Semi-submersible drone

Abstract

The invention relates to a monohull semi-submersible drone (1) comprising: a submerged hull (20), below a waterline plane (P2); a bow float mast (30), projecting from the submerged hull (20) and ending with an upper end (32) that is arranged above the waterline plane (P2) and that is arranged on the bow side (21) with respect to a front plane of the bow (P21) at one third of a bow-to-stern distance (d21); a stern float mast (40), projecting from the submerged hull (20), arranged between the bow float mast (30) and the stern (22) and comprising an upper end (42) arranged above the waterline plane (P2); and a marine propulsor (60T), arranged below the waterline plane (P2).

Description

[0001] TITLE: Semi-submersible Drone

[0002] The present invention relates to a semi-submersible drone.

[0003] CN213649852U describes a semi-submersible drone with a semi-submersible hull comprising a lower hull, a mid-pillar fixed to the top of the lower hull at a mid-position, and a tail pillar fixed to the top of the lower hull at the stern. The mid-pillar supports a pair of fixed wings equipped with solar panels and hydrological sensors, as well as a top platform with a wind turbine, an antenna for remote control of the drone, and a surface camera. The tail pillar supports a top platform suitable for receiving an aerial drone.

[0004] One drawback of this drone is that its relatively large central pylon imparts significant drag, resulting in a strong pitching moment when the drone moves forward. Consequently, the drone cannot be propelled at excessive speeds due to this drag and the risk of becoming unbalanced by pitching up. Furthermore, the large central pylon compromises the drone's stealth, as a substantial portion of it protrudes above the water's surface.

[0005] The aim of the invention is therefore to offer a semi-submersible drone whose stability, stealth and navigation speed are improved.

[0006] To this end, the invention relates to a semi-submersible drone, which is monohull-shaped, which has a mass distribution defining a waterline plane, and which comprises a main body, including:

[0007] - a submersible hull, comprising a bow and a stern crossed by a longitudinal axis and arranged entirely below the waterline plane to be submerged when the semi-submersible drone is afloat, a front bow plane being defined perpendicular to the longitudinal axis, the front bow plane being arranged at one-third of a bow-to-stern distance, bow side,

[0008] - a bow float mast, fixedly attached to the underwater hull, projecting from the underwater hull, arranged between the bow and the stern and terminating in an upper end arranged above the waterline plane to be raised when the semi-submersible drone is afloat and arranged on the bow side relative to the forward bow plane, and

[0009] - a stern float mast, permanently attached to the underwater hull, projecting from the underwater hull, arranged between the bow float mast and the stern, and comprising an upper end arranged above the waterline plane to be above the surface when the semi-submersible drone is afloat. The drone further comprises a naval propulsion system, attached to the main body and arranged below the waterline plane to be submerged when the semi-submersible drone is afloat.

[0010] In other words, the drone's mass, particularly that of the floating masts and the underwater hull, is distributed so that when the drone is submerged in a reference volume of water at rest (i.e., without current or waves) and the naval propulsion system is inactive, the drone tends to reach a stable position through buoyancy—that is, under the sole effect of gravity and Archimedes' principle—in which the waterline plane is coplanar with the plane of the reference water surface. The upper ends of the floating masts are above the reference water, while the underwater hull and the naval propulsion system are fully submerged. The waterline plane is then horizontal.The waterline plane is fixed relative to the main body and is entirely determined by the drone's structure. Preferably, the waterline plane is the waterline plane defined when the drone is fully loaded and fueled (if fuel is intended for drone propulsion) and submerged in Mediterranean seawater at 15°C, which serves as the reference water. During drone operation, depending on the characteristics of the water in which the drone is actually submerged, such as salinity and temperature, the drone's payload, currents and water agitation, and the drone's operating speed, the water surface is obviously not always flat or coplanar with the waterline plane.

