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Description and Main Characteristics of the Mining Fleet:

Krypton Ocean Group represents a fleet for deep-sea mining of ferromanganese nodules at the depth of 6,000 meters.

Autonomous underwater vehicle 3

Semi-submersible vessel 1

Ore carrier (“Handysize” DWT 35,000 – 45,000 t bulk carrier) 2

Pusher tug 2

Deck frame structure 1

Length 32 m

Width 24 m

Height 10 m

Loading capacity 300000 kg

Average speed in the nodules collecting mode 1.0 m/s

Maximum submersion depth 6000 m

Regular vessels of the world shipping will be used in the Mining Fleet.

Length overall: 216,75 m

Breadth moulded/max: 43 m

Depth: 13 m

Draft submerged at FPP/APP: 26 m

Summer draft: 9,68 m

Desk space [l x w]: 177,60 x 43,00 m

DWT: 50000 tons

Length: 180 – 185 m

Beam: 30 – 32 m

Draught: 6,2 – 10.2 m

Gross tonnage: 24500 – 25500 tons

DWT: 34500 –45500 tons

Deck frame structure

The deck structure is a block truss structure, installed on a semi-submersible vessel, which ensures a full technological cycle of autonomous mining underwater vehicles.

The deck structure consists of five compartments and a submersible platform.

Compartments 1, 2, and 4 are designed for transportation of autonomous mining vehicles to the mining area. On the main deck of each of the compartments there are retractable thrust arch conductors for fixing the underwater vehicles in a stowed position.

In compartment 1 at the second tier there is a tracking and control station for underwater vehicles to control their working mission. At the third tier of compartment 1 there is a helipad.

Compartment number 4 is located in the working area of the rotary crane and is intended for repair and maintenance of underwater vehicles.

In compartment 3 there is a tank for nodules mined and unloaded from autonomous underwater vehicles. In the lower part of the tank on the main deck of compartment 3 there is an 8-beam unloading facility for delivering nodules to vertical conveyors and further reloading into bulk cargo holds.

In the stern of the deck frame structure there is a submersible platform for maintenance of autonomous underwater vehicles after their ascent to the surface and the end of a full technological production cycle. The platform with the help of 4 hydraulic cylinders is lowered to the level of the bottom part of the underwater vehicle, which is located on the surface after the ascent. With the help of the pusher and the crossoffs, the underwater vehicle is put on the platform to unload the collected nodules. For the centering of the underwater vehicle above the receiving tank there are vertical rotary fenders on both sides of the submersible platform. Unloaded nodules using a plate feeder, vertical and belt conveyor are delivered to the tank located in compartment 3.

During the discharge of nodules a proportional loading of the working fluid (sea water) into the ballast tanks of the underwater vehicle takes place on the submersible platform.

On the submersible platform during the discharge of nodules, the underwater vehicle fuel tanks are refueled with hydrogen and oxygen.

The fuel tanks of the underwater vehicle are refueled from 4 modular containers with hydrogen and oxygen, located on the third tier in the stern of the deck structure.

4 modular containers with hydrogen and oxygen vessels are delivered to the area of mining of ferromanganese nodules, and empty containers are brought to the coastal filling stations by bulk carriers.

On the third tier platform, a swivel crane is installed to reload the containers from bulk carriers.

For mining and, accordingly, loading of one bulk carrier (35,000–45,000 tons deadweight), the fleet of three autonomous underwater vehicles should complete 107-116 diving cycles. For this purpose, six 4-modular containers with hydrogen and oxygen are needed.

Autonomous Underwater Vehicles (general view)

Nodules are mined from the bottom by an autonomous mining vehicle equipped with a nodule collection tool.

The collection tool consists of 3 blocks of rotating rams. In the bow block there are 3 rotating drums. Each of the feed blocks consists of 4 rotating drums. Each of the drums has 22 collection units with 2 rows of L-shaped grips. Each rotating drum has its own separate transportation chain to the receiving bin. The transportation chain consists of a relaod conveyor with a loading hopper, a screw feeder and a transport conveyor. In order to avoid a roll or trim of the underwater vehicle, the nodules are poured from the transport conveyor into the central zone of the storage bin. This ensures consistent and uniform filling.

