Hybrid buoyancy control for submersible vessels

Abstract

A submersible vessel is described, having a hybrid buoyancy system composed of a ballast tank and a buoyancy engine. The ballast tank provides for large changes in buoyancy of the vessel, while the buoyancy engine provides small changes. Use of the ballast tank in the buoyancy engine in combination achieves buoyancy control that cannot be achieved by using a ballast tank or a buoyancy engine alone. The combined use of a ballast tank and buoyancy engine allows a submersible vessel to fully float on a water surface, maintain a swamped state just beneath the water surface and additionally dive beneath the water surface and maintain a desired depth.

Description

II. Cross Reference to Related Application

[0001] The present application claims the benefit of provisional application No. 63 / 729,847 filed on Dec. 9, 2024.BACKGROUNDI. Government Interest

[0002] This invention was made with government support under grant no. DE-SC0021905 awarded by the Department of Energy. The government has certain rights in the invention.III. Field of Use

[0003] The present application relates to the maritime industry. More specifically, the present application relates to submersible vessels.IV. Description of the Related Art

[0004] Autonomous marine vessels are becoming more ubiquitous, as they offer capabilities unmatched by manned vessels, such as the ability to undertake long voyages without the need for onboard personnel, food or water. In some cases, even fuel is not required, in the case of unmanned sailing vessels, such as mono hull sailboats and multi-hull vessels, such a catamarans and trimarans. Autonomous sailing vessels may be particularly useful in commercial or military applications, as they are quiet and can operate for long time periods without human intervention.

[0005] Recently, autonomous sailing vessels have been developed that are capable of sailing on the surface of water, sailing in a partially-submerged, or “swamped” state, where a hull is submerged with its sail extending from the water surface and a fully-submerged state, diving to depths to avoid dangers such as approaching ships or storms. One such example of such a submersible sailing vessel is described in U.S. Pat. No. 10,029,773 assigned to the assignee of the current invention.

[0006] One problem for such submersible vessels is that they require different amounts of buoyancy for different operating states (i.e., fully surfaced, swamped and fully submerged). Traditional methods of buoyancy control utilize one or more ballast tanks, typically used on submarines. When diving, the ballast tanks are flooded with surrounding seawater, causing buoyancy to sharply decrease. When surfacing, high-pressure compressed air is forced into the ballast tanks, causing the seawater therein to be expelled.

[0007] Another well-known way to control buoyancy of a submersible vessel is with the use of buoyancy engines. Buoyancy engines alter the buoyancy of a vessel using a pressure-resistant chamber that contains a gas and an incompressible fluid. The liquid may be pumped into and out of the chamber, thus altering the volume of gas in the chamber which, in turn, alters the buoyancy of the vessel.

[0008] Both of the aforementioned buoyancy control techniques suffer drawbacks and may not be suitable for a small, lightweight, power-constrained submersible vessel. For example, the use of ballast tanks requires that the tanks be cycled from nearly empty to nearly full of water, each cycle requiring large amounts of energy, especially at depth. Additionally, maintaining a precise depth is difficult and energy-intensive, especially in applications where a vessel's buoyancy may change based on its depth, i.e., if a vessel contains components that “crush” under the pressure of the water. Regarding buoyancy engines, they generally do not provide enough buoyancy to float a vessel fully on the water surface. Further, buoyancy engines are typically bulky and heavy, which makes them less than ideal for applications on smaller vessels where size and weight are important design considerations.SUMMARY

[0009] The embodiments described herein relate to embodiments of a system and method controlling buoyancy of a submersible vessel. In one embodiment, a submersible vessel is described, comprising a ballast tank for causing large changes in a buoyancy of the submersible vessel, a buoyancy engine for causing smaller changes in buoyancy of the submersible vessel less than the large changes, and a buoyancy controller for altering the buoyancy of the submersible vessel using both the ballast tank and the buoyancy engine to achieve and maintain different depths by the submersible vessel.

[0010] In another embodiment, a method for controlling buoyancy of a submersible vessel is described, comprising: adjusting a first buoyancy produced by a ballast tank of the submersible vessel that causes large changes in buoyancy of the submersible vessel, adjusting a second buoyancy produced by a buoyancy engine of the submersible vessel for causing smaller changes in buoyancy of the submersible vessel less than the large changes and adjusting the buoyancy of the submersible vessel by adjusting both the first and second buoyancies due to the ballast tank and the buoyancy engine, respectively.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features, advantages, and objects of the embodiments of the present invention will become more apparent from the detailed description as set forth below, when taken in conjunction with the drawings in which like referenced characters identify correspondingly throughout, and wherein:

[0012] FIG. 1 is a side view of one embodiment of a submersible vessel, in this embodiment, a semi-autonomous, submersible sailing vessel;

[0013] FIG. 2 is a functional block diagram of one embodiment of a hybrid buoyancy system of the submersible vessel as shown in FIG. 1, comprising ballast tank, a buoyancy engine and a buoyancy controller;

[0014] FIG. 3 is a side view of another embodiment of a submersible vessel, in this embodiment, a hull and a floatation element combined into a single element;

[0015] FIG. 4 is a functional block diagram of one embodiment of the buoyancy controller as shown in FIG. 2;

[0016] FIG. 5 is a state diagram of a variety of operating states that the submersible vessel as shown in FIG. 1 may achieve using the hybrid buoyancy system as shown in FIG. 2;

[0017] FIGS. 6A-6C represent a flow diagram illustrating one embodiment of a method, performed by the buoyancy controller as shown in FIG. 2, for controlling buoyancy of the submersible vessel as shown in FIG. 1 in order to achieve the states as shown in FIG. 5;

[0018] FIG. 7 is a graphical representation showing the state of the ballast tank, a collector and reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a fully-surfaced state;

[0019] FIG. 8 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a prepare to swamp state;

[0020] FIG. 9 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a prepare to dive state;

[0021] FIG. 10 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a swamped state;

[0022] FIG. 11 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a dive state;

[0023] FIG. 12 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in a fully-submerged state;

[0024] FIG. 13 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in an ascent state; and

[0025] FIG. 14 is a graphical representation showing the state of the ballast tank, the collector and the reservoirs of the buoyancy engine as shown in FIG. 2 when the submersible vessel is in an emergency surface state.DETAILED DESCRIPTION

[0026] The present application describes various embodiments of a submersible vessel utilizing “hybrid” buoyancy control techniques. Specifically, a submersible vessel comprises a ballast tank and a buoyancy engine. The ballast tank provides “course” buoyancy adjustments to a vessel while the buoyancy engine provides “fine” buoyancy adjustments. The ballast tank and the buoyancy engine may be used in concert with each other to achieve both static and dynamic operating states. The novel use of a ballast tank in combination with a buoyancy engine allows a submersible vessel to fully float on the surface of water while also allowing the vessel to dive to and maintain considerable depths, all while maintaining a compact and light design. Additionally, very little energy is needed to maintain a maximum depth, as the buoyancy engine is a semi-stable system where small deviations from neutral buoyancy do not result in acute changes in the rate of ascension or descension.

[0027] The advantages of a hybrid buoyancy system as described herein is an ability for a submersible vessel to achieve very high buoyancy for floating on the water surface while also minimizing power to maintain depth when submerged. In contrast, using a gas-based ballast tank alone achieves high buoyancy while surfaced, but maintaining depth demands regular energy use due to the need to constantly correct buoyancy (as a gas-based buoyancy tank is, by nature, unstable at neutral buoyancy). Using a gas-based ballast tank alone requires depletion of a large tank of compressed gas at potentially very high pressure, or frequent use of a high-pressure air pump, which draws considerable power. Using a gas-fluid buoyancy engine alone does not typically produce the high buoyancy required to float a vessel on the water surface, for example, while sailing or motoring, and to do so would require a prohibitively heavy and large system.

[0028] FIG. 1 is a side view of one embodiment of a submersible vessel 100, in this embodiment, a semi-autonomous, submersible sailing vessel. In other embodiments, vessel 100 could comprise a submarine, an autonomous or semi-autonomous surface and subsurface vessel lacking a sail or wing, or virtually any kind of vessel capable of surface and sub-surface operation, regardless of propulsion type. The term “semi-autonomous” means a vessel capable of performing operations independently of any human while occasionally receiving instructions on how to carry out operations via a communication link, such as a satellite link.

[0029] In the embodiment shown in FIG. 1, vessel 100 comprises a hull 102, a floatation element 104, a mast 106, a wing 108, a keel 110, a rudder 112, masthead electronics 124 and a thruster 114 comprising a propeller 116. In some respects, this design is similar to a submerged sailing vessel as described in U.S. Pat. No. 10,029,773, assigned to the assignee of the present application and incorporated by reference herein. Of course, in other embodiments, vessel 100 may lack some of these features or comprise additional ones. For example, in one embodiment, vessel 100 may comprise a submersible, autonomous motorized boat lacking mast 106 and wing 108 well additionally comprising a gasoline engine to power the boat.

[0030] In FIG. 1, vessel 100 is shown operating in a “swamped” state, i.e., with hull 102 fully submerged in water 120 near water surface 118 with most or all of mast 106 and wing 108 protruding from water 120 and extending into air 122. In the swamped state, hull 102 is generally approximately between zero and ten feet within water surface 118, depending in part on the length of mast 106. The swamped state may be desirable in situations where stealth is important while sailing / moving, while communicating via masthead electronics 124, while determining wind speed and direction, while determining ambient air temperature, while drawing air into a ballast tank, etc.

[0031] Wing 108 is coupled to mast 106, which in turn is coupled to flotation element 104. Wing 108 may comprise a number of parallel, spaced apart “ribs” that support a sail or a rigid material or semi-rigid membrane, designed to propel vessel 100 during the swamped state or in a fully-surfaced state (i.e., hull 102 protrudes at least partially from water surface 118 and, typically, a maximum buoyancy is achieved by vessel 100). Wing 108 may be rotatably coupled to mast 106, where mast 106 is fixedly coupled to flotation element 104, or wing 108 may be fixedly coupled to mast 106 and mast 106 is rotatably coupled to flotation element 104. As vessel 100 is propelled by wind acting on wing 108, wing 108 is generally free to rotate around a longitudinal axis formed by mast 106 and may be controlled by an automatic wing-control mechanism, as described by U.S. Pat. No. 10,625,841, assigned to the assignee of the present application and incorporated by reference herein.

