ACOUSTIC TRAINING DEVICE AND METHOD FOR SIMULATING AN UNEXPLODED SUBMUNITION

BACKGROUND OF THE INVENTION

The present invention relates generally to Multiple Integrated Laser

Engagement System (MILES) type training devices, and more particularly to an

acoustic training device for simulating the effects of unexploded submunitions in a

tactical engagement simulation system such as the MILES.

The MILES has revolutionized the way in which armies train for combat.

MILES has been fielded with armies of many nations around the world and has

become the international standard against which all other Tactical Engagement

Simulation (TES) systems are measured. For the U.S. Army and Marine Corps,

MILES is the keystone of their opposing force, free-play TES program. It is highly

valued in its ability to accurately assess battle outcomes and to teach soldiers the skills

required to survive in combat and destroy the enemy. With MILES, commanders at

all levels can conduct opposing force free-play tactical engagement simulation training

exercises which duplicate the lethality and stress of actual combat.

The MILES systems uses laser "bullets" to simulate realistically the lethality of

a modern battlefield. Eye-safe Gallium Arsenide (GaAs) laser transmitters, capable

of shooting pulses of coded infrared energy, simulate the effects of live ammunition.

The transmitters are easily attached to and removed from all hand-carried and vehicle-

ounted direct-fire weapons. Detectors located on opposing troops and vehicles

receive coded laser pulses. MILES decoders then determine whether the target was

hit by a weapon which could cause damage (hierarchy of weapons effects) and whether

the laser bullet was accurate enough to cause a casualty. The target vehicles or troops

are made instantly aware of the accuracy of the shot by means of audio alarms and

visual displays, which can indicate either a hit or a near miss.

The coded infrared energy is received by silicon detectors located on the target.

In the case of ground troops, the detectors are installed on webbing material which

resembles the standard-issue load-carrying lift harness. Additional detectors a^e

attached to a web band which fits on standard-issue helmets. For vehicles, the

detectors are mounted on belts which easily attach to the front, rear, and sides. The

detectors provide 360° azimuthal coverage and sufficient elevation coverage to receive

the infrared energy during an air attack. The arriving pulses are sensed by detectors,

amplified, and then compared to a threshold level. If the pulses exceed the threshold,

a single bit is registered in the detection logic. Once a proper arrangement of bits

exists, corresponding to a valid code for a particular weapon, the decoder decides

whether the code is a near miss or a hit. If a hit is registered, a hierarchy decision is

made to determine if this type of weapon can cause a kill against this type of target

and, if so, what the probability of the "kill" might be.

While great success has been enjoyed with weapons that can be aimed, there

has been no convenient or economic way for the military to incorporate grenades,

mines, submunitions and other omnidirectional weaponry into their tactical exercises

using the MILES. Grenades, for instance, tend to rotate during flight and would

require a plurality of laser emitters to simulate a burst. Even were it economical to

provide several laser emitters on each grenade, there is still the possibility that a

player may be obstructed from view and thus unrealistically protected. Similarly,

unexploded submunitions may be laying in tall grass or under a rock when disturbed,

effectively attenuating any possible visual signal.

Copending patent application Serial No. 07/691 ,603, entitled "Apparatus and

Method for Interfacing Indirect-Fire Devices with MILES," uses a predetermined

acoustic signal to simulate an explosion in combination with receiver circuitry sensitive

to the acoustic signal and operatively connected to the existing MILES power supply.

A special feature presently incorporated in the MILES provides for an audible alarm to

be activated upon removal and reinsertion of the MILES power source. This feature

prevents someone from cheating by deactivating his MILES receiver during simulated

combat. When the power source (typically a battery) is reinstalled an audible alarm is

sounded. Consequently, by momentarily removing the MILES power source from the

circuit for a brief instant and then reconnecting it back into the circuit the interfacing

device is able to indicate a "kill" on MILES. This operation is performed when receiver

circuitry detects a predetermined acoustic signal of sufficient amplitude and duration

or can even be a coded acoustic signal. An acoustic signal overcomes the disadvantages

of highly directional laser pulses because of its substantially omnidirectional propagation

characteristics.

Training devices which generate a predetermined acoustic signal of sufficient

amplitude and duration and/or coded acoustic signals are described in copending patent

application Serial No. 07/983,952, entitled "Acoustic Training Device for Use in a

Tactical Engagement System." Particular training devices which simulate a grenade, a

"Bouncing Betty," and a Claymore mine are also described in copending patent

applications Serial Nos. 07/608,923, 07/708,253 and 08/002,367 respectively. All of

these training devices are designed to accurately simulate the effects of a properly

functioning weapon in a tactical engagement simulation.

