Patent ID: 8061659

Claim:
A method of detecting complete emptying of a liquid propellant from at least one of two surface tension tanks in an artificial satellite, the method including: providing emptying pipes on board the satellite wherein each said tank is connected by a respective emptying pipe having a respective tank-emptying valve mounted therein to at least one feed pipe, providing each of said feed pipes with a respective feed valve mounted therein for feeding a nozzle or a plurality of nozzles in a propulsion system for controlling the attitude and/or orbit of the satellite, providing each of said feed pipes with at least a respective nozzle-feed valve mounted therein that is controlled to open and close intermittently enabling liquid propellant to be fed from said tank, intermittently and during alternating periods, to said nozzle or plurality of nozzles at the respective downstream ends of the feed pipes, detecting pressure oscillation waves that result from opening and closing said feed valve and that travel along the feed and emptying pipes from the downstream feed valve towards said upstream tank by using at least one pressure sensor mounted in the emptying pipe or the feed pipe between said emptying valve and said feed valve, and then following operation of said feed valve, detecting the at least partial damping or disappearance of said pressure oscillation waves indicating that the transition between the liquid propellant and a propellant pressurization gas has gone past the pressure sensor, and indicating that the tank is completely empty.