WO2013126325A1

WO2013126325A1 - Mooring cable for transmitting oceanographic data

Info

Publication number: WO2013126325A1
Application number: PCT/US2013/026651
Authority: WO
Inventors: Noah LAWRENCE-SLAVAS; Richard Nye; Chad MURDOCK
Original assignee: Actuant Corporation
Priority date: 2012-02-20
Filing date: 2013-02-19
Publication date: 2013-08-29

Abstract

An apparatus for transmitting oceanographic data includes a mooring cable having a data transmission cable configured to transmit the oceanographic data. A reinforcement layer surrounds the data transmission cable, and a protective outer jacket surrounds the reinforcement layer. The mooring cable has sections of different densities to provide the mooring cable with an inverse catenary shape. These sections include a first section defined by the data transmission cable, the reinforcement layer, and the protective outer jacket. A second section configured to sink in sea water transitions to the first section and is defined by the reinforcement layer and the protective outer jacket. A third section transitions to the second section and is defined by the reinforcement layer. A fourth section configured to float in sea water transitions to the third section and is defined by the reinforcement layer.

Description

MOORING CABLE FOR TRANSMITTING OCEANOGRAPHIC DATA Technical Field

[0001] This invention relates to mooring cables, particularly mooring cables for in situ monitoring of oceanographic conditions.

Background Art

[0002] In recent years the implications of global climate change and the effects climate phenomena such as El Nino Southern Oscillation (ENSO), the Pacific Decadal and Pentadecadal Oscillations (PDO and PPO), and the North Atlantic Oscillation (NAO) have created a need for increased insitu monitoring of the world's oceans. Because remote sensing technology (i.e., satellite technology) is unable to penetrate the ocean surface, mooring cables that extend from the surface to the sea floor and gather real-time subsurface oceanographic data have proven to be valuable.

[0003] In order to obtain global subsurface data with a resolution appropriate for use with climate prediction models, a large-scale global observational array of such mooring cables needs to be implemented. However, previous mooring cable designs for obtaining oceanographic data have inherent weaknesses that limit their use in such an array. One such weakness is localized bending stress concentrations within the cable that can cause premature failure. These stress concentrations are formed because different sections of the mooring cable (i.e., portions of the mooring cable at different depths) have different requirements. For example, the upper sections of mooring cables typically include fish bite resistance whereas lower sections do not. For this reason and others, the sections of mooring cables typically include different materials. These different materials have different mechanical properties, such as bending stiffness. Depending on the difference in bending stiffness between two adjacent sections of the mooring cable, a large amount of bending can occur in a less stiff material proximate the interface with a more stiff material, thereby forming a stress concentration at the interface between the sections.

[0004] Furthermore, deployment of the above multi-section mooring cables is relatively difficult because shackles are used to connect the different sections. That is, the different sections are initially wound on different reels because the shackles inhibit the sections from being connected and wound on a single reel. Instead and during deployment, a section of the mooring cable is paid out and then the adjacent section is shackled to the first and paid out. This process continues until all the sections are shackled together and paid out. Such a process is relatively complicated, labor-intensive, and requires many experienced seagoing mooring technicians to ensure proper deployment.

[0005] Other weaknesses of previous mooring cable designs include an inability to telemeter in situ subsurface data from the surface to the sea floor, or the ability to telemeter this data but at a very high cost, the need for large surface buoys to support the weight and ocean current load (i.e., drag forces) caused by bulky mooring cables, and the need for large, expensive, and logistically-limited oceanographic deployment/servicing vessels.

[0006] As such, a need exists for a mooring cable for in situ monitoring of

oceanographic conditions that addresses one or more of the above weaknesses of previous designs.

Disclosure of Invention

[0007] In one aspect, the present invention provides an apparatus for transmitting oceanographic data. The apparatus comprises a mooring cable that includes a data transmission cable configured to transmit the

oceanographic data. A reinforcement layer surrounds the data

transmission cable, and a protective outer jacket surrounds the

reinforcement layer. The mooring cable has sections of different densities to provide the mooring cable with an inverse catenary shape. These sections include a first section defined by the data transmission cable, the reinforcement layer, and the protective outer jacket. A second section transitions to the first section and is defined by the reinforcement layer and the protective outer jacket, and the second section is configured to sink in sea water. A third section transitions to the second section and is defined by the reinforcement layer. The protective outer jacket is absent at the third section, and there is a smooth transition in bending stiffness between the protective outer jacket of the second section and the reinforcement layer of the third section. A fourth section transitions to the third section and is defined by the reinforcement layer. The protective outer jacket is absent at the fourth section, and the fourth section is configured to float in sea water.

