Patent Publication Number: US-2013233232-A1

Title: External Rescue and Recovery Devices and Methods for Underwater Vehicles

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority of U.S. Provisional Application Ser. No. 60/983,784 filed Oct. 30, 2007 entitled “External Rescue And Recovery Device For Underwater Vehicles,” which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Autonomous Underwater Vehicles (“AUV”) and other devices that drive underwater are generally required to be very close to neutrally buoyant for proper underwater operation. As such, a vehicle that weighs about 42 pounds in air weighs about negative 7 ounces in water if the buoyancy is +1%. When operating an AUV there is a real fear that the AUV could become stuck underwater in mud or caught on a rope or line, and with so little upward force it is not likely that the AUV would be able to force itself back to the water surface for recovery. 
     If an AUV drives into mud nose first, it might take significant upward force (buoyancy) to pull the AUV free and send it to the water surface. This could require about 2-10 pounds of upward force to have the AUV pulled free from the mud. The normal operating model is to send divers down to free the AUV and let it float to the water surface. One method of creating extra buoyancy is to carry one or more ballast weights, e.g., lead weights, at neutral buoyancy, then drop a weight using an automatic release to increase the AUV&#39;s buoyancy. Emergency ballast weights have been used on many underwater vehicles, but such weights typically provide only a few extra pounds of buoyancy, or a few percent of the body weight. 
     Underwater devices such as AUVs present difficulties that prevent or restrict the adding of safety devices to the body of the vehicle. For example, their hulls or internal structures are usually pressure vessels to keep electronics contained therein dry while underwater at some pressure, thereby making access through the hull for installation or deployment problematic. Space within the underwater vehicle is very limited to add safety devices, but many underwater vehicles add some form of emergency device. The implementation of the emergency device is usually tightly integrated into the design of the underwater vehicle, burdening the underwater vehicle with the emergency device&#39;s cost and complexity. Conventional emergency devices include 1) a drop or ballast weight that can be dropped from the underwater vehicle automatically if it detects an emergency situation to add many pounds of upward force (buoyancy) to help the vehicle free itself and get to the surface for recovery; 2) an inflatable bag filled with a gas providing large amounts of positive (upward) buoyancy aiding the vehicle to get to the surface of the water, such as the expandable bag or sleeve described in U.S. Pat. No. 4,271,552 issued Jun. 9, 1981 titled “Torpedo Floatation Device,” hereby incorporated by reference in its entirety, but the complexity of inflatable bags dominates the underwater vehicle design, so they are not generally used; 3) an acoustic locator pinger that sends a loud sound out at a particular frequency or rate so the vehicle can be located from the surface with directional location devices; 4) a small float, optionally with a Global Positioning System (“GPS”) to transmit the location of the vehicle in distress via radio signals, dropped on a long line that is released, floats to the surface, and is used to find the underwater vehicle so it can be pulled up or retrieved by dive; and 5) lights to aid divers in close range location of the distressed vehicle. While certain of these conventional emergency devices have been used on underwater vehicles, they are either ineffective and/or have been integrated into the main vehicle, adding significantly to the size, complexity, and cost of the main vehicle. Furthermore, these systems need to be planned in the early stages of a design of the underwater vehicle. 
     Accordingly, there remains a need for effective, efficient rescue and recovery of underwater vehicles. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides methods and devices for rescuing and recovering underwater vehicles. In one embodiment, a rescue and recovery system is provided that includes a submersible housing configured to be coupled to and disposed at least partially outside an underwater vehicle, an emergency mechanism located within the housing and configured to be deployed upon detection of an emergency condition, and an actuator configured to deploy the emergency notification mechanism. The emergency condition can vary, but it can include at least one of exceeding a threshold dive depth, exceeding a threshold dive time, falling below a threshold travel speed, the housing longitudinally oriented above a threshold angle, a power loss in the underwater vehicle coupled to the housing, exceeding a threshold dive speed, and receipt of a distress signal. The emergency mechanism can have a variety of configurations and can include at least one of a light, an expandable bag, a flare, a signal transmitter, a flag, a dye, and a GPS system. In some embodiments, the emergency mechanism can include a buoyancy mechanism, and the actuator can be configured to expand the buoyancy mechanism to increase a buoyancy of the housing and the underwater vehicle coupled to the housing. 
