aerostat

Abstract

Disclosed is an aerostat (100) comprising a first balloon (10a) and a second balloon (10b) that extend in a longitudinal direction (X), and a connection structure (30) configured to keep the first balloon and the second balloon stationary relative to each other. The connection structure (30) comprises, for each of the first and second balloons, a first frame (31a, 31b) connected to one of the first and second balloons, the first frame having substantially the same shape as the envelope in a transverse plane (YZ) of the balloon to which the first frame is connected, and partially surrounding the envelope, on the outside, and a first crosspiece (32) which connects the first frame of the first balloon and the first frame of the second balloon in the lateral direction (Y).

Description

[0001] Aerostat TECHNICAL FIELD The present invention relates to aerostats. PRIOR TECHNOLOGY More particularly, the invention relates to an aerostat comprising: - a first balloon and a second balloon extending in a longitudinal direction, each balloon consisting of an envelope containing a gas lighter than air, - a connecting structure configured to maintain the first and second balloons relative to each other. Patent document WO 2004 / 016503 shows a dirigible with two non-rigid envelopes connected by a connecting structure to form a catamaran shape. The connecting structure may include tubular composite elements. DESCRIPTION OF THE INVENTION The purpose of this disclosure is to further improve aerostats comprising two balloons.For this purpose, the present disclosure relates to an aerostat in which the connecting structure comprises: for each of the first and second balloons, a first frame connected to one of the balloons of said first and second balloons, each of the first frames having substantially the shape of the envelope in a transverse plane of said balloon to which the first frame is connected, and partially surrounding this envelope externally, said first frames being positioned in a first longitudinal position in the longitudinal direction, and - a first cross member which connects the first frame of the first balloon and the first frame of the second balloon in a laterally direction, said first cross member fixing the position of the balloons in the laterally direction. By means of these arrangements, the balloons are perfectly held by the first frame of the first balloon and by the second frame of the second balloon.These first frames conform well, externally, to the shape of the balloons in a transverse plane, thus ensuring effective support for the first and second balloons. These first frames, partially surrounding the balloons, can support the static lift (aerostatic) in the vertical direction, upwards on the aerostat, generated by the lighter-than-air gas. These first frames allow the use of a variety of fastening means between the first frames and the balloons, along the length of these first frames, which improves the support of the two balloons. In various embodiments of the device according to this disclosure, one or more of the following arrangements may also be used.In one design, the first frames are C-shaped, with the first frame attached to the first balloon and the first frame attached to the second balloon oriented in opposite directions. An opening in each first frame faces outward from the aerostat to accommodate the first and second balloons, respectively, while one body of each first frame faces inward from the aerostat to be connected by the first cross member. In another design, the C-shaped first frames extend in an angular sector between 20 and 270 degrees around the envelope of each balloon. In yet another design, an upper end zone of each balloon is covered by these first frames to support the first and second balloons vertically upwards.In one aspect, each of the first reinforcements is fixedly attached to a balloon at a plurality of attachment points, more than two, along said balloon, to distribute a fixation stress of the first reinforcement onto the balloon's envelope. In another aspect, the plurality of attachment points is greater than or equal to three and less than or equal to five. In another aspect, each attachment point includes a first reinforcement attachment inserted between the envelope and an external attachment layer enclosing said attachment, and said external layer being fixed to the envelope by a process of gluing, sewing, plastic welding, or a combination of these processes.In one aspect, the connecting structure further comprises: - a first lower rod directly or indirectly connecting a lower point of the first reinforcement of the first ball to the first cross member, and - a second lower rod directly or indirectly connecting a lower point of the first reinforcement of the second ball to the first cross member. In one aspect, the first and second lower rods are rigid, elastic, or elastic with damping. In one aspect, a connecting element provides either a rigid fixed connection between the first reinforcement and the first cross member or a hinged connection between the first reinforcement and the first cross member.According to one aspect, the aerostat further comprises a tail assembly connecting the first and second balloons in a longitudinal tail position in the longitudinal direction, said longitudinal tail position being different from the first longitudinal position. According to one aspect, the first cross member is equipped with a first propulsion device. According to one aspect, the first propulsion device is orientable by pivoting about a lateral axis to be angularly oriented between a horizontal propulsion position and a vertical propulsion position.According to one aspect, the linking structure comprises: for each of the first and second balloons, a second frame connected to one balloon of said first and second balloons, each of the second frames having substantially the shape of the envelope in a transverse plane of said balloon to which said second frame is connected, and partially surrounding this envelope externally, said second frames being positioned in a second longitudinal position in the longitudinal direction, different from the first longitudinal position, and - a second cross member which connects the second frame of the first balloon and the second frame of the second balloon in a lateral direction, said second cross member fixing the position of the balloons in the lateral direction.BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the disclosure will become apparent in the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings. In the drawings: - Figure 1 is a perspective view of an aerostat according to this disclosure, - Figure 2 is a front view of the aerostat of Figure 1, - Figure 3 is a top view of the aerostat of Figure 1, and - Figure 4 is a front view of the connecting structure of the aerostat of Figures 1 to 3, and - Figure 5 is a front view of a variant of the connecting structure of an aerostat, and - Figure 6 is a cross-sectional view of an XZ plane of the aerostat of Figure 1. In the various figures, the same numerals designate identical or similar elements.The figures include a longitudinal direction X, a lateral direction Y perpendicular to the longitudinal direction X, and a vertical direction Z perpendicular to the two previous ones. The aerostat moves primarily along the longitudinal direction X. The vertical direction Z corresponds to an upward direction of elevation.

