Spacecraft payloads are the sensing components that remain active over time and ensure Spacecraft's capability to perform multiple operations. It determines the rate of mission extension and the amount of scientific return based on extended performance. But it degrades over time due to the continuous process of operation and several space environmental factors. This paper has estimated payload mass fraction using the Spacecraft's data to relate it to the lifetime of orbital Spacecraft. Our prime intent is to check whether the spacecraft payload mass fraction affects the Spacecraft's lifetime concerning the initial hypothesis that the spacecraft mass greatly influences spacecraft lifetime. We derive some mathematical relation and establish a relationship between spacecraft payload mass fraction and lifetime. Finally, to verify our relation, we employ spacecraft data to investigate and interpret reliability behavior based on payload fraction and lifetime relation . Table of Conte nts 1. Acronyms and Subscripts ................................ ................................ ................................ ................................ .... 1 2. Introduction ................................ ................................ ................................ ................................ ......................... 2 3. Research Methodology ................................ ................................ ................................ ................................ ....... 2 4. Formulations ................................ ................................ ................................ ................................ ....................... 2 4.1. Spacecraf t Payload Fraction ................................ ................................ ................................ .................. 2 5. Relating the Spacecraft’s Payload Fraction with Lifetime ................................ ................................ .................. 3 5.1. Spacecraft’s Payload Fraction with Lifetime Relative to Gross Mass ................................ .................. 3 5.2. Spacecraft’s Payload Mass Fraction with Lifetime Relative to Gross Mass (Fueled & Unfueled) ....... 3 5.3. Estimating the Slope Parameter from Graph ................................ ................................ ......................... 3 6. Spacecraft’s Payload Fraction with Lifetime Relative to Dry Mass ................................ ................................ ... 4 6.1. Formulations ................................ ................................ ................................ ................................ ......... 4 6.2. Estimating the Slope Parameter from Graph ................................ ................................ ......................... 5 7. Results and Conclusion ................................ ................................ ................................ ................................ ....... 5 8. Acknowledgements ................................ ................................ ................................ ................................ ............. 6 9. Funding Resources ................................ ................................ ................................ ................................ .............. 6 10. Conflict of Interest ................................ ................................ ................................ ................................ ....... 6 11. Data Availability ................................ ................................ ................................ ................................ .......... 6 12. Supplementary Resources ................................ ................................ ................................ ............................ 6 13.