ARRANGEMENT FOR COMBATING AIR TARGETS

Abstract: The present invention relates to an arrangement (shell) (1, 11 and 25) for combating air targets, comprising a proximity fuse (20, 26) with one or a number of narrowly delimited seeking directions (2, 8, 9, 21 and 26) together with the explosive charge (14, 28) included in the shell and one or more fragment-forming casings (12, 32) belonging thereto, which are designed in such a manner that, on detonation of the explosive (14, 28), the shell has ball sheaves aligned with the seeking directions (2, 8, 9, 21 and 30) of the proximity fuse.

Description: ARRANGEMENT FOR COMBATING AIR TARGETS The present invention relates to a new type of shell intended to increase mainly the effective range of anti-aircraft cannon by, in the case of all near misses, to the greatest possible extent concentrating the fragments formed on detonation of the shell in the direction of the target. The invention involves more specifically a combination of a specially designed explosive-charged shell forming fragmentε on its detonation and a special type of proximity fuse intended to initiate the explosive charge when a target is detected. The detailed construction of the proximity fuse per se has nothing to do with the invention, however, although the fact that it is available is a prerequisite for the invention. The aim of the invention is therefore partly to increase the potential of the AA artillery for combating extremely difficult targets such aε sea- skimmers etc. and partly to increase the effect of the individual shells on more conventional targets and partly to reduce the dependency of anti-aircraft cannon on entirely accurate range calculations which, in spite of the most modern technology possible, can be difficult to achieve in the rapid combat sequences which are now involved in combating air targets. Add to this that the number of targets which are extremely difficult to combat in the form of autonomous guided or self-guiding weapon carriers with small external dimensions can be expected to increase in the future since the air force seeks to an ever increasing extent to be able to combat a selected target without itself having to enter the risk area around the target. Naval and field barrel-type anti-aircraft weapons of today consist mainly of automatic cannons of 20-76 mm calibre and for these use iβ as a rule made of explosive- charged high-explosive shells or ball-type high-explosive shells which, at least in the larger 40-76 mm calibres, are usually equipped with proximity fuses for initiation in the case of near misses of the target. For direct hits on the target there are percussion initiation functions. The generation of proximity fuses in general use today has an antenna pattern with relatively undefined omnidirectional seeking beams, and in the same way the fragments formed on the detonation of the high-explosive shells and ball-type high-explosive shells of today are scattered radially from them about their own longitudinal axis. The advantage of a combination of the omnidirectional proximity fuse and the omnidirectional fragmentation shell is that, with this combination, there is no need to keep track of the rotational position of the shell which therefore simplifies the initiation system. It is therefore only necessary for the proximity fuse to have ascertained that the shell is sufficiently close to a target for initiation of the explosive to take place. The disadvantage, however, is that the energy of the explosive charge and of the fragments scattered on its detonation is scattered while turning and is therefore directed only to a limited extent towards the target. For a single 40 mm AA shell, this means that it must today be as close to the target as roughly 5 metres in order to ensure that the target is shot down. Considering the rapid targets of today, it will be absolutely clear that such a close hit picture requires extraordinarily accurate prediction. The aim of the present invention then is to provide a method and an arrangement for effectively combating air targets with explosive-filled shellε which are provided with proximity fuses, fired from anti¬ aircraft cannon and rotate in the trajectory towards the target. In order to increase the effect of the shells on the target, the fragmentation of the previous generation of AA shells, which was distributed symmetrically around their own longitudinal axis, has been replaced by a directed fragmentation where the dynamic scatter direction of the explosive charge and of the fragments has been concentrated in one or more directions which coincide with the seeking direction or seeking directions of the proximity fuse. At the same time, omnidirectional proximity fuses of the conventional Doppler radar type which were used previously have been replaced by a newly developed proximity fuse, the special feature of which is that it has one to four clearly delimited seeking or radiation directions. This proximity fuse may be a so- called optronic proximity fuse, which is actually a laser proximity fuse, but it may also be an IR proximity fuse or another direction-sensing proximity fuse with one or possibly a few specifically defined radiation directions which are aligned with the main direction or main directions of the fragmentation of the shell, which will therefore produce a concentrated fragment sheaf in the direction of the target on detonation of the shell. The fact that the radiation direction or radiation directions of the proximity fuse is/are aligned with the fragmentation means of course that consideration has been given to the flying speed of the shell and its rotational speed and also to the reaction time of the proximity fuse and its initiation function interacting therewith. Through this combination, we have gained access to a proximity fuse-initiated shell which is capable of effectively combating air targets at up to three times the detonation range from the target of the older types of proximity fuse-initiated shells of the same calibre which they are intended to replace. A further advantage of the combination according to the invention is that by these means we eliminate the problem which was inherent in earlier types of proximity fuse which, in