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Robust housings of the power units and electronics of the autonomous underwater vehicle are designed to accommodate hydrogen cells, frequency converters, device controllers and the main onboard processor keeping them at atmospheric pressure.

Strong housings retain stability under hydrostatic pressure throughout the vehicle immersion.

Robust cases are made of VT22 titanium alloy.

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The fuel tanks of the autonomous underwater vehicle are located in its rear part. Refueling with hydrogen and oxygen is carried out on the ship dock at the time of nodules reloading. Refueling takes place through filler caps of the underwater vehicle, located below its waterline in the surface position. To ensure safety, the refueling is performed in the aft part of the ship-dock from the transitional aft bridge.

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Advances in 3M™ Glass Bubbles Technology

3M™ advances in glass bubbles technology ¹

1 – 3M™ Glass Bubbles for Subsea Insulation and Buoyancy Applications

 

The buoyancy of the autonomous underwater vehicle is provided by blocks filled with a composite paste-like material consisting of hollow glass spheres, industrial oil and paraffin. As hollow glass spheres, 3M’s IM16K glass bubbled are used for underwater buoyancy.

Buoyancy blocks have a density of 650 kg/m³. Polypropylene containers are filled with pasty buoyant material and stacked in each tier in the longitudinal direction between the structural elements of the ballast system. With the help of buoyancy blocks, the vehicle is “even keel” positioned in the surface position, the calculated value of the buoyancy center and the metacentric height of the vehicle are determined.

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The dive-ascent mode, trim control and constant maintenance of the base working horizon of an autonomous underwater vehicle relative to the bottom surface is provided by means of a ballast system.

The ballast system contains three tiers of blocks of high-pressure vessels. The vessels are made from pipe elements connected in series by welding and connecting transition pipes. The blocks of high-pressure vessels within each of the tiers are interconnected according to the vessel combining principle.

Pipe elements and vessel connecting pipes are made of a specialized titanium pseudo-α-alloy of the Ti-Al-V-Mo system with an Al content of not more than 6%; Mo – 2% max. (Figure 1). The alloy has a limit of short-term strength – 1,200 MPa and hardness HB 10-1 = 255 – 270 MPa (Figure 2).

Fig. 1. Marine titanium alloy area

Fig. 2. Titanium alloys yield strengths diagram

The alloy is weldable and can be used to make structures without additional heat treatment.

The total volume of the ballast system is 250 sq.m.

The working fluid of the ballast system is seawater. The working fluid is pumped from the system using submersible plunger high pressure pumps 1.3 T-4/63, produced by the Svesi pump plant (Ukraine).

Submersible brushless DC electric motors manufactured by SME (Submersible Motor Engineering) are used as drives for high-pressure pumps.

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During the dive and ascent of the autonomous underwater vehicle, as well as during its working mission, it is necessary to determine the current coordinates of the vehicle along the depth horizons.

The solution is a miniIPS pressure sensor – Intelligent Pressure Sensor, manufactured by Valeport Ltd.

Operating range, bar up to 600

Accuracy ± 0.01% FS

Resolution 0,001% FS

Selection of indications Continuous, weighted average or data on request

Data transfer rate 1, 2, 4 or 8 Hz, up to 1 time per day

Units of measure The secondary calibration function allows converting dB pressure units to meters

Case material titanium (6,000 m)

Size, mm 40 mm × x 185 (including connector)

Weight in air, kg less than 1

Connector SubConn MCBH6F (titanium) (another connector is available on request)

Interface RS232

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When an autonomous underwater vehicle is immersed, in a vertical position with the trim at the bow at 85° relative to its horizontal surface position, it is necessary to determine the distance to the bottom surface to begin leveling the vehicle on an even keel. The solution is Sonar 837A Delta T600, manufactured by IMAGENEX Technology Corp.

After alignment of the vehicle, this sonar is used to visualize and profile the surface in front of the vehicle and to determine distances to the obstacles that are along its trajectory.

