Key Reliability Drivers of Liquid Propulsion Engines and A Reliability Model for Sensitivity Analysis

This paper is to address the in -flight reliability of a liquid propulsion engine system for a launch vehicle for a flight mission . We first establish a comprehensive list of system and sub -system reliability drive rs for any liquid propulsion engine system. We then build a reliability model to parametrically analyze the impact of some reliability parameters. We present sensitivity analysis results for a selected subset of the key reliability drivers using the model . Reliability drivers identified include : number of engi nes for the liquid propulsion stage , s ingle engine total reliability, engine operation duration, engine thrust size, reusability, engine de -rating or up -rating, engine -out design ( including engine -out switc hing reliability, catastrophic fracti on, preventab le failure fraction, unnecessary shutdown fraction ), human rating and crew escape system, propellant specific hazards, engine start and cutoff transient hazards, engine combustion cycle s, vehicle and engine interface and intera ction hazards , engine health management system , engine modification, engine ground start hold down with launch commit criteria, engine altitude start (1 st start), Multiple altitude restart (> 1 restart ), component, subsystem and system design , manufacturing/ ground ope ration support /pre and post flight ch eck outs and inspection , extensiveness of the development program. We present some sensitivity analysis results for the following subset of the drivers : number of engines for the propulsion stage , single engine total reliability, engin e operat ion duration, engine de -rating or up -rating requirements, engine -out design, catastrophic fraction, preventable failure fraction, unnecessary shutdown fraction, and engine health management system implementation (basic redline s and more advanced h ealth management system s).