     The rescue and recovery system can have any number of variations. For example, the housing can be configured to decouple from the underwater vehicle upon detection of an emergency condition. As another example, the actuator can include at least one of an R134a refrigerant, carbon dioxide, and an explosive powder. As yet another example, the rescue and recovery system can include a sensor configured to detect an emergency condition and to trigger the actuator to deploy the emergency mechanism upon detection of the emergency condition. The sensor can be located within the housing. In some embodiments, the housing can be coupled to an underwater vehicle, and the sensor can be located within the underwater vehicle. As still another example, the rescue and recovery system can include a power system located within the housing and be configured to provide power to the housing independent of an underwater vehicle coupled to the housing. The actuator can be configured to turn on the power system upon detection of the emergency condition. 
     In some embodiments, the rescue and recovery system can include a cable configured to couple the housing to the underwater vehicle. The cable can connect to a head of the housing and a tail of the underwater vehicle to allow the housing to be towed underwater by the underwater vehicle. The cable can be configured to have a first length extend between the housing and the underwater vehicle and a second length that is longer than the first length contained within at least one of the housing and the underwater vehicle. At least a portion of the cable can be configured to unspool when underwater to increase a distance between the housing and the underwater vehicle. 
     In another embodiment, a self contained rescue system for an underwater vehicle is provided that includes an expandable buoyancy mechanism, a propellant providing system operatively connected to the expandable buoyancy mechanism for selectively inflating the buoyancy mechanism, and a mechanical connecting element for connecting the rescue system to an underwater vehicle. The system can have any number of variations. For example, the buoyancy mechanism can include an inflatable bag. As another example, the system can include a localization means and a communication means for determining, following deployment of the buoyancy mechanism and arrival at a water surface, a location of the rescue system and communicating the location. As yet another example, the system can include an acoustic pinger for communicating in water. 
     Some embodiments can include an underwater vehicle, and the mechanical connecting element can be connected to the underwater vehicle. The rescue system and the underwater vehicle can be configured to be in electronic communication. In some embodiments, the underwater vehicle can be configured to provide power to the rescue system. The underwater vehicle can be configured to signal the rescue system to deploy the buoyancy mechanism. The underwater vehicle can include an emergency detection means configured to signal the rescue system to deploy the buoyancy mechanism. The rescue system can be configured to be towed behind the underwater vehicle, e.g., about 2 to 4 feet behind the underwater vehicle. 
     In another embodiment, a rescue and recovery system is provided that includes a housing, a buoyancy chamber included in the housing and having a buoyancy mechanism disposed therein, a propellant chamber included in the housing, operatively connected to the buoyancy chamber, and configured to trigger expansion of the buoyancy mechanism disposed in the buoyancy chamber, and a coupling element configured to couple the housing to an underwater vehicle. The system can have any number of variations. For example, the coupling element can include a cable, and the cable can be configured to be removably coupled to the underwater vehicle. As another example, expansion of the buoyancy mechanism can be effective to float at least the housing toward a water surface. The system can include a localization means and a communication means for determining, following deployment of the buoyancy mechanism and arrival at the water surface, a location of the housing and communicating the location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of one embodiment of a rescue device; 
         FIG. 2  is a side view of the rescue device of  FIG. 1 ; 
         FIG. 3  is a perspective view of a tail portion of the rescue device of  FIG. 1  having a containment chamber in an undeployed state; 
         FIG. 4  is a perspective view of the rescue device including the containment chamber of  FIG. 3  in an deployed state; 
         FIG. 5  is a close-up perspective view of the containment chamber of  FIG. 4 ; 
         FIG. 6  is a perspective view of the containment chamber of  FIG. 5  with an inflatable bag disposed therein in an undeployed position; 
         FIG. 7  is a perspective view of the containment chamber of  FIG. 6  with the inflatable bag in a deployed position; 
         FIG. 8  is a side view of the rescue device of  FIG. 1  attached with a cable to an autonomous underwater vehicle; 
         FIG. 9  is a perspective view of the attached rescue device and autonomous underwater vehicle of  FIG. 8 ; and 
         FIG. 10  is a perspective view of a mechanical connection between the autonomous underwater vehicle and the cable of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Various exemplary methods and devices are provided for rescuing and recovering underwater vehicles. A person skilled in the art will appreciate that an “underwater vehicle” can include an unmanned, untethered underwater vehicle such as an Unmanned Undersea Vehicle (“UUV”) and an Autonomous Underwater Vehicle (“AUV”), and an unmanned, tethered underwater vehicle such as a Remotely Operated Underwater Vehicle (“ROV”). In one embodiment, a system is provided that includes a modular rescue device configured to attach to an underwater vehicle. The “rescue device” discussed herein can also be referred to in various embodiments as a “rescue buoy,” a “rescue vessel,” and an “emergency tow float.” The rescue device can include a tow vessel smaller in size than the underwater vehicle that can be attached to the underwater vehicle in a short amount of time and can be pulled or towed underwater by the underwater vehicle without significantly changing the underwater vehicle&#39;s operating characteristics. The rescue device can include one or more emergency mechanisms that can be automatically and/or manually activated to aid in detecting the location of the underwater vehicle in the event of an emergency, such as the underwater vehicle losing power, getting stuck or trapped in mud, rope, or other obstacle, performing outside safe operating limits, etc. One exemplary emergency mechanism includes a buoyancy mechanism, e.g., an expandable lift bag, configured to be inflated with a fluid to add buoyancy force to the system including the rescue device and underwater vehicle to pull the underwater vehicle toward a water surface. The rescue device can be configured to autonomously detect an emergency situation and deploy one or more of its emergency mechanisms, and/or the rescue device can be configured to listen for a trigger signal such as a signal from its attached underwater vehicle or a coded acoustic signal that can be sent from a distance, e.g., from above a water surface hundreds of feet away, and that can remotely signal the rescue device to deploy one or more of its emergency mechanisms. 