Frequency, kHz 260

Sensor nominal beam width in reception mode 120° х20°

Sensor nominal beam width in transfer mode 120° х20°

Effective horizontal beam width 3°, 1.5°, 0,75°

The number of rays when playing data 120, 240, 480

Range resolution screen 0.2%, output 0.02%

Minimum detectable range 0,5 m

Maximum working depth 6000 m

Frame rate per second 20

Interface to PC standard: 10 Mbit/s Ethernet (10 BASE-T) using TCP / IP

Maximum cable length, m 100

Connection corner connector for 8 conductors (Subconn MCBH8M-Ti)

Power a source of direct current 22-32 V at a power of 5 W

Weight in the air 3.3 kg; in water 1.9 kg

Materials 6AL4V Titanium, epoxy, PVC, titanium connector

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After putting the autonomous underwater vehicle into a flat keel, its horizontal position is determined by the readings of 4 echo sounders located in a square pattern on the bottom of the vehicle (two on the left and right sides). With their help, the vehicle is positioned at the required working distance relative to the bottom surface.

On the basis of information from 4 echo sounders and onboard controller commands using 4 thrusters located in the horizontal plane of the vehicle, the AUV is leveled from a possible roll or trim.

The solution is echo sounders of 852 Echo Sounder 6000 m series, produced by IMAGENEX Technology Corp.

Frequency, kHz 675

Beam width 9° х 9°

Range resolution, mm 20

Minimum detectable range, mm 500

Maximum working depth, m 6000

Maximum cable length, m 1000

Interface RS-232

Connection IE55-1204-BCR

Power 22-30 V DC source at 1.5 W power

Weight in air 0.53 kg, in water 0.34 kg

Materials 6AL4V Titanium, PVC, epoxy resin

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To determine the velocity vector relative to the seabed, as well as the angles of inclination, rotation and yaw of an autonomous underwater vehicle during the mission, LinkQuest Inc.’s NavQuest 600 DVL (Doppler Velocity Log) is used.

Frequency 600 kHz

Accuracy 1% ± 1 mm / s

Height maximum 140 m, minimum 0.3 m

Maximum speed, knots ± 20

Depth standard 800 m, additional 6,000 m

Maximum ping speed 5 / second

Maximum throughput, watts 100

Transmission in low power mode, Watt 28

Receiving, Watt 1

Average power consumption, Watt 2 – 6

Input voltage, Volt 24 ± 2 24 ± 2

Transducer 4 convex rays

Sensor beam angle 22°

Body material anodized aluminum and plastic

Interface RS-232 or RS-422 / ASCII or binary output from 9600 to 115 200 baud

Compass: Accuracy ± 2°

Tilt sensor (pitch and rotation) ± 0.5 ° up to ± 15 °

Temperatures: Accuracy ± 0.4 ° С from -5 ° С to 45 ° С

Weight in the air 9.2 kg, in water 4.2 kg

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The LinkQuest Underwater Acoustic Modem UWM4000 acoustic modem manufactured by LinkQuest Inc. is used to provide wireless communication between the control station on the support vessel and the sensors of the systems and devices of the autonomous underwater vehicle

Data transfer rate RS-232, bits / s 4800

Data transfer rate, bits / s 3200

Acoustic communication, bps 8500

Bit error rate less than 10 ¯⁹

Operating range, m 4000

Maximum depth, m 3,000 or 7,000

Power consumption in transmission mode, watts 7

Power consumption reception mode, watts 0,8

Standby Power Consumption, mW Watts 8

Sensor beam width 70°

Operating frequency, kHz 12,75 - 21,25

RS-232 configuration 9,600 baud, 1 start bit, 1 stop bit, parity bit and flow control

RS-232 input data buffer, kB 900

Voltage, Volt from 12 to 28

Working temperature from -5 ° С to 45 ° С

Storage temperature from -25 ° C to 75 ° C

Full length, mm 286

Diameter of the case, mm 144

Weight in the air 7.6 kg, in the water 4.1 kg

Additional data rate, baud 9600

The modem can communicate with 8 underwater sensors or devices that use the RS-232 interface (Figure 6). The modem can simultaneously display up to 16 analog inputs and provide up to 1 GB of persistent storage on a compact flash disk.

