A round comprising an active decoy

Abstract

A round 1 configured to be fired from a dispenser carried on an aerial platform, holds an active RF decoy 4 and an impulse cartridge 3 holding an explosive charge. The round 1 including an electrical

Description

GB2516077 describes an active decoy to protect an aerial platfom from radar based threats. In use, a launch tube, holding the active decoy payload, is pre-loaded with mission data before being fitted to the aircraft; this information is then transferred to volatile memory in the active decoy pay load immediately prior to ejection of the decoy from the launch tube. The present invention relates to the implementation of the afore described system. According to an aspect of tire invention there is provided a round configured to be fired from a dispenser carried on a platform, the round comprising a cartridge configured to retain an impulse cartridge holding a charge, the cartridge housing an active decoy adapted to be ejected from the cartridge through ignition of the charge; the round comprising: an electrical connector means comprising an interface external to the cartridge for interconnection with a firing contact of the dispenser, the electrical connector means adapted to receive a firing signal from the dispenser through the interconnection and carry the firing signal to the active decoy; the active decoy configured to initialise in response to receiving the firing signal, and to transmit an ignition signal to cause the impulse cartridge to fire the charge to eject the active decoy from the cartridge. Hie active decoy payload is interposed within the electrical circuit between the dispenser and the charge. This allows the active decoy to control the timing of its ejection so that it can download (or otherwise receive) mission data before being ejected. For example, part of the initialisation process may comprise the transmission of mission data to a store of the active decoy. Notably this contrasts with known passive decoys, e.g. rounds firing chaff or flares, in which there is direct electrical connection between the dispenser and the impulse cartridge. The active decoy may comprise a power store, e.g. a battery, and controller circuitry, and in which the power store is configured to be initialised in response to the active decoy receiving the firing signal to power the controller circuitry. Advantageously this enables the active decoy to remain in a dormant state or standby state, conserving power within the power store until it is desired to deploy the active decoy as a countermeasure against a threat. Another advantage of remaining in a dormant or standby state is that any RF circuitry within the active decoy may remain unpowered, minimising the possibility of the active decoy emitting undesirable RF signals prior to deployment. Another, further, advantage is it allows active countermeasures to be deployed from legacy dispensers used for firing passive countermeasures, e.g. chaff and flares, which do not provide power to the rounds other than a firing signal. The mission data may derive from a countermeasure system of the platform, comprising information obtained and / or generated during the mission; and / or it may comprise information derived prior to the mission which lias been stored on a nonvolatile store within the cartridge. The mission data may comprise parameters of threats (e.g. RF waveforms) that the decoy might encounter, and / or jamming waveforms to be used against these possible threats. Hie active decoy may comprise a volatile memory to hold the mission data. This ensures that the mission data cannot be recovered from the decoy once the decoy’s power source is depleted. The power store may comprise a thermal battery assembly comprising a thermal battery and an igniter, wherein the round is configured to transmit the firing signal to the igniter to initialise the thermal battery'. The electrical connector means may include a routing board positioned within the cartridge between the impulse cartridge and the active decoy, the routing board comprising circuitry to carry the firing signal from the interface to the active decoy and / or the ignition signal from the active decoy to the impulse cartridge. This arrangement allows the impulse cartridge to be inserted following assembly of the rest of the round, meaning the round can be kept in an intrinsically safe state until it is to be loaded into the dispenser. Tire routing board may include the non-volatile store for holding the mission data information, e.g. derived prior to the flight. The electrical connector means may include a contact, e.g. a pin connector, to contact with, and provide electrical connection with, the impulse cartridge to carry the firing signal from the routing board to the impulse cartridge. Where the routing board carries the non-volatile store, it is desirous the routing board remains on the platform, preferably within the cartridge, following ejection of the active decoy. To this end, the routing board may comprise an aperture aligned with an exhaust of the impulse cartridge so that following ignition of the charge, exhaust gases can pass through the routing board to propel the active decoy out of the