DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0022] The present invention relates to a special-purpose, self-propelled unmanned underwater vehicle 10 as shown in FIGS. 1 - 7 that may be launched from any of numerous platforms in the vicinity of a submarine 12 . The vehicle 10 may be guided toward the submarine 12 by a controller 13 (See FIG. 7 ) using data from internal (unmanned underwater vehicle-mounted) and/or external (launch platform-mounted) sensors of various types, such as acoustic, optic, and magnetic sensors. External sensory data may be fed to the vehicle 10 through a thin, spooled, trailing wire or by using optical or other covert methods. As can be seen from FIG. 1 , the vehicle 10 preferably approaches the submarine 12 from behind, along a tangential path, so as to avoid a collision that might alert the submarine crew and damage the vehicle 10 and its components. The vehicle 10 will target a predetermined area of the submarine that is well suited for both stealthy and longterm attachment.

[0023] Referring now to FIG. 1 , as the vehicle 10 approaches the submarine 12 , the vehicle 10 will match the submarine's speed and direction. This can be accomplished through adjustment of the forward thrust of the vehicle 10 and the positioning of its forward and rear control surfaces 14 and 15 , respectively.

[0024] As can be seen from FIG. 2 , the vehicle 10 has a surface 16 which is to be positioned adjacent the hull 18 of the submarine 12 . As the vehicle 10 approaches the submarine 12 , it maneuvers to orient the surface 16 towards the hull 18 . This maneuvering may be carried out using the control surfaces 14 and 15 and/or thrusters 20 onboard the vehicle 10 .

[0025] After being properly oriented, the vehicle 10 brushes up against the hull 18 using one or more of several techniques. Rear control surfaces 15 and forward control surfaces 14 can induce lift in the direction of the submarine hull 18 . Built-in thrusters 20 can act as suction devices. The shape of the underwater vehicle hull can create a venturi effect, drawing the vehicle 10 toward the submarine 12 . Fold-out panels 22 can be provided on the vehicle to divert water flow over the vehicle 10 . As forward thrust from the vehicle's propeller(s) 25 compensates for axial drag, these methods will produce forces causing the hull 26 of the vehicle 10 to be pinned against the submarine 12 .

[0026] With the vehicle 10 pinned against the submarine hull 18 at a predetermined location and orientation, the vehicle 10 begins its attachment routine. The vehicle 10 must be oriented so that its attachment apparatus is facing the submarine hull 18 . The vehicle propeller(s) 25 provides forward thrust to maintain the static location of the vehicle 10 with respect to the submarine 12 . At this point, the vehicle 10 attaches itself to the submarine 12 , the exact attachment method depending upon the nature of the submarine's hull surface.

[0027] Many submarines are coated with a thick, rubberlike material 30 which dampens acoustic emissions and reflections. To attach to such a material, an actuator 32 and a motor 34 inside the vehicle 10 may extend one or more corkscrew-like devices 36 through the surface 16 , as shown in FIG. 3 . Thereafter, the device(s) 36 may be driven into the coating material 30 using a twisting motion. One or two turns of the device(s) 36 should provide a sufficient foothold. This action must be done swiftly, before reactive forces push the vehicle 10 away from the hull 18 . Multiple attachment points may be necessary to prevent the vehicle 10 from becoming dislodged or from rattling against the hull 18 due to turbulent water flow along the submarine 12 .

[0028] If a submarine's outer layer is not rubberlike, it is most likely ferrous and, therefore, ferromagnetic. For this application, as shown in FIG. 4 , the vehicle 10 attaches itself to the submarine 12 using one or more permanent magnets 38 residing within the vehicle hull 26 . The magnet(s) 38 are driven toward the vehicle hull 26 along a rotating screw 40 powered by a low-speed, high-torque electric motor 42 . Magnetic attachment may also be possible if the submarine 12 has a sufficiently thin rubberlike coating 30 .

[0029] The permanent magnets 38 may also be used to assist in drawing the vehicle 10 toward a ferrous submarine hull during the vehicle's final approach. To increase the attractive force between the vehicle 10 and the submarine 12 during an approach maneuver, the permanent magnets 38 may be briefly augmented by collocated electromagnets (not shown). High power requirements, however, would make electromagnets unsuitable for extended operation with an electrically powered unmanned underwater vehicle.

[0030] Sound will be produced when the vehicle 10 impacts the submarine 12 , especially if the submarine hull 18 is uncoated metal. To dampen this sound, and thereby reduce the likelihood of alerting the submarine crew as to the presence of the vehicle 10 , sections of the vehicle 10 most likely to strike the submarine, i.e. the nose and tail, may be coated with a thin layer of soft material.

[0031] Once the vehicle 10 has attached itself, propulsive power is provided by the host submarine 12 . The motor 46 used to drive the propeller(s) 25 may become a generator, powered by water turning the propeller(s) 25 . The generator may be used to recharge one or more batteries 29 onboard the vehicle 10 , reducing the quantity of batteries needed for a long mission.