[0011] In the invention, the inclusion of both a bow and a stern float mast, positioned at a considerable distance from each other, at least at their upper ends, with the bow float mast close to the bow, provides good trim stability for the drone. This also allows for the float masts to be particularly thin, reducing their hydrodynamic drag and thus the pitching moment when the semi-submersible drone is moving forward along its longitudinal axis. With moderate hydrodynamic drag and pitching moment, high-speed navigation can easily be achieved. Because the float masts are thin, the drone's stealth is excellent, as it is essentially submerged except for the upper ends of the float masts.More specifically, the bow float mast is planned to be arranged so that its Archimedean center of buoyancy is located on the bow side relative to the front bow plane, when the drone is afloat in still water.

[0012] In this document, "drone" refers to an unmanned, remotely piloted vehicle. "Monohull" refers to a drone consisting of a single longitudinal hull, namely the underwater hull. This contrasts with, for example, a drone that is multihulled, such as a catamaran or trimaran, or that is a platform. "Semi-submersible" refers to a drone whose main volume is designed to be fully submerged, namely the underwater hull and the propulsion system, while a smaller portion is designed to remain above water at all times, namely the upper ends of the floating masts. Unlike a fully submersible drone, it is not designed to be capable of complete submersion. "Floating mast" refers to a mast that plays a major role in the drone's weight distribution, similar to, for example, the underwater hull.

[0013] Depending on other advantageous aspects of the invention, one or more of the following features are provided, taken individually or in all technically possible combinations:

[0014] - a frontal stern plane is defined perpendicular to the longitudinal axis, the frontal stern plane being arranged at two-thirds of the bow-stern distance, on the stern side;

[0015] - the upper end of the stern float mast is arranged on the stern side relative to the stern frontal plane;

[0016] - the bow float mast is entirely arranged on the bow side in relation to the front bow plane;

[0017] - the stern float mast is entirely arranged on the stern side in relation to the stern frontal plane;

[0018] - the upper end of the bow float mast and the upper end of the stern float mast are equidistant from the waterline plane;

[0019] - the semi-submersible drone includes a keel projecting from the underwater hull, so that the underwater hull is arranged between the upper end of the floating masts and the keel and the keel is arranged between the forward bow plane and the forward stern plane;

[0020] - at least one of the floating masts has an intermediate portion, connecting the upper end of this floating mast to the underwater hull, having a wing shape extending along a plane parallel to, or including, the longitudinal axis, with a leading edge directed towards the bow and a trailing edge directed towards the stern;

[0021] - the naval propulsion unit is a port-side naval propulsion unit, attached to the underwater hull;

[0022] - the semi-submersible drone includes a starboard naval thruster, attached to the underwater hull and arranged below the waterline plane to be submerged when the semi-submersible drone is afloat; - the underwater hull is arranged between the port and starboard naval thrusters, the port and starboard naval thrusters being configured to produce a forward displacement of the semi-submersible drone along the longitudinal axis, when the semi-submersible drone is afloat;

[0023] - the semi-submersible drone includes a compensating fin arranged entirely below the waterline plane to be submerged when the semi-submersible drone is afloat, fixedly attached to the main body, arranged on the bow side relative to the front bow plane, shaped to impart a pitching moment to the semi-submersible drone when the semi-submersible drone is afloat and moving forward along the longitudinal axis;

[0024] - the semi-submersible drone includes at least one surface monitoring sensor, attached to the upper end of the bow float mast or the upper end of the stern float mast;

[0025] - the semi-submersible drone includes at least one underwater surveillance sensor, attached to the underwater hull;

[0026] - the semi-submersible drone includes at least one telecommunications module, for remote control, the telecommunications module including an antenna attached to the upper end of the bow float mast or the upper end of the stern float mast.

[0027] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0028] [Fig. 1] Figure 1 is a perspective view of a semi-submersible drone according to a first embodiment of the invention.

[0029] [Fig. 2] Figure 2 is a side view of the drone in Figure 1.

