Patent Publication Number: US-6901876-B2

Title: Methods and apparatus for hull attachment for submersible vehicles

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to and is a continuation of U.S. patent application Ser. No. 10/072,642 filed Feb. 6, 2002, now U.S. Pat. No. 6,698,373, which claims priority to and is a continuation-in-part of U.S. patent application Ser. No. 09/898,777, filed Jul. 3, 2001, and issued as U.S. Pat. No. 6,474,255 on Nov. 5, 2002, which claims priority to and is a continuation of U.S. patent application Ser. No. 09/357,537, filed Jul. 19, 1999, and issued as U.S. Pat. No. 6,276,294 on Aug. 21, 2001. Each of the above-referenced applications is incorporated by reference in its entirety as if set forth fully herein. 

   TECHNICAL FIELD 
   The present invention relates to submersible vehicles, or more particularly, to methods and apparatus for hull attachment for submersible vehicles having improved adjustability, maintainability, integrity, reliability, and overall improved mission performance. 
   BACKGROUND OF THE INVENTION 
   Submersible vehicles are presently used for a wide variety of underwater operations, including inspection of telephone lines and pipe lines, exploration for natural resources, performance of bio-mass surveys of marine life, inspection of hulls of surface vessels or other underwater structures, and to search for shipwrecks and sunken relics. Submersible vehicles may be manned or unmanned, and may carry a wide variety of payloads. Furthermore, submersible vehicles may be towed by a surface vessel, or may be equipped with a propulsion unit for autonomous mobility. Overall, submersible vehicles are an important tool in the performance of a wide variety of hydrographic surveys for commercial, ecological, professional, or recreational purposes. 
     FIG. 1  shows a towed submersible vehicle  10  and related support equipment in accordance with the prior art. In this embodiment, the submersible vehicle  10  includes a hull  12  having a streamlined cylindrical body  13 . Several fins  14  project radially from the hull  12  as fixed control surfaces. The front (or bow) of the body  13  includes an open aperture  16  covered by a transparent window  18 . The body  13  has a substantially enclosed back (or stern)  20  and a tail section  22  which is attached to the back  20  and which has a vertical steering flap  24  and a horizontal steering flap  26 . The vertical and horizontal steering flaps  24 ,  26  are actuated by a pair of actuators (not shown) which are disposed within a payload area  21  inside the body  13 . Actuator arms  28  extend through the back  20  of the hull  12  to actuate the vertical and horizontal steering flaps  24 ,  26 . 
   The hull  12  also includes a tow point  30  located on an upper portion of the body  13  for attaching the submersible vehicle  10  to a tether or tow cable of a surface vessel. A pair of runners  32  are attached to the lower fins  14  to protect the vehicle from striking rocks or other objects on the ocean floor. 
   Support equipment for the submersible vehicle  10  includes a control unit  34 , which is connected to the submersible vehicle  10  by an umbilical  36 . Power is delivered to the submersible vehicle  10  through the umbilical  36 , and control signals from the controller  34  are transmitted through the umbilical  36  to the actuators for independently actuating the vertical steering flap  24  and the horizontal steering flap  26 . In the embodiment shown in  FIG. 1 , a viewing visor  38  may be connected by the umbilical  36  to a camera located within the payload compartment  21  which transmits photographic images of the underwater scene to the viewing visor  38 . A camera control box  40  is electronically coupled to the camera by the umbilical  36 , enabling an operator on the surface vessel to adjust the photographic images as desired. 
   In operation, the submersible vehicle  10  is towed behind a surface vessel over an area of interest, such as a pipeline, potential fishing area, or potential shipwreck area. Wearing the viewing visor  38 , the operator uses the controller  34  to control the movement of the submersible vehicle by adjusting the deflections of the vertical and horizontal steering flaps  24 ,  26 . Lateral movement of the submersible vehicle  10  is controlled by deflecting the vertical steering flap  24 , causing the vehicle to turn to the right or left (i.e. “yaw”). The depth of the submersible vehicle  10  is controlled by deflecting the horizontal steering flap  26 , causing the bow of the vehicle to pitch up or down (i.e. “pitch”). In this way, the operator is able to control the flight of the submersible vehicle  10  over the areas of interest on the ocean floor to perform inspections or acquire desired information. 
   Although desirable results have been achieved using the prior art system, several characteristics of the submersible vehicle  10  leave room for improvement. For instance, when the vehicle  10  is being towed in a current, especially a current that flows across the direction of travel of the surface vessel, the submersible vehicle  10  may become unstable. Cross-currents tend to cause the submersible vehicle  10  to “roll” about a lengthwise axis so that the runners  32  may no longer remain below the vehicle for protection. The rolling of the submersible vehicle  10  may also interfere with or disable the data acquisition equipment contained within the payload section. Strong currents along the direction of travel of the surface vessel (i.e. along the freestream flow direction) may also hamper the controllability of the vehicle  10 . 
