Low cost rapid mine clearance system

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to a method and system to clear mines underwater. More particularly, this invention relates to dropping tag particles across an area of the ocean and deploying an unmanned underwater vehicle to locate and neutralize mines that have a number of tag particles on them.

(2) Description of the Prior Art

Clearing underwater mines is a complicated, costly endeavor. The per-mine-killed cost of a robust system is often much greater than the cost of each mine. This unbalance is unacceptable since mass produced underwater mines could limit a navy's ability to operate in vast near-shore areas. The state of the art in mine clearance has relied on using sophisticated unmanned underwater vehicles (UUVs) each having a single warhead. The state of the art UUV locates an underwater mine, maneuvers in close proximity to it, and detonates the warhead. The underwater explosion is successful in the neutralization of a single mine if the UUV is positioned correctly. However, there are several shortcomings to this state of the art approach. The use of an underwater explosion precludes any element of stealth in the clearance of a single mine. This can be a major tactical shortcoming of the current methodology. Another is that the effectiveness of this technique relies on very accurate placement of the detonating charge to at least close proximity to the mine. Consequently, attaining this proximity comes at the considerable cost of a complex targeting system, complex vehicle control systems, and a complex vehicle to house such systems.

Furthermore, the contemporary UUV is often guided by communication links to a surface or underwater platform and requires significant involvement of crew resources to manage the launching, targeting and recovery of the UUV. The time to clear a well-mined area can be excessive and during the mine clearing operation, the naval assets managing and in support of the task may be easily targeted. The fact that simple floating mines may be mass-produced a very low cost produces yet another severe obstacle for an expensive system that can clear only a single mine. The problems associated with targeting mines in shallow water are also a concern, for examples, poor acoustics and water clarity limit traditional targeting systems.

In addition to the existing systems that incorporate at least one UUV in some navies, other devices such as that disclosed in U.S. Pat. No. 6,032,567 have been documented. In an operational sense they too have similar shortcomings regarding targeting and destruction of underwater mines. An additional problem these devices share is their limited effectiveness due to rapid dissipation of explosions or projectiles in an underwater environment.

Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for a method and apparatus to tag, locate, identify, and neutralize mines.

SUMMARY OF THE INVENTION

The first object of the invention is to provide a means to identify underwater mines.

Another object is to provide a method and apparatus to position a vehicle in proximity to an underwater mine.

Another object is to provide a method and apparatus to target an underwater mine.

Another object is to provide means to target an underwater mine in an unfavorable acoustic or visual environment.

Another object is to provide a robust means to destroy underwater mines.

Another object of the invention is to provide a system having the capability to neutralize several underwater mines with a single system during a single mission.

Another object of the invention is to provide a method and apparatus to tag and target mines quickly over a wide area.

Another object is to provide a method and apparatus to tag a plurality of mines from a single airborne platform.

Another object is to provide a method and apparatus to tag mines in a covert fashion.

Another object is to provide a method and apparatus is to tag mines for a finite duration of time.

Another object of the invention is to provide a method and apparatus to quickly identify tagged underwater mines.

Another object of the invention is to provide a method and apparatus for the rapid destruction of tagged mines.

Another object is to provide a method and apparatus to destroy a number of mines in a covert fashion by a single UUV platform.

Another object is to provide a cost effective means to destroy mines from long range.

Another object of the invention is to provide a mine clearance platform that may operate in its own self-defense.

Another object of the invention is to provide a method and apparatus to destroy underwater mines located at different depths in the water.

Another object is to provide a mine clearance system that may operate autonomously or with operator control.

Another object is to provide means to identify more mines than existing systems do.

These and other objects of the invention will become more readily apparent from the ensuing specification when taken in conjunction with the appended claims.

