A method for reusing the mechanical environment test of a spacecraft

Abstract

The present invention discloses a method for the mechanical environment test of a reusable spacecraft, which includes conducting virtual mechanical tests, building a mechanical environment test system, conducting high-level mechanical environment tests on the reusable spacecraft, determining the structural damage conditions, and predicting the remaining life of the spacecraft. The present invention predicts the dynamic response of the spacecraft structure through virtual mechanical tests, estimates the working life of the structure, and proposes high-level mechanical environment test conditions to simulate the reuse conditions. It can conduct physical tests on the spacecraft and extract the natural frequency values, and use the proportion of the decrease in the structural natural frequency as the judgment basis to determine the damage conditions of the spacecraft under the action of the mechanical environment in the working state, determine whether it can meet the requirements of reuse, and predict the remaining life. This method combines virtual tests with physical tests to effectively determine the life of the structure of the reusable spacecraft. The high-level physical tests also improve the test efficiency and provide an important basis for the reliability analysis of the spacecraft.

Description

Technical Field

[0001] The present invention relates to the technical field of reusable spacecraft research, and particularly to a method for mechanical environment testing of reusable spacecraft. Background Art

[0002] Reusable spacecraft have a wide range of application spaces in the military field. Moreover, with the continuous breakthrough of key technologies, reusable spacecraft will also have more advantages in terms of usage cost compared with traditional spacecraft. The procurement costs, usage, and support costs of modern space equipment are becoming increasingly huge, and economic affordability has become one of the unavoidable issues in the equipment development of various countries. Therefore, relevant research on the key technologies in the development process of reusable spacecraft has important engineering significance.

[0003] The purpose of the mechanical environment testing of spacecraft is to simulate various mechanical environments and their effects that spacecraft experience during launch and re-entry in ground mechanical testing equipment, so as to test whether the spacecraft and its various parts can withstand these environments and work properly. In order to give full play to the role of mechanical environment testing in ensuring the reliability of spacecraft, that is, to be able to discover problems and eliminate hidden dangers, and not be overly conservative, affecting the development cost and cycle. It not only requires correct test theory, formulation of relatively reasonable test conditions, but also requires test equipment that can relatively truly simulate various environments and correct test methods. The above points are interrelated and indispensable. The mechanical environments that spacecraft experience during launch are diverse, such as noise, vibration, shock, overload, and spin, etc. The dynamic environment of spacecraft is relatively complex. The dynamic environments that may be experienced during the entire life cycle include: the dynamic environment that spacecraft experience during transportation before launch; the dynamic environment that spacecraft experience during launch and return, specifically including the transient environment induced by rocket takeoff and the noise environment generated by engines, the pressure oscillation environment of solid rocket motors, the aerodynamic noise environment during liftoff, the transient environment generated when engines start and shut down, the POGO vibration environment, the liquid sloshing environment inside the tank, the transient environment generated during stage separation and fairing separation, the shock environment generated by the explosion of pyrotechnics, etc. Specific methods for mechanical environment testing of spacecraft include acoustic testing, random vibration testing, sine sweep vibration testing, shock testing, etc.

[0004] Regarding the mechanical environment testing of spacecraft, foreign countries already have clear test theories and specifications. The United States has published "General Environmental Test Specifications for Spacecraft and Their Components" and "Test Requirements for Space Vehicles". Europe and Japan also have similar tests and requirements. China has also established a relatively large-scale spacecraft environmental test equipment and has accumulated certain experience in test theory and test technology.

[0005] Compared with traditional single - use spacecraft, the development of reusable spacecraft is more difficult and requires consideration of more issues. For example, the impact of mechanical and thermal loads on the structure during multiple launch and return missions of the spacecraft, how to verify the reliability of the spacecraft structure through mechanical environment tests before launch, and so on. Vibration tests are a very important part of the mechanical environment tests of the spacecraft. How to propose corresponding test verification mechanisms for reusable spacecraft based on the integration of existing vibration test verification mechanisms is the main research topic of this patent. Summary of the Invention

[0006] The purpose of the present invention is to propose a mechanical environment test method for reusable spacecraft in order to solve the above - mentioned problems.

