METHOD FOR INCREASING THE PROBABILITY OF IMPACT WHEN COMBATING AIRBORNE TARGETS, AND A WEAPON DESIGNED IN ACCORDANCE WITH THIS METHOD

Method for increasing the probability of impact when combating airborne targets, and a weapon designed in accordance with this method.

The present invention relates to a novel method, and to a projectile deεigned in accordance therewith, for increasing the probability of target impact when combating airborne targets by means of a projectile which is filled with explosive, is fired towards the target, rotates in its trajectory, and creates splinters upon itε own detonation, which is initiated when the target is indicated by a proximity fuse.

The method and the projectile in accordance with the invention are in the first instance conceived for use in connection with those weapons which, because they are not equipped with advanced sighting and tracking systems adapted for combating aircraft, depend to a particularly large extent on exerting an impact on the target even in the event of serious misses, for example of up to 10 to 100 metres.

Developments in the field of aviation, both in the form of conventional aircraft, attack helicopters and anti-tank helicopters, and also guided and self-piloting missiles, have increased the requirements of even quite small military units for simple and effective anti¬ aircraft weapons; requirements which the air defence equipment available at present will never be able to satisfy completely. This is particularly so because the enhanced airborne capabilities have been forcing the established anti-aircraft systems to become ever more sophisticated, and therefore expensive, if they are to have any possibility of combating the enemy aircraft under all circumstances. λs has already been indicated, the present invention is in the first instance intended to be used in relatively simple weapon systems and in those which for some other reason do not have sighting and tracking equipment adapted for combating airborne targets, for example guns intended for other main purposes, for instance tank guns, or, alternatively, relatively simple one-man weapons or team-operated weapons intended for direct anti-aircraft combat, for example of the back- blast, countermass or rocket type. What may be regarded as a common feature of these types of weapons is the fact that they are principally employed in rapidly developing self-defence situations against more or less direct attacks from aircraft, and ,in these circumstances both the absence of appropriately advanced sighting equipment and the lack of time for preparation impose extra high demands on the range of impact of the weapon in the event of near misses. Thus, in order to achieve the result which is sought in connection with the invention, what is needed is, on the one hand, a warhead with a sufficient impact range, and, on the other hand, a proximity fuse for firing the impact component with sufficiently active range, and a search system adapted for the purpose of identifying actual targets and eliminating any error indications. In addition, there is of course the system carrier or the actual projectile. In a preferred embodi¬ ment, this can consist of an autonomous projectile fired, using rocket or backblast technology for example, from a launch barrel of the single-shot type. Such a weapon would be an inexpensive and efficient weapon for the infantry, for example, for defence against low-flying aircraft. The generation of proximity fuses which are today in active service, primarily in anti-aircraft guns and missiles, are of the Doppler radar type with omni¬ directional search beams, and, at least near ground level, with short feasible ranges of 2 to 5 metres, for example. These proximity fuses do not give any direc¬ tional information in respect of the indicated target, but simply indicate the proximity to a possible target. Since the present-day impact components are also designed so that they scatter their splinters radially upon detonation of their explosive charge, the inability of the proximity fuse to define the direction to the target has not represented any disadvantage, other than the fact that both the proximity fuse and the active charge squander some of their inherent energy in the direction away from the target.

In accordance with the present invention, it is now proposed instead that both the proximity fuse and active charge be made direction-dependent, something which is entirely feasible if we take as our starting point the basic knowledge which is available at present. In this connection, it would be possible for both the range of the proximity fuse and the impact range of the impact component to be increased very considerably, without the energy supply to either of them needing to be increased, but instead merely being concentrated in one or more active directions. The possibility of being able to cover the area around the projectile trajectory using a weapon constructed in accordance with this basic principle doeε of course already exiεt for any projectile which rotates in its trajectory.

Calculations have shown that the range for a warhead designed in accordance with the present inven¬ tion, that is to say the range of both the proximity fuse and of the active charge, could be increased, using these basic principles, by a factor of 10 compared with an impact component of equal size and of an earlier and nowadays conventional construction, and it is undeniable that this could be of very great value. Another advantage of a direction-sensing prox¬ imity fuse of the type characterizing the invention is that it should be entirely possible, with its help, to obviate the problems which today's proximity fuses give rise to on account of the fact that they have a tendency, because of the form of their antenna pattern, t s trigger the explosive charges of the warheads too late around the outer limit of their range, that is to say only after the projectile haβ passed the target.