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As an energy source on an autonomous underwater vehicle, FCe ™ 150 hydrogen fuel cells manufactured by US Hybrid are used.

Idling power from 7.5 to 10 kW

Continuous power 130 kW

Peak power 150 kW

System efficiency from 54 to 46% (from 10% to full capacity)

Operating temperature from -40 to 50 ° C

Fuel consumption from 0.8 to 9.6 kg / hour. (10% of total power)

Fuel pressure 1,200 ± 300 kPa

Fuel Type SAE J2719 Hydrogen

Cooling from 59 to 72 ° C (50/50 WEG)

Dimensions (length x width x height) 1,465 x 890 x 506 mm

Weight 474 kg

Start time 30 seconds

Off Time 10 seconds

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In the robust housings of power units and electronics, there are openings for the input of electrical and fiber-optic cables. Water-gas tightness of durable housings at cable entry points is ensured with the help of sealed high-pressure cable connectors.

Sealed Cable Connectors

At the point of contact of cable connectors with the surfaces of robust housings there are radial and end seals. The end seals are compressed with the help of crimp nuts on the inside of strong housings.

Sealed cable connectors withstand a hydrostatic pressure of 1.5 times the pressure at the working depth of the vehicle and retain water-gas tightness in case of damage or rupture of the connecting cable.

Hermetic cable connectors are manufactured by Hydro Bond Engineering Ltd. The company manufactures connectors of various materials for all types of cables for manned and unmanned underwater vehicles.

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Technological Cycle of the Mining Fleet

Transportation of the deck structure and autonomous underwater vehicles to the nodule mining area.

1. In the port, on the deck of the semi-submersible vessel moored by board, special guide runners are installed in the direction perpendicular to the center plane of the vessel. The deck structure is rolled up from the mooring area to the vessel on technological trolleys. With the help of jacks installed in the plane of the transverse bulkheads, the deck structure is lifted to remove the weight load from the carts and to further roll it out to the mooring area. After removing the carts, the jacks are lowered and the deck technological structure is installed on the main deck of the semi-submersible vessel. In the field of supporting pillers, the deck structure is attached to the main deck of the semi-submersible vessel with the help of electric tack welding.

The semi-submersible vessel departs from the mooring area and moves to the port harbor, where it is moored by ropes to floating vertical mooring barrels. The seawater is pumped into the ship’s ballast tanks, and it acquires the maximum draft in a semi-submerged state.

Alternately, pusher tugs approach each of the underwater vehicles, which are located at the mooring area, and abut with bow stops to the stern parts of the vehicles. From the pushing arrows of the pusher tugs, rope slings are put on the fodder protruding brackets. Rope haul ining is done and AUVs are fastened to pusher tugs.

The underwater vehicles are delivered by pusher tugs along the port harbor to the place of mooring of the semi-submersible vessel. In tow mode, the underwater vehicles are in position on an even keel. This is ensured by the injection and distribution of seawater in the ballast system tanks. At this moment the total volume of water in the ballast system is 235 m³.

Underwater vehicles are brought to compartments 1, 2 and 5 of the deck structure. In the zone of operation of the leading arrows of the stern platform, loops of locking cable delays are put on the bow bollards of the vehicle.

The pusher continues to move with the vehicle in the compartment area until the lock delays are fully tensioned. After removing the fixing towing ropes, the drawstrings of the winches are pulled on the stern bollards of the vehicle until tense. After that, the pusher and the underwater vehicle are disjoined.

For centering underwater vehicles in the compartments and to prevent the displacement of underwater vehicles in the horizontal plane during the ascent of the semi-submersible vessel, vertical rouls are installed in each of the compartments.

After installing the underwater vehicles into the compartments, the tugs are pushed into the transport compartment and centered over the technological beds.