cartridge. An alternative would be for the routing board to be positioned solely to one side of the exhaust though this may require a smaller board and so complicate the design of the routing board. It is also favourable that the routing board is mechanically secured to the cartridge, e.g. by means of fasteners so that it is not inadvertently ejected from the cartridge and platform when the charge is fired The cartridge may comprise, at a first end, a first aperture in which an interface plug is retained, the interface plug providing the interface external to the cartridge for interconnection with a firing contact of the dispenser. It will be appreciated than an interface element of form other than that considered a plug could be used. The cartridge may comprise, at the first end, a second aperture for retaining the impulse cartridge. There may be a recess within the cartridge in communication with the first aperture and / or second aperture and in which the interface plug and / or impulse cartridge sit when retained in the cartridge. The routing board may cany- an electrical contact that faces into the recess and by which, when one or both of the interface plug and / or impulse cartridge are absent, provides an electrical interface with a corresponding electrical connector of an external computer system that has been passed through the first or second aperture, to allow for loading of mission data from the external computer system into the non-volatile memory. The electrical contact may be separate to an electrical contact used to make connection with the impulse cartridge or interface plug. The electrical connector means may comprise a cable that extends between, and electrically interconnects, the routing board and an electrical input of the active decoy. The cable may be oriented to extend primarily about an axis that is parallel to the ejection trajectory of the decoy out from the cartridge. The electrical cable may be connected to one or both of the active decoy and the routing board, favourably at least the active decoy, through a releasably attachable connection to allow the active decoy to separate from tire routing board upon ejection of the active decoy. The cable may be retained to the active decoy primarily through an interference fit. Where the assembly comprises a piston, see below, the electrical cable favourably extends around the piston. The electrical cable may comprise a ribbon cable. The round may comprise a board mount element within the cartridge to which the routing board is mechanically fastened. The board mount element may be mechanically fastened directly to the cartridge. The board mount element may comprise one or more recesses facing the first and / or second apertures to receive the impulse cartridge and / or interface plug. The assembly may comprise a piston interposed between the active decoy and the impulse cartridge, favourably interposed between the active decoy and routing board. The piston functions to transfer kinetic energy from the fired charge to the active decoy. In doing so it acts to protect the decoy from the combustion and may also apply the force of the combustion more evenly across an end face of the active decoy reducing the likelihood of the active decoy jamming within the cartridge. The cartridge may have outer dimensions of approximately 2 inches by 1 inch by 8 inches (51mm by 25mm by 203mm). This makes the round compatible with a large number of existing dispensers configured to hold chaff and / or flare rounds. Hie active decoy may comprise circuitry for generating RF decoy signals following ejection of the active decoy from the cartridge and platform. According to another aspect of the invention there is provided a method of preparing a round to be fired from a dispenser carried on a platform, the round comprising a cartridge configured to retain an impulse cartridge holding a charge, the cartridge housing an RF active decoy adapted to be ejected from the cartridge through ignition of the charge, and a non-volatile memory; the method comprising: transmitting mission data to the non-volatile memory then mounting the impulse cartridge into the cartridge. The cartridge may comprise an aperture configured to retain the impulse cartridge, and in which the method comprises, prior to mounting the impulse cartridge in the aperture, inserting a data transfer connector through the aperture to provide a data connection with the non-volatile memory. The invention will now be described by way of example with reference to the following figures in which: Figure 1 is an exploded perspective view of a round; Figure 2 is an end view of the interface plug; Figure 3 is an end view of the impulse cartridge showing the exhaust; Figure 4 is a perspective view of the assembled round with a portion of the cartridge removed to show the active decoy; Figure 5 is a schematic diagram illustrating functional features of the circuitry of the active decoy and routing board; and Figure 6 is a schematic side view of the routing board and ribbon connector showing its laminar structure There is shown a round 1 configured to be ejected from a dispenser carried by an aerial platform, e.g. a jet aircraft. The round 1 comprises a cartridge 