Abstract:
A submersible able to maintain one atmosphere of pressure throughout its operating envelope with the capacity to maintain a habitable atmosphere through its capability of rapid transit between underwater operating areas and the water&#39;s surface so as to replenish habitable air via a system of ducting, valves, and fans. The submersible is comprised of a towing and stability system that can vary stability about the submersible&#39;s longitudinal axis by selectively clutching or declutching the submersible&#39;s minimally stable crew compartment to the submersible&#39;s more stable bow hull, as controlled by the submersible&#39;s operator. The towing and stability system also provides the ability to propel the submersible underwater along a path of the operator&#39;s selection by aligning the tow vector within proximity of the center of gravity and then steering the submersible in three dimensions by articulating a plurality of hydroplanes which enact moments upon the submersible, thereby controlling its path.

Description:
FIELD 
       [0001]    The present disclosure describes a towable, pressurized, positive-buoyancy submersible with a capability for surface air replenishment. 
       BACKGROUND 
       [0002]    In 1573, Englishman William Bourne published the first design for a submersible boat featuring a mast that could operate as a snorkel. Bourne is not believed to have ever constructed this vessel, but in 1620, Dutchman Cornelius van Drebbel built a wooden and leather submarine that could operate under the surface of the water, propelled by oars, with air supplied through snorkels. For the next several centuries, scores of submarine designs came and went, the primary purpose of these inventions, to act as a tool of warfare. These haphazard devices were generally more dangerous to their crews than their adversaries. 
         [0003]    In the mid nineteenth century, Captain Giovanni Luppis of the Austrian Navy and British engineer Robert Whitehead developed the first torpedo, a weapon ideally suited for the submarine, and the torpedo&#39;s advent accelerated the submarine&#39;s development. In 1864, Spanish designer Narcis Monturiol built the first combustion powered submarine, but it took several decades before the submarine found true military utility. Over the next century, many designs and modes of propulsion and weaponry ensued, culminating in the immense nuclear powered and armed submarines of the post World War II era. 
         [0004]    In 1942, Jacque Cousteau developed the first commercially successful SCUBA apparatus, and though Cousteau was acting in his capacity as a French Naval officer, he eventually became an icon of civilian underwater exploration and discovery. 
         [0005]    As civilian interest and access to the underwater world intensified, a variety of schemes for travel below the ocean&#39;s surface developed, from diving bells and bathyscapes to extreme deep water remotely operated submarines. Despite the great success, popularity and relative affordability of SCUBA diving, access afforded by submersibles has only come to homebuilders, those of affluence, or to those with bonafide commercial interests below the sea. The great advantage of the human body over an underwater structure is that the human body can negate pressure differential by equalizing against external pressure with compensating pressure from within. Unfortunately, human physiology has limits in its tolerance of the effects of high pressure gasses once inside the body. SCUBA divers may also find the high thermal demands of being underwater objectionable, have little tolerance for rapid pressure changes, and have very limited levels of power available for locomotion. 
         [0006]    Submersibles that can remain watertight and maintain structural integrity in the face of differential water pressure at depth have many advantages over SCUBA. Today, homebuilders are able to create their own submarines out of parts costing less than $10,000, but because of complex systems of reliable and safe propulsion, structure, and life support, the state of the art demands a minimum cost of approximately $350,000 for a commercially available dry, one atmosphere, personal submersible that is certified safe by an appropriate agency. For that price, the vehicle will have very little maneuverability and a top speed of less than five mph. Faster, more maneuverable personal subs are available, but at purchase prices that exceed $1 million. 
       SUMMARY OF THE INVENTION 
       [0007]    The limitations of prior art have led to stagnation of the submersible industry and by extension, its technology. The present invention greatly increases maximum speed and maneuverability while simultaneously lowering submersible cost, offering the potential to bring both affordability and improved function to the submersible industry. According to one embodiment of the invention, an enclosed steel shell, designed to maintain one atmosphere of internal pressure at the submersible&#39;s rated depth, is surrounded by a fiberglass hull designed to minimize hydrodynamic drag. Further, a segment of the free space between the steel shell and the fiberglass hull may be occupied by air such that the vessel floats higher in water, facilitating entry and exit of the submersible. According to routine practice, one or more pumps may then fill said space with water such that the vessel may float lower in the water to facilitate diving below the water&#39;s surface. 
