US Patent 8167240 System and methods for buoyancy management in an airship

An airship comprising a hull configured to be inflated with a first gas; a ballonet in the hull, the ballonet configured to be inflated with a second gas that is heavier than the first gas; a fan configured to draw the second gas into the ballonet; an inflatable landing system; a duct configured in the ballonet to allow access to components in the airship; and a valve coupled to the ballonet. The valve provides a pathway for air to flow between the ballonet and a plenum chamber, the plenum chamber is formed by the airship, a landing surface, and the inflatable landing system when the inflatable landing system is in contact with the landing surface.