The present invention, on the other hand, is intended to simulate the effects of

a weapon which has failed to operate after deployment. Many of the submunitions

and M42/M46-type grenades now is use require a mechanical firing pin to impact a

stab detonator in order to initiate the explosives found in these devices. It has been

demonstrated that a firing system relying on a firing pin to strike a stab detonator is

not sensitive to impact angles significantly less than 90° with respect to the target.

Consequently, the battlefield can become littered with armed submunitions that can

then be triggered upon contact by vehicles or personnel walking through the

battlefield.

An example of such a mechanical submunition firing system is exhibited in the

Army M223 fuze, which is employed in M42/M46 submunition grenades. These

grenades, described in U.S. Patent 4,852,496, to Campagnuolo, are stacked atop one

another and are delivered either by artillery projectile or rocket cargo rounds.

In addition to the M42/M46 grenades, there exists a host of other submunitions

used by the Navy, Air Force and Marines. Some of these include the Ml 18 Rockeye

submunition grenade which is launched by aircraft, and the blue series of submunition

grenade which are spherical bomblets also delivered by aircraft.

If any of these submunition grenades do not function after release, either from

aircraft, bomb, rocket or artillery projectile, they will lie upon the ground and remain

live. Any disturbance will then cause them to explode. The disturbance can occur

whenever a vehicle drives over the submunition, or even when a soldier or civilian

picks one up out of curiosity or in an attempt to recover souvenirs. This can be

particularly troublesome in a desert environment where the relatively soft impact

afforded by the sand results in a significant number of "duds."

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an acoustic

training device which simulates the effects of an unexploded submunition in a tactical

engagement simulation system.

It is another object of the present invention to provide an acoustic training

device which simulates the effects of an unexploded submunition in a tactical

engagement simulation system without requiring airborne or artillery delivery.

It is still another object of the present invention to provide an acoustic training

device which simulates the effects of an unexploded submunition in a tactical

engagement simulation system after placement in the field by a referee.

It is yet another object of the present invention to provide an acoustic training

device which resembles in appearance certain submunitions but fails to operate

immediately pursuant to conventional delivery in a tactical engagement simulation

system.

These objects and others not specifically enumerated are accomplished with a

an acoustic training device which resembles a submunition in appearance but houses

sound generating means, a motion sensor, activation and delay circuitry. The sound

generating means include a buzzer which emits an audible signal of a predetermined

frequency and duration which is easily recognized by an audio-equipped tactical

engagement simulation system receiving unit. In order that the submunition training

device may be properly positioned in the battlefield, it is equipped with a delay circuit

which, after arming, delays activation of the motion sensor. After the time delay, any

physical disturbance will complete the circuit causing the buzzer to sound. In one

embodiment the timing means comprises an R-C circuit and comparator which outputs

a signal voltage upon charging of the capacitor during a period related to the time

constant of the circuit. Three types of submunition grenades are also described to

better illustrate how the invention is practice and to represent those submunitions

which are delivered by airplane, artillery or rocket. The present invention is, however,

also intended to encompass other types of weapons which are in real combat delivered

in these way but which fail to detonate.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the present invention will be described with

reference to the accompanying drawings in which:

FIG. 1 is a side view of a prior art Ml 18 Rockeye submunition grenade which

is typically delivered by artillery round;

FIG. 2 is a side view of a prior art blue series, air-delivered spherical bomblet;

FIG. 3 is a side view of a prior art M42/M46 air-delivered submunition

grenade;

FIG. 4 is a cross-sectional view of a prior art M42/M46 air-delivered

submunition grenade employing a stab detonator;

FIG. 5 is a circuit diagram for an acoustic training submunition according to the

present invention;

FIG. 6 is a cross-sectional view of the Ml 18 Rockeye acoustic training device

according to the present invention;

FIG. 7a is a cross-sectional view of a blue series submunition training device

according to the present invention;

FIG. 7b is a cross-sectional view taken along line 7b-7b of FIG. 7a;

FIG. 8 is a cross-sectional view of the M42/M46 submunition training device

according to the present invention;

FIG. 9a is a mechanical motion switch such as that employed in one

embodiment of the present invention;

and FIG. 9b is a multi-directional mercury switch such as that employed in one

embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Conventional prior art submunitions such as those shown in FIGS. 1 , 2 and 3

vary in appearance according to way in which they are deployed and the type of target

they are intended to be used against. A common feature among submunitions is that

they are all delivered en masse to the target from a remote position, either by aircraft,

artillery shell or rocket. Submunitions can be used to destroy an opponents airport

runways or as antipersonnel devices. The Ml 18 Rockeye submunition grenade

depicted in FIG. 1, and the blue series of spherical bomblets shown in FIG. 2 are

delivered by air. The M42/M46 grenade submunition shown in FIG. 3 is typically

delivered by artillery shell.