       FIGS. 1 and 2  illustrate one exemplary embodiment of a rescue device  10  that can be submersed under water, can be attached to an underwater vehicle, and can include one or more emergency mechanisms configured to help locate the underwater vehicle during use of the underwater vehicle. The device  10  can have a variety of shapes, sizes, and configurations. As illustrated, the device  10  includes an elongate body or housing including an emergency mechanism containment chamber  12 , a propellant chamber  14 , an electronics chamber  16 , and a nose portion  18 . Each of the chambers  12 ,  14 ,  16  and the nose portion  18  can have any size and shape and can be located anywhere in the device  10 . As illustrated, the chambers  12 ,  14 ,  16  and the nose portion  18  are longitudinally arranged along the device  10  with the containment chamber  12  at a terminal, tail end  20  of the device  10 , the nose portion  18  at a terminal, head end  22  of the device  10 , the propellant chamber  14  adjacent the containment chamber  12 , and the electronics chamber  16  disposed between the propellant chamber  14  and the nose portion  18 . The propellant and electronics chambers  14 ,  16  are preferably integrally formed together in a single housing with the containment chamber  12  removably coupled thereto, e.g., using a plurality of screws and/or other attachment mechanism. The nose portion  18  can be integrally formed with its adjacent chamber, the electronics chamber  16 , or, as illustrated, the nose portion  18  can be an independent, pressure tight element attached to the remainder of the device  10  using, e.g., a magnetic hall effect switch. The housing of the device  10  is shown as being at least partially transparent, specifically in the propellant and electronics chambers  14 ,  16 , but any portion of the housing, including the entire housing, can be opaque. The device  10  can have a substantially cylindrical shape having a substantially constant circular cross-sectional shape along a longitudinal length thereof as shown, although the device  10  can have any shape. The head end  22  of the device  10 , e.g., the nose portion  18 , can taper distally, e.g., be rounded (as shown), cone-shaped, truncated cone-shaped, etc., to help improve hydrodynamics of the device  10 . 
     The containment chamber  12  can be configured to include one or more emergency mechanisms disposed therein that can, as mentioned above, be used to help determine a location of the device  10  and hence also an underwater vehicle attached to the device  10 . The emergency mechanism(s) in the containment chamber  12  can be effective above a water surface, but as will be appreciated by a person skilled in the art, they can be particularly effective when the device  10  and the underwater device are submerged and at a location remote from a manned control center. While the device&#39;s emergency mechanisms are preferably contained within the containment chamber  12  to help protect them from the outside environment and from other components of the device  10 , one or more emergency mechanisms can be located only partially within the containment chamber  12  or not be located within the containment chamber  12  at all, e.g., be in another chamber  14 ,  16 , be coupled to an outside surface of the device  10 , etc. 
     The containment chamber  12  can include any one or more emergency mechanisms in any combination. The emergency mechanisms discussed herein are non-limiting examples only, and a person skilled in the art will appreciate that these and/or other emergency mechanisms can be disposed in the containment chamber  12  and/or disposed elsewhere within or on the device  10 . Generally, the containment chamber  12  can be associated with physical or mechanical emergency mechanisms, while the electronics chamber  16  can be associated with electronic emergency mechanisms, although any type of emergency mechanism can be located anywhere. 
