Abstract:
A test system that is capable of evaluating the effectiveness of a weapons system designed to defeat an incoming, fast-moving, underwater munition is disclosed. In the illustrative embodiment, an extremely large tubular sheath is inflated underwater. The sheath is maintained at a depth and inclination that is appropriate for an incoming torpedo. An inert projectile is launched or flown inside the sheath at a speed that is consistent with the speed of munition that the weapons system is intended to defeat.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This case claims priority of U.S. Provisional Patent Application U.S. 60/908,679, which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to weapon systems in general, and, more particularly, to a system for testing a weapons system. 
       BACKGROUND OF THE INVENTION 
       [0003]    The Shkval is a high-speed, supercavitating, rocket-propelled torpedo developed by Russia. It was designed to be a rapid-reaction defense against U.S. submarines undetected by sonar. It can also be used as a countermeasure to an incoming torpedo, forcing the hostile projectile to abruptly change course and possibly break its guidance wires. 
         [0004]    The solid-rocket propelled torpedo achieves a high velocity of 250 knots (288 mph) by producing an envelope of supercavitating bubbles from its nose and skin, which coat the entire weapon surface in a thin layer of gas. This causes the metal skin of the weapon to avoid contact with the water, significantly reducing drag and friction. 
         [0005]    The Shkval is fired from the standard 533-mm torpedo tube at a depth of up to 328 ft (100 m). The rocket-powered torpedo exits the tube at 50 knots (93 kmh) and then ignites the rocket motor, propelling the weapon to speeds four to five times faster than other conventional torpedoes. The weapon reportedly has an 80 percent kill probability at a range of 7,655 yd (7,000 m). 
         [0006]    The torpedo is guided by an autopilot rather than by a homing head as on most torpedoes. Reportedly, there is a homing version of the Shkval that starts at the higher speed but slows and enters a search mode. 
         [0007]    Notwithstanding its defense-motivated origins, the Shkval is potentially a very significant offensive threat. To defeat such a torpedo, a surface ship deck-launched anti-torpedo must be capable of (1) brief but stable flight, (2) entering the water at a low grazing angle, and (3) sustaining a supercavitating running mode under water. 
         [0008]    There are no torpedo vehicles available that are capable of approaching the Shkval&#39;s speed. It is not possible, therefore, to access the feasibility of any anti-Shkval weapon system to a reasonable level of confidence. Consequently, there is a need for a test set-up that can act as a surrogate for an attacking Shkval torpedo, so that an anti-Shkval weapon system can be developed and tested. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a test system that is capable of evaluating the effectiveness of an anti-Shkval weapon system or other weapons system designed to defeat an incoming, very fast-moving, underwater munition. 
         [0010]    In the illustrative embodiment, an extremely large tubular sheath is inflated underwater. The sheath, which is effectively a “balloon,” is maintained at a depth and inclination that is appropriate for an incoming torpedo. An inert projectile is flown/propelled inside the sheath at the speed of a Shkval torpedo—250 knots. 
         [0011]    The sheath must be large enough in diameter to accommodate at least a minimal amount of projectile maneuvering. And the sheath must be long enough to provide for an expected amount of travel based on the projectile&#39;s speed and the time it is likely to take for the defensive system to “acquire” and destroy the projectile. A sheath having a diameter (inflated) that is in the range of about 5 to 15 meters and a length (inflated) that is in the range of about 50 to 500 meters should be adequate, as a function of the specific aspects of the anti-weapon that are being tested. 
         [0012]    The sheath must of course be sufficiently pressurized to resist water pressure, as a function of its depth under water. In some embodiments in which the projectile is missile (i.e., self-powered), the sheath is reinforced at the region where the missile initially fires, to accommodate the heat and erosive exhaust is generated. 
         [0013]    The sheath, projectile, or both can be appropriately painted to simulate the reflectivity of a Shkval, as influenced by the supercavitating bubbles that would be shrouding it in its supercavitating running mode. Alternatively, the air can be colored or misted for the same purpose. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  depicts a diagram of a test system in accordance with the illustrative embodiment of the present invention. 
           [0015]      FIG. 2  depicts a further embodiment of the test system of  FIG. 1 , wherein floats and/or weights are used to adjust the inclination of the sheath. 
           [0016]      FIG. 3  depicts an example in which a proposed anti-supercavitating torpedo weapon system is tested via the test system of  FIG. 1 . 
