Solid propellant thruster with integrated control device and thruster aging control system

Abstract

The invention relates to a solid propellant thruster comprising a housing (12) containing a propellant fill (14) in which an axial channel (16) is formed for the combustion of the propellant fill (14), on which housing (12) a propellant sample (24) located in the channel (16) and a sensor (28) located outside of the housing (12) and facing the sample (24) are arranged, to allow a vibrational excitation to be emitted and a response to be transmitted through the sample (24).

Description

Technical Field

[0001] The invention relates to a solid propellant thruster with an integrated control device and a thruster aging control system. Background Art

[0002] Many rocket-based ballistic weapons use the combustion of solid propellants to generate thrust to ensure their movement.

[0003] Ballistic weapons may be stored for long periods of time after manufacture, sometimes up to years. It is important to know the state of the propellant before use, to verify that it can perform its function and to assess the inherent safety level of its use.

[0004] It is possible to define an apparent age of a propellant, corresponding to the actual observed level of aging. This allows an assessment of the remaining useful life of a ballistic weapon using this propellant.

[0005] Solid propellants contain both fuel and oxidizer, and knowledge of certain mechanical properties of the propellant, such as Young's modulus or shear modulus, can provide an estimate of its apparent age. These mechanical properties can be derived from the material's response to vibration wave excitation.

[0006] It is known, in particular from document FR 2 954 498 A1, that a test device can be used which contains a propellant sample and a vibration system in a housing. The test device can be placed near the ballistic weapon or even inside it. In order to try to obtain comparable aging of the ballistic weapon and the test device.

[0007] However, the test device described in document FR 2 954 498 A1 is not suitable for industrial applications. The applicant has found several disadvantages:

[0008] - The device is bulky and heavy inside the thruster.

[0009] - Since the propellant sample in the test rig is confined within the test rig enclosure, its environmental conditions are different from those of the propellant in the thruster. In particular, the oxidation rate of the sample is different from that of the propellant in the thruster.

[0010] - Installing the test device inside the thruster introduces a power source inside the thruster. This poses a risk of igniting the thruster during the prototype testing phase.

[0011] -The presence of components other than propellant inside the thruster may interfere with its function. Summary of the invention

[0012] The present invention aims to solve some or all of the above problems by proposing a solid propellant thruster equipped with a test specimen that allows the emission of vibration excitations from outside the thruster through the specimen and the transmission of responses.

[0013] To this end, the object of the present invention is a solid propellant thruster comprising a casing containing a propellant charge, an axial passage formed in the propellant charge for combustion of the propellant charge, the casing being provided with a propellant sample located in the passage and a sensor located outside the casing and facing the sample to allow emission of a vibration excitation through the sample and transmission of a response.

[0014] Advantageously, the channel extends between the two axial ends of the pusher, and the housing has a sample through hole at one end thereof which communicates with the channel.

[0015] Advantageously, the pusher further comprises a disk fixed at the through hole of the housing, the disk having an inner surface facing the channel, on which the sample is fixed, and an outer surface facing in the opposite direction of the channel, on which the sensor is fixed.

[0016] Advantageously, the housing has a circular recess for accommodating the disc, and the sample passage hole is arranged at the bottom of the circular recess.

[0017] Advantageously, the sample is fixed to the inner surface of the disc by means of an adhesive.

[0018] The propellant charge may comprise a polymer binder, the adhesive advantageously being based on the same polymer binder.

[0019] Advantageously, the propellant of the sample is the same as the propellant of the fill.

[0020] Advantageously, the sensor comprises electrical connections for receiving a first signal to cause the sensor to emit a vibration excitation, and for acquiring a second signal representative of a response of the sample to the vibration excitation.

[0021] The invention also relates to a thruster aging control system according to the invention, comprising an electronic module configured to:

[0022] - Temporary connection to the sensor,

[0023] - sending a first signal to the sensor to cause it to form a vibration excitation,

[0024] - receiving a second response signal from the sensor,

[0025] - Derivation of a parameter representative of the thruster filling ageing state from the received signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention may be better understood and its advantages more apparent by reading the detailed description of one embodiment given, which is illustrated by the accompanying drawings, in which:

[0027] Figure 1 A solid propellant thruster according to the invention is schematically represented;

[0028] Figure 2 More detailed representation of the test Figure 1 The component of the propellant in the thruster. DETAILED DESCRIPTION

[0029] For clarity, the same elements will be labeled the same in different figures.

[0030] Figure 1 and Figure 2 A thruster 10 is schematically shown, for example for use in ballistic weapons. The thruster 10 comprises a solid propellant charge 14 in a housing 12. The solid propellant contains both a fuel and an oxidizer. The propellant is for example a composite propellant based on a polyurethane binder, as described in French patent FR 3 108 331 B3 filed by the applicant. The invention is not limited to this type of propellant, any type of propellant may be used within the scope of the invention.