the outer edge of their range area, had a tendency to trigger the detonation of the shells far too late, in other words when they had already passed the target. As this misfu ction was a direct consequence of the antenna pattern of the older types of proximity fuse, it was difficult to do anything about it. The complete shell made designed according to the invention may of course also be combined with other functional steps such as time release, initiation on direct hit, miss destruction etc. In the selection of dynamic main-action direction/main-action directions of the explosive charge and the fragments and with this the aligned radiation direction/radiation directions of the proximity fuse, there are a number of different alternatives. An alternative suitable for a proximity fuse with a single radiation direction is to arrange the main-action direction of the explosive charge and the radiation direction of the proximity fuse at an acute angle forwards in relation to the trajectory direction of the shell. As a result of the rotation of the shell, complete coverage is then obtained for a conical space extending in front of the shell and uniformly distributed around the axis of the trajectory of the shell. A corresponding part of the space will be scanned by the proximity fuse along a spiral path formed as the shell rotates. If on the other hand the seeking direction of the proximity fuse can form an angle which starts to approach a 90° angle with the projectile trajectory, the proximity fuse will scan the space around the projectile trajectory along a spiral path formed in a corresponding manner. Lastly, should the proximity fuse be provided with a number of seeking arms, the scanning pattern becomes denser with a number of spiral paths which run into one another. In the case of proximity fuses with a number of seeking directions, the shell must of course also be provided with a number of dynamic fragmentation directions aligned therewith. A variant of the invention which is suitable for combating larger targets such aβ aircraft is to make the proximity fuβe dependent on itβ rotation having indicated the target twice before the exploβive charge is initiated. Thiβ alternative iβ based on a microprocesβor coupled together with the proximity fuse, which has been programmed so that, during the firβt revolution of the shell in contact with a target, it can calculate the number of samples or contacts with the target in order that, during the second revolution, it can trigger the explosive charge after half the number of samples established during the first revolution. This procedure affordβ the maximum chance of total destruction of the target in the case of larger targets. In the case of small targets, however, e.g. sea- skimmers, the microproceββor connected to the proximity fuse must be programmed to initiate the explosive charge on the first target indication already since the target is in this case so small that the shell might otherwise pass the target before the next target indication could take place. It is of course a requirement that the proximity fuse does not initiate the explosive charge before the shell is within combat range even if it should detect the target within its seeking area much earlier. At least for the moment, however, the range of the proximity fuse should be the limiting factor in the great majority of cases. Quite generally, the present invention thus relates to an explosive-filled βhell which is preferably intended for combating air targets, fired in a trajectory towards the target by a barrel-type weapon and rotationally stabilized in the trajectory, and which is intended, when it is detonated, to scatter fragments in the direction of the target. The shell is also provided with a proximity fuse which initiates the detonation of the explosive when the target has been detected. The invention is characterized then by the combination of the proximity fuse being made direction-sensing and the casing of the shell which fragments on detonation of the exploβive being given βuch a shape that its dynamic f agmentation formed on detonation of the explosive coincides with the seeking direction of the proximity fuse. In this way, we have achieved a. proximity fuse- initiated βhell with a greater range than previously, in which the fragments from the detonation of the shell will always fall upon the detected target. Also forming part of the invention is the fact that the seeking direction of the proximity fuse is to form an angle of 15-90° with the longitudinal axis of the shell and that it can have up to four different simultaneous seeking directions distributed evenly around the periphery of the shell. The invention, together with its other characteristicβ, is defined in the patent claims below and it will now be described further in conjunction with the attached figures, in which Figure 1 shows one alternative embodiment of a shell provided with a proximity fuse with a seeking beam arranged obliquely forwards in the flight direction of the shell and, aligned therewith, a main combating direction for the active charge of the shell, Figure 2 shows another method of illustrating the scanning technique according to the invention, Figure 3 shows an alternative with a shell with two seeking beams directed in opposite directions and main combating directions directed parallel therewith, while Figures 4 and 5 show different variants of shells according to the invention. The shell 1 shown in Fig. 1 is located in the initial position A and the seeking beam 2 is directed obliquely upwards. Since the shell 1 rotates about its longitudinal axis, the seeking beam 2 will in principle enclose the cone which has the circular surface 3 as a base. This approach of course involves a given simplification since the shell also moves forwards a little during a revolution. The length of the cone is not infinite either since its length is delimited by the range of the proximity fuse. If the position is not simply obβerved at a given moment, it would therefore probably be more correct to βay that the βuccessively scanned area consistβ of the βpace around the trajectory of the βhell delimited by a radiuβ R limited by the ran -e of the proximity fuβe. In the