It has not been possible to realistically simulate the effects of submunition fire

in a tactical engagement simulation since even inert, sound-producing devices could

become deadly if launched by artillery or dropped from a plane. The mass and

velocity of such objects when they impact the target renders them very dangerous.

The present invention, however, simulates the lethality of a submunition which has not

detonated upon impact but remains "live." This has been a real problem in desert

combat where the relative softness of sand can cushion the impact of an incoming

submunition. FIG. 4 shows a cross-section of the M42/M46 grenade submunition

which employs a stab detonator. Such a device can fail to detonate if it impacts at any

angle substantially less than 90° from the target.

Submunitions can be projected into areas controlled by the opposing force.

Thus, while the opposing force may not anticipate a mine threat in their own territory,

they must remain alert at all times for unexploded submunitions, particularly near

typical submunition targets such as airports. Furthermore, many infantrymen are not

familiar with the various types of submunitions because these weapons are typically

deployed by other forces (i.e. artillery or aircraft). Many submunitions, such as the

blue series of spherical bomblets shown in FIG. 2 are relatively small and can be

concealed in tall grass or covered by sand. Subsequently, there is a need to

incorporate unexploded submunition training devices into tactical engagement

simulations so that soldiers may become aware of these hazards and develop strategies

to combat them.

The present invention simulates the effects of an unexploded submunition

without the danger involved in conventional submunition delivery. A referee locates

a position for the training submunition in the training battle zone, pulls out a pin from

an arming switch (note that a real submunition does not have such an arming pin and

switch), and places the submunition down. The switch closes and allows voltage from

a battery or some other type of power source to activate a first timer. This timer can

be preset for any desired "time-out" corresponding to the time reasonably needed by

a referee to position the training .device and subsequently evacuate the immediate area

surrounding the training device. Presently, a time-out of about 20 seconds is used.

During this delay a capacitor in the firing circuit is charged. If left undisturbed, the

grenade submunition will lay in this state for several days (i.e. until the charge

dissipates). However, if the submunition is picked up or otherwise physically disturbed

by one of the players, a motion switch senses the disturbance and sends a signal which

can fire a flash bulb, indicating function. At the same time, or alternatively, an

electronic buzzer is activated through a second timer which causes it to sound for a

predetermined period of time. The audible signal, and flash if it is employed, indicate

to the soldier and to an audio-equipped tactical engagement simulation system, that

an unexploded submunition has been disturbed and that the soldier would be a

casualty had the device been real. The length and duration of the audible signal are

such that it can be distinguished from other battlefield noises at ranges corresponding

to the lethality of a real submunition. The audible signal may also be modulated as

described in copending patent application Serial No. 07/983,952.

FIG. 5 is an electrical schematic of the circuit 100 which is common to all the

submunition training devices described herein. The general features of the circuit

include a power source 101 which is typically a battery, the size of which depends on

the submunition being simulated (e.g. cylindrical 6V lithium for the M42/M46 and

blue series spherical bomblet, and rectangular 9V alkaline for the Ml 18 trainer); an

arming switch 103 which includes some type of pin or external control; a first timing

circuit 105 for defining a time-out period during which the submunition is placed and

armed; a motion sensing switch 107 which closes when disturbed; a sound generating

circuit 109 and an optional flash bulb 1 11 to enhance the realism of the event.

When the pin is pulled from phone-type switch 103, capacitor 115 begins to

charge. After about 20 seconds, capacitor 1 15 charges to about 0.75 Vcc (the voltage

source 101), which is enough to trigger comparator 121 to go "high." The output signal

of comparator 121 effectively renders the submunition training device "live." The

charging time can be adjusted by changing the R-C time constant of a first circuit

comprising a resistor 113 and capacitor 115 or the comparator trigger level related to

the values of resistors 117 and 1 19, the voltage between which provides one input to

the comparator 121. Of course, other timing means may be devised for achieving an

appropriate "time-out" period, but this circuit is relatively straightforward, rugged and

dependable.

