Pop-up Antihelo Mine

Abstract

A pop-up mine, anchored to the bottom and remaining under the surface of a ody of water for destroying ASW and sonar dunking helicopters. The mine case includes an outer skin comprising fragment projectiles bonded to an explosive sheet. Deployed by a submarine, an anchor separates and sinks to the bottom, paying out cable to leave the mine close to the surface. A hydrophone, discriminating for detecting helicopters, activates a cable cutter and a rocket motor. The mine case pops to the surface, is lifted by the rocket to a predetermined altitude, and explodes to disperse the metal fragments, thus disabling the helicopter.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to underwater weapons systems such as mines and torpedoes and more particularly to a pop-up mine that detects and destroys ASW helicopters hovering over the water having the intent to detect and destroy a submarine.

At present there is no known offensive weapon that may be effectively used by a submarine to attack an Anti-Submarine Warfare helicopter or airplane. The submarine may only defensively hide by running away or diving deep to avoid detection and subsequent attack. The use of the deck gun of the older submarines required that the submarine expose itself by surfacing to fire on the aircraft.

The instant invention provides an offensive weapon for a submarine to use effectively against ASW aircraft that is triggered by the attacking aircraft.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide an effective sea-to-air offensive weapon.

Another object of the instant invention is to provide a submarine with an effective offensive weapon against ASW aircraft.

A further object of the instant invention is to provide a mine that is concealed under the sea surface which is released and lifted to an altitude to disable an aircraft.

A still further object of the present invention is to provide a mine that is activated by and will disable the attacking aircraft.

Briefly, these and other objects of the present invention are attained by a pop-up mine concealed below the water's surface that detects and destroys ASW helicopters hovering over the water with the intent to locate and destroy a submarine. The mine is deployed by a submarine, and subsequently releases a separable anchor which sinks to the bottom leaving the mine case concealed just below the surface of the water. A discriminating hydrophone, on the mine case, picks up the low frequency noise created by the downwash of a helicopter rotor when it is searching or "dunking" to listen for submarines. Upon hearing a helicopter, the hydrophone activates an anchor cable cutter and a rocket motor, causing the mine case to pop to the surface and be lifted to a predetermined altitude. The outer skin of the mine, composed of metal fragments bonded to an explosive sheet, is caused to explode, releasing flack projectiles which disable the helicopter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention and the many attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawing wherein:

FIG. 1 is a pictorial sequential view of a pop-up mine planted and later activated;

FIG. 2 is a side view partially cut away showing the details of the pop-up mine;

FIG. 3 is a schematic diagram of the electrical firing system; and

FIG. 4 shows the anchor cable deployment system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein like reference numerals designate corresponding parts throughout the several views, there is shown generally in FIG. 1 a pop-up mine 10 in an air-sea enviroment 12. A submarine 14 is shown as having just planted the mine system by expelling it out a garbage ejector or torpedo tube port 16 as shown in position A.

After planting as shown in position B the pop-up mine 10 separates, leaving a mine case 18 floating concealed under the surface, and a separable anchor 20 sinks to the bottom paying out a mooring line 22. In position C the mine is activated by cutting the mooring line 22 and energizing a rocket motor to pop to the surface (position D) and ascend to a height to disable a hovering and dunking ASW helicopter 24 (position E).

Referring now to FIG. 2, the mine case 18, anchor 20, and mooring line 22 are shown in detail. The mine case 18 comprises a pair of hemispheres 26 of thin spun aluminum or the like overlaid with a plurality of sheets 28 of "Starrflak." "Starrflak" is a Naval Ordnance Laboratory invention comprising a grid of one-fourth inch square metal fragments bonded to an explosive sheet. The "Starrflak" may be overlaid with cheesecloth laminated on with an epoxy resin or the like. The hemispheres are secured together along flanges 30 using suitable fasteners and sealed with a rubber gasket 32. A cable 34 from a battery and firing assembly 36 (to be discussed hereinafter) inside the case, exits through a stuffing gland 38 and is electrically connected to a detonator 40 on each hemisphere 26 and attached to the "Starrflak" by an adhesive or the like. Further, the cable 34 is electrically connected to a rocket motor and mooring line cutter initiator squib assembly 42.

Alongside the mooring line cutter and inside the case is a rocket motor 44 affixed to a mounting plate 46 sealed to the bottom of the case. The mounting plate contains a plurality of ports 48 through which the motor propulsive exhaust exits. The ports are sealingly closed by a port plate 50 secured by shear screws 52.

On top of the mine case 18 are flush-mounted hydrostats 54 which act as arming switches and a hydrophone 56 for activating the mine. Hydrophone 56 is electrically connected via a cable 58 to preamp 60 located at the bottom of the mine case, along with other electronics circuitry.

Referring now to FIG. 3 the electronic circuit contained in the battery and firing assembly 36 is shown in detail. The hydrophone 56 is electrically connected to an electronic filter 62 which passes only the desired low frequency band produced by the downwash of a helicopter rotor. The filter's output is fed via cable 58 to the signal preamplifier 60 which produces a usable output. This output is fed to an electronic switch 64 capable of initiating the rocket motor and mooring line cutter initiator squib 42. The signal preamp 60 derives its power from a battery 66 electrically connected thereto.

