Abstract:
An AUV is described that includes an external, deployable payload releasably attached to the exterior of the AUV. The release mechanism between the payload and the AUV is relatively simple and low cost. The payload is mounted external to the AUVs hull and does not significantly increase the cost of the AUV to which it is attached. There are no complex release mechanisms or intermediate launch systems attached to the AUV. Therefore, the described AUV can deploy payloads, such as sensors, that would normally be deployed from a manned platform. This can increase the payload capability of a small expendable AUV without increasing volume or cost of the AUV.

Description:
FIELD 
       [0001]    This disclosure relates to carrying and deploying diverse payloads from an underwater vehicle such as an autonomous underwater vehicle (AUV). 
       BACKGROUND 
       [0002]    AUVs have become a cost-effective alternative to deep sea manned and unmanned tethered technologies. The demand for AUVs carrying diverse payloads has increased the costs of AUVs. A trend has been to develop larger AUVs capable of carrying diverse payloads which increase the size and cost of the AUV proportionally. 
         [0003]    In addition, releasing payloads from an AUV underwater is a difficult and expensive task. Releasing or deploying payloads from AUVs underwater has generally been done by stowing the payload inside the AUV&#39;s hull. A port in the side of the hull opens and communicates to the ocean and releases the payload. Other AUV designs have launch tubes and or docking stations mounted to the exterior of the hull. The launch tubes and docking stations tend to be much smaller compared to the AUV and thus they have minimal impact on the buoyancy of the AUV. In addition, these are very complex and expensive solutions utilized in reusable AUV applications. 
         [0004]    In addition, it is sometimes desirable to create a stand-off distance between the AUV and the payload once the payload is released. 
       SUMMARY 
       [0005]    An AUV is described that includes an external, deployable unmanned payload releasably attached to the exterior of the AUV. The release mechanism between the payload and the AUV is relatively simple and low cost. The payload is mounted external to the AUVs hull and does not significantly increase the cost of the AUV to which it is attached. There are no complex release mechanisms or intermediate launch systems attached to the AUV. Therefore, the described AUV can deploy payloads, including but not limited to sensors, that would normally be deployed from a manned platform. This can increase the payload capability of a small expendable AUV without increasing volume or cost of the AUV. In one embodiment, the external payload is approximately the same size as the AUV so that the buoyancy of the AUV is changed. 
         [0006]    The deployable unmanned payload has its own contained displaced volume, therefore it does not disturb the volume of the AUV. The payload is a structure that is separate from the AUV, and is not a part or sub-part of the AUV, so that the displaced volume of the AUV remains the same before and after release of the payload from the AUV. Once the payload is released, the AUV is capable of continuing on its mission, for example by traveling to a new location which helps to create a stand-off distance between the AUV and the released payload. In another embodiment, the payload can be deployed and towed like a tethered body from the AUV. In still another embodiment, a standoff distance can be created between the manned or unmanned platform, whether aerial, surface or sub-surface, that the AUV is launched from. 
         [0007]    In one embodiment, releasing the external payload is achieved with a burn wire mechanism that contributes to securing the external payload to the AUV. The burn wire mechanism includes a burn wire that is programmed to burn at a predetermined time during the mission. At the appropriate time, electricity is sent through the burn wire, and the burn wire heats up and breaks. When the burn wire breaks, the external payload(s) is released and the AUV reverts back to its original intended state to continue its mission. Other forms of release mechanisms can be used as well. 
         [0008]    The embodiments described herein create a method to use an expendable AUV that is designed for a single mission to carry diverse payloads to extend the capability of the AUV for many different missions. However, the AUV does not need to be expendable. Rather, the AUV can be re-used after it releases the payload. 
         [0009]    The payload can also be expendable or the payload can be re-useable. 
         [0010]    In addition, in another embodiment, the AUV can carry multiple external payloads, with the payloads being the same as or different from one another, and with each payload being separately or jointly releasable from the AUV. 
         [0011]    As used herein, an AUV can be any unmanned underwater vehicle designed to operate underwater. The term “unmanned” means the AUV (and the payload) does not physically carry a human operator. In some embodiments, the AUV can be completely autonomous so that its operation is preprogrammed with no remote human control or operational intervention. In another embodiment, the AUV can be semi-autonomous so that some or all of its operation is controlled remotely by one or more human operators. 