         [0008]    According to another embodiment, the submersible may be comprised of two dive-planes located near the vessel&#39;s center of gravity and four tail-planes located toward the aft end of the vessel. Through operator controls, all six planes articulate about their respective spars to vary each planes&#39; respective lift, providing the operator with a means to rotate the entire submersible and its velocity vector about all three cardinal axes. And in another embodiment, a tow system comprised of a tether, cables, and rotational elements maintains proximity of the tow vector near the submersible&#39;s center of gravity, thereby facilitating improved rotational authority of the submersible and its velocity vector by said dive-planes and tail-planes. 
         [0009]    In a further embodiment, a variable stability system comprised of rotational elements of the tow system and fixed ballast located in the bottom of the submersible&#39;s bow hull, accommodates a state of high longitudinal stability for entry and exit of the submersible by locking the submersible&#39;s rotational elements such that the weight in the bottom of the submersible&#39;s bow hull contributes to lowering its center of gravity thereby distancing the submersible&#39;s center of gravity from its center of buoyancy. To decrease stability and enhance maneuvering capability, the vessel operator may declutch the bow hull from the remainder of the submersible, thereby freeing rotational elements thereby decoupling the fixed ballast weight in the bow hull, thereby bringing the effective center of gravity closer to the center of buoyancy and thus removing stabilizing torque about the submersible&#39;s longitudinal axis. 
         [0010]    In this and other embodiments, one or more transparent domes, which may be comprised of acrylic, may function as vessel windows and may also be housed in a hinged structure for entry and exit of the vessel such that when said window structures are sealed against the steel shell, the free space within the steel shell is contained from surrounding water and can be maintained at one atmosphere of pressure. 
         [0011]    In yet another embodiment, the steel shell comprises seating to accommodate at least one person and a life support system which may itself be comprised of components within and outside the steel shell. In this and other embodiments, one or more Human Machine Interfaces may control electronic systems that may facilitate appropriate management of said systems for operation of the submersible. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    Features and advantages of the claimed subject matter will be apparent from the following detailed description of embodiments consistent therewith, which description should be considered with reference to the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a side view illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0014]      FIG. 2   a  is an expanded view of the snorkel system illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0015]      FIG. 2   b  is an expanded view of the internal components of the snorkel system illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0016]      FIG. 3  is a top view illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0017]      FIG. 4  illustrates four different perspective views of the submersible; 
           [0018]      FIG. 5  is a top view of the steel shell and various components; 
           [0019]      FIG. 6  is a side view of the steel shell and various components; 
           [0020]      FIG. 7  is a lower perspective view of the steel shell and various components; 
           [0021]      FIG. 8  is a view of various components of the tow system illustrating one embodiment of the submersible in accordance with the present disclosure; 
           [0022]      FIG. 9  is a view of the tow tether and various components; 
           [0023]      FIG. 10  is a bottom view illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0024]      FIG. 11  is a front view illustrating one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0025]      FIG. 12   a  is a diagram of the dive planes and their respective spars; 
           [0026]      FIG. 12   b  is a diagram resembling both the pitch planes and the yaw planes and their respective spars; 
           [0027]      FIG. 13  is a side view of one exemplary embodiment illustrating internal components of the submersible in accordance with the present disclosure; 
           [0028]      FIG. 14  is a top view of one exemplary embodiment of the submersible in accordance with the present disclosure; 
           [0029]      FIG. 15  is a schematic of electrical switch functions organized according to bus location as may be seen in an exemplary embodiment of the submersible in accordance with the present disclosure; and 
           [0030]      FIG. 16  is a rear perspective view of the bow hull illustrating one exemplary embodiment of the submersible in accordance with the present disclosure. 
       
    
    
       [0031]    Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. 
       DETAILED DESCRIPTION 
       [0032]    Generally, this disclosure relates to a personal submersible having a reduced cost with a maximum speed and maneuverability well beyond what is currently available. This disclosure thus provides an underwater transport capable of underwater exploration for purposes including but not limited to discoveries of science and salvage, criminal and civil investigation, underwater inspection of marine vessels and other man-made equipment and construction, observation of underwater plant, animal, and geologic phenomena for scientific and recreational purposes, and may also include military, defense, and other applications particularly relevant to non-clandestine underwater surveillance. 
