METHOD AND APPARATUS FOR A BUOYANCY VESSEL FOR DEEP-SEA MINING

Abstract

A buoyancy system for an underwater autonomous vehicle is provided. The buoyancy system includes one or more pressure vessels, a primary pump connected to each of the one or more pressure vessels with the primary pump configured to pump liquid from the one or more pressure vessels. The buoyancy system further includes a controller communicatively coupled to the primary pump and configured to operate the main pump, and a power source configured to provide power to the controller and the primary pump. Each pressure vessel includes a cylindrical shell with an inner surface, spaced apart axial support members disposed on the inner surface of the cylindrical shell, and radial support plates between the axial support members.

Claims

1. A buoyancy system for an underwater autonomous vehicle, the buoyancy system comprises: one or more pressure vessels, each pressure vessel comprising: a cylindrical shell; spaced apart axial support members disposed on an inner surface of the cylindrical shell; and radial support plates between the axial support members; a primary pump connected to each of the one or more pressure vessels, wherein the primary pump is configured to pump liquid out of the one or more pressure vessels during operation of the buoyancy system; a controller communicatively coupled to the primary pump and configured to operate the main pump; and a power source configured to provide power to the controller and the primary pump.

2. The buoyancy system of claim 1, further comprising: a first pump connected to each of the one or more pressure vessels via a liquid inlet valve, the first pump configured to pump liquid into each of the one or more pressure vessels when commanded by the controller; and a second pump connected to each of the one or more pressure vessels via a gas inlet valve, the second pump configured to pump in gas to each of the one or more pressure vessels when commanded by the controller.

3. The buoyancy system of claim 1, wherein a volume of a liquid within each of the one or more pressure vessels is independently controlled via operation of the primary pump.

4. The buoyancy system of claim 1, wherein the axial support members are disposed lengthwise the cylindrical shell and the radial support plates are disposed on a circumference of the cylindrical shell.

5. The buoyancy system of claim 1, wherein the one or more vessels contain a first volume of a liquid and a second volume of a gas at a ratio adjusted by operation of the primary pump.

6. The buoyancy system of claim 5, wherein the liquid is at least one of sea water, filtered sea water, desalinated water, or de-ionized water and the gas is at least one of air or filtered air.

7. The buoyancy system of claim 1, wherein the axial support members and the radial support plates comprise aluminum.

8. The buoyancy system of claim 1, wherein the axial support members are metal extrusions with a hexagonal cross section.

9. The buoyancy system of claim 1, wherein the primary pump is a high-pressure hydraulic piston pump with a pumping rate proportional to a payload collection rate of the underwater autonomous vehicle so that for every net kilogram of payload collected by the underwater autonomous vehicle, an equal mass of liquid is pumped out of the one or more pressure vessels.

10. The buoyancy system of claim 1, wherein the buoyancy system is configured to operate at underwater depths between about 5 km and about 6 km.

11. A deep-sea mining system, the system comprising: a dynamic buoyancy system with one or more pressure vessels connected to one or more primary pumps, wherein the one or more pressure vessels comprise: a cylindrical shell; spaced apart axial support members covering a portion of an inner surface of the cylindrical shell; and radial support plates between the axial support members; an autonomous underwater vehicle; and an ore collection system; wherein the dynamic buoyancy system is configured to dynamically control a buoyancy of the deep-sea mining system by adjusting via the one or more primary pumps a ratio of a gas volume to a liquid volume contained in the one or more pressure vessels.

12. The system of claim 11, wherein the axial support members are disposed lengthwise the cylindrical shell and the radial support plates are disposed along a circumference of the cylindrical shell.

13. The system of claim 12, wherein multiple rows of radial support plates are disposed along a height of the cylindrical shell.

14. The system of claim 13, wherein a spacing between two adjacent rows of radial support plates is about 25 mm.

15. The system of claim 11, wherein the radial support plates have a thickness of about 4 mm.

16. The system of claim 11, wherein the one or more primary pumps have a combined output of about 500 kW or about 670 hp.

17. The system of claim 11, wherein the dynamic buoyancy system further comprises: a controller communicatively coupled to the one or more primary pumps and configured to operate the one or more main pumps; and a power source configured to provide power to the controller and the one or more primary pumps.

18. The system of claim 11, wherein the liquid volume is at least one of sea water, filtered sea water, desalinated water, or de-ionized water and the gas volume is at least one of air or filtered air.

19. The system of claim 17, wherein the dynamic buoyancy system further comprises: a first pump connected to each of the one or more pressure vessels via a liquid inlet valve, the first pump configured to pump liquid into each of the one or more pressure vessels when commanded by the controller; and a second pump connected to each of the one or more pressure vessels via a gas inlet valve, the second pump configured to pump gas to each of the one or more pressure vessels when commanded by the controller.

