, Hall of Fame, Robert Brothers. Archived 2008-05-16 at the Wayback Machine
- ^ Walker, P.; Early Aviation at Farnborough, Vol. I: Balloons, Kites and Airships, Macdonald (1971), Page 176.