         [0033]    In the interest of appreciating the scale and scope of the present disclosure, the following dimensions and operating specifications are listed; however, they should not be construed as to limit the scope, scale, or spirit of this disclosure in any manner:
       Length: 258 inches   Beam: 41 inches   Canopy external diameter: 28 inches   Displacement: 8450 lbs. seawater   Empty weight (estimated): 6175 lbs.   Operating weight while diving: 8325 lbs.   Maximum operating depth: 300 feet   Maximum speed: 25 mph (22 knots)   Minimum speed for submergence: 2 mph (1.5 knots)   Maximum bottom time (without supplemental life support): 14 minutes (will vary based upon conditions)       
 
         [0044]    In particular, the above specifications are specific to a two-seat submersible, but no part of this disclosure should be viewed as limiting to two occupants. For example, it is well within the scope and spirit of the disclosure that it should not be limited in size or occupancy, such that a submersible of this design may carry one, three, four or more occupants and/or operators. It is also within the scope and spirit of the disclosure that the submersible might carry no people and that it may operate autonomously, or that it may carry one or more passengers and all or part of the submersible&#39;s controlling operations might originate from an internal processor or an individual or processor outside of the submersible. 
         [0045]      FIGS. 1 and 3  depict the side and top views respectively of a preferred embodiment and present scope and scale of the disclosure. Likewise, the views presented in  FIG. 4  depict four perspectives that illustrate a not entirely unfamiliar presentation of a hydrodynamically faired, tandem-canopy arrangement with two larger dive planes  11  at the mid-body and four smaller tail planes  12  and  4  arranged at 90 degree intervals at the tail. For those talented in the art, it becomes immediately apparent that the dive planes, sitting close to the submersible&#39;s center of gravity (CG), may be employed to present a large force normal to their respective chord lines which could be of use in diving a positively buoyant submersible. It is also apparent that the two pitch planes  12  and two yaw planes  4 , all being far away from the CG, may be employed to generate moments about the CG in all three cardinal axes, thereby offering a method of directional control. Hydroplane fairings  5  provide a smooth transition from submersible body to each respective tail plane. Occupants or operators may sit underneath canopies  1  in seats  105  as depicted in  FIG. 13 . The two canopies  1  may pivot at hinges  6  and are arranged to function as both windows and hatches. In some embodiments, the canopies may be protected by external, conformal steel bars or bars constructed of similarly strong material. The canopies may further be protected either internally or externally by transparent covers or film. In some embodiments, computer monitors  107  may present data and provide an interface to control submersible electronic components. In a preferred embodiment, the seat is adjustable in fore and aft, seat angle, and vertical space. 
         [0046]    Two snorkels,  2  and  3 , offer the first glimpse of the novelty of the design, and two tow arms  32 , offer another subtle clue as to the advance in state of the art. The embodiment depicted in  FIG. 8  demonstrates that the submersible may be towed via a tether  73  towed by a surface vessel with sufficient horsepower and structural integrity to move both surface vessel and submersible. In some embodiments, the vessel may be towed with a steel cable or rigid line, or some combination of elasticized and rigid chord, line and or cable. Referring to an embodiment depicted in  FIG. 9 , the shock bungee  74  absorbs momentary jerk loads, and in the case of excessive tow loads, the weak link  75  may break, thereby preventing damage to other submersible components. In a preferred embodiment depicted in  FIG. 8 , the tether  73  attaches to the tow ring  72  which pulls the bridle cable  71 . The bridle cable attaches to both tow arms  32  at a position near the submersible&#39;s center of gravity so that lesser moments are required to rotate the vessel about any particular axis. As the submersible&#39;s tow angle varies, the tow ring  72  slides along the bridle cable  71  imparting similar towing forces on each respective tow arm  32  such that the tow force vector&#39;s lateral component is minimized throughout the submersible&#39;s operational envelope such that this may in turn produce a minimal moment about the submersible&#39;s longitudinal axis. In this way, tow forces may impart little or no rotation about the submersible&#39;s longitudinal axis. 