[0008] In another aspect, the present invention provides an apparatus for

transmitting oceanographic data. The apparatus includes a buoy configured to transmit the oceanographic data to a remote receiving station and an anchor configured to be positioned on the sea floor. A mooring cable connects the buoy and the anchor, and the mooring cable has sections of different densities to provide the mooring cable with an inverse catenary shape. The sections include a first section adjacent the buoy and a second section connected to the first section opposite the buoy. The second section is configured to sink in sea water. A third section transitions to the second section opposite the first section, and a fourth section transitions to the third section opposite the second section and proximate the anchor. The fourth section is configured to float in sea water. The mooring cable further includes a data transmission cable extending from the buoy to the anchor and in part defining the first, second, third, and fourth sections of the mooring cable. The data transmission cable is configured to transmit the oceanographic data to the buoy. The mooring cable further includes a reinforcement layer in part defining the first, second, third, and fourth sections of the mooring cable and surrounding the data transmission cable. The reinforcement layer extends substantially from the buoy to the anchor along the length of the data transmission cable.

[0009] The foregoing and other aspects of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention.

Brief Description of Drawings

[0010] FIG. 1 is a side view of an apparatus for transmitting oceanographic data according to the present invention;

[001 1] FIG. 2 is a side view of a mooring cable of the apparatus of FIG. 1 ;

[0012] FIG. 3 is a perspective sectional view of the mooring cable within line 3-3 of FIG. 2; portions of outer layers of the cable are hidden to illustrate inner layers;

[0013] FIG. 4 is a perspective sectional view of the mooring cable within line 4-4 of FIG. 2; portions of outer layers of the cable are hidden to illustrate inner layers;

[0014] FIG. 5 is a perspective detail view of a strain relief carrot of the mooring cable within line 5-5 of FIG. 2;

[0015] FIG. 6 is a perspective sectional view of the mooring cable within line 6-6 of FIG. 2; portions of outer layers of the cable are hidden to illustrate inner layers;

[0016] FIG. 7 is a perspective sectional view of the mooring cable within line 7-7 of FIG. 2; portions of outer layers of the cable are hidden to illustrate inner layers; and

[0017] FIG. 8 is a perspective sectional view of the mooring cable within line 8-8 of FIG. 2; portions of outer layers of the cable are hidden to illustrate inner layers.

Best Mode for Carrying Out the Invention

[0018] Referring to FIGS. 1 and 2, an apparatus 10 for transmitting

oceanographic data according to the present invention includes a buoy 12 that supports a subsurface mooring cable 14. An anchor 16 that rests on the sea floor transitions to the opposite end of the mooring cable 14 and limits motion of the buoy 12 and the mooring cable 14. The mooring cable 14 advantageously has smooth transitions in bending stiffness along its length to inhibit the development of stress concentrations that could otherwise cause premature failure. Furthermore, the mooring cable 14 facilitates low-cost real-time data telemetry of in situ oceanographic parameters, in some embodiments, throughout the entire water column from the sea surface to the sea floor. Such a structure also permits the apparatus 10 to be deployed as a cost-effective "easy to deploy" (ETD) system. In the following paragraphs, these advantages and the structures of the apparatus 10 that facilitate these advantages are described in further detail.

[0019] Referring particularly to FIG. 1 , the buoy 12 is configured to float and

maintain at least of portion of the apparatus 10 at the sea surface. The buoy 12 also houses or supports communication components (not shown) that transmit oceanic data obtained by the apparatus 10 to a remote receiving station (e.g., a satellite in communication with a sea or land- based research facility).

[0020] Referring now to FIGS. 2-8 and particularly FIG. 2, the mooring cable 14 generally includes a plurality of sections that define an inverse catenary shape. That is, the mooring cable 14 has vertically extending sections that are separated by a sideways S-shaped section. Such a shape provides the mooring cable 14 with slack between the surface and the sea floor while inhibiting the section proximate the anchor 16 from contacting and becoming fouled on the sea floor.

[0021] As described in further detail below, the mooring cable 14 includes some components or layers that partially define the different sections. Other components and layers differ between the sections, although smooth transitions are provided between such varying materials (or varying material dimensions) such that the overall properties of the mooring cable 14 (e.g., bending stiffness) change gradually to inhibit the formation of stress concentrations that could otherwise lead to premature failure.