[0002] DETAILED DESCRIPTION Figures 1 to 3 illustrate an example of an aerostat 100 according to this disclosure. The aerostat 100 comprises: - a first balloon 10a and a second balloon 10b extending in a longitudinal direction X, each balloon consisting of an envelope containing a gas lighter than air, - a connecting structure 30 configured to maintain the first and second balloons relative to each other. Such an aerostat may be called a catamaran-type (twin-balloon) aerostat, by analogy to a boat with two floats. The aerostat 100 may comprise a first balloon 10a and a second balloon 10b, or more than two balloons, arranged successively aligned in a lateral direction Y, or optionally arranged in the lateral direction Y and the vertical direction Z. In particular, in the transverse plane YZ, the balloons may be arranged in a staggered pattern.The following description will use, as a non-limiting example for the sake of simplicity, a two-balloon configuration. The first balloon 10a and the second balloon 10b extend in the longitudinal direction X between a nose 101 of the aerostat 100 located towards the front in this longitudinal direction X and a tail 102 of the aerostat 100 located towards the rear of the aerostat in a direction opposite to the longitudinal direction X. By extension, the terms nose and tail will also be used for each balloon 10a, 10b, or the envelopes of these balloons. Each balloon 10a, 10b has a roughly ovoid shape with a significant length in the longitudinal direction X.By convention, as shown in Figure 2, we will consider: - an upper portion 10as, 10ab respectively of the first and second balloons 10a, 10b, each upper portion corresponding to the upper half of the balloon in question, and above a horizontal plane H, and - a lower portion 10ai, 10bi of the first and second balloons 10a, 10b, each lower portion corresponding to the lower half of the balloon in question, and below a horizontal plane H. Similarly, each balloon 10a, 10b includes a vertex or vertex line Sa, Sb corresponding to the upper line of the balloon in question between the nose 101 and the tail 102 of that balloon. The first balloon 10a and the second balloon 10b are flexible or semi-rigid balloons. Such balloons are called non-rigid because they do not have a rigid structure that maintains the shape of the envelope containing the gas lighter than air.The shape of the envelope of a flexible or semi-rigid balloon is determined by the gas pressure inside the balloon, which is essentially equal to or greater than the air pressure at the balloon's altitude. Semi-rigid balloons may have an internal and / or external support structure to help support the gondola beneath it. Rigid balloons have practically disappeared due to the complexity of their rigid structure and their inefficiency for smaller balloons because of the weight of this structure. Examples of lighter-than-air gases include helium, hydrogen, or a predetermined mixture of one or both of these gases with air.The first and second balloons 10a, 10b may each include one or more smaller balloons inside, adapted to be inflated or deflated with air to modify the volume and / or pressure of the balloons 10a, 10b, thus allowing control of the aerostat's attitude (its angles of attack and yaw) and its altitude. The connecting structure 30 serves to maintain the balloons relative to each other. For example, in the case of the two balloons 10a, 10b shown in figures 1 to 3, this connecting structure 30 holds the balloons in all directions X, Y and Z, and prevents any movement of these balloons relative to each other, for example under the action of external forces, in particular aerodynamic forces due to the advance of the aerostat or weather conditions (such as wind) or under the action of internal forces of the aerostat, such as propulsion forces of varying amplitude and / or directions.This connecting structure 30 also serves to stiffen the balloons themselves and limit their deformation, through the action of these same external forces. The connecting structure 30 of the aerostat 100 according to this disclosure comprises: - for each of the first and second balloons 10a, 10b, a first frame 31a of the first balloon 10a and a first frame 31b of the second balloon 10b respectively, and - a first cross member 32 which connects the first frame 31a of the first balloon 10a and the first frame 31b of the second balloon 10b in the lateral direction Y, said first cross member 32 fixing the position of the first and second balloons at least in the lateral direction Y. Each of the first frames 31a, 31b is connected to a balloon of said first and second balloons 10a, 10b, respectively; In other words, the first frame of the first ball has reference 31a, and the first frame of the second ball has reference 31b.Each of the first reinforcements 31a, 31b has substantially the shape of the envelope in a transverse plane YZ of the balloon to which the first reinforcement is connected, and