After pumping the water from the ballast tanks and the ascent of the semi-submersible vessel, the UVs under the action of gravity are moved onto the floor of the first tier of the deck technological structure, and the tugboats go to the surface of technological beds. On the right and left sides, each of the underwater vehicles is grabbed by a pair of retractable conductors. The conductors are fixed on the slides by a screw stopper. After the underwater vehicles and the tugboats are fixed to the supporting structures, the vessel goes to the ​​nodule mining area.

Vehicle preparation to submersion in the mining area

After the vehicles are delivered to the production area, 235 m³ of water is pumped into the tanks of the ballast systems. The screw stoppers are opened and conductor pairs are separated.

The seawater is pumped into the ballast tanks of the vessel, and it acquires the maximum draft in a semi-submerged state. After the main deck of the vessel is immersed to a depth of 13 meters, under the force of buoyancy, the vehicles and tugboats float.

The pusher approaches the first vehicle and its bow supports touch the stern part of the vehicle. Fixing towing ropes are pulled from the pushing arrows of the pusher to the stern bollards. Rope haul ining is done and the underwater vehicle joins the pusher tug.

The submersible is delivered by the pusher to the submersible platform. In the zone of action of the leading arrows of the stern platform, loops of locking cable delays are put on the bow bollards of the vehicle. The pusher continues to move with the vehicle in the area of the submersible platform until the lock delays are fully tensioned. After removing the fixing towing ropes, the drawstrings of the cargo winches are fixed onto the stern bollards of the vehicle and are put to the tensioned state in contact with the vertical rotators of the platform. After that, the pusher and the underwater vehicle are disjoined. The pusher tug is sent to the compartment area of the deck structure for the delivery of the next vehicle.

After fixing the underwater vehicle above the submersible platform in a horizontal plane, the filling hoses are fed to the stern of the vehicle by the crane. The underwater vehicle is filled with hydrogen and oxygen.

After refueling, a loading frame with collet grips is approaching the vehicle. Collet grips are mounted on mating parts on the underwater vehicle. Crane slings are hauled in and the vehicles are fixed in a vertical plane.

First vehicle operation stage

During the first stage, 15 m³ of seawater is pumped into the ballast system. This operation provides the necessary amount of negative buoyancy and the calculated trim to ensure the optimal dive speed of the underwater vehicle.

After the ballast system is completely filled, the vehicle turns into negative buoyancy and the crane puts it down to the depth below the bottom of the vessel and is held in a vertical plane by collet grips.

Collet grips are opened simultaneously and the underwater vehicle dives, to perform the first cycle of its working mission.

During the dive, the underwater vehicle rotates about its transverse axis Y in the fixed coordinate system associated with the carrier ship, gradually creating a trim on the bow and submerging. The maximum calculated trim angle after pumping 15 m³ of water in is 85°.

Second vehicle operation stage

1. During the second stage, the vehicle is immersed in a vertical position — at 85° relative to its horizontal surface position. The vehicle immerses under the force of gravity, created by negative buoyancy. No additional forces are created by propulsion during the vehicle immersion. The underwater vehicle position during the dive is determined by a pressure sensor. The information from the pressure sensor is transmitted through the onboard controller and the acoustic modem to the monitor at the control station on the support vessel.

2. The distance from the current position of the vehicle during the dive to the bottom is determined using a front-view sonar located in the bow of the underwater vehicle. The distance to the bottom surface is determined by the AO slanting line (5° from the vertical when diving by the bow at 85°) and recalculated to the OB distance vertically from the vehicle bow to the bottom surface. This operation is necessary in order to determine with sufficient accuracy the distance from the bottom surface to the depth horizon, where the vehicle should begin to turn to an even keel. The information from the front-view sonar is transmitted via the on-board controller and the acoustic modem to the monitor at the control station on the support vessel.

Third vehicle operation stage

During the third stage, 15 m³ of water is pumped out of the ballast system and the underwater vehicle turns onto the even keel. When this occurs, the underwater vehicle is rotating relative to its transverse axis Y in a fixed coordinate system. This operation begins when the AUV reaches a point at 660 meters from the bottom surface. Within 6 minutes the water pumping starts. During this time, the vehicle is immersed to the horizon at 110 meters from the bottom surface. The vehicle even position will be proved by 4 echo sounders, which, after the vehicle is on an even keel, will determine the distance from the the vehicle underside to the seabed.