[0022] Turning now to the specific sections of the mooring cable 14 and as shown in FIGS. 2 and 3, a first or upper section 18 of the cable 14 connects to the buoy 12. In some embodiments, the upper section 18 is approximately 700 meters long and has a specific gravity (compared to sea water) that is greater than 1.03 (i.e., is more dense than sea water) such that it sinks in sea water. [0023] As shown in FIG. 3, at its center, the upper section 18 includes a data transmission cable 20 that operatively connects to the communication components housed by the buoy 12. The data transmission cable 20 is preferably a #21 AWG (768 CMA) Hi-Wire™ cable available from Cortland Cable of Cortland, New York. Such a cable comprises 12 strands of #32 AWG (0.008 inch diameter) plated copper wires helically wrapped at 6.5 turns per inch (about 47 degrees) around a 0.044 inch diameter nylon monofilament core. Such a cable also has a minimum elongation of 18 percent before failure. In addition to the data transmission cable, or in lieu thereof, other cables, lines or tubes for transmitting something from one end of the mooring cable to the other, can be used. For example, other transmitting cables, lines or tubes incorporated into the mooring line, and run from the buoy to the anchor, can be an optical cable, a natural gas line, or a hydraulic fluid line (not shown).

[0024] At its end proximate the buoy 12, the data transmission cable 20 is

uncovered for approximately one meter to contact the water. As such, the data transmission cable 20 forms part of an inductive coupling circuit described in further detail below.

[0025] Beginning approximately one meter below the buoy 12, the upper section 18 includes an insulation layer 22 that surrounds the data transmission cable 20. The layer 22 is preferably polypropylene with a water absorption of about 0.02 percent to 0.07 percent, such as Pro-fax EP315J available from LyondellBasell Industries of Rotterdam, the Netherlands. The layer 22 is preferably about 0.021 inches thick to provide a nominal diameter of about 0.105 inches over the data transmission cable 20. Such a layer 22, together with the data transmission cable 20, provides an insulating, low water permeability barrier around the data transmission cable 20.

[0026] To provide the cable 14 with tensile and bending strength, the upper

section 18 includes a strength member or reinforcement layer 24 that surrounds the insulation layer 22. In the upper section 18, the

reinforcement layer 24 is preferably a 12-strand liquid crystalline polyester (LCP)/high modulus polyethylene (HMPE) BOB™ (Blend Optimized for Bending) with a wear resistant coating available from Cortland Cable. The reinforcement layer 24 preferably defines an outer diameter over the data transmission cable 20 and the insulation layer 22 of approximately 0.21 inches.

[0027] The reinforcement layer 24 is itself wrapped in multiple layers for

protection. A first such layer in the upper section 18 is a helically extending protective tape 26, such as polytetrafluoroethylene (PTFE, i.e., Teflon®) tape having a width of one inch and a thickness of 0.003 inches.

[0028] The majority of the protective tape 26 (i.e., approximately 650 meters of the 700 meters of the upper section 18) is in turn wrapped in a fish bite protection layer or tape 28 that extends helically in the other direction than the protective tape 26. The fish bite protection layer 28 is capable of withstanding strikes by four to six foot warm water sharks without damaging the reinforcement layer 24. To this end, the fish bite protection layer 28 is preferably a non-conducting material such as a woven fabric of aramid fibers with a ceramic coating. In addition, the fish bite protection layer 28 is preferably wrapped so that it overlaps itself between 10 and 20 percent of its width. This construction inhibits the layer 28 from "opening" (i.e., moving such that the reinforcement layer 24 is exposed between portions of the layer 28) during cyclic loading and bending motions.

Furthermore, helically wrapping the fish bite protection layer 28 also allows the mooring cable 14 to stretch to some extent under load without causing the fish bite protection layer 28 to break (i.e., the wrapping gives the fish bite protection layer 28 some ability to stretch with the reinforcement layer 24).

[0029] At appoximately 650 meters from the buoy 12, the lower end of the fish bite protection layer 28 mechanically connects to a filler tape 30. The filler tape 30 surrounds the protective tape 26 and, like the adjacent fish bite protection layer 28, extends helically in the other direction than the protective tape 26. Also like the fish bite protection layer 28, the filler tape 30 is preferably wrapped so that it overlaps itself between 10 and 20 percent of its width to inhibit "opening". The filler tape 30 may be less capable of withstanding shark strikes than the fish bite protection layer 28 because fish are less common at such a depth. As such, the filler tape 30 is preferably a polyester tape having a thickness of 0.008 inches. In any case, the filler tape 30 serves as a "bending limiter" to smooth the bending stiffness transition between the upper section 18 of the mooring cable 14 and the adjacent section.

[0030] The fish bite protection layer 28 and the filler tape 30 are both surrounded by an additional protective layer 32. This layer 32 is preferably

polyethylene terephthalate (PET, i.e., Mylar®) having a thickness of about 0.001 inches.

