Self-eating hybrid rocket engine

Abstract

The present invention relates to a jet propulsion system provided with a hybrid rocket engine and, more specifically, to the storage of the fuels before they are introduced into the combustion chamber. This propulsion system is made up of a combustion chamber (1) closed by a cap (2) and a valve (3). A solid propellant (4) is used as a tank for a liquid propellant (5). These two propellants are introduced into the chamber (1) in order to be burned therein. The gases produced by this combustion are discharged via a nozzle (6) in order to provide a propulsive thrust. The system is a self-eating system in that it burns its own structure in order to launch. The propulsion system described by the present invention is particularly intended for propelling space vehicles and launchers.

Description

[0001]Self-consuming hybrid rocket engine Technical field The present invention relates to a jet propulsion system, in particular for a space launcher, equipped with a hybrid rocket engine and more precisely, the storage of propellants before being inserted into a combustion chamber. Chemical jet rocket engines expel fluids resulting from a reaction between several propellants through a nozzle to create thrust allowing movement of the propulsion system and its payload. In the case of hybrid rocket engines, at least one propellant is solid and at least one propellant is fluid. State of the prior art In the current state of the art, the storage of propellants for rocket engines depends on the nature of the propellant. Solid propellants are stored directly in the combustion chamber and fluid propellants are stored in tanks of fixed geometry.When the propulsion system is in flight, the fluid propellant tanks empty and gradually become an unnecessary burden that reduces the performance of the overall system. The empty tanks can also be detached from the propulsion system. In this case, they constitute detritus in space, thus gradually cluttering up the space. Disclosure of the invention The present invention proposes a solution to free oneself from the constraints linked to the tanks of the propulsion system and to increase the performance of the propulsion system. To do this, the invention proposes to replace the propulsion systems comprising tanks with a propulsion system equipped with autophagic storage. More specifically, the present invention comprises a hybrid rocket engine as described in the appended claims. The detailed description which follows, as well as the accompanying drawings, will allow a better understanding of the nature and advantages of the present invention.Brief description of the figures Figure 1 schematically describes a self-consuming hybrid rocket engine according to the present invention. Figure 2 represents an exemplary embodiment of the invention, in which the hollow solid propellant, in particular the solid propellant grain, is driven into the combustion chamber via a screw-nut system. Detailed description The present invention relates to a hybrid rocket engine equipping a jet propulsion system. A hybrid rocket engine is a rocket engine using at least one fluid propellant and at least one solid propellant. According to the present invention, the hybrid rocket engine comprises a combustion chamber supplied with a hollow solid propellant and a fluid propellant, the hollow solid propellant having a cavity closed by a plug and a valve, and the fluid propellant being stored in the cavity of the hollow solid propellant.Furthermore, the hollow solid propellant may comprise a first portion inserted into the combustion chamber to be burned therein with fluid propellant injected into the combustion chamber through the valve. The combustion will generate hot gases which will escape through a nozzle so as to produce thrust. In particular, the first portion may comprise an internal face towards the combustion space to be burned. The hollow solid propellant may further comprise a second portion which extends out of the combustion chamber and contains the fluid propellant before both being inserted into the combustion chamber.Furthermore, another aspect of the present invention relates to a hybrid rocket engine in which a pressurized combustion chamber closed by a plug and a valve contains a hollow solid propellant whose inner face burns with a fluid propellant injected through the plug, generating hot gases escaping through a nozzle so as to produce thrust on the vehicle. A portion of the hollow solid propellant protrudes around the plug from the combustion chamber and contains the fluid propellant before both are inserted into the combustion chamber. In other words, a portion delimited by the plug of the hollow solid propellant serves as a container for the fluid propellant before both are inserted into the combustion chamber.Thus, by using a hollow solid propellant as a hollow structure in the form, for example, of any hollow cylinder, which makes it possible to store the fluid propellant, the present invention makes it possible to free oneself from the constraints linked to the tanks of the propulsion system and to increase the performance of the latter. In particular, the hollow solid propellant is a grain of solid propellant having a hollow structure formed from a solid propellant. The hollow solid propellant therefore has a rigid and hollow structure and thus forms a tank whose walls are made of the solid propellant itself. In