[0031] The combustion of the propellant ensures the thrust of the thruster, and the housing 12 must be able to withstand the pressure and temperature generated by the combustion. In order to withstand the combustion temperature, a thermal protection layer can be integrated between the housing 12 and the propellant filling. In order to withstand the pressure, different materials can be used, such as metallic materials such as steel or carbon fiber-based materials. Other materials can be used. In addition to pressure and temperature, other constraints may arise when implementing the present invention.

[0032] A longitudinal passage 16 extending along an axis 18 is formed in the propellant charge 14. The passage 16 extends between two axial ends 20 and 22 of the thruster 10. Here, one end 20 of the passage 16 is blocked by a disk 26, and the other end 22 of the passage 16 forms a nozzle through which the propellant combustion products are ejected to provide thrust.

[0033] According to the present invention, the thruster 10 includes a propellant sample 24 located in the passage 16, where it is fixed to the inner surface 27 of the disk 26. The propellant sample 24 is preferably made of the same propellant as the propellant charge 14. Alternatively, it is also possible to use a propellant for the sample 24 that is different from the charge 14 but has similar physical properties (especially with respect to aging).

[0034] The thruster 10 also includes a sensor 28 fixed to the outer surface 30 of the disk 26, located opposite the sample 24, to allow the emission of vibration excitation through the sample 24 and the transmission of the response. The channel 16 can be formed directly in the propellant fill 14. In this case, the sample 24 is preferably exposed. More specifically, the propellant of the sample 24 as well as the propellant of the fill 14 are directly exposed to the air in the channel 16. Therefore, the propellant of the fill 14 and the propellant of the sample 24 react to the environment of the channel 16 in the same way. More specifically, during the storage of the thruster 10, changes in temperature and humidity may occur. These two parameters are critical to the aging of the propellant. Other parameters may also play a role, such as pressure, but may not be as important. However, exposing the propellant of the fill 14 and the propellant of the sample 24 to the same environment allows all types of environmental parameters to be taken into account. This same exposure also allows for the accommodation of different propellant compositions that may age differently depending on the environment; by keeping the same material for the propellant of the fill 14 and the propellant of the sample 24, they will age in a similar way because they are exposed to the same environmental conditions.

[0035] Figure 2 The sensor 28, the disc 26 and the sample 24 are shown in more detail. The sensor 28 is located on the outer surface 30 of the disc 26, the sample 24 is fixed on its inner surface 27, here parallel to the outer surface 30, and is configured to emit a vibration excitation in the sample 24. The vibration excitation is obtained, for example, by ultrasonic-type sound waves emitted by the sensor 28, which pass through the disc 26 and the sample 24. The disc 26 made of steel has good transmission characteristics for ultrasonic-type vibration excitations. More generally, the material forming the insert of the disc 26 is chosen to be able to transmit mechanical excitations while being less subject to aging risks like propellants.

[0036] exist Figure 1 and Figure 2 In the example shown, the sample 24 has two parallel faces, one face 32 in contact with the inner surface 27 of the disk 26, and the other face 34 freely exposed to the air in the channel 16. The vibration excitation emitted by the sensor 28 first passes through the sample 24 from the face 32 to the face 34, is at least partially reflected at the face 34, and then passes through the disk 26 again to be received by the sensor 28. The path of the vibration excitation from the face 32 to the face 34, called the outward path, is indicated by arrow 36, and the path from the face 34 to the face 32, called the return path, is indicated by arrow 38. In order to implement the present invention, the sample 24 can have other shapes. The faces 32 and 34 may not be parallel. The faces 32 and 34 are not necessarily planar. For example, the inner surface 27 of the disk 26 on which the sample 24 is placed may not be planar, in which case the face 32 of the sample 24 preferably conforms to the shape of the inner surface 27 to promote the vibration excitation to be directly transmitted from the disk 26 to the sample 24 without passing through any air layer that may exist between the inner surface 27 of the disk 12 and the face 32 of the sample 24.

[0037] The thickness of the disk 12 is such that it can withstand the temperature / pressure combinations in the combustion chamber, but if necessary, a heat shield can be inserted between the two faces 27 and 32 to thermally protect the disk 26 without fundamentally interfering with the acoustic principle of the system.

[0038] Advantageously, the sample 24 is bonded to the inner face 27 of the disk 26, while the sensor 28 is bonded to the outer face 30 of the disk 26. Thus, the fixation of the sample 24 and the sensor 28 is free of mechanical components that could interfere with the vibration excitation. The bonding also limits the formation of an air layer between the inner face 27 of the disk 26 and the face 32 of the sample 24, by completely spreading between the faces 27 and 32. The same is true for the sensor 28 side. The propellant may contain a polymer adhesive, such as described in patent FR 3 108 331 B3. Thus, it is advantageous to fix the sample 24 to the inner face 27 of the disk 26, and even to fix the sensor 28 on its opposite face 30, using an adhesive 39 that is the same adhesive as that used in the propellant. This type of adhesive makes it possible in particular to reduce the interference with the propagation of the vibration excitation at the interface between the adhesive and the propellant.