[0031] As a final component of the upper section 18 of the mooring cable 14, a protective outer jacket 34 surrounds the protective layer 32. The outer jacket 34 preferably adds 155 to 180 lbs in total weight to the mooring cable 14 and is preferably a combination of stainless steel and Texin 9- 90R, Shore A 90 durometer, black polyether-type thermoplastic polyurethane available from Bayer Material Science of Pittsburgh, Pennsylvania. The preferred stainless steel and thermoplastic

polyurethane mixture has a specific gravity of 2.00 g/cc and is 4704ZC50 available from Ecomass Technologies of Austin, Texas. The outer jacket 34 also includes a plurality of ridges 36 to provide strum suppression and reduce current drag force on the mooring cable 14. In some

embodiments, the outer jacket 34 may have nine parallel ridges 36 equally spaced from one another and extending helically about the jacket 34 with a 36-inch period. Furthermore, in some embodiments the ridges 36 may have a nominal height of 0.015 inches and define an outer diameter of approximately 0.40 inches.

[0032] Turning now to FIGS. 2 and 4, at approximately 700 meters from the buoy 12, the upper section 18 interfaces with a weighted or second section 38 of the mooring cable 14. The second section 38 is approximately 400 meters long and has a specific gravity (compared to sea water) that is greater than 1.03 such that it sinks in sea water.

[0033] Some of the components of the first section 18 also partially define the second section 38 and continuously extend over the length of the two sections. In particular, the data transmission cable 20 described above continuously extends from the first section 18 to the second section 38 and is disposed at the center of the second section 38. The insulation layer 22 described above also continuously extends from the first section 18 to the second section 38 and surrounds the data transmission cable 20.

[0034] Other components terminate at the interface of the first section 18 and the second section 38, although smooth transitions are provided to inhibit the formation of stress concentrations. In particular, proximate the interface between the two sections 18, 38, the data transmission cable 20 and the insulation layer 22 are surrounded by a machine splice 39 (FIG. 2) that connects the fibers of the reinforcement layer 24 of the first section 18 to the fibers of the reinforcement layer 24 of the second section 38. The machine splice 39 is preferably at least 50 meters in length to provide a smooth bending stiffness transition between the reinforcement layer 24 in the first section 18 and the second section 38. The machine splice 39 is wrapped in the protective tape 26 as described above, which is in turn wrapped in the filler tape 30 as described above. In addition, the filler tape 30 is in turn wrapped in the additional protective layer 32 as described above.

[0035] As briefly described above and as shown in FIG. 4, past the machine

splice 39, the insulation layer 22 is directly surrounded by the

reinforcement layer 24. In the second section 38, the reinforcement layer 24 is preferably a fatigue-resistant 12-strand braided blend including eight strands of polyester and four strands of LCP available from Cortland Cable. The LCP strands preferably include two left lay and two right lay strands to maintain the torque balance of the layer. In addition, the layer preferably has a total stretch of less than 12 percent at 63 percent of the rated breaking strength (RBS) of the cable 14 and defines an outer diameter over of approximately 0.28 inches.

[0036] The outer protective jacket 34 continuously extends from the first section 18 and over the entire length of the second section 38 of the mooring cable 14 (i.e., directly over both the protective layer 32 and the

reinforcement layer 24). By extending over both sections 18, 38, the outer protective jacket 34 smoothes the transition in bending stiffness along the two sections 18, 38. In the second section 38, the outer protective jacket 34 also has features as described above.

[0037] Turning now to FIGS. 2 and 5, immediately before the distal end of the second section 38 (e.g., about 0.25 meters before the end), a strain relief carrot 40 connects to the second section 38 and extends over 0.5 meters of an adjacent section of the mooring cable 14 that lacks the outer protective jacket 34. The strain relief carrot 40 provides a smooth change in bending stiffness between the adjacent sections of the mooring cable 14. For this reason, the strain relief carrot 40 preferably has an elongated barrel-like shape in which it tapers inwardly toward its ends and bows outwardly near the middle. Furthermore, the strain relief carrot 40 preferably comprises a semi-rigid material, such as Flexane 80 available from ITW Devcon of Danvers, Massachusetts.

[0038] Within the strain relief carrot 40, the second section 38 interfaces with a blended or third section 42 of the mooring cable 14. Turning to FIGS. 2 and 6, the third section 42 has a specific gravity (compared to sea water) that is approximately equal to 1.03, the specific gravity of sea water. The length of the third section 42 may vary depending on the nominal depth at which the apparatus 10 is to be deployed. Exemplary lengths of the third section 42 are shown in the following table.