figure, a target 4 haβ been drawn. When the shell 1 haβ reached position B, the seeking beam 2 (designated as 2' in position 6) strikes the target 4 and the exploβive charge of the βhell is initiated. Fragments which are emitted in this connection are scattered along the cone 5 marked in the figure and thus cover the target. That part of the surface 3 which the seeking beam 2' covers during an entire revolution on a level with position B has the base surface 6 in the figure. In this figure, the lines 2 and 2' actually mark, for greater clarity, the dynamic scatter direction of the fragments rather than the actual seeking direction of the proximity fuse since these two directions, as a result of the rotation and speed of the shell and the reaction time of the initiation system will require a number of degrees at the side of one another. In Figure 2, which represents another method of illustrating the scanning by the shell 1 of the space around it, that part of the surrounding space which the shell covers has been marked by the spiral curve which the radius R covers as a result of the rotation of the shell 1. Also drawn in the figure are the output lens β of the sensor belonging to the proximity fuse and the input lens d of the detector which interacts with the sensor. Figures 1, 2 and 3 involve obvious simplifications of the actual situation in that the dynamic fragmentation will never correspond to the normal to the fragmentation casing since both the projectile speed and the detonation of the explosive influence the direction of movement of the fragments. On the other hand, the seeking directions of the proximity fuse are correctly drawn in Figures 4 and 5 and it can be seen from these figures that the angular difference between these seeking directions and the respective fragmentation casing normal must be taken into account. The shell 7 shown in Figure 3 haβ two βeeking directionβ for itβ own proximity fuse designated by 8 and 9 in the figure. The two main combating directionβ of the βhell 7 have, aβ indicated above, for the sake of simplicity, been drawn here also as if they coincided entirely with the directionβ of the βeeking beams. It has been posβible to effect this simplification since it in — o — no way affects the principle of the invention but only its execution in practice. In position C, the seeking beam 8 of the proximity fuse indicates a target 10. The shell, however, is programmed for larger targets, as a result of which no initiation of its explosive charge takes place. During its first revolution in contact with the target, the processor of the shell linked to the proximity fuse indicates two sampleε, in other words the contact of the seeking beams 8 and 9 with the target. In position D, which corresponds to the position another half revolution later, in other words one revolution after the first contact with the target 10, the explosive charge of the shell 7 is initiated since all indications during one revolution together with a further half the number of indications during a subsequent revolution is considered to be a certain target indication. In thiβ case, the shell is assumed to be constructed in such a manner that it scatters fragments in two directions, on the one hand directly towards the target and on the other hand in the opposite direction. Other shell variants within the given inventive concept are of course also possible. If the shell has only one βeeking beam and is programmed for large targets, then its detonation is initiated on the second target indication of the sensor within two consecutive revolutions. Figure 4 shows a longitudinal section through an AA shell 11 comprising a forwardly directed active part 12 in the form of a fragmentation plate, which is at an angle relating to the longitudinal axis of the shell and behind which an explosive charge 14 is arranged. The part of the cylindrical part of the shell 11 which lieβ behind the fragmentation plate 12 but in front of the band 15 of the shell is deβigned as a conventional ball-type high- explosive shell with a large number of steel or heavy metal -.ragments 18 arranged between an outer and an inner caβing wall 16 and 17 reepectively (in thiβ case in the form of heavy metal balls) . The rear part 19 of the shell 11 on the other hand is made of a stronger material in order to function aβ a barrier in the formation of a concentrated fragment sheaf in the direction which covers the corresponding seeking direction of the proximity fuse arranged in the front part of the βhell, here deβignated by 20, the seeking direction being indicated by 21. Apart from the βeeking direction, no details of the proximity fuse 20 have been included in the figure. The initiation function 23 and the battery 24 necessary for the operation of the proximity fuse 20 are arranged in the rear part 22 of the shell 11. Figure 5 shows a shell 25 which is designed to be of larger calibre than that in Fig. 4, for which reason the proximity fuse 26 and the initiation function 27 of the shell do not in thiβ caβe occupy such a large part of the overall volume of the shell. The explosive charge of the shell iβ indicated by 28 in thiβ caβe and itβ band by 29. In this variant, the seeking direction of the proximity fuse is marked by the arrow 30 and inserted at the angle which covers the dynamic fragmentation direction of the fragmentation plate 32 which is in turn arranged parallel to the longitudinal axis 31 which coincides with its own trajectory direction. As can be seen from the figure, this alternative also gives a εlightly forwardly directed direction of action. The fragmentation plate 32 extends from a position directly behind the mounting of the proximity fuse 26 in the tip of the shell to a position directly in front of the band 29 of the shell. This means that it has been possible to make the rear part 33 of the shell, similar to the variant in Fig. 4, sufficiently strong to withstand the stresses to which the βhell will be expoβed on itβ firing via a barrel intended for thiβ purpoβe. Arranged between the fragmentation plate 32 and a special aerodynamically designed casing 34 which gives the βhell itε outer form iε a filling material 35. Thiε can alεo be uεed in order to balance the shell.