particular, the hollow solid propellant comprises a cavity, the cavity containing the fluid propellant and being closed by the plug and the valve. The hollow solid propellant is for example formed from a homogeneous structure of solid propellant. The hollow solid propellant may also be formed mainly from solid propellant and may comprise additives or other components (for example, ammonium perchlorate).A solid propellant is in particular a non-high energy propellant such as for example polyethylene or ABS (Acrylonitrile Butadiene Styrene). The hollow solid propellant is used to contain the fluid propellant intended to be burned in the combustion chamber. In other words, the cavity formed in the hollow structure of the hollow solid propellant serves as a container for the fluid propellant. A fluid propellant may be an oxidizer and may be for example a liquid cryogenic oxidizer. According to one embodiment, no container or tank or additional structure is necessary to contain the hollow solid propellant. Thus, no rigid envelope such as a rigid tank is necessary to encase the hollow solid propellant. However, a coating may coat the hollow solid propellant in order to increase the rigidity of the hollow solid propellant. The cavity formed in the hollow solid propellant is closed by the plug and the valve, the plug being able to comprise the valve.The cavity comprises for example a constant and regular diameter, for example tubular in shape, and the plug has a diameter corresponding to the diameter of the cavity. According to one embodiment, the plug and the valve are not located at the end of the hollow solid propellant but are located inside the hollow solid propellant so as to close the cavity at a given depth. In other words, the plug and the valve close the cavity so as to form a first portion of hollow solid propellant downstream of the plug. Downstream of the plug is the portion located outside the cavity closed by the plug. This portion of hollow solid propellant is inserted into the combustion chamber to be burned there. A second portion of hollow solid propellant located upstream of the plug and the valve serves as a container for the fluid propellant. The second portion of propellant extends in particular outside the combustion chamber.In particular, the plug may be used to delimit the portion of hollow solid propellant intended to contain the fluid propellant from the portion of hollow solid propellant intended to burn in the combustion chamber. The cavity formed in the hollow solid propellant has, for example, any cylinder shape. According to the present invention, the hollow solid propellant forming the reservoir of the fluid propellant comprises the solid propellant used during combustion to create thrust in the combustion chamber. The hollow solid propellant may be in the shape of a straight cylinder with a bottom, a straight prism or any other simple or complex shape, provided with a cavity comprising an opening capable of being closed by a plug. The plug may also comprise an injector, downstream of the valve in order to introduce the fluid propellant contained in the cavity into the combustion chamber.According to a particular embodiment, the hollow solid propellant may be coated, in particular on its external surface, with a coating making it possible to improve the sliding of the hollow solid propellant inside the wall(s) of the combustion chamber. The coating may be, for example, polytetrafluoroethylene. The hollow solid propellant may further comprise one or more additives, such as polytetrafluoroethylene, to improve the chemical compatibility of the solid propellant with the fluid propellant or to improve the regression speed during combustion. Furthermore, given the rigidity of the hollow solid propellant, and in particular of the solid propellant grain, the latter also serves to transmit the thrust forces from the nozzle to the payload of the propulsion system.According to one embodiment, inside the hollow solid propellant, and in particular the solid propellant grain, there is a plug equipped with a valve and for example an injector, which serves to delimit the part of the hollow solid propellant, and in particular the solid propellant grain, intended to contain the fluid propellant from the part of the hollow solid propellant, and in particular the solid propellant grain, intended to burn in the combustion chamber. The combustion chamber is the pressurized location where the combustion of the two propellants together takes place. Combustion is a chemical reaction of the two propellants which produces high-temperature combustion gases which are ejected through a nozzle, in a direction opposite to the direction of the desired movement of the payload of the propulsion system.According to one aspect of the invention, the combustion chamber is closed by a plug and a valve and contains a hollow solid propellant whose inner face burns with a fluid propellant injected through the plug. The chamber may further be closed by the hollow solid propellant inserted into the combustion chamber. The inner face of the hollow solid propellant is in particular the surface of the hollow solid propellant located in the combustion chamber downstream of the plug. In addition, the nozzle is an opening in the combustion chamber which allows the hot gases produced during the combustion of the propellants to escape so as to propel the payload of the propulsion system. The combustion chamber may