this first reinforcement partially surrounds the envelope of the balloon in question on the outside. The first reinforcements 31a, 31b are generally the same length along each balloon and are preferably symmetrical with respect to a longitudinal plane XZ. The first reinforcements 31a, 31b are positioned in a first longitudinal position x1 in the longitudinal direction X. The first reinforcements 31a, 31b and the first cross member 32 are rigid elements, that is to say, much more rigid than the gas-filled balloons 10a, 10b, and are adapted to withstand mechanical stresses of compression or tension. They are, for example, made primarily of a steel-type material or composite or composite fibers (carbon fibers).The aerostat 100 optionally comprises, as shown in the figures: - for each of the first and second balloons 10a, 10b, a second frame 36a of the first balloon 10a and a second frame 36b of the second balloon 10b respectively, and - a second cross member 37 which connects the second frame 36a of the first balloon 10a and the second frame 36b of the second balloon 10b in the lateral direction Y, said second cross member 37 fixing the position of the first and second balloons at least in the lateral direction Y. These second frames 36a, 36b are also connected to a balloon of said first and second balloons 10a, 10b respectively; In other words, the second frame of the first balloon has reference 36a, and the second frame of the second balloon has reference 36b. These second reinforcements 36a, 36b may have identical or different shapes from the first reinforcements 31a, 31b.Specifically, they are substantially shaped like the envelope in a transverse plane YZ of the balloon to which the second frame is connected, and this second frame partially surrounds the outer envelope of the balloon in question. The first frames 31a, 31b are also generally the same length along each balloon and are preferably symmetrical with respect to the longitudinal plane XZ. Furthermore, the second frames 36a, 36b may have a different length from the first frames 31a, 31b around the balloon envelopes. The second frames 36a, 36b are positioned in a second longitudinal position x2 in the longitudinal direction X (Figure 3). The second frames 36a, 36b and the second cross member 37 are also rigid elements, that is, much more rigid than the gas-filled balloons 10a, 10b, and are adapted to withstand mechanical stresses of compression or tension.For example, they are mainly made of a steel-type material or composite or composite fibers (carbon fibers). Figure 4 shows a front view of a connecting structure 30 of the type shown in Figures 1 to 3 of the aerostat 100, allowing for a better illustration of the shape of this connecting structure 30. The first frames 31a, 31b, for example, have a shape that can be defined as a C-shape, a portion of a circle, or a portion of an arch. The first frame 31a is connected to the first balloon 10a, and the first frame 31b is connected to the second balloon. The first frames 31a, 31b are oriented in opposite directions, and an opening Oa, Ob of each first frame is oriented outwards from the aerostat 100 (relative to the center of the aerostat between the two balloons). The openings Oa, Ob of the first reinforcements are then suitable to accommodate respectively the first ball 10a and the second ball 10b.A body Ca, Cb of each first frame is oriented towards the interior of the aerostat 100, the bodies Ca, Cb of the first frames being connected by the first cross member 32. Each of the first frames 31a, 31b has essentially the shape of the envelope of the balloon to which it is connected in a transverse plane YZ. The envelope is, for example, inflated under pressure so as to make contact over at least a portion of the length of the frame 31a, 31b attached to said balloon. This contact is, for example, linear or surface contact over a majority or total portion of the length of the first frame 31a, 31b (curvilinear length of the C-shaped form). Thus, the balloon is held in compression within the first frame, which is much more rigid than the balloon under pressure. The balloons 10a, 10b are thus held firmly within the first frame 31a, 31b.The balloons 10a, 10b are thus stiffened by the first reinforcements 31a, 31b of the connecting structure 30: they are better able to maintain their overall shape, not only in a cross-section YZ, but also in a longitudinal section XZ or XY. The first C-shaped reinforcements 31a, 31b extend along an angular sector Sc (Figure 2) between 20 degrees and 270 degrees around the envelope of each balloon. This angular sector Sc is preferably between 90 degrees and 220 degrees to better support the balloons 10a, 10b by encircling their envelopes. The angular sector Sc of a first reinforcement 31a, 31b can extend over a first length along the upper portion 10as, 10bs of each balloon and a second length along the lower portion 10ai, 10bi. As illustrated in Figure 2, the angular sector Sc