Abstract:
A system and method for disabling a small boat comprises at least two hulls and an entanglement device disposed therebetween. In the illustrative embodiment, each hull is an unmanned underwater vehicle. The system is launched from a vessel to intercept the small boat. When close to the small boat, the separating distance between the two hulls is increased, thereby deploying the entanglement device and causing it to become entangled with the small boat (e.g., the small boat&#39;s propulsion system, etc.).

Description:
STATEMENT OF RELATED CASES 
     This case claims priority of the following U.S. Provisional Patent Application Ser. Nos. 61/173,267 filed Apr. 28, 2009 and 61/174,249 filed Apr. 30, 2009. Both of these applications are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to means for disabling small water craft, such as are often used for hijacking or terrorist operations. 
     BACKGROUND OF THE INVENTION 
     Small watercraft can pose a hazard to commercial shipping and even naval ships. Regarding the former, Somali pirates have disrupted commercial shipping in the Gulf of Aden and even into the Indian Ocean. In 2008, these pirates collected in excess of $150 M in ransom from hijacked ship owners. The pirates use small craft to assault the ship; grappling hooks are used to secure lines, board the ship and seize control. Since modern merchant ships are highly automated, there are typically only small crews for onboard for defense. This enables pirates to easily overpower the crew and operate the ship after hijacking. 
     When maneuvering in restricted conditions, moored, or at anchor, naval vessels are particularly vulnerable to attack from a group of small, fast boats. Due to their size, speed, and maneuverability, these small boats can attack and then run and hide from larger navy vessels. To make matters worse, hostiles will often be operating in their own waters where they will typically enjoy a significant numerical advantage and superior knowledge of the waterways. This type of attack, which is referred to as a “small-boat-swarm,” is the tactic of choice for terrorists. 
     There are no truly cost-effective options for addressing the piracy issue. The naval response to small-boat-swarm has been to deploy similarly-sized, stealthy, fast, heavily-armed craft. An appropriately outfitted Zodiac-type raft has been used for this service. But even highly-trained navy personnel have a limited capability to withstand the repeated shock to their bodies that occurs when traveling in such craft at high speed in moderately high sea states. 
     SUMMARY OF THE INVENTION 
     The present invention provides a cost effective and non-lethal way to disable a small boat, such as used by pirates or terrorists. In accordance with the illustrative embodiment of the invention, a system for disabling a small boat comprises (1) two hulls, (2) a propulsion subsystem, (3) a homing, guidance, and control subsystem, (4) a depth-control subsystem, and (5) an entanglement device, typically comprising a long, stranded material that is neutrally or positively buoyant, suitably strong to be deployed by the moving hulls and not capable of being shredded by a prop. 
     The system, which is relatively small, is maintained aboard a commercial or naval vessel. If a small craft is detected by ships&#39; crew or on-board sensors, and if it is determined or likely that operators of the small craft have malicious intent, the system is deployed in the water. 
     The homing, guidance, and control subsystem acquires the target and causes the propulsion subsystem to move the system toward the small craft. As the system nears the target, the entanglement device is deployed. The entanglement device is deployed by increasing the distance between the two hulls, thereby causing the net, etc., to spread out near the surface of the water. 
     The intent of the entanglement device is, as its name suggests, to become entangled with the target craft. As previously noted, the entanglement device is a neutrally or positively buoyant, long, stranded material. In some embodiments, the entanglement device is a neutrally or positively buoyant net of monofilament construction and includes a plurality of strands of fibrous material that extend from net. If the small craft is propeller driven, the net or strands become entangled with the prop or other protruding features of the craft. If the small craft is a jet boat, the strands of fibrous material will be ingested into the jet intakes. In either case, the small craft will be incapacitated and rendered motionless in the water. 
     Assuming that the small boat is disabled at an acceptable standoff distance (several hundred meters, etc.) from the ship, its mission will be frustrated. For example, in the case of attempted piracy, the pirates will be prevented from boarding and there will be ample time for the commercial ship to escape and radio for help. Or, if the encounter is with a naval vessel, the small boat will not be able to approach the hull to place explosives or perpetuate other acts of sabotage. And the naval vessel can respond as appropriate. 
