Abstract: An offshore system is described that minimizes mooring loads attributable to oscillating wave drift. A tension member (24, FIG. 1), such as a chain, has a lower end (32) fixed to the seafloor and has an upper end portion (40) coupled to the vessel (12), so wave drift that occurs in a storm and urges vessel drift away from a quiescent position, is resisted by tension in the tension member. To reduce the load on the tension member, the vessel is allowed to move while paying out the tension member so it elongates. However, a brake mechanism (70) is applied to the tension member being payed out to slowly pay it out and absorb energy, to thereby damp vessel movement and minimize the maximum mooring load on the tension member. Preferably, at least three tension members (24, 26, 28) extend in different headings from the vessel to fixed locations on the seafloor, so a tension member that is resisting vessel drift extends at a large angle (C) to the vertical.

Abstract: An anchorless boat positioning system dynamically and automatically maintains a boat at a selected anchoring location within water without the use of a conventional anchor by using a steerable thruster whose thrust and steering direction are determined on the basis of position information signals received from global positioning system (GPS) satellites and heading indication signals from a magnetic compass. The anchorless positioning system continuously monitors the position and heading of the boat and compares it with the stored coordinates of the selected anchoring location to generate control signals for the steerable motor.

Abstract: A floating airport that consists of a multiple-deck structure floatingly supported by a plurality of independent hulls removably attached to the underside of the structure. A system of propulsion jets is provided on all sides to permit the motion of the structure in any desired direction relative to the water. The anchoring of the structure is achieved by dynamically monitoring the horizontal position of its center of gravity and by utilizing the propulsion system to avoid any significant movement with respect to a predetermined location. The structure is allowed to rotate approximately around its vertical axis in order to align the runways with the prevailing winds and minimize the winds' impact on its stability, and any translational motion of the center of gravity of the airfield with respect to the water surface is minimized.

Abstract: A submersible thrust producing implement for use in combination with an excavator, the excavator being of the type having a boom and a stick with an attachment end on the stick for attaching the implement, which boom and stick can be extended and retracted to selectively submerge the attachment end to a predetermined location in a body of water, and having a hydraulic power system for actuating the boom, the stick, and the implement.

Abstract: A method of controlling the position of an on-water water curtain device for building a water curtain on the water in order to stop or disperse dangerous gas leaking from a ship or to block flame and radiant heat due to the leaking gas. The method comprises the steps of detecting positions of the ship and the water curtain device, detecting wind direction and tidal current, and adjusting the position of the water curtain device to an optimal position in accordance with detected values so as to maintain the diaster prevention water curtain substantially perpendicular to the leaking gas.

Abstract: Automated constant depth steering and automated yaw correcting techniques for fishing boats or similar craft usable in concert or separately are disclosed. The constant depth steering arrangement controls a relative constant thrust electric trolling motor by varying the orientation of this trolling motor which propels the boat relative to the boat. The constant depth steering arrangement includes operator entry switches and potentiometers for receiving an operator selected water depth and an indication of the direction and sense in which water depth changes. The automatic yaw correcting arrangement includes a rudder-like structure for sensing the lateral component of craft motion relative to the water, and is responsive to the sensed lateral motion to imparting a lateral thrust to the craft in opposition to the sensed lateral component of craft motion.

Abstract: A floating drilling platform having dual work stations is disclosed for performing deep sea drilling and/or hydrocarbon production operations. The structure of the platform is designed to accommodate replaceable modules which facilitate the installation and removal of either a drilling derrick or production equipment. Thus, during the drilling phase of a reservoir's development, the platform may be outfitted with dual drilling derricks while at later times the platform may be outfitted with a drilling derrick and a full production facility. Various expedients are available to permit the equipment of one work station to be used in conjunction with the equipment of one other. Simultaneous management of dual conductors is enabled by a dual riser management system which models in real time riser behavior under varying environmental and other operational conditions. The dual riser management system includes a riser analysis subsystem, a mooring analysis subsystem and a vessel stability analysis subsystem.

Abstract: A vessel wave heading control apparatus is disclosed for use on a floating vessel. Linear acceleration signals from two accelerometers, which sense the rotational acceleration of the vessel due to waves which impact the vessel from a particular direction, are processed by a computer which subsequently produces vessel heading change signals to the steering and propulsion means of the vessel. These signals indicate the required heading and required rate of change of vessel heading necessary to turn the vessel into the direction of the oncoming waves in a timely manner.

Abstract: When the right turn or left turn is set by operating one joystick lever, the bow thrustor arranged on the bow side generates the drift thrust in the rightward or leftward direction in accordance with the turning angular velocity on the basis of the operation of the joystick lever. At the same time, the propellers provided on the stern side are controlled so as to generate the backward thrust proportional to the absolute value of the turning angular velocity of the ship. The forward thrust of the ship which is caused due to the generation of the drift thrust by the bow thrustor is suppressed. Thus, the ship is turned to the right or left around the stern as a rotational center at a predetermined speed with the position of the hull held.

