Spin-Stabilized Bomblet-Carrying Projectile

1. Field of the Invention

The invention relates to a spin-stabilized payload-carrying projectile containing bomblets and fillers disposed between the bomblets and the housing of the projectile.

2. Discussion of the Prior Art

Such payload-carrying projectiles are described, for example, on page 113 of the magazine "Wehrtechnik" [Military Engineering], vol. 10/85. A corresponding bomblet-carrying projectile is also shown in FIG. 3 of U.S. Pat. No. 3,981,244.

In known bomblet-carrying projectiles the fillers are normally made of plastic or aluminum and are used for securing the bomblets inside the projectile as well as for imparting the spin of the payload-carrying projectile to the bomblets. The longitudinal and transverse moments of inertia of the payload-carrying projectile which determine the ballistic stability are in general determined in these projectiles by many quantities including: the mass of the bomblets, the projectile base, the housing of the payload-carrying projectile as well as the nose of the projectile and the ejection charge contained in the nose of the projectile. A spinning projectile is considered to be stable if an incident angle produced by a disturbance disappears again.

If the distribution of mass of the bomblet-carrying projectile mentioned above is changed by the use of a considerably thinner housing than the customary housing of a payload-carrying projectile (for example in order to contain larger bomblets in the payload-carrying projectile), a negative effect on the ballistic stability of the bomblet-carrying projectile can result. This is so, because a change of the distribution of mass also leads to a change of the longitudinal and lateral moments of inertia which may result in a change in the ballistic stability.

It is an object of the present invention to achieve in a particularly simple manner the distribution of mass (or the moment of inertia) necessary for ballistic stability in bomblet-carrying projectiles with thin housings.

The above and other objects are accomplished by the invention in which a projectile for dispensing a payload at a selected point along its trajectory comprises filler pieces which are of steel or tungsten, and which are distributed in the projectile casing between the bomblets such that the projectile flies stably up to the point of ejection of the bomblets.

FIG. 1 is a longitudinal section of a preferred embodiment of the invention.

FIG. 2 is an enlarged sectional view taken along line II--II of FIG. 1.

In FIG. 1 the bomblet-carrying projectile 1 includes a nose 2 of the projectile, an ejection charge 20 contained in the nose, a casing or shell 3 of the payload-carrying projectile and a base 4.

The bomblets 30 and fillers 31-37 are inside the bomblet-carrying projectile 1. The center of gravity of the bomblet-carrying projectile 1 is at 5. Adapter rings 40 which contain the fuses for the rear layer of bomblets, are located between the projectile base 4 and the rear layer of bomblets oriented toward the projectile base.

In FIG. 2 a cross section through the bomblet-carrying projectile is shown.

The bomblet-carrying projectile can for example, be a 155 mm round, which ignites the ejection charge 20 after a pre-set time interval. The bomblets 30 are pushed out of the rear by the gas pressure being created in the nose of the projectile. In the present example six layers of bomblets with seven bomblets per layer are discharged over the target.

To utilize the interior of the bomblet-carrying projectile 1 as optimally as possible, a projectile housing 3 as thin as possible is to be used, i.e. the ratio of the wall thickness of the casing 3 of the payload-carrying projectile to the caliber of the barrel should be less than 0.05.

If the bomblet-carrying projectile is to fly stably, the distribution of mass must be selected such that an incident angle produced by a disturbance disappears again. In connection with the stability requirements of spin-stabilized projectiles see the "Handbook on Weaponry", second English Edition, 1982, pages 178-180 (published by Rheinmetall GmbH).

According to the invention, to achieve the mass distribution, that is, the moments of inertia about the projectile axis and a transverse axis passing through the center of gravity of the bomblet-carrying projectile 1, a particular material and a particular placement of the fillers 31-37 are provided.

In the bomblet-carrying projectile shown, the fillers 31, 32 and 35, 36, 37 are of steel. The fillers 33 and 34 which are in the vicinity of the center of gravity 5 are of heavy tungsten metal.

As seen in FIG. 2, the bomblets are of generally circular cross-sectional outline and are arranged in a cluster about the longitudinal axis A of the projectile. Circumferentially adjoining bomblets 30 are in contact with one another and each bomblet 30 furthermore contacts the inner wall face of the casing 3. The filler pieces 34, as well as the other filler pieces which are, as viewed axially, in front of or behind the filler pieces 34, are each situated in the space which is of generally triangular cross section and which is defined by two adjoining bomblets 30 and the inner surface portion of the casing 3 extending between such two adjoining bomblets. For a matching fit, each filler piece has two concave face portions complemental with the convex face portions of the adjoining bomblets 30 and a convex face portion which, in turn, is conforming to the concave inner wall portion of the casing 3.

By means of this arrangement, the following mechanical data are arrived at with a bomblet weight of 0.432 kg:

Mass: 47.8 kg

Longitudinal moment of inertia: 163,000 kg.times.mm.sup.2

Transverse moment of inertia: 1,796,000 kg.times.mm.sup.2

Revolution: U=15,600 rpm

A factor of stability S of 1.42 is calculated from these data, in accordance with the above-cited Rheinmetall publication. Since stable flight is ensured when S.gtoreq.1, the embodiment described above produces a stably flying projectile. If instead of steel and heavy tungsten metal the normally used plastic fillers have been employed, a factor of stability of S=0.79 would have resulted; or when using aluminum fillers S=0.86 would have resulted.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.