   Also, undesirable rolling characteristics are experienced when the submersible vehicle  10  is guided by the operator to a position that is laterally displaced to the sides of the surface vessel. That is, when the submersible vehicle  10  is flown out widely to the left or to the right of the surface vessel, the tether which is attached to the tow point  30  pulls on the tow point causing the vehicle to roll undesirably. 
   Furthermore, under some operating conditions, the shape and orientation of the fins  14  and the vertical and horizontal steering flaps  24 ,  26  fail to provide the desired hydrodynamic stability and controllability of the submersible vehicle  10 . In rough seas and high currents, such as those which may be experienced in the fisheries of the North Atlantic and North Pacific Oceans, and in some areas commonly associated with shipwrecks in the southeastern Pacific Ocean, prior art submersible vehicles sometimes fail to provide adequate or required stability or maneuverability characteristics, including roll, pitch, and yaw control. 
   Another drawback of prior art submersible vehicles  10  is the manner in which various exterior devices are attached to the body  13  of the hull  12 . For example,  FIG. 9  is an enlarged, partial isometric view of the hull  12  of the submersible vehicle  10  of  FIG. 1 . As shown in  FIG. 9 , one of the fins  14  is attached to the body  13  by a plurality of weld points  50 , and the tow point  30  is attached to the body  13  by additional weld points  52 . Also, a mount  54  for attaching various external equipment (e.g. lights, cameras, instrumentation, etc.) to the hull  12  includes a base member  56  that is attached to the body  13  by a plurality of weld points  51 . A threaded aperture  58  is disposed in the base member  56  to enable various external equipment to be mounted to the hull  12 . Of course, in other prior art vehicles, the number of weld points  50 ,  51 ,  52  may be greater or fewer than that shown in  FIG. 9 . 
   The prior art methods of attaching devices to the body  13  of the hull  12  by welding has several drawbacks. For example, the weld points  50 ,  51 ,  52  are susceptible to rust, particularly in a seawater environment, and may eventually become weakened. Additionally, the extremely high temperatures involved in the prior art methods of welding the fins  14  and other devices to the body  13  of the hull  12  may result in warpage or other deformities of the local area of the hull  12  proximate to the weld points  50 ,  51 ,  52 . Such deformities may undesirably degrade the accuracy with which the external equipment is positioned on the hull  12 , or may even degrade the strength and integrity of the hull  12 , particularly for hulls  12  designed to withstand extreme pressures. Yet another disadvantage of the prior art methods of attachment is that once a device (e.g. a fin  14  or a tow point  30 ) is welded to the body  13  of the hull  12 , it becomes difficult to remove for repairs or re-configuration of the vehicle  10 . 
   SUMMARY OF THE INVENTION 
   The present invention relates to improved methods and apparatus for hull attachment for submersible apparatus. The inventive attachment apparatus provide improved adjustability, maintainability, integrity, reliability, and overall improved mission performance of submersible apparatus, particularly submersible vehicles. In one embodiment, a submersible apparatus in accordance with the invention includes a hull having an elongated channel. A sliding member is at least partially disposed within the channel and moveable along at least a portion of the channel. A mounting assembly is attached to the sliding member and includes an engagement member coupled to the sliding member, the engagement member being selectively engageable between a first position wherein the mounting assembly is moveable along the channel, and a second position wherein the mounting assembly is secured in a fixed position along the channel. The apparatus advantageously permits a wide variety of equipment or devices (e.g. tow point assemblies, wing assemblies, tail assemblies, propulsion units, illumination devices, imaging devices, instrumentation, sensors, etc.) to be adjustably attached to the hull. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a towed submersible vehicle and related support equipment in accordance with the prior art. 
       FIG. 2  is a front elevational view of an arcuate-winged submersible vehicle in accordance with an embodiment of the invention. 
       FIG. 3  is a top elevational view of the arcuate-winged submersible vehicle of  FIG. 2 . 
       FIG. 4  is a side elevational view of the arcuate-winged submersible vehicle of  FIG. 2 . 
       FIG. 5  is a partial cross-sectional view of the arcuate-winged submersible vehicle taken along line  5 — 5  of  FIG. 3 . 
       FIG. 6  is a bottom elevational view of the arcuate-winged submersible vehicle of  FIG. 2 . 
       FIG. 7  is an isometric view of the arcuate-winged submersible vehicle of  FIG. 2  being towed by a surface vessel. 
       FIG. 8  is an isometric view of an alternate embodiment of an arcuate-winged submersible vehicle in accordance with the invention. 
       FIG. 9  is an enlarged, partial isometric view of the hull of the prior art submersible vehicle of  FIG. 1 . 
       FIG. 10  is an isometric view of a submersible vehicle in accordance with another embodiment of the invention. 
       FIG. 11  is an enlarged isometric view of the body portion of the hull of the submersible vehicle of  FIG. 10 . 