[0032] Sailing vessel 100, in one embodiment, is 5 feet long, 1 foot wide and 8 feet tall, comprising a displacement of approximately 270 pounds. However, the inventive concepts described herein could be applied to other vessels that are much smaller, or much larger, than these dimensions.

[0033] Wing 108 comprises one or more traditional soft sails, rigid wings, semi-rigid wings, inflatable wings, etc. In some embodiments, wing 108 is constructed from a lightweight, substantially rigid material such as molded fiber composite material or aluminum alloy. In cross-section, wing 108 is preferably configured as an airfoil that generates propulsive force (analogous to upward “lift” of an aircraft wing, but in a generally horizontal direction) regardless of whether an angle of attack is to the right or left of the wind, suitable foil configurations being known to those skilled in the relevant art. In another embodiment, the sail is constructed from a lightweight, flexible material such as cloth, nylon, Dacron®, Spectra®, Dyneema®, mylar, carbon fiber, etc. In these embodiments, wing 108 may be partially or fully inflated by the flow and pressure of incident wind, i.e., when wing 108 is formed similar to a ram air hang glider or kite wing.

[0034] Mast 106 extends generally perpendicularly from floatation element 104, providing a structure to support wing 108. In one embodiment, a longitudinal channel 126 may be formed longitudinally inside mast 106, with one end exposed to air 122 and the other end of channel 126 coupled to a ballast tank within floatation element 104 and / or hull 102 via a pump and appropriate tubing or the like (not shown). When vessel 100 is in the swamped or fully-surfaced state, the pump may draw air 122 through channel 24 and into a ballast tank to expel water in the ballast tank and / or to charge a tank with compressed air.

[0035] In addition to the swamped state and the fully-surfaced state, vessel 100 may be operated in a fully-submerged state, where the entire vessel 100 is submerged beneath water surface 118. This may be desired when adverse surface conditions exist, such as the presence of a storm or enemy vessel, to drift with an underwater current towards an intended destination, for exploration purposes, for scientific measurement purposes, etc. Vessel 100 is capable of achieving and maintaining depths ranging from 0 to 100 meters or more, depending on the design of vessel 100. Generally, larger and heavier vessels can achieve greater depth.

[0036] Thruster 114 is used to help propel vessel 100 in any of the three aforementioned operating states of vessel 100 by activating propeller 100 or some other propulsion device. In the present embodiment, thruster 114 is coupled to hull 102 via keel 110 and rudder 112.

[0037] Hull 102 is coupled to thruster 114 via keel 110 and rudder 112. Keel 110 is attached to a fore portion of hull 102 at one end, and to thruster 114 at the other end. Rudder 112 is rotatably coupled to an aft portion of hull 102 at one end and rotatably coupled to thruster 114 at the other end. Rudder 112 is coupled to hull 102 and thruster 114 such that it may be rotated about an axis formed longitudinally along the length of rudder 112, near a fore edge, as shown. In other embodiments, keel 110 and rudder 112 may connect at a same point on hull 102 or may be spaced apart from each differently than what is shown in FIG. 1.

[0038] Keel 110 may comprise a cross-section in the shape of a wing, teardrop, or other shape, to combat a side force generated by the wing 108 during sailing. In one embodiment, keel 110 comprises a solid structural element comprising a core material and a composite skin. In another embodiment, keel 110 may comprise one or more hollow compartments, to aid in buoyancy and / or to store materials and / or people. The size and shape of keel 110 is dependent on various factors, such as the overall size and weight of the vessel, especially wing 108.

[0039] Rudder 112 may also comprise a cross-section that is similar to the cross-section of keel 110, i.e., in the shape of a wing, teardrop, or other shape. In this embodiment, rudder 112 may also contribute to counter-acting the side force produced by wing 108 during sailing. In other embodiments, rudder 112's size and shape are designed to primarily apply a particular turning force to vessel 100, for purposes of steering, in accordance with design criteria to achieve certain performance goals. In any case, rudder 112 may be rotatably coupled using independent coupling mechanisms at each end or, in other embodiments, an internal rod or tube forming a structural element, and an airfoil-shaped exterior pivotally coupled to the rod or tube such that the airfoil shaped skin can rotate about the structural rod or tube in order to steer vessel 100. In some embodiments, such a rod or tube is located along a longitudinal fore edge of rudder 112. In other embodiments, the rod or longitudinal tube may be formed longitudinally through a middle, or even an aft, section of rudder 112. Rudder 112 may be controlled by a control system located within hull 102 or inside floatation element 104, comprising generally of a torque-producing mechanism, such as an electric motor, gears, pulleys, and / or other known mechanical devices.

[0040] Hull 102 may comprise one or more compartments, used to transport materials and / or, in some embodiments, one or more persons. Hull 102 may additionally house a ballast tank, a buoyancy engine, a battery and electronics used to operate vessel 100. Hull 102 may be constructed of a dense material, such as steel or lead, in order to provide inherent ballast. In other embodiments, hull 102 may comprise an external ballast affixed to an exterior portion of hull 102.

[0041] Floatation element 104 is coupled to hull 102, used in some embodiments to provide additional buoyancy to vessel 100. In some embodiments, floatation element 104 comprises a ballast tank and a compressed air system that causes surrounding water, or compressed air, to fill the ballast tank in order to achieve a desired buoyancy. In other embodiments, in addition to or excluding a ballast tank, floatation element 104 is constructed of buoyant material, such as closed-cell foam or some other material that is lightweight, strong and waterproof. Whatever material is chosen, it will typically be crushed somewhat by water pressure acting on the material as vessel 100 descends to various depths. When the material is crushed, the volume of floatation element 104 is reduced somewhat, and the displacement of vessel 100 decreases, causing a corresponding decrease in buoyancy.

[0042] The size, i.e., volume, shape and weight, of floatation element 104 is dependent on an amount of buoyancy needed to achieve neutral buoyancy of vessel 100 at or near water surface 118 and the type of buoyant material used. In general, floatation element 104 (as well as any net buoyancy provided by thruster 114, hull 102, rudder 112 and keel 100) must provide enough buoyancy to place vessel 100 into a fully-surfaced state, i.e. be greater or equal than the displacement of mast 106, wing sail 108 and any portion of floatation element 104 above the water surface while in the fully-surfaced state.

[0043] In a design variation of vessel 100, floatation element 104 is not used, and buoyancy of vessel 100 is controlled by utilizing a ballast tank and a buoyancy engine housed within hull 102. In a related embodiment, hull 102 and floatation element 104 are merged into a single structure, typically constructed from the same buoyant and waterproof material as floatation element 104. In this embodiment, most of the electrical components of vessel 100 may reside inside this combined structure.

[0044] A buoyancy of vessel 100 is an important design consideration which depends, in part, on the size and weight of vessel 100. When designing vessel 100 to be relatively small, such as less than 5 feet in length and less than 150 pounds, the materials chosen for mast 106, hull 102, wing 108 and floatation element 104 will affect the overall buoyancy of vessel 100. Thus, it may be desirable to choose materials for each portion of vessel 100 with lightweight materials. For example, the buoyancy of mast 106 may be increased over prior art designs by using a lightweight, strong polymer, such as ultra-high molecular weight polyethylene fibers (UHMWPE), any polyacrylonitrile-based material, or any other strong, lightweight material. Mast 106 may, additionally, be formed with an increased diameter versus prior art masts for similarly-sized vessels, which adds volume to mast 106.

[0045] Buoyancy of vessel 100 is controlled by a computerized buoyancy controller (not shown) typically located in either hull 102 or floatation element 104. Additional description of such a buoyancy controller is provided later herein.

[0046] FIG. 2 is a functional block diagram of one embodiment of a hybrid buoyancy system 201, comprising ballast tank 200, a buoyancy engine 230 (comprising collector 216, reservoirs 218A and 218B, pump 222, fluid pipe 224, fluid pipe 226, valve 220), a computerized buoyancy controller 232, a depth sensor 234, a pressure sensor 236 and a level sensor 238. Buoyancy controller 232 is a central processing computer used primarily to control the buoyancy of vessel 100 by way of altering the buoyancy provided by ballast tank 200 and the buoyancy provided by buoyancy engine 230. In some embodiments, the functionality of buoyancy controller 232 may be incorporated into another central computer onboard vessel 100, such as a “master” control unit used to control the buoyancy of vessel 100 as well as to perform other functions, such as navigation, communications, energy management, etc.

[0047] Buoyancy controller 232 uses both ballast tank 200 and buoyancy engine 230 in combination to achieve and maintain the aforementioned operating states of vessel 100.

[0048] Ballast tank 200 typically comprises a large, rigid tank used to provide large modifications of vessel displacement (i.e., buoyancy) by either flooding ballast tank 200 with surrounding water 120 to decrease buoyancy or to fill ballast tank 200 with air (either compressed or ambient air 120 when vessel 100 is in the swamped state or fully-surfaced state). The term “large” when used to describe buoyancy means an amount of buoyancy required to float vessel 100 fully on top of water surface 118, i.e., with at least a portion of hull 102 protruding from water surface when 118. As used herein, the terms “flood”, “flooding”, “fill”, “filling” or the like does not necessarily mean to “completely” flood or fill ballast tank 200 unless the term “completely” is used in connection therewith. When filled with air, ballast tank 200 displaces water to provide the buoyancy needed to lift mast 106 and wing 108 above water surface 118 and, typically, at least a portion of floatation element 104 and, in some cases, at least a portion of hull 102. The volume of ballast tank 200 is typically chosen such that it displaces water equal to the weight of vessel components lifted above the water surface 118 while in a fully-surfaced state, (such as mast 106 and wing 108). In some embodiments, ballast tank 200 comprises a port 202 to surrounding water 120, typically located on a lower portion of ballast tank 200, for filling and discharging water into and out of ballast tank 200. In some embodiments, ballast tank 200 comprises a valve 204 which provides an opening to ambient air 122 when vessel 100 is in the swamped or fully-surfaced state.