[0007] In order to achieve the above - mentioned purpose, the present invention adopts the following technical solutions:

[0008] A mechanical environment test method for reusable spacecraft includes the following steps:

[0009] S1. Conduct virtual mechanical tests. Virtual mechanical tests use the digital model of the spacecraft structure to simulate physical tests, predict the mechanical tests of the spacecraft through digital means, obtain the modal and dynamic response parameters of the structure, and thereby achieve the purpose of guiding the design of mechanical tests, evaluating the rationality of test conditions and measuring point settings, and optimizing the design of the spacecraft structure.

[0010] S2. Build a mechanical environment test system. The mechanical environment test system includes a spacecraft, a fixture, an electrodynamic shaker, a power amplifier, a controller, an acceleration sensor, a measuring instrument, and a control computer. The spacecraft is installed on the test table of the electrodynamic shaker through the fixture. The electrodynamic shaker is driven by the power amplifier to amplify the signal output by the controller. The controller generates corresponding signals according to the test conditions input by the computer and adjusts the output signals in real - time according to the feedback signals of the acceleration sensors at the control points. The acceleration sensors installed on the spacecraft obtain the response of the structure and transmit it to the control computer through the measuring instrument to save the results.

[0011] S3. Conduct low - level sine sweep tests, extract the results of the measuring acceleration sensors, and record the natural frequency f of the structure.

[0012] S4. Conduct high - level mechanical environment tests.

[0013] S5. Conduct low - level sine sweep tests, extract the results of the measuring acceleration sensors, and record the natural frequency f' of the structure.

[0014] S6. After the test results are determined to be valid, withdraw the spacecraft and restore the state of the mechanical environment test system.

[0015] S7. Determine the structural damage condition. When the spacecraft is subjected to mechanical environmental loads, the structural stiffness will decrease, which will in turn cause changes in its structural dynamic characteristics and a decrease in the structural natural frequency. Therefore, the proportion of the decrease in the structural natural frequency is selected as the damage determination criterion for the reusable spacecraft.

[0016] S8. According to the reliability requirements of the reusable spacecraft, select the coefficient α, and compare f' with α·f. When the natural frequency of the spacecraft decreases significantly after the high-level mechanical environmental test, that is, f' < α·f, the structure does not meet the requirement of being reusable N times, and the structural form should be redesigned and optimized.

[0017] S9. According to the reliability requirements of the reusable spacecraft, select the coefficient α, and compare f' with α·f. When the natural frequency of the spacecraft structure does not decrease significantly after the high-level mechanical environmental test, that is, f' > α·f, the structure can meet the requirement of being reusable N times.

[0018] S10. On the premise that the spacecraft can meet the service life requirement of being reusable N times, substitute the remaining change amount of the natural frequency of the reusable spacecraft Δf = f' - αf into the refined digital model of the spacecraft structure. By analyzing the damage value of the spacecraft, estimate the theoretical remaining flight times of the structure, providing a reference for the reliability analysis of the spacecraft.

[0019] Preferably, the virtual mechanical test in step S1 includes the following steps:

[0020] S1.1. Establish a refined digital model of the spacecraft structure.

[0021] S1.2. Conduct a virtual mechanical environment test, simulate the mechanical environment of a single flight of the spacecraft, extract the structural responses and stress-strain mechanical analysis results at key positions, and calculate the damage value of the spacecraft structure.

[0022] S1.3. Calculate the damage value corresponding to the spacecraft structure after being reused N times, propose the corresponding high-level mechanical environmental test conditions and test duration, and predict the working life of the spacecraft structure.

[0023] Preferably, the construction of the mechanical environment test system in step S2 includes the following steps:

[0024] S2.1. Build a mechanical environment test system capable of real-time closed-loop control.

