Investigation of modal properties and layout of elastomer diaphragm tanks in telecommunication satellite

Abstract

Elastomer diaphragm tanks have been adopted in many spacecraft applications, such as upper stages, space platforms, commercial and civil spacecraft as a propellant tank in which liquid propellant is covered with a diaphragm and compressed into a combustion chamber by gas pressure. Investigating the dynamic response and the influence of various parameters on the modal properties is a significant issue in the modeling of the space diaphragm tanks. In this work, the numerical study is presented to investigate the modal properties of a spherical fuel tank in both uncovered and covered cases with a flexible diaphragm as fluid–structure interacting situations. The filling volume ratio of fluid ranges is from 25 to 50%. Numeric dynamic simulations created by ANSYS software are verified by the experimental results of test tank and then, the validation of the numeric model is used to determine the natural frequencies and mode shapes of really elastomer diaphragm tank as the second case study for two conditions: fluid filling volume ratio of 80% that the tank is in full load condition and liquid filling volume ratio of 14% when the diaphragm completely inverted. After that, the best layout of diaphragm tanks in two-story satellite is detected by calculating deviations from center of gravity and cross moments of inertia objective functions in multi objective optimization software. Then the natural frequencies of satellite include diaphragm tanks computed and compared with natural frequencies and static loads of launch vehicle requirements. The achieved results of this study showed that the numeric simulations are able to renovate the experimental vibration characteristics of the diaphragm tank with a good precision. In addition numeric model can detect the best layout of diaphragm tank components.