[0049] In the embodiment shown in FIG. 2, ballast tank 200 is the same as hull 102. In other embodiments, hull 102 comprises a separate ballast tank 200 as well as one or more water-tight compartments for housing various electronics, such as master control unit (not shown), buoyancy controller 232 and a battery (not shown) used to power vessel 100, for storing goods (such as food medicine, fuel, etc.), for providing living quarters for a crew, etc.

[0050] Buoyancy engine 230 comprises collector 216 which provides an independent source of buoyancy then the buoyancy produced by ballast tank 200. Collector 216 typically comprises one or more high-pressure, rigid tanks within ballast tank 200 that allows for variable displacement compensation using a combination of an incompressible fluid and a compressible gas. The gas and fluid may be allowed to contact each other inside collector 216 or separated by a slidable barrier inside collector 216 which does not allow mixing, such as a flexible membrane or a rigid wall. In another embodiment, a linear actuator is used to drive a piston back and forth inside collector 216, akin to a syringe. With the piston positioned approximately mid-way through the length of collector 216, gas may be introduced into a lower portion of collector 216 (i.e., the volume defined by the space inside collector 216 between an end-cap of collector 216 and a gasket defining one end of the piston). The other end of collector 216 may be open to water inside ballast tank 200. To ascend, the piston is driven towards the water side, thereby causing an expansion of the volume of gas trapped within the lower portion of collector 216. Water may be ejected from the other end of collector 216, and the displacement of vessel 100 caused by collector 216 and, thus, buoyancy increases. To descend, the piston is driven towards the gas side, compressing the gas inside the lower portion of collector 216, and drawing in water from the other end, decreasing displacement and thus buoyancy.

[0051] In another embodiment, collector 216 comprises a hollow cylinder, a piston and a water pump for forcing the water inside ballast tank 200 into the hollow cylinder, driving the piston inside the hollow cylinder. In another embodiment, a flexible membrane (latex, etc.) inside the collector tank maintains separation between the water and gas, guaranteeing that only water can exit the water side. The air side is pre-pressurized, so using a pump to force surrounding water into the water side compresses the air as the membrane keeps the two separate, decreasing the displacement of vessel 100. Disabling the water pump and opening a valve 220 may completely evacuate the fluid side without any pumping power needed due to the pressure in the air side.

[0052] Buoyancy engine 230 is used to provide smaller adjustments to vessel buoyancy than ballast tank 200. These adjustments allow for achieving and maintaining the swamped state, to aid in descent and ascent, and to maintain depth efficiently. The overall buoyancy of vessel 100 is decreased by buoyancy engine 230 as incompressible fluid from the reservoirs 218A and B is forced into collector 216 via fluid pump 222, thereby deflating the reservoirs and compressing a gas (typically air) inside of collector 216 such that the volume 228 of the gas inside collector 216 is reduced. The term “incompressible” means an ability to resist compression, so that volume and density of the fluid remain nearly constant even under pressure. Reducing the volume 228 of air inside collector 216 causes a reduction in displacement of vessel 100 and, accordingly, the buoyancy of vessel 100. Conversely, buoyancy of vessel 100 is increased by opening valve 220 and activating pump 222 to pump the fluid out of collector 216 and into the reservoirs 218A and B, thereby inflating the bladders with the in all compressible fluid and increasing the volume 228 of the gas inside collector 216. While only a single collector 216 and two reservoirs 218A and B are shown in FIG. 2, in other embodiments, vessel 100 may comprise two or more collectors, and a greater, or fewer, number of reservoirs.

[0053] Reservoirs 218A and B are located within ballast tank 200 such that they are exposed to water inside ballast tank 200 when ballast tank 200 is at least partially filled with water and, therefore, experience the same pressure as the surrounding water pressure (as water is allowed to enter the ballast tank via port 202). Each bladder is typically pliable and inflatable, allowing each bladder to expand as incompressible fluid is forced into them by pump 222 when increasing the buoyancy of vessel 100 or to deflate as the incompressible fluid is pumped from the bladders into collector 216 when reducing buoyancy.

[0054] During the manufacturing process, or prior to deployment, buoyancy engine 230 is initialized with an amount of incompressible fluid, such as oil, into reservoirs 218A and B, typically filling them substantially, and a gas, such as air, nitrogen, or some other gas, fills collector 216 at a particular pressure, such as 1 Atmosphere. The volume of oil in the bladders is at least enough to substantially fill the entire volume of collector 216 when the bladders are deflated.

[0055] In one embodiment, collector 216 is designed such that vessel 100 achieves neutral buoyancy at or near water surface 118 when ballast tank 200 is filled with water and collector 216 is approximately two-thirds filled with the incompressible fluid. At a maximum-allowable depth, the displacement of fluid within collector 216 may be increased in order to account for a certain loss of buoyancy caused by crush of certain elements of vessel 100, such as floatation element 104. Thus, it is often desirable to have collector 216 more than halfway filled with the incompressible fluid while vessel 100 is in a neutrally buoyant state near water surface 118, as by doing so, extra buoyancy and be generated by collector 216 when vessel 100 is at a maximum depth.

[0056] The overall buoyancy of vessel 100 is controlled using both ballast tank 200 and buoyancy engine 230. When submerging, most or all of the air inside ballast tank 200 is expelled from ballast tank 200 by opening the air valve 204, thus allowing water to flood ballast tank 200 via port 202 and surround reservoirs 218A and B. Then, small adjustments to the buoyancy of vessel 100 may be made using only buoyancy engine 230 in order to descend at a particular rate, to maintain depth in a fully-submerged state, to ascend at a particular rate, to achieve a swamped state and to achieve a fully-surfaced state. To increase a descent rate of vessel 100, valve 220 may be opened and additional incompressible fluid pumped from reservoirs 218A and B into collector 216 via pump 222, thus reducing the displacement of fluid inside collector 216 and reducing the buoyancy of vessel 100. Conversely, to increase buoyancy and therefore decrease the descent rate of vessel 100, valve 220 is opened and pump 222 is activated to pump some of the incompressible fluid out of collector 216 and back into reservoirs 218A and B, thus increasing the displacement of fluid inside collector 216 and increasing the buoyancy of vessel 100.

[0057] To maintain depth, the overall displacement / buoyancy of vessel 100 may need small adjustments from time to time. This may be achieved by using buoyancy engine 230 alone to pump small amounts of incompressible fluid into, or out of, collector 216, to decrease or increase the buoyancy of the vessel, respectively. This takes very little energy at depth, since the pressure difference between the compressible gas acting on the incompressible fluid in collector 216 and the water pressure acting on reservoirs 218A and B is significantly small. For example, in one embodiment, at a maximum-design depth of 100 meters, the water pressure acting on reservoirs 218A and B is approximately 11 Atmospheres, collector 216 is approximately one-half to one third full of incompressible fluid (due to the decreased buoyancy of vessel 100 due to “crush”) and the gas inside collector 216 is also approximately 11 Atmospheres. Because the pressures are approximately equal, it takes very little energy to pump small amounts of fluid into or out of collector 216.

[0058] When it is desired to surface, buoyancy engine 230 is used to increase the displacement / buoyancy of the vessel by opening valve 220 and pumping some amount of incompressible fluid from collector 216 into reservoirs 218A and B. As the depth of vessel 100 is reduced during ascent (and, therefore, the water pressure on reservoirs 218A and B), the pressure inside collector 216 becomes significantly higher than the water pressure acting on reservoirs 218A and B. Thus, the incompressible fluid may be continuously transferred to reservoirs 218A and B during ascent with minimal or no energy expense simply by opening valve 220 due to the favorable trend in the pressure differential between the compressible air inside collector 216 and the water pressure acting on reservoirs 218A and B.

[0059] FIG. 3 is a side view of another embodiment of vessel 100, where floatation element 104 and hull 102 have been merged to form a single entity, referred to as hull 102. It should be understood that the placement of each component may reside in different areas within vessel 100, that the relative size of each component may not be to scale, and some components have been omitted, such as wing 108. In this embodiment, ballast tank 200 is a separate element housed within hull 102 and buoyancy engine 230 resides outside of ballast tank 200 but inside hull 102. In this embodiment, a number of components may reside inside hull 102 in one or more water-proof compartments 300, such as a battery 302, air system 212, master control unit 406 and buoyancy controller 232.

[0060] Ballast tank 200 is located within hull 102, comprising valve 204 and, in some embodiments, valve 302. In other embodiments, valve 302 may not be needed. Valve 204 and valve 302 are each operated electronically via buoyancy engine 230 in order to achieve various states of ballast tank 200, i.e. full or nearly fall, empty or nearly empty, or something in between. As described in FIG. 2, air system 212 may force air into or out of ballast tank 200 when mast 106 is exposed to the air via longitudinal channel 126 formed through mast 106.

[0061] Buoyancy engine 230, in this embodiment, is located outside ballast tank 200 but within whole 102 in a second compartment 304 that is exposed to water surrounding vessel 100 via port 202 in whole 102 as shown. Operation of hybrid buoyancy system 201 operates almost identically as the embodiment shown in FIG. 2.

[0062] FIG. 4 is a functional block diagram of one embodiment of computerized buoyancy controller 232, comprising processor 400, memory 402, and communication interface 404, as well as several external components, in this example, master control unit 406, depth sensor 234, pressure sensor 236 and level sensor 238. Buoyancy controller 232 controls buoyancy of vessel 100 by controlling ballast tank 200 and buoyancy engine 230. It should be understood that the functional blocks shown in FIG. 3 could be arranged in different manners in other embodiments, and that some basic functional blocks have been omitted, such as a power supply, for clarity.

[0063] Processor 400 is configured to provide general operation of buoyancy controller 232 by executing processor-executable instructions stored in memory 402, for example, executable computer code. Processor 400 comprises one or more general or special-purpose microprocessors, microcontrollers, discreet components and / or ASICs, chosen based on factors such as power consumption, processing speed, size and cost.

