GB2434632A

GB2434632A - Shell with heat-sensitive sensor

Info

Publication number: GB2434632A
Application number: GB0012119A
Authority: GB
Inventors: Raimar Steuer; Martin Regensburger
Original assignee: Diehl Munitionssysteme GmbH and Co KG
Current assignee: Diehl BGT Defence GmbH and Co KG
Priority date: 1999-05-27
Filing date: 2000-05-19
Publication date: 2007-08-01
Anticipated expiration: 2020-05-19
Also published as: GB2434632B; GB0012119D0; FR2898409A1; DE19924360B3; FR2898409B1

Abstract

The pressure wave from the detonated warhead (15) of a shell (14) which is launched from the object to be protected is intended to deflect an approaching kinetic-energy projectile (11) from the direction of the approach trajectory (16) by the influence of pressure on its tail control surfaces. This results in a solution for the detonation sensor system for developing the blast effect in the optimum proximity situation which is particularly simple in terms of equipment and can be achieved in a mechanically highly robust manner if the blast shell (14) is equipped with a sensor (18) whose detector element (21) is arranged behind solid optics such that it produces a field of view in the form of a hollow cone coaxially in front of it. This leads to the emission of a trigger signal when the heated nose (12) of the fast approaching kinetic-energy projectile (11) enters this response characteristic (19).

Description

Shell for defence against an approaching kinetic-energy projectile The

invention relates to a shell according to the precharacterizing clause of Claim 1.

Such a shell is intended to be launched from a stationary or mobile target object, in particular such as an armoured vehicle, in the direction of an approaching arrow-type projectile, in order to defend against the acute threat by a detonation and fume pressure wave, which then originates from the detonated blast shell, acting on the stabilization wings at the rear of the kinetic-energy projectile. Said projectile is deflected from its approach direction, so that it no longer strikes the target object frontally but, at worst, at the side and thus without any lethal effect.

In comparison with reactive armour -for example in accordance with DE 4122622 Al or DT 977984 -where arrnoured plates are moved under the acceleration from explosive oriented in the opposite direction to the approach direction of the kinetic-energy projectile, or transversely with respect to it, such a protection concept has the advantage that the reaction forces to be absorbed on the object to be protected itself can be considerably reduced. Furthermore, appropriately aimed firing of blast shells allows the threatened object to be protected on all sides, even against a number of attacks successively from the same direction, as is described in more detail in the prior Patent Application No. 198 47 091.6 from this applicant and dated 13.10.98. In fact, it is necessary to produce an advantageous proximity situation in order that even a low-cost warhead, which therefore acts non-directionally, in the blast shell releases its pressure wave against the kinetic-energy projectile to be defended against as close as possible to the time when the blast effect acts predominantly on the tail area of the attacking kinetic-energy projectile, where its cross section is enlarged owing to the stabilization fins. On the other hand, if the primary effect were on the projectile nose, the kinetic-energy bar would in some circumstances not be deflected sufficiently from the approach trajectory, or the stabilizing effect of the tail fins could result in it being moved back to the critical-impact approach direction once again.

In order to detonate the blast shell at a functionally critical time in the approach kinematics of the projectile to be defended against, the cited prior patent application proposes that the optimum detonation command time for the blast warhead be calculated, and be transmitted without using wires to the blast shell, on board the object to be protected, from trajectory tracking of the two projectiles, that is to say using the kinematics of the attacking projectile and using the kinematics of the blast shell in order to defend it, taking account of predetermined, system-dependent delay times.

The sensor and data-processing complexity for such a process of determining the best detonation initiation time and for transmitting this as time information or as a trigger signal to the blast shell is, however, highly complex owing to the short available operational times and owing to the atmospheric transmission disturbances in the environment of the two projectiles, which are flying at high speed and are therefore severely heated by ionizing friction effects in the air. The present invention is therefore based on the object of determining the initiation criterion for the warhead charge for kinetic-energy projectile defence more easily, namely with less data-processing complexity and directly on board the blast shell.

By virtue of the main claim, according to the invention, this object is essentially achieved in that the blast shell is equipped with a detonation initiation sensor which detects the entry of the kinetic- energy projectile to be defended against, with its very severely heated projectile nose and, possibly, shortly after this, using the likewise severely heated wing tips in a sensor reception characteristic generated at the front of the shell; at which point the detonation of the blast warhead is initiated since this results precisely in an advantageous proximity position for the blast effect.

This avoids the considerable additional equipment fitted on board the object to be protected in order to track two trajectories simultaneously in the same observation sector and for calculations, derived from this, of potential collision points and for transmitting an optimization result, determined from this, to the blast shell for internal conversion to a detonation time. It is now sufficient to equip the blast shell with a simple infrared detector, which does not involve any major signal-processing complexity.