[0025] S2.2. Design and manufacture a mechanical test fixture for the spacecraft.

[0026] S2.3. Install the spacecraft on the mechanical environment test system.

[0027] Preferably, in step S4, when conducting the high-level mechanical environment test, the reusable spacecraft is installed on a fixture and fixed to the tabletop of an electric vibration table. An acceleration sensor is installed, and the high-level mechanical environment test conditions in step S1.3 are input into a control computer. Then, the mechanical test of the reusable spacecraft is carried out on the established mechanical environment test system. During the test process, the responses of the structural key points measured by the acceleration sensor are recorded.

[0028] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0029] 1. This application can be used as a method for verifying the mechanical reliability of the structure of a spacecraft before launch. First, through virtual mechanical tests, the dynamic responses of the spacecraft structure are predicted, the working life of the structure is estimated, and high-level mechanical environment test conditions are proposed to simulate the reusable conditions. The mechanical environment test system can conduct physical tests on the spacecraft and extract the natural frequency values. Taking the decrease ratio of the structural natural frequency as the judgment basis, the damage situation of the spacecraft under the action of the mechanical environment in the working state is judged, whether it can meet the requirements of reuse is determined, and its remaining fatigue life can be estimated accordingly. This method combines virtual tests with physical tests, effectively determines the life of the reusable spacecraft structure, and the high-level physical tests also improve the test efficiency, providing an important basis for spacecraft reliability analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. shows a schematic diagram of a mechanical environment test system for a method of mechanical environment test of a reusable spacecraft according to an embodiment of the present invention;

[0031] Figure 2 FIG. shows a flow block diagram of a mechanical environment test according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Please refer to Figure 1-2 , the present invention provides a technical solution:

[0034] A method for mechanical environment test of a reusable spacecraft includes the following steps:

[0035] S1. Conduct virtual mechanical tests. Virtual mechanical tests use the digital model of the spacecraft structure to simulate physical tests, predict the spacecraft mechanical tests through digital means, obtain the modal and dynamic response parameters of the structure, and thereby achieve the purpose of guiding the mechanical test design, evaluating the rationality of test conditions and measuring point settings, and optimizing the spacecraft structure design;

[0036] S2. Build a mechanical environment test system. The mechanical environment test system includes a spacecraft, a fixture, an electro-dynamic vibration shaker, a power amplifier, a controller, an acceleration sensor, a measuring instrument, and a control computer. The spacecraft is installed on the test table of the electro-dynamic vibration shaker through the fixture. The electro-dynamic vibration shaker is driven by amplifying the signal output by the controller by the power amplifier. The controller generates corresponding signals according to the test conditions input by the computer and adjusts the output signals in real time according to the feedback signals of the acceleration sensors at the control points. The acceleration sensors installed on the spacecraft obtain the response of the structure and transmit it to the control computer through the measuring instrument to save the results;

[0037] S3. Conduct a low-level sine sweep test, extract the results of the measuring acceleration sensors, and record the natural frequency f of the structure;

[0038] S4. Conduct a high-level mechanical environment test;

[0039] S5. Conduct a low-level sine sweep test, extract the results of the measuring acceleration sensors, and record the natural frequency f' of the structure;

[0040] S6. After the test results are determined to be valid, withdraw the spacecraft and restore the state of the mechanical environment test system;

[0041] S7. Determine the structural damage condition. When the spacecraft is subjected to mechanical environment loads, it will cause a reduction in structural stiffness, which will in turn cause changes in its structural dynamic characteristics and a decrease in the structural natural frequency. Therefore, the proportion of the decrease in the structural natural frequency is selected as the damage determination criterion for the reusable spacecraft;

[0042] S8. According to the reliability requirements of the reusable spacecraft, select the coefficient α, compare f' with α·f. When the natural frequency of the spacecraft is significantly reduced after the high-level mechanical environment test, that is, f' < α·f, then the structure cannot meet the requirement of being reused N times and the structural form should be redesigned and optimized;

