GB2142419A

GB2142419A - Sub-munition for a cluster bomb

Info

Publication number: GB2142419A
Application number: GB08133131A
Authority: GB
Inventors: Geoffrey Brendan Wheaton; Donald George Merchant; John Stevenson Hunter; Michael Laurence Robinson; Jonathan Huntley Walla Shannon
Original assignee: Commonwealth of Australia
Current assignee: Commonwealth of Australia
Priority date: 1979-01-03
Filing date: 1980-01-03
Publication date: 1985-01-16
Also published as: GB2142418B; GB2142418A; AU5397179A; GB2142419B

Abstract

A sub-munition for a cluster bomb adapted to be ejected from a tube in a canister aligned with the axial direction of flight of the canister when released from an aircraft, comprises a body 34 having a tail section with sub-calibre fins 35 and an arming slug 40 axially disposed in the tail section and having a sub-calibre arming plate 39 normally positioned adjacent to the tail section but movable rearwardly by air pressure (as shown) to arm the said sub-munition during flight so as to prevent arming when a series of the said sub-munitions are held in end-to-end contact in a said tube. The arming slug is provided with a zig-zag groove 41 to oscillate a rotor to introduce a time-delay in arming. A groove 36 sustains symmetric air flow about the sub-munition body and, in like manner, a lip 37 controls the air flow about the tail section. The centre of gravity of the sub-munition is so positioned that the sub-munition does not fly stably but develops lift in a random direction. The rear edges of the fins are chamfered so as to rotate the sub-munition and assist the scattering affect. <IMAGE>

Description

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GB 2 142 419 A

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SPECIFICATION

Sub-munition for a cluster bomb

5 Background of the invention

This invention relates to a sub-munition for a cluster bomb adapted to be ejected from a tube in a canister aligned with the axial direction of flight of the canister when released from an aircraft. AO Cluster bomb units, which are generally referred to as CBU's provide a means of transporting on an aircraft large numbers of sub-munitions which can at will be dispensed from the CBU and scattered by various means so as to impact on the target over a 15 wide area.

According to this invention, a sub-munition for a cluster bomb adapted to be ejected from a tube in a canister aligned with the axial direction of flight of the canister when released from an aircraft, compris-20 es a body having a tail section with sub-calibre fins and an arming slug axially disposed in the said tail section and having a sub-calibre arming plate normally positioned adjacent to the said tail section but movable rearwardly by air pressure to arm the said 25 sub-munition during flight whereby to prevent arming when a series of the said sub-munitions are held to end-to-end contact in a said tube.

Brief description of the drawings 30 Figure 1 is a perspective view of a cluster bomb for which a sub-munition of the invention is suitable.

Figure 2 is a perspective view showing the cluster bomb after release and with the parachute deployed to slow down the bomb while the aircraft continues 35 its course until a safe distance is reached at which a propulsion charge is fired to project the forward bulkhead and, because of the retarding action of the parachute, cause sub-munitions contained therein to leave the tubes and scatter generally in the direction 40 of the trajectory.

Figure 3 is a longitudinal sectional view of the cluster bomb, but omitting the tail section.

Figure 4 is a section on line 4-4 of Figure 3 to show the arrangement of the radial petals which separate 45 the nose part from the canister which includes the tubes carrying the sub-munitions.

Figure 5 is a somewhat diagrammatic forward end elevation of the canister showing the tubes which carry the munitions.

50 Figure 6 is a side elevation to a much larger scale than Figure 1, of a sub-munition of the invention in the state when housed in a tube in the cluster bomb, the insert showing a further enlarged view of the shape of the end of the fins; and 55 Figure 7 is a perspective view of the sub-munition, but showing it as in flight with the arming mechanism pulled out by aerodynamic drag to ready the sub-munition for explosion on impact.

