Abstract:
A telescoping spar structure designed to be scalable for use with very large floating platforms to relatively small floating platforms includes a platform/hull for supporting a payload; a telescoping spar attached to the platform/hull that includes several interlocking tubes extending from a shallow end to a deep end of the spar, the tubes configured to telescope in and out of adjacent tubes such that the tubes are nestable together in a stowed configuration; a buoyancy chamber attached to the spar between shallow and deep ends of the spar; and, a damping chamber attached to the spar between the buoyancy chamber and the deep end of the spar, the damping chamber including: a first compartment for entraining a volume of water, a second compartment for enclosing deployment ballast, and a release mechanism for jettisoning the deployment ballast from the second compartment after the spar structure is deployed, enabling the platform to rise to an operational height relative to the waterline.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of the co-pending U.S. Provisional Application No. 60/295,202, filed on Jun. 1, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to buoys, large floating ocean platforms, and other smaller-scale floating platforms used to support various types of instrumentation and equipment.  
           [0004]    2. Description of the Related Art  
           [0005]    A need for stable platforms at sea is well established in the oceanographic research and energy production communities. However the types of platforms and the platform design options available to these communities are limited. For example, the commercial platforms available to oceanographers are generally large spar buoys that weigh thousands of kilograms, are on the order of 20 m long, and are very difficult to deploy and recover from conventional ships. Smaller buoys are available, however the smaller buoys generally have very limited stability and mast height, thus restricting the type of scientific instrumentation that can be effectively deployed on the buoys. Prior art patents related to small scale buoys include, for example, U.S. Pat. No. 4,949,643 to Bowersett et al. that discloses an anti-tilt buoy mooring system for use in oceanographic and military applications. The &#39;643 patent demonstrates the need for stabilizing buoys and is directed to stabilizing forces from mooring lines attached at the center of buoyancy of a standard, caisson type buoy. U.S. Pat. No. 5,348,501 to Brown discloses a compact retrievable marker buoy for marking underwater locations for recreational, scientific and other purposes. U.S. Pat. No. 4,962,798 to Ferraro et al. discloses a buoy deployment system for storing and deploying compact sonobuoys from an aircraft. The &#39;798 patent illustrates the need for compact buoys capable of housing sophisticated scientific instrumentation.  
           [0006]    For large energy production platforms, e.g., oil platforms, choices are typically limited to seafloor mounted, shallow-water jack-up towers, or floating barge or large spar exploration/production platforms. In deep-water offshore locations, it becomes impractical to establish seafloor-based platforms as a means to support an exploration/production facility above the water. Floating barge type platforms, however, have difficulty operating in a variety of sea-states and currents, while simultaneously maintaining contact with subsurface oil production equipment. Alternatively, production facilities have been designed for positioning directly on the ocean floor. Many of the facility designs in this category, however, are complex and difficult to construct and maintain. Spar-type platforms are typically very large (e.g., hundreds of thousand of tons and 100&#39;s of feet high), need to be fabricated in specially designed docks, require extreme measures to tow them into place, and are very expensive to construct (many such platforms cost more than $1 billion). The use of such large and expensive spar platforms is thus confined to applications that have a very high return on investment.  
           [0007]    U.S. Pat. No. 3,572,041 to Graaf describes details of an oil rig production platform according to the prior art, including a massive spar section of unitary construction. U.S. Pat. No. 4,702,321 to Horton illustrates a spar structure comprising an elongated cylindrical caisson having a length over 200 m, the caisson being again of prefabricated unitary construction that must be towed to a work site.  
           [0008]    Other designs exist concerning stabilizing large oil platforms in ultra deep water (over 600 m deep) where conventional catenary mooring lines become impractical. U.S. Pat. No. 6,012,873 to Copple et al. discloses a buoyant spar platform with a retractable gravity base. The gravity base is tethered with pre-tensioned cables to the buoyant spar structure and is designed to minimize the platform&#39;s response to excitation loads. In this design the buoyant spar structure is also a large prefabricated unitary structure.  
           [0009]    The above-mentioned patents show a market need for stable, sea-going platforms. Further, there is a need for more compact platforms, regardless of scale, that would reduce the costs of transporting the platforms to and from a work site, and also reduce the costs of deploying and recovering the platforms at a work site.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is directed to an improved, highly stable, sea-going platform. An object of the present invention is to provide a platform that is compact in a stowed configuration for ease of transport, and that extends upon deployment to a length that increases the platform&#39;s deployed stability. Another object of the present invention is to provide a platform that is easily deployed and recovered. Yet another object of the present invention is to provide a platform design that is highly scalable, from large ocean going platforms used for energy production, to small lake-based platforms used to support small-scale instrumentation.  
