## 3 Results and Analysis
### Analysis of Pressure Load Characteristics of Liquid Cabin
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Test No.**} & \multirow{2}{*}{**Kinetic Energy**} & **Initial Peak** & **Specific Impulse** & **Peak Cavitation** & **Specific Impulse of** \\  & & **Pressure** & **of Initial Pressure** & **Load** & **Cavitation Load** \\  & & **(MPa)** & **(MPa-us)** & **(MPa)** & **(MPa-us)** \\ \hline
1 & 15,432 & 19.1 & 450 & 8.3 & 2516 \\
3 & 18,799 & 22.9 & 502 & 9.1 & 2617 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Peak value and specific impulse of initial pressure and cavitation load. Figure 16: Pressure loading stage. (**a**) 100 us; (**b**) 250 us; (**c**) 2300 us; (**d**) 3300 us; (**e**) 8000 us; (**f**) 11,300 us. of a high-pressure region, and then the bubble collapses, followed by bubble expansion again. At this time, shock waves are generated, and most of the energy in the bubble is converted into impact energy. Thereafter, the bubble keeps expanding and collapsing until all energy is dissipated. Due to the existence of the free surface in the water tank and the pressure sensor located at the bottom of the side wall of the water tank, the measured shock wave load for bubble collapse is relatively small (Figure 15). The cavity collapse pressure measured by Disimilea was very large, even exceeding the initial shock pressure. On the one hand, because the measuring points were arranged near the ballistic axis, and the cavity collapse also occurred on the ballistic axis, the measured pressure was large; on the other hand, the liquid-filled tank used was a closed tank with a large volume, resulting in a large cavity and higher pressure value generated during cavity collapse. To investigate the effect of attack angle on the loads during the projectile penetrating the liquid cabin, No. 29-33 are selected for investigation, and the loads on the side walls of the water tank and at the horizontal distance of 7.5 cm between the front/rear plates and the center are measured. According to Figure 17, as the attack angle of the projectile increases, the initial shock wave pressure load on the side walls of the tank tends to increase first and then decrease; meanwhile, due to improved attack angle, the area of the projectile in contact with water increases, resulting in greater water disturbance, so the load on the front plate keeps increasing; on the contrary, the pressure load on the rear plate decreases with the increasing attack angle for the following reasons: when the projectile enters the water at the velocity of 2400 m/s; meanwhile, the wave velocity in the water is only 1500 us, and the projectile separates from the shock wave after water entry for a period of time; at this time, the projectile yaws, and the measuring point on the rear plate is far away from the projectile axis; the increasing attack angle leads to greater projectile yaw and farther measuring point from the axis, and thus the pressure load on the rear plate decreases with the increasing attack angle. The initial shock wave propagates far away in a hemispherical shape, and the pressure along the wave arc decreases with the angle of the wave moving away from the ballistic axis. The measuring point on the front plate is more than 90\({}^{\circ}\) away from the axis, and the measuring point on the rear plate is near the axis, so at small attack angles, the pressure load on the rear plate is greater than that on the front plate; as the attack angle increases, the pressure load on the front plate increases but decreases on the rear plate, with the former exceeding the latter. The specific impulse change in the initial shock wave loads on the front and rear plates is consistent with the variation law of the shock wave pressure peak, but the specific impulse change of the cavitation load on the front plate is not significant.