[0039]

Table 1

Exemplary Mooring Lengths (in meters)

Depth 3000 3400 4000 4700 5000

First Section 700 700 700 700 700

Second Section 400 400 400 400 400

Third Section 970 1246 1660 2143 2350

Fourth Section 1380 1564 1840 2162 2300 Fifth Section 12 12 12 12 12

Overall Length 3462 3922 4612 5417 5762

[0040] Some of the above components also partially define the third section 42 and continuously extend from the second section 38 to the third section 42. In particular, the data transmission cable 20 described above continuously extends from the second section 38 to the third section 42 and is disposed at the center of the third section 42. The insulation layer 22 described above also continuously extends from the second section 38 to the third section 42 and surrounds the data transmission cable 20.

[0041] Beginning at approximately 1250 meters from the buoy 12, the insulation layer 22 in the third section 42 is surrounded by a highly flexible second insulation layer 44. The second insulation layer 44 is preferably a thermoplastic elastomer with a water absorption of about 0.1 percent and a specific gravity of about 0.89, such as TP5280 available from T&T Marketing Inc. of Allamuchy, New Jersey. The layer 44 is preferably about 0.052 inches thick to provide a nominal diameter of about 0.209 inches over the first insulation layer 22. Such an insulation layer 44 facilitates the "neutral" specific gravity of the third section 42 of the mooring cable 14 and, in turn, the inverse catenary shape of the mooring cable 14.

[0042] The second insulation layer 44, and the first insulation layer 22 when the second layer 44 is absent in the third section 42, are directly surrounded by the reinforcement layer 24. In the third section 42, the reinforcement layer 24 is preferably the same polyester/LCP braided blend as in the second section 38. As such, a machine splice does not connect the reinforcement layer 24 between the second and third sections 38, 42.

[0043] Unlike the above sections, the reinforcement layer 24 defines the

outermost layer in the third section 42 of the mooring cable 14. That is, and as described briefly above, the outer protective jacket 34 is absent in the third section 42 of the mooring cable 14.

[0044] At its distal end, the third section 42 interfaces with a fourth section 46 of the mooring cable 14. Turning to FIGS. 2 and 7, the fourth section 46 has a specific gravity (compared to sea water) that is at most approximately 0.96 such that it floats in sea water. Like the third section 42, the length of the fourth section 46 may vary depending on the nominal depth at which the apparatus 10 is to be deployed. Exemplary lengths of the fourth section 46 are shown in the above table.

[0045] Some of the above components also partially define the fourth section 46 and continuously extend from the third section 42 to the fourth section 46. In particular, the data transmission cable 20 described above continuously extends from the third section 42 to the fourth section 46 and is disposed at the center of the fourth section 46. The first insulation layer 22 described above continuously extends from the third section 42 to the fourth section 46 and surrounds the data transmission cable 20. The second insulation layer 44 is also present in the fourth section 46 and surrounds the first insulation layer 22. However, starting at about 10 meters past the end of the splice interface with the third section 42 and for the remainder of the fourth section 46, the second insulation layer 44 has a thickness of about 0.108 inches to provide a nominal diameter of about 0.320 inches over the first insulation layer 22. The thicker insulation layer 44 facilitates a smooth bending stiffness transition between the third and fourth sections 46, 52. In addition, the thicker insulation layer 44 facilitates the relatively low specific gravity of the fourth section 46 of the mooring cable 14 and, in turn, the inverse catenary shape of the mooring cable 14.

[0046] Other components terminate at the interface of the third section 42 and the fourth section 46, although smooth transitions are provided to inhibit the formation of stress concentrations. In particular, proximate the interface between the two sections 42, 46, the insulation layer 44 is surrounded by a machine splice 48. The machine splice 48 is preferably at least 50 meters in length to provide a smooth bending stiffness transition between the reinforcement layer 24 in the third section 42 and the fourth section 46.

[0047] As briefly described above, past the machine splice, the second insulation layer 44 is surrounded by the reinforcement layer 24. In the fourth section 46, the reinforcement layer 24 is preferably a 12-strand braided blend including eight strands of 12-X soft multi-filament polypropylene (MFP) available from Guelph Twines of Guelph, Ontario, Canada and four strands of HMPE available from Cortland Cable. The HMPE strands preferably include two left lay and two right lay strands to maintain the torque balance of the layer. In addition, the layer preferably has a total stretch of less than 12 percent at 63 percent RBS and defines an outer diameter of approximately 0.50 inches.

[0048] Immediately before the distal end of the fourth section 46 (e.g., about several meters before the end), a strain relief carrot 50 (FIG. 2) connects to the fourth section 46 and extends over several meters of an adjacent section of the mooring cable 14 that includes an addition woven layer. Like the first strain relief carrot 40, the second carrot 50 provides a smooth change in bending stiffness between the adjacent sections of the mooring cable 14. For this reason, the strain relief carrot 50 preferably has an elongated barrel-like shape in which it tapers inwardly toward its ends and bows outwardly near the middle. Furthermore, the strain relief carrot 50 preferably comprises a semi-rigid material, such as Flexane 80.