         [0012]    In one embodiment, the external payload is attached to the outside of the AUV in a vertically stacked or a horizontal side-by-side configuration. In other embodiments, the external payload can be attached to the front or rear of the AUV in a generally collinear arrangement. 
         [0013]    The payload can be a generally cylindrical body to maximize hydrodynamic efficiency. However, other payload shapes can be used as well. 
         [0014]    In one embodiment, the payload can be in the form of optional external ballast, including but not limited to ballast weights, that can be used as needed, for example to adjust the weight distribution of the AUV-payload combination. The ballast payload can be separate from both the AUV and other payload(s) and can be released when the other payload(s) is released, or released separately from the AUV. 
         [0015]    The payload may be a completely autonomous system separate from the AUV, or the payload can communicate by suitable communication technology including but not limited to, wirelessly, using a tether line or other communication technology, with the AUV to transfer data and power. 
         [0016]    In one embodiment, a combination comprises an autonomous underwater vehicle with an exterior surface and a displaced volume, and an external payload is releasably deployable from the autonomous underwater vehicle. The external payload is releasably connected to the exterior surface of the autonomous underwater vehicle by a releasable mechanism, and the displaced volume of the autonomous underwater vehicle remains the same before and after release of the external payload. While the combination is submerged under water, the external payload can be deployed from the autonomous underwater vehicle by releasing the releasable mechanism. 
         [0017]    In another embodiment, a method of deploying a payload in water comprises releasably mounting a payload to an exterior of an autonomous underwater vehicle having a displaced volume. The autonomous underwater vehicle with the payload mounted thereto into water is launched into the water. While the autonomous underwater vehicle and the payload are submerged under the water, the payload is released from the autonomous underwater vehicle so that the displaced volume of the autonomous underwater vehicle remains the same after release of the payload. 
     
    
     
       DRAWINGS 
         [0018]      FIG. 1  is a side view of an AUV carrying an external, deployable payload. 
           [0019]      FIG. 2  is a detailed view of a portion of the AUV showing one form of releasable connection between the AUV and the external payload. 
           [0020]      FIG. 3  is a close-up view of a portion of the payload support on the AUV. 
           [0021]      FIG. 4  is a perspective view of another embodiment of an AUV carrying an external, deployable payload in the form of an expendable ballast tank. 
           [0022]      FIG. 5  is a cross-sectional side view of the expendable ballast tank of  FIG. 4 . 
           [0023]      FIG. 6  is a side view of the AUV together with the expendable ballast tank in cross-section showing operation of the expendable ballast tank. 
           [0024]      FIGS. 7A-D  illustrates an example sequence of operation of the AUV and release of the expendable ballast tank therefrom. 
           [0025]      FIGS. 8A-C  illustrate an example of a launch kit that can be used to launch the AUV and the external payload attached thereto from a launch platform such as a submarine. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  shows a side view of an AUV  10  carrying an external, deployable unmanned payload  12 . The AUV  10  is of generally conventional construction known in the art including a cylindrical hull  14 , a hydro-dynamically shaped, for example bullet shaped, forward end  16 , and an aft end  18  containing a propulsion mechanism  20 , such as a propeller  22  (best seen in  FIG. 2 ) driven by a motor  24  (shown in dashed lines in  FIG. 1 ), for propelling the AUV  10  through the water. The AUV  10  can also include a steering mechanism, separate from or integral with the propulsion mechanism, for example steerable fins  26  (best seen in  FIG. 2 ) or the propulsion mechanism  20  can be steerable to function as the steering mechanism. 
         [0027]    The AUV  10  can also include a suitable power supply  28  (shown in dashed lines in  FIG. 1 ), for example one or more batteries, disposed within the hull  14  for providing power to the AUV  10  and optionally provide power to the payload  12 . Suitable control electronics for controlling operation of the AUV  10  can also be disposed within the hull  14 . 