[0064] Memory 402 comprises one or more non-transitory information storage devices, such as RAM, ROM, EEPROM, flash memory, or virtually any other type of electronic, mechanical, or optical storage device. Memory 402 is used to store the processor-executable instructions for operation of buoyancy controller 232 as well as any information used by processor 400 to perform such operations, such as threshold information, a maximum depth level, desired ascent and descent rates, one or more dive profiles (i.e., a schedule of desired depth levels as a function of time), etc. In some embodiments, at least a portion of memory 402 is incorporated into processor 400, such as the case in embodiments where processor 400 comprises a microcontroller, custom ASIC or some other processing device having an on-board memory.

[0065] Communication interface 404 is coupled to processor 400, comprising circuitry necessary for processor400 to electronically communicate with various onboard sensors, control devices (such as valve 204, valve 222, pump 222, and valve 208), masthead electronics 124, solar control circuitry, etc. Communication interface 404 may comprise two or more different types of communication circuitry needed to communicate in different ways with the various devices. Examples of such different types of communication circuitry include Wi-Fi circuitry, Ethernet circuitry, USB circuitry, data bus I / O, etc. Such circuitry as well-known in the art.

[0066] Depth sensor 234 provides depth information associated with vessel 100 while diving. It typically comprises a water pressure sensor. Depth sensor 234 is typically coupled to buoyancy controller 230 via communication interface 404, although in other embodiments, it could be coupled to master control unit 406 in addition or alternative to buoyancy controller 230. Depth information is used to control buoyancy of vessel 100 while diving, ascending and maintaining depth.

[0067] Pressure sensor 236 may comprise a gas-based sensor or a fluid-based sensor for monitoring the pressure inside collector 216. Pressure sensor 236 is selected to withstand high pressures that may be encountered inside collector 216 at maximum depth. Signals from pressure sensor 236 are provided to buoyancy controller 230 via communication interface 404 and / or to master control unit 406. Pressure readings may be used to determine an amount of buoyancy provided by collector 216.

[0068] Level sensor 238 is typically located on a wall of ballast tank 200 to indicate when a water level inside ballast tank 200 has reached level sensor 238 and, therefore, a desired level. In some embodiments, multiple level sensors 238 may be used, each one to indicate a particular level of water inside ballast tank 200. Level sensor 238 is coupled to buoyancy controller 230 and / or master control unit 406.

[0069] FIG. 5 is a state diagram of a variety of operating states that vessel 100 may achieve using hybrid buoyancy system 201. Initially, vessel 100 may be in a fully-surfaced state 500, either stationary or navigating on water surface 118, with mast 106, wing 108 and flotation element 104 fully exposed to air 122, and hull 102 partially exposed to air 122. In the fully-surface state, buoyancy of vessel 100 is it a maximum as contributed by buoyancy engine 230 and ballast tank 200. Specifically, ballast tank 200 is empty or nearly empty and full or nearly full of air and collector 216 is empty or nearly empty of the incompressible fluid, which is stored in reservoirs 218A and B. Below is a summary of the various operating states of vessel 100 and a typical, corresponding state of collector 216, reservoirs 218A and B and ballast tank 200:CollectorReservoirsBallast TankFully-SurfacedEmpty / Nearly EmptyFull / Nearly FullEmpty / Nearly EmptyReady to SwampMore than ½ FullLess than ½ FullEmpty / Nearly EmptyReady to DiveFull / Nearly FullEmpty / Nearly EmptyEmpty / Nearly EmptySwampedMore than ½ FullLess than ½ FullFull / Nearly FullDivingMore than ¾ FullLess than ¼ FullFull / Nearly FullFully-SubmergedHalf / Less than ½ FullHalf / more than ½ FullFull / Nearly Fullat DepthAscentLess than ½ FullMore than ½ FullFull / Nearly Full

[0070] From the fully-surfaced state 500, vessel 100 may transition into one of several other possible states, for example, a “prepare to dive” state 502, a “prepare to swamp” state 504, a swamped state 506, or a dive state 508. In “prepare to dive” state 502, ballast tank 200 is full or nearly full with air and collector 216 is full or nearly full with the incompressible fluid from reservoirs 218A and B. In the “prepare to swamp” state 504, ballast tank 200 is full or nearly full with air and collector 216 may be partially filled with the incompressible fluid from reservoirs 218A and B. In the swamped state 506, ballast tank 200 is filled or nearly filled with water and collector 216 is empty or nearly empty of the incompressible fluid from reservoirs 218A and B. In the dive state 508, ballast tank 200 is filled or nearly full of water while collector 216 is typically more than halfway filled with the incompressible fluid, ranging from half-way filled (resulting in a slightly negative buoyancy provided by buoyancy engine 230, causing a smallest rate of descent) to almost completely filled (resulting in a maximum negative buoyancy provided by buoyancy engine 230, causing a maximum rate of descent). The descent rate of vessel 100 during dissent may be changed by adjusting the volume of air / fluid inside collector 216 between these two points.

[0071] When vessel 100 is in “prepare to dive” state 502, vessel 100 may transition to dive state 508 or revert to fully-surfaced state 500. While in the “prepare to swamp” date 504, vessel 100 may transition to swamped state 506, dive state 508 or revert to fully-surfaced state 500. While in swamped state 506, vessel 100 may transition to dive state 508 or revert to fully-surfaced state 500.

[0072] While in dive state 508, vessel 100 may transition to a “fully-submerged” state 510 or revert back to “prepare to dive” state 502, “prepare to swamp” state 504 or swamped state 506. In the “fully submerged” state (sometimes referred to as a “maintain depth” state), ballast tank 200 is full or nearly full of water and buoyancy engine 230 is more than halfway full and in one embodiment approximately one third full with the incompressible fluid from reservoirs 218A and B. In this state, the overall buoyancy of vessel 100 is approximately neutral.

[0073] After maintaining depth at the “fully-submerged” state 510, vessel 100 may transition to an ascent state 512 to revert to any of the aforementioned states in a controlled manner by varying the amount of incompressible fluid inside collector 216. Typically, ballast tank 200 is not used to alter the buoyancy of vessel 100. In the ascent state 512, ballast tank 200 is typically full or nearly full of water and the incompressible fluid within collector 216 may vary from between the volume inside collector 216 when vessel 100 is neutrally buoyant at depth to being nearly or completely void in collector 216. In some embodiments, vessel 100 may enter an “emergency ascent” state 514 in situations where vessel 100 is unable to surface using buoyancy engine to 230. In this state, ballast tank 200 is filled with compressed gas from an air tank or gas cartridge of system 212 filled with a compressed gas, thereby greatly increasing buoyancy of vessel 100 and causing vessel 100 to surface.

[0074] FIGS. 6A-6C represent a flow diagram illustrating one embodiment of a method, performed by buoyancy controller 232, for controlling buoyancy of vessel 100 in order to achieve the states as shown in FIG. 5. It should be understood that in some embodiments, not all of the method steps shown in FIG. 6 are performed, and that the order in which the steps are performed may be different in other embodiments.

[0075] At step 600, buoyancy engine 230 is initially configured. Initial configuration comprises filling reservoirs 218A and B with an incompressible fluid, such as oil, and introducing a volume 228 of compressible gas into collector 216. The amount of incompressible fluid in the bladders is at least enough to substantially fill collector 216 when minimal buoyancy of vessel 100 is desired. Collector 216 may be filled completely or partially with a gas, such as air, nitrogen, or some other compressible gas. In some embodiments, the gas inside collector 216 may be set to a particular pressure such as between −2 and +2 Atmospheres. It may be desirable to limit the pressure inside collector 216 to a relatively low pressure so that pump 222 requires as little energy as possible to fill collector 216 with the incompressible fluid from reservoirs 218A and B.

[0076] The size of collector 216 and reservoirs 218A and B is selected based on the size of vessel 100 and the amount of displacement needed to overcome crush and cause vessel 100 to ascend at maximum-design depth without use of ballast tank 200. For example, if vessel 100 weighs 150 pounds, has a displacement of 18 gallons (and, therefore, approximately 145 pounds of positive buoyancy) while fully-submerged, the buoyant force provided by collector 216 should be equal or greater than approximately 5 pounds in order to cause vessel 102 ascend at the maximum-designed depth at a minimum ascent rate.

[0077] At step 602, after buoyancy engine 230 has been initialized with the incompressible fluid and the compressible gas, vessel 100 may be placed into water 120.

[0078] At step 604, processor 400 of buoyancy controller 232 may cause vessel 100 to achieve the fully-surfaced state 500 by adjusting a buoyancy of both ballast tank 200 and buoyancy engine 230, either simultaneously or sequentially. To achieve the fully-surfaced state 500, processor 400 may open valve 220 and activate pump 222, pumping any incompressible fluid that may be present within collector 216 into reservoirs 218A and B, placing collector 216 in an empty or nearly empty state, full of gas at a relatively low pressure of typically between −2 and +2 Atmospheres. When collector 216 is empty or near empty, processor 400 may deactivate pump 222 and closed valve 220, as indicated by pressure sensor 236.

[0079] Simultaneously while adjusting the buoyancy produced by buoyancy engine 230, or sequentially, processor 400 may increase the buoyancy provided by ballast tank 200 by either pumping water out of ballast tank 200 or by introducing a compressed gas inside ballast tank 200. In one embodiment, processor 400 causes valve 204 to open and system 212 to activate, causing an air pump to draw air 122 inside longitudinal channel 126 and into ballast tank 200. In another embodiment, system 212 is configured to store compressed air in an air tank of system 212, and processor 400 causes valve 204 to close and system to 212 to release an amount of the compressed air into ballast tank 200. This results in ballast tank 200 being empty or near empty, and full or nearly full of air.

