A method relating to a decoy

Abstract

An untethered decoy 2 for protecting a platform 3 against radar-based threats has a first end 2A, a second end 2B and stabilising fins 23. A method of deploying the decoy 2 from the platform 3 into ai

Description

The present invention relates to a method of deploying a decoy for protecting a platform against radar based threats, and also to a round comprising said decoy. GB2516077 describes an active decoy to protect an aerial platform from radar based threats. US7520463 relates to a method for controlling deployment of a towline connecting a mooring aircraft to a towed decoy. To improve the performance of the decoy, the inventors have identified that it is desirous to stabilise the decoy into a substantially fixed attitude as quickly as possible once deployed to provide a stable platform for the decoy’s antenna. According to a first aspect of the invention there is provided a method of deploying, from a platform into air, a decoy (optionally, an untethered decoy) for protecting the platform against radar based threats; the decoy having a first end and a second, opposite, end, the decoy comprising one or more stabilising fins for stabilising the decoy, following ejection from the platform, in an orientation in which the first end faces towards the forward direction of travel of the decoy through the air; and the method comprising launching the decoy away from the platform, second end first. An expected application of the decoy is to protect aerial platforms travelling at high speeds, e.g. >300kph. The decoy can be ejected in any direction from the aerial platform but it will often be rearward, i.e. in an opposite direction to the platform’s heading. Further the speed of ejection is typically less than the forward speed of the platform. Consequently, following ejection, the decoy will be moving through the air in the same direction, i.e. with same heading, as the platform at the instance of deployment. As such, by ejecting the decoy second end first, the attitude of the decoy immediately upon its departure platform will be close to intended attitude of the decoy 05 06 25 compared with had it been ejected first end first, meaning that the time to settle into a stable orientation is reduced. When carried by the platform, the decoy may be held within a cartridge of a round, the round held within a dispenser of the platform and in which the decoy is ejected out 5 from the cartridge rear end first. The decoy is typically ejected into highly turbulent air, and therefore it is preferable that the stabilising fins have a relatively large surface area to provide sufficient stabilising force to bring the decoy into a stable attitude as quickly as possible following launch. On the other hand, the decoy needs to fit within a cartridge whose size is likely 10 to be constrained to provide compatibility with legacy dispensers. As such, it is preferred that the one or more stabilising fins are operable between a collapsed stowed configuration to enable the decoy, including the one or more fins, to fit within the cartridge, and an erect operational configuration to stabilise the decoy in the air once ejected from the cartridge. 15 For simplicity, it is preferred that each of the one or more fins are hinged to a casing of the decoy allowing rotation outwardly from the stowed configuration to the operational configuration. Nevertheless, the person skilled in the art will appreciate that other, possibly more complex, mechanisms, e.g. use of linear actuators to draw the fins linearly outwards from the casing, may be used for this purpose. 20 In a favourable arrangement, the one or more stabilising fins are situated, more favourably are hinged to the casing, about the second end of the decoy. Where so, this provides the advantage that, following ejection of the decoy, the fins will leave the cartridge first and so can rotate into the operation configuration earlier, which aids to bring the decoy into a stable attitude more quickly irrespective of the direction it is 25 ejected away from the platform. According to another aspect of the invention there is provided a round configured to be discharged into the air from a dispenser carried on a platform; the round comprising a cartridge housing an active decoy for protecting the platform against radar based 05 06 25 threats; means to hold a charge configured, when ignited, to eject the active decoy from the cartridge through a first end of the cartridge; the decoy having a front end and a rear end, the decoy comprising one or more stabilising fins for stabilising the decoy, following ejection of the decoy from the platform, in an orientation in the air which the front end faces the forward direction of travel of the decoy through the air; and in which the RF decoy is oriented within the cartridge with the rear end facing towards the first end of the cartridge. The invention will now be described by way of example with reference to the following figures in which: Figure lisa schematic cross-section of a round comprising an active decoy loaded in a dispenser of a platform; and Figure 2 is a schematic of the active decoy in operation following deployment from the platform. There is shown a round 1 comprising an active decoy 2 for protecting an aircraft 3 from radar based threats. The aircraft 3 may be a fixed or rotary wing aircraft. The round 1 is held within a chamber 4 of a dispenser 5 carried by the aircraft 3. To simplify implementation, the round 1 is sized to fit within the chamber 4 of, and be configured to be deployed from, legacy dispensers systems used for deploying traditional chaff and / or flare countermeasures. The round 1 comprises a cartridge 6 that houses, in addition to the decoy 2, an impulse cartridge 7 holding a charge 7A. A first end 6A of the cartridge 6 is provided with an end wall 6B. A second, opposite, end 6C of the cartridge 6 has an opening 6D to allow the active decoy 4 to pass out of the cartridge 6 when the impulse cartridge 3 is fired. A dispensable cover or stopper 8 closes off the open end 6D until expelled by the active decoy 2 during ejection. 05 06 25 The decoy 2 is elongate, having opposite first end 2A and a second end 2B. The decoy 2 is oriented within the cartridge 6 with first end 2A facing the end wall 6B and second end 2B facing the second end 6C of the cartridge 6. The ignition cartridge 7 sits between the decoy 2 and end wall 6B. 5 The decoy 2 comprises a casing 20 that holds electronic circuitry 21 configured to generate a decoy signal, e.g. a radio frequency decoy signal, to be transmitted through an antenna 22 to lure, jam or otherwise deceive a threat. The electronic circuitry 21 may also be configured to receive RF signals from potential threats through the antenna 22 and to generate the decoy signal based on the received RF signals. 10 The decoy 2 comprises stabilising fins 23, in this example four though this is not to be taken as limiting, to stabilise the attitude of the decoy 2 in the air following launch from the aircraft 3. The fins 23 are mounted to the casing 20 about the second end 2B, through hinges 24 so that they may rotate relative to the casing 20, outwardly from a folded stowed configuration represented in Fig 1 to enable the decoy 2 to fit into the 15 cartridge 6, to an extended deployed configuration represented in Fig 2, in which they extend laterally away from the casing 20 to stabilise the decoy 2. The decoy 2 is typically deployed whilst the aircraft 3 is in flight, travelling with a forward speed over 300 km / h. The dispenser 5 is configured to produce (or relay) a firing signal, for example, in response to an instruction from the pilot and / or an 20 electronic countermeasure system onboard the aircraft 3 that a possible threat has been detected. The firing signal is transmitted, through an electrical contact, shown schematically by line 9, extending through wall 6B, from the dispenser 5 to the round 1. The firing signal is used to ignite the charge 7A of the ignition cartridge 7 which propels the decoy 2 25 second end 2B first, in other words second end 6B leading, out of the cartridge 6, out of the dispenser chamber 4 and away from the aircraft 3. The firing signal may be transmitted from the dispenser 5 to the ignition cartridge 7 directly or, is used to initiate the electronic circuitry 21, which following initiation, produces a further firing signal to be transmitted to the ignition charge. 05 06 25 Upon launch of the decoy 2 from the chamber 4, the fins 23 rotate outwardly into the deployed configuration. This may be achieved through the use of a bias means, e.g. one or more torsion springs, that urge each fin 23 to rotate about its respective hinge 24. 5 As can be seen in Fig 2, by virtue of being ejected second end 6B first at a first speed X in a rearward direction rearwardly (arrow A) from the aircraft 3 traveling in a forward direction (arrow B) at a second speed Y, where Y>X, the ejected decoy, which is untethered to the platform, continues to move (arrow C) in the forward direction, as well as downwards, in an orientation or attitude in which the first end 6A faces towards 10 the direction of travel (C). The fins 23 act to stabilise the decoy 2 in this attitude against the destabilising forces of the turbulent airstream in the wake of the aircraft 3. The electronic circuitry 21 acts to detect RF signals from one or more threats through its antenna 22 and generates RF decoy signals S transmitted through antenna 22 to 15 deceive and / or j am the threat. The stable attitude of the decoy provides a stable platform for the antenna 22 improving the performance of the decoy 2. Although the figure implies the cartridge is cylindrical, it may be cuboid or another shape. 05 06 25

