# Prediction Method of Blast Wave Impact on Crew Module for Liquid Rocket Explosion on Launch Pad
## 6 Results and Analysis
### EnhancementEffects on Peak Overpressure of Model with aRocket  
The rocket model has a marked effect on the strength of the blast wave. For the whole rocket explosion scenario, the peak overpressure of model without a rocket is 2.09 MPa and that of model with a rocket is 35.84 MPa. The latter is 17 times of the former. Therefore, the influence of a rocket model on simulation results cannot be ignored.  
Models with a rocket and without a rocket are established for each explosion scenario. The peak overpressure acting on crew module is taken respectively, and the influence of rocket body on the blast wave propagation is studied by comparing the results. It is assumed that in the model with and without a rocket, the peak overpressure of the blast wave acting on the crew module is \(P_{\text{R}}\) and \(P_{\text{A}}\) respectively, and the pressure enhancement factor \(\alpha=P_{\text{R}}/P_{\text{A}}\) is defined. Under different scenarios, the peak overpressures and the pressure enhancement factors are shown in Table 12, and the pressure enhancement factor curve with scaled distance is shown in Figure 7.  
As can be seen from Figure 8, \(\alpha\) generally decreases with the scaled distance increases. When the scaled distance is less than 1.0 m/kg\({}^{-1/3}\), \(\alpha\) decreases significantly with the increase of the scaled distance, from the highest 17.15 to 3.91. However, when the scaled distance is greater than 1.0 m/kg\({}^{-1/3}\), \(\alpha\) does not change significantly with the scaled distance, and is stable at about 4.  
The rocket model can enhance the peak overpressure of blast wave. The factor is about 4 times in far scaled distance, while it is greater than 4 times in near scaled distance and up to 17 times. Therefore, the rocket model cannot be ignored when studying the effect of blast wave on the crew module.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Involved in Explosion** & **TNT Mass (kg)** & **Distance (m)** & **Scaled Distance** & **Peak Overpressure** \\  & & **(m-kg\({}^{-1/3}\))** & **(MPa)** \\ \hline whole rocket & \(5.12\times 10^{4}\) & 20 & \(5.39\times 10^{-1}\) & \(3.58\times 10^{1}\) \\ stage-1, 3 and boosters & \(4.62\times 10^{4}\) & 20 & \(5.57\times 10^{-1}\) & \(3.19\times 10^{1}\) \\ stage-3 & \(1.11\times 10^{4}\) & 15 & \(6.73\times 10^{-1}\) & \(2.07\times 10^{1}\) \\ stage-1, 2 and boosters & \(4.01\times 10^{4}\) & 36.5 & 1.07 & 4.97 \\ stage-2 & \(4.98\times 10^{3}\) & 20 & 1.17 & 3.99 \\ stage-2 and boosters & \(2.14\times 10^{4}\) & 37 & 1.33 & 3.14 \\ stage-1 & \(1.87\times 10^{4}\) & 36 & 1.35 & 2.86 \\ \hline \hline \end{tabular}
\end{table}
Table 11: Peak overpressures of blast wave for different stages involved in explosion.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Involved in Explosion** & \(P_{\text{R}}\) **(MPa)** & \(P_{\text{x}}\) **(MPa)** & \(\alpha\) \\ \hline whole rocket & 35.84 & 2.09 & 17.15 \\ stage-1, 3 and boosters & 31.90 & 1.98 & 16.11 \\ stage-3 & 20.73 & 1.65 & 12.56 \\ stage-1, 2 and boosters & 4.97 & 1.27 & 3.91 \\ stage-2 & 3.99 & 1.01 & 3.95 \\ stage-2 and boosters & 3.14 & 0.80 & 3.92 \\ stage-1 & 2.86 & 0.71 & 4.03 \\ \hline \hline \end{tabular}
\end{table}
Table 12: Comparison of peak overpressures of the model with and without a rocket.