comprise a wall of a shape complementary to the shape of the hollow solid propellant so that the latter is inserted into the combustion chamber and slides on the wall(s) of the chamber as it burns.The wall(s) of the combustion chamber thus form a receptacle for receiving a first portion of the hollow solid propellant, a second portion of the hollow solid propellant containing the fluid propellant extending out of the combustion chamber before both being inserted into the combustion chamber. According to one embodiment, the combustion chamber is partly delimited by the first portion of hollow solid propellant and the plug. Furthermore, the plug may hermetically close the cavity formed in the hollow solid propellant, the valve serving to circulate the fluid propellant from the cavity to the combustion chamber. The rocket engine may comprise one or more propellant insertion systems for inserting the hollow solid propellant, and in particular the solid propellant grain, into the combustion chamber and for moving the plug as the hollow solid propellant, and in particular the solid propellant grain, having a shape that may be cylindrical, burns.The propulsion system according to the invention is self-consuming in the sense that it consumes its own structure. Indeed, the hollow solid propellant is gradually introduced inside the combustion chamber as the hollow solid propellant is consumed. When the hollow solid propellant enters the combustion chamber, the storage volume of the fluid propellant decreases. Indeed, the propellant insertion system(s) creates a displacement of the hollow solid propellant in the combustion chamber as combustion progresses, the cavity closed by the plug and storing the fluid propellant decreases. By compression, in particular of the plug in the cavity storing the fluid propellant, the fluid propellant is therefore also forced, via the valve, into the combustion chamber. A single propellant insertion system may be sufficient to force both propellants into the chamber.According to a particular embodiment, the rocket engine further comprises a means for connecting at least one wall of the combustion chamber to the plug in order to mechanically connect the plug to the combustion chamber. The mechanical connection can maintain the plug in a certain position relative to the combustion chamber while allowing movement, for example a rotational movement, of the plug. Alternatively, the plug can be maintained in a fixed position by the connection means in the rocket engine. The connection means can comprise at least one knife mechanically connecting said at least one wall of the combustion chamber to the plug. In this case, the mechanical connection is a knife in the sense that the first portion of the hollow solid propellant inserted into the combustion chamber is traversed at least in part by said at least one knife during insertion.In particular, since the hollow solid propellant is subjected to high internal pressure when it is inserted into the combustion chamber, it is easily crossed by the knives as the solid propellant grain penetrates into the combustion chamber. Indeed, the knives cut the solid propellant grain, in particular in the direction of insertion of the solid propellant grain. The knife or knives passing through the hollow solid propellant also have the effect of preventing rotational movement of the hollow solid propellant. In other words, the connection means also has a function of stopping rotation of the hollow solid propellant. The knife or knives mechanically connecting the plug to the wall or walls of the combustion chamber, they cut the hollow solid propellant at the speed of introduction of the hollow solid propellant into the combustion chamber.When the plug is mechanically connected to the wall(s) of the combustion chamber by means of several knives, the latter may be of different lengths. Indeed, the knives may mechanically connect the plug with the wall(s) of the combustion chamber at different heights in the combustion chamber. According to another embodiment, the knives may be of the same length. The rocket engine may further comprise a propellant insertion system which will manage the insertion of the solid propellant grain into the combustion chamber as well as the introduction of the fluid propellant into the combustion chamber. The insertion system may comprise a means for generating a translational movement of the hollow solid propellant, in order to insert it into the combustion chamber as combustion progresses. The propellant insertion system may be connected to the plug.According to another embodiment, the plug may comprise the propellant insertion system. The means for generating a translational movement of the hollow solid propellant is capable of generating a translational movement of the hollow solid propellant relative to the wall(s) of the combustion chamber and / or relative to the plug. For example, it may (or may not) be imaginable that a propellant insertion system is located at the plug, and that the plug is mechanically connected to the chamber, thus moving at the same speed inside the hollow solid propellant and in particular the solid propellant grain. For example, the plug and the combustion chamber may be connected by a certain number of knives. If necessary, the hollow solid propellant and in particular the solid propellant grain, already subjected to high internal pressure, is easily cut by the knives as it