Patent GB-902055-A (GB)
Title: Rocket thrust control
Inventor: ABILD ROBERT NOBLE
IPC: F02K9/56
Filed: 1960-11-24
Abstract: 902,055. Fluid-pressure servomotor-control systems. UNITED AIRCRAFT CORPORATION. Nov. 24, 1960, No. 40409/60. Class 135. [Also in Group XXVI] A rocket engine comprises a combustion chamber, sources of liquid propellants, pumping means for delivering propellants from the sources to the combustion chamber and fluid motor means for driving the pumping means, also means for selecting a thrust level for the engine, means responsive to pressure in the combustion chamber for sensing the actual thrust level of the engine, servo motor means responsive to the difference between the selected thrust level and the actual thrust level to establish the selected thrust level, and means responsive to an operating condition of the pumping means to vary the servomotor output. The engine shown comprises a combustion chamber and thrust nozzle assembly 12, 14, a tank 16 for liquid fuel (e.g. liquid hydrogen), a tank 44 for liquid oxidizer (e.g. liquid fluorine or liquid oxygen), a fuel pump 20 and an oxidizer pump 48, the two pumps being driven by means of a turbine 32 which is actuated by vaporized fuel. The engine also comprises a helium tank 100, a main thrust control unit 180, a purge control unit 198, a fuel valve 40 in the fuel supply duct 38, the valve being operated by an actuator 90, and an oxidizer valve 60 and a propellant utilization valve 58 in the oxidizer supply duct 56. At starting, the fuel and oxidizer tanks are filled, the fuel filling the conduit 18, the pump 20 and the conduit 22 up to the check valve 24, these parts being surrounded by a cooling jacket. A portion of the liquid fuel will pass through the check valve 24 and pass through the conduit 22, jacket 26 around the combustion chamber and thrust nozzle, through conduit 30, by-pass conduit 76 (the by-pass control valve 78 being open) to the duct 38 up to the fuel valve 40 which is in the closed position, this portion of fuel being vaporized since the conduits are not jacketed. The oxidizer fills the conduit 46, the pump 48 and the conduit 56 up to the oxidizer valve 60 which is in the closed position, the utilization valve 58 being in an open position. The oxidizer conduit is surrounded by a jacket 96 to which helium is supplied under pressure from the tank 100 through line 98, the purpose of the jacket being to prevent leakage of liquid fluorine. Helium is also supplied from tank 100 through line 192 up to the needle valve 190 in the thrust control unit 180, the valve 190 being in the closed position. Helium is also supplied from the tank 100 through line 302 to the purge control unit 198. The unit 198 comprises four chambers 282, 284, 286, 288, each having a double-seated valve 296 on a stem 294, an end-plate 291 on the stem, a bellows 290 and a spring 292 bearing against the end-plate. Initially the valves 296 are in their lower positions against seatings 300, so that helium supplied through line 302 passes through ducts 306, 316 and 308, 314 to charge the compartments 278, 280 of the accumulator 268. Helium supplied through the line 302 to the chambers 282, 284 is dead-ended as the valves 296 are held against the seatings 300. To start the engine, the lever 182 on the thrust control unit 180 is moved to its low power position, movement of the lever rotating the cam 186, whereby the needle valve 190 is opened by pressure of the helium in the line 192, helium then flowing through line 194 to line 196. The righthand part of line 196 leads to the purge control unit 198 and helium is supplied through line 318 into the chambers 282, 284, 286, 288 causing the valves 296 to move to their upper positions against seatings 298. Helium in the duct 302 is thereby admitted through ducts 310, 312 to charge the compartments 272, 274 of the accumulator 266. At the same time, helium from the compartments 278, 280 of the accumulator 268 is released and flows through ducts 314, 328 and 316, 320, respectively. Helium passes through line 328 to the check-valve 330 which is opened by the pressure, the helium entering the fuel conduit 38 downstream of the valve 40, which is in the closed position, and so purging the conduit 38 and manifold 42. Helium passing through the line 320 similarly opens checkvalve 322 and purges the oxidizer conduit 56 downstream of the valve 60 which also is in the closed position. Helium flowing