REACTION JET CONTROL SYSTEM

Abstract: A reaction jet control system for a flying vehicle, the system comprising pairs (3, 4 and 5, 6) of jet reaction nozzles with associated gas flow supply ducts, the duct between two nozzles (3, 4) of any one pair including a first gas diverter valve (11B) and the duct between two pairs of nozzles including a second gas diverter valve (11A). This arrangement ensures accurate balancing of the gas flows between the nozzles and gives economy in use of the fuel supply.

Description: REACTION JET CONTROL SYSTEM This invention relates to a reaction jet control system. It relates particularly to a system for use in a vehicle capable of flight outside the earth's atmosphere where reaction jets are used to control attitude and flight direction. In providing a jet control system it is necessary for the system to be able to effect the necessary changes in vehicle attitude and flight direction whilst maintaining economy of the fuel gas supply. It is quite likely that the gas for the jet reaction nozzles would be derived from a solid propellent charge which, once ignited, would burn continuously at a steady rate until all the fuel is consumed. Since the gas pressure within a combustion chamber burning a solid propellant charge needs to be maintained within predetermined limits to avoid too slow or too fast burning of the charge, it is not in general possible to modify the gas flow through one nozzle without making a corresponding change to the flow through a different nozzle. The present invention was devised in order to provide a simple and reliable way of controlling the jet flows which would give an economy in the number of mechanical parts needed. -2- According to the invention, there is provided a reaction jet control system for a flying vehicle, the system comprising pairs of jet reaction nozzles with associated gas flow supply ducts, the duct between two nozzles of any one pair including a first gas diverter valve, and the duct between two pairs of nozzles including a second gas diverter valve. Preferably, the said first gas diverter valve is a fluidic valve capable of controlling output gas flows without mechanical moving parts. The said fluidic valve may be a momentum interaction amplifier valve. The said flui ic amplifier valve may have two control parts responsive to fluid pressure inputs, the said control parts being connected to a gas pressure balance valve. Conveniently, the said gas pressure balance valve is a gas flapper valve. The first diverter valve and the second diverter valve nay each be connected to respective gas pressure balance valves. By way of example, some particular embodiments of the invention will now be described with reference to the accompanying drawings , in which: Figure 1 is a side view of a jet vehicle showing one arrangement of jet nozzles. Figure 2 is a cross-sectional view taken on the line II-II of Figure 1, Figure 3 is an enlargement of Figure 2 showing details of the nozzle alignment. Figure 4 is a block diagram showing a diverter valve arrangement. Figure S shows a diverter arrangement using spool valves. Figure 6 is a rotary diverter valve. Figure 7 is a fluidic diverter valve. Figure 8 shows a schematic diagram symbol for a fluidic diverter valve. Figure 9 is a flapper valve. Figure 10 is a schematic diagram of a fluidic diverter and flapper valve circuit, and. Figure 11 is a schematic control system for four nozzles. Figure 1 shows a jet vehicle 1 suitable for flying at extremely high altitude or in space, and which utilises a system of reaction jets from nozzles 2 to control attitude and flight direction. The main thrust nozzles of the vehicle have not been shown. The cross-sectional view of Figure 2 shows that two jet nozzles on each side at the front part of the vehicle are capable of controlling Rolling Moment L, Lateral Thrust Y and Vertical Thrust Z. A similar set of four nozzles at the vehicle rear can be used in conjunction with the front nozzles to give additional control of the vehicle attitude. λs shown in Figure 3, the front nozzles, 3, 4, 5 and 6 can be operated in various arrangements by a control system 7 which has valves to divert a gas supply to different pairs of the nozzles in turn. Thus the jet nozzle 3 can have a jet efflux 8 and this will produce a thrust acting along the line 9 on the vehicle body. In such a vehicle, it is quite likely that the gas for the jet reaction nozzles will be derived from a solid propellant charge, which once ignited would burn continuously at a steady rate until all the fuel is consumed. In these circumstances it is evident that when any anoevre is demanded, each of the four nozzles in Figure 3 must be passing half its maximum flow and therefore it will be generating half its maximum thrust. Thus when a manoevre is demanded, two nozzles may have their flow increased, and two may have their flow decreased. For example, as shown in Figure 3 - Mode Required Flow Increase Flow Reduce Roll L 4, 6 3, 5 Lateral Force Y 3, 4 5, 6 Vertical Force 2 3, 6 4, 5 A conventional way of operating these nozzles would be to introduce a variable restrictor into the gas supply to each nozzle so that each one may have its flow increased or reduced as necessary. However, this requires each restrictor to be controlled accurately so that a proper balance is achieved between those with the flow increased and those with the flow reduced. If this is not done, a spurious output is obtained, for example, if lateral force was demanded, nozzles 3 and 4 should have their flows increased together. If they do not balance exactly, then a rolling moment and a vertical force will be developed, causing errors in the vehicle attitude. In addition, the sum of the flows from all the nozzles must remain constant so that the correct combustion chamber pressure is maintained. If too much flow is passed the combustion chamber pressure will drop leading to the possibility of extinction of the combustion flame. If, on the other hand, too little flow is passed the combustion chamber pressure will increase leading to higher combustion rates and ever higher chai-ber pressure with the eventual possibility of explosive structural failure. An alternative arrangement making use of diverter valves is depicted in Figure 3. This shows somewhat schematically, three diverter valves 11 which serve to control four jet nozzles. Each valve is capable of diverting its inlet flow down its two outlets in any proportion from the total amount down one side to the total down the other side and with the total flow remaining constant all the time. In order to assist understanding of the system, the diverter valve nay be considered as a spool valve as shown in Figure 5. The three diverter valves 11A, llB and IIC thus control flows to the four jet nozzles 3, 4, 5 and 6. In order to obtain a rolling moment L from the nozzles it is necessary to increase flow to nozzles 4 and 6, and reduce flow to nozzles 3 and 5. This may be achieved by actuating both valves llB and IIC to the right so they take up the positions depicted in Figure 5. Lateral thrust demand Y is obtained by actuating valve 11A to the left, increasing flow to nozzles 3 and 4, and reducing flow to nozzles 5 and 6. Vertical thrust demand Z is obtained by actuating valves 11B and IIC in opposite directions, increasing flow to nozzles 3 and 6, and reducing flow to nozzles 4 and 5. It will be appreciated that the use of diverter valves ensures constant flow at all times through the system thus keeping the combustion chamber pressure steady. It is relatively simple to maintain a balance between the nozzles having a maximum flow and those having a minimum flow because any out of balance can be removed by an adjustment in the actuation of single valve (llB or IIC). It will also be appreciated that the invention is -7- not restricted to the use of any particular type of diverter valve. Provided the valve is capable of passing a constant flow of gas an alternative type of valve might be used. Figures 6 and 7 show respectively a rotary type of diverter valve having a movable control member 12 , and a fluidic valve. In general, the gas stream produced from the combustion chamber will be extremely hot, with a temperature of the order of 2000 C C and the strean may also contain particulate matter with the combustion products. It nay not be practical therefore to use mechanical moving part valves under these cond itions. On solution to this problem is to use the fluidic diverter valve shown in Figure 7. The fluidic diverter valve is based on the well establ ished f luidic mometum interaction ampl if ier in which the gas stream at an inlet port 13 can be deflected in any proportion between the two outlet ports 14 by a low level gas pressure stream applied to either of the control ports 16. A vent 17 is provided to prevent wall attachment of the fluid stream by the Coanda effect which would lead to digital operation of the valve. The vents at the two sides of the valve are joined by a vent connecting passage 18. In conventional use, the vent would discharge to atmosphere , but in this application all gas must be -8- exhausted through the thrust-nozzles, since all exhaust gas will generate thrust and none must be lost by discharge in a non-useful direction. In order to achieve this object, the vent connecting passage 18 is provided with a further inlet opening 20 which is intended to receive the gas output from a vent of a flapper valve arrangement (about to be described) . A schematic diagram of the fluidic diverter valve is g iven in Figure 8. The control pressure signals may be generated by a simple flapper valve arrangement as shown in Figure 9. In this Figure , the valve has an inlet port 19 and two flow restrictors 21 for the incoming gas streams . The incoming gas streams are arranged to impinge equally on a flapper 22 mounted on a pivot 23. This provides control pressure outputs at output ports 24 and these control pressures may be applied to the control parts 16 of a fluid ic diverter valve. A vent enclosure 26 surrounds the flapper 22 and has a vent outlet port 27 an output from which may be applied to the vent 17 of the fluidic valve. In order to control the control gas pressures appearing at the output ports 24, the flapper 22 is βoved up or down mechanically by a suitable actuator in response to signals from the control system of the vehicle . A schematic diagram of a flapper valve arrangement -9- connected to control a fluidic diverter valve is given in Figure 10. A complete system diagram for controlling four nozzles is shown schematically in Figure 11. This would thus be suitable for controlling the gas streams emerging from the four jet nozzles 3, 4, 5, 6 by actuating the three diverter valves 11A, 11B and IIC. This would thus be suitable for the four nozzles located at the front end of the jet vehicle and a similar control system would be used for the four nozzles at the rear end of the craft. It will be noted that an advantage of the systec. shown in Figure 11 is that only three actuators are required to control the four nozzles compared with the conventional approach where four actuators would be required, one for each nozzle restrictor. The arrangement of the invention therefore not only simplifies the gas handling system making it lighter and cheaper, it also simplifies the control system. The foregoing description of an embodiment of the invention has been given by way of example only and a number, of modifications may be made without departing from the scope of the invention as defined in the appended claims. For instance, it is not essential that the control system should be applied to a vehicle having a combustion chamber relying on a solid fuel propellent material, in a different embodiment, the invention might be applied to gas streams derived from a liquid fuel propellant material.