penetrates the chamber.In particular, the means for generating a translational movement of the hollow solid propellant may, for example, be implemented by means of a screw-nut type system. The means for generating a translational movement of the hollow solid propellant may comprise a screw capable of being rotated in a thread forming a face of the hollow solid propellant so as to apply a force to insert it into the combustion chamber. The thread forming a face of the hollow solid propellant may, in particular, form the internal face of the hollow solid propellant. For example, the hollow solid propellant may comprise a thread on the internal wall of the cavity in order to interface with a screw formed around the plug. The thread is obtained, for example, by tapping. The plug closing the cavity may comprise a screw pitch complementary to the thread located on the internal wall of the cavity.According to another embodiment, the screw is connected to the plug but the rotation of the screw does not cause a rotational movement of the plug. A mechanical system for inserting the grain may for example be composed of a screw-nut system in which the hollow solid propellant, in particular the solid propellant grain, has an internal thread which interfaces with a screw around the plug. According to a particular embodiment, the hollow solid propellant may be coated with a coating allowing a reduction in the friction of the screw when the latter interfaces with the screw thread making up a face of the hollow solid propellant. The coating may for example be polytetrafluoroethylene.The rocket engine may further comprise a mechanical rotation system such as an electric motor powered by batteries, fuel cells, gas generator or any other source of electricity that allows the screw to rotate, thus driving the hollow solid propellant and in particular the solid propellant grain, in translation. A turbine using the combustion gases, or any other system may also be considered to drive the screw or the plug provided with a screw thread. Thus, the propellant insertion system allows the combustion chamber to be supplied with hollow solid propellant and the compression of the plug in the cavity caused by the movement of the hollow solid propellant allows the introduction of the fluid propellant into the combustion chamber via the valve. In this particular embodiment based on the screw-nut system, the propellant insertion system manages the rotation of the screw which will rotate relative to the hollow solid propellant.This screw and nut system makes it possible to transform the rotational movement of the screw into a translational movement of the hollow solid propellant moving the hollow solid propellant in the combustion chamber. The hollow solid propellant also moves in translation relative to the plug. This translational movement of the hollow solid propellant implies a reduction in the size of the cavity since the plug does not undergo such a translation in the combustion chamber. Thus, the pressure on the fluid propellant will increase in the cavity closed by the plug. According to another embodiment, the screw nut system is reversed between the hollow solid propellant and the plug. In other words, the hollow solid propellant can comprise the screw and the nut can be formed by the combustion chamber or the plug. The rotational stopping of the grain in the screw-nut system can be achieved with the knives previously described or another rotational stopping system, whatever it may be.The screw rotation system could also be useful for driving a pump that would serve to increase the pressure of the fluid propellant between the tank and the combustion chamber. Indeed, in this case, the pump driven by the rotation system makes it possible to increase the pressure of the fluid propellant contained in the cavity with a view to its introduction into the combustion chamber. The characteristics of the solid grain can be adapted by using coatings, additives or a particular micro-structure. For example, a layer of polytetrafluoroethylene can also be applied to the hollow solid propellant, in particular to the solid propellant grain, to allow it better chemical compatibility with the fluid propellant, better sealing in the thread or reduced friction with the screw or the wall of the combustion chamber.The hollow solid propellant, in particular the solid propellant grain, can also be composed of several materials: the external envelope, in the form of a coating of the hollow solid propellant, in particular the solid propellant grain, can be made of a thermal ablative material which releases cold gases when pyrolyzed, which would serve to insulate the walls of the combustion chamber and the nozzle. It is also possible to consider using composite materials as hollow solid propellant, in particular solid propellant grain, or to produce it by an additive manufacturing process. Figure 1 illustrates an embodiment of the invention in the case of a hybrid rocket engine. According to an exemplary embodiment, the propellants used by the hybrid rocket engine are respectively a liquid cryogenic oxidizer and a solid fuel at room temperature, but the invention can be implemented with other combinations of propellants.Figure 1(a) illustrates a hybrid rocket engine which comprises a hollow solid propellant, in particular a solid propellant grain, and a fluid propellant to be consumed to achieve the thrust necessary to move the payload of the