Accordingly, the present invention is a method and apparatus to clear mines underwater. Tag particles are dropped from an aircraft over a wide area of the ocean to sink and stick on submerged mines. An unmanned underwater vehicle (UUV) platform locates and neutralizes mines that have tag particles on them. The platform has an elongate cylindrical-shaped pressure hull that could be launched from a torpedo tube, for example. The tag particles each contain a gas volume dimensioned to resonate with impinging acoustic energy and create reflected portions of the impinging acoustic energy from a targeted mine. The UUV platform has a sonar system provided with at least one transducer to project the acoustic energy through the ambient water. At least one hydrophone transducer in the sonar system receives the reflected portions of the projected acoustic energy to locate a targeted mine to enable its destruction by high-energy supercavitating projectiles fired from the UUV platform. All tag particles dissolve after a period of time to provide no discernable traces of a mine hunting operation.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention and many of the attendant advantages thereto will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein like reference numerals refer to like parts and wherein:

FIG. 1

is a schematic view of the mine clearance system of this invention;

FIG. 2

is a schematic view showing details of the UUV;

FIG. 3A

schematically shows a tag particle while it is dry before deployment in water;

FIG. 3B

schematically shows a tag particle when it is wetted at a time t=0 as it is dropped into water;

FIG. 3C

schematically shows a tag particle after a time past time t=0 upon dissolution of a water soluble acoustically transparent cover and adhesive; and

FIG. 4

schematically depicts the UUV platform engaging a tagged mine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to

FIGS. 1 and 2

of the drawings, mine clearance system

10

has an unmanned underwater vehicle (UUV) platform

20

deployed from a remote site

11

. UUV platform

20

operates in concert with tag particles

40

to neutralize targets, such as a mine

50

or field of mines beneath the surface of water

60

. Mines typically are buoyant and are held in place by a tether

50

A. UUV platform

20

and tag particles

40

of mine clearance system

10

synergistically cooperate to improve kill ratios of mines

50

as compared to more costly, contemporary systems.

FIG. 1

shows an aircraft

70

dropping of tag particles

40

and UUV platform

20

positioned in water

60

. It is to be understood, however, that tag particles

40

of this invention are more likely to be dropped from or sown by aircraft

70

across a wide area, or region suspected of being mined prior to deployment of UUV platform

20

. Aircraft

70

may be a conventional fixed wing aircraft, drone aircraft, or helicopters. Surface vessels may be used to disperse tag particles

40

. Some particle disbursement methods may be more desirable than others for avoiding unwanted attention.

UUV platform

20

can have an elongate cylindrical-shaped pressure hull

21

enabling its launch from a tube, such as a torpedo tube at remote site

11

. Hull

21

is made from metal or synthetic materials having sufficient strength for bearing ambient water pressure. Other components to be described herein also are substantially built and sealed to reduce the effects of ambient water pressure, and these components and interconnections are made according to acceptable and established marine engineering principles for successful operation while UUV platform

20

hunts and destroys mines

50

at depths.

At least one propeller

22

can be located aft on hull

21

and is connected to an appropriate motor and power supply (not shown) to propel UUV platform

20

. The power supply can additionally be used to power communication, sensor, processing, and activation modules in UUV platform

20

. An optical fiber

23

can be deployed from a spool of such fiber in hull

21

to extend from an extension

23

A of UUV platform

20

to remote site

11

. Optical fiber

23

will function as an optical communication link. This link will transmit control signals to UUV platform

20

from remote site

11

and data signals from UUV platform

20

to remote site

11

.

UUV platform

20

has modular systems on board to assure responsive buoyancy and propulsion, auto pilot and guidance including optical, acoustic and other navigation systems as well as Global Positioning System (GPS) compatible systems. Such systems are well established in the art and can be selected and tailored for incorporation into UUV platform

20

by one skilled in the art. UUV platform

20

additionally has an acoustic sensor system, or sonar system

24

schematically depicted as being located near the nose portion of UUV platform

20

. As shown in

FIG. 4

, this system has at least one acoustic transducer to project acoustic energy

24

A through ambient water

60

and at least one acoustic transducer (hydrophone) to receive reflected portions

24

B of the projected acoustic energy from mines

50

. Acoustic energy

24

A can be projected in response to control signals sent over optical fiber

23

from remote site

11

, and the information concerning the reflected acoustic energy

24

B can be transmitted over optical fiber

23

to site

11

.

