## 3 Shock Experiment and Simulation Study of Spacecraft Structure
### Shock Experiment of the Spacecraft Structure  
The shock experiment should provide information for subsequent numerical simulation verification in three aspects. First, the shock force function acting on the structure is measured in the test. It is used as the input signal of numerical analysis. Second, the hybrid model is established, according to the structure of spacecraft. Third, the response results of the structure under shock load are obtained. It is used as a reference value for numerical analysis results.  
We designed a high frequency and high efficiency shock test platform based on the light-gas gun device. Shock tests of typical spacecraft structures are carried out with this platform. In the tests, a typical structure of the spacecraft is assembled by employing aluminum honeycomb sandwich panels and beams. The four aluminum honeycomb sandwich panels have the same structure; the size is 100 cm \(\times\) 120 cm, and the thickness is 3 cm. The plates are assembled into the spacecraft cabin by the beam structure.  
The shock experiment of the structure is shown in Figure 3. The structure is suspended on the test support by using elastic ropes. The power unit of shock loading device is the light-gas gun which is shown in Figure 4a. By changing the pressure value of the pressure chamber of the light-gas gun, the shock load is adjusted. Bullets with various geometries and vibrating rods of different materials and sizes are fabricated. By selecting the bullet and the vibrating rod, the waveform of the loading signal can be adjusted, and the shock load of our concerned frequency and magnitude can be obtained. A shock force sensor and a vibration rod are arranged at the shock position of the structure, which is shown in Figure 4b. In the experiment, the function of the shock force sensor is to measure the electric signal of the shock force function of the bullet acting on the steel plate. The measuring range of the force sensor is 80,000 N. The measured signal can be directly converted into the pressure signal by using the piezoresistive relationship obtained by calibrating the sensor in advance. It provides input force for numerical calculation.  
Subsequently, the inclusion curves of \(SRS\) results of all acceleration sensor data on a board are used as the test results of the board. The acceleration sensors are arranged on four plates in the principle of random distribution. Four acceleration sensors are arranged on each board. The measuring range of the acceleration sensor is 20,000 Hz and 50,000 g. Through the signal acquisition system, the acceleration response of each position of the structure is collected. The measurement and control system of the experiment can be seen in Figure 5. Based on the measurement and control system, the results are collected, analyzed and processed. Finally, the acceleration shock response spectrum of the structure can be calculated, according to the shock response results. According to the acceleration signal of each measuring point, the average acceleration response and \(SRS\) of the structure in space is calculated. The test experiment is used to provide reference values for numerical analysis.