           [0017]      FIG. 4  depicts a block diagram of the weapon system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  depicts a diagram of test system  100  in accordance with the illustrative embodiment of the present invention. The test system can be located in a large and sufficiently deep pond or tank, or in a natural water way, as appropriate. In the illustrative embodiment, test system  100  is used to test a ship-mounted high-speed-torpedo defense system, such as system  122 , which is located on vessel  120 . 
         [0019]    In the illustrative embodiment, system  100  includes gas supply line  102 , sheath  110 , and inert projectile  112 . Gas supply line  102  is partially submerged; gas intake  104  is above the water line and gas discharge  108  is below the water line. Gas supply line  102  is supported in an appropriate fashion (e.g., from above, from below, etc.). 
         [0020]    Gas intake  104  of the gas supply line receives flow  118  of gas (e.g., air, nitrogen, etc.). In some embodiments, the gas as supplied is appropriately pressurized. In some other embodiments, gas supply line  102  includes an inline gas compressor (not shown). The inline gas compressor draws gas (e.g., air, etc.) into gas intake  104 , compresses the gas, and then directs it toward gas discharge  108 . Some embodiments will receive gas from a pressurized source and then pressurize it further via an inline compressor. 
         [0021]    Control valve  106  controls flow  118  of gas through supply line  102 . In some embodiments, control valve  106  is remotely controlled. Control valve  106  is meant to be representative of what is more likely to be an arrangement of valves (e.g., check valves, flow control valves, etc.) for controlling the flow of gas through supply line  102 . 
         [0022]    Sheath  110  is coupled, via a gas-tight connection, to gas discharge  108  of gas supply line  102 . The sheath is a non-porous bag, typically flexible, that is suitable for inflation with a gas. Effectively, sheath  110  is a very long, tube-shaped balloon. 
         [0023]    Flow  118  of compressed gas exits gas discharge  108  of gas supply line  102  and inflates sheath  110 . 
         [0024]    Supported within sheath  110  is projectile  112 . The projectile is inert; in other words, it does not carry a munitions payload. Projectile  112  is supported by support  114 , which in the illustrative embodiment, is coupled to gas supply line  102 . 
         [0025]    Projectile  112  can be self-powered (e.g., a missile, etc.), or it can be ejected (e.g., launched via an auxiliary power source). To the extent that projectile  112  is self-powered, shield  116  is advantageously employed to protect sheath  110  from hot exhaust gases. Furthermore, in some embodiments, sheath  110  is reinforced and appropriately lined, proximal to the launch location, with a heat- and abrasion-resistant material. Once launched, projectile  112  proceeds through sheath  110 . 
         [0026]    Sheath  110  must be large enough in diameter to accommodate at least a minimal amount of projectile maneuvering. To that end, diameter D of the inflated sheath is typically in a range of about 5 to 15 meters. Furthermore, the sheath must be long enough to provide for an expected amount of travel based on the speed of projectile  112  speed and the time it is likely to take for the defensive system to “acquire” and, as appropriate, destroy the projectile. Length L of the sheath is typically in a range of about 50 to 500 meters, as a function of the specific aspects of the anti-weapon that are being tested (e.g., target acquisition or target acquisition and neutralization, etc.). 
         [0027]    To serve as a useful test bed, sheath  110  should be situated underwater at an appropriate depth. That depth will typically be 100 meters or less. 
         [0028]    In most instances, a torpedo will be fired from a depth that is greater than that of its target. In other words, the torpedo will rise from its launch depth to a target depth. As a consequence, it is advantageous to control the inclination of sheath  110  to permit projectile  112  to follow a typically inclined trajectory. 
         [0029]    Sheath  110  is depicted in a horizontal attitude in  FIG. 1 . Actually, it&#39;s free end would typically rise higher in the water than the fixed end (located at discharge  108 ), since the sheath is filled with gas and is less dense than the water. The inclination of sheath  110  can be controlled using floats  224  and weights  225 , as depicted in  FIG. 2 . Any desired inclination/declination can be provided with an appropriate selection of floats and weights. 
         [0030]    In some embodiments, ribs (not depicted), are positioned along the length of sheath  110 . The ribs provide rigidity to inflated sheath  110  to help maintain an elongated cylindrical shape. 
         [0031]      FIG. 3  depicts test system  100  being used to test ship-mounted high-speed-torpedo defense system  122  aboard vessel  120 . The high-speed torpedo-defense system integrates several conventional technologies via a command and control system. The control system coordinates the activities of these various technologies to acquire and destroy a rocket-propelled or other high-speed torpedo. 