         [0028]    The AUV  10  can also carry one or more mission specific packages  30  (shown in dashed lines in  FIG. 1 ) suitable for its intended mission. Examples of mission specific packages include, but are not limited to, various sensor packages, sonar packages, munitions packages, communications packages, and the like. 
         [0029]    With reference to  FIG. 1 , the payload  12  is illustrated as being releasably mounted on the AUV  10  in a vertically stacked configuration. However, the payload  12  and the AUV  10  can be arranged in a horizontal side-by-side configuration as well, or in any other configuration where the payload  12  is mounted external to the hull  14  of the AUV  10 . Using a vertically stacked arrangement is easier to implement since the disruption to the hydrodynamics of the AUV  10  are easier to compensate for. In some embodiments, the payload  12  can be mounted to the forward end  16  or to the aft end  18  of the AUV  10  in a generally collinear arrangement. 
         [0030]    As shown in  FIG. 1 , the AUV  10  includes a first longitudinal axis X-X, and the payload  12  includes a second longitudinal axis Y-Y. In the vertically stacked configuration illustrated in  FIG. 1 , as well as in a horizontal side-by-side configuration, the axes X-X and Y-Y are parallel to one another but offset from each other. In another embodiment where the payload  12  and the AUV  10  are in a generally collinear arrangement, the axis X-X will be generally parallel to and generally collinear with the axis Y-Y. 
         [0031]    To be more hydro-dynamically efficient, the payload  12  is illustrated in  FIG. 1  as having a cylindrical configuration with a generally cylindrical hull  32  having a hydro-dynamically shaped, such as bullet shaped, forward end  34  and an aft end  36 . In the illustrated embodiment, the payload  12  does not have a separate propulsion mechanism or steering capability. Therefore, when the payload  12  is released from the AUV  10 , the payload  12  is intended to float submerged under the water, float at the surface of the water, and/or sink to the bottom, depending upon the buoyancy characteristics of the payload  12  and its intended mission. 
         [0032]    In some embodiments, the buoyancy characteristics of the payload  12  can be controlled so that the payload can selectively achieve multiple positions in the water during its mission. For example, the buoyancy of the payload  12  can be controlled so that the payload is initially floating submerged in the water, then the buoyancy is changed so that the payload  12  floats at or near the surface of the water, and then the buoyancy is changed again so that the payload sinks to the bottom. Other multiple position schemes can be achieved by changing the buoyancy of the payload  12 . 
         [0033]    The payload  12  can carry its own internal power supply  38  (illustrated in dashed lines in  FIG. 1 ), such as one or more batteries, which provide power to the payload  12 . In one embodiment, the payload power supply  38  can supply all of the power the payload  12  requires while it is attached to the AUV  10 . In another embodiment, the payload power supply  38  can supply some power to the payload  12  while the power supply  28  of the AUV  10  supplies some power to the payload  12  while the two are attached. In still another embodiment, the AUV power supply  28  can supply all power to the payload  12  while the two are attached to avoid draining the payload power supply  38 . 
         [0034]    Once the payload  12  separates from the AUV  10 , the payload power supply  38  can supply all of the power the payload  12  requires. In another embodiment, power can be supplied to the payload  12  via a tether (not shown) that connects the AUV  10  and the payload  12  even after the payload  12  separates from the AUV  10 . 
         [0035]    Likewise, while attached, the payload  12  may communicate using a suitable communication technique, for example wirelessly or using a tether line, with the AUV  10  to transfer data to and from the AUV  10 . In addition, after separation, the payload  12  may communicate using a suitable communication technique, for example wirelessly or using a tether line, with the AUV  10  to transfer data to and from the AUV  10 . 
         [0036]    The payload  12  can carry one or more mission specific packages  40  suitable for its intended mission. Examples of mission specific packages  40  include, but are not limited to, various sensor packages, sonar packages, munitions packages, communications packages for transmitting and/or receiving signals, and the like. The payload  12  can also have data processing capability provided by one or more data processors. In one embodiment, the payload  12  is a sensor payload that contains one or more sensor packages designed to perform a sensing mission at its deployed location. In another embodiment, the payload can be a payload launch system that launches a specific payload. 