     One embodiment of a physical or mechanical emergency mechanism includes a buoyancy mechanism such as a lift bag, a balloon, or other expandable member that can be contained in an unexpanded or non-deployed position at least partially inside the containment chamber  12  and that can be inflated with a fluid or otherwise expanded to increase a buoyancy of the device  10 . Generally, underwater devices can be neutrally buoyant, making them prone to becoming easily trapped or stuck underwater as they have very little upward force due to buoyancy. The device  10  attached to a neutrally buoyant underwater vehicle can also be neutrally buoyant and hydrodynamic, but it can be configured to increase its buoyancy upon deployment of the buoyancy mechanism. The buoyancy mechanism can have any size, shape, and configuration, and can be configured to provide any amount of buoyancy force when in an expanded or deployed position, e.g., at least about fourteen pounds of upward force, although the buoyancy force provided by an expanded buoyancy mechanism is preferably at least enough to pull the device  10  alone and/or the device  10  with an underwater vehicle attached thereto from underwater to the water surface. Increasing a buoyancy of the device  10  and an underwater vehicle attached thereto by at least about three orders of magnitude can provide sufficient upward force to float the device  10  and the underwater vehicle, e.g., at least about fourteen pounds of buoyancy can provide about 33% reserve buoyancy to an underwater vehicle weighing about forty-two pounds, which can be sufficient buoyancy to float the underwater vehicle. The buoyancy mechanism can be brightly colored, e.g., fluorescent, safety orange, etc., and/or have reflective properties to help improve visibility of the buoyancy mechanism from a distance. 
     Another embodiment of a physical or mechanical emergency mechanism includes a relatively long line that can be released or unspooled to allow the rescue device  10  to separate from its associated underwater vehicle if the device  10  detects or is notified that the underwater vehicle is not being pulled free after the buoyancy mechanism has been deployed. Similar to unwinding a fishing rod with a bobber attached, the long line can allow the device  10  to float to the water surface while still attached to the distressed underwater vehicle stuck underwater, thereby marking the location of the underwater vehicle. Other embodiments of physical or mechanical emergency mechanisms include flares (smoke and/or light), flags (which can be brightly colored), flashing lights located on and/or visible through the housing, and dyes configured to color water to make a large, brightly colored target for aircraft to locate. 
     The propellant chamber  14  can be configured to have a deployment mechanism disposed therein that is configured as an actuator to deploy at least one emergency mechanism. The deployment mechanism can have a variety of configurations, but in the illustrated exemplary embodiment the deployment mechanism includes at least one propellant contained within at least one propellant container  24  within the propellant chamber  14 . The propellant container  24  can be in selective fluid communication with the containment chamber  12  such that at least a portion of the propellant disposed in the propellant chamber  14  can be introduced into the containment chamber  12  to deploy at least one emergency mechanism disposed therein. Any fluid or solid propellant can be used, e.g., a gas such as carbon dioxide, a refrigerant such as R134a (tetrafluoroethane), and an explosive powder. R134a has a much lower vapor pressure compared to carbon dioxide and can thus be particularly effective in relatively shallow water (up to about 200 feet), while carbon dioxide can be particularly effective in deep water (up to about 2000 feet). Explosive powder can be particularly effective at very deep depths (over about 2000 feet). The propellant chamber  14  preferably has one propellant loaded therein, but the propellant chamber  14  can be configured to contain a plurality of propellants that can be selectively deployed at different depths depending on the propellant&#39;s effectiveness at the depth of the device  10  when an emergency mechanism is deployed. 
       FIGS. 3-5  illustrate one embodiment of the containment chamber  12  configured to receive an inflatable bag in an opening  28  formed in the containment chamber  12 , with the propellant chamber  14  configured to deploy the bag from the containment chamber  12 . The containment chamber  12  can have a variety of configurations, but as shown, the containment chamber  12  includes a cylindrical housing  32  configured to have disposed therein a piston assembly  30  having opposed arms  30   a  that define the opening  28 . To arm the device  10  with the bag disposed in the opening  28 , the containment chamber  12  can be moved from an undeployed position, shown in  FIG. 3 , to a deployed position, shown in  FIGS. 4 and 5 , by ejecting the piston assembly  30  from the cylindrical housing  32  to provide better access to an interior of the containment chamber  12 . The piston assembly  30  can be manually and/or electronically ejected from the cylindrical housing  32  in any way, as will be appreciated by a person skilled in the art, such as by unscrewing screws  38  attaching the containment chamber  12  via a release plug  34  to the propellant chamber  14 . Ejecting the piston assembly  30  can proximally move the piston assembly  30  to extend beyond the tail end  20  of the device  10  to expose a tube fitting  36 . The piston assembly  30  can remain coupled to the containment chamber  12  in its deployed position by being coupled to the release plug  34 , which can be coupled to a coupling mechanism such as an expandable rod  42  or a spring configured to extend between the release plug  34  and a distal portion of the cylindrical housing  32 . 
