# Prediction Method of Blast Wave Impact on Crew Module for Liquid Rocket Explosion on Launch Pad
###### Abstract
An empirical non-TNT approach was established to predict launch vehicles explosion environment characteristics in the near field by [PERSON]. All available empirical data from full scale launch vehicle explosion tests and accidents was assembled. Crew survivability from catastrophic explosions could be increased in this way [9]. Compared with test research, numerical simulation methods have some advantages, including reducing costs, improving efficiency, and facilitating parameters analysis. [PERSON] et al. conducted the assessment based on an interpretation of these data via analytical semiquantitative estimates and numerical simulations of simplified models for the whole range of the physical phenomenon governing the outcome of a propellant-tank breach [10]. [PERSON] et al. assessed a specific failure resulting from a catastrophic disintegration during ascent of the crew launch vehicle liquid propellant tank and determined the time scales of the various processes and the strength and propagation of the blast wave if the mixture ignites [11]. [PERSON] et al. presents air blast and fragmentation hazard analyses during processing of launch vehicle in the Vehicle Assembly Building as well as consequence and risk analyses to provide added information for the decision maker [12]. [PERSON] al. studied explosive yields for Delta heavy vehicles in the explosion mode of impacting the ground with different distances and angles [13]. Explosion is a complex multidisciplinary problem that involves combustion, fluid dynamics, thermodynamics, structure/fluid interaction, and shock physics for high-speed flows, especially the accidents. The physical process governing the breakup and vaporization of the bulk liquid propellants are extremely complex with a variety of phenomena such as flashing, aerodynamic gas/liquid mixing, and vaporization occurring concurrently. The launch vehicle makes this even more complex in that the vehicle is accelerating upward with the atmospheric conditions changing with altitude and vehicle velocities. The TNT (2,4,6-Trinitrotoluene) equivalent model is a good method using worst-caseassumptions to define the potential explosions risk in an attempt to envelope the blast environment for crew module  
The liquid propellant explosion test has high risk and high cost, and the experimental conditions are strict and the repeatability is poor, which makes the test difficult. With the development of computer simulation technology, numerical simulation has become the main method to solve such problems [14]. Blast loads in simple geometries can be predicted by using empirical formulas. In a more complex model with rocket, one approach is to use numerical tools such as LS-DYNA [15] to provide reliable estimates of the effects of adjacent structures on the blast loads. Numerical simulations can be used to extend the database of blast effects on the crew modules. Experiments have been conducted to validate the numerical simulation techniques against blast load experimental results. Numerical simulations can help to understand the hazards to the crew module of the blast wave. While detailed experimental investigations are not easy to perform, numerical simulations can close that gap. Hence, the number of field experiments can also be reduced by using numerical simulations. While an experimental investigation captures mainly one scenario, numerical simulations can be used to investigate a multiplicity of threat scenarios [16]. [PERSON] et al. simulated the peak overpressure and attenuation law of blast wave of liquid propellant explosion in the air by using AUTODYN software [17]. [PERSON] and [PERSON] et al. used the accident consequence analysis software PHAST to study rocket explosion hazards on launch pad, predicting the scope of the rocket explosion hazards, and dividing the safety distance with the relevant criteria [18; 19]. However, hazards for the rocket explosion on launch pad and the crew module exposed to the blast wave have received relatively little attention.