In this study, a numerical analysis for predicting the internal pressure of the flight vehicle system with relief valve and N2-injection type cooler was conducted to operate the system safely in an unsteady-state condition. By adopting an incompressible ideal gas equation to computational domain at each time step, internal pressure was calculated without iteration. To increase the accuracy of the numerical analysis results, numerical model was correlated by modifying the volume of the computational domain. To modify the volume of computational domain, internal pressure along time was compared with experimental results. It showed good agreement within system operating time. Air mass flow rate at the relief valve is calculated by interpolating the performance curve data. For accurate and rapid calculation of the internal pressure in an unsteady-state condition, time step size convergence study was conducted additionally. By using a correlated numerical model, Pcr of the relief valve is conducted to remain the flight vehicle system within an internal pressure range of 0.6-2.0 atm, in each flight profile. Finally, specific Pcr of relief valve was applied to the system and the experimental results showed that the internal pressure remained in a safe range.

For this study, A vibration attenuation of the vibration absorber that is attached to the flight structures was carried out. Flight structures are stabilized to allow for operations in various operating environments; however, as the size and weight of the flight structures are reduced, to meet the requisite performance, the operating-environment-induced vibrations lead to a degraded operating performance; therefore, the reduction of these vibrations should lead to an increased operating performance. The vibration absorber includes a compliant energy-storage device, such as a spring, and is mass secured to the energy-storage device. In this study, the research to prepare the anti-vibration design of the flight structures was accomplished, and the vibration of the flight structures was analyzed using the finite element analysis; accordingly, a vibration experiment for the verification of the result of the finite element analysis was also conducted. Further, the design guidelines of a tuned mass damper were obtained.