CONTROLLABLE BUOYANT SYSTEM AND METHOD

A controllable buoyant system (10) includes a support structure having a sealed hollow enclosure (12) containing a first gas and surrounded by a second gas, either the first gas or the second gas being lighter than ambient air. The hollow enclosure is pre- filled with the first gas via a one-way valve that prevents the first gas escaping and an altitude sensor (14) generates an altitude signal indicative of a height of the support structure. A height transducer (17, 21, 61, 66, 67, 68) coupled to the hollow enclosure is responsive to the altitude signal for varying the buoyancy of the support structure. A controller (15) is coupled to the altitude sensor and to the height transducer and is responsive to the altitude signal and to at least one reference altitude signal for automatically controlling the height transducer in order to maintain the support structure buoyant at the preset altitude.