         [0047]      FIGS. 6-7  depict a preferred embodiment in which the tow arms  32  attach to the tow cross  34 .  FIG. 16  depicts the forward 50 inches of the hull, herein labeled the bow hull  48 , internally comprised of a bearing bulkhead  49  which secures the bow hull to the remainder of the submersible in that the bearing bulkhead  49  is sandwiched between the tow cross  34  and the bow plate  43 . In a preferred embodiment, the bottom of the bow hull may be filled with a mixture of lead shot and epoxy so that the center of gravity of the bow hull is very low. This lead epoxy mixture may occupy the hard ballast containment area  106 , depicted in  FIG. 13 . It can now be seen in this embodiment that in static conditions as well as when tow forces are applied to the submersible, the bow hull remains stable with respect to the submersible&#39;s longitudinal axis. The bow hull  48  is secured to the remainder of the submersible at the outer race of the tow bearing  33 , the inner race of which mounts around the bearing support shaft  31  which is permanently secured to the steel shell. So it can be further seen that when the bow hull is travelling without rotation in the longitudinal axis, the steel shell and all that it is comprised of, to include the operator, any other passengers, and the remainder of the hull, may all be permitted to rotate freely about the submersible&#39;s longitudinal axis. 
         [0048]      FIG. 5  depicts an additional embodiment in which a pin actuator  38  inserts a pin into the bow plate  43 , locking the bow hull  48  to the remainder of the submersible which effectively lowers the entire submersible&#39;s center of gravity. It is therefore understood by those knowledgeable in the art that the locked assembly has greater stability about the longitudinal axis, which may be useful for the purpose of entrance and exit as well as reducing oscillations in rough seas or at other times when conditions warrant a more stable vessel. In some embodiments, though, a clutch or brake assembly or some other simple device that eliminates rotation of the tow bearing may be employed to lock the bow hull to the remainder of the submersible. 
         [0049]    In some embodiments, a ring bearing or a slewing ring bearing may be mounted around the submersible such that one or more attach points are secured to said bearing. In such an embodiment, the bearing rotates relative to the remainder of the submersible, and thus the bow hull may be fixed to the remainder of the submersible hull. In one embodiment, an assembly may be built, supported by such a ring bearing to carry ballast, such that variable stability may be achieved by selectively locking the submersible to said ballast. Other devices that permit low-friction rotation about the submersible&#39;s longitudinal axis may be employed to attach towing hardware to position a vessel&#39;s tow vector close to its CG while permitting vessel rotation, but such devices would be encompassed by the scope of the invention described herein. Likewise, other modes of varying the submersible&#39;s static stability, such as placing ballast upon an actuator to vary its vertical position, may be envisioned by those of average skill in the related art, but would not materially alter the scope of the invention. 
         [0050]    In some embodiments, foot actuated rudder pedals may direct movement of two independently operated yaw planes  4 , as may be viewed in  FIG. 1 .  FIG. 12   b  depicts an embodiment of the yaw planes as they might be seen if removed from the submersible. The submersible&#39;s planes may be comprised of a foil section and a structural spar  16 . Rotation of the yaw planes about the spar  16  may impart hydrodynamic lift normal to the chord line of the planes which may rotate the entire submersible in yaw. In some embodiments, a joystick  104 , as may be seen in  FIG. 13 , manipulated by an operator, may control two independently operated pitch planes  12 , as seen in  FIG. 3  which may be pivoted about their respective central spars to vary each pitch plane&#39;s lift. Varying the lift of the pitch planes in a symmetric fashion may be seen to impart a pitch moment upon the submersible and its velocity vector. Alternatively, asymmetric lift of the pitch planes or yaw planes may be seen to impart a roll moment about the submersible&#39;s longitudinal axis. And in some embodiments, an electronic processor may use joystick position and rudder pedal position to compute desired positions for each individual hydrofoil independently such that torque and torsion originating at the tail planes dictates rotational control of the submersible about all three cardinal axes. 
         [0051]    Those knowledgeable in the art will realize that as long as the submersible, acting as a hydrodynamic body, does not suffer a condition of hydrodynamic stall, the path of the submersible will align within proximity of the direction the submersible is pointed such that the submersible operator can control its path by pointing the submersible towards the desired direction using the joystick  104  and rudder pedals. It is further understood that a three axis joystick could supplant the need for rudder pedals and that there may be any other manner of interface device that could be employed to control the motion of the planes. 