     The bag can be coupled with the tube fitting  36  by, e.g., inserting a fill tube of the bag within the tube fitting  36  of the piston assembly  30  and positioning the bag within the opening  28  between the opposed arms  30   a  of the piston assembly  30 . The bag is preferably tightly wound or otherwise compressed into a fully unexpanded configuration before the bag is coupled to the containment chamber  12 , which can help reduce a volume of the bag disposed in the containment chamber  12 . As will be appreciated by a person skilled in the art, the tube fitting  36  and the fill tube can be secured together using a locking mechanism, e.g., corresponding threads on the tube fitting  36  and the fill tube, a latch, etc., to help keep the bag connected to the device  10  when the bag is deployed.  FIG. 6  illustrates an exemplary embodiment of an inflatable bag  44  connected to the tube fitting  36  and disposed in the opening  28  in an undeployed position. 
     With the containment chamber  12  in the deployed position, a fill plug  40  can be exposed. The fill plug  40  can be at least partially removed to provide access to the propellant container  24  within the propellant chamber  14 . A propellant configured to deploy the bag disposed in the containment chamber  12  can be loaded into the propellant chamber  14  through an opening exposed by removing the fill plug  40 . The propellant container  24  can include at least one visible fill line, and propellant can be added to the propellant container  24  until the fill line is reached. With a desired amount of propellant added to the propellant chamber  14 , the fill plug  40  can be reattached, thereby sealing the propellant container  24  and allowing it to pressurize to a vapor pressure of the propellant contained therein. The propellant chamber  14  can optionally include a pressure gauge configured to allow display or other notification of a pressure of propellant contained within the propellant chamber  14  to help inform a user whether the propellant is at a safe and effective pressure. Propellant can be loaded into the propellant chamber  14  before and/or after the bag is loaded into the opening  28 . Before the device  10  is turned on, e.g., by supplying a 5.5-30 Volt DC power source included in the electronics chamber  16  and placing a magnet over the device&#39;s hall effect switch, the propellant can be prevented from deploying the bag, and any other emergency mechanisms can also be prevented from deploying. 
     With the bag attached to the piston assembly  30  and propellant loaded into the propellant chamber  14 , the piston assembly  30  can be reinserted into the cylindrical housing  32  by, e.g., distally pushing the piston assembly  30 . The release plug  34  can also be reattached to the propellant chamber  14  using the screws  38 , thereby securing the bag within the containment chamber  12  until it is deployed. The electronics chamber  16  can include a buzzer configured to signal a user that the bag contained in the containment chamber  12  has been properly configured and is ready for deployment upon appropriate trigger if it is not first deactivated by, e.g., manual intervention by a user. To help release at least a portion of the propellant from the propellant chamber  14  into the bag to deploy the bag by e.g., moving the containment chamber  12  from the undeployed position to the deployed position, the tube fitting  36  can be configured with a releasable mechanism, e.g., a valve, that can be triggered open upon appropriate actuation signal from the electronics chamber  16 . Non-limiting examples of various ways to automatically inflate a bag using a propellant can be found in U.S. Pat. No. 4,482,333 issued Nov. 13, 1984 and titled “Automatic Inflation System,” which is hereby incorporated by reference in its entirety.  FIG. 7  shows the bag  44  in a deployed position following inflation of the bag  44  with a propellant delivered from the propellant chamber  14  to an internal cavity of the bag  44  through the tube fitting  36 . 