can extend mainly over the upper portion of a balloon.In this way, the balloon 10a, 10b is securely held at its upper portion, which absorbs a static lift force F1 generated by the gas, which is lighter than air. This static lift force F1 corresponds to the Archimedes' principle, oriented vertically in the direction Z, upwards. Thus, the balloon 10a, 10b is supported in the vertical direction Z upwards. In particular, the apex Sa, Sb of each balloon can advantageously be covered by the first reinforcements 31a, 31b. In other words, each first reinforcement extends at least to the apex Sa, Sb of each balloon. In this way, each balloon 10a, 10b is securely held at its upper portion 10as, 10bs, which absorbs a static lift force F1. Thus, each balloon 10a, 10b is supported in the vertical direction Z upwards.Each of the first reinforcements 31a, 31b is fixedly attached to a balloon 10a, 10b at a plurality of attachment points Fx1, Fx2, Fx3 (Figure 4), more than two, along the envelope of one of the balloons 10a, 10b, to distribute the fastening stress of the first reinforcement onto the envelope of that balloon. Thanks to this arrangement, the fastening stress at each attachment point can be less than a fastening strength limit, this fastening strength limit being a function of the nature of the balloon envelope and the gas pressure inside the balloon. For example, this plurality of attachment points makes it possible to achieve a fastening stress below the elastic limit of the envelope of the balloons 10a, 10b in order to obtain effective fastening at each attachment point and prevent any envelope tearing under operating conditions. This elastic limit of the envelope is, for example, between 50 MPa and 110 MPa.The plurality of attachment points Fx1, Fx2, Fx3 is, for example, greater than or equal to 3 and less than or equal to 5. This number of attachment points represents a good design compromise for the balloon casings used. Furthermore, each attachment point Fx1, Fx2, Fx3 may include a first or second reinforcement fastener At inserted between the balloon casing and an outer fastening layer that encapsulates said fastener. The outer layer is attached to the casing by a process of gluing, sewing, plastic welding, or a combination of these processes. The fastener At is attached to the first or second reinforcement, for example, by a mechanical means, such as a screw, bolt, cotter pin, or any other means. The second reinforcements 36a, 36b advantageously have shapes similar or identical to the first reinforcements 31a, 31b and according to embodiments and variants that may be similar or identical.According to variants of the connection structure 30 of the aerostat 100, the characteristics of which are shown in Figure 2, this connection structure 30 may further comprise: - a first lower rod 33a directly or indirectly connecting a lower point Pia of the first frame 31a of the first balloon 10a and the first cross member 32, and - a second lower rod 33b directly or indirectly connecting a lower point Pib of the first frame 31b of the second balloon 10b and the first cross member 32. By "direct or indirect connection," it is understood that each rod may be directly connected to the first cross member 32 or indirectly by another structure itself connected to the first cross member 32, such as a gondola 50, as shown in the figures. These rods 33a, 33b are substantially linear elements, extending between two points to mechanically connect them.The rods 33a and 33b are, for example, rigid bars adapted to withstand compressive or tensile mechanical stresses. They are, for example, primarily made of steel, composite materials, or composite fibers (carbon fibers). These rods may also be cables adapted to withstand only tensile stresses. They are, for example, primarily made of steel wire or synthetic material. The first lower rod 33a and the second lower rod 33b are rigid, elastic, or elastic with damping. These rods can be extendable and equipped with extension stops, and optionally equipped with a damper. The first lower rod 33a and the second lower rod 33b stiffen the connecting structure 30 of the aerostat.In particular, such rods positioned in the lower portion of each balloon operate in tension under the action of a static lift force F1 generated by the Archimedes' buoyancy of the gas in the balloons, which corresponds to a principal force for the connecting structure 30. According to variants of the connecting structure 30 of the aerostat 100, the connecting structure 30 may include: - a first upper rod 34a directly or indirectly connecting a higher point Psa of the first frame 31a of the first balloon 10a and the first cross member 32, and - a second upper rod 34b directly or indirectly connecting a lower point Pib of the first frame 31b of the second balloon 10b and the first cross member 32. These upper rods 34a, 34b are of the same type as the lower rods 33a, 33b or different. These rods are optional because, under