2 that retains: an impulse cartridge 3 holding a charge 3A (shown notionally in Fig 3); an active decoy 4; a dispenser interface plug 5; routing board assembly 6 comprising an interface board 60, ribbon connector 7 and an interface board mount 8; and a piston 9. The cartridge 2 is elongate having a first end 2A and a second end 2B. The outer dimensions of the cartridge 2 are approximately two inches by one inch by eight inches, (51mm by 25 mm by 203mm) though it will be appreciated that different dimensions may be selected to provide compatibility' with different dispensers. At the first end of the cartridge 2 there is provided an end wall 2C through which are provided a first aperture 2D and second aperture 2E. The dispenser interface plug 5 is held within the first aperture 2D. The impulse cartridge 3 is held within the second aperture 2E. Each of the interface plug 5 and impulse cartridge 3 are provided with external screw threads by which they are fastened to the cartridge 2 through corresponding threads 2F provided by the end wall 3 that face into the first and second apertures 2D 2E. The second, opposite, end 2B of the cartridge 2 is open to allow the active decoy 4 to freely pass out of the cartridge 2 when the impulse cartridge 3 is fired. A dispensable protective cover or stopper 10 closes off the open end 2B until expelled by the active decoy during ejection. The interface board 60 is mechanically fastened to the mount 8, e.g. by fasteners 11. The interface board 60 and mount 8 are located within the first end 2A of the cartridge 2 adjacent the end wall 2C, the mount 8 lying between the interface board 60 and first end face 2C. The mount 8 is mechanically fastened to the cartridge 2 by threaded fasteners 12, that extend through the end wall 2C into corresponding threaded receiving holes 80 in the mount 8. In this way the interface board 60 is also mechanically fastened to the cartridge 2. The mount 8 comprises a first recess 81 and a second recess 82, each opening towards the end wall 2C. The first recess 81 is configured to receive an inwardly protruding part 5A of the dispenser interface plug 5. The second recess 82 is configured to receive an inward end 3B of the impulse cartridge 3. Hie piston 9 and active decoy 4 are located within the cartridge 2 behind the interface board 60, as viewed from the first end 2A; the piston 9 located directly between the interface board 60 and the active decoy 4. Consequently, the piston 9 lies directly between the impulse cartridge 3 and the active decoy 4. The function of the piston 9 is to transfer energy of the combustion of the charge 3A of the impulse cartridge 3 to the active decoy 4, whilst protecting the decoy 4 from the heat generated by the combustion. The dispenser interface plug 5, interface board 60 and ribbon cable 7 provide an electrical connection to receive and convey a firing signal from the dispenser to the active decoy 4 and to convey a further firing signal from the active decoy 4 to the impulse cartridge 3 to detonate the charge 3A to eject the active decoy 4 from the cartridge 2 and away from the platform. With reference to Fig 5, the active decoy 4 comprises a casing 40 housing a thermal battery 41, including an ignition charge 41 A, for igniting the battery 41; controller 43, a volatile computer readable store 44; and radio frequency (RF) circuitry 45 for generating RF waveforms. An example of a suitable thermal battery 41 is a molten-salt battery. The active decoy 4 further comprises an antenna 46 for receiving signals from potential threats to the aerial platform and for transmitting RF decoy signals generated by the circuitry 45 from the ejected decoy 100 for the purpose, for example, of jamming or luring a threat away from the platform. When the cartridge 2 is loaded into a bay of the dispenser, the dispenser interface plug 5 provides a physical and electrical interface with the dispenser for receiving a firing signal from the dispenser to eject the active decoy 4 from the platform. The dispenser may be configured to produce a firing signal, for example, in response to an instruction from the pilot and / or an electronic countermeasure system onboard the platform. The dispenser interface plug 5 comprises, with respect to the cartridge 2, an outwardly-facing electrical contact 5B at a first end of the plug 5 for making contact with the dispenser, and an inwardly facing electrical contact 5C (see Fig 2) at the inner end 5 A of the plug 5 for contact with the interface board 60. The interface board 60 carries routing circuitry 61 and a non-volatile memory 62 for holding mission data, e.g. including parameters of threat systems that the decoy 4 might encounter and jamming waveforms 3 to be used against these possible threats. The routing circuity 61 includes an electrical connector 63, e.g. implemented by a spring-loaded electrical connector pin 63 such as a pogo pin, configured to make physical and electrical connection with the inwardly facing contact 5C of the dispenser interface plug 5 to receive the firing signal from the plug 5. With reference to Fig 6, the interface board 60 has a laminar structure comprising a layer 64 of relatively flexible dielectric material, sandwiched