         [0052]    In other embodiments, the operator may dive the submersible by control of two dive-planes  11  which may travel at a downward angle of attack by pivoting around their respective central spars  15  to vary both hydrofoils&#39; lift. The dive planes  11  may be used to trim the submersible&#39;s pitch attitude for various conditions. In some embodiments, the dive planes may be rotated asymmetrically to command rotation of the submersible about its longitudinal axis, and this force may act to supplement or counteract rotational moments commanded by the pitch planes  12  or yaw planes  4 . 
         [0053]    It is understood now by those knowledgeable in the art that the tow system described herein operating in conjunction with the variable stability system also described herein comprise the submersible&#39;s towing and stability system, said system functioning to permit maneuvering at high rotational velocities when desired, and at other times, providing for a stable, relatively rotation free platform for activities such as entry and exit. 
         [0054]    Depending upon ballast configuration and vessel attitude, the operator may use any combination of dive plane, pitch or even yaw input to submerge the submersible. In some embodiments, the submersible may be operated at positive buoyancy and may use the force of the dive plane, as well as hydrodynamic force on the submersible&#39;s hull, for submersion. Therefore, in some embodiments, any time the towing vessel ceases to tow the submersible, it may automatically surface, offering inherent safety to its operation. 
         [0055]      FIGS. 2   a  and  2   b  herein depict another embodiment of the invention which may be employed to operate the submersible more economically. While at the surface, fresh air may be supplied to the operator and any other occupant via air delivered aboard through a system of snorkels, servo-operated ports, and fans. Such air may be rebreathed while submerged for limited amounts of time. 
         [0056]    Referring to  FIG. 2   b , the forward snorkel riser  59  is shown on the left, and the view of this riser depicts its internal elements for the purposes of illustration. The rear snorkel riser  59  (on the right) is comprised of the same internal elements, but none of these elements are made visible, as would ordinarily be apparent. Referring now to  FIGS. 1 ,  2   a , and  2   b , in a preferred embodiment, air enters the submersible through the intake snorkel  2  and descends past the intake valve  81 , through the forward riser  59  and then sucked through an intake fan, where it then circulates throughout the pressure section. Air is exhausted by an exhaust fan which pumps air out the rear riser  59 , past the exhaust valve  81  and out of the exhaust snorkel  3 . Valve actuators  84  move the valve rods  83  up and down to open and close the valves to either permit air circulation or to make the pressure section watertight for submersion. Valve guides  82  maintain proper alignment of the valves  81 . Ball float-valves  9 , held in place by cages  10 , seal the snorkels when the snorkels submerge due to waves or other phenomena which may otherwise flood the submersible when the snorkels are exposed to water with the valves  81  open.  FIG. 6  depicts spray drains  41  which have low spots with outlets below the snorkel valve seats such that a portion of any water that may enter the snorkels does not enter the risers  59 .  FIG. 13  depicts snorkel drains  109  which transport any moisture which may descend down the risers  59  to the subfloor  110 . Water which may for any reason accumulate in the subfloor  110  is pumped overboard by the bilge pump  108 . In some embodiments, the snorkels are located in different parts of the vessel, such as behind the rear canopy, and in some embodiments, the snorkels extend and retract, as optimal for surface and diving operations. 
         [0057]    During diving operations, oxygen and carbon dioxide monitors may determine when the submersible&#39;s atmosphere is about to be unsuitable for human respiration at which time the operator may maneuver the vehicle to the surface to expel consumed air and re-introduce fresh air. Venting of the ambient atmosphere may negate the need and expense of employing carbon dioxide scrubbers and a supply of oxygen, which may minimize costs. In some embodiments, carbon dioxide scrubbers and supplemental compressed air, oxygen, or other gasses may be carried inside the submersible for extended underwater operations at incremental escalations of complexity and cost commensurate with increased depth and bottom time. 
         [0058]    In yet other embodiments, the submersible operator may sit at ambient pressure equal to that of its water depth; however, in some embodiments, the submersible&#39;s hull may contain some differential level of pressure such that the operator is exposed to an intermediary level of pressure between ambient pressure and one standard atmosphere. 