Referring firstly to the cluster bomb, the canister 1 60 has on it a nose 2 and a tail 3, the nose 2 being locked to the canister 1 by means of a series of radially arranged petals 4 which are shaped so that when a cylinder 5 is projected forwardly by a gas charge from a piston 6 fitted to the front bulkhead 7, the 65 detent ends 8 of the petals 4 are withdrawn from apertures in the canister 1 by pressure of the heel 9 of the petals 4 against the wall 10 of the nose 2, the petals 4 having their inner ends connected by retaining bolts 11 to a flange 12 on the cylinder 5 so that when the gas pressure on the piston 6 projects forwardly the cylinder 5 together with the front part 14 of the nose, this being permitted by flexing of a sealing diaphragm 15 connected between the wall 10 of the nose 2 and a flange 16 secured to the cylinder 5, the heel 9 acts as a fulcrum to move the detent ends 8 inwards to withdraw them from engagement with apertures in the canister 1, this action releasing the bulkhead 7 from the canister 1 and allowing the nose 2 to move forwardly from the bulkhead 7.

Continued reaction of the gas pressure on the piston 6 through the bulkhead 7 against the canister 1 forces the nose 2 away from the bulkhead 7 until the cylinder 5 reaches the end of the travel of the cylinder 5, piston 6 combination, the piston head being restrained from leaving the cylinder. At this time the piston 6 and attached bulkhead 7 are 'picked up' by the forward moving nose 2 so that the momentum acquired by the entire nose assembly causes it to separate from the canister 1, as shown in Figure 2, allowing sub-munitions to be described later, to be deployed.

An arming and detonating fuse 18 is carried in that part 14 of the nose 2 and this has arming cables 19 extending from it which are connected to the aircraft so that arming of the cluster bomb occurs after separation of the bomb from the carrying aircraft, a lead 19 passing through the canister 1 to operate the tail 3 to deploy a parachute with the required delay after release of the cluster bomb from the aircraft has occurred.

The tail 3 comprises a frame 20 attached to a rear bulkhead 21 of the canister 1 and this supports a series of fins 22 and also includes parachute petals 23 which are arranged around the frame 20 and are hinged at their rear to the rear of the frame 20 so that they can be deployed by suitable pressure means when the cluster bomb is to commence the retarding action, but between the tail petals 23 are located parachute members 24 which are also fixed to the tail petalsinsuch a manner that when the tail petals 23 open out about their rear hinges the parachute members 24 are deployed substantially as shown in Figure 2 and are held in this position by a series of cords 25 extending forward from the parachute sections and secured to the rear bulkhead 21, similar members 26 also limiting the rearward movement of the free ends of the tail petals 23 to ensure that the required drag is applied to the canister 1 after release from the aircraft. The parachute is shaped to cause the canister to rotate about its axis.

Within the canister 1 are a series of light tubes 28 which are held together by tie members 29 and are embedded in a plastic foam material 30 which fills the space between the outer surfaces of the tubes 28 and the inner surface of the wall of the canister 1 whereby to hold the tubes firmly in position within the canister 1.

Each sub-munition 34 of the invention of which one is shown more particularly in Figures 6 and 7

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comprises a body having a nose with a groove 36 circumferentially arranged just to the rear of the front end of the sub-munition, the purpose of this being to provide the correct airflow about the 5 sub-munitions after they are released from the tube.

Each sub-munition has a series of sub-calibre tail fins 35 arranged on an extension from the body 34 and arming of the sub-munition is by means of a sub-calibre plate 39 secured at the end of a movable 10 arming slug 40, the plate 39 being so proportioned that it extends into the airstream between the tail fins 35 to be pulled out by the airstream at the appropriate time, but the outward movement of the arming slug 40 is retarded by an induced oscillatory 15 motion in a time-delay device as it is pulled out, the arming slug having a zig-zag groove 41 formed in this member which engages an appropriate pin in the time-delay device. This is not shown as any standard time-delay device can be used.

20 Safety pins and other safety means are included in the sub-munition assembly, but these can take any usual or approved form and are not specifically shown herein.