[0049] Within the strain relief carrot 50, the fourth section 46 interfaces with a fifth section 52 of the mooring cable 14. Turning to FIGS. 2 and 8, the fifth section 52 is relatively short compared to the other sections; in particular, the fifth section 52 preferably has a length of approximately 12 meters.

[0050] The data transmission cable 20, the first insulating layer 22, the second insulating layer 44, and the MFP/HMPE reinforcement layer 24 described above continuously extend from the fourth section 46 to the fifth section 52 of the mooring cable 14. In addition, a chafe resistant reinforcement layer 54 surrounds the MFP/HMPE reinforcement layer 24 within the fifth section 52. At its upper end within the strain relief carrot 50, the chafe resistant reinforcement layer 54 is preferably whipped to the MFP/HMPE reinforcement layer 24 to inhibit unraveling. In addition, the chafe resistant reinforcement layer 54 is preferably a 12-strand braid of 12-X HMPE available from Cortland Cable that defines an outer diameter of

approximately 0.75 inches.

[0051] At the distal end of the fifth section 52, the data transmission cable 20 and the MFP/HMPE reinforcement layer 24 extend outside of the chafe resistant reinforcement layer 54 for approximately one meter, which connects to the anchor 16 via a splice (not shown). The data transmission cable 20 contacts the water to form an inductive coupling circuit including the cable 20 and the sea water between the buoy 12 and the anchor 16. As such, a plurality of sensors (e.g., sensors configured to sense pressure, salinity, current speed, temperature, and/or the like) supported along the length of the mooring cable 14 and in contact with the sea water may transmit data over the circuit to the communication components supported by the buoy 12.

The mooring cable 14 is generally manufactured as follows. First, the data transmission cable 20 is formed in a length sufficient to continuously extend from the first section 18 through the fifth section 52 of the mooring cable 14. Next, the insulation layers 22, 44 are extruded over the data transmission cable 20 at the appropriate sections of the mooring cable 14. The different diameter sections of the second insulating layer 44 are extruded in separate steps. The insulated data cable is then passed through a braider that braids the reinforcement layer 24 about the cable. A relatively high amount of back tension is preferably applied to the braider to minimize the constructional stretch of the cable. In addition and as described above, machine splices 39, 48 are formed at interfaces where the reinforcement layer 24 changes materials. Next, the protective tape 26, the fish bite protection layer 28, and the protective layer 32 are wrapped around the reinforcement layer 24 in the first section 18 of the mooring cable 14 while the cable is under a tension of 50 to 150 lbs. The outer protective jacket 34 is then extruded as a single continuous component over the first and second sections 18, 38 of the cable 14 while the cable is under a tension of 50 to 150 lbs. The chafe resistant reinforcement layer 54 is braided over and whipped to the reinforcement layer 24 in the fifth section 52 of the mooring cable 14. To complete the mooring cable 14, the strain relief carrots 40, 50 are molded over the cable at the appropriate locations. For molding the carrot 40, the cable 14 is hanged vertically and subjected to a relatively low amount of tension (e.g., 20 to 50 lbs). The reinforcement layer 24 is coated with a line stiffener, such as Intershield 259 available from International Marine, along a length of two to three meters adjacent to the end of the protective jacket 34. After the line stiffener dries, the portion of the cable 14 beneath the carrot mold is wrapped with a single layer of Teflon® tape. The mold is then positioned such that the protective jacket 34 extends approximately 0.13 meters into the mold, and the mold is filled with the semi-rigid material that forms the carrot 40 (e.g., Flexane 80). The second carrot 50 is formed in a similar manner.

[0053] After the above steps, the mooring cable 14 is wrapped around a single reel supported by a pallet, and one end of the cable 14 is connected to the buoy 12 and the other end is connected to the anchor 16. The assembly is then enclosed and shipped for deployment. To deploy the apparatus 10, the pallet is pushed from a deployment vessel such that the anchor 16 sinks to the sea floor while the buoy 12 remains at the surface to unravel the mooring cable 14 from the reel. Such an "easy-to-deploy" process is considerably less labor-intensive than previous deployment methods in which different sections of mooring cables were paid out and shackled together.

[0054] The apparatus 10 may be modified in other manners that are not explicitly described above. For example, the mooring cable 14 can be other lengths than those described above to facilitate placement at other ocean depths. As another example, the different sections of the mooring cable 14 could use different materials than those described above.