the action of the Archimedes' principle of buoyancy from the balloon gas, they operate in compression.However, these upper rods improve the rigidity of the connecting structure 30. According to variants of the connecting structure 30, a connecting member 32a, 32b establishes a connection between the first frame 31a, 31b and the first cross member 32. This connecting member 32a, 32b provides: - either a rigid fixed connection so that the first frames 31a, 31b are firmly attached to the cross member 32, - or a hinged connection allowing angular movement between the first frames 31a, 31b and the cross member 32. The aerostat 100 may also include a tail assembly 40 connecting the first balloon 10a and the second balloon 10b. This tail assembly 40 is for example located in a longitudinal tail assembly position xe in the longitudinal direction X, corresponding for example to the tail 102 of the aerostat 100.The longitudinal position of the tail assembly xe differs from the first longitudinal position x1 of the first frames 31a, 31b of the connecting structure 30. This tail assembly 40 includes a horizontal stabilizer 41 capable of providing an aerodynamic lift component. Preferably, the aerodynamic lift component of this tail assembly 40 is high when the aerostat is moving forward, enabling it to glide like an airplane with wings. The horizontal stabilizer 41 includes an elevator. The tail assembly 40 further includes a vertical stabilizer 42 equipped with a rudder. Advantageously, the tail assembly 40 of the present aerostat 100 helps to stabilize the aerostat 100, in particular to limit pitching or nose-up movements.Furthermore, this tail assembly 40 can be capable of generating high lift, thanks to the horizontal stabilizer 41, and for example, thanks to the large surface area and possibly the aerodynamic profile of this horizontal stabilizer 41. The aerostat 100 advantageously includes a first propulsion device 35, such as one or more propeller engines or jet-type engines (for example, small ones). In one variant, the first propulsion device 35 can be located on the tail assembly 40. In another variant shown in the figures, the first propulsion device 35 is advantageously located on the first crossmember 32 of the aerostat 100.This first propulsion device 35 is preferably orientable by pivoting about a lateral axis Y to be angularly oriented between: - a horizontal propulsion position in which the first propulsion device 35 is capable of generating a propulsion force in the longitudinal direction X, and - a vertical propulsion position in which the first propulsion device 35 is capable of generating a propulsion force in the vertical direction Z. In the vertical propulsion position, or in an intermediate position between the horizontal and vertical propulsion positions, the first propulsion device 35 is then capable of generating vertical lift sufficient to raise the aerostat 100 upwards in the vertical direction Z. The first propulsion device 35 may comprise two motors as shown in the figures, pivotally mounted on the cross member 32.Each engine is, for example, located on either side of the nacelle 50, said nacelle 50 being situated between the two balloons 10a, 10b. The two engines can be steered independently of each other. The aerostat 100 optionally includes a second propulsion device 38 of the same type as the first propulsion device 35, or of a different type. This second propulsion device 38 is advantageously located on the second cross member 37, particularly in the case where the connecting structure 30 of the aerostat includes a second frame 36a, 36b and a second cross member 37 as shown in the figures. The second propulsion device 38 can be steered like the first propulsion device 35, and it can also include two engines, for example, located on either side of the nacelle 50. Thus, as shown in the figures, the nacelle 50 is, for example, connected at least to the first cross member 32.It will be understood that the solution illustrated in the figures, an aerostat 100 with four steerable engines, provides a propulsion and orientation capacity with a very advantageous thrust force, similar to a quadcopter drone. The two balloons 10a and 10b then provide additional lift of the Archimedes type thanks to the lighter-than-air gas inside said balloons. The aerostat 100, as described herein, has other technical features for its operation, which we will now describe in detail. These features are very advantageous, particularly for ensuring a high degree of safety for its occupant or the cargo being transported.We assume here that the aerostat 100 corresponds to the preceding description, and that this aerostat 100 comprises: - a first balloon 10a and a second balloon 10b extending in a longitudinal direction X, each balloon consisting of an envelope containing a gas lighter than air, - a connecting structure 30 configured to maintain the first and second balloons relative to each other. The aerostat 100 