     Since the system is non-lethal, it presents decreased safety risks for the crew. Furthermore, if the system is deployed against what turns out to be a non-hostile target, there will be no loss of life and any potential liability will be significantly reduced. The system is intended to be disposable, so a relatively minimal level of sophistication in terms of tracking, guidance, and control systems is desirable. 
     In some embodiments, the two hulls are small, unmanned underwater vehicles (“UUVs”). In such embodiments, the propulsion subsystem, homing, guidance, and control subsystem, depth-control subsystem (typically a ballasting system), and propulsion subsystem will be onboard each UUV. 
     In some other embodiments, one or both of the hulls is powered (i.e., propulsion hulls), but they are not autonomous in the sense of a UUV. In such embodiments, the two hulls are typically each coupled via movable linkages to a third hull, which can house the homing, guidance, and control subsystem. These embodiments incorporate a mechanism for reconfiguring the linkages, which changes the separation distance between the hulls to deploy the entanglement device. 
     In still further embodiments, the hulls are not powered; rather they are attached to a third hull that incorporates a propulsion subsystem and a homing, guidance, and control subsystem. The hulls typically include the depth-control subsystem (e.g., a ballasting system, etc.). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts system  100  in accordance with the illustrative embodiment for disabling small watercraft. 
         FIGS. 2A-2D  depict system  100  of  FIG. 1  in use. 
         FIGS. 3A-3D  depict a first alternative embodiment of system  100 . 
         FIGS. 4A-4B  depict a second alternative embodiment of system  100 . 
         FIG. 5  depicts a mother ship having under-the-waterline bays for deploying a system for disabling small watercraft in accordance with the illustrative embodiment of the present invention. 
         FIG. 6  depicts a method for disabling small watercraft in accordance with the illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrative embodiment of a system for disabling small watercraft comprises:
         two hulls, wherein the separation distance between the hulls can be changed;   a way to propel and guide the hulls through water to a target;   an ability to float or submerge;   an entanglement device for disabling the target.
 
This system can be implemented in a variety of ways, a few of which are described herein and depicted in the accompanying drawings.
       

       FIG. 1  depicts system  100 , which is first embodiment of a system for disabling small watercraft. In system  100 , the two hulls are realized as UUVs  102 A and  102 B. Entanglement device  108  is coupled to UUVs  102 A and  102 B. 
     UUVs  102 A and  102 B can be any one of a number of available UUVs, including, without limitation, Mk 39 EMATT, SUBMATT, as available from Lockheed Martin, or other suitable UUVs. Each UUV includes homing, guidance, and control subsystem  104 , depth-control subsystem  105 , and propulsion subsystem  106 . 
     In some embodiments, homing, guidance, control subsystem  104  comprises passive and/or active sensors for acquiring the small craft and a processor running software capable of estimating a trajectory of the small craft and/or an intercept trajectory. Having acquired the position of the small craft, the guidance system issues commands, for example, to the propulsion systems of UUV  102 A and  102 B to propel system  100  toward the target. It will be appreciated by those skilled in the art that any one of a number of approaches to acoustic tracking, guidance, and control can be used for homing, guidance, and control system  104 . It is within the capabilities of those skilled in the art to design and implement such systems. 
     In the illustrative embodiment, depth-control subsystem  105  is a conventional ballasting system, well known to those skilled in the art. Propulsion subsystem  106  comprises an electrically-driven propulsor or water jet, or other thrust-generating systems suitable for propelling UUVs, as a function of their size. 
     In accordance with the illustrative embodiment, entanglement device  108  comprises net  110  (e.g., monofilament, etc.) having fibrous “streamers”  111  extending therefrom. In some embodiments, streamers  111  comprise a plurality of elongated strands of fibrous material, each of which strands has a length that is typically in the range of about 1 to 4 meters. Entanglement device  108  need not be a net, per se; it can take any form that is suitable for disabling the propulsion system (e.g. entangling the propellers or other external features, fouling the intakes of a jet-propelled craft, etc.) of a target. 