20. The system of claim 11, wherein the one or more primary pumps are high-pressure hydraulic piston pumps with a combined pumping rate proportional to a payload collection rate of the deep-sea mining system so that for every net kilogram of payload collected, an equal mass of liquid is pumped out of the one or more pressure vessels.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying figures, which are included as part of the present specification, illustrate the presently preferred embodiments and together with the general description given above and the detailed description of the preferred embodiments given below serve to explain and teach the principles described herein.

[0008] FIG. 1 illustrates an exemplary deep-sea mining system, in accordance with some embodiments.

[0009] FIG. 2 illustrates a dynamic buoyancy system implemented in a deep-sea mining system, in accordance with some embodiments.

[0010] FIG. 3 describes the operation of a dynamic buoyancy system as implemented in a deep-sea mining system, in accordance with some embodiments.

[0011] FIG. 4 is an exemplary arrangement of a dynamic buoyancy system with multiple pressure vessels forming respective dynamic buoyancy sub-systems as implemented in a deep-sea mining system, in accordance with some embodiments.

[0012] FIG. 5 is a top view of an array of dynamic buoyancy sub-systems as implemented in a deep-sea mining system, in accordance with some embodiments.

[0013] FIG. 6 is an isometric view of a pressure vessel of a dynamic buoyancy system as implemented in a deep-sea mining system, in accordance with some embodiments.

DETAILED DESCRIPTION

[0014] FIG. 1 illustrates an exemplary deep-sea mining system 100 deployed from a mining ship 110 to collect ore nodules 120 disposed on the seabed, according to some embodiments. Deep-sea mining system 100 descents at the vicinity of the seabed and hovers over the seabed during the ore collection process. In some embodiments, deep-sea mining system 100 includes an underwater autonomous vehicle (UAV) 130, an ore collection system 140 that collects ore nodules 120 form the seabed, a payload hopper 150 for temporarily storing the collected ores, and a dynamic buoyancy system 160 that enables the deep-sea mining system 100 to maneuver primarily in a vertical direction (e.g., to descend from the sea surface to the seabed and ascend from the seabed to the sea surface).

[0015] According to some embodiments, UAV 130 is equipped with thrusters (not shown in FIG. 1) that enable deep-sea mining system 100 to maneuver primarily in a lateral direction (e.g., parallel to the seabed—along the x-y plane) and secondarily in the vertical direction (e.g., along the z-direction). By way of example and not limitation, ore collection system 140 can be equipped with one or more robotic arms 140a that may extend towards the seabed and reach for the ore nodules. In some embodiments the robotic arms 140a can harvest the ore nodules by picking them up as the deep-sea mining system 100 hovers over the seabed, and dispose them into payload hopper 130 via a conveyer belt, a suction system, or any other suitable means, methods, or techniques.

[0016] According to some embodiments, deep-sea mining system 100 uses underwater surveying and inspection systems to identify the position of the ore nodules 120 on the seabed and to determine whether marine life is anchored on the nodules. By way of example and not limitation, deep-sea mining system 100 may be configured to avoid collecting ore nodules having marine life anchored on them. Once the payload hoper 150 is full, the dynamic buoyancy system 160 enables the deep-sea mining system 100 to ascent to the sea surface and deliver its payload.

[0017] According to some embodiments, the components of deep-sea mining system 100 (e.g., dynamic buoyancy system 160, payload hopper 150, ore collection system 140, and UAV 130) operate in synergy. In some embodiments, these components may be either integrated in a housing or operated as detachable modules physically and communicatively connected to one another. According to some embodiments, dynamic buoyancy system 160, payload hopper 150, ore collection system 140, and UAV 130 are physically attached to one another during the collection/mining process, and at least the payload hopper 150 and the dynamic buoyancy system 160 can be physically attached to one another during the mining and ascending process. In some embodiments, the dynamic buoyancy system 160 can provide the necessary buoyancy to compensate for the collected ores during the mining process and the ascent of at least the payload hopper 150 or of the entire deep-sea mining system 100. In some embodiments, if the dynamic buoyancy system 160 and the payload hopper 150 ascent on their own to the ocean surface, UAV 130 may provide with its thrusters the necessary buoyancy to deep-sea mining system 100 until the dynamic buoyancy system 160 and the payload hopper 150 descend again from the sea surface to re-attach to the deep-sea mining system 100.