[0080] At this point, vessel 100 is in fully-surfaced state 500 on top of water surface 118, with the entirety of mast 106, wing 108 fully exposed to air 122, and at least some of flotation element 104 exposed to air 122. Ballast tank 200 is filled or nearly filled with air, and collector 216 full or nearly full of the compressible gas introduced earlier. At this point, vessel 100 is at a maximum buoyancy. A graphical representation of the state of ballast tank 200, collector 216 and reservoirs 218A and B in the fully-surfaced state 500 is shown in FIG. 7. FIG. 7 shows ballast tank 200 full or nearly full of air 700, collector 216 full or nearly full of compressible gas 702 and reservoirs 218A and B, together represented as a single unit for simplicity, shown as fully or nearly-fully expanded with incompressible fluid 704. Also shown is a system 212 of compressed gas coupled to ballast tank 200 for use in an emergency ascent, which will be explained later herein.

[0081] At step 606, vessel 100 may begin navigating to a destination as programmed into a central controller, such a centralized computer programmed to control various operations of vessel 100, onboard vessel 100 prior to departure. In one embodiment, the functionality of buoyancy controller 232 may be incorporated into such a central controller. For purposes of discussion, vessel 100 is now traveling on water surface 118 in fully-surfaced state 500, either powered by wind, thruster 114, or a combination of both.

[0082] At step 608, at some time later, processor 400 of buoyancy controller 232 may receive a command from master control unit 406 to change the buoyancy of vessel 100 by a particular amount. In another embodiment, master control unit 406 simply provides one of several pre-determined commands to buoyancy controller 232, such as “go to fully-surfaced state”, “go to swamped state”, “go to fully-submerged state” (in some embodiments, also a desired depth), “prepare to dive”, “prepare to swamp”, “ascend / descend slowly”, “ascend / descend quickly”, “emergency ascent”, “increase / decrease descent rate” (to a particular rate or by a predetermined amount), etc. Each of these commands is described below.

[0083] In this example, as vessel 100 is navigating in the fully-surfaced state 500 (i.e., ballast tank 200 empty or nearly empty, collector 216 empty or nearly empty and reservoirs 218A and B full or nearly full), processor 400 of buoyancy controller 232 may receive the “prepare to swamp” command from the master control unit 406.

[0084] At step 610, in response to receiving the “prepare to swamp” command, processor 400 may decrease the buoyancy provided by buoyancy engine 230 while maintaining the buoyancy produced by ballast tank 200 as mast 106, wing 208, and a portion of flotation element 104 remain above water surface 118. This may be achieved by processor 400 causing pump 222 to activate and valve 220 to open in order to pump a prescribed amount of the incompressible fluid from reservoirs 218A and B into collector 216, thereby reducing the volume of compressible gas inside collector 216, decreasing displacement of the incompressible fluid inside collector 216 and causing a small decrease in buoyancy. FIG. 8 illustrates the state of ballast tank 200, collector 216 and reservoirs 218A and B while vessel 100 is in the “prepare to swamp” state 504, with the volume of gas 800 inside collector 216 reduced to about ⅓ the total volume of collector 216, resulting in an increased pressure inside of collector 216 of, in this embodiment, approximately 11 Atmospheres. The state of collector 216 at this point may be referred to as the neutral buoyancy state of buoyancy engine 230 at or near water surface 118. The pressure inside collector 216 at the neutral buoyancy state of buoyancy engine 230 may be selected based on the water pressure expected at a maximum dive depth, in this example, 100 meters, as the water pressure at 100 meters is approximately 11 Atmospheres. Also as shown in FIG. 8, ballast tank 200 is full or nearly full of air, the incompressible fluid occupies approximately ⅔ of the total volume of collector 216, while each of reservoirs 218A and B are deflated by approximately ⅔.

[0085] In the neutral buoyancy state of buoyancy engine 230, it may be desirable to design collector 216 to be filled with a volume of incompressible fluid greater than the volume of the compressed gas. This allows a degree of “headroom” of buoyancy at a maximum-designed depth to compensate for any crush experienced by vessel 100 at the maximum-designed depth. Specifically, as vessel 100 descends to greater depths, various components, such as flotation element 104, may lose volume due to the increasing water pressure exerted on such elements. As a result of the lost volume, displacement is reduced, therefore reducing buoyancy. If the volume of compressed air and incompressible fluid inside collector 216 at the neutral buoyancy state of buoyancy engine 230 near water surface 118 is less than two-thirds, say 50-50, then at the maximum-designed depth, some amount of the incompressible fluid may need to be pumped out of collector 216 in order to maintain a neutral buoyancy at the maximum-designed depth. If the amount of incompressible fluid inside collector 216 is low at the maximum-designed depth, then buoyancy engine 230 can only increase the buoyancy of vessel 100 by only a small amount. If vessel 100 happens to breach the maximum-designed depth, buoyancy engine 230 may not have enough incompressible fluid within collector 216 to change the buoyancy of vessel 100 in order to surface. Therefore, it may be desirable, at or near water surface 118, to establish the neutral buoyancy state of buoyancy engine 230 so that collector 216 is more than half full of incompressible fluid.

[0086] At step 612, processor 400 of buoyancy controller 232 may stop pumping the incompressible fluid from reservoirs 218A and B into collector 216 by causing pump 222 to stop pumping and causing valve 220 to close. Processor 400 may determine when to stop pumping the incompressible fluid when it receives a pressure signal from pressure sensor 236 inside collector 216. At this point, vessel 100 is in the “prepared to swamp” state where vessel 100 is still able to navigate on water surface 118 but is somewhat less buoyant in preparation to enter the swamped state.

[0087] Referring, now, back to when vessel 100 was in the fully-surfaced state 500 (i.e., ballast tank 200 empty or nearly empty, collector 216 empty or nearly empty and reservoirs 218A and B full or nearly full), at step 614, processor 400 of buoyancy controller 232 may receive the “prepare to dive” command from the master control unit 406.

[0088] At step 616, in response to receiving the “prepare to dive” command, processor 400 may minimize the buoyancy provided by buoyancy engine 230 while still maintaining mast 106, wing 208, and at least a portion of flotation element 104 above water surface 118. Processor 400 may first cause pump 222 to activate and valve 220 to open in order to fill or nearly-fill collector 216 with incompressible fluid from reservoirs 218A and B, thereby compressing the gas inside collector 216 at a maximum pressure, resulting in less displacement of the incompressible fluid and, thereby, minimizing the buoyancy provided by buoyancy engine to 230.

[0089] FIG. 9 illustrates the state of ballast tank 200, collector 216 and reservoirs 218A and B while vessel 100 is in the “prepare to dive” state 502. As shown in FIG. 9, the volume of gas 800 inside collector 216 has been reduced to a minimal amount, about only 1 / 20 the total volume of collector 216, and the pressure inside of collector 216 has increased to a maximum amount, in this example, to approximately 16 Atmospheres. This pressure is the maximum pressure experienced by collector 216 and results in the greatest reduction of buoyancy to vessel 100 as provided by buoyancy engine 230. In this configuration, buoyancy engine 230 may cause vessel 100 to descend at a maximum dissent rate when ballast tank 200 is filled with water. FIG. 9 additionally shows ballast tank 200 full or nearly full of air, the incompressible fluid occupying approximately 19 / 20 of the total volume of collector 216, while each of reservoirs 218A and B are fully or nearly deflated.

[0090] At step 618, processor 400 of buoyancy controller 232 may stop pumping the incompressible fluid from reservoirs 218A and B into collector 216 by causing pump 222 to stop pumping and causing valve 220 to close. At this point, vessel 100 is in the “prepared to dive” state 502, with vessel 100 still able to navigate on water surface 118 but somewhat less buoyant than in the “prepare to swamp” state in preparation to dive to a prescribed depth.

[0091] Referring, now, to when vessel 100 was in the “prepare to swamp” state (i.e., ballast tank 200 empty or nearly empty, collector 216 approximately two thirds filled with the incompressible fluid from reservoirs 218A and B and reservoirs 218 A and B approximately two thirds deflated), processor 400 of buoyancy controller 232 may receive the “go to swamped” state 506 command from the master control unit 406.

[0092] At step 620, in response to receiving the “go to swamped” state 506 command when vessel 100 is in the “prepare to swamp” state, processor 400 may first increase the buoyancy provided by buoyancy engine 230 and then substantially decrease the buoyancy provided by ballast tank 200. Processor 400 may open valve 220 and activate pump 222, pumping any incompressible fluid that may be present within collector 216 into reservoirs 218A and B, placing collector 216 in an empty or nearly empty state. When collector 216 is empty or near empty, processor 400 may deactivate pump 222 and closed valve 220, as indicated by pressure sensor 236. Subsequently, processor 400 may cause valve 204 to open, thereby releasing most or all of the air inside ballast tank 200 and allowing water to enter ballast tank 200 via port 202. Processor 400 may continue to maintain valve 204 in the open position until a water level sensor 238 inside ballast tank 200 indicates that the water level inside ballast tank 200 is at a level where the swamped state may be achieved, typically a level where most or all of the air inside ballast tank 200 has been evacuated from ballast tank 200 and ballast tank 200 is full or nearly full with water. Processor 400 may then cause valve 204 to close, thereby maintaining a large volume of water inside ballast tank 200. FIG. 10 illustrates the state of ballast tank 200, collector 216 and reservoirs 218A and B when vessel 100 has achieved the swamped state 506, with ballast tank 200 full or nearly full of water 120, collector 216 empty or nearly empty of incompressible fluid and reservoirs 218A and B about ⅓ full.

[0093] In some embodiments where the buoyancy of both ballast tank 200 and buoyancy engine 230 are both changed, it may be desirable to adjust the buoyancy produced by buoyancy engine 230 first before adjusting the buoyancy provided by ballast tank 200 in embodiments where vessel 100 depends on solar, wind or wave energy for its electrical needs. By first adjusting the buoyancy provided by buoyancy engine 230, vessel 100 may remain on water surface 118, continuing to collect solar energy by solar panels on wing 108 or elsewhere on vessel 100, thus continuing to charge a battery on board vessel 100 until a dive command is initiated.