       FIG. 12  is an enlarged, partial front elevational view of the submersible vehicle of  FIG. 10 . 
       FIG. 13  is an enlarged, partial front elevational view of the tow point attachment assembly of  FIG. 12 . 
       FIG. 14  is an enlarged isometric view of a rail nut of the tow point assembly of  FIG. 13 . 
       FIG. 15  is an enlarged, partial isometric exploded view of a wing attachment assembly of the submersible vehicle of  FIG. 10 . 
       FIG. 16  is an enlarged, partial front elevational view of a tow point attachment assembly in accordance with an alternate embodiment of the invention. 
       FIG. 17  is an isometric view of a submersible vehicle in accordance with yet another embodiment of the invention. 
       FIG. 18  is an enlarged, partial isometric exploded view of a wing attachment assembly and an equipment attachment assembly of a submersible vehicle in accordance with another alternate embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention relates to arcuate-winged submersible vehicles for use in, for example, underwater payload delivery and data acquisition, including hydrographic surveys for commercial, ecological, professional, or recreational purposes. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 2–8  and  10 – 18  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description. 
     FIG. 2  shows a front elevational view of an arcuate-winged submersible vehicle  100  in accordance with the present invention. In this embodiment, the vehicle  100  has a hull  12  that includes a cylindrical body  13  and a pair of arcuate (or “gull-shaped”) wings  114  projecting outwardly from the body  13  at an angle A with the vertical (see  FIG. 2 ). The arcuate wings  114  may typically attach to the body over a range of angles from about 30 to about 70 degrees, with a value of A of approximately 50 degrees being preferred. Each arcuate wing  114  has a partially curved or arcuate shape with a lateral radius of curvature R 1  that varies from the wing root  122  to the wing tip  120 . In this embodiment, the lateral radius of curvature R 1  of the arcuate wings  114  increases with increasing distance from the body  13  and is greater near the leading edges  116  or bow of the vehicle  100  and less along the trailing edges  118  of the wings. A pair of straight planar fins  14  project downwardly and radially outward from the body  13 . The body  13  has an aperture  16  at the bow covered by a transparent window  18  (see  FIG. 3 ), a watertight, enclosed back  20 , and an interior payload compartment  21 . The hull  12  also has a tow point  30  attached along a top portion of the body  13 . A light fixture  128  is attached to a lower surface of each wing  114 . 
     FIG. 3  is a top elevational view (or “planform” view) of the arcuate-winged submersible vehicle  100  showing additional features of the arcuate wings  114 . In this embodiment, each arcuate wing  114  has a leading edge  116  that is swept in a rearward direction. In other words, the leading edges  116  do not project from the body  13  in a perpendicular direction, but rather, are angled toward the rear of the vehicle at an angle B which varies with distance from the body  13 . The light fixture  128  projects slightly ahead of the leading edge  116  of each arcuate wing  114 . 
   As further shown in  FIG. 3 , each arcuate wing  114  also has a trailing edge  118  that is swept in a forward direction at an angle C which also varies with distance from the body  13 . The leading and trailing edges  116 ,  118  of the arcuate wings  114  join together at a smoothly curved wing tip  120 . Each arcuate wing  114  also has a wing root  122  attached to the body  13 . The trailing edge  118  of each arcuate wing  114  is further shaped to define a cutout area  124 , and a wing steering flap  126  is hingeably attached to each arcuate wing  114  and received within the cutout area  124 . Each wing steering flap  126  is adjustably deflectable over a range of positions from a full-up position to a full-down position. 
   In the embodiment shown in  FIG. 3 , the angle B of the swept leading edge  116  averages about 32 degrees along an inner section near the body, decreases to an average of about 27 degrees along a middle section of the leading edge  116 , increases again to an average of about 45 degrees along an outer section, and then continues to increase to 90 degrees at the wing tip  120  to smoothly join with the trailing edge  118 . Similarly, the angle C of the swept trailing edge  118  varies from an average of about zero degrees along an inner section near the body, increases to an average of about 47 degrees along a middle section of the trailing edge  118 , and then continues to increase to 90 degrees at the wing tip  120 . It should be understood, however, that the variation of the angles B and C of the leading and trailing edges  116 ,  118  respectively, may be varied from the particular embodiment shown to any number of possible configurations depending upon the intended maneuverability characteristics or the desired appearance of the vehicle, including, for example, holding angles B and C constant. 
     FIG. 4  is a side elevational view of the arcuate-winged submersible vehicle  100 , and  FIG. 5  is a partial cross-sectional view of the vehicle  100  taken along line  5 — 5  of  FIG. 3 . As shown in  FIG. 5 , the arcuate wings  114  has a cross-sectional shape  115  that has a longitudinal radius of curvature R 2 . In this embodiment, the longitudinal radius of curvature R 2  is approximately infinite near the leading edge  116  and the trailing edge  118  of the cross-sectional shape  115  (i.e. the wing is substantially planar near the leading and trailing edges  116 ,  118 ). Along an intermediate portion, the cross-sectional shape  115  has a positive longitudinal radius of curvature R 2 , followed by a negative longitudinal radius of curvature R 2  and the cross-sectional shape  115  becomes planar near the trailing edge  118 . 