The information from 4 echo sounders is transmitted through the onboard controller and the acoustic modem to the monitor at the control station on the support vessel.

  1. If for some reason the water is not pumped out of the ballast system and the vehicle does not level, the autonomous emergency ballast system is started and solid ballast is discharged.
  2. This operation is necessary in order to avoid collision and introduction of the vehicle into the bottom ground. The control of sensors and actuators of the autonomous ballast system is carried out by the operator from the tracking and control station through the acoustic modem.

Fourth vehicle operation stage

During the fourth stage, the vehicle in the position on an even keel from a horizon of 110 meters relative to the bottom surface moves to the required working distance of 4.0 meters relative to the seabed. This movement is carried out with the help of 4 thrusters located in vertical cylindrical channels on the right and left sides. At the same time, the change in the distance to the bottom surface is determined by 4 echo sounders located in the bottom of the vehicle. At the time when the vehicle is at 1.0 meter from the bottom surface, marching propulsion units are turned on. The vehicle position vertically relative to the bottom surface is determined by 4 echo sounders.

The vehicle begins to move in a horizontal plane at a speed of 1 m/s. The speed of the vehicle relative to the bottom surface is determined by the Doppler Velocity Log. After the beginning of its movement in the horizontal plane, the sliding frames of the nodule collection tool are set in motion. Drums with trays located on sliding frames move down in a vertical plane in the direction of the bottom surface. After lowering the drums at a distance of 2.0 m from the vehicle underside, the drums rotation engine is started. After the drums started rotating, the speed of the vehicle relative to the bottom, determined by the Doppler Velocity Log, and the angular velocity of drums rotation are synchronized. After synchronization of the speed of the vehicle in the horizontal plane and the angular velocity of drums rotation, the drums are lowered to a distance of 4 m from the vehicle underside. The movement of the frames in the vertical plane is determined by the linear displacement sensors, which are located on the racks of the sliding frames.

After extending the collection tools to a working distance of 4.0 m from the vehicle underside, the grips of the bottom surface touch the seabed ground (Table below, Pos. A).

Grips touching the bottom

By the mass of the collection tool and the chain sagging, the grips are introduced into the ground to a depth of 60 mm (Table below, Pos. B).

Grips introduction into the ground

After penetration into the ground, the grips close, by turning from the vertical to the horizontal position (Table, pos. C).

Grips shutting and extraction of nodules

The sheme of grips introduction into the ground and extraction of nodules.

The recovered nodules are held by the grips, turned into a horizontal position. The grips are shut using gear mechanisms and hydraulic cylinders located on the inner surface of the collection tools.

Buoyancy control of the autonomous underwater vehicle in the nodule collection mode.

During the working mission of the autonomous underwater vehicle (Figure 1), it is necessary to control its buoyancy and constantly maintain the base working horizon of the vehicle relative to the bottom surface.

1 – nodule collection tool; 2 – echo sounders; 3 – vertical thrusters; 4 – tank; 5 – high pressure pumps; 6 – ballast system capacity; 7 – marching propulsion

At the basic working horizon, the vehicle is in zero-buoyancy mode. Nodules collected by the collection tool (1) and brought to the tank (4) of the underwater vehicle, create a negative buoyancy for the underwater vehicle. At this moment the force of the weight of the underwater vehicle G exceeds the force of maintaining the vehicle at B = γ V.

where γ is the density of water in the working horizon;

V is the volume of all displacement parts of the vehicle.