[0030] [Fig. 3] Figure 3 comprises four pairs of views A, B, C and D, each pair of views including a schematic side view and a schematic front view of the same semi-submersible drone according to an embodiment of the invention distinct from that of the other pairs of views.

[0031] Figures 1 and 2 show a semi-submersible monohull drone 1, according to a first embodiment of the invention, comprising a main body 2, which includes a single hull 20, which is underwater. The main body 2 also includes a bow float mast 30 and a stern float mast 40.

[0032] Drone 1 also includes a 60B port-side naval thruster and a 60T starboard-side naval thruster. Drone 1 also preferably includes a 70B port-side trim tab and a 70T starboard-side trim tab. Drone 1 also preferably includes a 50 keel.

[0033] The mass distribution of drone 1, mainly the mass of the hull 20, the masts 30 and 40 and the keel 50 if provided, but also the compensating fins 70B and 70T if provided and the thrusters 60B and 60T, means that the drone defines a waterline plane P2 shown in Figure 2, fixed with respect to the main body 2.

[0034] The underwater hull 20 comprises a bow 21 and a stern 22, traversed by a longitudinal axis X20 and connected by an intermediate section 23 of the hull 20. The axis X20 is preferably parallel to plane P2. In operation, the axis X20 is intended to be horizontal. The intermediate section 23 is, for example, cylindrical with a circular base and coaxial with the axis X20. The bow 21 and the stern 22 each have a convergent shape, for example, cylindro-conical and / or tapered coaxially with the axis X20, from the intermediate section 23 to the tip, for hydrodynamic reasons. Overall, the hull 20 has an elongated shape along the axis X20, with a maximum diameter much smaller than its length along the axis X20. The hull 20, including the bow 21, the stern 22 and the intermediate part 23, is entirely arranged under the plane P2 and at a distance from the plane P2.In other words, hull 20 is configured to be fully submerged when drone 1 is afloat, i.e., submerged in water.

[0035] As shown in Figure 2, a forward frontal plane P21 is defined perpendicular to the longitudinal axis X20 and to plane P2. The forward frontal plane P21 is located at one-third of the bow-to-stern distance d21, on the bow side. A stern frontal plane P22 is defined perpendicular to the longitudinal axis X20 and to plane P2. The bow-to-stern distance d21-d22 is measured parallel to the axis X20, from one end of the hull 20 to the other. The stern frontal plane P22 is located at two-thirds of the bow-to-stern distance d21, on the stern side. In other words, the parallel planes P21 and P22 divide the hull 20 into three equal parts along the axis X20. In this case, both planes P21 and P22 are traversed by the intermediate part 23 of the hull 20.

[0036] The bow float mast 30 comprises an intermediate portion 31 and an upper end 32, which terminates the mast 30 and is connected to the hull 20 by the intermediate portion 31.

[0037] The mast 30 is fixedly attached to the underwater hull 20 via the intermediate section 31. The mast 30 projects from the underwater hull 20. The mast 30 projects from the intermediate section 23 of the hull 20, to be positioned between the bow 21 and the stern 22. Preferably, the mast 30 is straight and extends along a sagittal plane P30 of the main body 2, the sagittal plane P30 including the axis X20 and being perpendicular to the plane P2. Preferably, the mast 30 extends perpendicularly to the axis X20. In the example, the mast 30 is therefore designed to be vertical when the drone 1 is afloat. Alternatively, as shown schematically in the pairs of views A and B in Figure 3, the mast 30 extends along the sagittal plane P30 but is oblique towards the bow 21. Alternatively, the mast 30 is oblique towards the stern 22. Alternatively, the mast 30 is not straight but is, for example, curved.

[0038] The upper end 32 is arranged above the waterline plane P2 so that it is above water when the drone 1 is afloat. The intermediate portion 31 crosses the plane P2 and is therefore intended to be partially submerged.