[0018] In some embodiments, deep-sea mining system 100 can include additional components, modules, and systems necessary for its operation. These additional components, modules, and systems are not shown in FIG. 1 for simplicity. By way of example and not limitation, these additional components, modules, and systems may include cables, one or more onboard computers, electronic equipment, additional thrusters, motors, batteries, communication equipment, cameras, radars, controllers, global positioning systems, and the like. These additional components, modules, and systems are within the limit and the scope of this disclosure. In some embodiments, deep-sea mining system 100 may operate under autonomous mode, semi-automatic mode, manual mode, or combinations thereof based on instructions from mining ship 110. In yet another embodiment, deep-sea mining system 100 may be communicatively coupled and physically connected to mining ship 110 via ropes, cables, and the like.

[0019] Details of the dynamic buoyancy system 160 are shown in FIG. 2, according to some embodiments. As shown in FIG. 2, dynamic buoyancy system 160 includes a pressure vessel 200, a buoyancy foam 210, a primary pump 220, a controller 230 capable of receiving and transmitting data, and a power source 240 with a charge port 240a. According to some embodiments, all the components in dynamic buoyancy system 160 are designed to operate at ocean depths between about 5 km and 6 km. However, this is not limiting and dynamic buoyancy system 160 may be configured to operate at larger or lower depths. In some embodiments, the pressure vessel volume can be selected based on the mineral payload weight target. For example, larger payload weights require a higher pressure vessel volume than lower payload weights.

[0020] Pressure vessel 200, as shown in FIG. 2, contains both a compressible gas (e.g., air, filtered air, or another suitable gas or mixture of gasses), and an incompressible liquid (e.g., sea water, filtered sea water, desalinated water, de-ionized water, or another suitable liquid) shaded gray. In some embodiments, dynamic buoyancy system 160 may include one or more secondary pumps in addition to primary pump 220. For example, an optional gas pump 250 for gas pressurization may attach to a valve 260 to pre-fill the pressure vessel 200 with compressible gas at the sea surface. According to some embodiments, valve 260 may allow the gas to enter pressure vessel 200 and prevent the liquid and the gas from escaping pressure vessel 200. Additionally, valve 260 may prevent sea water from entering pressure vessel 200 when the dynamic buoyancy system 160 is at mining depth (e.g., at a depth between 5 km and 6 km). The term “optional” as used herein is intended to mean that gas pump 250 may or may not be attached to pressure vessel 200 (e.g., via valve 260) at all times. For example, gas pump 250 may be located on mining ship 110 and may connect to pressure vessel 200 via valve 260 while buoyancy system 160 is at the sea surface, and subsequently disconnect from pressure vessel 200 when buoyancy system 160 is ready to descend. In another example, gas pump 250 may remain attached to pressure vessel 200 via valve 260 during the descent and mining process (e.g., at all times). In some examples, a low-pressure sub-sea liquid pump 270 may be affixed to a valve 280 to pump incompressible liquid into pressure vessel 200 at the sea surface. In some embodiments, sub-sea liquid pump 270 may introduce liquid into pressure vessel 200 during the decent or during the mining process as discussed later in connection to FIG. 3. By way of example and not limitation, sub-sea liquid pump 270 is capable of proving gas at a pressure of about 200 psi.

[0021] In some embodiments, primary pump 220 is a high-pressure, low-volume (HPLV) pump intended to pump the incompressible liquid from the pressure vessel 200 (e.g., via valve 290) at a depth corresponding to a surrounding sea water pressure of about 600 bars. In some embodiments, the primary pump 220 can be a high-power output pump (e.g., with about 300 hp or about 224 kW of output power) with a pump rate that can match the ore collection rate. In some embodiments, the primary pump 220 can be a high-efficiency piston pump, such as a high-pressure hydraulic piston pump. By way of example and not limitation, the pump rate of primary pump 220 can be at least 4 liters/sec and proportional to the ore collection rate so that for every net kilogram of ore collected, a kilogram of liquid is pumped out of the pressure vessel 200. By way of example and not limitation, primary pump 220 can be single or multi-stage pump.

[0022] The pumps described above can be powered by a rechargeable power source 240 which can be charged via charging port 240a when dynamic buoyancy system 160 in at the sea surface. According to one embodiments, power source 240 can be a 400 kWh rechargeable battery. By way of example and not limitation, power source 240 can be a Lithium Iron Phosphate (LiFePO.sub.4) battery. However, any suitable rechargeable battery may be used based on the desirable cycle durability and energy density requirements. According to some embodiments the rechargeable power source 240 is not insulated and heat generated by rechargeable power source 240 is dissipated into the water.

