Reliability Calculation of Satellite Propellant Tank Using Stress-Strength Interference Model

The propulsion system plays a critical role in satellite missions, with propellant tanks serving as one of the vital components. These tanks ensure a continuous and gas-free supply of propellant to the engines, underscoring their critical role in mission success. The failure of a propellant tank can result in catastrophic mission failure or even loss of life in manned missions. Thus, assessing the numerical reliability of such tanks becomes imperative. The propellant tank discussed in this paper is an all-titanium container with spherical shape experiencing hoop stresses due to internal pressure. The present paper explores the stress-strength interference model method for evaluating the reliability of a satellite propellant tank, elucidating the assumptions made during the reliability calculations. Statistical method with the assumption of normal distribution of stress has been adopted as there is much evidence that the material strength associated with static stress occurs as a normally distributed function. The maximum stress points on different locations of the tank at operating pressure were identified through stress analysis. Subsequently, a stress-strength model was employed to calculate tank design reliability. The predicted value is compared with the estimated reliability based on past ISRO satellite data since the 1980s. This work will be useful in calculating the reliability of propellant tanks or pressure vessels utilized in ISRO spacecrafts.