The echo sounders (2), located in the bottom part, record the change in the position of the underwater vehicle relative to the bottom surface. The vehicle starts moving down in a vertical plane. The signals from the echo sounders arrive at the central onboard controller of the underwater vehicle. The central controller includes a group of high-pressure pumps (5). The water is pumped out of the AUV ballast system tanks. By pumping the water out, the difference between the weight of the vehicle G and the force of B is balanced. Any fluctuations of the forces G and B in the process of balancing them are overcome by the stops of the thrusters (3) located in the vertical cylindrical channels of the left and right sides of the underwater vehicle. This ensures the continuous maintenance of the basic working horizon of the underwater vehicle. With the help of thrust P, it is possible to overcome the force of resistance to the movement of R in the vertical plane.

Depending on the relationship between the weight of the vehicle and its supporting force, the buoyancy force p, representing the difference of forces G – B, may be greater or less than zero (Figures 2 and 3), or equal to zero.

G ˃ B, p = G – B

B ˃ G, p = B – G

If the screws in the vertical channels operate to lift the vehicle at a negative buoyancy, the onboard controller determines the thrust for vertical thrusters P = R + p. At the same time, if the screws in the vertical channels operate to lift the vehicle at a positive buoyancy, the onboard controller reduces the thrust for the vertical thrusters by P = R – p. If the screws in the vertical channels work to lift the vehicle at zero buoyancy (for example, when avoiding obstacles in the vertical plane), then the onboard controller determines the thrust for the vertical thrusters P = R.

If the vehicle has short-term positive buoyancy when performing the working mission, the pumping of water from the ballast system tanks stops and the screws in the vertical channels work to lower the vehicle. In this case, the onboard controller determines thrust P = R + (B – G) for vertical thrusters.

When the collection tools are filled with nodules, there is a maximum difference between the weight of the vehicle G and the sustaining force B. In this case, the vehicle will move downward from the base working horizon to the bottom surface. This movement can occur at a roll or trim. The vehicle is turned to zero buoyancy and an even keel by the maximum thrust of the vertical thrusters (3) and by pumping the water from the ballast system tanks (6) in the maximum performance mode. The screws in the vertical channels work to lift the vehicle and in the mode of maximum thrust, the collection tools are lifted from the bottom surface, and the vehicle moves to the point exceeding its basic working horizon. The water is pumped out of the ballast system until the moment of the vehicle zero-buoyancy. The vehicle “hangs” and turns to an even keel. After that, using the propulsion units (7), the vehicle moves in a horizontal plane, and the vehicle speed relative to the bottom and the angular velocity of rotation of the nodule collection tool are synchronized. After synchronization of the speed of the vehicle in the horizontal plane and the angular velocity of rotation of the nodule collection tool, the vehicle moves down in the vertical plane at zero buoyancy using thrusters. The downward movement of the vehicle in the vertical plane takes place until the collection tool touches the ground and then the nodule collection process resumes.

The vehicle mines 300 tons of nodules in one dive. And accordingly, 220 m³ of ballast water is to be pumped out of the ballast system.

When working at the bottom surface, the velocity vector relative to the seabed is determined by the Doppler Velocity Log, as well as the angles of inclination, rotation and yaw. Using the Doppler Velocity Log, the vehicle speed is constantly and continuously controlled and the angular velocity of the drum rotation is synchronized with the speed of displacement by the vehicle in the horizontal plane. Possible obstacles along the trajectory of the underwater vehicle are tracked by a front-view sonar. Using the sonar, the surface in front of the vehicle is visualized and profiled. The information from the sonar is recorded on theprocessor hard disk, which is located in the casing of the underwater vehicle. To bypass obstacles, confront lateral drift (drift) and keep the vehicle on the course in the horizontal plane, the thrusters located in the channels in the forward part of the vehicle are used.

Fifth vehicle operation stage

During the fifth stage, the vehicle turns to a positive buoyancy. This is achieved by pumping the remaining amount of liquid of 15 m³ from the ballast system.

After the vehicle turns to a positive buoyancy, its ascent begins. The vehicle is ascending by positive buoyancy.

Any current position of the underwater vehicle in the depth horizons during its ascent are determined by a pressure sensor. Information from the pressure sensor is transmitted through the onboard controller and the acoustic modem to the monitor at the control statiton on the support vessel.