Abstract: An arrangement for spacing a floating body from a mother vessel during borehole-seismic measurements, wherein the floating body includes at least two buoyant bodies connected by a rigid framework and which supports the seismic equipment, the floating body is maintained in a correct position for transmitting seismic pulses by a crane or boom mounted on the mother vessel, a tube or hose system is mounted on the framework for ejecting a pressurized medium, preferably water, against the side of the vessel through nozzles, and the pressurized medium is transferred to the system through a hose coupled to a source of pressurized fluid on board the vessel.

Abstract: Methods and apparatus are provided for temporarily mooring a tension leg platform while the permanent vertical tethering elements thereof are connected between the platform and an anchor located upon the ocean floor.

Abstract: An adaptive riser angle position reference system and method for determining the horizontal position of a marine vessel relative to an underwater wellhead from angular deviations from vertical of a riser between the vessel and the wellhead are disclosed. The system comprises sensors for determining deviation from vertical of the riser at positions proximate the wellhead and the vessel and a compensation filter for adaptively filtering signals indicative of the lower and upper riser angles in accordance with filter coefficients which are determined by riser parameters. The filter coefficients are established by riser parameter identification means which effectively compares riser response, as indicated by the lower and upper riser angles, with the responses of a plurality of riser models, and selects filter coefficients corresponding to the most accurate model.

Abstract: In order to transfer a fluid from a station on the sea bed for a vessel or vice versa, a discharging/loading buoy comprising coupling apparatus for fluid flow is placed in a submerged state and fixed in this state with anchoring apparatus. A vessel is brought and held in position above the buoy by means of dynamic positioning. Then the coupling apparatus for the fluid flow is connected to a coupling section on the vessel.

Abstract: Apparatus for the dynamic positioning of a moving body such as a boat alongside a drilling platform at sea by means of a magnetic field in a plane OXY in which the moving body comprises one or more magnetometers (m.sub.100), and an apparatus for taking bearings on the angle .theta., which a moving reference point O'xy makes with the reference point OXY. The magnetometer (m.sub.100) measures the components of the magnetic field H.sub.x and H.sub.y in the reference point O'xy, a circuit calculates the components of the field H.sub.X an H.sub.Y in the fixed reference point and other circuits determine the position of the moving body. A circuit prepares control signals for the motor of the moving body from the values of H.sub.x an H.sub.y and values X.sub.p and Y.sub.p of the position stored in the memory.

Abstract: A drilling ship is maintained over a deep sea well in a drilling position defined by an inner circle and an outer circle having the well as their center. The ship is connected to a set of anchors fastened to the sea bed and adapted, when the ship is subjected to the action of external forces tending to change its position and of not more than a predetermined magnitude, to restrain the ship from moving beyond the confines of the inner circle. The ship is equipped with a set of adjustable propellers adapted, in conjunction with the anchors, to position the ship within the confines of the outer circle when the external forces acting on the ship to change its position exceed the predetermined magnitude. The operation of the propellers is controlled by a computer to which values are fed which are determined by detectors of the position of the ship and of external forces acting upon it.

Abstract: A pump module adapted to be mounted on the lower end of a compliant pipe extending vertically in a sea for pumping cold water to the upper end thereof to an energy conversion device having means for eliminating torques created by the pump, means for maintaining the pump in axial alignment with the compliant pipe and means for reducing the axial stress of the pump on the compliant pipe.

Abstract: The relative horizontal positions of a floating marine platform and the lower end of a flexible connecting line, such as a cable, drill string, or well bore riser, suspended from the platform are determined by generating angle signals representing the instantaneous vertical slope angles of the connecting line at or near its upper and lower ends, filtering these signals to remove higher order frequencies resulting from variable forcing functions, such as surface wave induced motion of the platform, which produce no net change in the platform position, whereby the filtered angle signals represent the mean terminal slope angles of the envelope of the undulating connecting line, and combining these filtered angle signals in accordance with a predetermined position equation which compensates for phase lag between the sensor measured and true positions of the platform due to the transit time of platform motion induced stress waves or undulations along the connecting line to the lower angle sensor.

Abstract: This invention provides a system which includes winding apparatus for haug in and paying out a substantially inextensible steel rope tethering a floating vessel to a moorage or towing vessel, and a control system responsive to signals indicative of the tension in the steel rope and of the length of rope paid out for controlling the winding apparatus. There is also provided an energy reservoir for receiving and storing energy from the winding apparatus when the rope is paid out. The control system operates such that the tension in the steel rope does not exceed a predetermined value.

Abstract: In order to automatically position a ship which is subjected to external disturbance forces and which is provided with propulsion units arranged to orient the ship in the direction of the resultant of such disturbance forces, there is derived a representation of a control value from the sum of the representations of the actual transverse forces acting on the ship, the control value representation is compared with a representation of a given nominal value, and the control value is brought to zero on the basis of the result of such comparison.