Once armed, any small movement or vibration will trigger inertia switch 107,

which is either a mechanical motion switch 500 as illustrated in FIG. 8 or a multi-

irectional mercury switch 600 as shown in FIG. 9. A suitable switch for present

purposes is the model 2008-4 mercury vibration/motion switch produced by Signal

Systems International or Lavallette, New Jersey. The model 2008-4 is only 0.325" in

diameter and 0.38" long, thus being easily packaged in a submunition-like housing

along with other electrical and electro-mechanical components of the present

invention. Triggering of such an inertia switch 107 supplies voltage to a second timer

circuit 123 which drives the buzzer 125 and optional flashbulb 11 1. The frequency,

duration and means for modulating the audible signal are discussed in copending

patent application Serial No. 07/983,952. Currently, MILES-compatible training

submunitions emit a 70-80 dB signal at 3750 Hz for about 4 seconds. A pulse-

modulation rate of 50-100 milliseconds may also be implemented where receiver

circuitry is designed to detect modulated signals. The amplitude of the signal ensures

an appropriate "kill radius" within which the training device will cause an audio-

adapted tactical engagement system to indicate a casualty. The frequency and

modulation scheme have been chosen to distinguish over ambient battlefield noises.

The preferred flashbulb 1 11 is a common type camera flashbulb such as the Sylvania

Blue Dot, although an LED or Xenon flash beacon would also suffice.

Referring now to FIG. 6, an Ml 18 Rockeye training submunition 200 is shown

in cross-section so that the arrangement of internal elements may be discerned. The

housing is made up of two main components. These are a tubular casing 201 which

is cup-like and typically aluminum, and a clear or translucent plastic cover 205 which

threads onto the tubular casing to form a substantially cylindrical body. A nose cone

203 protrudes from the clear plastic cover, and may be integrally formed of plastic

with an aluminum sheathing. At the rear of the tubular casing 201 a smaller housing

207 with an integral acoustic horn 21 1 protrudes rearward. A plurality of fins 209

extend from the rear housing 207 to accurately mimic the actual device.

Unlike the true Ml 18 Rockeye submunition, however, the training device 200

is provided with an external ring and pull pin 213 which is inserted into an arming

switch 215 affixed to the inside of the tubular casing 201. The arming switch 215 is

a phone type switch with a nonintegral pin inserted between contacts. The transducer

225 is located just ahead of an opening in the base of the tubular casing 201 and the

mouth of the acoustical horn 21 1 which is machined into the rear housing 207. A 9-V

alkaline battery is suspended within the cylindrical body formed by the tubular casing

201 and plastic cover 205. A flashbulb 227 sits in front of the battery 217 so that when

the plastic cover 205 is removed, both the flashbulb 227 and the battery 217 are

accessible. The motion switch 221 is also affixed internally to the housing 201 so that

it moves with the whole device. The tubular casing 201 also houses the delay circuit

219 which controls the "time-out" period during which a referee may place the

submunition training device 200 and leave the area, and the timer circuit 223 which

fires the flashbulb 227 and drives the transducer 225. Because the flashbulb 227 is

located forward of the tubular casing 201 and within the plastic cover 205, the flash

of light it creates is visible to those soldiers who inadvertently set-off the device.

Two cross-sectional views of a blue series spherical bomblet submunition trainer

300 are shown in FIGS. 7a and 7b respectively. The housing 301 of this training

submunition is a hollow blue-tinted, translucent urethan sphere resembling in size

and features the actual blue series of submunitions. It is preferably formed in two

hemispherical pieces and joined by machine screws and threaded inserts (not shown).

13

SUBSTITUTE SHEET (RULE 26.

Like the Ml 18 Rockeye training device 200, the blue series submumtion training

device 300 is provided with a pull ring and pin assembly 303 which is inserted between

contacts in an arming switch 305. The blue series of submunition are smaller than the

Ml 18 Rockeye housing and thus require a smaller power source 307, such as a 6V

lithium of the type commonly used in portable cameras.

The M42/M46 grenade submunition training device 400 also employs the

smaller power source 41 1 which is located inside the lower half of a metallic tubular

housing 401. Like the Ml 18 Rockeye submunition training device 200, however, the

upper half of the housing 401 can be formed from a translucent or clear plastic and

threaded to the lower half. In such a configuration the flashbulb 421 is located in the

upper half so that the flash is visible to troops. In addition to all the foregoing

elements described in connection with the M 118 Rockeye submunition training device

200 and the blue series submunition training device 300, the M42/M46 submunition

training device 400 is also provided with a dummy fuze 405 and ribbon attachment 403

which mimic the actual M42/M46 for realism. The real M42/M46 submunition as

shown in FIGS. 3 and 4 is provided with a ribbon which allows a pin to unscrew in

flight. A spring then pushes the detonator into alignment with a shape charge. Impact

at angles near 90° results in detonation of the real weapon.

While there has been described and illustrated specific embodiments of the

invention, it will be obvious that various changes, modifications and additions can be

made herein without departing from the field of the invention which should be limited

only by the scope of the appended claims.