         [0037]    In one embodiment, the payload  12  can include control surfaces including, but not limited to, controllable steering fins, or other steering capability. It is preferred that the payload not include its own propulsion mechanism, although in some embodiments the payload  12  can include a propulsion mechanism. 
         [0038]    The payload  12  is a structure that is separate from the AUV  10 , and is not a part or sub-part of the AUV  10 . As a result, the displaced volume of the AUV  10  remains the same before and after release of the payload  12  from the AUV  10 . 
         [0039]    Referring to  FIGS. 1 and 3 , one or more payload supports  42  are fastened to the AUV  10 , for example on the exterior surface of the hull  14 . In the illustrated example, there are two payload supports  42 , one support  42  supporting a forward end of the payload  12 , and one support  42  supporting a rear end of the payload  12 . The payload supports  42  passively support the payload  12  on the AUV  10  without fastening the payload  12  to the AUV  10  so that, absent other means for securing the payload  12  to the AUV  10 , the payload  12  can freely separate from the payload supports  42 . In the illustrated example, each payload support  42  comprises a curved support bracket that generally matches the curvature of the cylindrical hull  32  of the payload  12  so that the payload  12  rests on the curved brackets when the payload  12  is attached to the AUV  10 . However, other payload support configurations can be used. 
         [0040]    Referring to  FIGS. 1 and 2 , a releasable mechanism  44  releasably fastens the payload  12  on the AUV  10 . Any releasable mechanism  44  that can retain the payload  12  on the AUV  10 , and that can be actuated to release the payload  12  from the AUV  10 , can be used. 
         [0041]    In the illustrated embodiment, the releasable mechanism  44  comprises a one-piece wire  46  that crosses over the payload  12 , around one of the payload supports  42 , and attaches at its free ends  48   a,    48   b  to a burn wire  50  as best seen in  FIG. 2 . The burn wire  50  is illustrated in  FIG. 2  as being located on the outside of the hull  14  of the AUV  10 . However, the burn wire  50  can be disposed inside the hull  14  as long as the ends  48   a ,  48   b  can be released to permit release of the payload  12 . In addition, the burn wire  50  could be located on the payload  12  to initiate release via the payload  12  rather than via the AUV  10 . 
         [0042]    The one-piece wire  46  is sufficient to retain the payload  12  on the AUV  10  during typical anticipated use. To release the payload  12 , electricity is sent through the burn wire  50  which causes the burn wire  50  to heat up and break. When the burn wire  50  breaks, the ends  48   a,    48   b  of the wire  46  are released, which releases the external payload  12  and any external ballast  52  (if used). One advantage of using the external ballast  52  is that neither the AUV  10  nor the payload  12  needs to be modified for ballast. Also, the payload  12  could remain buoyant if needed and the ballast  52  can be jettisoned with the payload  12  from the AUV  10 , leaving the AUV  10  and the payload  12  properly trimmed to continue with their respective missions. 
         [0043]    After release of the payload  12 , the AUV  10  can continue its mission and travel away from the released payload  12 . Thus, a stand-off distance can be created between the AUV  10  and the released payload  12 . In addition, a standoff distance is created between the manned or unmanned platform, whether aerial, surface or sub-surface, that the AUV  10  and payload  12  attached thereto are launched from. 
         [0044]      FIGS. 4-6  illustrate another example of an AUV  100  with an external, deployable unmanned payload which in this example is an external, deployable, expendable ballast tank  102 . The use of an expendable ballast tank  102  as the payload creates additional mission opportunities. For example, in one embodiment, after launching the AUV  100  with the expendable ballast tank  102 , the AUV  100  can remain dormant, with the expendable ballast tank  102  controlling and maintaining a predetermined depth of the AUV  100 . The AUV  100  and ballast tank  102  can then loiter and drift for a predetermined period time, such as hours, days, weeks, etc. until the predetermined time period is met. The expendable ballast tank  102  can then be detached from the AUV  100  at which point the AUV  100  becomes active and begins its mission. 
         [0045]    As will be discussed further below, the AUV  100  and the ballast tank  102  can be releasably attached together using a suitable releasable mechanism, such as the single wire  46  concept discussed above for  FIGS. 1-3 . However, as discussed below, in this embodiment the burn wire for initiating release can be located on the ballast tank  102 . 
