GB2156290A

GB2156290A - Rockets and rocket motors

Info

Publication number: GB2156290A
Application number: GB08506956A
Authority: GB
Inventors: Daniel Henry Stirling Everard
Original assignee: EVERAIDS Ltd
Current assignee: EVERAIDS Ltd
Priority date: 1984-03-27
Filing date: 1985-03-18
Publication date: 1985-10-09
Also published as: GB8506956D0; GB2156290B

Abstract

It is known to use solid propellent motors to provide propulsion for rockets, these motors requiring a constant combustion rate of the propellant. The invention permits a constant combustion rate of the propellant while providing control of the rocket in the pitch, yaw and roll planes. This is achieved by pulsing the thruster nozzles 6, 7, 8, 9 which allow the gas to exit from the rocket combustion chamber 5, so that a constant number of nozzles, preferably only one, is or are open at any one time thereby providing a constant gas flow out of the chamber. The nozzles described herein may comprise servo-operated on/off plug valves and may be mounted inside the motor combustion chamber. While a solenoid operated ball valve 19 closes a port 18, combustion chamber pressure acts in cylinder 10 on the rear of valve member 11 to close the nozzle. Opening ball valve 19 allows pressure in the cylinder 10 to be relieved through port 18 so that the valve member 11 moves inwards to open the nozzle to the combustion chamber. <IMAGE>

Description

SPECIFICATION Rockets and rocket motors This invention relates to solid propellant rockets and rocket motors.

According to one aspect of the invention, there is provided a rocket having a solid propellant motor the combustion chamber of which communicates via respective on-off valves with four fixed efflux nozzles, the rocket further comprising valve control means for opening and closing the valves during the flight of the rocket to produce thrust impulses from the respective nozzles which, summed over a period of time, constitute an overall rocket control force vector for that period while the number of valves open at any one time remains constant, each of the nozzles being directed to produce thrust comprising a radial component and two of the nozzles being positioned at respective opposite sides of and equispaced from the pitch plane of the rocket so that impulses from these two nozzles provide yaw control components of said vector while the other two nozzles are positioned both at the same side of the yaw plane and at one and the other side respectively of the pitch plane of the rocket so that impulses from these two nozzles provides roll control components and pitch control components of said vector.

According to a second aspect of the invention, there is provided a solid propellant rocket motor comprising a combustion chamber, a thruster nozzle the inlet of which is connected to the chamber, and an on-off plug valve which is at the combustion chamber side of said thruster nozzle inlet and which includes a valve member and actuator means for moving the valve member into and out of engagement with said inlet to control the flow of gas through the nozzle.

Advantageously, said thruster nozzle is attached to the wall of the combustion chamber and said valve is entirely mounted inside the combustion chamber. The valve may comprise a pressure chamber, in which said valve member is mounted for linear movement in response to a difference in pressure between the inside and outside of the chamber, the chamber communicating with the interior of said combustion chamber and, via a solenoid-controlled on-off servo-valve, with the exterior of the combustion chamber and the arrangement being such that, when said servo-valve is off, the pressure within the pressure chamber increases towards that of the combustion chamber and urged by this pressure, said valve member then moves into engagement with said nozzle inlet while, when said servo-valve is on, the pressure within the pressure chamber is released and then the valve member moves out of engagement with the nozzle inlet.

According to a third aspect of the invention, there is provided a thrust control valve operable to direct a gas supply to provide thrust including a housing having nozzle means rigidly attached to it at one end, control means mounted within said housing, a pressure chamber having a gas inlet port and a gas outlet port also mounted within the housing, and a gas supply, the pressure chamber containing plunger means, the control means being operable to close off said outlet port when in a first position and to open said outlet port when in a second position, the plunger means being operable to come into sealing engagement with said nozzle means when said outlet port is closed and to direct said gas supply through said nozzle means when said outlet port is open, due to a pressure difference across it.

For a better understanding of the invention reference will now be made by way of example to the accompanying drawings in which: Figure 1 is a sectioned side view of a rocket; Figure 2 is a view from the rear of a motor used in the figure 1 rocket; and Figures 3 and - each comprise a sectional elevation of a control valve used in the figure 2 motor, the two figures showing the valve in its closed and open positions respectively.

