Heated gas intermittent thrustor or rocket engine

1,002,469. Utilizing energy of radiations. THOMPSON RAMO WOOLDRIDGE Inc. April 8, 1964 [April 8, 1963], No. 14494/64. Heading G6P. [Also in Divisions B7 and F1] A heated gas rocket motor or thrustor which is used intermittently comprises means for storing a propellant fluid, a radioisotope capsule, heat exchanger means surrounding the capsule for storing heat emitted therefrom, the heat exchanger means having passages therethrough, an inlet connected to the propellant storing means, and an outlet. At least one propulsion nozzle is connected to the outlet, and control means is provided so as to permit intermittent thrusting by expulsion of heated propellant through the nozzle and alternate periods of heat storage in the heat exchanger. The motor is suitable for attitude control for a space vehicle. The embodiment of Fig. 1 comprises a reservoir 11 which contains a suitable volatile liquid such as liquid hydrogen or ammonia, a heating and heat storage unit 13, and a propulsion nozzle 21, the three elements being connected by ducting 18. The heating unit 13 is of spherical form and has a radioactive capsule 15 disposed at the centre. The unit is covered with insulation material 14 and is provided with a series of concentric perforated spherical walls 16, 17, there being a core of high temperature metallic gauze disposed within the inner wall 17. Working fluid flows from the reservoir 11 to the heating unit 13, assuming the valve 12 is open, and flows inwardly to the space within the inner wall 17 becoming vaporized and superheated by the heat radiated from the capsule 15. Assuming the valve 19 to be closed so that the vaporized fluid cannot escape, the fluid serves as a heat storage material which stores heat emitted by the capsule. When the valve 19 is opened the vaporized fluid discharges through the nozzle 21 to impart thrust to the vehicle. A pressureactuated device 22 is connected to the heater unit and serves to open or close a switch 23 which controls the opening of valve 12, the valve 12 being closed when the switch 23 is in the open position shown. The switch 24 when in the full line position shown acts to allow the valve 19 to open so that the superheated vapour from the heater 13 will discharge through the nozzle 21. When the thrust operation is finished the switch 24 is moved to the position shown by broken lines. The valve 19 will close and the switch 23 will move to the closed position as a result of the reduced pressure within the heater and the valve 12 will thus open whereby more fluid will flow into the heater to be vaporized and superheated ready for the next thrust operation. In Fig. 2, the heater unit comprises a cylindrical container 33 disposed within the outer shell 32, heat insulating material 38 being disposed therebetween. The container 33 has a series of open tubes extending therethrough through which working fluid can pass from an inlet 36 to an outlet 37 and thence through thrust nozzles 44, 45, 46 controlled by valves 41, 42, 43, respectively. The container 33 has three radio-active capsules 31 disposed along the axis thereof and the container is filled with fluid such as silicon or lithium hydride which becomes heated by radiation from the capsules 31 and serves to transfer heat to the working fluid when it is allowed to pass through the tubes. The transfer of heat from the transfer fluid to the working fluid causes the fluid to gradually solidify, the material again becoming liquid and then vapour when the thrusting period is terminated and the flow of working fluid stopped. A thermostatically controlled flap may be provided in the insulating material, the flap opening when a predetermined temperature of the heating unit is reached whereby excess heat generated by the radioisotope capsules may be radiated outwardly. The radioisotope material may be plutonium 238, curium 242, curium 244 or polonium 210; alternatively it may be strontium 90 or cerium 144. Specification 997,276 is referred to.