Assessment of a thrust induced by a water-fueled magnetron sputtering source

Water-fueled low-pressure discharge is sustained by a magnetron sputtering source consisting of a copper cathode and a ring anode, and a force exerted to a target plate located downstream of the source is measured, where the water gas is continuously introduced by using a mass flow controller operational for a differential pressure lower than the water vaper pressure at a room temperature. The source and the dc power supply for the discharge are electrically floating from the grounded vacuum chamber to ensure zero net current between the source and the surroundings; the mass ejection of the sputtered and electrically neutral copper atoms or clusters are responsible for the thrust generation, while the ionized particles do not contribute to the thrust generation due to the plasma confinement near the cathode. The measurement shows the thrust generation of about 3–4 mN/kW at a discharge power level of about 80 W. The results would potentially lead a propulsion device with no neutralizer and no high-pressure gas storage tank.