[0039] Preferably, the mast 30 is entirely arranged on the bow side 21 relative to the forward bow plane P21. In other words, the mast 30 is located between the plane P21 and the end of the hull 20 on the bow side 21, for example, midway between the two. At the very least, the upper end 32 is arranged on the bow side 21 relative to the forward bow plane P21. Preferably, the bow float mast 30 is arranged so that its center of buoyancy is located on the bow side 21 relative to the forward bow plane P21 when the drone 1 is afloat in still water.

[0040] Alternatively, as shown in the pair of views B in Figure 3, the upper end 32 is arranged on the bow side 21 relative to the bow frontal plane P21, while part of the mast 30 is arranged on the stern side 22 relative to the bow frontal plane P21, with the mast 30 passing through the bow frontal plane P21. Preferably, in this case as well, the bow float mast 30 is arranged so that its center of buoyancy is located on the bow side 21 relative to the bow frontal plane P21 when the drone 1 is afloat in still water.

[0041] Preferably, the intermediate portion 31 has a wing shape extending along a plane, here the sagittal plane P30, parallel to or including the longitudinal axis X20, with a leading edge 33 directed towards the bow 21 and a trailing edge 34 directed towards the stern 22. The leading edge 33 and the trailing edge 34 extend along the mast 30, following the plane along which the wing extends, here the plane P30. The edges 33 and 34 each connect the hull 20 to the end 32. This particular shape of the mast 30 helps to limit the hydrodynamic drag of the mast 30 and the pitching moment when the drone 1 is moving forward.

[0042] The stern float mast 40 comprises an intermediate portion 41 and an upper end 42, which terminates the mast 40 and is connected to the hull 20 by the intermediate portion 41.

[0043] Mast 40 is fixedly attached to the underwater hull 20 via the intermediate section 41. Mast 40 projects from the underwater hull 20. Mast 40 projects from the intermediate section 23 of the hull 20, to be positioned between the bow 21 and the stern 22. Mast 40 is positioned between the stern 22 and mast 30, at a distance from mast 30. Preferably, mast 40 is straight and extends along the sagittal plane P30. Preferably, mast 40 extends perpendicularly to the axis X20. In this example, mast 40 is therefore designed to be vertical when the drone 1 is afloat. Alternatively, as shown schematically in the pairs of views A and B in Figure 3, the mast 40 extends along the sagittal plane P30 but is oblique towards the stern 22. Alternatively, the mast 40 is oblique towards the bow 21. Alternatively, the mast 40 is not straight but is, for example, curved.

[0044] The upper end 42 is positioned above the waterline plane P2 so that it is above water when the drone 1 is afloat. The intermediate portion 41 crosses the plane P2 and is therefore intended to be partially submerged.

[0045] Preferably, the upper end 32 of the bow mast 30 and the upper end 42 of the stern mast 40 are equidistant from the waterline plane P2, i.e., at the same height. This ensures that both ends 32 and 42 are particularly low above the waterline when the drone is afloat, thus ensuring the stealth of drone 1.

[0046] Preferably, the mast 40 is entirely arranged on the stern side 22 relative to the stern frontal plane P22. In other words, the mast 40 is located between the plane P22 and the stern end 22 of the hull 20, for example, midway between the two. At the very least, the upper end 42 is arranged on the stern side 22 relative to the stern frontal plane P22. Preferably, the stern float mast 40 is arranged so that its center of buoyancy is located on the stern side 22 relative to the stern frontal plane P22 when the drone 1 is afloat in still water.

[0047] Alternatively, as shown in the pair of views B in Figure 3, the upper end 42 is arranged on the stern side 22 relative to the stern frontal plane P22, while part of the mast 40 is arranged on the bow side 21 relative to the stern frontal plane P22, with the mast 40 passing through the stern frontal plane P22. Preferably, in this case as well, the stern float mast 40 is arranged so that its center of buoyancy is located on the stern side 22 relative to the stern frontal plane P22 when the drone 1 is afloat in still water.