     Referring again to  FIGS. 1 and 2 , the propellant chamber  14  can be in electronic communication (wireless and/or wired) with the electronics chamber  16 , which can allow the electronics chamber  16  to trigger the propellant chamber  14  with a signal indicating when to “fire” or otherwise release a propellant disposed therein to deploy an emergency mechanism. Accordingly, a signal from the electronics chamber  16  can be effective as an actuator to deploy an emergency mechanism. The electronics chamber  16  can have a variety of configurations. In an exemplary embodiment, the electronics chamber  16  includes a processor such as a PIC microcontroller available from Microchip Technology Inc. of Chandler, Ariz., configured to process instructions related to, e.g., control of various aspects of the device  10  such as deployment of emergency mechanisms and communication with remote equipment at, e.g., at a land or boat-based control station. A microcontroller processes instructions in this embodiment, but any one or more processors configured to process instructions for a system, e.g., a central processing unit, a microprocessor, a digital signal processing unit, application specific integrated circuits (“ASIC”), a state machine, logic circuitry, etc., can be included in the device  10  to control various aspects of the device  10 . 
     The electronics chamber  16  can be powered in any number of ways. The electronics chamber  16  can be externally powered by being in electronic communication with an underwater vehicle attached to the device  10 , as discussed further below, and receive power from the underwater vehicle. Alternatively or in addition, the electronics chamber  16  can include an internal power source, e.g., a DC battery a providing a voltage in a range of about 5.5 to 30 volts. One or more lights, e.g., light emitting diodes, attached to an outside surface of the housing and/or disposed in and visible through the electronics chamber  16  or other portion of the device  10  can indicate an operating state of the device  10 , such as the device&#39;s current power source, low power, deployment of an emergency mechanism, etc. The electronics chamber  16  can also include and/or control one or more display monitors disposed on or visible through the housing. The display monitor(s) can display past, present, and/or future operating characteristics of the device  10  and/or the underwater vehicle attached thereto. Any one or more operating characteristics can be displayed, such as an available amount of reserve power that can be provided by the device  10  and a depth of the device  10 . 
     The electronics chamber  16  can also include at least one electronic emergency mechanism, although the electronics chamber  16  can additionally or alternatively include a physical emergency mechanism, as mentioned above. One example of an electronic emergency mechanism includes a sensor configured to detect an emergency event. The sensor can be configured to detect an emergency event by monitoring one or more conditions related to the device  10  and/or the underwater vehicle to which the device  10  is attached and to trigger an appropriate distress action upon detection of an emergency event, e.g., deploy an emergency mechanism, send a distress signal, etc. Alternatively or in addition, the sensor can be configured as a receiver to detect an emergency event by receiving a wired or wireless acoustic or other electronic signal from the underwater vehicle attached to the device  10  and/or from a remotely located control station indicating the occurrence of an emergency event, and the sensor can be configured to trigger an appropriate distress action in response. The device  10  can include one or more sensors, and each sensor can be configured to detect one or more emergency events indicating distress of the underwater vehicle attached to the device  10 . Moreover, an underwater vehicle attached to the device  10  can include one or more sensors in addition or in alternative to sensor(s) in the device  10  and can be configured to be in electronic communication with the device  10  to trigger an appropriate distress action. 
     A person skilled in the art will appreciate that various types of sensors can be used. One example of sensor includes a power detector configured to detect a power loss in the underwater vehicle attached to the device  10 . Upon detection of a power loss, the sensor can trigger activation of a reserve power supply included in the electronics chamber  16  configured to supply power to the underwater vehicle. Any reserve power supply, e.g., batteries, super capacitors, etc., configured to provide any amount of power, e.g., at least about fifteen Farads, etc., can be used, but the amount of reserve power carried by the device  10  is preferably at least an amount of power necessary to deploy the buoyancy mechanism in the containment chamber  12  and to run any signaling equipment configured to contact a remotely located control station. Another example of a sensor includes a depth or pressure sensor configured to measure depth of the device  10  and/or its attached underwater vehicle. The depth sensor can be configured to arm only after the underwater vehicle is under the water and/or can be configured to detect when the underwater vehicle is operating unsafely, e.g., diving too quickly, diving too deep, etc. Another example of a sensor includes a time sensor configured to detect when the underwater vehicle attached to the device  10  has been underwater for a time exceeding a predetermined threshold time programmed into the processor in the electronics chamber  16  that indicates a maximum safe operating time, such as a time after which the underwater vehicle should be retrieved to, e.g., ensure that the underwater vehicle has adequate power to resurface. Yet another example of a sensor includes a tilt sensor configured to detect if the device  10  is tilting head-first above a predetermined threshold angle programmed into the processor in the electronics chamber  16  that indicates a maximum safe operating angle. If the device  10  is slightly positively buoyant as indicated by meeting or exceeding the threshold angle, this can signify that the underwater vehicle attached to the device  10  is stopped and that the device  10  is floating up with its head end  22 , connected to the underwater vehicle, pointed down. Still another example of a sensor includes a speed sensor configured to detect if a speed of the underwater vehicle attached to the device  10  has fallen below a predetermined threshold minimum speed, thereby indicating that the underwater vehicle is disabled, stuck, or otherwise in distress, and/or if the underwater vehicle&#39;s speed has exceeded a predetermined threshold maximum speed, thereby indicating an undesirable operating condition that could negatively impact functionality of the underwater vehicle. In addition, the sensor could be a timer—if the mission exceeds a preset maximum time limit a rescue could be indicated. 