The advantages afforded by the present invention also include the fact that a considerable increase in capability should be possible, even in the case of the fully modern anti-aircraft gun, if the principles of the invention are applied thereto. The present invention could thus be defined in the first instance as a method, and in the second instance as a device, for combating airborne targets by means of a projectile which is charged with explosive and provided with a proximity fuse and which is fired in a trajectory towards the target, rotating about its own longitudinal axis, and which, when a target is indicated by the proximity fuse, is initiated to detonate and on detonation scatters splinters in the direction towards the target. The characteristic feature of the invention is that the proximity fuse included in the projectile is given at least one, but no more than four, search direc¬ tion(ε) which iε (are) limited narrowly to the sides and oriented at an angle of 15 - 90° to the trajectory direction of the projectile, and at the same time the splinter-forming shell of the projectile iε designed such that its dynamic splinter directions, created upon detonation of the explosive, completely cover possible contacts of the proximity fuse with targets within its own range, but independently of the distance to the projectile trajectory.

The search direction or search directions of the proximity fuse will be coordinated with the dynamic splinter-scattering direction or splinter-scattering directions of the actual projectile, and in this context it is of course necessary to take into consideration both the velocity of the projectile and its speed of rotation, and also the reaction time of the initiation system cooperating with the proximity fuse.

In accordance with this basic principle, the proximity fuse can then be designed with two search arms which lie extremely close to one another and are other¬ wise identical (for example, diverging by only one degree or a few degrees) . With this basic construction, it is in fact easy to eliminate a large number of different error indicationε, since two completely different indications (i.e. with differences greater than a defined limit value) for both the search arms can very probably be regarded as meaning that one search arm has struck a target while the other lies outside. By contrast, two identical indications which are not changed within a predetermined sequence can very probably be regarded as signifying ground contact, water or, under certain conditions, clouds. The various features of the invention are defined in the attached patent claims, and the invention will now be described in somewhat greater detail with reference to the attached figures, of which Fig. 1 shows a sketch of an example of use, and Fig. 2 shows the main parts of the projectile used in connection with the invention.

Fig. 1 thus shows a marksman 1 equipped with a weapon 2 which is designed in accordance with the inven¬ tion and which consists of a launch barrel and a projectile 3 launched from this barrel by means of a gas generator or in some other way. The main parts of the projectile 3 are shown in Fig. 2. The marksman 1 in Fig. 1 iε under threat from an attack helicopter 4, against which he has therefore fired his weapon. The projectile 3 follows the trajectory 5, shown in the figure, in the direction towards the target. While the projectile is flying on the trajectory 5, a proximity fuse 6 (see Fig. 2) , which is incorporated in the projectile, successively searches, via a narrowly limited search beam moving along a helical track defined by the rotation of the projectile, the surrounding area out to and including the maximum range of the proximity fuse. In the figures, this search beam is intentionally shown only as individual dashed lines 7. The intention is in fact that these will have a lateral extent which is as small as is technically possible. The area around the projectile trajectory scanned by the proximity fuse is indicated in Figure 1 in the form of a spiral line 7', which thus symbolizes the longest range of the proximity fuse. When the proximity fuse 6 has indicated the target 4, the active charge 8 of the projectile is detonated, whereupon a hail of splin¬ ters fired in the direction of the site of the target indication is formed.

The projectile 3 shown in Fig. 2 comprises, in its forward part, the previously mentioned proximity fuse 6 with associated electronics which can include a programmable microprocessor and, immediately behind the latter, the active charge 8, a main drive motor 9, and a starter booster 10. The proximity fuse 6 can, for example, be a so-called optronic laser proximity fuse, an IR proximity fuse, or a proximity fuse of another basic type. A precondition for the proximity fuse in question iε that it must have one to four concentrated search beams distributed evenly around the circumference of the projectile and with a very narrowly limited extent transverse to the search direction.

Fig. 2 also indicates two different positions of the target 4 (4' and 4'') when the latter is struck by the search beam of the proximity fuse. These two posi- tions lie at different distances from the projectile trajectory 5. When the proximity fuse 6 indicates targets at position 4', the active charge 8 iε initiated, and a concentrated hail of splinters, formed on detonation of the active charge, is thrown towards the target along the trajectory 11' which shows the centre line of the hail of splinters.

To begin with, the hail of splinters has a movement slightly obliquely forwards relative to the direction of movement of the projectile but, as the component of movement in the trajectory direction is decelerated by the wind in the atmosphere, the direction of movement of the hail of splinters will become ever more radial the further the hail of shot has travelled away from the projectile. This has been illustrated in Fig. 2 by mean, of the target position 4'' and splinter scatter 11' ' .