propulsion system while Figure 1(b) illustrates the hybrid rocket engine in which the majority of the hollow solid propellant, in particular the solid propellant grain, and the fluid propellant has been consumed in order to illustrate the autophagic aspect of the propulsion system. The combustion chamber 1, capable of withstanding the pressure within it, is closed by a plug 2 and a valve 3 which delimit two parts in the hollow solid propellant, in particular the solid propellant grain 4: the zone intended for combustion at the level of the combustion chamber 1 and the zone intended for the storage of the fluid propellant 5.The combustion chamber 1 is delimited in particular by a wall 1a connected to a nozzle 6 in order to eject the combustion gases and allow propulsion by thrust of the charge using the propulsion system. The combustion chamber also comprises, opposite the nozzle, an opening capable of receiving a portion of the hollow solid propellant, in particular the solid propellant grain 4, having a cavity for storing a fluid propellant 5. This opening is closed by the plug and the valve. As illustrated, the plug and the valve also serve to close the cavity of the hollow solid propellant 4. The plug may comprise the valve. The cavity comprises, for example, a constant and regular diameter, such as, for example, a tube, and the plug has a diameter corresponding to the diameter of the cavity.In the illustrated embodiment, the outer face of the hollow solid propellant 4 is of a complementary shape to the wall 1a of the combustion chamber 1 in order to be introduced into the chamber 1 as the solid propellant and the fluid propellant are consumed. The fluid propellant 5 can enter the combustion chamber via the valve 3, for example when pressure is exerted by the cap on the fluid propellant in the cavity of the hollow solid propellant. As illustrated in FIG. 1, the portion of the hollow solid propellant located between the cap and the wall of the combustion chamber 1a is used for combustion. In addition, the portion of the solid propellant located above the combustion chamber serves as a container for the fluid propellant before both being introduced into the combustion chamber 1.Thus, as the hollow solid propellant located in the combustion chamber and the fluid propellant are used, the two propellants located upstream of the combustion chamber are inserted into the combustion chamber in order to be consumed, thus reducing the size of the propulsion system until the majority of the hollow solid propellant and the fluid propellant is consumed as illustrated in Figure 1(b). Combustion is achieved by burning the hollow solid propellant located in the combustion chamber and the fluid propellant 5 introduced into the combustion chamber. By entering the combustion chamber 1 and burning with the hollow solid propellant, in particular the solid propellant grain 4, the fluid propellant 5 generates combustion gases which are then ejected by the nozzle 6 which allows the jet propulsion of the system. Combustion is a chemical reaction of the two propellants to produce gases used for thrust.The portion of hollow solid propellant located in the combustion chamber 1 may comprise a decreasing thickness as illustrated in Figure 1. In other words, the surface of the propellant that is burned, namely the internal face of the hollow solid propellant, may be approximately cone-shaped. Figure 2 represents an exemplary embodiment of the hybrid rocket engine of the invention, in which the hollow solid propellant is driven into the combustion chamber via a propellant insertion system. The propellant insertion system illustrated in Figure 2 is based on a screw-nut type system. Figure 2(a) illustrates the hybrid rocket engine containing a hollow solid propellant and a fluid propellant to be consumed while Figure 2(b) illustrates the hybrid rocket engine in which the majority of the hollow solid propellant, including the solid propellant grain, and the fluid propellant has been consumed in order to illustrate the autophagic aspect of the propulsion system.As illustrated in Figure 2(a), the inner face of the hollow solid propellant 4, namely the cavity, comprises a thread 9. According to a particular embodiment, the thread 9 is made on all or part of the surface of the cavity of the hollow solid propellant. In the illustrated embodiment, the thread 9 present on the cavity of the hollow solid propellant will have the role of a nut. According to the embodiment illustrated in Figure 2, the cap 2 comprises on its outer surface, a screw 8 of the propellant insertion system capable of being rotated in a thread 9 composing the inner face of the hollow solid propellant 4, namely the cavity, so as to apply a force to insert it into the combustion chamber. This screw and nut system makes it possible to transform the rotational movement of the screw into a translational movement of the hollow solid propellant thus moving the hollow solid propellant in the combustion chamber.Alternatively, the screw-nut system is reversed between the hollow solid propellant and the plug. The plug may comprise the screw. However, the screw may be separate from the plug. The rocket engine illustrated in Figure 2 may comprise a means 7 for connecting at least one wall of the combustion chamber 1 to the plug 2. The illustrated connection means is formed of knives 7. The knives may be of different sizes, in particular they may be of different