The design of the sub-munitions 34 is such that 25 they fit neatly into the tubes 28 supported in the canister land when in place the rearmost sub-munition is lodged against the rear bulkhead 21 with the other sub-munitions stacked forwardly and with the most forward sub-munition loaded into position 30 by resilient bosses 46 rearwardly projecting from the forward bulkhead 7 so that when the sub-munitions are assembled in the tubes they are firmly located and are of a dimension such that they move freely in the tube, but airflow past them is restricted. To 35 ensure correct discharge of the sub-munitions the rear of the canister 1 is sealed by the bulkhead 21 so that the sub-munitions are successively released with progressive delay taking place to minimise collisions between the sub-munitions after they 40 leave the tube.

The bulkhead 21 can of course have a controlled air flow into the rear of the tubes to further regulate the rate of discharge under inertia when the canister 1 is retarded by the parachute section. 45 The operation of the cluster bomb is as follows.

The nose 2 at the forward end of the canister encloses the fuse 18 which controls the function of the CBU. When the CBU leaves the parent aircraft on the command of the pilot, the arming wires 19 50 activate it. Firstly the tail enabling assembly is activated to deploy its parachute, if so commanded. Secondly, a thermal battery is activated in the fuse 18 and a clock is started. If a third wire is pulled a full arming sequence is completed.

55 The clock causes electrically-fired gas motors or similar devices, not shown, in the tail to be connected to the battery after a preset time which allows the CBU to be clear of the aircraft. When the gas motors, or similar devices fire, the tail petals 22 are 60 released into the airstream and since they are rear-hinged they open further deploying a parachute. The parachute, in a very short time, draws the CBU behind the aircraft so that sub-munitions may be released with acceptably low risk of damage to 65 the parent aircraft should one accidentally detonate when released.

Sub-munitions are not released until a specified time has elapsed and the fuse has sensed an appropriate retardation/time history. The battery 70 then fires a detonator in the fuse 18 which has been moved from a 'safe' position to an 'armed' position by retardation forces. This detonator ignites a gas generator charge in the axial cylinder 5 to which the fuse is attached. The piston 6 in the cylinder is 75 attached to the front bulkhead 7 while the radial petals 4 have their inner ends attached to the cylinder.

As the gas in the cylinder 5 expands, the cylinder is forced forward. In doing so it moves the radial petals 80 4 which are so designed as to withdraw their ends 8 which interlocked with the canister 1. Thus, the front bulkhead 7 is no longer restrained to the canister.

When the cylinder 5 reaches the end of the travel of the cylinder 5/piston 6 combination, the piston 85 head is restrained from leaving the cylinder. Because the fuse 18 and cylinder 5 combination has by this time attained sufficient momentum in the forward direction it continues forward, taking the piston 6 and attached bulkhead 7 with it. The proportions of 90 the assembly and the gas generator charge are so chosen that the velocity of the assembly relative to the canister is sufficient to ensure that the assembly is well clear of the sub-munitions as they are released.

95 Since the sub-munitions 34 are now unrestrained in the forward direction the retardation force exerted by the open parachute 24 causes the canister 1 to be drawn away from the forward moving sub-munitions 34 and they emerge from their tubes into 100 free air.

Because at the same time as retarding the CBU the parachute 24 has been imparting spin, the sub-munitions 34 are accelerated radially on emergence from the canister.

105 Because also no air is allowed to the rear of the sub-munitions 34 as they leave their tubes 28, the air pressure behind the sub-munitions becomes less as they move down the tube 28. This has the effect of progressively separating the sub-munitions 35 longi-110 tudinally.

Both these factors have the effect of reducing the mutual interference between sub-munitions and subsequent damage on emergence. Both factors are important to the efficient operation of the CBU. 115 Once the sub-munitions 34 are released into the airstream and are separated from each other, aerodynamic drag causes the plate 39 at the rear to withdraw the arming slug 40, providing the velocity is sufficient to overcome a safety spring, not shown. 120 The arming slug 40 is keyed to the sub-munition body via the zig-zag slot 41 and to an arm'rng rotor 42 via a parallal slot 43. Withdrawal of the slug 40 thus causes the rotor to oscillate in the manner of a clutter time-delay. At the end of the clutter delay the last 125 track of the zig-zag rotates the rotor into the armed position where a detonator, lead and warhead are in line and a spring supported striker is freed. As this occurs the drag plate and slug fall away leaving the sub-munition under control of aerodynamic forces 130 generated by its shape.