Abstract: A mooring system is disclosed for maintaining a ship shape drilling vessel within alignment limits and for warping it into the sea while drilling a well from the vessel in the sub-surface ground below it. The mooring system absorbs all of the forces on the vessel, such as wind, current, wave, swell, roll, pitch, heave, surge and sway. These forces are measured by sensing load on a motor, electric, hydraulic, and the like, driving the anchor chain wildcat while hauling it in, by sensing load on the brake bands for the windlass wildcats, and by sensing load on the chain stopper, which sensed loads are transmitted to a display device which provides sufficient information to maintain the drilling vessel within the alignment limits and to warp it into the sea to minimize forces and motions of the vessel and to avoid beam sea forces.

Abstract: A boat stabilizer system comprising a pair of nozzles attached permanently or temporarily to a boat to extend beneath the boat adjacent the front and rear so that a pressurized stream of water can be directed through the nozzles in a desired dirction to stabilize the boat against wind and current to prevent drifting.

Abstract: The present invention relates to vessels which are propelled by two or more groups of thrusters and particularly to ships or oil drilling rigs in which it is desired to keep on a particular station. In some circumstances one of the thrusters is found to interfere with the operation of another thruster or to be overloaded when another thruster is not overloaded. The invention provides a method and apparatus for alleviating these problems.

Abstract: This invention provides a system for maintaining hoses and mooring lines extending outwardly from a single buoy mooring terminal, in a desired direction. Also provided is an arrangement for directing the mooring line and hose to move to a ship.

Abstract: A drilling unit is disclosed which incorporates a submersible streamlined hull supporting a streamlined upper hull above the surface of the water by support columns and trusses. The unit is directionally controlled by transverse thrusters and in-line propulsion screws in the submersible hull which are operated by a control system to maintain station keeping over the wellhead at an optimum heading for minimizing the effects of environmental forces such as wind, current and wave action. The control system senses the vessel's heading and surge and sway motions with respect to the wellhead reference and converts this information into error signals. The bow and stern thrusters and in-line propulsion screws are then operated to produce thrust forces which reduce the respective errors. In response to the generation of a stern thrust the control system iteratively calculates a change in the bow target point position on the target circle which will make the stern thrust trend toward zero.

Abstract: For the purpose of controlling the position of an oil rig or other vessel, it is provided with a plurality of steerable thrusters, one pair being located at the bow and one pair at the stern. The two thrusters of each pair are arranged to exert thrust at an angle of 90.degree. so that the net thrust vector may be "steered" merely by controlling the magnitude and direction of thrust of each thruster. By this means it is only necessary to change the directions of the thrust of the thrusters relatively infrequently.

Abstract: The position of a ship moored by at least three anchor ropes extending between the ship and independent remote anchor points is corrected by a control system comprising a rope orientation angle detector, a device for designating the angle and amount of movement of the ship which are necessary to correct the position of the ship, a position correction parameter designating device which determines whether parallel movement or swinging movement is to be made to correct the position of the ship and sends the result of determination to the rope orientation angle detector, a deviation operator which compares the angle of movement with the rope orientation angle for producing an output corresponding to the differential angle, a rope extension and contraction control device responsive to the outputs from the deviation operator and the rope orientation angle detector for producing an output for commanding paying out or taking up of respective anchor ropes, and winches mounted on the ship for operating respective ancho

Abstract: A marine jet drive unit includes a continuously running pump. A reversing gate is positioned partially or wholly within the forward jet to establish a corresponding reverse jet. For neutral drive, the gate is positioned such that the reverse jet just balances the forward jet. A remote shift control unit includes a detent means for locating and holding a rotatable shift lever in neutral. The detent means includes a pair of detent pins carried by a plate which is connected to a support wall by a slot and bolt lost motion connection. The pins are located to opposite sides of the lever and the connection permits angular adjustment about the pivot axis of the lever. The plate supports the detent pin in alignment with a circular outer periphery of the lever plate having oppositely located radial detent grooves. The lever is connected by a push-pull cable to the gate. The precise neutral position of the lever may vary for different drive units.

Abstract: The invention concerns dynamic ballast and stabilization systems for deep-sea applications such as the dynamic anchoring and stabilizing of off-shore platform structures supported by an elongated structure of the type having the lower ends fastened into the floor of a body of water. The system employs a relatively large impellor assembly which generates a downward vertical thrust of sufficient magnitude as to maintain the platform anchored. The structure is designed to absorb shock and movement within a prescribed range to cushion and protect operating equipment. The impellor is enclosed in a movable slinger which can control the lateral direction of the impellor generated thrust such that lateral displacement of the structure is counteracted by the underwater reactive force generated by the impellor. This system includes means for converting the flow of seawater into usable power for driving the system.