[0023] According to some embodiments, the deep-sea mining system 100 shown in FIG. 1 can estimate its ore collection rate by measuring, for example, the mass of the collected ores in payload hopper 150 via its instrumentation. In response, dynamic buoyancy system 160 may use the collection rate estimate to adjust the buoyancy of deep-sea mining system 100. At the same time, and if required, UAV 130 can activate its thrusters to keep the deep-sea mining system 100 within operating distance from the sea floor (e.g., within the reach of robotic arms 140a). In some embodiments, the total thrust from UAV 130 can be fed forward to the dynamic buoyancy system 160 so that dynamic buoyancy system 160 can adjust the buoyancy of deep-sea mining system 100 to reduce the total vertical thrust compensation from UAV 130.

[0024] In referring to FIG. 2, controller 230 can be configured to receive instrumentation readings—such as pressures readings, temperature readings, volume readings, mass readings, collection rates and other types of rates, etc.—of the deep-sea mining system 100. Controller 230 may also be configured to receive/transmit data within, to and from the dynamic buoyancy system 160, and operate the pumps (e.g., gas pump 250 and sub-sea liquid pump 270) and the valves (e.g., valves 260, 280, and 290) in response to weight changes caused by the ore collection process. In further embodiments, controller 230 may include a standard processing device, such as a single-board computer like a Raspberry Pi, or an ARM processor.

[0025] According to some embodiments, dynamic buoyancy system 160 is further equipped with sensors (not shown in FIG. 2) to constantly monitor the pressure inside pressure vessel 200, the flow rate of the liquid through the pipelines, the temperature of controller 230, the temperature of the pumps (e.g., gas pump 250 and sub-sea liquid pump 270), and the temperature of power source 240.

[0026] In some embodiments, buoyancy foam 210 can provide static buoyancy to compensate for the mass of dynamic buoyancy system 160 so that the dynamic buoyancy system 160 itself is neutrally buoyant when deep-sea mining system 100 is at the target depth (e.g., at a depth between about 5 km and 6 km). By way of example and not limitation, buoyancy foam 210 can be a syntactic foam—e.g., hollow glass microspheres (microballoons) cast in resin. Adding buoyancy foam to the dynamic buoyancy system 160 increases the buoyancy. Neutral buoyancy can be achieved by adding enough buoyancy foam 210 so that the upward force due to the water displacement caused by buoyancy foam 210 and pressure vessel 200 compensates for the mass of the dynamic buoyancy system 160.

[0027] In other embodiments, the deep-sea mining system 100 can include a buoyancy system that features more than one (e.g., multiple) pressure vessels 200 as shown by way of example and not limitation in FIG. 4. In the exemplary configuration of FIG. 4, the pressure vessels 200 can be connected, via a central manifold 400, to a single pump 220 and controller 230 pair. Additionally, each of the pressure vessels 200 can be equipped with its own valves 260, 280, and 290, with each valve 290 being connected to the central manifold 400. In FIG. 4, gas pumps 250, sub-sea liquid pumps, and buoyancy foams 210 are omitted for simplicity. According to some embodiments, each pressure vessel 200 connected to the common primary pump 220 and controller 230 pair forms a dynamic buoyancy sub-system 400.

[0028] By way of example, the deep-sea mining system 100, may be equipped with a buoyancy system having an array of 21 pressure vessels 200, each pressure vessel 200 forming a dynamic buoyancy sub-system 400 arranged in 3×7 array as shown in FIG. 5, which is a top view of deep-sea mining system 100 shown in FIG. 1 along line A-B. In some embodiments, each dynamic buoyancy sub-system 400 in FIGS. 4 and 5 can be independently controlled via its valves 260, 280, and 290. It is to be appreciated that fewer or additional buoyancy systems 400 (e.g., fewer or more than 21) may be used in any suitable configuration depending on the dimensions of deep-sea mining system 100 and the payload weight that the deep-sea mining system 100 is required to carry. That is to say, the configurations shown in FIGS. 4 and 5 are not limiting and merely provide one of many possible examples and configurations. Therefore, additional configurations and permutations, besides the ones shown in FIGS. 4 and 5, are possible and within the spirit and the scope of the disclosure.

[0029] With multiple dynamic buoyancy systems, as discussed above, the deep-sea mining system 100 can compensate for the uneven distribution of ore nodules in payload hoper 150. For example, uneven loading may occur when the ore nodules are not evenly distributed in payload hoper 150 (e.g., more ores may accumulate on one side of payload hoper 150). If a single dynamic buoyancy system was used in an uneven loading scenario, the thrusters of UAV 130 located on the heavy side would have to work continuously to keep deep-sea mining system 100 leveled. In contrast, and by using an array of dynamic buoyancy systems (e.g., an array of dynamic buoyancy systems 400 as discussed above), buoyancy can be adjusted by operating the dynamic buoyancy systems 400 located on the heavy side so that deep-sea mining system 100 remains leveled without the need for corrective action from the thrusters of UAV 130.