[0055] Similarly and in some embodiments, the data transmission cable 20 may only be present in the upper section 18 of the mooring cable 14. In such embodiments, the reinforcement layer 24 within the second and third sections 38, 42 of the mooring cable 14 may be a 12-strand braid of polyester available from Cortland Cable. The reinforcement layer 24 within the fourth and fifth sections 46, 52 of the mooring cable 14 may be a 12-strand braid of co-polymer (e.g., Polysteel™ Fiber available from Polysteel Atlantic Limited of Edwardsville, Nova Scotia, Canada) having a specific gravity of at most 0.94, such as Co-Polymer 12-Strand rope available from Cortland Cable. [0056] From the above description, it should be apparent that the present invention provides an apparatus for transmitting oceanographic data that provides various advantages over previous devices. In particular, the continuous mooring cable 14 facilitates an "easy-to-deploy" process that is considerably less labor-intensive than previous deployment methods in which different sections of mooring cables were paid out and shackled together. As another example, the reinforcement layer 24 includes different density materials in the different sections of the mooring cable 14 to facilitate smooth bending transitions. Similarly, the outer protective jacket 34 smoothes over changes in the mooring cable's 14 bending stiffness along the first and second sections 18, 38. The reinforcement layer 24 and the data transmission cable 20 have the capability to withstand high amounts of repeated bending and tension loading cycles. The data transmission cable 20 and the surrounding insulation layers also provide several advantages. For example, in some embodiments, the data transmission cable 20 extends from the first section 18 through the fifth section 52 of the mooring cable 14 to facilitate simplified data transmission compared to previous cable designs. As another example, the cable has a bending radius of less than 1 inch and has an elongation of up to 18 percent without failure. Similarly, the cable 14 can withstand the effects of water pressure at full ocean depth without degradation.

[0057] A preferred embodiment of the invention has been described in

considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described, but should be defined by the claims that follow.

Claims

1. An apparatus for transmitting oceanographic data, comprising: a mooring cable including: a data transmission cable configured to transmit the oceanographic data; a reinforcement layer surrounding the data transmission cable; a protective outer jacket surrounding the reinforcement layer; the mooring cable having sections of different densities to provide the mooring cable with an inverse catenary shape, the sections including: a first section defined by the data transmission cable, the reinforcement layer, and the protective outer jacket; a second section connected to the first section and defined by the reinforcement layer and the protective outer jacket, and the second section being configured to sink in sea water; a third section connected to the second section and defined by the reinforcement layer, the protective outer jacket being absent at the third section, and wherein there is a smooth transition in bending stiffness between the protective outer jacket of the second section and the reinforcement layer of the third section; and a fourth section connected to the third section and defined by the reinforcement layer, the protective outer jacket being absent at the fourth section, and the fourth section being configured to float in sea water.

2. The apparatus of claim 1 , wherein the mooring cable further comprises a plurality of machine splices connecting the sections of the mooring cable, each of the machine splices having a length of at least 50 meters to facilitate smooth bending stiffness transitions between the sections of the mooring cable.

3. The apparatus of claim 1 , wherein the mooring cable further includes a strain relief carrot disposed at a connection interface of the second section and the third section to facilitate the smooth transition in bending stiffness.

4. The apparatus of claim 1 , wherein the reinforcement layer forms a single continuous component over the first, second, third, and fourth sections and the protective outer jacket forms a single continuous component over the first and second sections to facilitate smooth bending stiffness transitions between the sections of the mooring cable.

5. The apparatus of claim 1 , wherein the data transmission cable further defines the second, third, and fourth sections of the mooring cable.

6. The apparatus of claim 5, wherein the data transmission cable has a first thickness at the third section and a second thickness at the fourth section, and the second thickness is greater than the first thickness to facilitate smooth bending stiffness transitions between the sections of the mooring cable.

7. An apparatus for transmitting oceanographic data, comprising: an apparatus for transmitting oceanographic data, comprising: a mooring cable including: a data transmission cable configured to transmit the oceanographic data; a reinforcement layer surrounding the data transmission cable; a protective outer jacket surrounding the reinforcement layer; the mooring cable having sections of different densities to provide the mooring cable with an inverse catenary shape, the sections including: a first section defined by the data transmission cable, the reinforcement layer, and the protective outer jacket; a second section connected to the first section and defined by the reinforcement layer and the protective outer jacket, and the second section being configured to sink in sea water; a third section connected to the second section and defined by the reinforcement layer, the protective outer jacket being absent at the third section; and a fourth section connected to the third section and defined by the reinforcement layer, the protective outer jacket being absent at the fourth section, and the reinforcement layer having a specific gravity less than 1.03 at the fourth section such that the fourth section is configured to float in sea water.

8. The apparatus of claim 7, wherein the reinforcement layer has a specific gravity greater than 1.03 at the first section and the second section.