lengths. According to an illustrated embodiment, the plug 2 is mechanically connected to the combustion chamber 1 by means of knives 7 which take up the internal pressure forces. The knives 7 pass through the solid propellant grain 4. When the rocket engine is in operation, the screw 8 rotates, driving in translation the thread 9 internal to the hollow solid propellant, in particular of the solid propellant grain 4, and thus moves in translation the hollow solid propellant towards the interior of the combustion chamber 1.According to a particular embodiment, the hollow solid propellant, in particular the solid propellant grain 4, cannot rotate relative to the combustion chamber because it is blocked in rotation by the knives 7; it is therefore forced to move axially in the combustion chamber 1. The fluid propellant 5 is contained in a volume which decreases because the plug 2 advances in the hollow solid propellant, in particular the solid propellant grain 4. Indeed, the volume of the cavity of the hollow solid propellant 4 containing the fluid propellant 5 decreases as combustion progresses because the hollow solid propellant 4 performs a translational movement relative to the plug 2. This decrease in volume forces the fluid propellant 5 through the valve 3 into the combustion chamber 1. The rotational speed of the screw 8 therefore imposes the mass flow rate to pass into the combustion chamber.As the hollow solid propellant, in particular the solid propellant grain, advances in the chamber as it burns, the internal surface of the hollow solid propellant, in particular the solid propellant grain 4, present in the combustion chamber, will have a conical shape in chamber 1, and the shape of this surface will be stationary during combustion for a fixed rotation speed of the screw 8. The regression speed being almost constant along the chamber, the hollow solid propellant present in the combustion chamber therefore takes on an approximately conical shape. Industrial application This type of propulsion is particularly suitable for space launchers. When combustion reaches its end, the rocket engine will have consumed a major part of the hollow solid propellant, in particular the solid propellant grain. The remaining mass of the space launcher using this propulsion device will therefore be very low at the end of combustion.Declarations Hybrid rocket engine in which a pressurized combustion chamber (1) closed by a plug (2) and a valve (3) contains a hollow solid propellant (4) whose internal face burns with a fluid propellant (5) injected through the plug (2), generating hot gases (6) escaping through a nozzle (6) so as to produce thrust on the vehicle characterized in that a part delimited by the plug (2) of the hollow solid propellant (4) serves as a container for the fluid propellant (5) before both being inserted into the combustion chamber (1).Hybrid rocket engine in which a pressurized combustion chamber (1) closed by a plug (2) and a valve (3) contains a hollow solid propellant (4) whose internal face burns with a fluid propellant (5) injected through the plug (2), generating hot gases (6) escaping through a nozzle (6) so as to produce thrust on the vehicle, characterized in that a portion of the hollow solid propellant (4) protrudes around the plug (2) outside the combustion chamber (1) and contains the fluid propellant (5) before both being inserted into the combustion chamber (1). Rocket engine according to the preceding statements, characterized in that a certain number of knives (7) connect the combustion chamber (1) to the plug (2), the exterior of which is a screw (8) rotated in a thread (9) composing the internal face of the hollow solid propellant (4) so ​​as to apply a force to insert it into the chamber.Rocket engine according to the preceding statement characterized in that the rotation of the screw (8) also drives a pump which allows additional pressurization of the fluid propellant (5) between the interior of the solid propellant (4) and the combustion chamber (1). Rocket engine according to the preceding statements characterized in that the screw (8) is rotated by an electric motor powered by an energy source such as batteries, fuel cells, or a gas generator. Rocket engine according to any one of the preceding statements characterized in that the screw (8) is rotated by a turbine driven by the gases produced by the combustion. Rocket engine according to any one of the preceding statements characterized in that a layer of thermal ablative is located on the exterior of the solid propellant (4) and releases cold gases to insulate the walls of the chamber (1) and the nozzle (6).Rocket engine according to any one of the preceding statements, characterized in that the solid propellant (4) is a composite material. Rocket engine according to any one of the preceding statements, characterized in that the solid propellant (4) is produced by additive manufacturing. Rocket engine according to any one of the preceding statements, characterized in that the hollow solid propellant comprises additives to improve its characteristics of density, mechanical strength, thermal conduction, regression speed during combustion, radial temperature distribution of the exhaust gases, chemical compatibility, average molar mass of the exhaust gases, friction characteristic, or any other physical characteristic of the solid propellant (4) and its combustion products with the fluid propellant (5).

