# Prediction Method of Blast Wave Impact on Crew Module for Liquid Rocket Explosion on Launch Pad
###### Abstract  
The role of manned space flight in the field of space exploration and utilization is growing. However, the security system of the manned spaceflight is still imperfect. In the case that the rocket explodes, crew modules maybe damaged by the blast wave, which will threaten the safety of the crews. This research aims to obtain the necessary data and information to enable the designers of the launch vehicles and crew modules to develop safer launch systems. To this end, this paper proposes a numerical method using LS-DYNA to study the propagation law of blast waves caused by rocket explosion on the launch pad and to quantify the impact of the blast wave on crew module. The numerical results indicate that the final blast waveform of the model with rocket is conical in the upper and lower parts, and spherical in the middle. At the same time, the third-stage explosion is the most harmful to the crew module, while the first-stage explosion is the least. Furthermore, the model with rocket has a marked effect on explosion strength: the pressure enhancement factor is about 4-17 times. Most importantly, overpressure prediction formula acting on the crew modulesof explosion on the launch pad is established for quick peak overpressure predicting and damage evaluating. m m  
This point has been amply demonstrated by a series of explosion accidents over the past decades. The space shuttle Challenger exploded 73 s after launch in 1986, killing all seven astronauts on board. As was established by the Challenger investigation, the original source of the disaster was freezing of the O-ring in the lower section of the left solid booster and formation of a gas leak through the O-ring [1]. The Challenger disaster provoked studies of various risks that can lead to similar catastrophic events. In September 2016, the approximately 549 t Falcon-9 rocket exploded on the launch pad, causing $200 million worth of damage to the AMS-6 communications satellite. Moreover, Space X's main launch pad at the Cape Canaveral satellite launch base, severely affecting subsequent launch plans. The most likely cause of the accident was a leak of the helium system in the oxygen tank of upper stage. In April 2015, a Falcon-9 carrying 2 t cargo exploded just 139 s after launch, causing rocket destruction and delay in subsequent launch plans. The hazards to personnel and facilities around the launch site must be considered in safety analysis and assessment. Many workers studied liquid propellant explosion characteristics by conducting experiments and analyzing experimental data. Between 1963 and 1969, NASA and other units conducted a series of rocket explosion scaled tests using liquid propellants such as liquid oxygen/kerosene, liquid hydrogen/liquid oxygen, and studied the hazardous characteristics of liquid propellant explosion [2; 3; 4]. From 1962 to 1969, ADL (Advanced Distributed Learning) Corporation and the MIT (Massachusetts Institute of Technology) et al. managed the liquid oxygen/kerosene propellant tests of Saturn rockets during simultaneous mixing and separate mixing, to study the explosive yields of liquid propellant [5]. Between 1966 and 1968, [PERSON] et al. reviewed the hazards of liquid propellant explosion blast wave and determined the basic methods for blast wave research and hazard assessment [6]. To develop a better understanding of the magnitude and the character of explosions resulting from a breach of LH2/LOX tanks and to clarify the important questions about cryogenic H2/Ox explosion mechanisms, Hydrogen-Oxygen vertical-impact (HOVI) tests were carried out at the NASA Johnson Space Center's White Sands test facility [7]. NASA had been funding an ongoing development program to characterize the explosive environment produced by using the test and accident data available from public or NASA sources as well as focused scaled tests that are focusing on the near field environment that threaten the crew modules [8].