     Operation of a system for disabling a small craft, such as system  100 , is now described in conjunction with  FIGS. 2A through 2D  and  FIG. 6 . 
       FIG. 2A  depicts small craft  220  approaching vessel  200 , which in this embodiment is depicted as being commercial shipping vessel  200 . A crew member aboard vessel  200  is alerted to the presence of craft  220 . 
     In response, the crew of the commercial vessel deploys system  100  into the water, as depicted in  FIG. 2B . See also,  FIG. 6 , operation  601 , which recites “deploying two hulls in the water.” In some embodiments, system  100  is simply lowered over the side of the vessel  200 . In some other embodiments, vessel  200  includes special adaptations for a more-stealthy launch of system  100 , such as a towing cradle, etc., that keeps system  100  submerged. Such adaptations, which can also include below-the-waterline storage bays (see, e.g.,  FIG. 5 ), would more typically be used in conjunction with a naval vessel. 
     Once in the water, acoustic sensors associated with system  100  acquire craft  220  and develop trajectory estimates and an intercept solution. See also,  FIG. 6 , operation  603 , which recites “estimating a location of a target.” 
     System  100  then transits toward target  220  in accordance with trajectory/intercept estimates. See also,  FIG. 6 , operation  605 , which recites “transiting the hulls to the target.” In a preferred mode of operation, system  100  dives to maintain stealth and then transits toward craft  220 . 
     As system  100  approaches target  220 , it surfaces. After surfacing, or just prior to surfacing, and in response to a command from a human operator or in accordance with system programming, UUVs  102 A and  102 B increase their separation distance, thereby deploying entanglement device  108  as depicted in  FIG. 2C . See also,  FIG. 6 , operation  607 , which recites “deploying an entanglement device by increasing a lateral separation between the two hulls.” 
     With entanglement device  108  deployed (e.g., net with streamers, etc.), system  100  engages target  220 , as depicted in  FIG. 2D . The small craft becomes tangled in the net and the streamers snare the prop of the small craft or foul its jet intakes, whichever is present. See also,  FIG. 6 , operation  609 , which recites “causing the entanglement device to become entangled with a portion of the target.” 
     In some further embodiments, more than one instance of system  100  is used. The use of a relatively larger number of these systems increases the potential reach of entangling device  108  and, of course, is required when the attacking force includes plural small watercraft. 
       FIGS. 3A through 3D  depict system  300 , which is an alternative embodiment of system  100  depicted in  FIG. 1 . One significant difference between system  300  and system  100  is that in system  300 , hulls  302 A and  302 B are not UUVs. At least one of hulls  302 A and  302 B is a propulsion hull (i.e., includes a propulsion subsystem), but neither of these hulls function autonomously in the manner of a UUV, such as UUVs  102 A and  102 B. 
     Referring now to  FIGS. 3A through 3D ,  FIG. 3A  depicts a front view of system  300  wherein entanglement device  108  is not deployed,  FIG. 3B  depicts the same view as  FIG. 3A  but with entanglement device  108  deployed,  FIG. 3C  depicts a side view of system  300  in the same state as in  FIG. 3A , and  FIG. 3D  depicts a top view of system  300  in the same state as in  FIG. 3B . For clarity, streamers  111  are not depicted in  FIGS. 3A and 3B  and the various linkages and other structure beneath entanglement device  108  are not depicted in  FIG. 3D . 
     System  300  comprises hulls  302 A and  302 B, secondary hull  326 , linkages  312 A and  312 B, and entanglement device  108 , interrelated as shown. 
     With particular reference to  FIGS. 3A and 3B , linkage  312 A couples hull  302 A to secondary hull  326 . Likewise, linkage  312 B couples hull  302 B to secondary hull  326 . As will be evident from  FIG. 3C , system  300  includes two sets (one forward, one rear) of  312 A linkages (for coupling to hull  302 A) and two sets of  312 B linkages (for coupling to hull  302 B). Only the forward  312 A and  312 B linkages are depicted in  FIGS. 3A and 3B  and neither forward nor rear  312 B linkages are depicted in  FIG. 3C . 