[0032] Attached to the host submarine 12 , the vehicle 10 remains quiet and motionless except for the propeller(s) 25 , drive shaft 27 and motor-generator 46 . Its function is to go wherever the submarine 12 goes and remain undetected by the submarine crew. The vehicle 10 may be used to collect and store data on compass bearing, speed—as indicated by the propeller turning rate—and oceanographic conditions such as depth and temperature. The vehicle 10 may reveal its location by emitting a dye marker 50 that floats to the surface and is visible from above, akin to an oil slick, or by periodically ejecting an RF beacon 52 similar in operation to an emergency position indicating radio beacon (EPIRB). An EPIRB is an RF transmitter that notifies maritime rescue services by sending a coded signal which is relayed by satellite to a ground station. When released from a submerged vessel, it rises to the surface and begins transmitting a distress call automatically. The RF beacon 52 could also upload stored data.

[0033] The vehicle 10 may also contain one or more hydrophones 54 for monitoring the acoustic environment at all times. If it is decided that the host submarine 12 must be located and destroyed, a coded acoustic signal may be transmitted to the vehicle 10 by methods which can cover large areas of ocean, such as surface ship active sonar, submarine active sonar, helicopter dip sonar, seafloor-mounted acoustic projectors, etc. Upon receiving and decoding this command, the vehicle 10 may immediately begin transmitting acoustically by means of an acoustic projector 56 . It should be understood that the term “transducer” can refer to both an acoustic projector, such as 56 , and an acoustic receiver, such as hydrophones 54 . The term “hydrophone” refers explicitly to an acoustic receiver. The acoustic output may be of a frequency and source level that will travel great distances underwater, facilitating rapid localization of the submarine 12 .

[0034] Once the vehicle 10 begins transmitting, the submarine 12 must be localized and attacked before it has time to surface, stop moving, deploy divers, deactivate the vehicle 10 , and disappear beneath the waves. It should be noted that the act of surfacing and stopping greatly increases the submarine's vulnerability, especially to attack from the air. When the hydrophone(s) 54 receive acoustic signals in the torpedo active homing frequency range, it may begin echo-repeating those signals through its acoustic projector 56 , thereby acting as a homing beacon for nearby torpedo 58 as shown in FIG. 5 .

[0035] If the vehicle 10 remains quiet, once attached it can likely remain there undetected until located visually. There is no practical way to inspect the hull of a moving or deeply submerged submarine. Hull inspections at sea, which are quite rare, must be done with the submarine almost stationary and at or near the surface. The conventional method of performing such an inspection involves divers using scuba equipment and visual aids. Assuming that one does not want the vehicle 10 to be detected, the vehicle 10 can detach itself upon completion of its mission or under speed and depth conditions that permit a visual inspection of the submarine hull 18 . Speed can be determined by measuring vehicle propeller turning rate, using a sensor 64 such as an accelerometer, a tachometer or from acoustic cues. Depth can be gauged via a pressure sensor 60 .

[0036] If the vehicle 10 is attached to the submarine's rubber coating 30 , it will detach itself simply by reversing the direction of the electric motor 34 which drove the corkscrew(s) 36 into the coating. As soon as the corkscrew(s) 36 separate(s) from the hull 18 , the vehicle 10 will drift away. If permanent magnets 38 are employed, detachment is accomplished by driving the magnets 38 away from the submarine hull 18 , combined with propulsive thrust to overcome the diminished yet still finite magnetic attraction between the vehicle 10 and submarine hull 18 . In either case, separation must be executed in a controlled maneuver so as to avoid striking the submarine hull 18 or being sucked into its propellers.

[0037] Upon detaching from the submarine 12 , as shown in FIG. 6 , the vehicle 10 will proceed far enough away to preclude its visual detection by submarine divers. The vehicle 10 may upload stored data by releasing an RF beacon 52 and then scuttle itself. Alternatively, the vehicle 10 may traverse to a predetermined pickup point, surface with the aid of a balloon 62 inflated by gas from a pressurized flask, signal its location via an acoustic or RF link, and await recovery.

[0038] FIG. 7 provides a schematic diagram of the components of the vehicle 10 . These components are operatively connected to controller 13 which controls and coordinates operation of the components to provide the functionality disclosed above.

[0039] As can be seen from the foregoing description, the vehicle 10 may be used to covertly monitor and report the activities of a submarine. The vehicle 10 may also be used as a remotely activated, acoustic localizing beacon for anti-submarine warfare forces. The vehicle 10 may also be used to act as an echo-repeater or other type of torpedo acoustic homing beacon.

[0040] It is apparent that there has been provided in accordance with the present invention an unmanned underwater vehicle which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.