In a nonrigid airship this is accomplished by incorporating separate, smaller envelopes called ballonets within the main envelope.
An airship that is going to take off at sea level and climb to 10,000 feet en route must have approximately 30 percent of its total envelope volume taken by air in the ballonets at take off to allow room for the expansion of helium during the climb.
Also, the airship's altitude, overall response and handling characteristics and flight control utilizes a system of ballonets
contained within each individual module, thereby creating a dynamically adjustable airship, WSGI said.
The rigger climbs about in the framework, testing his ballonets
and making sure that the ventilators are working properly and letting out the gas forced from the ship in its continual ride.
Hydrogen gas fills internal ballonets
, providing the lift necessary to keep the massive craft airborne.
located fore and aft in each of the hulls provide pressure control.