further comprises: a tail assembly 40 connecting the first and second balloons in a longitudinal tail assembly position xe in the longitudinal direction X, and at least one first propulsion device 35, orientable by pivoting about a lateral axis Y to be angularly oriented between a horizontal propulsion position and a vertical propulsion position.The aerostat 100 is suspended in the air at an altitude thanks to a total lift St in the upward vertical direction Z, adapted to compensate or balance the weight P in the downward vertical direction Z. This total lift St for the aerostat in question is the sum of: - a static lift F1 generated by the lighter-than-air gas of the first balloon 10a and the second balloon 10b, - a vertical propulsion lift F2 corresponding to a vertical component of the propulsion force generated by the first propulsion device 35, and - an aerodynamic lift F3 which is a function of the shape of the aerostat 100 including the first balloon 10a, the second balloon 10b and the tail assembly 40, and which is also a function of the angle of incidence of the aerostat 100, and the speed v of the aerostat 100 in the environment.This decomposition of the total lift force St is schematically represented in Figure 6, which illustrates such an aerostat 100 in hover. This figure is a longitudinal section in the XZ plane to visualize the gondola 50 between the two balloons 10a and 10b. The points of application of these lift forces have been displaced within the XZ plane for visualization, but the weight P, or gravitational force of the aerostat 100, is applied at the center of gravity G of the aerostat. The static lift force F1 corresponds to the Archimedes' thrust directed vertically upwards in the Z direction. This static lift F1 can be calculated by: F1 = V.ρ.g where V is the volume of gas in the balloons, ρ is the mass density of the air surrounding the aerostat 100 at its altitude, and g is the value of gravity (usually g = 9.81 m / s²).The weight or gravitational force P is a force directed in the opposite direction to the vertical direction Z, that is, downwards (towards the ground), and it is equal to: P = mg, where m is the total mass of the aerostat 100, and g is the value of gravity (usually g = 9.81 m / s²). The effective weight Pe is defined as: Pe = (m - V.ρ).g = Ls.g, where the component (m - V.ρ) = Ls is often called the static heaviness or aerostatic balance (or "static heavinees" in English). This is the difference between the total mass m of the aerostat 100 and the volume of gas V in the balloons multiplied by the density ρ of the air surrounding the aerostat at its altitude. The total lift St is then: St = F1 + F2 + F3. For flight at constant altitude, the total lift St must be equal in magnitude (in the opposite direction) to the gravitational force P (force equilibrium). If the total lift St is less than the gravitational force P, the aerostat 100 is descending.If the total lift St is greater than the gravitational force P, the aerostat 100 rises in altitude. In other words, the effective weight Pe is compensated by the vertical propulsion lift F2 and / or the aerodynamic lift F3. The aerostat 100 then has the following characteristics: 1) the shape of the aerostat is configured so that the aerostat has a glide ratio Fi greater than 2, which allows it to glide easily, 2) the first and second balloons 10a, 10b contain a volume of gas so that the static lift F1 is strictly greater than 50% of the total lift St, 3) the first propulsion device 35 is configured so that the vertical propulsion lift F2 can be strictly greater than 50% of the effective weight Pe of the aerostat 100, in the vertical propulsion position of the first propulsion device 35. Thanks to these arrangements, the aerostat 100 has extended flight capabilities at altitude.Indeed, it can ascend to a higher altitude than other aerostats. The Aerostat 100 can hover or maintain a constant altitude. The static lift (F1) and vertical propulsion lift (F2) of the Aerostat 100 ensure hovering. The static lift (F1) and aerodynamic lift (F3) ensure constant altitude flight. Furthermore, the Aerostat 100 is very safe and capable of maintaining lift even in the event of a major malfunction or damage. If the static lift F1 is lost by partial or total gas loss of the first balloon 10a and / or the second balloon 10b, the aerostat 100 is capable of descending at a low speed to ensure the survival of the occupant or to ensure the integrity of a payload of the aerostat 100.Specifically, the first propulsion device 35 is capable of providing vertical propulsion lift F2 to at least partially compensate for the loss of static lift F1. For example, the first propulsion device 35 will shift into a vertical propulsion position to provide this compensation. If the vertical propulsion lift F2 becomes zero due to a loss of power in the first propulsion device 35, the aerostat 100 is capable of gliding in descent to ensure the survival of the occupant