   Because the arcuate-winged vehicle  100  has an approximately planar portion (i.e. approximately infinite lateral and longitudinal radii of curvature R 1 , R 2 ) in the vicinity of the cutout areas  124  of the trailing edges  118 , the wing steering flaps  126  are substantially planar. This configuration preferably enables the wing steering flaps  126  to be hingeably attached to the arcuate wings  114  in a conventional straight-hinge fashion to reduce turbulence and cavitation for improved wing steering flap performance. 
   Alternately, the lateral radius of curvature R 1  in the vicinity of the cutout areas  124  may be finite (i.e. curved), and the wing steering flaps  126  may be contoured to the shape of the arcuate wings  114  and joined to the wings in a less conventional manner. This may be accomplished, for example, by dividing each wing steering flap  126  into multiple segments (not shown) with each segment being individually hingeably attached to the arcuate wing  114 . 
   Numerous other features of the arcuate wings  114  may be varied from their particular configuration shown in  FIGS. 2 through 5 . As mentioned above, the variation of the angles B and C of the leading and trailing edges  116 ,  118  respectively, may be varied from the particular embodiment shown. Alternately, the leading edges  116  may be forwardly swept, or the trailing edges  118  may be rearwardly swept, or the leading and trailing edges  116 ,  118  may project perpendicularly from the body  13 . Furthermore, the lateral and longitudinal radii of curvature R 1 , R 2  of the arcuate wings  114  may be varied from the curvatures shown in the accompanying figures, including, for example, holding these parameters constant. 
     FIG. 6  is a bottom elevational view of the arcuate-winged submersible vehicle  100  showing a wing flap actuator  130  attached to the lower surface of each arcuate wing  114 . An actuator arm  132  extends from each actuator  130  to each wing steering flap  126  for actuating the wing steering flap  126  between the full-up and full-down positions, thereby providing depth control of the vehicle. The actuators  130  may be of any conventional type, including hydraulic or electrically-driven actuators, such as the Digit linear actuator available from Ultra Motion of Mattituck, N.Y. 
   The hull  12  also includes a tail assembly  134  having a rigid support  135  extending from the back  20  of the body  13 . A vertical tail steering flap  136  is hingedly attached to the rigid support  135  and is hingeably and adjustably deflectable over a range of positions from a full-left position to a full-right position. As best seen in the side elevational view of the vehicle  100  shown in  FIG. 4 , a tail flap actuator  138  is attached to the rigid support  135 . A control arm  140  attaches the tail flap actuator  138  to the tail steering flap  136  for actuating the tail steering flap  136  between the full-left and full-right positions, thereby providing lateral or yaw control of the vehicle. 
   One may note that a wide variety of control surface configurations may be utilized to control the vehicle  100 . The wing steering flaps  126 , for example, may be joined by an appropriate linkage to operate in unison so that only one wing flap actuator is needed to actuate both wing flaps to provide pitch control, although some controllability of the vehicle (e.g. roll control) may be sacrificed. Also, the wing flaps need not be disposed within cutout areas  124 , and may be repositioned anywhere along the trailing edges of the wings. The wing flaps may even be eliminated and replaced by one or more control surfaces located elsewhere on the vehicle, including those which project from the tail assembly  134  (e.g. “elevators”), or from the body  13  (e.g. “canards”), or from other portions of the hull  12 . 
   Similarly, the vertical tail steering flap  136  may be repositioned on the hull of the vehicle, or may be eliminated and replaced with suitable control surfaces that provide the desired lateral (or “yaw”) directional control, including pairs of vertical control surfaces mounted on the wings or elsewhere on the vehicle. Furthermore, the vehicle may be controlled by replacing the wing flaps and the tail flap with a “V-tail” having two deflectable control surfaces that provide the desired pitch, yaw, and roll control. A non-exhaustive collection of possible control surface configurations suitable for use with arcuate-winged vehicles is presented by Professor K. D. Wood&#39;s “Aerospace Vehicle Design, Volume I,” Second Edition, at pages 1–9:22 through 1–9:23, published by Johnson Publishing Company of Boulder, Colo., incorporated herein by reference. 
     FIG. 7  is an isometric view of the arcuate-winged submersible vehicle  100  being towed behind a surface vessel  152  using a tether  150 . As the vehicle  100  is towed through a fluid medium, the arcuate wings  114  enhance the stability and controllability of the vehicle&#39;s movement through the medium. An operator or controller (not shown) on the surface vessel  152  may control the flight of the vehicle  100  by transmitting control signals from a control unit to the wing and tail flap actuators  130 ,  138 . The control signals may be electrically transmitted from the control unit via an umbilical ( FIG. 1 ), or by an RF signal sent by a transmitting antenna, or even by acoustic signals. The operator transmits appropriate control signals to the wing flap and tail flap actuators  130 ,  136  to deflect the wing steering flaps  126  and tail steering flap  136 , thereby controlling the depth and lateral position of the vehicle with respect to the direction of travel of the surface vessel. In this manner, the operator pilots the arcuate-winged submersible vehicle  100  over a desired flight path. 