Battery 66 is shown electrically isolated and not producing power to the circuits due to a plurality of hydrostatic arming switches 54 shown in their normally-open position. When closed, these arming switches 54 carry current to the hydrophone preamp 60, the electronic switch 64 and thence to the initiator 42, and a firing circuit comprising a charging resistor 68, and a firing capacitor 70. An apogee switch 72 of the inertial type connects the charging circuit to the detonators 40.

FIG. 4 shows mooring line 22 wound upon a spool 78 suitably supported for rotation. A pawling mechanism 80, positioned adjacent spool 78, controls the rotation of the spool to pay out line 22. Hydrostats 82 regulate the operation of the pawling mechanism 80 to control the mooring depth of mine case 18.

In operation, the pop-up anti-helo mine 10 is planted (View A) by the very submarine 14 that the ASW hovering helicpoter 24 is attempting to locate, by deploying the mine out the garbage ejector 16. After ejection, the anchor 20 separates from the mine case 18, paying out mooring line 22, and sinks to the bottom (View B) keeping the case submerged. When the anchor sinks below a predetermined depth, the mooring line spool 78 pawls and the anchor continues to the bottom. Pawling occurs a distance from the bottom equal to the desired case mooring depth, and is controlled by hydrostats 82 or the like.

Electrical arming of the mine occurs after ejection from the submarine and during the anchoring phase, allowing the submarine to cruise to a safe standoff distance. Referring to FIG. 3 arming occurs by water pressure actuating the hydrostatic switches 54 causing power from battery 66 to be applied to the hydrophone preamplifier 60, the arming circuit resistor 68 and capacitor 70 charging it and the electronic switch 64.

The pop-up mine system now waits in position (FIG. 1, View B) for a ASW hovering, dunking helicopter. When a helicopter 24 nears the location, the hydrophone 56 picks up the low-frequency sound and pressure waves created by the rotor downwash. The electrical output of the hydrophone 56 is fed through filter 62 which passes only low frequency signals, and cancels high frequency sound emitted from passing shipping, ambient noise, sonar and marine life. The low frequency signal is fed via the cable 58 to the hydrophone preamplified 60. If the output is of sufficient magnitude, the electronic switch 64, such as a relay or silicon controlled rectifier, will activate applying a current to the rocket motor and mooring line cutter squib 42.

When the squib fires, the mooring line 22 is severed by squib 42 and the rocket motor 44 ignited, blowing out the jet port plates 50, allowing the mine case 18 to pop to the surface of the water and be lifted by the rocket into the air to an altitude of 10 feet to 150 feet depending on the rocket used. At the apogee, the inertia or velocity discriminator apogee switch 72 closes, dumping the charge in the firing capacitor 70 into the detonators 40, detonating the "Starrflak" and spraying the area with metal fragments to disable the ASW helicopter.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A pop-up, anti-helo mine system adapted to be moored below the water's surface and to be propelled into the air upon detection of an air target comprising:

a mine case adapted to be moored below the water's surface;

an explosive attached to said mine case;

an anchor assembly releasably connected to said mine case;

a mooring line connecting said anchor assembly to said mine case;

means for paying out said mooring line from said anchor assembly;

an acoustic detection device provided in said mine case to detect target signals above the water's surface;

propulsion means for propelling said mine case out of the water; and

control means responsive to said acoustic detection device to release said anchor assembly and to activate said propulsion means.

2. The pop-up, anti-helo mine system of claim 1, wherein said propulsion means comprises

a solid rocket motor for propelling said mine to a predetermined altitude above the water's surface.

3. The pop-up, anti-helo mine system of claim 2, wherein said acoustic detection device comprises:

a hydrophone capable of receiving sounds in water and converting them to electrical impulses;

an electrical filter connected to said hydrophone for passing only low frequencies produced by a helicopter; and

a preamplifier for amplifying the impulses to a magnitude capable of activating the mine.

4. The pop-up, anti-helo mine system of claim 3 wherein said control means comprises

a rocket motor and cable cutter initiator squib electrically connected to said acoustic detection device for releasing said mooring line and igniting said rocket motor when said hydrophone detects a helicopter.

5. The pop-up, anti-helo mine system of claim 4 wherein said explosive comprises:

a metal sheet segmented to produce a plurality of metal fragments; and

an explosive sheet bonded to said metal sheet,

whereby the resulting laminant forms the outer shell of said mine case.

6. The pop-up, anti-helo mine system of claim 4 further comprising:

a firing circuit including a chargeable capacitor and resistor;

at least one electro-responsive detonator in contact with said explosive; and

an apogee switch for coupling said firing circuit to said electro-responsive detonator to initiate said detonator and consequently said explosive.

7. The pop-up, anti-helo mine system of claim 6 further comprising

a plurality of hydrostatically operated arming switches for connecting a source of electrical power to said acoustic detection device, said initiator squib, and said firing circuit after deploying and anchoring.

8. The pop-up, anti-helo mine system of claim 7 wherein said means for paying out mooring line comprises:

a spool for winding said anchor line; and

a pawling mechanism coacting with said spool for releasing and stopping said spool.