[0094] In one embodiment, vessel 100 may transition from the fully-surfaced state 500 directly to the swamped state 506, as shown in FIG. 5, without having to first transition to the “prepare to swamp” state 504. In this embodiment, processor 400 receives the “go to swamped” state 506 command from the master control unit 406 and in response, may maintain the buoyancy provided buoyancy engine 230 and reduce the buoyancy provided by ballast tank 200 by causing valve 204 to open, thereby releasing most or all of the air inside ballast tank 200 and allowing water to enter ballast tank 200 via port 202.

[0095] At step 622, processor 400 of buoyancy controller 232 may receive the “dive” command from master control unit 406 for vessel 100 to achieve the dive state 508. In addition to receiving the “dive” command, processor 400 may also receive a depth from master control unit 406, indicating a depth to which vessel 100 should dive and maintain. In some embodiments, the master control unit 406 may also indicate a desired descent rate at which vessel 100 should descend. The dive command may be received while vessel 100 is in the fully-surfaced state 500, the prepared to dive state 502, the prepare to swamp state 504 or the swamped state 506.

[0096] At step 624, in response to receiving the “dive” command, processor 400 may alter the buoyancy of vessel 100 by a predetermined amount (in some embodiments, depending on the desired descent rate) by decreasing the buoyancy provided by ballast tank 200 and / or the buoyancy provided by buoyancy engine 230. For example, when vessel 100 is in the fully-surfaced state 500 or the ready to swamp state 504, processor 400 may reduce the buoyancy produced by both ballast tank 200 and buoyancy engine 230. When vessel 100 is in the ready to dive state 502, processor 400 may reduce the buoyancy of ballast tank 200 only. When in the swamped state 506, processor 400 may reduce the buoyancy of buoyancy engine 230 only. FIG. 11 illustrates this state of ballast tank 200, collector 216 and reservoirs 218A and B while vessel 100 is in the dive state.

[0097] In the case of being in the fully-surface state 500, ballast tank 200 is full or nearly full of air while collector 216 is either empty or nearly empty of incompressible fluid or semi-full of incompressible fluid, respectively. To enter dive state 508, processor 400 may first pump collector 216 full or nearly full with incompressible fluid from reservoirs 218A and B, thus compressing the air within collector 216 at a maximum pressure, occupying a minimal amount of volume within collector 216. At this point, vessel 100 is still resting on water service 118 and able to produce energy from the sun. Processor 400 may then cause valve 204 to open, thereby releasing most or all of the air inside ballast tank 200 and allowing water to enter port 202 and into ballast tank 200. At this point, a maximum amount of negative buoyancy is provided by ballast tank 200 as well as a maximum negative buoyancy provided by buoyancy engine 230, and vessel 100 descends completely underwater.

[0098] In the case of vessel 100 being in the ready to swamp state 504 when the dive command is received, ballast tank 200 is full or nearly full of water while collector 216 is empty or nearly-empty of incompressible fluid from reservoirs 218A and B, in the neutrally buoyant state of buoyancy engine 230. To enter dive state 508, processor 400 generally maintains ballast tank 200 in its present state, i.e., full or nearly full of water, and pumps collector 216 full or nearly full of incompressible fluid, thus compressing the air within collector 216 at a maximum pressure, occupying a minimal amount of volume within collector 216. At this point, a maximum amount of negative buoyancy is provided by ballast tank 200 as well as a maximum negative buoyancy provided by buoyancy engine 230, and vessel 100 descends completely underwater.

[0099] In the case of vessel 100 being in the ready to dive state 502, ballast tank 200 is full or nearly full of air while collector 216 is full or nearly full of incompressible fluid. To enter dive state 508, processor 400 causes valve 204 to open, thereby releasing most or all of the air inside ballast tank 200 and allowing water to enter port 202 and into ballast tank 200. Collector 216 is generally maintained at its full or nearly-full state. At this point, a maximum amount of negative buoyancy is provided by ballast tank 200 as well as a maximum negative buoyancy provided by buoyancy engine 230, and vessel 100 descends completely underwater.

[0100] In the case of vessel 100 being in the swamped state 506 when the dive command is received, ballast tank 200 is full or nearly full of water while collector 216 is empty or nearly-empty of the incompressible fluid. To enter dive state 508, processor 400 maintains ballast tank 200 and its current configuration, i.e., full or nearly full of water, and then opens valve 220 and activates pump 222, thereby pumping the incompressible fluid from reservoirs 218A and B into collector 216, thus compressing the air within collector 216 to a maximum pressure, occupying a minimal amount of volume within collector 216. At this point, a maximum amount of negative buoyancy is provided by ballast tank 200 as well as a maximum negative buoyancy provided by buoyancy engine 230, and vessel 100 descends completely underwater.

[0101] At step 626, as vessel 100 is descending through water 120, processor 400 may control a rate of descent of vessel 100 by adjusting the buoyancy provided by buoyancy engine to 230 alone. In one embodiment, master control unit 406 provides a desired descent rate to buoyancy controller 232. In another embodiment, a rate of dissent may be calculated by processor 400 based on one or more factors, such as a current depth of vessel 100, a target depth of vessel 100, a current location of vessel 100, etc. An actual descent rate may be monitored by processor 400 as it receives signals from depth sensor 234 located on vessel 100 via communication interface 404. For example, if the desired descent rate is-0.6 m / s, and an actual descent rate is-0.8 m / s, processor 400 may increase the buoyancy provided by buoyancy engine 230 by opening valve 220 and activating pump 222 in order to pump some amount of the incompressible fluid from collector 216 and into reservoirs 218A and B. This increases the buoyancy provided by buoyancy engine 230 thereby slowing the rate of descent. When the actual rate of descent is within a predetermined range of the desired descent rate, for example+ / −1 m / s, processor 400 may deactivate pump 222 and close valve 220, thereby preventing any further fluid from entering or leaving collector 216 and maintaining the buoyancy provided by buoyancy engine 230.

[0102] In some embodiments, when vessel 100 comprises elements that crush or deform under the water pressure as vessel 100 descends, such as flotation element 104, the actual rate of descent of vessel 100 may continuously increase as vessel 100 descends through water 120. In these embodiments, processor 400 may monitor the actual descent rate and periodically or continuously pump some amount of incompressible fluid from collector 216 into reservoirs 218A and B in order to maintain the desired rate of descent.

[0103] In some embodiments, memory 402 stores an indication of pressure or volume inside collector 216 to match a range of potential, desired descent rates when ballast tank 200 is full or nearly full with water. For example, at a desired descent rate of −0.2 m / s, the pressure within collector 216 should be 12 Atmospheres or the amount of incompressible fluid within collector 216 should occupy a little more than two thirds of the volume of collector 216. For a desired descent rate of −0.4 m / s, the pressure inside collector 216 should be 13 Atmospheres corresponding to an amount of incompressible fluid within collector 216 more than the amount of fluid at a descent rate of −0.2 m / s. Thus, when processor 400 receives the dive command and a desired rate of dissent, processor 400 pumps collector 216 with a commensurate amount of the incompressible fluid from reservoirs 218A and B, thereby achieving a particular pressure within collector 216, achieving a particular buoyancy provided by buoyancy engine 230 and causing vessel 102 dissent at the desired descent rate.

[0104] At step 628, processor 400 may determine that vessel 100 is near or at the desired depth provided by the master control unit 406.

[0105] At step 630, in response to determining that vessel 100 is near or at the desired depth, processor 400 may begin to increase the buoyancy of vessel 100 using buoyancy engine 230 alone. Specifically, processor 400 may increase the buoyancy provided by buoyancy engine 230 by causing valve 220 to open and activating pump 222 in order to cause some amount of the incompressible fluid from collector 216 back into reservoirs 218A and B. Shortly before, or when, vessel 100 achieves the desired depth, processor 400 may deactivate pump 222 and cause valve 220 to close, thereby maintaining the buoyancy provided by buoyancy engine 230 and bringing vessel 100 to the desired depth. The resulting state of ballast tank 200, collector 216 and reservoirs 218A and B when vessel 100 achieves the fully-submerged state 510 at a desired depth are shown in FIG. 12. In FIG. 12, ballast tank 200 is full or nearly full with water, collector 216 is about ⅓ full of incompressible fluid, and reservoirs 218A and B are approximately ⅔ full. At depth and neutrally buoyant, collector 216 contains a greater volume of compressed air 800 than in the swamped state, as vessel 100 may have become less buoyant due to crush at depth.

[0106] At step 632, at some time later, after vessel 100 has maintained a desired depth in the fully-submerged mode 510, processor 400 may receive an “ascend” command from the master control unit 406 via communication interface 404. In addition to receiving the “ascend” command, processor 400 may also receive a depth from master control unit 406, indicating a depth to which vessel 100 should ascend and maintain. In one embodiment, the ascend command may indicate that vessel 100 should achieve the fully-surfaced mode 500. In some embodiments, the master control unit 406 may also indicate a desired ascent rate at which vessel 100 should ascend.

[0107] At step 634, in response to receiving the “ascend” command, processor 400 may alter the buoyancy of vessel 100 by increasing the buoyancy provided by buoyancy engine 230 alone. Specifically, processor 400 may open valve 220 and activate pump 222, causing some amount of incompressible fluid to be pumped from collector 216 and into reservoirs218A and B. The greater the desired ascent rate, the more fluid is pumped out of collector 216. Thus, to achieve a maximum ascent rate, processor 400 may pump most or all of the incompressible fluid from collector 216 into reservoirs 218A and B. At this point, the state of ballast tank 200, collector 216 and reservoirs 218A and B are shown in FIG. 13 during ascent.