   The operator may receive visual images or other feedback signals from a camera or other navigational equipment (e.g. inclinometer, depth gauge, sonar, etc.) on board the vehicle to assist in operating the vehicle. In addition, a computer, microcomputer, or other programmable device may be located on-board the vehicle, such as within the payload compartment, to monitor input signals from the controller or from the navigational sensors and to transmit appropriate feedback signals to the controller on the surface vessel  152 , or control signals to the actuators  130 ,  138  to control wing steering flap deflections and tail steering flap deflections, respectively. The on-board computer or control system might therefore be used, for example, as a safety system to prevent the vehicle from exceeding a maximum depth, to maintain the attitude of the vehicle, or to prevent collisions with submerged structures. 
   The arcuate-winged submersible vehicle  100  provides markedly improved stability and maneuverability over prior art submersible vehicles having straight wings or simple fins. The arcuate-shaped wings  114  increase the operator&#39;s control over the vehicle, improving the ability to fly the vehicle along a desired path over the floor of the ocean, especially when the vehicle is guided a great distance to the left or right of the surface vessel  152 . Undesirable rolling characteristics exhibited by prior art vehicles are substantially reduced or eliminated. Similarly, the stability and maneuverability of the arcuate-winged vehicle in a strong cross-current is favorably improved over the characteristics of prior art submersible vehicles. 
   The improved hydrodynamic maneuverability and stability of the submersible arcuate-winged vehicle  100  provides superior payload delivery and data acquisition characteristics over prior art submersible vehicles. Because the vehicle is more stable, data acquired from a variety of payload devices (cameras, sonar, microphones, etc.) are of better quality than obtained using prior art submersible vehicles. Therefore, the arcuate-winged submersible vehicle  100  provides improved hydrographic survey data for such applications as marine bio-mass surveys in fisheries, ecological surveys, underwater mapping surveys or mineral exploration or searching for shipwrecks, and many other applications. 
   As described above, the shape of the arcuate-winged vehicle  100  may differ from that shown in the figures. Tests suggest, however, that the shape having the swept leading and trailing edges  114 ,  116  as shown in the accompanying figures provides desirable vehicle stability and maneuverability characteristics. In particular, for a wingspan w defined as the distance from wing tip to wing tip of the arcuate wings  114  (see  FIG. 6 ), and a distance L is defined as the maximum distance from the leading edge to the trailing edge of the arcuate wings  114 , optimum characteristics have been achieved where the ratio w/L is approximately equal to 3/2. 
   It should also be understood that the arcuate wings  114  may project from the hull  12  from any number of positions about the circumference of the body  13 . For example, the arcuate wings may attach to the body  13  at higher or lower positions than those shown in  FIG. 2 . Desirable results have been achieved, however, with the configuration shown in  FIG. 2  where the curvature of the arcuate wings  114  is such that the wing tips  120  are at approximately the same “water line” (i.e., same vertical level) as the attachment point between the wing root  122  and the body  13 . 
     FIG. 8  shows an arcuate-winged submersible vehicle  200  in accordance with an alternate embodiment of the invention. In this embodiment, the arcuate-winged submersible vehicle  200  includes a propulsion unit  260  attached to each fin  14 . The propulsion units  260  are of any conventional type, including electrical or hydraulic units, and advantageously enable the vehicle  200  to be propelled along a desired path without being towed by a surface vessel. As the vehicle  200  propels itself through the fluid medium, the arcuate wings enhance the stability and controllability of the vehicle&#39;s movement through the medium. The desired stability and maneuverability characteristics are thereby achieved in an autonomously powered vehicle  200 . Although the arcuate-winged vehicle  200  may remain tethered to a surface vessel for purposes of recovery or launch of the vehicle  200 , or for transmittal of control signals to the control actuators, the vehicle  200  is otherwise free to maneuver independently from the surface vessel. 
   The arcuate-winged vehicle  200  further includes a hingable tow point assembly  270 . The tow point assembly  270  has a tow plate  272  coupled to the body  13  of the hull  12  by a hinge  274 . The tow plate  272  includes an arcuate slot  274  disposed therethrough and positioned proximate to an arcuate leading edge  276  of the tow plate  272 . The arcuate slot  274  is sized to receive a shackle (not shown) of a tow cable or tether for launch or recovery of the vehicle. The tow point assembly  270  is especially useful, however, on towed vehicle configurations such as the vehicle  100  shown in  FIGS. 2 through 7 . 