Claims

Claims 1. A hybrid rocket engine comprising a combustion chamber supplied with a hollow solid propellant (4) and a fluid propellant (5), the hollow solid propellant having a cavity closed by a plug and a valve, and the fluid propellant being stored in the cavity of the hollow solid propellant.

2. A rocket engine according to the preceding claim, characterized in that the hollow solid propellant comprises - a first portion inserted into the combustion chamber to be burned there with fluid propellant (5) injected into the combustion chamber through the valve, and - a second portion which (4) extends out of the combustion chamber (1) and contains the fluid propellant (5) before both being inserted into the combustion chamber (1).

3. A rocket engine according to claim 1 or claim 2, characterized in that it further comprises a connecting means connecting at least one wall of the combustion chamber (1) and the plug (2). 4.Rocket engine according to the preceding claim, characterized in that the connection means comprises at least one knife (7) mechanically connecting said at least one wall of the combustion chamber to the plug and in that the first portion of the hollow solid propellant is crossed by said at least one knife during insertion of the hollow solid propellant into the combustion chamber.

5. Rocket engine according to claim 3 or claim 4, characterized in that the connection means comprises a plurality of knives mechanically connecting said at least one wall of the combustion chamber to the plug at different heights in the combustion chamber.

6. Rocket engine according to any one of the preceding claims, characterized in that it further comprises a system for inserting the propellants into the combustion chamber.

7. Rocket engine according to the preceding claim, characterized in that the plug comprises the system for inserting the propellants.

8. Rocket engine according to any one of claims 6 to 7, characterized in that the system for inserting the propellants comprises a means for generating a translational movement of the hollow solid propellant to insert it into the combustion chamber.

9. Rocket engine according to the preceding claim, characterized in that the means for generating a translational movement of the hollow solid propellant comprises a screw (8) capable of being rotated in a thread (9) forming a face of the hollow solid propellant (4) so ​​as to apply a force to insert it into the combustion chamber. 10.Rocket engine according to the preceding claim, characterized in that the thread (9) composing a face of the hollow solid propellant composes the internal face of the hollow solid propellant (4).

11. Rocket engine according to claim 9 or claim 10, characterized in that the cap comprises the screw.

12. Rocket engine according to any one of claims 9 to 11, characterized in that the rotation of the screw (8) further drives a pump capable of increasing the pressure of the fluid propellant when it is introduced into the combustion chamber (1).

13. Rocket engine according to any one of claims 9 to 12, characterized in that the screw (8) is rotated by an electric motor powered by an energy source such as batteries, fuel cells, or a gas generator.

14. Rocket engine according to any one of claims 9 to 12, characterized in that the screw (8) is rotated by a turbine driven by the gases produced by the combustion.

15. Rocket engine according to any one of the preceding claims, characterized in that the hollow solid propellant (4) comprises an outer layer of thermal ablative capable of releasing cold gases during combustion to insulate the wall or walls of the combustion chamber (1) and a nozzle (6).

16. Rocket engine according to any one of the preceding claims, characterized in that the solid propellant (4) is formed from a composite material.

17. Rocket engine according to any one of the preceding claims, characterized in that the solid propellant (4) comprises one or more additives.