[0039] As an alternative, it is conceivable to glue the test coupon 24 directly to the inner surface of the housing 12 , which blocks the end 20 of the passage 16 .

[0040] The disk 26 can be fixed to the housing in different ways. Here, it is mounted in a circular recess 29 of the housing 12 and fixed by screws (not shown in the figure for simplicity). The bottom 31 of the recess 29 has a hole 33 for receiving the sample 24. As an alternative, the disk 26 can also be mechanically fixed to the outer surface of the housing 12.

[0041] Furthermore, a sealing ring 35 is inserted between the disk 26 and the housing 12 , which is seated in a groove 37 provided in the disk 26 .

[0042] exist Figure 1 and Figure 2 In the figure, the sensor 28 is represented as a single component configured to transmit vibration excitation and receive a response to the transmitted vibration excitation. In practice, two functions can be distinguished: transmitting and receiving vibration excitation, one component for transmitting the excitation and the other for receiving the vibration excitation that passes through the sample 24 and is reflected by the surface 34. The sensor 28 can use piezoelectric ceramics to generate the vibration excitation. This type of ceramic can also receive the reflected wave, form a response to the vibration excitation, and output a corresponding electrical signal.

[0043] In the embodiment shown, the sensor 28 includes an electrical connection 40 for temporarily connecting the sensor 28. The electrical connection 40 and the sensor 28 are located outside the housing 12, which prevents any electrical signals from entering the housing to operate the sensor 28. Therefore, only the vibration excitation enters the housing 12. The electrical connection 40 allows the connection of an electronic module 42, here represented as a personal computer. The electronic module 42 can be connected to the sensor 28 via a cable 44. Alternatively, the electronic module 42 can be connected to the sensor 28 via a wireless connection.

[0044] The electronic module 42 is configured to generate and send a signal to the sensor 28 to cause it to form a vibration excitation. The electronic module 42 is also configured to receive a response signal from the sensor 28, which corresponds to the vibration response of the sample 24.

[0045] The electronic module 42 is configured to analyze the response signal from the sensor 28 and to derive therefrom parameters representative of the aging state of the propellant of the sample 24 and, therefore, of the propellant of the fill 14. This derivation is done, for example, by comparing the received signal with stored signals representative of different aging states. It is also possible to determine from the vibration response certain mechanical parameters of the propellant, such as its Young's modulus or its shear modulus. The evolution of these mechanical parameters provides information about the aging state of the propellant.

[0046] In this regard, it should be noted that the arrangement of the invention allows determining the remaining useful life of the thruster without requiring specific knowledge of the conditions in which the thruster is stored in order to determine the ageing state of the propellant.

Claims

1. A solid propellant thruster comprising a housing (12) containing a propellant charge (14), wherein an axial passage (16) is formed in the propellant charge (14) for combustion of the propellant charge (14), wherein the housing (12) is provided with a propellant sample (24) located in the passage (16) and a sensor (28) located outside the housing (12) and facing the propellant sample (24) so ​​as to emit a vibration excitation through the propellant sample (24) and transmit a response.

2. A thruster according to claim 1, wherein the passage (16) extends between the two axial ends (20, 22) of the thruster (10), and the housing (12) has a propellant sample passage hole (33) at one end (20) thereof that communicates with the passage (16).

3. The thruster according to claim 2 further comprises a disk (26) fixed at the through hole (33) of the housing (12), the disk having an inner surface (27) facing the channel (16), the propellant sample (24) being fixed on the inner surface, and an outer surface (30) facing the opposite direction of the channel (16), the sensor (28) being fixed on the outer surface.

4. A thruster according to claim 3, wherein the housing (12) has a circular recess (29) for receiving the disc (26), the propellant sample being provided at the bottom (31) of the circular recess (29) through the hole (33).

5. A thruster according to claim 3 or 4, wherein the propellant sample (24) is fixed to the inner surface (27) of the disc (26) by means of an adhesive (39).

6. The propeller according to claim 5, wherein the propellant charge (14) comprises a polymer binder, the adhesive (39) being based on the same polymer binder.

7. The thruster according to any of the preceding claims, wherein the propellant of the propellant sample (24) is the same as the propellant of the fill (14).

8. A thruster according to any one of the preceding claims, wherein the sensor (28) includes an electrical connection (42) for receiving a first signal to cause the sensor (28) to emit a vibration excitation, and for acquiring a second signal representative of a response of the propellant sample (24) to the vibration excitation.

9. An aging control system for a thruster (10) according to any one of the preceding claims, comprising an electronic module (42) configured to: - temporarily connected to said sensor (28), - sending a first signal to the sensor (28) to cause it to form a vibration excitation, - receiving a second response signal from said sensor (28), - deriving from the received signal a parameter representative of the ageing state of the filling (14) of the thruster (10).

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