[0048] Preferably, the intermediate portion 41 has a wing shape extending along a plane, here the sagittal plane P30, parallel to or including the longitudinal axis X20, with a leading edge 43 directed towards the bow 21 and a trailing edge 34 directed towards the stern 22. The leading edge 43 and the trailing edge 44 extend along the mast 40, following the plane along which the wing extends, here the plane P30. The edges 43 and 44 each connect the hull 20 to the end 42. This particular shape of the mast 40 helps to limit the hydrodynamic drag of the mast 40 and the pitching moment when the drone 1 is moving forward.

[0049] Each floating mast 30 and 40 differs from a simple fin, notably in that the floating mast is elongated upwards from the underwater hull 20, so that its upper end is above water when the drone 1 is afloat, and particularly in that the floating mast plays a major role in the buoyancy of the drone 1, given its volume compared to that of the hull 20. In other words, each floating mast is significant in its length (i.e., vertically) and relatively narrow in its width (i.e., parallel to the longitudinal axis X20). In other words, each floating mast is longer vertically from the hull 20 than it is wide parallel to the axis X20.

[0050] Alternatively, as shown in view pair C of Figure 3, a pair of masts 30 and / or a pair of masts 40 are provided. In this case, the two masts 30 or 40 of each pair are, for example, arranged in a "V", on either side of the sagittal plane P30, being, for example, arranged symmetrically with respect to the sagittal plane P30. For example, masts 30 and 40 are parallel to plane P21.

[0051] The keel 50, if present, preferably projects from the intermediate section 23 of the hull 20, ideally along the sagittal plane P30, so that the underwater hull 20 is positioned between the ends 32 and 42 and the keel 50, and the keel is positioned between the frontal planes P21 and P22. In other words, the keel 50 points downwards while the masts 30 and 40 point upwards. The keel 50 lies entirely below the waterline plane P2. When the drone 1 is afloat, the keel is fully submerged. Keel 50, when present, plays a major role in the weight distribution of drone 1, acting as a counterweight to masts 30 and 40. This means that drone 1 tends to orient itself with keel 50 pointing downwards and masts 30 and 40 pointing upwards. Keel 50 can also impart a pitching moment to compensate for the pitching moment produced by masts 30 and 40 when drone 1 is moving forwards.

[0052] The compensating fins 70B and 70T, if provided, are preferably fixedly attached to the main body 2, and preferably attached to the hull 20. Each fin 70B and 70T is arranged entirely below the waterline plane P2 so that it is submerged when the semi-submersible drone is afloat. The fins 70B and 70T are preferably arranged on the bow side 21 relative to the forward bow plane P21. Preferably, the port fin 70B projects from the hull 20, in particular from the intermediate section 23, in a port direction, that is to say, laterally to the left in the forward direction of travel of the drone 1. Preferably, the starboard wing 70T protrudes from the hull 20, in particular from the intermediate part 23, in a starboard direction, i.e. laterally to the right in the forward direction of the drone 1. The wings 70B and 70T are advantageously symmetrical with respect to the sagittal plane P30.Preferably, hull 20 is arranged between fins 70B and 70T.

[0053] Each 70B and 70T fin has a wing shape designed to impart a pitching moment to drone 1 when the semi-submersible drone is afloat and moving forward along the longitudinal axis X20. To achieve this, as shown in Figure 2 for fin 70T, each 70B and 70T fin is advantageously inclined at an oblique angle in the pitching position, meaning its leading edge is angled downwards, opposite the mast 30, relative to its trailing edge, which is angled upwards. By imparting a pitching moment, the 70B and 70T fins passively compensate for the pitching moment generated by masts 30 and 40 during forward navigation.

[0054] Each 60B and 60T naval propulsion unit is attached to the main body 2, preferably to the hull 20, being arranged entirely below the waterline plane P2 to be submerged when the semi-submersible drone is afloat.