[0030] Another benefit of using multiple dynamic buoyancy systems is operational redundancy. For example, in the event that one of the dynamic buoyancy systems fails, another dynamic buoyancy system may be activated so that deep-sea mining system 100 can continue to operate without disruptions.

[0031] According to some embodiments, the dynamic buoyancy system (e.g., dynamic buoyancy system 160 or each of the dynamic buoyancy systems 400) responds to data communications form other modules and dynamically adjusts the buoyancy by pumping liquid in and out of its pressure vessel 200 to meet the motion objectives of deep-sea mining system 100. According to some embodiments, the dynamic buoyancy system can communicate with UAV 130, which can request a buoyancy rate adjustment based on the thrust vector requirements so that deep-sea mining system 100 maintains its distance from the seabed. The term “thrust vector” as used herein refers to the combined force acting on the deep-sea mining system 100 at any given moment and includes the vertical buoyancy forces applied by the one or more dynamic buoyancy systems and the horizontal and/or vertical forces applied by the thrusters of UAV 130. Additionally, the dynamic buoyancy system can communicate with the ore collection system 140, which, based on its perceived ore mass collection rate, can request that the buoyancy is adjusted to maintain deep-sea mining system 100 at a pre-determined distance from the seabed without the need to engage the thrusters from UAV 130. This limits the energy consumed by UAV 130. Further, the dynamic buoyancy system can communicate with mining ship 110 (e.g., via UAV 130 or via another module) to adjust the buoyancy so that the deep-sea mining system 100 can be parked at a given depth in case of adverse weather, repairs, or other reasons.

[0032] The operation of the dynamic buoyancy system 160 (and each of the dynamic buoyancy systems 400) under different buoyancy conditions is schematically shown and described in FIG. 3, according to some embodiments. More specifically, FIG. 3 demonstrates how the level of the liquid (shaded gray) in pressure vessel 200 can be adjusted by dynamic buoyancy system 160 to achieve different buoyancy conditions for the deep-sea mining system 100 shown in FIG. 1.

[0033] According to some embodiments, the gas pressure inside pressure vessel 200 must be sufficient so that when the entire volume of liquid from pressure vessel 200 is pumped out, the gas pressure inside pressure vessel 200 is equal to or slightly below the atmospheric pressure (i.e., between about 14.6 psi and about 3.2 psi, with 14.6 psi being the atmospheric pressure) so that the primary pump 220 can remain operational underwater. In the event that the gas pressure inside pressure vessel 200 is not sufficient and pressure vessel 200 is “under vacuum” (e.g., the pressure of pressure vessel 200 is below 3.2 psi) while there is still liquid to be pumped out, the remaining liquid will start to evaporate and the liquid's vapor pressure can compromise the pump's ability to remove additional liquid from pressure vessel 200. In this “pressure vessel vacuum scenario,” dynamic buoyancy system 160 will fail to provide the necessary buoyancy to the deep-sea mining system 100.

[0034] The aforementioned “pressure vessel vacuum scenario” can be avoided by setting the initial volume and pressure of the gas in pressure vessel 200 such that when all the desired liquid is pumped out, the pressure of the gas, as approximated by the ideal gas law, is not below the pumpable limit of primary pump 220 (e.g., below about 3.2 psi). The gas pressure, along with the maximum internal operating pressure of pressure vessel 200, can determine the minimum volume of gas, and consequently, the maximum volume of liquid allowed in pressure vessel 200. Additional gas volume can be allocated (e.g., a larger pressure vessel 200 may be used) to lower the gas pressure and increase the maximum allowable liquid volume in pressure vessel 200 so that when the pressure vessel 200 is emptied of the liquid, the gas pressure is equal to or above the minimum pumpable limit of 3.2 psi—e.g., between about 14.6 psi and about 3.2 psi, as discussed above. Alternatively, additional static buoyancy may be provided by increasing the amount of buoyancy foam 210 in the dynamic buoyancy system 160.

