Patent ID: 8881501

Claim:
A vapor jet emitting device for producing thrust by emitting a jet of vapor produced from a liquid propellant, comprising: a propellant tank for storing a liquid propellant and supplying vapor produced by evaporation of part of the liquid propellant to an external location, including a tank body for storing the liquid propellant, and a mesh member arranged inside the tank body to cover a liquid surface of the liquid propellant to divide an interior of the tank body into a liquid propellant storing area and a gas storing area by utilizing surface tension of the liquid propellant, wherein the gas storing area of the tank body being kept at higher temperature than temperature in the liquid propellant storing area, and the tank body having a propellant inlet open into the liquid propellant storing area and a gas outlet open into the gas storing area; a thruster connected to the gas outlet of the tank body of the propellant tank by a gas supply line to emit a jet of vapor produced inside the tank body and supplied through the gas outlet; and a control section for obtaining temperature and pressure in the gas storing area of the tank body, setting a lower limit to which the pressure in the gas storing area is allowed to decrease by vapor discharge through the gas outlet, on the basis of a minimum pressure value allowing a liquid film of the liquid propellant to be maintained on the mesh member, calculating “on” time for a pulse causing vapor discharge through the gas outlet so that the vapor discharge will not result in a pressure decrease below the lower limit, and activating the thruster by feeding a pulse with the “on” time calculated.