[0055] The 60B and 60T thrusters are preferably arranged between the bow 21 and the stern 22, preferably between planes P21 and P22. Preferably, the port thruster 60B projects from the hull 20, in particular from the intermediate section 23, in a port direction. Preferably, the starboard thruster 60T projects from the hull 20, in particular from the intermediate section 23, in a starboard direction. The 60B and 60T thrusters are advantageously arranged symmetrically with respect to the sagittal plane P30. Preferably, the hull 20 is arranged between the 60B and 60T thrusters. Each naval thruster 60B and 60T, when submerged, is capable of providing a propulsion force parallel to the X20 axis, to generate forward movement of the drone along the X20 axis, and possibly reverse movement. For this purpose, each propulsion system includes, for example, a propulsion propeller, driven by a motor.The propeller's axis of rotation is preferably parallel to the X20 axis. The propeller is, for example, coaxially housed within a tubular sleeve 61 of the 60B or 60T thruster. Preferably, the propeller's axis of rotation is fixed relative to the main body 2, particularly relative to the hull 20. To achieve this, the tubular sleeve is preferably fixedly attached to the hull 20. Preferably, the motor is electric. Preferably, a separate electric motor is provided for each 60B and 60T marine thruster. Preferably, the respective electric motor of each 60B and 60T marine thruster is housed directly within the tubular sleeve 61 of said marine thruster. For this purpose, a brushless motor suitable for operation in water may be provided, for example. Alternatively, the electric motor(s) are housed inside the hull 20.To power the electric motor, a reserve of electricity is preferably provided, for example in the form of a battery, preferably carried inside the hull 20. An electrical power converter is advantageously provided, through which the battery supplies the electric motors with the desired power.

[0056] Preferably, the propulsion power and / or propulsion direction of each naval thruster 60B and 60T is adjustable independently of the other naval thruster. By adjusting the propulsion power and / or propulsion direction of the 60B and 60T thrusters, forward movement can be achieved, selectively in a straight line and in a yaw curve. Therefore, a rudder is not required for drone 1, thus limiting the number of actuators for the drone and improving its reliability and stealth. Thanks to these arrangements, preferably, no external part of drone 1 is mobile, except for the propeller of the 60B and 60T thrusters, ensuring its stealth and reliability, and reducing its cost. In particular, it is easy to design the main body 2 to be completely enclosed and watertight.

[0057] Alternatively, a single naval propulsion system can be provided, preferably with an additional rudder to steer drone 1 in yaw.

[0058] Preferably, the semi-submersible drone includes at least one telecommunications module 80 for remote control. Advantageously, the telecommunications module includes an antenna 81, which is attached to the upper end 42 of the stern float 40 so that it is raised above the waterline when the drone 1 is afloat. Alternatively, the antenna 81 could be attached to the bow float 30. The telecommunications module 80 also includes telecommunications electronics 82, housed inside the main body 2, for example in the hull 20, and electronically connected to the antenna. The antenna is preferably a satellite antenna. The telecommunications module 80 is also electronically connected to the thrusters 60B and 60T, for example by being connected to the electrical power converter, in order to control the thrusters 60B and 60T according to the commands received at the antenna 81.A status report from the 60B and 60T thrusters or the onboard battery can also be sent via the telecommunications module 80.

[0059] Alternatively to, or in addition to, antenna 81, another antenna for a different type of telecommunication can be provided on the same upper end of the mast, or a cable outlet for wired telecommunication can be provided for remote control of the drone 1. The cable outlet can alternatively be located at the stern 22. Preferably, the semi-submersible drone 1 includes one or more surface surveillance sensors 83, attached to the upper end 32 of the bow float mast 30, so that they are exposed when the drone 1 is afloat. It is advantageous to mount these sensors 83 on the bow mast 30 to capture the aerial environment in front of the drone 1 and thus facilitate remote control of the drone, and / or enable reconnaissance, exploration, surveillance, or espionage missions using the drone 1. The sensor(s) 83 may include, for example, a camera, radar, LiDAR, and / or a microphone.Alternatively or in addition, such sensors 83 may nevertheless be attached to the upper end 42 of the stern float mast 40. The telecommunications module 80 is electronically connected to said sensors 83 to transmit the information from the sensors 83 via the antenna 81.