The illustrated rocket consists of a body 1 which contains a motor 2. The motor 2 comprises a combustion chamber 4 which is partly filled with solid propellant 3. The rear of the combustion chamber 4 is define by an end cap, to which there are attached four thruster nozzlelvalve assemblies comprising nozzles 6, 7, 8 and 9. The valve in each nozzle/valve assembly is electrically controlled and when the valve is open, gas can exit from the combustion chamber 4 through the associated nozzle to provide thrust on the rocket. The valves in the respective nozzle/valve assemblies are operated in sequence to produce pulses of thrust from the associated nozzles, there being always one, but only one nozzle which is producing thrust at any one time. This ensures that the gas flow from chamber 4 and hence the pressure therein remain constant.

The nozzles point outwards so that the thrust each nozzle produces can be resolved into two perpendicular components, one of these components acting along the rocket axis to provide forward propulsion of the rocket, and the other component acts in a direction extending radially outward from the rocket axis to provide control of the rocket in the pitch, yaw and roll planes.

Each nozzle produces a similar axial thrust component so that, even though the nozzles are beng operated one at a time, the forward thrust remains substantially constant. Meanwhile, the overall radial thrust component over a given time period comprises the sum of the individual radial thrust components produced by the respective nozzles which have been operated during that time. Thus, radial control of the rocket, i.e. yaw, pitch and roll control, can be obtained by appropriately controlling which of the nozzles are operated, the sequence in which they are operated, and the respective times for which they are operated so as to give the appropriate overall radial thrust component.

The radial components of thrust produced by nozzles 6 and 7 act to move the rocket in the yaw plane i.e. to the right or left respectively. In order to obtain no net movement in the yaw plane, noz zles 6 and 7 have to be operated alternately for equal lengths of time, the radial components of thrust cancelling each other out when summed.

Nozzles 8 and 9 produce radial components of thrust which act downwards providing upward movement of the rocket and therefore control in the pitch plane. Downward movement of the rocket is provided by gravity. Roll control can be obtained together with upward pitch control by altering the times for which nozzles 8 and 9 operate so that a net radial component of thrust is produced which does not pass through the rocket axis thereby giving roll movement as well as an upward movement to the rocket.

Other nozzle arrangements are possible depending on the degree of control required in the pitch, yaw and roll planes.

As shown best in Figures 3 and 4, the valve of each nozzle/valve assembly is positioned within the combustion chamber of the rocket while the nozzle of the assembly projects through the motor end cap 5.

The valve consists of a housing 14 defining a cylinder 20, one end of which engages the inlet aperture 12 of the nozzle and which contains a plugvalve member 11. The valve member 11 has a conical sealing surface 21 at one end, the end nearer the aperture 12, and has a diameter which for about half the length of the member extending back from the surface 21 is slightly less than the internal diameter of the cylinder 20. The remaining part of the member 11, apart from a groove 23 containing a flexible sealing ring 24, is a sliding fit within the cylinder 20.The member 11 is able to move within the cylinder 20 between a Qnozzleclosed' position shown in Figure 3, in which position the surface 21 closes the aperture 12, and a Qnozzle-open' position shown in Figure 4, in which position the surface 21 is away from the aperture 12 so that gas can exit from the combustion chamber through duct 25 leading to the aperture 12. Between the other end of the valve member 11 and a wall 22 closing the other end of the cylinder 20 there is defined a pressure chamber 10.

A hole 18 in the cylinder end wall 22, which hole can be closed by a valve-member 19 forming part of a solenoid-operated servo-valve 13, provides communication via a duct 16 between the pressure chamber 10 and the exterior of the combustion chamber. Meanwhile, a small metering orifice 17 leads from the chamber 10 to a duct 15 which in turn leads to the interior of the combustion chamber.

To the close valve as shown in Figure 3, the solenoid of the servo-valve 13 is energised so as to maintain the valve member 19 in sealing engagement with the hole 18. Hence, due to the communication between the chamber 10 and the combustion chamber via duct 15 and orifice 17, pressure builds up in the pressure chamber 10 and at first forces the valve-member 11 into engagement with the nozzle inlet 12, and then maintains it in this position. When the solenoid 13 is de-energised, the valve-member 19 is pushed away from the hole 18 by the pressure within chamber 10.