[0108] During a “controlled” ascent, i.e., an ascent rate less than a maximum possible ascent rate with collector 216 empty or near empty of incompressible fluid, for example, a controlled ascent rate of +0.6 m / s, processor 400 may begin pumping incompressible fluid from collector to 216 into reservoirs 218A and B while monitoring an actual ascent rate of vessel 100 using depth sensor 234 coupled to buoyancy controller 232. Pumping the incompressible fluid from collector 216 into reservoirs 218A and B requires very little energy to operate pump 222 relative to a maximum amount of energy to fill collector 216 when it is empty and at or near water surface 118, because the pressure inside collector 216 at depth is approximately the same as the water pressure exerted against reservoirs 218A and B. In one embodiment, pump 222 is not needed to transfer the incompressible fluid from collector 216 into reservoirs 218A and B. In this embodiment, as vessel 100 ascends, the water pressure acting on reservoirs 218A and B inside ballast tank 200 becomes less than the pressure inside collector 216 if valve 220 is not opened. Thus, by simply opening valve 220 during ascent, incompressible fluid may naturally flow from collector 216 to reservoirs 218A and B due to this pressure differential. This is a very advantageous configuration, as little or no power is needed to cause ascension of vessel 100 at depth.

[0109] When the actual ascent rate is at, or within a predetermined amount from, a desired ascent rate, processor 400 stops pumping the incompressible fluid from collector 216 into reservoirs 218A and B and continues to monitor the actual rate of ascent. If the actual rate of ascent is within a predetermined range, such as + / −0.1 m / s, processor 400 may take no further action and continue monitoring the actual rate of the ascent. However, if the actual rate of ascent is greater than the predetermined range, processor 400 will cause either an increase or a decrease in the buoyancy provided by buoyancy engine 230 only depending on whether the actual ascent range needs to be reduced or increased, respectively. This process may be performed periodically or continuously in order to keep the actual ascent rate of vessel 100 within the predetermined ascent range.

[0110] At step 636, processor 400 may determine that vessel 100 is near or at the desired depth provided by master control unit 406, typically by monitoring depth sensor 234 located onboard vessel 100.

[0111] At step 638, in response to determining that vessel 100 is near or at the desired depth, processor 400 may begin to decrease the buoyancy of vessel 100. Specifically, processor 400 may decrease the buoyancy provided by buoyancy engine 230 alone by activating pump 222 and causing valve 220 to open, thereby pumping at least some of the incompressible fluid from reservoirs 218A and B into collector 216, thus decreasing the volume of compressed air 800 inside collector 216 and, thus, reducing the buoyancy provided by buoyancy engine 230. This causes the rate of ascent to slow and then stop, causing vessel 100 to achieve the desired depth in the fully-submerged state.

[0112] At step 640, when the desired depth comprises the fully-surfaced state 500, i.e. depth=0, and vessel 100 is at a depth associated with the swamped state 506, processor 400 may achieve the fully-surfaced state 500 by opening valve 220 and activating pump 222 in order to expel most or all of the incompressible fluid within collector 216 into reservoirs 218A and B, thereby providing maximum buoyancy from buoyancy engine 230. Additionally, processor 400 may open valve 204 and activating system 212, drawing air 122 through longitudinal channel 126 and into ballast tank 200. As air is forced into ballast tank 200, water inside ballast tank 200 is expelled via port 202 and ballast tank 200 is filled completely or nearly completely with air in order to provide a maximum amount of buoyancy to vessel 100, thereby causing vessel 100 to achieve the fully-surfaced state 500.

[0113] At step 642, returning to when vessel 100 is in the fully-submerged state 510, at step 638, processor 400 may receive an “emergency ascent” command from the master control unit 406. This command may be issued upon determining that the vessel 100's battery life is lower than a predetermined threshold, which may threaten vessel 100's ability to surface, upon determining a failure of ballast tank 200 and / or buoyancy engine 230, upon determining the presence of an underwater threat, such as the approach or presence of a large marine animal, submarine, other autonomous underwater vehicle, etc.

[0114] At step 644, in response to receiving the emergency ascent command, processor 400 may cause valve 204 to close if it is open and to cause system 212 to release most or all of its compressed gas into ballast tank 200. This causes a large volume of water to exit ballast tank 200 via port 202 while ballast tank 200 fills with the compressed gas, whereupon vessel 100 begins ascending at a rapid rate. FIG. 14 illustrates the state of system 212, ballast tank 200, collector 216 and reservoirs 218A and B while vessel 100 is in the emergency ascent state. Note that the state of collector 216 and reservoirs 218A and B is a “don't care” state as depicted in FIG. 14, as it does not matter what state any of these components are in, because system 212 is sized such that vessel 100 may be surfaced using only the buoyancy created by the compressed air 1400 inside ballast tank 200. However, in other embodiments, processor 400 may additionally increase the buoyancy provided by buoyancy engine 230 by opening valve 220 and pumping most or all of the incompressible fluid inside collector 216 out of collector 216 and into reservoirs 218A and B. This causes additional positive buoyancy to the buoyancy provided by ballast tank 200, aiding in resurfacing vessel 100.

[0115] Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Other technical advantages may become readily apparent to one of ordinary skill in the art after review of the foregoing figures and description.

[0116] It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described above, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described above.

[0117] Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set. The article “a” means “one or more”.

[0118] In many places in this document, actions (e.g., functionality) are performed by one or more processors executing processor-executable instructions (i.e., software, firmware). This is done for ease of description; it should be understood that, whenever it is described in this document that software performs any action, the action is in actuality performed by underlying hardware elements (such as a processor and a memory device) according to the instructions that comprise the software. Such functionality may, in some embodiments, be provided in the form of firmware and / or hardware implementations.

[0119] The elements described in this document include actions, features, components, items, attributes, and other terms. Whenever it is described in this document that a given element is present in “some embodiments,”“various embodiments,”“certain embodiments,”“certain example embodiments, “some example embodiments,”“an exemplary embodiment,”“an example,”“an instance,”“an example instance,” or whenever any other similar language is used, it should be understood that the given element is present in at least one embodiment, though is not necessarily present in all embodiments. Consistent with the foregoing, whenever it is described in this document that an action “may,”“can,” or “could” be performed, that a feature, element, or component “may,”“can,” or “could” be included in or is applicable to a given context, that a given item “may,”“can,” or “could” possess a given attribute, or whenever any similar phrase involving the term “may,”“can,” or “could” is used, it should be understood that the given action, feature, element, component, attribute, etc. is present in at least one embodiment, though is not necessarily present in all embodiments. Terms and phrases used in this document, and variations thereof, unless

[0120] otherwise expressly stated, should be construed as open-ended rather than limiting. As examples of the foregoing: “and / or” includes any and all combinations of one or more of the associated listed items (e.g., a and / or b means a, b, or a and b); the singular forms “a”, “an”, and “the” should be read as meaning “at least one,”“one or more,” or the like; the term “example”, which may be used interchangeably with the term embodiment, is used to provide examples of the subject matter under discussion, not an exhaustive or limiting list thereof; the terms “comprise” and “include” (and other conjugations and other variations thereof) specify the presence of the associated listed elements but do not preclude the presence or addition of one or more other elements; and if an element is described as “optional,” such description should not be understood to indicate that other elements, not so described, are required.

[0120] As used herein, the term “non-transitory computer-readable storage medium” includes a register, a cache memory, a ROM, a semiconductor memory device (such as D-RAM, S-RAM, or other RAM), a magnetic medium such as a flash memory, a hard disk, a magneto-optical medium, an optical medium such as a CD-ROM, a DVD, or Blu-Ray Disc, or other types of volatile or non-volatile storage devices for non-transitory electronic data storage. The term “non-transitory computer-readable storage medium” does not include a transitory, propagating electromagnetic signal.

[0121] The claims are not intended to invoke means-plus-function construction / interpretation unless they expressly use the phrase “means for” or “step for.” Claim elements intended to be construed / interpreted as means-plus-function language, if any, will expressly manifest that intention by reciting the phrase “means for” or “step for”; the foregoing applies to claim elements in all types of claims (method claims, apparatus claims, or claims of other types) and, for the avoidance of doubt, also applies to claim elements that are nested within method claims. Consistent with the preceding sentence, no claim element (in any claim of any type) should be construed / interpreted using means plus function construction / interpretation unless the claim element is expressly recited using the phrase “means for” or “step for.”

[0122] Whenever it is stated herein that a hardware element (e.g., a processor, a network interface, a display interface, a user input adapter, a memory device, or other hardware element), or combination of hardware elements, is “configured to” perform some action, it should be understood that such language specifies a physical state of configuration of the hardware element(s) and not mere intended use or capability of the hardware element(s). The physical state of configuration of the hardware elements(s) fundamentally ties the action(s) recited following the “configured to” phrase to the physical characteristics of the hardware element(s) recited before the “configured to” phrase. In some embodiments, the physical state of configuration of the hardware elements may be realized as an application specific integrated circuit (ASIC) that includes one or more electronic circuits arranged to perform the action, or a field programmable gate array (FPGA) that includes programmable electronic logic circuits that are arranged in series or parallel to perform the action in accordance with one or more instructions (e.g., via a configuration file for the FPGA). In some embodiments, the physical state of configuration of the hardware element may be specified through storing (e.g., in a memory device) program code (e.g., instructions in the form of firmware, software, etc.) that, when executed by a hardware processor, causes the hardware elements (e.g., by configuration of registers, memory, etc.) to perform the actions in accordance with the program code.

[0123] A hardware element (or elements) can therefore be understood to be configured to perform an action even when the specified hardware element(s) is / are not currently performing the action or is not operational (e.g., is not on, powered, being used, or the like). Consistent with the preceding, the phrase “configured to” in claims should not be construed / interpreted, in any claim type (method claims, apparatus claims, or claims of other types), as being a means plus function; this includes claim elements (such as hardware elements) that are nested in method claims.

[0124] Although process steps, algorithms, or the like, may be described or claimed in a particular sequential order, such processes may be configured to work in different orders. In other words, any sequence or order of steps that may be explicitly described or claimed in this document does not necessarily indicate a requirement that the steps be performed in that order; rather, the steps of processes described herein may be performed in any order possible. Further, some steps may be performed simultaneously (or in parallel) despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modifications thereto, does not imply that the illustrated process or any of its steps are necessary, and does not imply that the illustrated process is preferred.

[0125] Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above description should be read as implying that any particular element, step, range, or function is essential. All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the invention. No embodiment, feature, element, component, or step in this document is intended to be dedicated to the public.

