Abstract: A rocket engine shaft seal which prevents leakage from escaping from the pump to the turbine along the shaft 1. The seal has a bellows spring 8 for pushing the floating ring seal 2 into contact with the mating ring 4 when the rocket engine is off, thus sealing the liquid in the pump section more reliably. When the engine is on, the pressure of the fuel will overcome the force of the bellows spring 8, moving the floating ring seal 2 away from contact with the mating ring 4, so as to save wear on the face contact portion 5 of the floating ring seal and preserve a good seal when the engine is off. The floating ring seal 2 has an inner diameter 11 for forming a seal with the shaft 1. The shaft 1 may have a labyrinth on it for forming a labyrinth seal with the floating ring seal 2, or with the floating ring seal and the bellows adapter's arm portion 13 for forming a longer labyrinth seal.