18. Rocket engine according to any one of the preceding claims, characterized in that the solid propellant (4) is produced by additive manufacturing. 19.Hybrid rocket engine in which a pressurized combustion chamber (1) closed by a plug (2) and a valve (3) contains a hollow solid propellant (4) whose internal face burns with a fluid propellant (5) injected through the plug (2), generating hot gases (6) escaping through a nozzle (6) so as to produce thrust on the vehicle, characterized in that a part delimited by the plug (2) of the hollow solid propellant (4) serves as a container for the fluid propellant (5) before both being inserted into the combustion chamber (1).

20. Rocket engine according to the preceding claim, characterized in that a portion of the hollow solid propellant protrudes around the plug outside the combustion chamber.

21. Rocket engine according to any one of claims 19 to 20, characterized in that the hollow solid propellant comprises a cavity, the cavity containing the fluid propellant and being closed by the plug and the valve. 22.Rocket engine according to any one of claims 19 to 21, characterized in that the combustion chamber is further closed by the hollow solid propellant inserted into the combustion chamber.

23. Rocket engine according to any one of claims 19 to 22, characterized in that the hollow solid propellant comprises - a first portion inserted into the combustion chamber to be burned there with fluid propellant (5) injected into the combustion chamber through the valve and - a second portion which extends out of the combustion chamber (1) and contains the fluid propellant (5).

24. Rocket engine according to any one of claims 19 to 23, characterized in that it further comprises a connection means connecting at least one wall of the combustion chamber (1) and the plug (2).

25. Rocket engine according to the preceding claim, characterized in that the connection means comprises at least one knife mechanically connecting said at least one wall of the combustion chamber to the plug and in that the hollow solid propellant contained in the combustion chamber is crossed by said at least one knife during insertion of the hollow solid propellant into the combustion chamber.

26. Rocket engine according to claim 24 or 25, characterized in that the connecting means comprises a plurality of knives mechanically connecting said at least one wall of the combustion chamber to the plug at different heights in the combustion chamber.

27. Rocket engine according to any one of claims 19 to 26, characterized in that it further comprises a system for inserting the propellants into the combustion chamber.

28. Rocket engine according to the preceding claim, characterized in that the plug comprises the propellant insertion system.

29. Rocket engine according to any one of claims 27 to 28, characterized in that the propellant insertion system comprises means for generating a translational movement of the hollow solid propellant to insert it into the combustion chamber.

30. Rocket engine according to the preceding claim, characterized in that the means for generating a translational movement of the hollow solid propellant comprises a screw (8) capable of being rotated in a thread (9) forming a face of the hollow solid propellant (4) so ​​as to apply a force to insert it into the combustion chamber.

31. Rocket engine according to the preceding claim, characterized in that the thread (9) forming a face of the hollow solid propellant forms the internal face of the hollow solid propellant (4).

32. Rocket engine according to claim 30 or claim 31, characterized in that the cap comprises the screw.

33. Rocket engine according to claim 19, characterized in that a certain number of knives (7) connect the combustion chamber (1) to the plug (2) the exterior of which is a screw (8) rotated in a thread (9) forming the internal face of the hollow solid propellant (4) so ​​as to apply a force to insert it into the chamber. 34.Rocket engine according to any one of the preceding claims 30 to 33, characterized in that the rotation of the screw (8) also drives a pump which allows additional pressurization of the fluid propellant between the interior of the solid propellant (4) and the combustion chamber (1).

35. Rocket engine according to any one of the preceding claims 30 to 34, characterized in that the screw (8) is rotated by an electric motor powered by an energy source such as batteries, fuel cells, or a gas generator.

36. Rocket engine according to any one of the claims 30 to 34, characterized in that the screw (8) is rotated by a turbine driven by the gases produced by the combustion.

37. Rocket engine according to any one of claims 19 to 36, characterized in that a layer of thermal ablative is located on the outside of the solid propellant (4) and releases cold gases to insulate the walls of the combustion chamber (1) and the nozzle (6).

38. Rocket engine according to any one of claims 19 to 37, characterized in that the solid propellant (4) is a composite material.

39. Rocket engine according to any one of claims 19 to 38, characterized in that the solid propellant (4) comprises one or more additives.

40. Rocket engine according to any one of claims 19 to 39, characterized in that the solid propellant (4) is produced by additive manufacturing.

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