Shaped charge projectile system

This invention provides a subcaliber projectile which is launched from a full bore projectile having a shaped charge warhead prior to impact with the target. The subcaliber projectile is tethered to the full bore projectile by means of a fine electrical cable of fixed length which serves as the communication link between the two projectiles with the length of the cable determining the fuzing standoff distance. The ballistic coefficient of the subcaliber projectile is made such that the subcaliber projectile always flies ahead of the full bore projectile.

BACKGROUND OF THE INVENTION 
1. Field of Art 
This invention relates to providing ignition to a shaped charge projectile 
at an appropriate stand-off distance from the target. 
2. Prior Art 
Mechanisms for providing stand-off for a shaped charge projectile are well 
known in the prior art. A rigid forward extension which places a contact 
mechanism, such as a piezoelectric crystal, a distance forward of the 
shaped charge is shown in U.S. Pat. No. 3,416,449, issued Dec. 17, 1968, 
to J. Brothers; U.S. Pat. No. 3,474,731, issued Oct. 28, 1969, to F. R. 
Thomanek; U.S. Pat. No. 3,613,585, issued Oct. 19, 1971, to S. Dubroff; 
U.S. Pat. No. 3,760,731, issued Sept. 25, 1973, to G. E. Gaughan etal; 
U.S. Pat. No. 3,906,860, issued Sept. 23, 1975, to W. H. Johns and my U.S. 
Pat. No. 4,291,627, issued Sept. 29, 1981. 
A bellows structure which is inflated during flight, by a not disclosed 
timing mechanism, to place a contact mechanism a distance forward of the 
shaped charge is shown in U.S. Pat. No. 4,181,079, issued Jan. 1, 1980, to 
H. Klier et al. A coaxial tube structure which is extended during flight 
by airdrag retarding the outermost tube, but not in in a shaped charge 
application, is shown in U.S. Pat. No. 3,677,179, issued July 18, 1972, to 
L. A. Potteiger. 
Mechanisms for instructing fuzes, particularly timing circuits, during 
flight as shown in my U.S. Pat. No. 3,844,217, issued Oct. 29, 1974 and in 
others, including U.S. Pat. No. 4,291,627. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a mechanism for an extended 
fuzing stand-off for a shaped charge warhead. 
A feature of this invention is the provision of a subcaliber projectile 
which is launched from a full bore projectile having a shaped charge 
warhead prior to impact with the target. The subcaliber projectile is 
tethered to the full bore projectile by means of a fine electrical cable 
of fixed length which serves as the communication link between the two 
projectiles with the length of the cable determining the fuzing standoff 
distance. The ballistic coefficient of the subcaliber projectile is made 
such that the subcaliber projectile always flies ahead of the full bore 
projectile.

DESCRIPTION OF THE INVENTION 
The invention is based upon the premise that two projectiles of 
substantially different dimensions can be made to have nearly identical 
aeroballistic characteristics, and as such, can be made to fly matched 
ballistic trajectories. A further aeroballistic refinement is then made in 
the smaller of the two projectiles to allow it to fly a slightly faster 
trajectory than the larger projectile. If then, the two projectiles are 
gun launched together, where the smaller projectile is carried by the 
larger projectile and then the two are made to separate just prior to 
target impact, the smaller projectile, with its better ballistic 
characteristics, will fly slightly ahead of the larger projectile from 
which it is launched. If further, the two projectiles are tethered 
together by means of a thin, short length wire, they will fly to the 
target with the wire taut, representing a fixed separation between the two 
projectiles. If now the lead projectile carries a piezoelectric crystal in 
its nose to serve as a crush up sensor, and the wire connecting the two 
projectiles is designed to carry the electrical impulse from this crystal 
to a fuze in the "follow" projectile, then target impact by the lead 
projectile will cause the shaped charge warhead in the "follow" projectile 
to function at a target standoff determined by the length of the 
connecting wire cable. In this manner it is possible to precisely fix the 
target standoff distance to allow optimum warhead effectiveness. 
FIG. 1 shows the overall weapon system including a fire control system 10 
having a range finder and which may be located on the gun turret or the 
vehicle and which is coupled to a RF data link transmitter 12 having a 
transmit antenna 14 which transmits fuze time setting data to the inflight 
projectile system 16. 
FIG. 2 shows the inflight projectile system including a full bore 
projectile 20 carrying a subcaliber projectile or probe 22 coupled by a 
fine, two conductor wire 24 to a base fuze 26 which is disposed behind a 
shaped charge 28. A receive antenna 30 is coupled to a receiver and fuze 
timer 32 whose output is coupled by a conductor 34 to a pyrotechnic gas 
generator or dimple motor 36 having an electrical initiator 37 which is 
able to eject the probe 22 from the recess 38 in which it is initially 
disposed. 
The transmitter and receiver electronics are similar to those shown in U.S. 
Pat. No. 3,844,217, to which reference for details should be made. The 
time set into the receiver and fuze timer 32 is its exact instant along 
the trajectory of the projectile 20 that the probe 22 is to be deployed. 
At that time, the output of the fuze timer causes the motor 36 to eject 
the probe 22. This time is a few hundred milliseconds prior to impact with 
the target. 
As shown in FIG. 4, the opening of the recess 38 is sealed against the 
environment by means of a thin metal foil 39 which is torn away as the 
probe is ejected. The insulated cable 24 connecting the projectile base 
fuze 26 to the probe 22 provides the communication link between the probe 
22 and the projectile 20. The fuze conventionally contains a set-back 
generator 40, which may be of the type shown in my U.S. Pat. No. 
4,091,733, issued May 30, 1978, a diode 42, an inertial switch (trembler) 
44, a capacitor 52 and a detonator 54. An ogival crush-up switch 46, which 
may be of the type shown in U.S. Pat. No. 4,291,627, is in the projectile 
20 and in parallel with the inertial switch (trembler) 44 in the base fuze 
26, and closure of any of these switches will cause the warhead to 
function. 
A piezoelectric crystal 48 is encased within the probe and a series diode 
50 is added within the fuze 26 as shown in FIG. 6. The probe will function 
the fuze 26 when it has impacted a target and the crystal 48 has generated 
a high voltage spike which passes through the blocking diode 50, and in 
discharging the fuze capacitor 52, functions the fuze detonator 54. An 
inadvertent short circuit of the connecting cable from the probe to the 
projectile fuze will not cause the warhead to function. This feature 
prevents a premature function of the round in the event the connecting 
cable is damaged (shorted), by whatever means, prior to target impact. 
As shown in FIG. 5, the wire 24 is stowed in a cavity behind the probe and 
is extracted from the cavity as the probe is accelerated forward of the 
projectile. The last few inches of wire is passed through a drag brake 
(snubber) 56 to limit tension on the line as the probe approaches its 
fully extended position. 
The projectile 20 may be a 105 mm, fin stabilized, high length-to-diameter 
ratio dart. The projectile 20 decelerates more rapidly than the probe 22 
due to its higher drag. Fired at identical velocities at the same instant, 
the probe will always reach the target before the projectile.