         [0046]    With reference to  FIG. 4 , the AUV  100  is of generally conventional construction known in the art including a cylindrical hull  104 , a hydro-dynamically shaped, for example bullet shaped, forward end  106 , and an aft end  108  containing a propulsion mechanism  110 , such as a propeller  112  (best seen in  FIG. 4 ) driven by a motor  114  (shown in dashed lines in  FIG. 4 ), for propelling the AUV  100  through the water. The AUV  100  can also include a steering mechanism, separate from or integral with the propulsion mechanism  110 , for example steerable fins  116  (best seen in  FIG. 4 ) or the propulsion mechanism  110  can be steerable to function as the steering mechanism. 
         [0047]    The AUV  100  will also include a suitable power supply  118  (shown in dashed lines in  FIG. 4 ), for example one or more batteries, disposed within the hull  104  for providing power to the AUV  100  and optionally provide power to the ballast tank  102 . Suitable control electronics for controlling operation of the AUV  100  can also be disposed within the hull  104 . 
         [0048]    The AUV  100  can also carry one or more mission specific packages  120  (shown in dashed lines in  FIG. 4 ) suitable for its intended mission. Examples of mission specific packages include, but are not limited to, various sensor packages, sonar packages, munitions packages, communications packages, and the like. 
         [0049]    With reference to  FIGS. 4-6 , the ballast tank  102  is illustrated as being releasably mounted on the AUV  100  in a vertically stacked configuration. However, the ballast tank  102  and the AUV  100  can be arranged in a horizontal side-by-side configuration as well, or in any other configuration where the ballast tank  102  is mounted external to the hull  104  of the AUV  100 . Using a vertically stacked arrangement is easier to implement since the disruption to the hydrodynamics of the AUV  100  are easier to compensate for. 
         [0050]    As shown in  FIG. 6 , the AUV  100  includes a first longitudinal axis X-X, and the ballast tank  102  includes a second longitudinal axis Y-Y. In the vertically stacked configuration illustrated in  FIG. 6 , as well as in a horizontal side-by-side configuration, the axes X-X and Y-Y are parallel to one another but offset from each other. 
         [0051]    To be more hydro-dynamically efficient, the ballast tank  102  is illustrated in  FIG. 4-6  as having a cylindrical configuration with a generally cylindrical hull  122  having a hydro-dynamically shaped, such as bullet shaped, forward end  124  and a hydro-dynamically shaped, such as bullet shaped, aft end  126 . In the illustrated embodiment, the ballast tank  102  does not have a separate propulsion mechanism or steering capability. Therefore, when the ballast tank  102  is released from the AUV  100 , the ballast tank  102  is intended to float submerged under the water, float at or near the surface of the water, and/or sink to the bottom, depending upon the buoyancy characteristics of the ballast tank  102  and its intended mission. 
         [0052]    The ballast tank  102  is designed to permit its buoyancy characteristics to be selectively controlled. In particular, referring to  FIG. 5 , the ballast tank  102  includes a first section  130  that, during use, defines a dry section that is sealed to prevent ingress of water into the first section  130 . The first section  130  includes one or more batteries  132  that provide power to various components of the ballast tank  102 , control electronics  134  that control operation of the ballast tank  102 , and a pressure transducer  136  that senses the pressure of outside water acting on the forward end  124  which is used to determine depth of the ballast tank  102  in the water. 
         [0053]    With continued reference to  FIG. 5 , the ballast tank  102  also includes a generally hollow, second section  140  to the rear of the first section  130 . The section  140  is a generally hollow portion of the hull  122 . The section  140  can be considered a wet section that allows ingress and egress of water therefrom via a plurality of openings  142  formed in the hull  122 . At the upper end of the hull  122 , an air exit opening  144  is formed in the section  140 , with air flow through the opening  144  to an air outlet  145  being controlled by a solenoid valve assembly  146 . A tank  148  containing a supply of high pressure gas, for example air, is removably mounted near the rear of the second section  140 . The tank  148  is normally sealed prior to installation to prevent escape of the high pressure gas. A puncher device  150  is provided to break the seal on the tank  148  upon installation of the tank  148 . Instead of a seal and a puncher device, a mechanical valve assembly can be provided to release the high pressure gas from the tank  148 . Various fluid lines  152  are provided between the tank  148  and a high pressure gas outlet  153  that discharges into the section  140 . Flow of the high pressure gas through the outlet  153  is controlled by a solenoid valve assembly  154 . 