If, for any reason, the vehicle does not ascend, it turns on the emergency discharge of the collected nodules from the tank of the underwater vehicle. The nodules are discharged through the hatch located under the tank in the bottom part of the vehicle. The sensors and actuators of the nodule discharge hatch are controlled by the operator from the tracking and control station through the acoustic modem.

If for some reason the collected nodules are not discharged from the tank of the underwater vehicle and the vehicle does not ascend, the autonomous emergency system is activated and solid ballast is discharged. The sensors and actuators of the autonomous ballast system are controlled by the operator from the tracking and control station of the underwater vehicle through the acoustic modem.

Sixth vehicle operation stage

After surfacing, the underwater vehicle is in its surface position with trim at the stern. The water is pumped into its bow ballast tank. After the vehicle turns onto an even keel, the pusher approaches it and rests against the bow of the vehicle. Fixing tow ropes are wound from the belaying booms of the pusher to the stern bollards of the vehicle. The ropes are hauled in and the underwater vehicle joins with the pusher tug. The vehicle is delivered by the pusher to the submersible platform.

On the submersible platform, the intake hopper is moving forward.

In the zone of operation of the belaying booms of the stern platform, loops of fixing guy ropes are put on the bow bollards of the vehicle. The pusher continues moving with the vehicle in the area of the submersible platform until the guy ropes are fully tensioned.

After removing the fixing ropes, the guys of load hoists are belayed onto the stern bollards of the vehicle and hauled in until tense and in contact with the vertical rotating boat fenders of the platform.

After that, the pusher and the underwater vehicle are disjoined. The pusher leaves for the mooring area.

As soon as the protruding hooks of the vehicle get into the zone of operation of the belaying arms of the stern platform, they are pulled into the loops of the guy ropes and hauled in until tense. The pusher and the underwater vehicle are disjoined. The pusher moors to the side of the semi-submersible vessel, and the underwater vehicle is pulled to the stern platform by mooring winches. The ropes are hauled in by mooring winches until the underwater vehicle’s hull is in contact with vertical rotating fenders. In this case, the vehicle is in a floating state and does not rely on a submersible platform.

After fixing the underwater vehicle above the submersible platform in a horizontal plane, the loading frame with two-piece grippers is delivered to the vehicle by the rotary crane of the deck structure. The grippers are attached to mates on the underwater vehicle. The crane slings are hauled in and the vehicles is fixed in a vertical plane above the receiving hopper.

The hatch in the bottom part of the vehicle opens and the nodules are unloaded into the receiving hopper. The nodules from the receiving hopper through plate feeders and vertical conveyors are reloaded to belt conveyors of the left and right side. Belt conveyors deliver the nodules to the transshipment tank. During the discharge of nodules, 235 m³ of water is charged into the ballast tanks of the underwater vehicle. At the same time, the fuel tanks of the underwater vehicle are filled with hydrogen and oxygen.

The design of the submersible platform provides for the possibility to unload the underwater vehicles both on the surface and in a semi-submerged state of the supporting vessel.

After unloading the nodules and filling 235 m³ of water into the ballast tanks, the vehicle turns to a positive buoyancy. The ropes are paid out by mooring winches and the vehicle is unfixed in the horizontal plane.

For immersion and the start of the second cycle, 15 m³ of water is pumped into the ballast tanks. The vehicle turns to a negative buoyancy and is held in a vertical plane by the two-piece grippers of the frieght frame.

The two-piece grippers are simultaneously opened and the underwater vehicle performs the diving, leaving for the second cycle of its working mission.

To perform the planned annual production of about 1,000,000 tons, three autonomous underwater vehicles should be used. The time of the full working cycle of one underwater vehicle is 4 hours. This time is distributed as follows: one hour is used for diving, one for collecting nodules, one for ascending, and one for unloading the collected nodules and filling the vehicle with hydrogen and oxygen.

When one vehicle is submerged and another vehicle ascends, the vehicles may be drifted, approach each other or their routes may intersect. To avoid this, the surfacing vehicle activates its propulsion system and the vehicles are diverged to a safe distance from each other at the planned depth horizon.

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