     Another example of an electronic emergency mechanism includes a communications link, e.g., a radio link, a satellite link, an underwater acoustic transmitter link, etc., configured similar to a marine Emergency Position-Indicating Radio Beacon (“EPIRB”). The communications link can be configured to communicate a position of the device  10  to a remote location using a global positioning system (“GPS”) or other positioning system. The communications link can be configured to transmit a position upon any trigger, such as by receiving a trigger signal from a sensor to communicate the device&#39;s and/or underwater vehicle&#39;s position upon the sensor&#39;s detection of an emergency event. The position communication can occur immediately upon receipt of a trigger signal or after a time delay, such as after the device  10  has buoyed to the water surface following deployment of an inflatable bag from the containment chamber  12 . In some embodiments, the position communicated over the communications link can trigger a distress action if, e.g., the device  10  has strayed outside a preprogrammed area. 
     In addition or as an alternative to the communication link, the nose portion  18  of the device  10  can include a location identifying mechanism, such as an acoustic pinger  26  configured to send a long range acoustic signal through water, to signal a location of the device  10 . In an exemplary embodiment the pinger  26  can continuously ping at defined intervals to signal the device&#39;s location once the device  10  has dived beyond a threshold depth and/or has been deployed for a threshold amount of deployed time. The pinger  26  can ping at any frequency or rate, e.g., at about 10 kHz. 
     The processor in the electronics chamber  16  can be preprogrammed before deployment of the device  10  underwater. As will be appreciated by a person skilled in the art, the processor can be programmed in any way, such as by using an RS-232 terminal, e.g., a stationary or laptop computer running Windows Hyperterm (HyperTerminal™ available from Microsoft Corp. of Redmond, Wash. or Hilgraeve, Inc. of Monroe, Mich.), to store one or more parameters in a memory mechanism configured to be accessible by the processor. Any type of memory can be used for the memory mechanism, including but not limited to one or more of volatile (e.g., SRAM, etc.), non-volatile (e.g., flash, hard drive, etc.), or other memory. A non-volatile memory can retain programmed parameters following device shut-off so that programmed parameters need not be re-entered if the device  10  is power cycled. 
     Various parameters can be preprogrammed into the processor. One exemplary programmable parameter includes an emergency mechanism deployment delay time that can indicate a time between detection of an emergency event and when an emergency mechanism such as inflation of a buoyancy mechanism or sending of a distress signal should be deployed in response to the detection. Using the emergency mechanism deployment delay time can serve as a safety feature to prevent premature deployment of an emergency mechanism if, for example, the underwater vehicle attached to the device  10  becomes stuck in mud but is able to dislodge itself under its own power. Another exemplary programmable parameter includes an armed depth, which can indicate a depth below which the device  10  will enable at least one and preferably all of its emergency mechanism rescue features. Having an armed depth above which emergency mechanisms will not be deployable can help eliminate erroneous implementation of the device&#39;s rescue features on the surface and can act as a safety interlock for users. Yet another exemplary programmable parameter includes a threshold depth above which the device  10  will automatically deploy at least one emergency mechanism because the device  10  has exceeded a maximum desirable depth. Another exemplary programmable parameter includes a power management feature to indicate which one or more features of the device  10  to deactivate or turn off during non-emergency operation of the device  10  in order to conserve power. Any one or more features of the device  10  can be “flagged” for non-emergency shut-off using the power management feature, such as the pinger  26 , a driver or receiver interface between the processor and RS-232 terminal such as a MAX232 (available from Maxim Integrated Products of Sunnyvale, Calif.) or other integrated circuit, lights, display monitors, etc. 