[0035] In some embodiments, and while the buoyancy of deep-sea mining system 100 is on the surface, the pressure vessel 200 can be prepared with a volume of air that includes: (i) a minimum gas volume 300, (ii) a static buoyancy gas volume 310, and (iii) a gas volume reserved for the descent mass volume 320, as shown in FIG. 3. According to some embodiments, the minimum gas volume 300 prevents the “pressure vessel vacuum scenario” discussed above. The static buoyancy gas volume 310 is an additional gas volume never displaced by the liquid. Consequently, the static buoyancy gas volume 310 does not provide dynamic buoyancy but a static upward force (e.g., a static buoyancy). Finally, the gas volume reserved for the descent mass volume 320, represents the gas volume that is displaced by the liquid. As discussed in connection to FIG. 2, gas can be pumped into pressure vessel 200 with gas pump 250 via valve 260. At this point, the deep-sea mining system 100 has positive buoyancy and last-minute testing can occur.

[0036] According to some embodiments, dynamic buoyancy system 160 is designed so that if the volume of the liquid present in pressure vessel 200 is equal to the neutral buoyancy level, the deep-sea mining system 100 can be neutrally buoyant. In the example of FIG. 3, the neutral buoyancy level is represented by dashed line 300. In the “Pre-descent” stage A, as shown in FIG. 3, the volume of the liquid in pressure vessel 200 is less than the neutral buoyancy level 300 and the ‘descent mass’ volume 320 (e.g., the volume occupied by the ‘descent mass’ of the liquid). The pre-descent stage A, represents a situation where the deep-sea mining system 100 is at the sea surface and has positive buoyancy.

[0037] When the descent is initiated (e.g., by data communication to the controller 230 shown in FIG. 2), a body of liquid equal to the decent mass volume 320 is pumped into the pressure vessel 200 as shown in the “Descending” stage B in FIG. 3. According to some embodiments, the additional liquid volume makes the deep-sea mining system 100 negatively buoyant. As a result, a net downwards force acts on the deep-sea mining system 100 and accelerates it to a terminal downward velocity within the water. According to some embodiments, liquid is pumped in with sub-sea liquid pump 270 via valve 280 shown in FIG. 2. The terminal velocity of the deep-sea mining system 100 can be further controlled by controlling the volume of the liquid in pressure vessel 200. For example, to reduce the terminal velocity, the liquid volume may be gradually reduced from the upper descent mass volume limit 340 in FIG. 3 without reaching the neutral buoyancy level 300. As discussed above in connection to FIG. 2, liquid may be pumped out with primary pump 220 via valve 290.

[0038] As the deep-sea mining system 100 approaches the seabed, it is commanded to pump out enough liquid volume to gain neutral buoyancy, which removes the downward force and causes it to decelerate and stop close to the seabed. In other words, while the deep-sea mining system 100 is reaching its target depth (e.g., between 5 km and 6 km), primary pump 220 can bring the volume of the liquid to the neutral buoyancy level 300 so that the deep-sea mining system 100 becomes neutrally buoyant. This ensures that the deep-sea mining system 100 can stay at its target depth (e.g., at a predetermined distance from the seabed) with minimal effort and without heavily relying on the thrusters from UAV 130. According to some embodiments, the thrusters of UAV 130 shown in FIG. 1 can be used only for fine depth adjustments. This buoyancy condition is shown in FIG. 3 by the “Deceleration/Neutral/Start Collecting” stage C.

[0039] At the target depth, the collection of ore nodules 120 may commence. During the collection process, the deep-sea mining system 100 travels horizontally (e.g., along the x-y plane shown in FIG. 1) and occasionally vertically (e.g., along the z-direction) as required to follow the seabed contour. As the deep-sea mining system 100 collects ore nodules 120 from the seabed and gains weight, neutral buoyancy is maintained by pumping out additional volume of liquid to compensate for the added ore weight, as shown in the “Collecting/Complete/Neutral” stage D of FIG. 3. According to some embodiments, the buoyancy required at any given moment during the collection process can be calculated based on an estimated mining mass rate. This means that the mass or volume of the pumped liquid should follow the total (net in water) mass of the collected ore nodules. Because the ore has less weight in water due to its buoyancy, since it displaces water, the net in water mass is the reduced mass which would create the downward force observed and measured by the systems of deep-sea mining system 100. The amount of buoyancy required can be communicated to the dynamic buoyancy system 160 which can pump out liquid at a dynamically changing rate. As shown in FIG. 3, the majority of the liquid's volume in pressure vessel 200 is used to compensate for the maximum ore mass being loaded while the deep-sea mining system 100 remains neutrally buoyant.