         [0059]    The invention&#39;s construction may be optimized for higher-speed, low power consumption through a liquid medium. In an embodiment, the submersible&#39;s composite hull may be comprised of fiber-reinforced, plastic laminate material. In some embodiments, a fiber-reinforced plastic hull may act as a fairing to house an internal pressurized shell composed of steel. Nothing in this disclosure should be construed to limit the scope of materials selected for the composite hull nor the steel shell. For instance it is perfectly acceptable to the designs described herein that the shell may be comprised primarily of aluminum or any other metal or alloy. Alternatively, the shell could be comprised primarily of carbon fiber, fiberglass, or any other composite material. Likewise, the hull may be comprised of plastic or any material of appropriate structural fortitude that may be shaped to meet the hydrodynamic requirements of the design. Those practiced in the art may envision other materials suitable to the hull or shell in accordance with the present invention. 
         [0060]    In a preferred embodiment, the submersible is designed and constructed to keep water outside of the steel shell although water is permitted to travel in and out of the space between the composite hull and the steel shell. It is understood by those talented in the art as an aspect of the preferred embodiment that water can be pumped in and out of this volume of space to vary the vessel&#39;s freeboard. In some embodiments, the vessel freeboard is lengthened by the use of an expansion joint sealed to the entry hatch such that when the canopy is opened, the expansion joint is extended. It can be seen then that the extended expansion joint resembles in form and function a submersible&#39;s conning tower, thereby extending the vessel&#39;s freeboard. 
         [0061]    The ballast snorkel  8  in  FIG. 1  offers a supply of air to facilitate the draining of water ballast when the submersible&#39;s body is near the surface yet still underwater. The ballast snorkel also serves as a ballast vent such that differential pressure cannot build across the composite hull.  FIG. 10  depicts the ballast pump fill/drain port  52 , from where water ballast enters and exits the submersible. The drain plug  51  permits complete draining of the submersible&#39;s water ballast and must be installed to allow the water ballast volumes to remain empty when the submersible is in the water. 
         [0062]    In some embodiments, the composite hull may itself act as a pressure vessel such that the submersible is not comprised of a steel shell. Other configurations are also envisioned. For example, the composite hull construction may alternatively include, but not be limited to an all metal hull with no core, or a very thin metal hull encasing a core material. Any of the plasticized materials could be used as a hull material sandwiched around a wide variety of wood, foam, honeycomb of paper or metal or other honeycomb material, or any other material core intended for structural applications. 
         [0063]    In some embodiments, the steel shell and bulkheads may be replaced by or be reinforced by internal stringers and stations (open bulkheads also known as formers or frames). In regard to the internal supporting structure, any stiff material of reasonable modular strength could be used, including but not limited to a variety of metals or composite material such as carbon-epoxy laminate or high-strength aluminum. 
         [0064]    In another preferred embodiment, the pitch planes  12 , yaw planes  4 , and dive planes  11  may be constructed of structural foam core encased in fiberglass with pultruded carbon-fiber spars. Because of axial forces carried by these planar control surfaces, a fiberglass plate may be cured lengthwise to each spar to distribute these torsional loads throughout the foam core. In some embodiments, the spar may be comprised of steel or other metal, and axial forces within the plane may be carried by a steel or similarly stiff material plate welded or otherwise fastened to a metal spar. 
         [0065]    In some embodiments, the Plexiglas canopy  1  in  FIG. 1  allows external viewing, however the use of Lexan or any other see-through material capable of withstanding the required differential and dynamic pressure of underwater travel may be possible. In some embodiments, one or more of the canopies do not open but remain fixed, and entry and exit is via one or more hatches distinct from the canopies. 
         [0066]    It will be apparent to anyone knowledgeable in the art that the disclosure herein entails a unique load transfer system. Because of large maneuvering forces that may be generated by the tail planes, rather than build a truss from the steel shell to the tail that may transmit large moments to the steel shell&#39;s rear head, portions of both the fore and aft cylindrical space between the steel shell and the composite hull are filled with a pourable epoxy that cures to a hardness similar to ethylene propylene diene monomer (EPDM). The fill cures in place so as to provide a custom cushioned support between the composite hull and the steel shell. This system permits maneuvering loads to be transmitted to the steel shell across a very large area without imparting moments on the steel shell due to tail plane forces. In one embodiment, the EPDM fill cures to the composite hull and is not permanently fastened to the steel shell to afford inspection of the steel shell&#39;s external surface. 