This allows the gas collected in the pressure chamber 10 to vent to the atmosphere along duct 16. As the pressure in the pressure chamber 10 decreases, the valve member 11 is forced out of engagement with the nozzle aperture 12 by the pressure within the combustion chamber acting upon the periphery of surface 21 and the boundary between the narrow and wider diameter parts of the member 11. Gas from the combustion chamber is now able to exhaust through the nozzle to provide the required thrust. Some of the exhaust gas from the combustion chamber still flows into the pressure chamber 10 via orifice 17 but is able to leak away via hole 18, the relative sizes of the hole 18 and orifice 17 being chosen to ensure that the pressure within chamber 10 at this time remains less than that in the combustion chamber. When the solenoid 13 is energised, the hole 18 is closed so allowing the pressure inside chamber 10 to build up and force valve member 11 against the nozzle inlet 12 as described earlier.

By mounting the valve in the combustion chamber, a faster operation time can be achieved as only a relatively small volume of gas has to be removed from the pressure chamber 10 before the valve will operate. Naturally, it is possible to mount the valve/nozzle assembly external to the combustion chamber.

The valve housing 14 and valve member 11 are made of high temperature resistant material for example the valve member could comprise titanium alloy with a tip, defining surface 21, made of molybdenum alloy. The housing and nozzle, and perhaps also the valve member, could comprise ceramic material.

Claims

1. A rocket having a solid propellant motor the combustion chamber of which communicates via respective on-off valves with four fixed efflux nozzles, the rocket further comprising valve control means for opening and closing the valves during the flight of the rocket to produce thrust impulses form the respective nozzles which, summed over a period of time, constitute an overall rocket control force vector for that period while the number of valves open at any one time remains constant, each of the nozzles being directed to produce thrust comprising a radial component and two of the nozzles being positioned at respective opposite sides of and equispaced from the pitch plane of the rocket so that impulses from these two nozzles provide yaw control components of said vector while the other tow nozzles are positioned both at the same side of the yaw plane and at one and the other side respectively of the pitch plane of the rocket so that impulses from these two nozzles provide roll control components and pitch control components of said vector.

2. A solid propellant rocket motor comprising a combustion chamber, a thruster nozzle the inlet of which is connected to the chamber, and an on-off plug valve which is at the combustion chamber side of said thruster nozzle inlet and which in cludes a valve member and actuator means for moving the valve member into and out of engagement with said inlet to control the flow of gas through the nozzle.

3. A solid propellant rocket motor according to claim 2, wherein said thruster nozzle is attached to the wall of the combustion chamber and said valve is entirely mounted inside the combustion chamber.

4. A solid propellant rocket motor according to claim 2 or 3, wherein the valve comprises a pressure chamber, in which said valve member is mounted for linear movement in response to a difference in pressure between the inside and outside of the chamber.

5. A solid propellant rocket motor according to claim 4, wherein the chamber communicates with the interior of said combustion chamber and, via a solenoid-controlled on-off servo-valve, with the exterior of the combustion chamber and the arrangement being such that, when said servo-valve is off, the pressure within the pressure chamber increases towards that of the combustion chamber and urged by this pressure, said valve member then moves into engagement with said nozzle inlet while, when said servo-valve is on, the pressure within the pressure chamber is released and then the valve member moves out of engagement with the nozzle inlet.

6. A thrust control valve operable to direct a gas supply to provide thrust including a housing having nozzle means rigidly attached to it at one end, control means mounted within said housing, a pressure chamber having a gas inlet port and a gas outlet port also mounted within the housing, and a gas supply, the pressure chamber containing plunger means, the control means being operable to close off said outlet port when in a first position and to open said outlet port when in a second position, the plunger means being operable to come into sealing engagement with said nozzle means when said outlet port is closed and to direct said gas supply through said nozzle means when said outlet port is open, due to a pressure difference across it.

7. A solid propellant rocket motor substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.