Subwarhead

Abstract: The invention relates to a subwarhead which is arranged to be separated from a missile, for example a carrier shell or the like, over a target area. The subwarhead comprises an active part, a target detector and an arrangement which imparts a rotation to the subwarhead for scanning of the target area in a helical pattern during the descent of the subwarhead towards the target area, the target detector being arranged displaceably in order to allow a free view at the side of the active part. Two diametrically situated aerofoils (1, 2) are arranged to be pivotable, each on its own shaft (4, 5), which shafts are situated in a plane which is at right angles to the axis of symmetry of the active part, from a folded-in position, in which the aerofoils connect with the outer surface of the subwarhead, to a position folded out by 90°, in which the two aerofoils form a braking area for the rate of descent of the subwarhead.

Description: The present invention relates to a subwarhead arranged to be separated from a missile, for example a carrier shell or the like, over a target area, the subwarhead comprising an active part, a target detector and an arrangement which imparts a rotation to the subwarhead for scanning of the target area in a helical pattern during the descent of the subwarhead towards the target area. Such a subwarhead is previously described in SE-A-86 01423 and in its EPO equivalence EP-A-0 252 036, forming the basis for the preamble of independent claim 1. Characteristic of the subwarhead described in said patent is the fact that the target detector is arranged pivotably on a bearing shaft which is parallel with the line of symmetry of the active part in order to allow pivoting out of the target detector from a folded-in position, in which the optical axis of the target detector coincides with the line of symmetry of the active part, to a folded-out position, in which the optical axis of the target detector is parallel with the line of symmetry of the active part, in order to allow a free view by the target detector at the side of the active part, and furthermore that an aerofoil is pivotably arranged on a bearing shaft which is also parallel with the line of symmetry of the active part in order to allow pivoting out of the aerofoil from a folded-in position to a folded-out position at the side of the active part. By means of an expedient aerodynamic design of the subwarhead and the braking area of the detector and the aerofoil, a suitable rate of descent of the subwarhead and furthermore a driving moment, which imparts to the subwarhead its rotation, around the axis of spin are obtained. This is brought about without assistance from a parachute, which is an advantage since the parachute takes up space. Within the available space in a carrier shell, an increased space can instead be made available for the active part itself. Although the subwarhead described above has proved to have good characteristics as far as rate of descent and scanning rotation are concerned, it has become desirable to be able to increase the braking area further. This can be the case, for example, when it is desired to use heavier active parts. The braking area of the target detector and aerofoil is limited to the cross-sectional area of the cylindrical subwarhead, which can result in the rate of descent becoming too high with the existing size of the braking area if the weight of the active part is increased at the same time. The aim of this invention is in the first instance to produce a subwarhead of the abovementioned type but with a substantially greater braking area. According to the invention, this is achieved in a simple manner and without it being necessary to use extra space. The features of the invention emerge from the characterizing part of independent Claim 1. The invention is described below in greater detail with reference to the attached drawing which shows an example of how a subwarhead according to the invention can be designed. In Figure 1 a side view of the subwarhead is shown, partly in cross-section, and in Figure 2 a perspective view is shown, the subwarhead being shown in both cases in its folded-out position. The subwarhead is assumed to have been separated from a carrier shell. The carrier shell can be one of 15.5 cm calibre, for example, which has been fired from a field artillery piece in conventional manner in a ballistic trajectory towards a target area. In order to give the subwarhead a controlled movement of scanning of the target area, that is to say a controlled rotation and rate of descent, two diametrical aerofoils (1, 2) are arranged to be pivotable from a folded-in position, in which the aerofoils connect with the outer surface 3 of the subwarhead, into a folded-out position, in which the two aerofoils form a braking area. The two aerofoils 1, 2 are pivotably arranged on folding-out shafts 4, 5 which are at right angles to the line of symmetry of the active part. The active part 6 can be of a type known per se and is thus not described further here. In contrast to the subwarhead which is described in SE-A-86 01423 mentioned in the introduction, the target detector in this case constitutes a separate part 7 from the two diametrically suspended aerofoils 1, 2. In order to allow a free view at the side of the active part, the target detector 7 is arranged to be displaceable or pivotable from a folded-in position in the stirrup-like superstructure 8, in which the two folding-out shafts 4, 5 are also arranged, on the active part. By virtue of this construction, the two aerofoils can be given a greater braking area. They can furthermore be made comparatively thin, which is favourable as far as weight is concerned. The aerofoils can be made of titanium, for example, and are curved so that they have a given radius in their folded-out position. The material is elastically flexible so that the aerofoils, in the folded-in position, connect with the outer surface of the subwarhead but, in the folded-out position, are bowed out into their curved position. By means of varying the curvature of the aerofoils, a further parameter is obtained for varying the flight characteristics. The aerofoils can furthermore be of different length, which influences the rate of rotation of the subwarhead. In their folded-in position, the aerofoils are locked to the outer surface of the subwarhead in a suitable manner, for example the thin aerofoil profile can engage in a groove or slot in the outer surface. The aerofoils are rotated from their folded-in position with the aid of their internal energy, rotational and air forces by approximately 90° into their folded-out position. Expediently, a damping element is installed so that the aerofoils are stopped gently in the folded-out position and any oscillations are prevented. If necessary, this can be combined with a given time delay so that the two aerofoils are folded out only a given time after the subwarheads have been separated from the carrier shell. In this connection it should also be mentioned that a subwarhead provided with diametrically arranged aerofoils which are pivotable on shafts of their own in a plane perpendicular to the axis of symmetry of the active part of the warhead is known in the art through DE-C-265 383. The warhead according to said patent is however of quite another type as it is not provided with any target detector at all and as the aerofoils are of quite another shape. The two aerofoils can be combined with an aerodynamic rotational brake of a type known per se, of the type, for example, which is described in SE-A-86 05123.

Claims: Subwarhead arranged to be separated from a missile, for example a carrier shell or the like, over a target area, the subwarhead comprising an active part (3), a target detector (7) and two diametrically situated airofoils (1, 2), said airofoils (1, 2) imparting to the subwarhead during its descent towards the target area a braking action and a rotation of spin around the subwarheads axis of spin whereby making the target detector (7) to scan said target area in a helical pattern during said descent, said target detector (7) being arranged displaceably or pivotably in order to allow a free view at the side of the active part (3) and said aerofoils (1, 2) being arranged to be pivotable, each on its own shaft (4, 5), from a fold-in position, in which they connect with the outer surface of the subwarhead, to a position folded out 90°, whereby forming a braking area imparting said braking action characterized in that the aerofoils (1, 2) are made from an elastically flexible material so that when the aerofoils (1, 2) pivot out from their folded-in position they at the same time are bowed out into a precurved predetermined curvature selected for desired flight characteristics and which curvature is maintained in said unfolded position. Subwarhead according to claim 1 characterized in that the aerofoils are of different lengths.

Inventors: VESA REIJO, VESA, REIJO
Applicants: BOFORS AB, AKTIEBOLAGET BOFORS
Application year: 1990
Main classification: F42B10
IPC codes: F42B10