           [0011]    According to the present invention, a telescoping spar structure includes a platform/hull for supporting a payload; a telescoping spar attached to the platform/hull that includes several interlocking tubes extending from a shallow end to a deep end of the spar, the tubes configured to telescope in and out of adjacent tubes such that the tubes are nestable together in a stowed configuration; a buoyancy chamber attached to the spar between shallow and deep ends of the spar; and, a damping chamber attached to the spar between the buoyancy chamber and the deep end of the spar, the damping chamber including: a first compartment for entraining a volume of water, a second compartment for enclosing deployment ballast, and a release mechanism for jettisoning the deployment ballast from the second compartment after the spar structure is deployed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic diagram illustrating an embodiment of the present invention in a pre-deployment configuration.  
         [0013]    [0013]FIG. 2 is a schematic diagram illustrating an embodiment of the present invention including ballast in a pre-deployment configuration.  
         [0014]    [0014]FIG. 3 is a schematic diagram illustrating an embodiment of the present invention including ballast in a partially deployed configuration.  
         [0015]    [0015]FIG. 4 is a schematic diagram illustrating an embodiment of the present invention in a fully deployed configuration after the ballast is jettisoned.  
         [0016]    FIGS.  5 A- 5 C are schematic diagrams of an embodiment of the present invention at various stages of deployment.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    A first embodiment of the present invention, illustrated in FIG. 1 in a pre-deployment configuration, concerns a multi-leg structure  10  to support, for example, undersea drilling operations. The structure  10  comprises four spars  12  (only two are shown), each spar  12  including a series of five concentric, thin-walled, telescoping tubes  14 . In FIG. 1, the spars  12  are shown in a pre-deployment, stowed configuration as would be used for example during transportation to a deployment site. The exact number of tubes  14 , their size and their length is mission dependent as the structure  10  can easily be scaled for different operating parameters. For lake and low sea-state applications, the length and/or the number of tubes  14  can be small. The deployed length of the tubes  14  is dictated by the stability requirements of the application, and one skilled in the art can select the proper size and number of telescoping tubes  14 . Material selection is also up to an individual designer. Plastic, steel, phenolic or even resin-coated paper, among many other materials, could be used in the construction of the spars  12 .  
         [0018]    The nested tubes  14  may be held together during storage and deployment by a simple locking mechanism (not shown in FIG. 1) that one skilled in the art can construct. The locking mechanism could be remotely activated, water-activated or time release activated to release the tubes  14  when needed during deployment. The tubes  14  are preferably sized so that they slide in and out freely. A series of joints  16  at the ends of the tubes  14  prevent the tubes from separating from each other when the spars  12  are extended. The joints  16  may be constructed such that the tubes  14  lock into place after deployment. For larger structures  10 , such as oil production platforms, the nested tubes  14  could be stored inside or on the platform/hull  26  so that the structure  10  could be more easily towed by a ship. During deployment, the tubes  14  would drop through the platform/hull  26  into their extended position.  
         [0019]    Although round tubing is an economical design selection, a variety of different designs could be used; for example, round tubes with weight reducing holes, elliptic or square tube stock. For applications where orientation of the telescoping tubes  14  is important, these materials would have some advantages over round stock. Also, a compound structure similar to a three-legged truss structure used in radio antenna towers could be used where higher strength is needed in the design. A telescoping  3 -legged buoy structure could be an excellent design for high sea state operation. However, whichever type of telescoping structure is used, the concepts of the present invention remain the same.  
         [0020]    [0020]FIG. 2 shows the same embodiment as FIG. 1, however ballast-filled damping chambers  20  are added to the spars  12 . The weight of the ballast  22  lowers the structure  10  in the water in preparation for deployment of the telescoping spars  12 .  
         [0021]    [0021]FIG. 3 shows the same embodiment as illustrated in FIGS. 1 &amp; 2; however the structure  10  is now partially deployed. After the pre-deployment locking mechanism is released, the force of gravity on the ballast  22  causes the spars  12  to become fully extended. Buoyancy chambers  18  are attached to the third telescoping tubes  14  and, whereas the chambers  18  were previously near the waterline  34 , they are now shown pulled deeper beneath the waterline  34 . In some embodiments, the chambers  18  buoyancy would be prohibitively large for the ballast  22  to effectively extend the spar  12  via gravity alone. In those cases, the chambers  18  can also be flooded to assist in extending the spars  12  to their operational length. The size of the buoyancy chambers  18  will depend on the weight of the structure  10  and its mission payload, e.g., from heavy and large oil rigs to lightweight and compact instrumentation, antennas, etc. The tube  14  to which the buoyancy chamber is attached is dependent on the sea-state. Again, one skilled in the art of spar buoy design can select the proper size for the buoyancy chambers  18 . In the present embodiment, placing the buoyancy chambers  18  on the third tube  14  is designed to place the chambers  18  at a relatively deep depth, out of the influence of most wave action. The buoyancy chambers  18  are attached to a tube  14  so that the smaller tubes  14  beneath the chamber  18  are not obstructed.  