Claims

1. A submersible vessel, comprising:a ballast tank for causing large changes in a buoyancy of the submersible vessel;a buoyancy engine for causing smaller changes in buoyancy of the submersible vessel less than the large changes; anda buoyancy controller for altering the buoyancy of the submersible vessel using both the ballast tank and the buoyancy engine to achieve different depths by the submersible vessel.

2. The submersible vessel of claim 1, wherein the submersible vessel further comprises:a hull for housing at least the buoyancy engine;wherein the buoyancy engine comprises:a collector;a reservoir coupled to the collector via a value;an incompressible fluid inside the collector and / or the reservoir;a compressible gas located inside the collector; anda pump to force the incompressible fluid between the collector and the reservoir;wherein the submersible vessel is capable of operation in a swamped state, wherein the swamped state comprises a state where the hull is fully submerged beneath a water surface and at least another portion of the submersible vessel protrudes from a surface of water, and wherein the buoyancy controller is further configured to:initiate a descent of the submersible vessel to the swamped state by:first causing the pump to pump at least some of the incompressible fluid out of the collector and into the reservoir; andthen causing the ballast tank to fill substantially with water.

3. The submersible vessel of claim 2, wherein the submersible vessel is additionally capable of operation in a fully-submerged state, wherein the fully-submerged state comprises a state where the submersible vessel is entirely submerged beneath a water surface, wherein the buoyancy controller is further configured to:initiate a descent of the submersible vessel to the fully-submerged state by:first causing the pump to move most or all of the incompressible fluid in the reservoir into the collector; andthen causing the ballast tank to fill substantially with water.

4. The submersible vessel of claim 3, wherein the buoyancy controller is further configured to:initiate an ascent of the submersible vessel at a maximum rate of ascent from the fully-submerged state by maintaining any water in the ballast tank and causing the pump to force most or all of the incompressible fluid from the collector into the reservoir.

5. The submersible vessel of claim 4, wherein the buoyancy controller is further configured to:initiate an ascent of the submersible vessel at a rate of ascent less than the maximum rate of ascent by maintaining any water in the ballast tank and causing the pump to force any amount of the incompressible fluid from the collector to the reservoir less than an amount that would leave the collector empty or nearly-empty.

6. The submersible vessel of claim 2, wherein the ballast tank comprises a port for allowing water to enter the hull, and the reservoir is located within the hull and in contact with water in the ballast tank.

7. The submersible vessel of claim 1, wherein the submersible vessel is capable of operation in a swamped state, the submersible vessel further comprising:a hull;a mast having one end coupled to the hull; anda wing coupled to the mast;wherein the swamped state comprises a state where the hull is fully submerged beneath the water surface and the mast and wing protrude at least partially from the water surface, wherein the buoyancy controller is further configured to:initiate a descent of the submersible vessel to the swamped state by:first causing most or all of the incompressible fluid out of the collector and into the reservoir; andthen causing the ballast tank to fill substantially with water.

8. The submersible vessel of claim 7, further comprising:an air pump;wherein the ballast engine comprises:a collector;a reservoir coupled to the collector via a value;an incompressible fluid inside the collector and / or the reservoir;a compressible gas located inside the collector; anda pump to force the incompressible fluid between the collector and the reservoir;wherein the mast is hollow, comprising a longitudinal channel having a first end coupled to the ballast tank and a second end exposed to air when the submersible vessel is in the swamped state or a fully-surfaced state, wherein the buoyancy controller is further configured to:determine that the submersible vessel has achieved the swamped state;in response to determining that the submersible vessel has achieved the swamped state:activate the air pump to draw air into the longitudinal channel, through the mast, and substantially fill the ballast tank with air; andactivate the pump to force most or all of the incompressible fluid out of the collector and into the reservoir.

9. The submersible vessel of claim 1, further comprising:a gas cartridge coupled to the ballast tank, the gas cartridge filled with a compressed gas;wherein the buoyancy controller is further configured to:determine an adverse condition of the submersible vessel while the submersible vessel is in a fully-submerged state; andin response to determining an adverse condition of the submersible vessel while the submersible vessel is in a fully-submerged state, activate the gas cartridge, causing the compressed gas in the gas cartridge to enter the ballast tank for emergency resurfacing.

10. The submersible vessel of claim 1, wherein the buoyancy engine comprises:a collector;a reservoir coupled to the collector via a value;an incompressible fluid inside the collector and / or the reservoir;a compressible gas located inside the collector;a pump to force the incompressible fluid between the collector and the reservoir;wherein the compressible gas occupies about one-third of the collector volume and the incompressible fluid occupies about two-thirds of the collector volume when the vessel is neutrally buoyant near a surface of water.

11. The submersible vessel of claim 10, wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:causing the ballast tank to fill substantially with water;initially activating, by the buoyancy controller, the pump to fill the collector more than half-way full of the incompressible fluid, thus causing the submersible vessel to descend underneath the surface of the water;after initiating descent, monitoring a rate of descent of the submersible vessel; andwhen the submersible vessel approaches a desired depth, activating, by the buoyancy controller, the pump to expel at least some of the incompressible fluid from the collector into the reservoir to increase the buoyancy of the submersible vessel.

12. The submersible vessel of claim 10, wherein the buoyancy engine further comprises:a valve coupled between the collector and the reservoir, controllable by the buoyancy controller;wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:causing the value to open, allowing the compressible gas in the collector to push the incompressible fluid into the reservoir without using the pump.

13. The submersible vessel of claim 2, further comprising:a depth gauge coupled to the buoyancy controller;wherein the hull comprises a crushable material, causing the buoyancy of the submersible vessel to change with respect to a depth of the submersible vessel, wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:determining a depth of the submersible vessel as the submersible vessel dives beneath the water surface; andactivating the pump to expel a predetermined amount of the incompressible fluid from the collector into the reservoir in accordance with the depth.

14. A method for controlling buoyancy of a submersible vessel, comprising:adjusting a first buoyancy produced by a ballast tank of the submersible vessel that causes large changes in buoyancy of the submersible vessel;adjusting a second buoyancy produced by a buoyancy engine of the submersible vessel for causing smaller changes in buoyancy of the submersible vessel less than the large changes; andadjusting the buoyancy of the submersible vessel by adjusting both the first and second buoyancies due to the ballast tank and the buoyancy engine, respectively.

15. The method of claim 14, wherein the submersible vessel is capable of operation in a swamped state, wherein the swamped state comprises a state where the hull is fully submerged beneath a water surface and at least another portion of the submersible vessel protrudes from a surface of water, the method further comprising:initiating a descent of the submersible vessel to the swamped state by:first causing a fluid pump to pump at least some of an incompressible fluid out of a collector of the buoyancy engine and into a reservoir of the buoyancy engine; andthen causing the ballast tank to fill substantially with water.

16. The method of claim 15, wherein the submersible vessel is additionally capable of operation in a fully-submerged state, wherein the fully-submerged state comprises a state where the submersible vessel is entirely submerged beneath a water surface, the method further comprising:initiating a descent of the submersible vessel to the fully-submerged state by:first causing the pump to move most or all of the incompressible fluid in the reservoir into the collector; andthen causing the ballast tank to fill substantially with water.

17. The method of claim 16, further comprising:initiating an ascent of the submersible vessel at a maximum rate of ascent from the fully-submerged state by maintaining any water in the ballast tank and causing the pump to force most or all of the incompressible fluid from the collector into the reservoir.

18. The method of claim 17, further comprising:initiating an ascent of the submersible vessel at a rate of ascent less than the maximum rate of ascent by maintaining any water in the ballast tank and causing the pump to force any amount of the incompressible fluid from the collector to the reservoir less than an amount that would leave the collector empty or nearly-empty.

19. The method of claim 14, wherein the submersible vessel is capable of operation in a swamped state, wherein the swamped state comprises a state where a hull of the submersible vessel is fully submerged beneath the water surface and a mast and a wing of the submersible vessel protrudes at least partially from the water surface, the method further comprising:initiating a descent of the submersible vessel to the swamped state by:first causing most or all of an incompressible fluid inside a collector of the buoyancy engine into a reservoir of the buoyancy engine; andthen causing the ballast tank to fill substantially with water.

20. The method of claim 19, further comprising:determining that the submersible vessel has achieved the swamped state;in response to determining that the submersible vessel has achieved the swamped state:activating an air pump to draw air into a longitudinal channel of a mast of the submersible vessel coupled to the ballast tank, and substantially filling the ballast tank with air; andactivating a fluid pump to force most or all of the incompressible fluid out of the collector and into the reservoir.

21. The method of claim 14, further comprising:determining that the submersible vessel has suffered an adverse condition while in a fully-submerged state; andin response to determining that the adverse condition has occurred, activating a gas cartridge filled with a compressed gas, causing the compressed gas in the gas cartridge to enter the ballast tank for emergency resurfacing.

22. The method of claim 14, wherein a compressible gas inside a collector of the buoyancy engine occupies about one-third of the collector volume and an incompressible fluid occupies about two-thirds of the collector volume when the submersible vessel is neutrally buoyant near a water surface.

23. The method of claim 22, wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:causing the ballast tank to fill substantially with water;initially activating, by the buoyancy controller, a fluid pump to fill the collector more than half-way full of the incompressible fluid, thus causing the submersible vessel to descend underneath the surface of the water;after initiating descent, monitoring a rate of descent of the submersible vessel; andwhen the submersible vessel approaches a desired depth, activating, by the buoyancy controller, the fluid pump to expel at least some of the incompressible fluid from the collector into the reservoir to increase the buoyancy of the submersible vessel.

24. The method of claim 22, wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:causing a value coupled to the collector, to open, allowing the compressible gas in the collector to push the incompressible fluid into the reservoir without using the pump.

25. The method of claim 15, wherein the submersible comprises a crushable material, causing the buoyancy of the submersible vessel to change with respect to a depth of the submersible vessel, wherein altering the buoyancy of the submersible vessel by the buoyancy controller comprises:determining a depth of the submersible vessel as the submersible vessel dives beneath the water surface; andactivating the fluid pump to expel a predetermined amount of the incompressible fluid from the collector into the reservoir in accordance with the depth.

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