or to maintain the integrity of a payload on the aerostat 100. Indeed, the lift-to-drag ratio Fi of the aerostat 100 and the gas volumes of the first and second balloons 10a, 10b allow for this capability. The aerodynamic lift-to-drag ratio Fi of an airplane or aerostat is the ratio between the lift Cz and the drag Cx, that is: Fi = Cz / Cx.In unpowered gliding flight, the glide ratio (Fi) is also the ratio between the horizontal distance traveled (Dh) and the vertical descent height (Hv), or the ratio between the horizontal speed (Vh) and the vertical speed (Vv) (rate of descent), that is: Fi = Dh / Hv = Vh / Vv. The glide ratio (Fi) of the aerostat 100 is advantageously greater than 2. Thus, the aerostat 100 has a shape configured to achieve this glide ratio. The aerostat 100 is therefore capable of gliding. The aerostat's glide ratio (Fi) can also be greater than 3 due to its shape, in order to have improved unpowered flight capabilities. The aerostat 100, comprising a first balloon (10a) and a second balloon (10b), inherently has a fairly high drag compared to an airplane or a glider. However, the aerostat 100 can also have a very high lift coefficient (Cl), compensating for this drag to obtain an adequate glide ratio. The fineness ratio Fi of the aerostat 100 can be less than 10 or less than 7.According to one variant, the first and second balloons 10a, 10b contain a total gas volume such that the static lift F1 is greater than 70% of the total lift St. Thus, the aerostat 100 is safer in the event of a power loss in the first propulsion device 35. According to another variant, the first propulsion device 35 has sufficient power to ensure that the vertical propulsion lift F2 is greater than 70% or even greater than 100% of the effective weight Pe of the aerostat 100, in the vertical propulsion position of the first propulsion device 35. The aerostat 100 thus develops an improved propulsion lift capacity. The aerostat 100 advantageously includes a control unit UC. This control unit is integrated into the aerostat 100 and, for example, into the gondola 50. According to one variant, the control unit UC detects a loss of gas and measures a descent speed vd of the aerostat 100.The control unit UC can then command the orientation of the first propulsion device 35 with a propulsion angle towards the vertical propulsion position and sufficient power from the first propulsion device 35 to ensure that the descent speed vd is less than a predetermined first descent speed limit V1. The first descent speed limit V1 is, for example, less than 10 m / s. Thus, the control unit UC ensures the survival of the occupant of the gondola 50 or the integrity of a payload on the aerostat 100. Optionally, the first descent speed limit V1 is less than 5 m / s or even less than 1 m / s to better ensure survival or integrity. This first descent speed limit V1 can be set in the control unit UC. In one variant, the control unit UC detects the loss of propulsion in the first propulsion device 35 and measures a descent speed vd of the aerostat.The control unit UC can then control the total gas volume of the first and second balloons 10a, 10b and can control the angle of attack Ai of the aerostat so that the descent speed vd is less than a predetermined second limiting descent speed V2. The second limiting descent speed V2 is, for example, less than 10 m / s. Thus, the control unit UC ensures the survival of the occupant of gondola 50 or the integrity of a payload in the aerostat 100. Optionally, the second limiting descent speed V2 is less than 5 m / s or even less than 1 m / s to better ensure survival or integrity. This second limiting descent speed V2 can be set in the control unit UC. In one variant, the control unit UC detects the loss of propulsion in the first propulsion device 35 and measures a descent speed vd of the aerostat.The control unit UC can then authorise the removal of at least one weighting device from the aerostat 100. For example, the weighting device is the first propulsion device 35 or an auxiliary device of the first propulsion device 35 such as a fuel tank or batteries or a carried load.Partial Nomenclature 100 Aerostat 34a First upper rod 101 Nose 34b Second upper rod 102 Tail 35 First propulsion device 10a First balloon 36a Second frame of the first balloon 10as Upper portion 36b Second frame of the second balloon 10ai Lower portion 37 Second cross member 10b Second balloon 37a Connecting element of the first balloon 10bs Upper portion 37b Connecting element of the second balloon 10bi Lower portion 38 Second propulsion device 11 Horizontal fin 40 Empennage 12 Vertical fin 41 Horizontal stabilizer 30 Connecting structure 42 Horizontal stabilizer 31a First frame of the 50 Gondola of the first balloon 31b First frame of the UC Control unit of the second balloon 32 First cross member 32a Connecting element of the first balloon 32b Connecting element of the second balloon 33a First lower rod 33b Second lower stem.