         [0067]    In a preferred embodiment, the composite hull is divided into three component parts. The bow hull is distinct, permitting it to remain fixed when the remainder of the vessel rotates about the tow bearing  33 . The remainder of the composite hull is split into two parts along the midline such that there is distinctly a rear starboard hull and a rear port hull. The composite hull must carry all the loads that originate at the tail planes. The tail planes mount to tail plane supports, therefore, these tail plane supports must be secured to the composite hull. For structural integrity of the tail plane supports, it may be useful to keep these tail plane supports as a single structure embedded and bonded to the tail cone in which the structure sits. Therefore, it may be of use to maintain the entire tail cone as a single structure and then to permanently bond the tail cone to one of the rear hulls. As it is useful to be able to remove the composite hulls for maintenance and inspection, there will be a seam down a portion of the submersible&#39;s midline. If the tail cone is one integral, inseparable component, this seam will separate from the submersible midline, as depicted by line  53  depicted in  FIG. 10 . 
         [0068]      FIG. 5  depicts an embodiment in which dive plane supports  37  carry dive plane loads to the steel shell. The supports may be designed to separate from the steel shell in the event of excessive dive plane loads or a collision such that the structural integrity of the steel shell is maintained. In an embodiment, the dive plane supports and the dive plane actuators are housed within the dive plane fairings  65  depicted in  FIG. 11 . 
         [0069]    In a preferred embodiment, the bearing support shaft  31  is hollow, thereby resembling a pipe in form and function. The bearing support shaft  31  permits cable and wiring, as may be required for a transducer or other electronics, to be carried to the tip of the submersible&#39;s bow. The bearing support shaft may also route an emergency release device to the bridle cable  71  such that when actuated, one end of the bridle cable is permitted to be pulled away from the submersible such that the submersible is released from the towing tether  73 . In another embodiment, the bearing support shaft  31  is thick at its length closest to the steel shell to carry the loads imparted by the tow bearing  33  and the support shaft is thinner towards the bow. It may be seen then that in the case of a head-on collision that the bearing support shaft would collapse at the bow, rather than be driven into the forward head of the steel shell. Impact energy may then be absorbed by the structure of the composite hull and may also be absorbed by destroying the adhesive bonds between the lead shot and epoxy that comprise the submersible&#39;s hard ballast in its bow. 
         [0070]    The embodiment depicted in  FIG. 13  illustrates the forward trim ballast box  101  and the aft trim ballast box  102 . Those knowledgeable in the art will realize that the submersible portrayed herein may benefit from a certain precision in balance and loading. As the weights of submersible occupants may vary, distinct internal trim ballast areas may hold some amount of hard ballast such that the submersible&#39;s total weight and CG may be adjusted as desired by its operator. Such adjustments are also useful in changing ballast requirements between salt and fresh water dive areas, or to adjust the submersible&#39;s ballast for a higher salt dive area, as may be encountered in the Red Sea. The trim ballast boxes may be designed to carry trim ballast close to the submersible&#39;s midline so as to not materially alter the submersible&#39;s longitudinal stability. 
         [0071]    In a preferred embodiment, electrical systems such as sonar, communication equipment, sensors, and lighting are powered by batteries which are housed in one or more battery boxes  103 . Those knowledgeable in the art may imagine many different systems which may be useful, desirous, or necessary for any given underwater operation. In some embodiments, electrical power will be supplemented by a turbine driven generator, the turbine being turned by the vessel&#39;s forward motion.  FIG. 15  depicts an embodiment in which various switches and controls are employed to operate the submersible and its systems described herein. Computer management of automated warnings and other operations may afford submersible operators with opportunities to better perform desired operations or to otherwise divert attention to more pleasant tasks such as outside observation. 
         [0072]    The illustrative embodiment of the towable submersible described herein comprises many systems and features that have not been specified in this detailed description of the invention but that would be well understood by one of ordinary skill in the related art as typical and expected components of the invention. It is understood that the towable submersible described herein may be comprised of the many and various safety features and other components that may be dictated by the United States Coast Guard, other governmental agencies both foreign and domestic, or nautical classification societies that audit submersible design and construction. 
         [0073]    The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described (or portions thereof), and it is recognized that various modifications are possible within the scope of the claims. Accordingly, the appended claims are intended to cover all such equivalents.