Claims: CLAIMS s 1. A reaction jet control system for a flying vehicle, the system comprising pairs of jet reaction nozzles with associated gas flow aupply ducts, the duct between two nozzles of any one pair including a first gas diverter valve and the duct between two pairs of nozzles including a second gas diverter valve. 2. A control system as claimed in Claim 1, in which the said first gas diverter valve is a fluidic valve capable of controlling output gas flows without mechanical moving parts. 3. A control system as claimed in Claim 2, in which the said fluidic valve is a momentum interaction amplifier valve. 4. A control system as claimed in Claim 3, in which the said fluidic amplifier valve has two control ports responsive to fluid pressure inputs the said control ports being connected to a gas pressure balance valve. 5. A control system as claimed in Claim 4, in which the said gas pressure balance valve is a gas flapper valve. €. A control system as claimed in Claim 3 or Claim 4 in which the said first diverter valve and the said second diverter valve are each connected to respective gas pressure balance valves. 7. A reaction jet control system substantially as hereinbefore described with reference to any one of the accompanying drawings. c

Inventors: DAVIES GUY EDWARD, DAVIES, GUY, EDWARD
Applicants: PLESSEY OVERSEAS, PLESSEY OVERSEAS LIMITED
Application year: 1987
Main classification: B64C15
IPC codes: F02K9