[0040] According to some embodiments, the liquid's pump rate (which is based on the known density of the liquid) is proportional to the pump's pumping rate (which is proportional to the pump's rotational rate) and is matched to the collected (net in water) ore mass loading rate. In some embodiments, the mass loading rate is calculated by the ore collection system 140 shown in FIG. 1. By way of example and not limitation, the ore collection system 140 may estimate the mass loading rate based on: (i) visual cues from onboard cameras (e.g., with implementation of computer vision), (ii) electrical power measurements from a conveyor belt which may track the mass of the collected ores, or (iii) other suitable volumetric or mass measurement instrumentation (e.g., deflection sensors) configured to provide a mass estimate.

[0041] According to some embodiments, any differences between the estimated and actual ore mass will result in a buoyancy error, which can be compensated immediately by the thrusters of UAV 130. As discussed above, operation of the thrusters in a response to a buoyancy error is fed forward to the dynamic buoyancy system 160 to adjust the pump rate of primary pump 220. According to some embodiments, during and upon completion of collection process, deep-sea mining system 100 remains neutrally buoyant.

[0042] In some embodiments, during the ore collection process, the deep-sea mining system 100 can remain positive buoyant so that the thrusters of UAV 130 can jet a small amount of water upwards to keep the deep-sea mining system 100 within the desirable range from the seabed. This positive buoyant state ensures that the thrusters of UAV 130 never jet water downward toward the seabed to disrupt the sediment and create plumes of sediment—which can reduce the visibility for the imaging system in deep-sea mining system 100 and increase the environmental impact.

[0043] Once the deep-sea mining system 100 reaches its maximum load capacity and it is time for it to ascend, dynamic buoyancy system 160 is requested (e.g., via data communications to controller 230) to pump out (e.g., with primary pump 220) a liquid volume equal to the ascend mass volume 350. This allows the deep-sea mining system 100 to achieve positive buoyancy and ascend with the ore payload at terminal velocity towards the sea surface. This is shown schematically by the “Ascending” stage E in FIG. 3. According to some embodiments, a reserve mass volume of liquid is available to ensure that the primary pump 220 operates as intended and to balance the ore load if required. The reserve volume of liquid is shown in FIG. 3 as extra mass volume 360.

[0044] In some embodiments, when it is desirable to temporarily “park” the deep-sea mining system 100 either during the ascent or decent without long term energy use, data communications to controller 230 can command the dynamic buoyancy system 160 to pump in or out liquid (whatever the case may be) to achieve neutral buoyancy. The process can be reversed when the trip resumes.

[0045] According to some embodiments, FIG. 6 is a detailed view of the pressure vessel 200 shown in FIGS. 2-5, which is part of the dynamic buoyancy system 160 shown in FIG. 1. According to some embodiments, pressure vessel 200 can operate in depths greater than 4 km below the sea level (e.g., at sea depths between about 5 km and 6 km). For this reason, the pressure vessel 200 is constructed from a sheet metal shell 610 supported by internal extrusions; namely, axial support members 620 and radial support plates 630.

[0046] As discussed in connection to FIG. 2, pressure vessel 200 is connected, via valve 290, to primary pump 220. In some embodiments, the primary pump 220 can pump liquid (e.g., sea water, filtered sea water, desalinated water, de-ionized water, or another suitable liquid) in and out of the pressure vessel 220 according to the operations described in connection to FIG. 3. When the primary pump 220 is used to introduce and remove the liquid from pressure vessel 220, it may substitute the low-pressure sub-sea liquid pump 270 shown in FIG. 2. In some embodiments, the primary pump 220 and the low-pressure sub-sea liquid pump 270 may coexist so that the low-pressure sub-sea liquid pump 270 can be activated as a secondary pump in emergencies when, for example, the primary pump malfunctions or requires assistance. In further embodiments, a single primary pump 220 or an array of primary pumps 220 may be used to achieve a total power output of about 500 kW or about 670 hp.

[0047] According to some embodiments, the sheet metal shell 610 is an outer shell constructed from bent sheet material, such as titanium, with a water tight seam 640 that connects the two ends of the sheet metal to form the cylindrical body of sheet metal shell 610. By way of example and not limitation, the sheet metal shell 610 can have a diameter of about 1.67 m, a height of about 1.65 m, and a sheet metal thickness of about 10.7 cm.

[0048] In referring to FIG. 6, axial support members 620 are stacked lengthwise inside the cylindrical body. According to some embodiment, axial support members 620 are metal extrusions made from titanium. However this is not limiting, and axial support members 620 may be constructed from other metals, alloys, or materials that have appropriate weight to strength ratio suitable for high pressure environments. In some embodiments, the axial support members 620 have a hexagonal cross-section with each side of the hexagon being about 1 inch in length. In some examples, axial support members 620 are positioned so that 8.2% of the axial surface area is occupied by the axial support members 620. In some embodiments, axial support members 620 may have other suitable cross-sectional shapes (e.g., rectangular, circular, and the like).