[0043] S9. According to the reliability requirements of the reusable spacecraft, select the coefficient α, compare f' with α·f. When the natural frequency of the spacecraft structure is not significantly reduced after the high-level mechanical environment test, that is, f' > α·f, then the structure can meet the requirement of being reused N times;

[0044] S10. On the premise that the spacecraft can meet the requirement of N - time reuse life, substitute the remaining change in natural frequency of the reusable spacecraft, Δf = f' - αf, into the refined digital model of the spacecraft structure. By analyzing the damage value of the spacecraft, estimate the theoretical remaining flight times of the structure, providing a reference for the reliability analysis of the spacecraft.

[0045] Specifically, as Figure 1 and Figure 2 shown, the virtual mechanical test in step S1 includes the following steps:

[0046] S1.1. Establish a refined digital model of the spacecraft structure;

[0047] S1.2. Conduct a virtual mechanical environment test, simulate the mechanical environment during one flight of the spacecraft, extract the structural responses and stress - strain mechanical analysis results at key positions, and calculate the damage value of the spacecraft structure based on theories such as fatigue mechanics.

[0048] S1.3. According to the damage theory and the expected number of reuse times of the spacecraft, calculate the corresponding damage value of the spacecraft structure after N - time reuse. Based on the damage equivalence principle, propose the corresponding high - level mechanical environment test conditions and test duration, and predict the working life of the spacecraft structure.

[0049] The steps for building the mechanical environment test system in step S2 include the following:

[0050] S2.1. Build a mechanical environment test system with real - time closed - loop control;

[0051] S2.2. Design and machine the mechanical test fixture for the spacecraft;

[0052] S2.3. Install the spacecraft on the mechanical environment test system.

[0053] The purpose of building the mechanical environment test system is to accurately test the mechanical environment of the spacecraft. This system can simulate the mechanical environment of the spacecraft's working state, test the performance and defects of the structure, and can perform real - time closed - loop control on the vibration form through the control signal fed back by the acceleration sensor.

[0054] In step S4, when conducting the high - level mechanical environment test, install the reusable spacecraft on the fixture and fix it to the tabletop of the electrodynamic vibration table. Install the acceleration sensor, input the high - level mechanical environment test conditions in step S1.3 into the control computer, and conduct the mechanical test of the reusable spacecraft on the built mechanical environment test system. During the test, record the responses of the key points of the structure measured by the acceleration sensor.

[0055] Before and after the high-level mechanical environment test, a low-level sine sweep test is carried out respectively. The results of the measured acceleration sensors are extracted, and the natural frequencies of the structure are recorded, that is, the vibration excitation frequency values corresponding to the extreme values of the measured acceleration sensor response of the structure during the sine sweep test, which are denoted as f and f' respectively.

[0056] The method of the present application can be used to verify the mechanical reliability of the structure of a spacecraft before launch. First, the dynamic response of the spacecraft structure is predicted through virtual mechanical tests, the working life of the structure is estimated, and high-level mechanical environment test conditions are proposed to simulate the reuse conditions. The mechanical environment test system can conduct physical tests on the spacecraft and extract the natural frequency values. Taking the proportion of the decrease in the natural frequency of the structure as the judgment basis, the damage situation of the spacecraft under the action of the mechanical environment in the working state is judged, whether it can meet the reuse requirements is determined, and its remaining fatigue life can be estimated accordingly. This method combines virtual tests with physical tests, effectively determines the life of the reusable spacecraft structure, and the high-level physical tests also improve the test efficiency, providing an important basis for the reliability analysis of the spacecraft.

