GB2277980A - Gun launchable shell and fuse - Google Patents

Abstract

A shell (3) comprises a hydrostatic fuse (4) which allows the shell to function as a depth charge. The fuse may operate in response to pressure or after a predetermined time lapse from water entry. Conventional impact or proximity fuses may be additionally incorporated, acting in conjunction with, or as a selectable alternative to, the hydrostatic fuse. This allows the shell to be deployed against both surface and submarine targets. The fuse may be used in conjunction with a conventional shell or with a shell whose explosive charge is optimised for underwater performance. <IMAGE>

Description

GUN LAUNCHABLE SHELL AND FUSE This invention relates to a gun-launchable explosive shell arranged to detonate underwater and a fuse for use with such a shell.

Submarines are very difficult to detect, and therefore pose a serious military threat. In particular they are able, in some circumstances, to attack a surface ship with torpedoes or missiles before the ship is aware of the submarine's presence.

Because of this and other threats posed by submarines, considerable resources are deployed in anti-submarine warfare (ASW). Forces used to hunt submarines include ships, aircraft and other submarines. In many cases, a surface ship force will include an ASW force to protect or screen the surface ships from attack by submarines.

In some situations the ASW force may have considerable difficulty in detecting and classifying a submarine. In particular, when using active sonar in shallow or confined water, a large number of false sonar contacts, which may come from wrecks, rocks or other non-submarine sources, may be obtained by the ASW force. It may be difficult to distinguish such contacts from a real submarine, particularly a submarine which is moving slowly or is stationary. Many such potential contacts may be obtained during the course of a day, and each one indicates a potential threat to the ASW force or to surface ships which it is protecting. It can take a long time to classify each individual contact with a high degree of probability, and in many situations there is not sufficient time to do this.The ASW force then has to attack each potential contact with a homing torpedo, in order to protect the surface force. If there are many such false contacts, the stock of homing torpedoes may be quickly used up. Furthermore, the cost of homing torpedoes is relatively high. If, on the other hand, the ASW force decides to use its torpedoes sparingly and not attack all of the possible contacts, then any one of them may be a real submarine which subsequently launches an attack on the surface force. A helicopter or aircraft may not always be available to launch homing torpedoes on the suspected target, in which case an ASW ship can make fewer attacks since it needs to get closer to each contact in order to attack.

The ASW force may decide to attack a potential submarine contact with depth charges, but there are factors which limit the usefulness of such devices in this situation.

It has been proposed to equip an ASW force with mortar devices that can be used to project depth charges towards the submarine.

However such devices have a number of disadvantages. They are relatively bulky and consume a relatively large amount of deck space. Also they do not achieve a very long delivery range and are relatively inaccurate.

A submarine or other threat such as mini submarines, divers, or chariots may penetrate close in to coastal areas, harbours or channels where it may pose a serious threat through the use of mines, torpedoes or missiles or through intelligence data gathering. The defending ASW force may find it difficult to atack such a submarine or the like because in very shallow waters the sonar conditions may be difficult and render homing torpedoes ineffective. If the submarine is on or close to the sea bed and slow or stationary it becomes particularly difficult to attack.

Incursions into coastal water may occur in peacetime when, for political reasons, the defending ASW force may wish to provoke the submarine, or force it to surface, or make it go away without actually causing sinking damage.

In accordance with the invention, a gun-launchable shell comprises bathometric fuse means.

In the present specification, the term "bathometric fuse" refers to a fuse which is arranged to provide detonation below the surface of the sea or other body of water.

Such a shell may operate in the manner of a depth charge. Unlike conventional depth changes it may be deployed by a standard naval gun over a much wider range than a conventional depth charge and with much higher accuracy.

The fuse means may comprise a hydrostatic fuse. This ensures that the shell will explode at a predetermined depth under the sea as determined by pressure due to the head of water above the fuse.

The fuse means may comprise a time delay fuse arranged to detonate a predetermined time after the shell has entered the water. This may be provided as an alternative to or as an addition to the hydrostatic fuse.

The shell may comprise proximity fuse means.

