A buoyancy control system is disclosed for maintaining a buoyant vehicle at a controlled depth by jettisoning either a heavy liquid or a light liquid. The control system monitors the depth of the buoyant vehicle and determines the direction and magnitude of vertical velocity. If it exceeds the threshold...http://www.google.de/patents/US5379267?utm_source=gb-gplus-sharePatent US5379267 - Buoyancy control system