[0060] Preferably, the semi-submersible drone 1 comprises one or more underwater surveillance sensors 84, attached to the underwater hull 20. Each sensor 84 can be located inside the hull 20 or on top of it. It is advantageous to position these sensors 83 on the bow 21 to capture the underwater environment in front of the drone 1, thus facilitating remote control of the drone 1 and / or enabling reconnaissance, exploration, surveillance, or espionage missions using the drone 1. The sensor(s) 84 may include, for example, a camera, sonar, and / or hydrophone. Alternatively, or in addition, such sensors 84 may be located on the stern 22. The telecommunications module 80 is electronically connected to the sensors 84 to transmit the information from the sensors 84 via the antenna 81.

[0061] The main body 2, specifically the hull 20, is designed to carry a payload, which may include the aforementioned sensors, a sonar, and / or a reconnaissance / surveillance system. Alternatively, or in addition, the payload may include cargo, for example, to perform a delivery with drone 1.

[0062] It is preferable that masts 30 and 40 be fixed relative to hull 20. However, it is possible to make masts 30 and 40 telescopic to adjust the buoyancy of drone 1 according to the characteristics of the water in which drone 1 will be submerged. Alternatively, or in addition, ballast can be integrated into the main body 2 for the same purpose.

[0063] In addition to or as a replacement for the on-board battery, drone 1 can be electrically powered by cable, in particular with a cable departure via mast 40 or stern 22.

[0064] In the preceding, we have described embodiments in which the masts 30 and 40 protrude from the hull 20 without passing through it completely. Alternatively, as shown in the pair of views D in Figure 3, the masts 30 and 40 are provided to pass completely through the hull 20, each having a lower end 39 and 49 projecting downwards from the hull 20, opposite the upper ends 32 and 42. Preferably, for each mast 30 and 40, the length of mast extending beyond the hull 20 at the upper end 32 or 42 is greater than the length of mast extending beyond the hull 20 at the lower end 39 or 49. In this case, the presence of the keel 50 is optional, since the ends 39 and 49 create a nose-down moment to counteract the nose-up moment of the masts 30 and 40 at the ends 32 and 42.

[0065] It is advantageous to stipulate that masts 30 and 40 are at the same height relative to hull 20, meaning that the length of mast 30 extending beyond hull 20 at the lower end 39 is equal to the length of mast 40 extending beyond hull 20 at the lower end 49. Alternatively, one of the masts 30 and 40 can be lower than the other, meaning that the length of mast 30 extending beyond hull 20 at the lower end 39 is either less than or greater than the length of mast 40 extending beyond hull 20 at the lower end 49. These considerations, applicable to the lower ends 39 and 49, can also be applied to the upper ends 32 and 42.

