Simulations for assessing potential impact of Ares I propellant tank common bulkhead failure

Detailed assessments of the potential risk and impact of various failure scenarios are being performed as part of the design evolution process for NASA's Ares I Crew Launch Vehicle (CLV). This paper uses numerical simulations to assess a specific failure resulting from cracks developing in the common bulkhead separating the liquid hydrogen (LH2) and liquid oxygen (LOX) sections of the CLV propellant tank. A parametric study is performed to characterize the rate of pressure rise in the tank sections due to vaporization of LH2 as it enters the warmer oxygen section as a function of crack surface area and ullage volume. Vaporization of LH2 can lead to a rapid increase in pressure and potentially threaten the structural integrity of the tank sections. When the pressure in the oxygen section exceeds that of the hydrogen section the flow direction reverses and warm two-phase mixture flows back into the hydrogen section. The results presented in this paper indicate that large common bulkhead failures are potentially most dangerous during the first two minutes after lift-off when the ullage volumes in the tank are small. Gravity is determined to have an attenuating effect on the tank pressurization rate, although the dominant effect on the pressure rise is the vaporization process. The simulations also indicate that the risk of sustained combustion is low since the propellants are cold and require large amount of energy for ignition.