between two rigid layers 65, 66 of relatively rigid dielectric material. The relatively flexible layer 64 may be comprised from polyamide. The relatively rigid layers 65 and 66 may be comprised of epoxy resin. Tire ribbon cable 7 is provided by an elongate portion of the relatively flexible layer 64 carrying conductive tracks that extends laterally beyond the rigid layers 65, 66. Through this configuration, the ribbon cable 7 extends from an edge of the routing board 60, around the side of the piston 9 to make connection with an electrical connector 4A of the active decoy provided on a side 4B of the decoy that faces perpendicular to the line of travel of the decoy 4 as it is ejected out of the cartridge 2. The ribbon cable 7 is physically retained to the electrical connector 4A solely by an interference fit (though it could additionally or alternatively be held by a weak adhesive or releasable bond adhesive), such that when the charge 3 is ignited, the electrical connector 4A readily separates from the ribbon cable 7 as the active decoy 3 is propelled out of the cartridge 2. When assembled, the interface board 60 lies directly between the impulse cartridge 3 and the active decoy 4. The interface board 60 defines a through aperture 60A that is aligned with an exhaust 3B (see Fig 3) of the impulse charge 3. This provides a path through the interface board 60 to the piston 9 for propellent gases generated by combustion of the charge 3A. This ensures the majority of the force of the propellent gases is conveyed against the piston 9 and hence also the active decoy 4, rather than the interface board 60. The routing board 60 includes a further contact 67, illustrated notionally in Fig 5, provided on a side of the routing board that faces into the second recess 82. Before the impulse cartridge is installed, a data connector plug (not shown) of an external computer system may be inserted through the second aperture 2E to contact the further contact 67 to provide a data connection between the routing board 60 and external computer system by which mission data can be transmitted from the external computer system to the non-volatile memory prior to the round 1 being loaded into the dispenser. In use, a firing signal from the dispenser, received through the interface plug 5 is conveyed through the routing circuitry 61 and via the ribbon connector 7, to the ignitor 41A of the battery 41. The firing signal causes the ignitor charge to detonate, igniting the battery 41 that powers the circuitry of the decoy including the controller 43. Following initialisation, the controller 43 transfers a copy of mission data held on the non-volatile store 62 carried on the interface board 60 into the volatile memory 44. Once the mission data has been copied, the controller 43 generates an ignition signal, of similar characteristics to the firing signal, i.e. of sufficient power to ignite charge 3A, which is routed back to the interface board 60 via the ribbon cable and routing board 60 to the input of the impulse cartridge 3. The charge 3 A ignites generating propellent gases that pass out through exhaust 3B, through the aperture 60A within the interface board 60 and against the piston 9 urging the piston 9 against the active decoy 4 to eject the active decoy 4 out from the second end 2B of the cartridge 2. Upon ejection, the RF circuitry 45 acts to detect RF signals from one or more threats through its antenna 46 and generates, using the mission data in store 44, RF decoy signals which are transmitted via antenna 46 to deceive and / or jam the threat. In a variant, the routing board may not be located directly between the active decoy 4 and charge. Rather it could be positioned to one side between the two, or alongside the impulse cartridge. A cable of form other than a ribbon cable could be used connect the active decoy and the routing board. In the absence of a piston, the routing board may be in direct physical contact with the active decoy. Where so, an electrical connection may be provided therebetween by electrical contacts provided on their respective contacting faces, obviating need of a cable. The ignition signal produced by the active decoy 4 may not have sufficient power to ignite the charge 3A, in which case it may be used to prompt a signal generator carried on the routing board 60, to generate an ignition signal to ignite charge 3A. Although the invention was conceived for use with radio frequency active decoys, it could also be applicable to active decoys adapted to transmit and receive other electromagnetic frequencies, such as within the infrared. In a variant, the interface board 60 may carry a controller configured to transfer the mission data held on the non-volatile store 62 carried on the interface board 60 into the volatile memory 44 of the decoy. Rather than transferring the mission data held by the round onto the decoy, the round may include processing circuitry, e.g. held on the interface board, configured to process mission data to produce derivate data, which is transferred to the decoy, and used by the decoy to generate the required RF decoy signal. For die purpose of the this application this derivate data may also be considered as mission data.