With regard to the extremely short passage time of the two projectiles which are flying past one another at high speed in opposite directions, it could actually still be problematic when determining the moment at which detonation should be initiated for the optimum effect to additionally have to take into account the propagation time of the blast wave from the shell to the kinetic-energy projectile to be defended against, as a function of the passage separation. However, additional data-processing complexity relating to this can be avoided if the sensor characteristic of the shell is directed in front in the form of a hollow cone -and, if required, its wall is for its part designed to have an approximately conical cross section with a comparatively large apex angle. This is because the detonation signal is generated earlier, the greater the transverse distance at which the kinetic-energy projectile enters the characteristic which, in practice, compensates for the correspondingly longer propagation time for the blast wave until the moment at which it is effective.

In any case, the pressure wave from the detonated warhead of a shell which is launched from the object to be protected will thus deflect an approaching kinetic-energy projectile reliably from the direction of the approach trajectory, by the influence of pressure on its tail control surfaces. This results in a solution for the detonation sensor system for developing the blast effect in the optimum proximity situation, whose equipment is particularly simple and which can be produced in a mechanically highly robust manner, if the blast shell is equipped with an infrared sensor whose detector element is arranged behind solid optics such

that it produces a field of view in the form of a

hollow cone coaxially in front of it. This leads to the emission of a trigger signal on the warhead when the heated nose of the fast approaching kinetic-energy projectile enters this response characteristic.

Further features and advantages as well as additional developments of the invention result from the further claims and from the following description of preferred exemplary embodiments of the solution according to the invention, which are sketched in highly simplified form in the drawing, limited to what is essential. In the drawing: Figure 1 shows the proximity situation between a kinetic-energy penetrator and a defence shell which exerts a blast effect on it, taking account of the geometry of its sensor response characteristic, Figure 2 shows a fish-eye detector for providing a sensor characteristic as shown in Figure 1, and Figure 3 shows an immersion lens for providing a sensor characteristic as shown in Figure 1.

The kinetic-energy projectile 11, which is approaching a stationary or mobile object that is to be protected, in particular a battle tank, is heated as a consequence of air friction owing to its high air speed, in particular on the projectile nose 12 and at the free ends of its stabilization wings 13 arranged in the tail area.

The attacking projectile 11 is intended to be intercepted by a blast shell 14 fired against it, by a preferably non-directional warhead 15 being detonated in an advantageous proximity position. The proximity position may be regarded as being advantageous when the blast effect initiated by the detonation acts predominantly on the tail area with the stabilization wings 13 of the kinetic-energy projectile 11, in order to deflect said projectile from its severe-impact orientation in the direction of the attack trajectory 16 as it passes the blast shell 14, or even to divert it entirely from this trajectory which, until then, has been aimed at the object to be protected.

In order to detonate the warhead 15 at the moment of advantageous relative proximity between the attacking projectile 11 and the defence shell 14, a sensor 18 is fitted in the front area 17 of the latter, and this sensor 18 reacts to the extreme heating of the approaching kinetic-energy projectile 11. To this end, the heat sensor 18 has a response characteristic 19 which is oriented neither exactly transversely nor exactly in front, but with the field of view preferably opening concentrically in front with respect to the trajectory of the shell 14 in the direction of flight like a truncated hollow cone -as can be seen from Figure 1 of the drawing. For its part, the wall of the hollow cone may likewise expand conically in axial section.

In order to initiate its defence function, the blast shell 14 is therefore equipped with a sensor 18 with an omnidirectional view, which supplies a detonation signal 20 to the blast warhead 15 as soon as at least the heated nose 12 of the approaching kinetic-energy projectile 11, and/or its likewise heated tip of the stabilization wings 13, enters the response characteristic 19 of the sensor 18. Owing to the hollow-conical characteristic, this moment is reached earlier as the trajectories approach, the greater the transverse distance between-the attacking projectile 11 and the defending projectile 14.

The detonation initiation sensor 18 fitted in the front area 17 of the blast shell 14 may contain a detector with Peltier cooling in order to achieve a wide operating temperature range; alternatively it may contain an infrared semiconductor detector, whose equipment is less complex, which is physically smaller, and operates at the ambient temperature. In order to achieve the sensor response characteristic 19 which is oriented in the form of a funnel in front, an annular detector element 21 (or a number of discrete detector elements arranged along a circular arc) can be arranged behind a fish-eye objective lens, as is shown in symbolic, simplified form in Figure 2. The sensor 18 can be constructed with simpler equipment and to be more robust bearing in mind the stresses during firing if, according to Figure 3, the annular design of the detector element 21 is borne directly behind a solid base in the form of an immersion lens 22 composed of silicon, with its high refractive index (whose order of magnitude is considerably more than three) . This arrangement also results in a sensor 18 having a detection cone with relatively wide walls and a defined aperture angle as the response characteristic 19.