9. The apparatus of claim 7, wherein the data transmission cable further defines the second, third, and fourth sections of the mooring cable.

10. The apparatus of claim 7, wherein the data transmission cable has a

specific gravity greater than 1.03 at the second section to facilitate the tendency of the second section to sink in sea water, and the data transmission cable has a specific gravity less than one at the fourth section to facilitate the tendency of the fourth section to float in sea water.

1 1. An apparatus for transmitting oceanographic data, comprising: a buoy configured to transmit the oceanographic data to a remote receiving station; an anchor configured to be positioned on the sea floor; a mooring cable connecting the buoy and the anchor, the mooring cable having sections of different densities to provide the mooring cable with an inverse catenary shape, the sections including: a first section adjacent the buoy; a second section connected to the first section opposite the buoy, the second section being configured to sink in sea water; a third section connected to the second section opposite the first section; a fourth section connected to the third section opposite the second section and proximate the anchor, the fourth section being configured to float in sea water; the mooring cable further including: a data transmission cable extending from the buoy to the anchor, in part defining the first, second, third, and fourth sections of the mooring cable and being configured to transmit the oceanographic data to the buoy; a reinforcement layer in part defining the first, second, third, and fourth sections of the mooring cable and surrounding the data transmission cable and extending substantially from the buoy to the anchor along the length of the data transmission cable.

12. The apparatus of claim 1 1 , wherein the mooring cable further includes a first protective layer surrounding the reinforcement layer, a fish bite protection layer surrounding the first protective layer, and a second protective layer surrounding the fish bite protection layer.

13. The apparatus of claim 12, wherein the first protective layer is

polytetrafluoroethylene (PTFE) tape, and the second protective layer comprises biaxially-oriented polyethylene terephthalate (BoPET).

14. The apparatus of claim 1 1 , wherein the reinforcement layer includes a braid comprising eight strands of high modulus polyethylene (HMPE) and four strands of liquid crystalline polyester (LCP).

15. The apparatus of claim 12, wherein the mooring cable further comprises a protective outer jacket that surrounds the reinforcement layer along the first and second sections of the data transmission cable and is absent along the third and fourth sections of the data transmission cable to facilitate the inverse catenary shape.

16. The apparatus of claim 15, wherein the protective outer jacket forms a continuous component over the first and second sections of the data transmission cable.

17. The apparatus of claim 15, wherein the protective outer jacket includes strum suppression features to facilitate decreased current drag force.

18. The apparatus of claim 15, wherein the protective jacket comprises a

protective aramid tape along the first section of the data transmission cable.

19. The apparatus of claim 1 1 , wherein the data transmission cable forms a continuous component over the first, second, third, and fourth sections of the mooring cable.

20. The apparatus of claim 1 1 , wherein the data transmission cable comprises: a conducting wire configured to transmit the oceanographic data; and an insulating layer surrounding the conducting wire.

21. The apparatus of claim 20, wherein the insulating layer is a first insulating

layer, and the data transmission cable further comprises a second insulating layer surrounding the first insulating layer along the third and fourth sections of the data transmission cable and being absent along the first and second sections of the data transmission cable to facilitate reduced localized areas of bending and the inverse catenary shape.

22. The apparatus of claim 21 , wherein the first insulating layer comprises polypropylene and the second insulating layer comprises a thermoplastic elastomer.

23. The apparatus of claim 20, wherein the conducting wire comprises: a nylon monofilament core to facilitate elastic elongation; and a plurality of conductive wires configured to transmit the oceanographic data and helically wrapped around the nylon monofilament core.

24. The apparatus of claim 1 1 , wherein the mooring cable further includes a fifth section connected to the fourth section and adjacent the anchor, wherein the fifth section further includes a chaffing-resistant layer surrounding the reinforcement layer proximate the anchor.

25. An apparatus for transmitting oceanographic data, comprising: a mooring cable including: a transmission cable for transmitting something from one end of the mooring cable to the other; a reinforcement layer surrounding the transmission cable; a protective outer jacket surrounding the reinforcement layer; the mooring cable having sections of different densities to provide the mooring cable with an inverse catenary shape, the sections including: a first section defined by the transmission cable, the reinforcement layer, and the protective outer jacket; a second section connected to the first section and defined by the reinforcement layer and the protective outer jacket, and the second section being configured to sink in sea water; a third section connected to the second section and defined by the reinforcement layer, the protective outer jacket being absent at the third section, and wherein there is a smooth transition in bending stiffness between the protective outer jacket of the second section and the reinforcement layer of the third section; and a fourth section connected to the third section and defined by the reinforcement layer, the protective outer jacket being absent at the fourth section, and the fourth section being configured to float in sea water.