The shell may comprise impact fuse means. These additional fuse means allow the shell to function as a conventional shell thereby increasing its versatility.

The shell may comprise means to inhibit operation of the impact fuse means until after the shell has entered the water. This allows the shell to detonate if it comes into contact with a sub-surface solid body which it encounters after its initial inpact with the surface of the sea.

The shell may comprise pre-selection means arranged to select the mode of operation of the shell prior to filing. In this particularly advantageous arrangement, the shell is provided with a number of different types of fuse means. One or more of these fuse means is selected prior to firing the shell, the others being inhibited. Thus, for example, a single shell may be capable of operating as a conventional shell or as a depth charge according to which fuse means is enabled. When used as a depth charge, detonation may, for example, be selected in response to one or more of depth, elapsed time from impact, proximity etc.

Preferably the pre-selection means is arranged to co-operate with pre-selecting means, the pre-selecting means being arranged to apply, to a shell presented thereto, all stimuli necessary to ensure that the selected mode or modes of operation are enabled.

Preferably the pre-selecting means is incorporated into the gun from which the shell is to be fired. This allows the gun to be loaded with a round before the precise nature of the target has been ascertained. Once the nature of the target has been ascertained, the appropriate fuse means can be selected and the gun fired without delay.

The invention will now be described by way of non-limiting example only with reference to the drawings in which: Figure 1 shows a first embodiment of the invention; Figure 2 shows a second embodiment of the invention; Figure 3 shows a flow diagram illustrating stages in deployment of embodiments of the invention; Figure 4 illustrates way of utilising the invention; Figure 5 illustrates another way of utilising the invention; and Figure 6 illustrates yet another way of utilising the invention.

Referring to Figures 1 and 2, a shell has a body 1 containing explosive 2. The conventional cartridge case and propellant have been omitted for clarity. The shell has a fuse 3 having a bathometric sensor 4 comprising a hydrostatic pressure sensor 5 arranged to operate at a predetermined pressure. The operating pressure can be preset prior to firing according to the depth at which detonation is to take place. The fuse 3 has a safety and arming arrangement 6 which ensures that the shell only becomes armed after it has been fired. The safety and arming mechanism may comprise any of the conventional arrangements known to those skilled in the art, for example centrifugally-operated detents or switches. It may be arranged to arm the shell only after the shell has travelled a safe distance from its point of firing.

In the present embodiment, the safety and arming mechanism also includes a further arrangement triggered by impact of the shell with the water whose operation will be described later. The fuse has a screw threaded portion 7 by which it is coupled to the shell body 1. Preferably this is dimensionally compatible with a standard screw threaded coupling used for conventional fuses. The fuse 3 has a detonator 8 which is triggerable by the hydrostatic sensor 5 and which causes detonation of the explosive charge 2.

A sequence of operation of the shell will now be described with reference to figures 3 and 4. A ship 41 suspects the presence of a submarine 43 close to the seabed 42. A shell in accordance with the invention is fired from the ship's gun 45.

At a point 32 on its trajectory 46, a first arming mechanism 31 comprising a centrifugal detent operates. The first arming mechanism is responsive to the spin induced in the shell by firing. At this point in the operating sequence the shell is not yet armed. At a second point 34 in the trajectory a second arming mechanism 33 comprising a drag force sensor operates.

At point 36, the shell makes impact with the surface 40 of the sea. In the present embodiment, the impact causes a third arming mechanism 35 to operate.

In the present embodiment, the third arming mechanism enables the hydrostatic sensor 5. When the shell has sunk to a depth sufficient to trigger the hydrostatic fuse 5, it supplies a fire signal 37 to the detonator 8, thereby detonating the shell and causing an underwater explosion 47. This completes the deployment sequence.

The deployment sequence described above is given by way of example only, and different sequences, such as the omission of, or the addition of, arming stages may be provided according to operational requirements. For example, the third arming stage and its associates mechanism may be omitted, the hydrostatic sensor being enabled by the second arming mechanism 33.