         [0022]    [0022]FIG. 4 shows the same embodiment as illustrated in FIGS.  1 - 3 ; however the structure  10  is now filly deployed. After the spars  12  are fully extended and locked into place, the ballast  22  is jettisoned from the damping chamber  20 . For the case where the buoyancy chambers are buoyant, the mass reduction of the damping chamber  20  will cause the entire structure  10  to rise to its operational height relative to the waterline  34 . For the case where the buoyancy chambers  18  are not buoyant, after the spars  12  are fully extended and locked into place, air is pumped into the buoyancy chambers  18  and causes the entire structure  10  to rise to its operational height relative to the waterline  34 .  
         [0023]    Operation of the embodiment shown in FIGS.  1 - 4  is summarized as follows:  
         [0024]    1. The compact structure  10  is transported (e.g., shipped, towed, flown, etc.) to a deployment site. (FIG. 1.)  
         [0025]    2. At the deployment site, a damping chamber  20  including ballast  22  is connected to the compacted spars  12  of the structure  10 . Alternatively, or in addition to the ballast  22 , the buoyancy chambers  18  are flooded. (FIG. 2.)  
         [0026]    3. The spars  12  are deployed to their full length using gravity as the activation mechanism.  
         [0027]    4. The fully deployed spars  12  are locked into place. (FIG. 3.)  
         [0028]    5. The buoyancy chambers  18 , attached to the spars  12 , are filled with air and the expendable deployment ballast  22  is jettisoned from the damping chambers  20 . The structure  10  then rises to its operational height relative to the sea surface. (FIG. 4.)  
         [0029]    6. If necessary, mooring lines  28  are attached to the structure  10  and any work rigs  24  or instrumentation are placed on or assembled on the platform/hull  26 .  
         [0030]    7. Recovery reverses the deployment procedure; however, secondary cabling (not shown) running through the spars  12 , or other mechanisms, may be used to retract the spars  12  to their stowed configuration.  
         [0031]    The structure  10  is therefore both easy to deploy and recover and, primarily because of the reduced structural requirements of deployment and recovery, is relatively inexpensive to construct. These two features make the present invention useful and economical in numerous applications such as: small, less expensive oil exploration/production platforms; relatively small and cost-effective at-sea windmill/wave energy production platforms; and cost-effective oceanographic platforms for the detailed study of the environment.  
         [0032]    Note that FIGS.  1 - 4  illustrate only a single embodiment of the present invention and that those skilled in the art will readily appreciate other embodiments within the scope of the present invention. For example, small oceanographic platforms may use only a single telescoping spar according to the present invention, whereas larger oil platforms could employ many more spars than are illustrated in FIGS.  1 - 4 . The following additional details of the present embodiment should therefore be understood to apply equally well to numerous other embodiments.  
         [0033]    Referring again to FIGS.  1 - 4 , the buoyancy chambers  18  can be fabricated in a variety of ways. One construction technique would fabricate the chambers  18  of syntactic foam, making a fixed chamber. As suggested above, if one required variable buoyancy chambers  18 , the chambers  18  could be hollow (possibly with a flexible bladder) and air could be pumped into and out of the chambers  18  to change their buoyancy. The need for variable buoyancy chambers  18  is application dependent. Typically, one would use variable buoyancy chambers  18  in cases where the amount of ballast  22  to pull the buoyancy chamber  18  and telescoping spars  12  underwater to the proper deployment depth is prohibitively large.  
         [0034]    The shape of the buoyancy chambers  18  is an important design parameter. A high cross sectional area chamber close to the water surface could allow wave action to adversely affect the structure  10  stability. As known to those skilled in the art, an engineering study could be performed to optimize the depth of the buoyancy chambers  18  and the shape and size of the chambers  18 . Also, adding additional telescoping tubes  14  to the spars  12  and placing the chambers  18  deeper and farther from the wave effects could be simpler than designing a complex buoyancy chamber  18 .  
         [0035]    Stability of the structure  10  can also be improved by adding stabilization cables  30  (as shown in FIG. 4) between the spars  12 .  