The acoustic transducers project and receive acoustic energy at high frequencies to provide meaningful imaging from reflected acoustic energy from the tag particles on the mines

50

to identify the mines. The high frequencies of the projected and reflected acoustic energy

24

A and

24

B may typically be in the range, for example, from between 100 KHZ and 2 MHZ for acceptable resolution. These typical frequencies of sonar system

24

, are intended to be exemplary and not intended to be limiting, and this energy is used to detect tag particles

40

as explained below.

UUV platform

20

has two underwater projectile systems

25

A and

25

B. Projectile systems

25

A and

25

B fire supercavitating projectiles

25

C (FIG.

4

). Supercavitating projectiles

25

C may be bullet-like missiles propelled from conventional cartridges by detonating propellants or may be rocket-like projectiles propelled by exhaust gases produced from burning rocket propellants from launch rack-like structure in UUV platform

20

. In either case, projectiles

25

C are designed to be supercavitating assuring sufficiently high velocity passage through the water and sufficient kinetic energy to destroy or otherwise neutralize a targeted mine

50

.

Projectile system

25

A is oriented to shoot supercavitating projectiles

25

C into its targeted mine

50

when the designated mine

50

is directly in front of, or aligned with the longitudinal axis of UUV platform

20

. Projectile system

25

B is oriented to shoot supercavitating projectiles

25

C into its targeted mine

50

when the designated mine

50

is at right angles to the longitudinal axis of UUV platform

20

. Projectile systems

25

A and

25

B may have magazines of supercavitating projectiles

25

C fired from firearm-like cartridges or launched from stacked rocket launching racks so that systems

25

A and

25

B are therefore, capable of firing multiple rounds in bursts or as single shots. Bursts of supercavitating projectiles, such as shown in

FIG. 4

might be used to facilitate the destruction of not only mines

50

but also moving targets, such as a threatening hostile undersea craft or incoming missiles. In addition, firing bursts of projectiles

25

C from projectile systems

25

A and

25

B may help reduce the necessity of having an elegant targeting solution.

A flash-suppressing muzzle can be provided for projectile systems

25

A and

25

B to reduce the possibility of detection of their firing. Projectile systems

25

A and

25

B can also have laser-targeting systems (not shown) that may include a laser designator aligned with projectile systems

25

A and/or

25

B to illuminate a target. In addition laser-targeting systems for systems

25

A and

25

B could be responsive to laser designation from another UUV platform that has a laser designator to kill an illuminated mine

50

.

UUV platform

20

may additionally be provided with a magnetic detection and fuzing device

26

that can use magnetic sensing and homing to detect mine

50

and aim and align underwater projectile systems

25

A and

25

B for destruction of the targeted mine

50

. Device

26

might additionally be used to identify and home in on threatening countermeasures or hidden magnetic objects that otherwise might not be discovered.

UUV platform

20

is stabilized for steering, station keeping, and accurate firing of supercavitating projectiles

25

C from projectile systems

25

A and

25

B by pop-out wings

27

and control surfaces

29

. Pop-out wings

27

are pivotally rotated from slot-shaped bays

28

in UUV platform

20

. Fore, or aft fin-like control surfaces

29

are outwardly displaced from UUV platform

20

to a fixed position after launch from the tube at remote site

11

. Wings

27

and control surfaces

29

may be selectably rotated by suitable mechanisms responsive to control signals for steering and maintaining the attitude of UUV platform during transit to mine

50

and/or during firing of projectiles

25

C. Wings

27

and control surfaces

28

may also have controllable flaps to further refine control.

Maneuvering and stabilizing UUV platform

20

, particularly during firing, can further be augmented by a vectored thrust control system

30

. Vectored thrust control system

30

has a number of radially outwardly pointing nozzles

30

a

that direct selective high pressure flows of fluid outwardly to hold UUV platform

20

steady and allow firing of projectiles

25

C at targeted mines

50

, or other targets, at any orientation.