   In operation, the tow plate  272  of the hingable tow point assembly  270  is pivotably movable with respect to the body  13  about the hinge  274 . The tow plate  272  adjustably pivots over a range of positions from a full left position contacting one arcuate wing  114  to a full right position contacting the other arcuate wing  114 . Therefore, as an operator controls the tail steering flap deflection to guide the vehicle laterally to the side of the surface vessel, the tow plate  272  pivots about the hinge  274 , and undesirable rolling of the vehicle  200  caused by the tow cable is reduced or eliminated. Similarly, as the operator adjusts the wing steering flap deflection to cause the vehicle to dive to greater depths, the shackle of the tow cable slides within the arcuate slot  274 . In this way, undesirable nose up or nose down pitching of the vehicle caused by the tow cable is reduced or eliminated. 
   Several features of the tow point assembly  270  may be varied from the embodiment shown in  FIG. 8 . The size and shape of the tow plate  272 , for example, may be modified to a wide variety of suitable sizes and shapes. Similarly, the length and shape of the arcuate slot  274  may be varied as desired, including quarter-circular, semi-circular, elliptic, and parabolic shapes. The most suitable geometry of the tow point assembly for a particular submersible vehicle may depend on a number of factors, including the anticipated flight path of the vehicle. Although the tow point assembly  270  is shown in  FIG. 8  on an arcuate-winged vehicle  200 , it is also suitable for use with a wide variety of towed or autonomously powered conventional submersible vehicles that do not have arcuate wings. 
     FIG. 10  is an isometric view of a submersible vehicle  300  in accordance with another embodiment of the invention. In this embodiment, the vehicle  300  includes a hull  312  having a body  313  with a plurality of longitudinal channels  315  disposed therein. As best shown in  FIG. 11 , the plurality of channels  315  are disposed within the outer surface of the body  313  at a plurality of circumferential positions, and in this embodiment, extend longitudinally along the entire length of the body  313 . The channels  315  may be formed in the body  313  in any conventional manner, including machining or casting. 
   Referring again to  FIG. 10 , a pair of arcuate wings  314  are attached to the body  313  by a plurality of wing attachment assemblies  320 . Similarly, a tail assembly  322  is attached to the body  313  by a tail attachment assembly  324 , and a tow point assembly  280  is attached to the body  313  by a tow point attachment assembly  281 . 
     FIG. 12  is an enlarged, partial front elevational view of the submersible vehicle  300  of  FIG. 10 . As shown in  FIG. 12 , in this embodiment, each arcuate wing  314  is attached to the body  313  by wing attachment assemblies  320  along two of the longitudinal channels  315 . Similarly, the tow point assembly  280  and the tail assembly  322  ( FIG. 10 ) are attached to the body  313  along a single longitudinal channel  315  extending along the top of the body  313  by respective tow point and tail attachment assemblies  281 ,  324 . As described more fully below, the wing, tail, and tow point attachment assemblies  320 ,  322 ,  281  are adjustably positionable along their corresponding longitudinal channels  315 . 
     FIG. 13  is an enlarged, partial front elevational view of the tow point attachment assembly  281  of  FIG. 12 . In this embodiment, the tow point attachment assembly  281  includes a base  282  having a threaded member  284  disposed therethrough. A rail nut  286  is slideably positioned within the channel  315  and includes an engagement hole  287  threadedly engaged with the threaded member  284 . As shown in  FIG. 14 , in this embodiment, the rail nut  286  has three threaded engagement holes  287  disposed therein, allowing for up to three threaded members  284  to be used. As the threaded member  284  is tightened, engagement surfaces  288  on the rail nut  286  are brought into engagement with opposing locking surfaces  316  of the channel  315  to secure the rail nut  286 , and thus the tow point attachment assembly  281 , in position in the channel  315 . 
   The tow point attachment assembly  281  advantageously permits the tow point assembly  280  to be moved axially along the length of the submersible vehicle  300  by simply loosening the one or more threaded members  284 , sliding the rail nut  286  axially along the channel  315 , and re-tightening the threaded members  284 . Thus, the tow point assembly  280  may be easily re-positioned to account for variations in the center of gravity of the submersible vehicle  300 . For example, if various external equipment (e.g. lights, cameras, instrumentation, etc.) are attached to or removed from the hull  312 , the position of the tow point assembly  280  may be adjusted along the channel  315  to maintain the desired pitch and trim characteristics of the vehicle  300 . Because the axial position of the tow point attachment assembly  281  is adjustable by simply loosening and tightening one or more threaded members, the position of the tow point assembly  280  may be adjusted more easily and quickly than prior art assemblies, especially those that rely on weldments or other methods of fixing the assembly to the hull. 
   Another advantage of the inventive attachment assembly  281  is that, in the event repairs are needed, the tow point assembly  280  may be easily detached and replaced with spare parts. This advantageously improves the maintainability of the vehicle, and also reduces or eliminates down time of the vehicle  300 . 