[0057] The above description of the embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for reusing the mechanical environment test of a spacecraft, characterized in that, it includes the following steps: S1. Conduct a virtual mechanical test. The virtual mechanical test uses a digital model of the spacecraft structure to simulate the physical test, predicts the spacecraft mechanical test through digital means, obtains the modal and dynamic response parameters of the structure, and thereby achieves the purpose of guiding the mechanical test design, evaluating the rationality of test conditions and measuring point settings, and optimizing the spacecraft structure design; S2. Build a mechanical environment test system. The mechanical environment test system includes a spacecraft, a fixture, an electrodynamic shaker, a power amplifier, a controller, an acceleration sensor, a measuring instrument, and a control computer. The spacecraft is installed on the test table of the electrodynamic shaker through the fixture. The electrodynamic shaker is driven by the power amplifier to amplify the signal output by the controller. The controller generates a corresponding signal according to the test conditions input by the computer and adjusts the output signal in real time according to the feedback signal of the acceleration sensor at the control point. The acceleration sensor installed on the spacecraft obtains the response of the structure and transmits it to the control computer through the measuring instrument to save the results; S3. Conduct a low-level sine sweep test, extract the results of the measuring acceleration sensor, and record the natural frequency f of the structure; S4. Conduct a high-level mechanical environment test; S5. Conduct a low-level sine sweep test, extract the results of the measuring acceleration sensor, and record the natural frequency f' of the structure; S6. After the test results are determined to be valid, withdraw the spacecraft and restore the state of the mechanical environment test system; S7. Determine the structural damage condition. When the spacecraft is subjected to mechanical environment loads, it will cause a decrease in structural stiffness, which will in turn cause changes in its structural dynamic characteristics and a decrease in the structural natural frequency. Therefore, the ratio of the decrease in the structural natural frequency is selected as the damage determination criterion for the reusable spacecraft; S8. According to the reliability requirements of the reusable spacecraft, select a coefficient α, compare f' with α·f. When the natural frequency of the spacecraft decreases significantly after the high-level mechanical environment test, that is, f' < α·f, then this structure does not meet the requirement of being reusable N times and the structural form should be redesigned and optimized; S9. According to the reliability requirements of the reusable spacecraft, select a coefficient α, compare f' with α·f. When the natural frequency of the spacecraft structure does not decrease significantly after the high-level mechanical environment test, that is, f' > α·f, then this structure can meet the requirement of being reusable N times; S10. On the premise that the reusable spacecraft can meet the service life requirement of being reusable N times, substitute the remaining change amount of the natural frequency of the reusable spacecraft Δf = f' - αf into the refined digital model of the spacecraft structure. By analyzing the damage value of the spacecraft, estimate the theoretical remaining flight times of the structure to provide a reference for the reliability analysis of the spacecraft.

2. The method for reusing the mechanical environment test of a spacecraft according to claim 1, characterized in that, the virtual mechanical test in step S1 includes the following steps: S1.

1. Establish a refined digital model of the spacecraft structure; S1.

2. Conduct virtual mechanical environment tests to simulate the mechanical environment during the first flight of the spacecraft, extract the structural responses and stress-strain mechanical analysis results at key positions, and calculate the damage values of the spacecraft structure. S1.

3. Calculate the damage values corresponding to the spacecraft structure after being reused N times, propose the corresponding high-level mechanical environment test conditions and test duration, and predict the working life of the spacecraft structure.

3. A method for mechanical environment tests of a reusable spacecraft according to claim 1, characterized in that the establishment of the mechanical environment test system in step S2 includes the following steps: S2.

1. Establish a mechanical environment test system capable of real-time closed-loop control; S2.

2. Design and manufacture a mechanical test fixture for the spacecraft; S2.

3. Install the spacecraft on the mechanical environment test system.

4. A method for mechanical environment tests of a reusable spacecraft according to claim 2, characterized in that in step S4, when conducting high-level mechanical environment tests, the reusable spacecraft is installed on a fixture and fixed to the tabletop of an electric vibration table, an acceleration sensor is installed, the high-level mechanical environment test conditions in step S1.3 are input into the control computer, and mechanical tests of the reusable spacecraft are carried out on the established mechanical environment test system. During the test process, record the responses of the structural key points measured by the acceleration sensor.

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