         [0054]    Referring to  FIGS. 5 and 6 , operation of the ballast tank  102  will now be described. The pressure transducer  136  determines the depth of the ballast tank  102 , and thus the depth of the AUV  100 . The control electronics  134  control the solenoid valve assemblies  146 ,  154  to control the buoyancy characteristics of the ballast tank  102 , thereby controlling the depth of the AUV  100 . In particular,  FIG. 6  shows a representative boundary  160  between air  162  contained in the upper part of the interior of the second section  140  of the hull  122  and water  164  contained in the lower part of the interior of the second section  140  of the hull  122 . Opening the valve of the valve assembly  146  allows air  162  to vent from the hull  122  through the opening  144  and the outlet  145  as shown by the arrows in  FIG. 6 , which permits more water  164  to flood into the hull  122  through the openings  142  thereby reducing the buoyancy of the ballast tank  102  and causing the depth of the AUV  100  to increase. To increase buoyancy and decrease the depth of the AUV  100 , the valve of the valve assembly  146  is closed, and the valve of the valve assembly  154  is opened to introduce high pressure gas into the hull  122 . The high pressure gas forces water  164  out of the openings  142  in the hull  122  as shown by the arrows in  FIG. 6 , which increases the amount of air  162  in the hull  122  and increases the buoyancy of the ballast tank  102 . 
         [0055]    The ballast tank  102  is a structure that is separate from the AUV  100 , and is not a part or sub-part of the AUV  100 . As a result, the displaced volume of the AUV  100  remains the same before and after release of the ballast tank  102  from the AUV  100 . 
         [0056]    The AUV  100  and the ballast tank  102  are releasably attached in any suitable manner. For example, the AUV  100  and the ballast tank  102  can be releasably attached in a manner similar to the attachment described above for the AUV  10  and the payload  12  shown in  FIGS. 1-3 . 
         [0057]    In particular, referring to  FIG. 4 , one or more payload supports  170  are fastened to the AUV  100 , for example on the exterior surface of the hull  104 . In the illustrated example, there are two payload supports  170 , one of the supports  170  supporting a forward end of the ballast tank  102 , and one of the supports  170  supporting a rear end of the ballast tank  102 . The payload supports  170  passively support the ballast tank  102  on the AUV  100  without fastening the ballast tank  102  to the AUV  100  so that, absent other means for retaining the ballast tank  102  to the AUV  100 , the ballast tank  102  can freely separate from the payload supports  170 . In the illustrated example, each payload support  170  comprises a curved support bracket that generally matches the curvature of the cylindrical hull  104  of the ballast tank  102  so that the ballast tank  102  rests on the curved brackets when the ballast tank  102  is attached to the AUV  100 . However, other support configurations can be used. 
         [0058]    Referring to  FIGS. 4 and 5 , a releasable mechanism  172  releasably fastens the ballast tank  102  on the AUV  100 . Any releasable mechanism  172  that can retain the ballast tank  102  on the AUV  100 , and that can be actuated to release the ballast tank  102  from the AUV  100 , can be used. 
         [0059]    In the illustrated embodiment, the releasable mechanism  172  comprises a one-piece wire  174 , similar to the one-piece wire  46 , that crosses over and around the AUV  100  and the ballast tank  102 , and attaches at its free ends (not shown), similar to the free ends  48   a,    48   b,  to a burn wire  176  that is similar to the burn wire  50  seen in  FIG. 2 . In this example, the burn wire  176  (see  FIG. 5 ) is located in or on the ballast tank  102  instead of in or on the AUV  100  like in the embodiment in  FIGS. 1-3 . 