In the projectile and movement axis of the shell 14, the convex front face of the immersion lens 22, which has an antireflective coating, is expediently fitted with a central cover 23. This also avoids the detector element 21 being overdriven irrespective of the circular free space in the centre of said detector element 21, since the radiation that is incident directly from the direction of flight is suppressed, because the interception situation is typically not a collision but a flight past the other object. Opposite the convex front, the lens -22 has the detector element 21 fitted to its planar rear face, preferably with the interposition of an optical filter 24 in order to block solar radiation.

In order to assist the process of making the sensor operation independent of direct and reflective solar radiation, whose main intensity occurs at a wavelength around 4.2 pm, not only is the optically blocking filter 24 provided, but also a detector element 21 composed of a material such as PbSe (lead selenide), which actually operates in the radiation spectrum around a wavelength of 4.2 pm. This is because this is the point where the greatest atmospheric absorption of heat radiation occurs, due to water vapour, and which therefore has the greatest attenuating effect on the long atmospheric transmission path of the sunlight while, in contrast, having scarcely any effect on the short propagation path of the thermal energy from the kinetic-energy projectile 11 to the detector element 21 which, in the end, amounts to only about 1 metre or less (Figure 1) In addition, it may also be expedient to suppress the effects of solar radiation electrically. For this purpose, a filter circuit 25 is connected downstream from the sensor 18 and, for its part, supplies only the detonation signal 20 to the blast warhead 15. The operation of the filter circuit 25 is based primarily on the fact that the hot points of the kinetic-energy projectile 11 produce at least a very short high-frequency voltage pulse as the response characteristic 19 of the sensor 18 moves quickly across its detector element 21. In comparison to this, the radiation from a hot spot located virtually in a stationary position in the field of view, as in the case of solar radiation, produces only a very low-frequency signal via the detector element 21, namely depending on the oscillatory movements of the blast shell 14 on its trajectory towards the kinetic-energy projectile 11.

This significant frequency difference can be used in the filter circuit 25 to suppress the influence of sunlight, for example by means of a conventional bandpass filter for a typical band from 200 Hz to kHz.

No complex electronics and, in particular, no signal processor either are therefore required to produce the filter circuit 25 in order to mask out solar influences electrically. The filter circuit 25 is at the same time expediently designed for a certain reaction delay between the occurrence of the trigger signal, which is supplied by the detector element 21 when the kinetic-energy projectile 11 to be defended against enters the sensor response characteristic 19, and the actual initiation of the blast warhead 15, in order that the blast wave reliably acts on the kinetic-energy projectile 11 to be defended against only behind its centre of gravity in order to deflect it transversely, as described initially.

Claims

-10 -Claims 1. Shell (14) for defence against an approaching

kinetic-energy projectile (11) by blast effect in particular against its stabilization wings (13), characterized in that the shell (14) is equipped with a heat-sensitive sensor (18) as a proximity sensor for blast initiation.

2. Shell according to Claim 1, characterized in that its sensor (18) has a hollow-conical response characteristic (19), coaxially in front in the direction of flight.

3. Shell according to Claim 1 or 2, characterized in that, in its front area (17), said shell is equipped with a sensor (18) in the form of an infrared detector element (21) arranged behind fish-eye optics.

4. Projectile according to Claim 1 or 2, characterized in that, in its front area (17), said projectile is equipped with a sensor (18) in the form of an infrared detector element (21) arranged behind an immersion lens (22) 5. Projectile according to Claim 4, characterized in that the immersion lens (22) has an annular detector element (21) on its planar rear face, and has a cover (23) in the centre of its convex front face.

6. Projectile according to Claim 4 or 5, characterized in that a solar filter (24) is -11 -arranged between the detector element (21) and the immersion lens (22) 7. Projectile according to one of the preceding claims, characterized in that the sensor (18) is equipped with a detector element (21) whose main sensitivity is in the wavelength band around 4.2 pm.

8. Projectile according to one of the preceding claims, characterized in that a filter circuit (25) having a pass band in the region between approximately 200 Hz and 200 kHz is connected downstream from the sensor (18) Amendments to the claims have been filed as follows 1. Shell for defence against an approaching kinetic-energy projectile by a blast effect which acts predominatelY against stabilization wings in the tail area of the projectile, the shell being equipped with a heat-sensitive sensor which has a hollow-conical response characteristic located coaxially in front of the shell in the direction of flight and is provided with a detector for blast initiation in which the sensor comprises an immersion lens having a planar rear face with the detector in the form of an annular infrared detector element arranged behind it, and a convex front face with a cover in its centre.

2. Shell according to Claim 1, in which a solar filter is arranged between the detector element and the immersion lens.

3. Shell according to Claim 1 or 2, in which the main sensitivity of the detector is in the wavelength band around 4.2 um.

4. Shell according to Claim 1, 2 or 3, in which the signal from the sensor for blast initiation passes through a filter circuit having a pass band in the region between approximately Hz and 200 kHz.