through the line 328 also passes through duct 336 to the thrust control unit 180, the pressure of the helium causing the needle valve 338 to open, whereby helium flows through duct 222 and line 224 and into the combustion chamber 12 which is thereby purged. Helium will also pass through the left-hand part of line 196 to the fuel valve actuator 90 which causes the fuel valve 40 to open, and to the oxidizer valve 60 which is also caused to open. Helium also passes from the line 196 through line 144 to the flapper valve nozzle 134 and to the bellows 122 in the utilization valve 58. Rotation of the lever 182 and cam 186 permits the fuel pressure in the line 204 to open the needle valve 202 whereupon fuel flows through the restriction 206 to the chamber 236 where it acts on the piston 240 which is loaded in the opposite direction by means of spring 242, the piston-rod 244 being connected by means of a lever 246 to the by-pass control valve 78. Fuel also passes from the restriction 206 to the duct 208 and nozzle 210, the opening of which is controlled by a flapper valve 212 which is pivotally mounted at 214. Rotation of the lever 182 also rotates cam 188 which by means of the spring-loaded guide piston 228 and follower 226 loads the flapper valve 212 in an anti-clockwise direction so tending to increase the area of the nozzle outlet 210. Build-up of pressure in the chamber 236 is thereby prevented and the by-pass valve 78 is maintained in the closed position so that all the fuel vapour in the conduit 30 acts on the turbine 32 and maximum power is available for driving the pumps. The by-pass valve 78 will remain closed until the combustion chamber pressure which is sensed by the bellows 220 through line 224 reaches such a value that the flapper valve 212 is moved clockwise so closing off the nozzle outlet 210, the consequent increase in pressure in the chamber 236 acting on the piston 240 to open the by-pass valve 78. Fuel and oxidizer flow to the combustion chamber at tank pressure as soon as the valves 40 and 60 are opened, and they ignite spontaneously upon mixture with each other. The heat of combustion of the chamber 12 will increase the vaporization of the fuel flowing in the jacket 26 and so increase the power of the turbine and so the output of the pumps. If the speed of the pumps should exceed a predetermined limit, the pressure of fuel acting through line 258 to the bellows 256 will cause the flapper valve 212 to move clockwise so closing off the nozzle outlet 210 whereupon the piston 240 will be forced downwardly to open the by-pass valve 78 and so less vaporized fuel passes to the turbine. A lever 248 pivoted to the casing at 252 and to the piston-rod 244 at 250 and acting on the flapper valve 212 by means of a spring 254 acts as a follow-up device. The pressures in the fuel and oxidizer tanks 16, 44 are communicated by lines 140, 136 to the bellows 130, 128, any difference in pressure causing movement of the flapper valve 126 which controls the outlet nozzle 134 of the helium duct 144. The duct 144 communicates with the bellows 122 of the propellant utilization valve 58, the position of the bullet member 110 being varied so as to control the flow area of oxidizer conduit 56 in proportion to the fuel flow rate. Upon shutdown of the engine, the lever 182 is moved to the off position and the cam 186 will close the two needle valves 190 and 202, the closing of needle valve 190 cutting off the helium signal pressure to the line 196, the pressure in the line being vented through duct 342. The fuel valve 40 will be closed by means of spring 92 and the oxidizer valve 60 will be closed by means of spring 170 and so flow of propellants will cease. The venting of the line 196 will cause the springs 292 in each of the purge control chambers 282, 284, 286, 288 to move the valves 296 to their lower positions against seatings 300. Helium from the chamber 272 will then flow through lines 310, 334, 328 to the check valve 330 and so purge the fuel conduit downstream of valve 40. Helium will also flow through line 336 and so purge the combustion chamber pressure-pipe 224. Also helium from the chamber 274 will pass through lines 312, 326, and 320 to check valve 322 and so purge the oxidizer conduit 56 downstream of valve 60. The lowering of valves 296 in the chambers 286, 288 permits the re-charging of the accumulator chambers 278, 280. Specifications 902,054 and 902,056 are referred to.