An improved armor-piercing inertial penetrator projectile having a prepenetrator which has a substantially uniform flight diameter D, over substantially its entire length. A prepenetrator assembly is formed by a plurality of elements which are adapted to interact with the material of the corresponding target upon impact so as to form an effective surface which has a diameter larger by a predetermined amount than the flight diameter D of the prepenetrator.

BACKGROUND OF THE INVENTION 
The invention relates to an armor-piercing inertial projectile 
(hyper-velocity kinetic energy penetrator projectile) with a 
prepenetrator, which has a substantially uniform diameter over its entire 
length. 
Such type projectile is, for example, described in U.S. Pat. No. 4,098,194. 
The effect of the penetrator on an inclined armored plate was determined to 
be such that the axis of a penetration channel, which is formed at impact 
extends in proximity to the surface normal and therefore encompasses an 
angle with the firing direction of the projectile. This causes penetrators 
made of steel to bend and with heavy metal penetrators to break up or 
disintegrate which detracts significantly from the target effectiveness of 
the corresponding penetrator when impacting on a multi-plate armored 
target. 
SUMMARY OF THE INVENTION 
It is an object of this invention to avoid the interaction between an 
inertial project and an armored plate which causes bending and breaking of 
the projectile and to thereby improve the penetration capabilities of the 
corresponding penetrator.

DETAILED DESCRIPTION 
According to FIG. 1 there is illustrated an inertial projectile having a 
longitudinal axis A and a pre-penetrator 10 with a nose 12 and an 
intermediate region and at the rear of which a region 80 is disposed to 
which a not further illustrated and described main penetrator adjoins. The 
pre-penetrator 10 has a projectile diameter D.sub.1 (hereinafter referred 
to as the flight diameter) and is provided with a nose body 22, the rear 
portion of which is formed as a frusto-conical surface 25. In the 
intermediate region between the nose 12 and the region 80 there are 
disposed a plurality of funnel-shaped first elements 16.1, 16.2, 16.3. The 
element 16.3 is matingly adapted with its funnel-shaped front surface 36, 
defined by a cutting edge 40, to the frusto-conical surface 25 and 
directly adjoins the latter. With a predetermined wall thickness the 
element 16.3 defines at its rear side a frusto-conical surface 37; there 
follow still two further similarly shaped first elements, that is element 
16.2 and 16.1. All three first elements 16 form a stack. The rear most 
element 16.1 adjoins at its rear side directly a funnel-shaped front 
surface 82 of the penetrator region 80. In the region of longitudinal axis 
A there is provided an axial connecting element 44, for example a stay 
bolt, which is provided with a front threaded portion 46 and a rear 
threaded portion 48. The rear threaded portion 48 connects the stay bolt 
44 with the main penetrator, whereas the front threaded portion 46 is 
screwed on to the nose body 22. The shaft 45 of the stay bolt 46 extends 
through the central opening (not illustrated in detail) of the elements 16 
. . . , whereby the stack of elements 16 . . . , is fixed in the 
intermediate region. 
When impacting a conventionally inclined armored plate of a multi-layer 
target there is formed the first portion of a penetration channel by means 
of the nose body 22. As soon as the element 16.3 contacts with its cutting 
edge 40 the target material of a corresponding armor plate, it spreads out 
in view of its shape, whereby its effective diameter increases relative to 
the main diameter D.sub.1. The elements 16.2 and 16.1 behave 
correspondingly and ensure thereby that a sufficiently large penetration 
channel and exit-crater are achieved in the corresponding target plate, so 
that the following main penetrator is not hindered and consequently can 
become target effective in accordance with its hyper-velocity as well as 
also its mass to impart increased kinetic energy against the following 
target plate(s). 
The embodiment of FIG. 2 differentiates itself from the embodiment of FIG. 
1 in that the portion 451 which extends between the threaded parts 46 and 
48 of the stay bolt 44 is of frusto-conical shape and in that an element 
17 is provided, which abuts with a flat plan rear surface 17.sup.1 against 
a front end surface 84 of the region 80. 
The elements 16 . . . , whose number can be predetermined, can be adapted 
to different targets and be made out of different material and can have 
different wall thicknesses. 
The embodiment of FIGS. 3 and 3a includes two pipe-shaped elements 18. A 
plurality of pipes with corresponding different exterior diameters are 
coaxially arranged. These pipes abut with their rear sides 52 against the 
flat front end surface 84 of the region 80 and are adapted to bear 
according to their lengths with their forward sides 50 against the conical 
surface 26 for mutual bracing. The elements 18 have a plurality of slits 
58 which extend in the longitudinal direction from the front side 50 to 
the rear-sided annular region 60. The outer element 18 is surrounded at 
its outer periphery by a jacket 30, the inner surface of which is not 
designated with a reference number and is immediately adjacent to the 
peripheral surface 54 on the outer element 18. The jacket 30 is joined 
with the nose body 22 in a forward connection zone 32 and with the 
rear-sided adjoining penetrator region 80 at a rear-sided connecting zone 
88 in a manner only schematically illustrated and not described in detail. 
In this manner all corresponding parts are arranged and fixed with respect 
to each other in a predetermined manner. 
When impacting on a conventional inclined armor plate of a multi-layer 
target there is again formed the first portion of the penetration channel 
by means of the nose body 22. The jacket 30 tears and, as a result of the 
movement of the surface 84 in the firing direction, the elements 18 are 
repelled by the frustoconical surface 26 in such a way that they move with 
their forward sides 50, due to inter-action with the material of the 
target to spread out and form a corresponding effective surface of 
increased diameter with respect to the flight diameter D.sub.1. 
In the embodiment in accordance with FIGS. 4 and 4a the aforedescribed 
slits 58, which were described in connection with FIGS. 3 and 3a, are 
replaced by means of grooves 56, which extend however over the entire 
length of each element 18. Each groove 56 forms a fracture zone, so that 
upon impacting the target by the corresponding pre-penetrator the breaking 
of the fracture zones causes the guiding of the elements 18 outwardly via 
a sliding on the conical surface 26 of the cone 24 causing a spreading out 
of such elements and achieving the previously described effect. 
In the embodiment of FIGS. 5 and 5a a bundle of rod-shaped third elements 
20 are surrounded in a region of a prepenetrator 10 by a jacket 30 and are 
joined with the region 80 of the main penetrator as will be described 
hereinafter. The nose body 22 which is fixedly supported by the jacket 30 
has again at its rear side a cone 24. The elements 20 bear with their 
rear-side ends 72 against the flat end-face 84 of the region 80 and bear 
with their forward ends 70 against the conical surface 26 of the cone 24. 
Upon impacting a conventionally inclined armor plate of a multi-layered 
target there is again formed a first portion of the penetration channel by 
the nose body 22. The jacket 30 tears or breaks and due to the movement of 
the surface 84 in the direction of firing S the rods 20 are repelled in 
such a way by the conical surface 26 that they move with their forward 
ends 70 having the cutting edges 74, by inter-action with the material of 
the target, to form an effective surface of an enlarged diameter with 
respect to the flight diameter D.sub.1. 
Although the invention is illustrated and described with reference to a 
plurality of embodiments thereof, it is to be expressly understood that it 
is in no way limited to the disclosure of such preferred embodiments but 
is capable of numerous modifications within the scope of the appended 
claims.