Claims: PATENT CLAIMS 1. Explosive-filled shell (1, 11 and 25) intended for barrel-type weapons, which iε intended preferably for combating air targets (10) , is fired in a trajectory towards said target (10) and rotationally stabilized in the trajectory, and is provided with a casing (12, 16-18 and 32) which iβ adjacent to the exploεive (14, 28) and forme fragmentβ on the detonation thereof and with a proximity fuse (20, 26) intended to initiate the explosive charge (14, 28) when the target (10) has been detected, characterized in that it comprises the combination of a proximity fuse (20, 26), which has one to four seeking directions (2, 8, 9, 21 and 30) which are laterally directed relative to the projectile trajectory of the shell (1, 11 and 25) , concentrated around its own main directions and narrowly delimited around theβe, and a fragment-forming casing (12, 32) which iβ aligned with the exploβive charge (14, 28) and designed in such a manner that, on detonation of the explosive (14, 28), it produces a dynamic fragmentation which is concentrated in the βeeking direction (2, 8, 9, 21 and 31) or βeeking directionβ of the proximity fuse. 2. Shell (1, 11 and 25) for combating air targetβ (10) according to Claim 1, characterized in that the scanning direction/scanning directions of the proximity fuse (20, 26) and the dynamic fragmentation directions of the fragments aligned therewith form an angle of 15-90° with the projectile trajectory of the shell. 3. Shell (1, 11 and 25) according to Claim 1 or 2, characterized in that its fragment-forming casing (12, 16-18) comprises a fragmentation plate (12) which is inclined relative to the longitudinal axis (13) of the projectile and formed from a large number of steel or heavy metal fragments together with binding material and behind whioh the explosive charge is arranged and which, on detonation of the explosive, produceε a dynamic fragmentation which is directed obliquely forwards in the flying direction of the βhell (25) , the proximity fuβe of the βhell having been given a seeking direction which is aligned with said dynamic fragmentation direction. 4. Shell (1, 11) according to Claim 3 or 4, characterized in that its side walls (16, 17) from the outer edge of the fragmentation plate (12) up to directly in front of the band (15) of the shell (11) is made as a conventional ball-type high-explosive shell with only thin casing walls (16, 17) together with a large number of steel or heavy metal fragments (18) arranged between the casing walls while the shell body behind the band is made of a more robust material. 5. Shell (1, 25) according to Claim 1 or 2, characterized in that itβ fragment-forming casing consists of a fragmentation plate (32) comprising a large nximber of steel or heavy metal fragments together with binding material, which (32) , a little way into the shell (25) , extends essentially parallel to the longitudinal axis (31) of the shell (25) from the front part of the shell where itβ proximity fuβe (26) iε located to a position directly in front of the band (29) of the shell, while the space in the direction of action of the shell behind the fragmentation plate (32) is filled with exploβive (28) while the εpace on the oppoεite εide of the fragmentation plate and out to a thinner outer casing (34) which defines the aerodynamic shape of the shell iβ filled with a filling material (35) , the βeeking direction of the proximity fuse coinciding with the dynamic fragmentation emerging from the fragmentation plate on detonation of the exploεive. 6. Shell (1, 11, 25) according to one of Claimε 1-5, characterized in that itε proximity fuεe (20, 26) iε of the two-armed type. 7. Shell (1, 11 and 25) according to one of Claimβ 1-6, characterized in that itβ proximity fuεe iε of t ie distance-measuring type or a combination with one of the two-armed type.

Inventors: KORPE LARS, KORPE, LARS
Applicants: BOFORS AB, KORPE LARS, KORPE, LARS
Application year: 1996
Main classification: F42C13
IPC codes: F42B12, F42C13