Claims

1. A method of deploying, from a platform into air, an untethered decoy for protecting the platform against radar based threats;the decoy having a first end and a second, opposite, end,5 the decoy comprising one or more stabilising fins for stabilising the decoy,following ejection from the platform, in an orientation in which the first end faces towards the forward direction of travel of the decoy through the air; andthe method comprising launching the decoy away from the platform, second end first.10 2. A method according to claim 1 wherein the platform is an aerial platform.

3. A method according to claim 1 or 2 wherein, when carried by the platform, the decoy is held within a cartridge of a round, the round held within a dispenser of the platform and in which the decoy is ejected out from the cartridge second end first.15 4. A method according to claim 3 wherein the round comprises a charge and themethod comprises igniting the charge to eject the untethered decoy from the cartridge.

5. A method according to any previous claim wherein the one or more stabilising fins lieabout the second end of the decoy.20 6. A method according to any previous claim wherein the decoy is launched awayfrom the platform in a direction lying rearward to the platform.05 06 257. A round configured to be discharged into the air from a dispenser carried on a platform; the round comprisinga cartridge housing an untethered decoy for protecting the platform against radar based threats;means to hold a charge configured, when ignited, to eject the active decoy from the cartridge through a first end of the cartridge;the decoy having a first end and an opposite, second end,the decoy comprising one or more stabilising fins for stabilising the untethered decoy, following ejection of the untethered decoy from the platform, in an orientation in the air which the first end faces the forward direction of travel of the decoy through the air;and in which the untethered decoy is oriented within the cartridge with the second end facing towards the first end of the cartridge.

8. A round according to claim 7 configured to hold the charge within the cartridge between the untethered decoy and the second end of the cartridge9. A round according to claim 7 or 8 wherein the one or more stabilising fins are located about the second end of the untethered decoy.

10. A round according to claim 7 or 8 or 9 wherein the stabilising fins are configurable to rotate between a stowed position and a deployed position.

11. A round according to any claim 7-10 comprising the charge configured, when ignited, to eject the untethered decoy from the cartridge through a first end of the cartridge.

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