Claims

1. A round configured to be fired from a dispenser carried on a platform, the round comprising a cartridge configured to retain an impulse cartridge holding a charge, the cartridge housing an active decoy adapted to be ejected from the cartridge through ignition of the charge; the round comprising:an electrical connector means comprising an interface external to the cartridge for interconnection with a firing contact of the dispenser, the electrical connector means adapted to receive a firing signal from the dispenser through the interconnection and carry the firing signal to the active decoy;the active decoy configured to initialise in response to receiving the firing signal, and to transmit an ignition signal to cause the impulse cartridge to fire the charge to eject the active decoy from the cartridge.

2. A round according to claim 1 wherein the active decoy comprises a volatile store to hold mission data; during initialisation, the round assembly is configured to transmit mission data to the volatile store, and the active decoy is configured to transmit the ignition signal after the mission data is stored within the volatile store.

3. A round according to claim 2 wherein the cartridge houses a non-volatile store external to the active decoy to hold mission data; and the round is configured to transmit mission data from the non-volatile store to the volatile store after the active decoy has received the firing signal and before the active decoy has transmitted the ignition signal.

4. A round according to any previous claim wherein the active decoy comprises a power store and controller crrcuitn . and in which the power store is configured to be initialised m response to the active decoy receiving the firing signal.

5. A round according to claim 4 wherein the power store comprises a thermal battery which includes an ignitor charge, wherein the round is configured to transmit the firing signal to the ignitor charge, detonating the ignitor charge to initialise the battery.

6. A round according to any previous claim wherein the electrical connector means includes a routing board that lies within the cartridge between the impulse cartridge and the active decoy; the routing board comprising circuitry to cany the firing signal from the interface to the active decoy and / or the ignition signal from the active decoy to the impulse cartridge.

7. A round according to claim 6 wherein the routing board defines an aperture aligned with an exhaust of the impulse cartridge when retained by the cartridge, so that exhaust gases from firing of the charge pass through the aperture to eject the active decoy.

8. A round according to claim 6 or 7 wherein the routing boarding carries the nonvolatile store to hold mission data.

9. A round according to any claim 6-8 wherein the routing board comprises an electrical contact to make connection with the impulse cartridge.

10. A round according to any previous claim wherein the electrical connector means comprises a cable that extends between, and electrically interconnects, the routing board and an electrical input of the active decoy, wherein the electrical cable is connected to one or both of the active decoy and the routing board through a releasably attachable connection to allow the active decoy to physically separate from the routing board upon ejection of the active decoy.

11. A round according to claim 10 wherein the cable is retained to the active decoy primarily through an interference fit.

12. A round according to any claim 8-11 wherein the routing board comprises a flex-rigid board comprising a relatively flexible dielectric layer sandwiched between two relatively rigid dielectric lay ers, and in which the relative flexible layer comprises an elongate portion that extend laterally beyond the relative rigid layers and which carries conductive tracks to provide a flexi-cable that connects the routing circuitry to the active decoy.

13. A round according to claim 12 wherein the flexi-cable is orientated to extend primarily in an axis parallel to the ejection path of the active decoy out of the cartridge.

14. A round according to any previous claim in which the cartridge houses a piston.

15. A round according to claim 13 and 14 in which the flexi-cable extends aroundthe piston.

16. A round according to any previous claim wherein an end face of the cartridge defines therethrough a first aperture at a first end for retaining the impulse cartridge.

17. A round according to any previous claim wherein an end face of the cartridge defines therethrough a second aperture for retaining an interface plug that provides an interface external to the cartridge for interconnection with a firing contact of the dispenser.

18. A round according to any previous claim wherein the electrical connector means is adapted to carry the ignition signal to the impulse cartridge to fire the charge to eject the active decoy.

19. The round of any previous claim comprising the impulse cartridge.

20. A method of preparing a round to be fired from a dispenser carried on a platform;the round comprising: a cartridge configured to retain an impulse cartridge holding a charge, the cartridge housing an RF active decoy adapted to be ejected from the cartridge through ignition of the charge; and a non-volatile memory;the method comprising:transmitting mission data to the non-volatile memory' then mounting the impulse cartridge into the cartridge.

21. A method according to claim 20 wherein the cartridge comprises an aperture configured to retain the impulse cartridge, and in which the method comprises, prior to10mounting the impulse cartridge in the aperture, inserting a data transfer connector through the aperture to provide a data connection with the non-volatile memory.16

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