     In the embodiment of system  300  depicted in  FIGS. 3A through 3D , linkages  312 A and  312 B are articulated or jointed. That is, pivot point  316  rotatably couples linkage member  314  to linkage member  320  and pivot point  322  rotatably couples linkage member  320  to secondary hull  324 . 
     Linkages  312 A and  312 B are capable of reconfiguring to change the separation distance between hulls  302 A and  302 B by allowing the linkage members to partially rotate relative to one another. Compare, for example,  FIG. 3A  to  FIG. 3B ; the separation between hulls  302 A and  302 B is greater in  FIG. 3B  than in  FIG. 3A . To achieve this increased separation, the angle between linkage member  320  and secondary hull  324  is increased and the angle between linkage members  320  and  314  is increased. And with the increased separation shown in  FIG. 3B , entanglement device  108  deploys. 
     System  300  includes a mechanism or arrangement for reconfiguring linkages  312 A and  312 B. In the embodiment depicted in  FIGS. 3A through 3B , the mechanism comprises spring-biasing devices  318  and  324 . The spring-biasing devices are arranged with respect to linkage members  314  and  320  such that in the absence of some restraint, device  318  causes member  314  to rotate away from member  320 . Device  324  causes linkage member  320  to rotate away from secondary hull  326 . In some embodiments, the restraint is a latch or similar mechanism (not depicted) that, when engaged, maintains linkages  312 A and  312 B in their “stowed” or non-extended state (as in  FIG. 3A ). When homing, guidance, and control system  104  determines that system  300  is in the vicinity of the target and entanglement device  108  is to be deployed, the subsystem sends a signal to an actuator (not depicted) to move the latch, thereby freeing linkage members  314  and  320 . Once the linkage members are freed, the potential energy stored in spring biasing devices  318  and  324  can be released, resulting in the rotation of the linkages members, as previously described. 
     In conjunction with the present disclosure, those skilled in the art will be able to design and incorporate any one of a variety of mechanisms suitable for accomplishing the above-described functionality (i.e., reconfiguring linkages  312 A and  312 B). It is notable that for most contemplated uses, it is not necessary for linkages  312 A and  312 B to be able to autonomously return to their stowed after entanglement device  108  is deployed. After successful deployment and immobilization of a target, system  300  can be reset manually after recovery, to the extent recovery is desired. That is, with its relatively low cost, system  300  can be considered to be disposable. 
       FIG. 3A  depicts system  300  fully submerged, which is optional if not preferable when transiting to a target (see, e.g.,  FIG. 6 : operation  605  of method  600 ).  FIG. 3B  depicts system  300  with hulls  302 A and  302 B and entanglement device  108  floating. 
       FIGS. 4A and 4B  depict system  400 , which is a second alternative embodiment of system  100  depicted in  FIG. 1 . A first primary difference between system  400  and system  300  is that in system  400 , neither hull  402 A nor hull  402 B is a propulsion hull. Rather, secondary hull  426  is a propulsion hull. 
     Referring now to  FIGS. 4A and 4B ,  FIG. 4A  depicts a side view of system  400  with entanglement device  108  not deployed and  FIG. 4B  a rear view with system  400  in the same state as in  FIG. 4A . For clarity, streamers  111  are not depicted in  FIG. 4A . 
     System  400  comprises hulls  402 A and  402 B, secondary hull  426 , two sets each of linkages  412 A and  412 B, and entanglement device  108 , interrelated as shown. 
     Linkages  412 A and  412 B function in the manner of linkages  312 A and  312 B, previously described. Hulls  402 A and  402 B depth-control subsystem  405  (e.g., ballasting system, etc.). Homing, guidance, and control subsystem  104 , and propulsion subsystem  106  are disposed in secondary hull  426 . 
       FIG. 5  depicts mother ship  500 . The mother ship includes under-the-waterline bays  530 A,  530 B,  530 C, and  530 D for stowing any of systems  100 ,  300 , or  400  disclosed herein. In a threat condition, one or more of these systems can be deployed from ship  500  without alerting a target of the release. 
     It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.