In underwater explosions, damage is primarily inflicted by blast. The magnitude of blast produced, will, other things being equal, be a function of the size of the shell. While the force of the explosion produced by, for example, a conventional explosive charge carried by a 41/2 inch calibre shell may be insufficient to cause much damage to a conventional submarine, it can be extremely effective against midget sumbarines or unprotected divers. Moreover, the high rate of fire of current guns allows a large number of shells to be deployed in a short time, and the accumulative blast may be capable of inflicting significant damage.

Further, underwater explosions may cause a submarine to take evasive action, thereby causing it to reveal its presence, which presence may only have been suspected. Once its presence has been postively ascertained, heavier conventional depth charges or other suitable weapons may be brought into play.

In a further embodiment of the invention, not shown, a shell is provided with an explosive charge tailored to produce a blast which inflicts the maximum damage on its target. This damage is not necessarily damage to the main structure of an underwater vessel. By producing a suitable profile of shock wave with respect to time it may be possible to cause failure of seals and gaskets which would resist a conventional underwater explosion.

For example, the explosive charge may be such as to maximise the volume of gas produced, and to produce this volume of gas in a very short time. This will give rise to a sharp pressure wave which is capable of causing certain synthetic rubber or polymer seals to fail by brittle fracture. The leaks resulting from such seal failure may lead to operational difficulties in a submarine and functional failure of a torpedo.

The invention may also be used in a defensive role against torpedo attack. In Figure 5, a ship 41 is shown laying a pattern of underwater explosions 47 in the path of an attacking homing torpedo 50. The rapid fire rate of a naval gun allow a spread of underwater explosions to be laid accurately in a very short time each underwater explosion 47 produces a large number of bubbles in the water. While the larger bubbles soon rise to the surface, the smaller bubbles may persist for an appreciable length of time. These bubbles can produce false echoes while they exist, and generate noise when they collapse. Thus the bubbles can confuse the automatic homing mechanism of an attacking torpedo.

Of course, if the shell explodes sufficiently close to the torpedo, the blast may cause sufficient damage to render it ineffective. For example, its sensors may malfunction, or it may spring a leak.

In any of the above described scenarios, the ship's sonar detectors may be utilised to detect the bubbles as a means of checking the accuracy of firing. This may be done with reference to absolute position, or else the position of the bubbles can be compared with the target position if this is known.

The invention is not limited to the exemplary arrangement described above and a number of modifications are possible within the scope of the invention.

In one modification, not shown, the hydrostatic fuse is replaced by a timer arranged to time out a predetermined time after impact with the surface of the sea.

This can be as effective as a hydrostatic fuse where the rate of descent of the shell is known, and is advantageous for deployment in shallow water or where the depth of the water is unknown. It also reduces the chance of leaving live shells on the sea bed in an armed state.

In another modification, not shown, the hydrostatic fuse is supplemented by a timer. This can function as a back-up to the hydrostatic fuse.

In a further modification, not shown, the fuse incorporates an impact fuse. This allows the shell to explode immediately on coming into contact with an undersea object if such contact occurs before the predetermined depth is reached. In another modification, not shown, the fuse includes a proximity sensor. This allows the fuse to detonate if it approaches within a predetermined distance of an undersea object before the predetermined depth is reached.

In another modification, not shown, the fuse includes conventional impact and/or proximity sensors for use on surface targets. This allows the same type of shell to be used against surface or subterranean targets at will, the appropriate sensor or sensors being enabled prior to firing according to the target.

In another modification, not shown, the shell comprises preselection means to allow the mode of operation of the shell to be selected prior to firing. The shell is fitted with two or more different types of fuse, and one or more of these fuses is enabled prior to firing. The fuse or fuses appropriate to the target is or are enabled before the shell is loaded into the gun.

In another modification, not shown, the fuse comprises preselection means for allowing the appropriate sensor or sensors to be selected after the shell has been loaded into the gun from which it is to be fired. In this case, the gun incorporates preselecting means arranged to co-operate with the preselection means of the shell.

This allows a round to be loaded into a suitably equipped gun, ready for firing, before the nature of the target is known.