   Yet another advantage of the inventive attachment assembly  281  is that welds  52  ( FIG. 9 ) to the surface of the body of the hull may be eliminated. Because welds  52  may be susceptible to rust and may become weakened, the inventive attachment assembly  281  may exhibit longer life and greater reliability than prior art methods that rely on weldments. Also, by eliminating the extremely high temperatures associated with welding, certain undesirable side effects of the welding process (e.g. warpage or other deformities of the hull) may be eliminated that further improve the strength, structural integrity, reliability, and useable life of the vehicle. Furthermore, the inventive attachment assemblies may provide improved control and accuracy of the position of the attached device, such as the tow point assembly  280 . 
   Similarly, the tail attachment assembly  324  may be constructed in the same manner as the tow point attachment assembly  281  shown in  FIGS. 12–14 . Thus, the above-noted advantages of improved adjustability, maintainability, integrity, and overall performance may also be realized using the inventive attachment scheme for the tail assembly  322 . Furthermore, the tail assembly  322  may be moved fore and aft on the body  313  as necessary to modify the characteristics of the vehicle, including, for example, the location of the center of gravity, or the moment arm of the tail flap  336 . To provide the desired strength and rigidity, in a preferred embodiment, the tail assembly  322  is mounted to the body  313  by a pair of tail attachment assemblies  324  (only one visible in  FIG. 10 ) attached to the opposing uppermost and lowermost channels  315  of the body  313 . 
   It may be noted that the inventive attachment assemblies  281 ,  324  may be used to attach virtually any external device to the body  313 , including, for example, the fins  317 , or cameras, lights, instrumentation, or any other equipment. Furthermore, the inventive attachment assemblies are not limited to use with arcuate winged submersible vehicles, but rather, may be employed on all manner of existing submersible vehicles (e.g.  FIG. 1 ), surface vessels, or on any type of apparatus wherein the above-noted advantages of improved position adjustability, maintainability, and integrity may be desired, including submersible tanks, sealable vessels, boat hulls, or other suitable apparatus. 
     FIG. 15  is an enlarged, partial isometric exploded view of the wing attachment assemblies  320  of the submersible vehicle  300  of  FIG. 10 . As shown in  FIG. 15 , in this embodiment, the wing  314  is attached to the body  313  of the hull  312  by a plurality (in this case six) wing attachment assemblies  320 . Each wing attachment assembly  320  includes a plurality of holes  322  extending through the base of the wing  314  that are aligned with corresponding threaded engagement holes  287  in corresponding rail nuts  286  (only two visible in  FIG. 15 ) disposed in channels  315  of the body  313 . Although the two rail nuts  286  shown in  FIG. 15  are shown for illustrative purposes as extending beyond the end of the body  313 , and as discussed above, they may be positioned anywhere along the length of their respective channels  315 . A threaded member  284  ( FIG. 13 ) extends through each hole  322  and is threadedly engaged with the corresponding engagement hole  287 , thereby securing the wing  314  to the body  313 . 
   The inventive wing attachment assemblies  320  provide the above-noted advantages of improved adjustability, maintainability, integrity, and overall performance for attachment of the wings  314  to the body  313 . Also, the inventive attachment assembly enables the wings  314  to be moved fore and aft on the body  313  (denoted by arrow  325  in  FIG. 15 ) as necessary to modify the hydrodynamic characteristics of the vehicle, including, for example, the location of the center of gravity, the location of the center of lift of the wings, or the moment arm of the wing flaps. 
   It should be noted that the many of the particular characteristics of the inventive attachment assemblies shown in  FIGS. 10–15  may be varied from the embodiments depicted therein. For example, the particular cross-sectional shapes of the channels  315  and the rail nuts  286  may be changed to any shape that provides suitable surfaces that engage and secure the position of the corresponding attachment assembly, including rectangular, partial-circular, or other suitable shapes. Similarly, the size of the rail nut  286  may be increased or decreased as desired, or the plurality of rail nuts may be replaced by a single, elongated rail nut. 
   For example,  FIG. 16  shows an enlarged, partial front elevational view of a tow point attachment assembly  380  in accordance with an alternate embodiment of the invention. In this embodiment, the tow point assembly  380  includes an attachment assembly  381  that includes a base  382  having a threaded member  384  disposed therethrough. A channel  385  is formed on a body  393  by a pair of angle members  386  that are secured to the body  393  by any suitable method. In the embodiment shown in  FIG. 16 , the angle members  386  are secured by welds  388  to the body  393 . A sliding member  390  is slideably positioned within the channel  385 , and is threadedly engaged with the threaded member  384 . As the threaded member  384  is tightened, engagement surfaces  392  on the sliding member  390  frictionally engage with locking surfaces  394  on the angle members  386 , securing the attachment assembly  381  in position. In alternate embodiments, the wings, tail assembly, or any other external devices may be attached to the. 