         [0032]    Torpedo defense system  122 , which is not a part of test system  100 , includes command and control system  326 , SONAR  328 , LIDAR  330 , and weapons system  334 . See also  FIG. 4 , depicting the flow of communications and information between the various elements of high-speed torpedo defense system. 
         [0033]    Command and control system (“CCS”)  326  coordinates the activities of and provides processing for the constituent systems (SONAR  328 , LIDAR  330 , and weapons system  332 ). More particularly, CCS  326  coordinates initial detection, via SONAR, which provides the torpedo&#39;s bearing to about +/− one degree. The CCS also coordinates hand-off to LIDAR  330  for high resolution bearing and ranging. Furthermore, CCS  326  coordinates weapons system  332 , under the control of LIDAR  330 . 
         [0034]    CCS  326  comprises one or more processors. Due to the rapid response time required to acquire and destroy a high-speed torpedo (i.e., about 5 seconds), CCS  326  operates with relative autonomy. CCS  326  does require operator interaction for initialization, system troubleshooting, training, and support. In some embodiments, CCS  326  includes redundant hardware that is disposed in several locations aboard ship to improve the survivability of system  122 . 
         [0035]    SONAR system  328  comprises conventional passive SONAR, active SONAR, or both. In some embodiments, the SONAR system is modified to provide higher-frequency detection for increased resolution by reducing the spacing of hydrophones in the SONAR array. CCS  326  supports the operation of SONAR  328  by performing data processing for passive SONAR (e.g., beamforming, classification, track, etc.) to develop the initial detection and bearing information relative to the frame of reference for the other systems (e.g., LIDAR  330  and weapons  332 . CCS  326  also controls active SONAR with information for waveforms, source level, and other acoustic parameters that are required for proper operation. 
         [0036]    LIDAR  330  is a conventional light detection and ranging system for ranging and tracking. It typically utilizes a high-power pulsed laser system. CCS  326  provides LIDAR  330  with control data for operation and aiming. Further, CCS  326  takes the optical data from LIDAR receivers and develops high-resolution track information relative to the gun frame of reference. 
         [0037]    Weapons system  332  comprises one or more rotary guns (e.g., a gatling gun, etc.) or reciprocating guns. In some embodiments, the gun fires low-grazing angle, supercavitating projectiles, such as projectile  336 . CCS  326  develops gun control information that will properly lead the gun to fire projectiles where the target will be when the projectiles travel to that volume. The software for CCS  326  accounts for any translation impacts due to ship movement, including mast motions, gun recoils, gun inertial, ship movement due to weather, etc. 
         [0038]    In operation of test system  100  to evaluate the efficacy of high-speed torpedo defense system  122 , projectile  112  is launched/fired. SONAR  328  of defense system  122  detects (or, if ineffective, does not detect) the launch of projectile  112  and determines bearing and approximate range. Bearing accuracy is about +/− one degree. 
         [0039]    SONAR  328  hands over bearing and range to LIDAR  330 , which places an initial range “gate” in a fixed position at approximately a standoff range. In an actual encounter, the gate would be at about 1000 yards. But in the context of test system  100 , the gate is suitably adjusted to meet the limitations (reduced size scale) of test system  100 . 
         [0040]    When projectile  112  breaches the gate, LIDAR  330  initiates tracking of the torpedo, determining its position in angle-angle range space. LIDAR  330  then hands this information over to weapons system  332 . More particularly, the information from LIDAR  330  is used to position the guns to an initial pointing position, positioning the gun at the exact firing point to provide a high probability of projectile impact with the incoming projectile  112 . 
         [0041]    In an actual attack scenario, weapons system  332  would open fire at about 500 meters. This distance is suitably adjusted for the reduced size scale of test system  100 . In some embodiments, projectiles are not fired from weapons system  332  toward test system  100 . In some other embodiments, projectiles  334  are fired from weapons system  332 , which will damage or destroy sheath  110 . In some embodiments, projectiles  334  from the deck launcher are preferably cavity-running, delayed-ignition, high-explosive projectiles. The projectiles are designed to enter the water at low grazing angles, and enter into a cavity-running or super-cavitation mode. On impact with the torpedo, a delayed ignition system detonates a high-explosive fill. 
         [0042]    The performance of the high-speed-torpedo defense system is evaluated based on target acquisition time and other performance measures.