         [0036]    If the platform/hull  26  needs to remain close to a constant level above the waterline  34 , then the spars should have buoyancy at the waterline  34 . Since the telescoping tubes  14  may be negatively buoyant, a “trim” floatation section (not shown in the Figures) should be added to the tubes  14  near the waterline  34 . The trim floatation can be as simple as a closed-cell foam collar around the tubes  14  extending a length above and below the waterline  34 . The amount of buoyancy the collar provides per its submerged length is selected to give the structure  10  its required “spring constant” for stable operation in a selected sea state. This spring constant is one element that determines the structure&#39;s resonance frequency and is selected to be much lower than the lowest expected wave frequency.  
         [0037]    The platform/hull  26  may also act as a reserve buoyancy chamber at the top of the spars  12  and help ensure that the work rig  24  remains above water. The floatation provided by the platform/hull  26  is sized in at least one embodiment to support generally two to three times the deployment ballast  22 . In some applications, the reserve buoyancy of the floatation is an important component of the structure  10  and is used in the deployment sequence.  
         [0038]    The damping chamber  20  is attached to or near the bottom tube  14  via a rope, chain or other type of connection device  32 . In addition to storing ballast  22 , the chamber&#39;s function is to add mass to the structure  10  by entraining water when the chamber  20  is in the water without adding weight to the structure  10  when the chamber  20  is out of the water. The added mass of the entrained water effectively lowers the structure&#39;s resonance frequency and thus makes the structure more stable in high sea-states. A single compartment in the chamber  20  can serve the function of storing both ballast  22  and entrained water by simply providing porous walls to the chamber that prevent the ballast from falling out but still allow water to enter. Also, the chamber  20  can be used to store fixed ballast (not shown in the Figures) that would not be released during deployment of the structure  10  but would remain enclosed in the damping chamber  20  as additional stabilizing mass. One skilled in the art can readily select the proper size and shape of the damping chamber(s)  20 .  
         [0039]    As discussed above, the damping chamber  20  includes a release mechanism (not shown in the Figures) that jettisons the expendable deployment ballast  22  at the proper time in the deployment sequence. The release mechanism can be an automatic, time-delayed, water-activated mechanism that opens a trap door  36  or a remote controlled mechanism under the control of the deployment operator. When the trap door  36  is opened, the deployment ballast  22  is released. The deployment ballast  22  can be any number of different materials: sand, rocks, or other environment-friendly material.  
         [0040]    Much smaller scale applications of the present invention are also possible. For example, a second embodiment of the present invention is a three-leg  12  weather system that can also be described in reference to FIGS.  1 - 4  (the third spar however is not shown). Weather sensors (e.g., anemometer, wind vane, thermometer, etc.) would be located on the platform/hull  26 , and a data acquisition system (DAS) could be located in a waterproof housing on the platform/hull  26 . A battery pack could be located at the bottom of one spar  12  so that it serves as ballast and contributes to the system&#39;s stability without additional nonfunctional mass. A power cable could be designed to extend the length of the telescoped spars  12  to the battery pack.  
         [0041]    If a mission required recovery of the weather system, the system would also include a recovery winch or similar mechanism to draw the telescoped spars  12  back into their retracted position. One possible design again uses gravity to pull the extended spars  12  back together. A second ballast material could be deployed from the recovery vessel where the ballast is connected to lines that would pull the telescoping spars  12 , after the locking mechanisms are disengaged, back into their retracted position.  
         [0042]    Other variations to small-scale embodiments of the present invention include the use of deflatable or expendable reserve buoyancy at the platform/hull  26 . As described above, the spar structure  10  is initially ballasted to place the platform/hull  26  at its operational height. The addition of the expendable ballast  22  sinks the structure  10  to the waterline of the reserve buoyancy provided by the platform/hull  26 . The reserve buoyancy of the platform/hull  26  supports the top of the structure  10  while the weight of the ballast  22  extends the spars  12 . After the spars  12  extend to their deployed position and are locked into place, the expendable ballast  22  is jettisoned. Without the expendable ballast  22 , the structure  10  and payload on the platform/hull  26  rises to its operational height relative to the waterline  34 . However, in some cases the deployed platform/hull  26  will not be able to support the material (e.g., inflatable device, floatation material, etc.) required to provide the necessary pre-deployment reserve buoyancy. For example, some systems may require a large amount of expendable ballast, and would therefore require significant reserve buoyancy material at the platform/hull  26  to keep a payload dry. In such cases the reserve buoyancy material could be expendable or it could comprise an inflatable device such as an air-filled tube/collar. After the structure  10  is deployed, the reserve buoyancy material could be deflated or released from the platform/hull  26  so that it drops to the waterline so that it rides up and down the spar(s)  12  along with any wave action. A scientific meteorological package is an example of a payload that could require the reserve buoyancy material to be removed after deployment. The relatively large mechanical structure of the reserve buoyancy material could distort airflow around the wind instrumentation of the meteorological package and compromise the wind measurements.  