[0049] In some embodiments, radial support plates 630 can be stacked between the axial members for resisting radial load. The radial support plates 630 can have an outer diameter that matches the inner diameter of the cylindrical body.

[0050] By way of example and not limitation, the pressure vessel 200 can be constructed as follows. First, the cylindrical body (e.g., sheet metal shell 610) is formed by welding the two ends of the sheet metal lengthwise to form the water tight seam 640. Subsequently, alternating layers of axially aligned support members 620 and radial support plates 630 into the cylindrical body are installed on internal wall surfaces of the sheet metal shell 610. According to some embodiments, the spacing between the radial support plates 630 is determined by the length of axial support members 620. Meanwhile, the size ratio between the radial support plates 630 and axial support members 620 can be defined based on the material used and the maximum operating pressure that the pressure vessel 200 has to withstand. By way of example and not limitation, the radial support plates 630 can have a thickness of about 4 mm. In some examples, the spacing between two adjacent radial support plates 630 can be about 25 mm.

[0051] In some embodiments, each of the radial support plates 630 and axial support members 620 feature small drain holes to allow the trapped liquid within them to drain freely when the level of the liquid inside pressure vessel 200 falls. According to some embodiments, the drain holes are large enough to mitigate pumping losses and small enough to maintain the structural integrity of the radial support plates 630 and axial support members 620.

[0052] As discussed earlier in connection to FIG. 3, the pressure vessel 200 can be partially filled with liquid when in an environment of a low pressure point (e.g., at the surface of the sea). The mass of the liquid at that time should be at least equivalent to the desired mass of the payload that needs to be offset for buoyancy. When buoyancy needs to increase, the primary pump connected to the pressure vessel 200 pumps the liquid out of the pressure vessel. As the liquid is pumped out, the gas inside the pressure vessel 200 expands to fill the volume left behind by the pumped liquid. According so some embodiments, a substantial pressure differential builds between the inside of pressure vessel 200 and the deep-sea environment surrounding it. The internal structure of the pressure vessel 200 (i.e., the axial support members 620 and the radial support plates 630) distributes the stress so that the pressure vessel 200 maintains its shape throughout the mining operation without collapsing.

[0053] Advantageously, pressure vessel 200 disclosed herein has a low fabrication cost and provides the ability to dynamically adjust the buoyancy of deep-sea mining system 100 in high pressure deep-sea environments due to vessel's high strength to weight ratio. Accordingly, pressure vessel 200 is appropriate for cost effective dynamic buoyancy displacement.

[0054] It is to be appreciated that the dynamic buoyancy system described herein is not limited to deep-sea mining systems and can be implemented in any type of submersible vehicle that operates under autonomous, semi-autonomous, or manual control at high depth settings (e.g., in deep lakes or underwater trenches). Further, the dynamic buoyancy system and the pressure vessel described herein is not limited to submersible vehicles that carry payloads but can be implemented without limitation is other types of deep-see submersible vehicles.

[0055] The operating principles descriptions disclosed herein for the dynamic buoyancy system 160 and pressure vessel 200 are directly applicable to deep-sea mining systems equipped with multiple pressure vessels 200, like the dynamic buoyancy systems 400 shown in FIGS. 4 and 5. In the case of multiple dynamic buoyancy systems, each dynamic buoyancy system may be independently controlled. Alternatively, dynamic buoyancy systems may be divided into sub-groups that may be independently controlled. For example, in the 3×7 arrangement of FIG. 4, the 21 dynamic buoyancy systems may be divided to three sub-groups (e.g., a 3×2 sub-group, a 3×3 sub-group, and another 3×2 sub-group) with each sub-group operated independently from the other sub-groups. These and other similar variations and permutations are within the spirit and the scope of the disclosure.

[0056] It is also to be appreciated that various features of the disclosure which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

Terminology

[0057] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0058] The term “approximately”, the phrase “approximately equal to”, and other similar phrases, as used in the specification and the claims (e.g., “X has a value of approximately Y” or “X is approximately equal to Y”), should be understood to mean that one value (X) is within a predetermined range of another value (Y). The predetermined range may be plus or minus 20%, 10%, 5%, 3%, 1%, 0.1%, or less than 0.1%, unless otherwise indicated.

[0059] The indefinite articles “a” and “an,” as used in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0060] As used in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of” “only one of” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0061] As used in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0062] The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof, is meant to encompass the items listed thereafter and additional items.

[0063] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed. Ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term), to distinguish the claim elements.

[0064] Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.