Claims

CLAIMS 1. Aerostat (100) comprising: - a first balloon (10a) and a second balloon (10b) extending in a longitudinal direction (X), each balloon being made up of an envelope containing a gas lighter than air, - a connecting structure (30) configured to maintain the first balloon and the second balloon relative to each other, the aerostat being characterized in that the connecting structure (30) comprises: for each of the first and second balloons, a first frame (31a, 31b) connected to a balloon of said first and second balloons, each of the first frames (31a, 31b) having substantially the shape of the envelope in a transverse plane (YZ) of said balloon to which the first frame is connected, and partially surrounding this envelope externally, said first frames being positioned in a first longitudinal position (x1) in the longitudinal direction (X),and - a first cross member (32) which connects the first frame of the first balloon and the first frame of the second balloon in the lateral direction (Y), said first cross member (32) fixing the position of the balloons in the lateral direction (Y).

2. Aerostat according to claim 1, in which the first frames (31a, 31b) are C-shaped, the first frame (31a) connected to the first balloon (10a) and the first frame (31b) connected to the second balloon are oriented in opposite directions, an opening (Oa, Ob) of each first frame being oriented outwards from, the aerostat to accommodate the first and second balloons (10a, 10b) respectively, a body (Ca, Cb) of each first frame being oriented towards the interior of the aerostat to be connected by the first cross member (32).

3. Aerostat according to claim 2, wherein the first C-shaped frames (31a, 31b) extend in an angular sector of between 20 degrees and 270 degrees around the envelope of each balloon.

4. Aerostat according to any one of claims 1 to 3, wherein an upper end zone (ZS) of each balloon is covered by said first frames in order to support said first and second balloons in an upward vertical direction (Z). 5.Aerostat according to any one of claims 1 to 4, wherein each of the first armatures (31a, 31b) is fixedly attached to a balloon (10a, 10b) at a plurality of attachment points (Fx1, Fx2, Fx3), in a number greater than 2, along said balloon, to distribute a fastening stress of the first armature on the balloon envelope.

6. Aerostat according to claim 5, wherein the plurality of attachment points is in a number greater than or equal to 3 and less than or equal to 5.

7. Aerostat according to claim 5 or 6, wherein each attachment point comprises a first armature attachment inserted between the envelope and an external fastening layer enclosing said attachment, and said external layer being fixed to the envelope by a method of gluing, sewing, plastic welding, or a. combination of these methods.

8. Aerostat according to any one of claims 1 to 7, wherein the connecting structure (30) further comprises: - a first lower rod (33a) directly or indirectly connecting a lower point (Pia) of the first frame (31a) of the first balloon (10a) and the first cross member (32), and - a second lower rod (33a) directly or indirectly connecting a lower point (Pib) of the first frame (31b) of the second balloon (10b) and the first cross member (32).

9. Aerostat according to claim 8, wherein the first lower rod (33a) and the second lower rod (33b) are rigid, elastic, or elastic with damping.

10. Aerostat according to any one of claims 1 to 9, wherein a connecting member (32a, 32b) provides a rigid fixed connection between the first frame (31a, 31b) and the first cross member (32) or a hinged connection between the first frame (31a, 31b) and the first cross member (32). 11.Aerostat according to any one of claims 1 to 10, further comprising a tail assembly (40) connecting the first balloon and the second balloon in a longitudinal tail position (xe) in the longitudinal direction (X), said longitudinal tail position (xe) being different from the first longitudinal position (x1).

12. Aerostat according to any one of claims 1 to 11, in. wherein the first cross member (32) is equipped with a first propulsion device (35).

13. Aerostat according to claim 12, wherein the first propulsion device (35) is pivotable about a lateral direction axis (Y) to be angularly oriented between a horizontal propulsion position and a vertical propulsion position. 14.Aerostat according to any one of claims 1 to 13, wherein the connecting structure (30) comprises: for each of the first and second balloons, a second frame (36a, 36b) connected to a balloon of said first and second balloons, each of the second frames (36a, 36b) having substantially the shape of the envelope in a transverse plane (YZ) of said balloon to which said second frame is connected, and partially surrounding this envelope externally, said second frames being positioned in a second longitudinal position (x2) in the longitudinal direction (X), different from the first longitudinal position (x1), and - a second cross member (37) which connects the second frame of the first balloon and the second frame of the second balloon in the lateral direction (Y), said second cross member (37) fixing the position of the balloons in the lateral direction (Y).

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