   The attachment assembly  381  shown in  FIG. 16  may advantageously provide the above-noted advantages of improved positionability and improved repairability of the tow point assembly through minor modification of the body of the hull. For example, for existing submersible vehicles wherein it may be impractical to replace the existing hull with a hull having channels integrally formed therein (e.g. by machining or casting), some of the beneficial characteristics of the inventive attachment assemblies may be achieved by attaching external members onto the existing hull to form a channel for a sliding member. Clearly, this method of attachment is not limited to the tow point assembly  380  shown in  FIG. 16 , and may be readily extended to the attachment of the wings, tail assembly, fins, or any other external devices (e.g. lights, cameras, instrumentation, etc.). 
     FIG. 17  is an isometric view of a submersible vehicle  400  in accordance with yet another embodiment of the invention. In this embodiment, the vehicle  400  includes a hull  412  having a body  313  with a plurality of channels  315 , and a forward payload assembly  440 . A pair of propulsion units  260  are attached to the body  313  by corresponding attachment assemblies of the type described above (with reference to the assemblies  281 ,  320 ,  324 , and  381 ). The forward payload assembly  440  includes a plurality of support members  442  that project forward of the body  313  and are slideably attached to the channels  315  at various circumferential stations of the body  313 . To improve clarity, only three support members  442  are shown in  FIG. 17 . In a preferred embodiment, support members  442  are symmetrically attached around the entire circumference of the body  313  to provide improved balance and hydrodynamic characteristics. 
   Each support member  442  is attached to the body  313  by an attachment assembly that includes a threaded member  284  ( FIG. 13 ) engaged through a hole disposed though the support member  442 , and extending into a sliding member  286  ( FIG. 15 ) that is slideably engaged within a channel  315  of the body  313 . The sliding members  286  may project out of the channel  315  beyond the front of the body  313 , as depicted in  FIG. 15 . The forward payload assembly  440  may be equipped with any desired instrumentation or payload, including, for example, an illumination device  444 , an imaging device  446  (e.g. camera, video, sonar, or radar apparatus), a microphone, or other desired monitors, sensors, and equipment. 
   As shown in  FIG. 17 , the body  313  that includes channels  315  (or channels  385  shown in  FIG. 16 ) advantageously permits the submersible vehicle  400  to be easily and economically retrofitted with the forward payload assembly  440 . Because the supports  442  may be easily installed or removed from the body  313 , the submersible vehicle may be quickly modified to accomplish a variety of missions. For example, the submersible vehicle may be equipped with the forward payload assembly  440  to include sidewardly-viewing instrumentation for inspecting ship hulls, piers, bridge supports, etc., or may be rapidly modified to include downwardly-viewing instrumentation for inspecting the ocean floor, pipelines, communication lines, etc. Alternately, the forward payload assembly  440  may be easily removed to return the submersible vehicle to a substantially forward-looking configuration. Thus, the vehicle having a body with channels further improves the flexibility, versatility, usefulness, and overall mission performance of the submersible vehicle. 
   It should be noted that the inventive attachment methods may be employed with circumferential channels, or with channels extending in any other direction on the body of the hull. For example,  FIG. 18  is an enlarged, partial isometric exploded view of a wing attachment assembly  520  and an equipment attachment assembly  580  of a submersible vehicle  500  in accordance with another alternate embodiment of the invention. In this embodiment, the vehicle  500  includes a body  513  having a plurality of circumferential channels  515 . In  FIG. 18 , the channels  515  extend partially around the circumference of the body  513 . Alternately, the channels  515  may extend entirely around the body  513 . 
   In this embodiment, the wing  514  is attached to the body  513  by a plurality of wing attachment assemblies  520 . Each wing attachment assembly  520  includes a threaded member  284  disposed through a hole  522  in the wing  514  and engaged into a sliding member  586  slideably positioned in one of the channels  515 . Similarly, the equipment attachment assembly  580  includes a base  582  attached to a plurality of sliding members  586  by a corresponding threaded members  284  ( FIG. 13 ) that are engaged through holes  584 . 
   The submersible vehicle  500  having the body  513  with circumferential channels  515  advantageously improves the adjustability of the positions of the wings and various external equipment around the circumference of the body  513 . Thus, the above-noted advantages of improved adjustability, maintainability, integrity, and overall performance for attachment of the wings  514  at various circumferential positions on the body  513 . Also, the equipment attachment assembly  580  advantageously enables any type of external equipment (e.g. propulsion units  260 , illumination devices, imaging devices, instrumentation, sensors, etc.) to be adjustably positioned on the body  513 . Again, the flexibility, versatility, usefulness, and overall mission performance of the submersible vehicle is significantly enhanced. 
   Although specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein of the invention can be applied to other arcuate winged submersible vehicles, not necessarily the exemplary arcuate winged submersible vehicles described above and shown in the figures. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all submersible vehicles that operate within the broad scope of the claims. Accordingly, the invention is not limited by the foregoing disclosure, but instead its scope is to be determined by the following claims.