An underwater camera system

31

is used to assist transit to the targeted mines and to assist in the final targeting of mines

50

. Camera system

31

is mounted forward on UUV platform

20

and may have a source of visible or non-visible radiation, depending on the type of camera used. During progression to a targeted mine

50

, the radiation source can radiate energy on not only the area in front of UUV platform

20

but also marine topography at the bottom of ambient water

60

. The high level of radiation enables a sensor package, e.g., camera, radiation detector, etc., in camera system

31

to receive reflected portions of the radiation and provide data signals representative of ambient features and mines

50

. These data signals are processed in processing, logic, and relay modules in UUV platform

20

and relayed remote site

11

. UUV platform

20

, therefore, has another capability for avoiding obstacles, following a series of known undersea features and/or locating and identifying mine

50

. Because UUV platform

20

may be submerged to a considerable depth in water

60

, the radiation associated with camera system

31

is hidden from possibly unfriendly observers above water

60

as data is gathered.

A conventional warhead

32

can be included in UUV platform

20

to destroy a high value target or hardened target. Warhead

32

might also be detonated to destroy or scuttle UUV platform

20

when such action is desired.

Responsive displacements of propeller

22

, wings

27

control surfaces

28

and vectored control system

30

via modules in UUV platform

20

steer and guide UUV platform

20

to the vicinity of one or more mines

50

. The processing and logic modules for accomplishing this are well known in the art and are included in UUV platform

20

where they process incoming data signals from sonar system

24

and camera system

31

. Furthermore, the processing, logic and transceiver modules in UUV platform

20

are also responsive to command signals received from remote site

11

over optical fiber

23

. These modules can be responsive to acoustic command signals received through ambient water

60

from remote site

11

by the hydrophone transducers of sonar system

24

. Accordingly, these modules create internal control signals for maneuvering UUV platform

20

in response to data signals and the remotely originating command signals thereby steering and guideing UUV platform

20

to mine

50

. Thus, UUV platform may be deployed at remote site

11

and may travel a distance of several nautical miles underwater under the control of command signals from remote site

11

. Once near mine

50

, UUV platform

20

may rely on data signals from sonar system

24

, magnetic system

26

, and camera system

31

to acquire, identify, and home in on one or more mines

50

and destroy them by projectile systems

25

A and

25

B.

Mine clearance system

10

of this invention has tag particles

40

to aid in locating, identifying, and destroying mines

50

. Referring to

FIGS. 3A

,

3

B, and

3

C, each tag particle

40

has a virtually uniformly sized volume of gas

41

contained inside a water-soluble acoustically transparent cover

42

that is at least partially coated by a water-activated adhesive

43

. Each acoustically transparent cover

42

allows interaction between impinging acoustic energy from projector-transducers of sonar system

24

and each gas volume

41

. The uniform size of gas volumes

42

and the relatively great acoustic impedance between the gas and the surrounding water will make each tag particle

40

resonate, or appear to radiate as a dominant acoustic source as compared to the ambient. This resonance, or apparent radiation will be created when each tag particle

40

is exposed to projected acoustic energy from transducers

24

at the particle's resonant frequency. The resonant frequency is a function of the dimensions of the gas volume

41

in the particle

40

. Optionally, the projected acoustic energy could come from another source, such as remote site, for example. Consequently, each mine

50

that has tag particles

40

on it will become more acoustically enhanced, or prominent in the projected acoustic energy from sonar system

24

. This will enable location of tagged mines

50

at greater distances than untagged mines

50

.

Referring also to

FIG. 3A

, when tag particles

40

are being stored or transported while they are in the dry state, or dry, the outer water-activated adhesive

43

is inert preventing coalescence of tag particles

40

. Accordingly, tag particles

40

can be stored in mass quantities on board aircraft

70

and freely sown or dropped to disperse over a wide area or region where mines

50

are suspected of being located. The combined weight of gas volume

41

, cover

42

, and adhesive

43

of each tag particle

40

is such as to make tag particles

40

be negatively buoyant and sink when they are in water.

Referring also to

FIG. 3B

, when adhesive

43

of each tag particle

40

contacts water

60

at a time, t=0, it is wetted and becomes activated (sticky). The outer, wetted surfaces of adhesive

43

become sticky enough to adhere to the outer surfaces of mines

50

. The gas volume

41

can be air, nitrogen or any type of relatively non-reactive gas having low moisture content. Cover

42

can be gelatin or some other acoustically transparent water-soluble material. Adhesive

43

can be any well-known water activated adhesive.