Claims

CLAIMS Semi-submersible drone (1), which is monohull, which has a mass distribution defining a waterline plane (P2), and which comprises: a main body (2), comprising: • a submersible hull (20), comprising a bow (21) and a stern (22) crossed by a longitudinal axis (X20) and arranged entirely below the waterline plane (P2) to be submerged when the semi-submersible drone (1) is afloat, a front bow plane (P21) being defined perpendicular to the longitudinal axis (X20), the front bow plane (P21) being arranged at one-third of a bow-stern distance (d21), on the bow side (21), • a bow float mast (30), fixedly attached to the underwater hull (20), projecting from the underwater hull (20), arranged between the bow (21) and the stern (22) and terminating in an upper end (32) arranged above the waterline plane (P2) to be raised when the semi-submersible drone (1) is afloat and arranged on the bow side (21) relative to the forward bow plane (P21), and • a stern float mast (40), fixedly attached to the underwater hull (20), projecting from the underwater hull (20), being arranged between the bow float mast (30) and the stern (22) and comprising an upper end (42) arranged above the waterline plane (P2) to be emerged when the semi-submersible drone (1) is afloat; and a naval thruster (60B, 60T), attached to the main body (2) and being arranged below the waterline plane (P2) to be submerged when the semi-submersible drone (1) is afloat. Semi-submersible drone (1) according to claim 1, wherein: a stern front plane (P22) is defined perpendicular to the longitudinal axis (X20), the stern front plane (P22) being arranged at two-thirds of the bow-stern distance (d21), stern side (22); and the upper end (42) of the stern float mast (40) is arranged stern side (22) with respect to the stern front plane (P22).Semi-submersible drone (1) according to claim 2, wherein: the bow float mast (30) is entirely arranged on the bow side (21) with respect to the front bow plane (P21); and. The stern float mast (40) is entirely arranged on the stern side (22) with respect to the stern frontal plane (P22). Semi-submersible drone (1) according to any one of the preceding claims, wherein the upper end (32) of the bow float mast (30) and the upper end (42) of the stern float mast (40) are equidistant from the waterline plane (P2). Semi-submersible drone (1) according to any one of claims 2 or 3, wherein the semi-submersible drone (1) comprises a keel (50) projecting from the underwater hull (20), such that the underwater hull (20) is arranged between the upper end (32, 42) of the floating masts (30, 40) and the keel (50) and that the keel (50) is arranged between the forward bow plane (P21) and the forward stern plane (P22).Semi-submersible drone (1) according to any one of the preceding claims, wherein at least one of the float masts (30, 40) has an intermediate portion (31, 41), connecting the upper end (32, 42) of this float mast (30, 40) to the underwater hull (20), having a wing shape extending along a plane parallel to, or including, the longitudinal axis (X20), with a leading edge (33, 43) directed towards the bow (21) and a trailing edge (34, 44) directed towards the stern (22).Semi-submersible drone (1) according to any one of the preceding claims, wherein: the naval thruster (60B, 60T) is a port naval thruster (60B), integral with the submersible hull (20); the semi-submersible drone (1) comprises a starboard naval thruster (60T), integral with the submersible hull (20) and arranged below the waterline plane (P2) to be submerged when the semi-submersible drone (1) is afloat; and the submersible hull (20) is arranged between the port naval thruster (60B) and the starboard naval thruster (60T), the port (60B) and starboard (60T) naval thrusters being configured to produce a forward displacement of the semi-submersible drone (1) along the longitudinal axis (X20), when the semi-submersible drone (1) is afloat.Semi-submersible drone (1) according to any one of the preceding claims, wherein the semi-submersible drone (1) comprises a compensating fin (70B, 70T) arranged entirely below the waterline plane (P2) to be submerged when the semi-submersible drone (1) is afloat, fixedly attached to the main body (2), arranged on the bow side (21) relative to the front bow plane (P21). 15 configured to impart a pitching moment to the semi-submersible drone (1) when the semi-submersible drone (1) is afloat and moving forward along the longitudinal axis (X20). Semi-submersible drone (1) according to any one of the preceding claims, wherein the semi-submersible drone (1) comprises at least one surface surveillance sensor (83), attached to the upper end (32) of the bow float mast (30) or the upper end (42) of the stern float mast (40). Semi-submersible drone (1) according to any one of the preceding claims, wherein the semi-submersible drone (1) comprises at least one underwater surveillance sensor (84), attached to the underwater hull (20).Semi-submersible drone (1) according to any one of the preceding claims, wherein the semi-submersible drone (1) comprises at least one telecommunications module (80), for remote control, the telecommunications module comprising an antenna (81) attached to the upper end (32) of the bow float mast (30) or to the upper end (42) of the stern float mast (40).

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