The above described arrangements are given by way of example only, and arrangements in accordance with the invention can utilise any suitable fuse known to those skilled in the art according to the nature of a particular target against which the shell may need to be employed.

The shell body and its explosive charge may comprise a conventional shell to which a fuse in accordance with the invention is fitted. In another modification, not shown the shell body and explosive charge are designed for optimum underwater performance. For example, the charge may be designed to release a cloud of a substance which produces a strong echo as well as or instead of producing an explosion. Alternatively the charge may be designed to maximise the underwater explosive performance.

Embodiments of the invention having multipurpose capability and which can be preselected before firing are especially advantageous in that they can reduce or eliminate the requirement for a ship to carry a large stock of different shells, each dedicated to a particular duty.

Furthermore, although the embodiment has been described in the context of a ship-borne gun, it may equally well be utilised by shore-based guns.

In Figure 6 a land based gun 60 is shown deploying a shell in accordance with the invention against a hostile intruder 61. The gun 60 is of large calibre and the shell contains an explosive charge comparable to that carried by a conventional depth charge. By utilising such a shell the conventional land based gun is thereby able to deal with the hostile intruder without auxilliary assistance.

The application of the invention to large calibre shells suitable for use by shorebased guns is especially advantageous in the defence of coastal water, river estuaries, fiords etc, allowing countermeasures to be rapidly taken against suspected hostile underwater craft without the need to summon a ship or helicopter which would otherwise be needed to deploy conventional depth charges.

Although a large calibre gun is advantageous, in terms of size of payload, the invention may be usefully employed with lesser calibre guns. The gun need not be one deployed in a fixed shore battery but may be a mobile gun or howitzer.

Claims (22)

1. A gun-launchable shell comprising bathometric fuse means.

2. A shell as claimed in Claim 1 in which the fuse means comprises a hydrostatic fuse.

3. A shell as claimed in Claim 1 or 2 in which the fuse means comprises a time delay fuse arranged to detonate a predetermined time after the shell has entered the water.

4. A shell as claimed in any preceding claim comprising proximity fuse means.

5. A shell as claimed in any preceding claim comprising impact fuse means.

6. A shell as claimed in Claim 5 comprising means to inhibit operation of the impact fuse means until after the shell has entered the water.

7. A shell as claimed in any preceding claim comprising an explosive charge adapted for the production of an underwater explosion.

8. A shell as claimed in Claim 7 in which the underwater explosion is such as to maximise the effect of blast.

9. A shell as claimed in Claim 7 or Claim 8 in which the underwater explosion is such as to maximise the production of bubbles.

10. A shell as claimed in any preceding claim comprising a plurality of fuse means and means to selectively enable at least one of the plurality of fuse means prior to firing the shell.

11. A shell as claimed in claim 10 in which the means to selectively enable is adapted to be operated when the shell is disposed in the gun from which it is to be fired.

12. A shell as claimed in claim 10 or 11 in which the plurality of fuse means are disposed in a common fuse housing.

13. A fuse for a shell comprising bathometric fuse means.

14. A fuse as claimed in Claim 13 in which the bathometric fuse means comprises a hydrostatic fuse.

15. A fuse as claimed in Claim 13 or 14 in which the fuse comprises time delay fuse means arranged to detonate a predetermined time after impact.

16. A fuse as claimed in any one of Claims 13 to 15 comprising proximity fuse means.

17. A fuse as claimed in any one of Claims 13 to 16 comprising impact fuse means.

18. A fuse as claimed in Claim 17 comprising means to inhibit operation of the impact fuse means until after the fuse has entered the water.

19. A fuse as claimed in any one of claims 14 to 18 comprising a plurality of fuse means and means to selectively enable at least one of the plurality of fuse means prior to firing the shell to which the fuse is to be fitted.

20. A fuse as claimed in claim 19 in which the means to selectively enable is adapted to be operated when the shell to which the fuse is to be fitted is disposed in the gun from which the shell is to be fired.

21. A shell substantially as hereinbefore described with reference to the accompanying drawings.

22. A fuse substantially as hereinbefore described with reference to the accompanying drawings.