Referring also to

FIG. 3C

, after a period of time in water

60

beyond t=0, adhesive

43

dissolves, and water-soluble cover

42

dissolves. The dissolving of adhesive

43

and cover

42

of each tag particle

40

frees gas volume

41

to the water where it may escape. Consequently, there are virtually no readily discernable traces of tag particles

40

left for detection of the tagging process. Selection among well-known materials for and tailoring of cover

42

and adhesive

43

by one skilled in the art can change the rates of activation and dissolution.

Referring also to

FIG. 1

, aircraft

70

carrying dry tag particles

40

flies over a suspected minefield and drops tag particles

40

across a wide area of water

60

. Since tag particles

40

are heavier than water

60

, they sink in water

60

as tag particles

40

, designated

40

AA. Water

60

activates adhesives

43

on cover

42

causing particles

40

AA to become sticky. A small number of tag particles

40

, designated

40

BB, are stuck on the outer surfaces of mines

50

. The remainder of tag particles

40

settle on the bottom of water

60

and are designated

40

Cc. UUV platform

20

searches for reflected acoustic energy from mines

50

, those mines

50

that are tagged with adhered tag particles

40

(

40

BB) can be detected and UUV platform

20

can home in on them. Tag particles

40

(

40

CC) at the bottom are not detected, and after a period of time, they will dissolve sufficiently to each release gas volume

41

which is buoyed to the surface of water

60

.

Referring to

FIG. 4

, UUV platform

20

detects a tagged mine with projected and reflected acoustic energy at enhanced ranges for subsequent visual identification by camera system

31

. Tag particles

40

BB of mine hunting system

10

that are adhered to mines

50

make the job of finding them by UUV platform

20

easier and at a greater distance as compared to contemporary systems. After location and identification, each mine

50

can be methodically destroyed by UUV platform

20

which aims and fires one or more aimed high-kinetic energy supercavitating projectiles

25

C. The aimed high-energy supercavitating projectiles

25

C from projectile systems

25

A and

25

B are fired, or launched from UUV platform

20

that is located at a safe separation distance from each mine

50

. The use of a supercavitating projectile

25

C greatly extends the offset, or separation distance at which it will penetrate each mine

50

. The penetration of each mine

50

underwater with high kinetic energy supercavitating projectile

25

C completes the neutralization of each mine

50

, and the safe separation distance reduces the possibility of damaging UUV platform

20

so that it can find and destroy a number of mines during a single deployment.

Mine clearance system

10

of the invention uses supercavitating projectiles

25

C fired from underwater projectile system

25

A and

25

B on UUV platform

20

to destroy mines

50

underwater. Mine clearance system

10

also can use its supercavitating projectiles

25

C from projectile systems

25

A and

25

B for self-defense. Mine clearance system

10

has the ability to place tag particles

40

on mines

50

across a wide area or region via one or more aircraft

70

and deploy more than one UUV platform

20

to simultaneously clear mines

50

from an area.

Mine clearance system

10

uses tag particles

40

designed to “tag” underwater mines

50

and then dissolve and dissipate their gas volumes to limit their lifetime. Mine clearance system

10

uses identifying tag particles

40

to locate mines by acoustic means by its sonar system

24

, and optionally may use magnetic device

26

and/or camera system

30

.

Mine clearance system

10

of this invention provides for (1) less cost per mine destroyed, and (2) destruction of a large number of mines per mission as compared to contemporary mine neutralization systems. Mine clearance system

10

additionally has the ability to: (1) target and locate more mines per mission, (2) target mines quicker, (3) destroy mines in more adverse environmental conditions, (4) destroy mines from greater distances, (5) destroy mines undetected, (6) destroy mines located over a wider range of depths, and (7) destroy mobile mines as compared to contemporary mine neutralization systems.

The disclosed components and their arrangements as disclosed herein all contribute to the novel features of this invention. Mine clearance system

10

of this invention provides a reliable and cost-effective means to remove the threat that may otherwise be created by underwater mines. Therefore, mine clearance system

10

as disclosed herein is not to be construed as limiting, but rather, is intended to be demonstrative of this inventive concept.

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.