     The rescue device  10  can be fixedly or removably attached in any way to an underwater vehicle. The underwater vehicle can be configured to attach to the device  10 , or because the device  10  is modular, the device  10  can attach to an existing underwater vehicle without requiring much if any modification to the existing underwater vehicle. In some embodiments, the device  10  can fixedly or removably attach to an underwater vehicle with a cable or tow line extending between the head end  22  of the device  10  and a tail end of the underwater vehicle, which can allow the device  10  to be disposed outside the underwater vehicle and be towed behind the underwater vehicle when the underwater vehicle is in motion underwater, traditionally at a speed in a range of about one to four knots. In some embodiments, the device  10  can be fixedly or removably attached to an outside surface of an underwater vehicle using any one or more attachment mechanisms, e.g., bolts, clamps, screws, welding, etc., as will be appreciated by a person skilled in the art. The device  10  can be fully or partially disposed outside the underwater vehicle when attached to an outside surface thereto. Attaching the device  10  to an outside surface of the underwater vehicle can help reduce chances of the device  10  becoming accidentally detached from the underwater vehicle and/or the tow line extending between the device  10  and the underwater vehicle becoming tangled, severed, or otherwise disabled to diminish or eliminate effective operation of the device  10  and/or the underwater vehicle. 
     In an exemplary embodiment of the rescue device  10  attached to an underwater vehicle illustrated in  FIGS. 8-10 , the device  10  can be attached to an AUV  50 , e.g., a 42 pound Iver2AUV available from OceanServer Technology, Inc. of Fall River, Mass., with a cable  52  extending between the head end  22  of the device  10  and a tail end  54  of the AUV  50 . The cable  52  can have any size, shape, and configuration. In the illustrated embodiment, the cable  52  has a fixed length in a range of about 2 to 4 feet, but the cable  52  can have any fixed or variable length. For example, in another embodiment, a variable length cable extending between the device  10  and the AUV  50  can be at least partially spooled or coiled inside the body of the device  10  and/or the AUV  50 . Non-limiting examples of a various reeling systems can be found in U.S. Pat. No. 3,961,589 issued Jun. 8, 1976 and titled “Buoyant Cable Antenna Reeling System,” which is hereby incorporated by reference in its entirety. In this way, in the event of an emergency, the cable can act as a relatively long line that can be payed out from within the device  10  and/or the AUV  50  to allow the device  10  to rise to the water surface if the AUV  50  is unable to be released from a stuck position with increased buoyancy provided by the device  10 , if the device  10  cannot properly deploy an emergency mechanism, or if any other problem is encountered in rescuing the AUV  50 . Any length of cable can be spooled inside the device  10  and/or the AUV  50 , e.g., about 600 feet, but it is preferably a length much longer than a length of unspooled cable extending between the device  10  and the AUV  50  to allow the device  10  to float a large distance away from the AUV  50  and reach a water surface when the cable  10  is at least partially unspooled. 
     The cable  52  can be attached to the device  10  and to the AUV  50  in any way, as will be appreciated by a person skilled in the art. As illustrated, the cable  52  includes a mechanical connection element  56  configured to mechanically couple the cable  52  to the AUV  50  at the AUV&#39;s tail end  54  using an attachment mechanism, e.g., bolts, screws (as shown), clamps, welding, etc. The mechanical connection element  56  can include a plurality of connection elements, as illustrated, to help support tension placed on the cable  52  by the device  10  when the AUV  50  is in motion and towing the device  10 , although tension can be supported in any way appreciated by a person skilled in the art. The cable  52  can also include an electrical connection element  58  configured to electrically couple the cable  52  to the AUV  50  to allow electrical communication between the AUV  50  and the device  10  for powering purposes, for signaling between the device  10  and the AUV  50 , etc. The electrical connection element  58  can include a waterproof electrical connector, such as an underwater pluggable connector available from 
     Impulse Enterprise of San Diego, Calif. or a Subconn® Underwater Connector available from Subconn Inc. of Burwell, Nebr. Electrical communication between the device  10  and the AUV  50  can be achieved in any way appreciated by a person skilled in the art, such as via a wire or fiber included in the cable  52 . The mechanical and electrical connection elements  56 ,  58  separately attach to the AUV  50 , but a person skilled in the art will appreciate that they can connect to the AUV  50  in any way, including singularly. 
     A person of ordinary skill in the art will recognize that features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. A person of ordinary skill in the art will also appreciate further features and advantages of the invention based on the above-described embodiments. For example, specific features from any of the embodiments described above may be incorporated into devices or methods of the invention in a variety of combinations and subcombinations, as well as features referred to in the claims below which may be implemented by means described herein. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims or those ultimately provided. Any publications and references cited herein are expressly incorporated herein by reference in their entirety.