         [0043]    Referring to FIGS.  5 A- 5 C, following is a more detailed description of a ship-based deployment and recovery of an embodiment of the present invention. In this embodiment it is again assumed that the structure  10  is a relatively small, single spar  12  system, such as the weather system described above, that can be deployed from a suitable sized ship or aircraft. It is also assumed that the buoyancy of the structure is fixed so that the buoyancy chamber  18  does not need to be adjusted during deployment and recovery. However, one skilled in the art could modify the deployment and recovery procedure described here to account for a variable buoyancy system. (The shipboard activities are not illustrated in FIGS.  5 A- 5 C.)  
         [0044]    An example of a deployment procedure is as follows:  
         [0045]    1. The structure  10  is disengaged from a deck-mounted cradle on a ship and connected to a deploying crane or U-frame.  
         [0046]    2. The structure  10  is lifted vertically and placed just above the water while the ship is moving slowly forward.  
         [0047]    3. The damping chamber  20  is then pushed off the ship and into the water at the same time that the structure  10  is released from the crane or U-frame via a quick disconnect or similar device.  
         [0048]    4. The structure  10  then sinks up to the reserve buoyancy platform/hull  26 . (FIG. 5A.)  
         [0049]    5. A water-activated release device (or remote release device) on a release drum spool allows the ballast  22  to extend the nested tubes  14  to their full length and the telescoping spar joints  16  to lock into position. (FIG. 5B.)  
         [0050]    6. A short time later the water-activated trap door  36  on the damping chamber  18  releases the expendable deployment ballast  22 .  
         [0051]    7. The structure  10 , more buoyant after the release of the expendable ballast  22 , then rises up to its operating height. (FIG. 5C.)  
         [0052]    Advantages of the deployment operation shown above include the fact that the ship simply drops the structure  10  overboard and moves away—the deployment is automatic. Further, the automatic deployment mechanism is simple and passive; it relies on only the water activated release and gravity for its power. Assuming proper design and clearances, the telescoping tubes  14  simply fall into place. Finally, if some mechanism does manage to jam, the action of the structure  10  in the waves will more than likely “wiggle” the jammed parts free. The higher the sea state, the more likely the structure  10  will properly deploy. Such a feature is superior to conventional spar designs that are less likely to deploy in high sea states.  
         [0053]    An example of a recovery procedure is as follows:  
         [0054]    1. The ship approaches the structure  10  and activates the recovery procedure with a simple remote control device.  
         [0055]    2. A winch motor (in the mission package) is activated by the remote control and pulls the ballast  22  and the lower tube section  14  up into the first tube  14  at the waterline  34 .  
         [0056]    3. The ship uses a grappling hook to recover a lifting line attached to a small float. The other end of the lifting line is attached to the lift point on the top of the structure  10 .  
         [0057]    4. The ship then proceeds to haul in the structure  10  like any other wave riding buoy.  
         [0058]    Other options that could be included in the recovery procedure include jettisoning the damping chamber  20 . A lower capacity winch could be used to pull in the extended tubes  14  if the ballast weight of the chamber  20  were not present. The damping chamber  20  could also be recovered with a separate tag line and pulled aboard the ship. Also, if the seas were too high for an easy recovery, the structure  10  could have an optional, built-in release mechanism (e.g., pull pin) that would drop all parts of the structure  10  except the platform/hull  26  that presumably supports an expensive payload that is worth the effort to retrieve.  
         [0059]    Finally, if the structure  10  were designed as an expendable system, then a recovery system would not be required. In that case, the joints  16  could be made very simply by using a very long tamper fit. The lower circumference of the outside tubes  14  could be flared in and the upper circumference of the inside tubes  14  could be flared out. The speed damper mechanism could be reduced in size or eliminated altogether and the joints  16  allowed to jam into place. As an expendable system, the mechanical structure could also be of a biodegradable configuration such as resin/wax coated paper. The resin/wax could be designed with a finite water proofing life and after it degrades the paper structure of the system would dissolve in the water.  
         [0060]    The above therefore discloses a telescoping spar platform apparatus and method for deploying, using, and recovering the same. Alterations, modifications, and improvements concerning various other applications will readily occur to those skilled in the art. Such alterations, modifications and improvements as are made obvious by this disclosure are intended to be part of this description though not expressly stated herein, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and not limiting. The invention is limited only as defined in the following claims and equivalents thereto.