         [0060]    The one-piece wire  174  is sufficient to retain the ballast tank  102  on the AUV  100  during typical anticipated use. To release the ballast tank  102 , electricity is sent through the burn wire  176  which causes the burn wire  176  to heat up and break. When the burn wire  176  breaks, the ends of the wire  174  are released thereby releasing the ballast tank  102  from the AUV  100 . 
         [0061]      FIG. 4  shows another variation of securing the ballast tank  102  to the AUV  100  where a pair of forward and rear wires  180   a,    180   b  that are secured by burn wires (not shown) attach the ballast tank  102  from the AUV  100 . In this embodiment, one of the wires  180   a,    180   b,  such as the rear wire  180   b,  can hold a removable seal  182  in place that covers a pressure switch on the AUV  100  that controls activation of the AUV  100 . The seal  182  is removed when the wire  180   b  is released upon destruction of the burn wire, thereby activating the AUV  100 . 
         [0062]    The construction of the ballast tank  102  permits a number of possible mission scenarios to be implemented. For example, one example mission scenario is illustrated in  FIGS. 7A-D .  FIG. 7A  shows the AUV  100  and the ballast tank  102  deployed in the water. During this time, the AUV pressure switch is covered by the removable seal  182  that is held in place by the wire  180   b.  Therefore, the AUV  100  is dormant, with the expendable ballast tank  102  controlling and maintaining a predetermined depth of the AUV  100 . The AUV  100  and ballast tank  102  loiter and drift for a predetermined period time, such as hours, days, weeks, etc. 
         [0063]    With reference to  FIG. 7B , once the predetermined time period is reached, the ballast tank  102  control, which is part of the control electronics  134 , causes electrical energy to be directed through the burn wires connected to the wire  180   a,    180   b,  causing the burn wires to heat up and break, thereby releasing the wires  180   a,    180   b  and allowing the ballast tank  102  to release from the AUV  100 . The detached ballast tank  102  is initially positively buoyant and begins to rise as shown by the arrows in  FIG. 7B . In addition, the AUV  100  is initially negatively buoyant and begins to sink as shown by the arrows in  FIG. 7B . When the wires  180   a,    180   b  are released, the seal  182  over the pressure switch of the AUV is removed so that the AUV  100  becomes active. 
         [0064]    Referring to  FIG. 7C , in one embodiment, the ballast tank  102  can be immediately scuttled so that it sinks to the bottom by opening the valve of the valve assembly  146  so that the ballast tank  102  becomes negatively buoyant. In an alternative embodiment, the ballast tank  102  can be initially sent to or near the surface of the water so that a mission specific package  184  (seen in  FIG. 4 ) of the ballast tank  102  can perform a mission. For example, the package  184  can be a communications package allowing the ballast tank  102  to transmit and/or receive communications including, but not limited to, transmit a signal indicating the current global position of the ballast tank  102 , or send out jamming signals to jam communications in the area. After the mission of the package  184  is completed, the ballast tank  102  can then be scuttled as discussed above so that it sinks to the bottom. 
         [0065]    Referring to  FIG. 7D , after separation of the ballast tank  102 , the AUV  100  becomes active and can begin its mission. The mission can include, but is not limited to, traveling to a new location to create a stand-off distance between the AUV  100  and the ballast tank  102 . 
         [0066]    The AUV  10  and the payload  12 , and the AUV  100  and ballast tank  102 , can be launched from any suitable launch platform including, but not limited to, a surface or submerged vessel, air dropped into the water from an airborne vehicle, launched from shore, or launched from any other platform. 
         [0067]      FIGS. 8A-C  illustrate a launch kit  200  that can be used to launch the AUV  10  and the payload  12 , or the AUV  100  and ballast tank  102 , from a launch platform such as a submarine. The launch kit  200  includes a pair of shells  202   a,    202   b  and an end cap  204 . The shells  202   a,    202   b  are releasably connected to one another and generally surround the AUV  10 /payload  12  or the AUV  100 /ballast tank  102  combination. The end cap  204  closes the front end of the shells  202   a,    202   b.  After being launched from the launch platform, the shells  202   a,    202   b  separate and fall away along with the end cap  204 , freeing the AUV  10 /payload  12  combination or the AUV  100 /ballast tank  102  combination for their mission. 
         [0068]    The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.