Lifetime Qualification of Electric Thrusters for De ep-Space Missions

Electric thrusters intended for use on deep-space s cience missions have unique life qualification issues. Operational lifetimes of ten s of thousands of hours, operation over a broad range of input powers, and complex wear-out failure modes present significant challenges to the qualification of thruster life fo r a low risk of wear-out failure. The traditional approach of performing a single life te st for the require life plus some margin ‐ typically 50% ‐ provides insufficient info rmation to characterize the failure risk for a given deep-space mission. Validated, co nservative, deterministic analyses can be used to establish that most failure modes have s uch large margins against failure for the intended application that further detailed anal yses and tests are unnecessary. For the remaining few life-limiting wear-out failure mo des, the use of probabilistic failure analyses based on validated models of the important physical wear-out processes are required to assess failure risk. This paper provid es the rationale behind the need to qualify the life of electric thrusters for deep-spa ce missions through a combination of long-duration testing and probabilistic failure ana lyses.