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The sub-munition 34 has an aerodynamic stabilizer comprising radial fins 35 of sub-calibre span. Air-flow about the blunt nose is controlled by the shallow circumferential groove 36 which suppresses 5 the effects of minor surface irregularities thereby sustaining symmetric flow conditions about the sub-munition body. In like manner a lip 37 at the body-tail junction controls the air-flow about the finned stabilizer. With correctly chosen centre of 10 gravity position the sub-munition will not fly stably on a normal ballistic trajectory but trims at incidence and develops lift in a random direction. Spin necessary for optimum scattering performance is imparted by a chamfer 38 at the trailing edge of each 15 fin. The randomly directed lift causes the sub-munitions to scatter over an area dependent on height and velocity of the CBU at the moment of sub-munition release.

On impacting on a target the warhead is caused to 20 detonate by any known means. A pre-fragmented warhead case can be used which fractures into fragments selected in size and weight to damage aircraft or other thin structures in the near vicinity.

A cluster bomb device comprising a canister 25 having a fixed bulkhead at the rear end and a releasable bulkhead attheforward end, a nose attached to the said forward bulkhead, and a tail projecting rearward from the said rear bulkhead characterised by deployable retarding means on the 30 said tail, detent means on the said forward bulkhead engaging the said canister, means to withdraw the said detent means from engagement with the said canister, a nest of tubes within the said canister having their axes longitudinally arranged in the said 35 canister, and adapted to each hold a series of sub-munitions in an end-to-end arrangement, and means to deploy the said retarding means and to release the said detent means whereby to jettison the said forward bulkhead and the said sub-40 munitions successively due to their rate of travel relative to the said retarding canister and its tubes, forms the subject of applicants co-pending patent application No. 8000002.

Claims

45 CLAIMS arranged to project into an airstream flowing between the said fins when the said sub-munition is forwardly released from a said tube to move back the said slug to arm the said sub-munition, said 70 sub-munition having its centre of gravity so positioned that the sub-munition will not fly stably on a normal ballistic trajectory but trims at incidence to the ballistic trajectory to develop lift in a random direction. 75 4. A method of dispersing sub-munitions according to claim 1,2 or 3 from a cluster bomb wherein the sub-munitions are urged laterally by selecting the position of the centre of gravity and by choosing their shape to control airflow over them such that 80 they are positioned at an angle to the direction of flight to develop lift in a random direction. 5. The method of claim 4 wherein arming slugs on each sub-munition are held in an unarmed position by arranging the sub-munitions to fill the 85 said tubes to prevent withdrawal of the arming slugs, and arming the said sub-munitions by repositioning the said arming slugs by airflow over the said arming slugs as the sub-munitions separate on being successively ejected from the said tubes. 90 6. A sub-munition for a cluster bomb, substantially as hereinbefore described with reference to Figure 6 and 7 of the accompanying drawings. Printed in the UK for HMSO, D8818935,11/84,7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A 1AV, from which copies may be obtained.

1. A sub-munition for a cluster bomb adapted to be ejected from a tube in a canister aligned with the axial direction of flight of the canister when released

50 from an aircraft, said sub-munition comprising a body having a tail section with sub-calibre fins and an arming slug axially disposed in the said tail section and having a sub-calibre arming plate normally positioned adjacent to the said tail section but 55 movable rearwardly by air pressure to arm the said sub-munition during flight whereby to prevent arming when a series of the said sub-munitions are held in end-to-end contact in a said tube.

2. A sub-munition according to claim 1 wherein 60 the said arming slug is provided with a zig-zag deformation to oscillate a rotor to introduce a time-delay in arming.

3. A sub-munition according to claim 1 or 2 characterised in that the arming slug is extendable

65 from the rear of the said body and the arming plate is