The International Space Station (ISS) represents one of the most challenging engineering projects in history. Even today, the size, complexity, and operating environment issues that were overcome to make ISS a reality set it as a benchmark for engineering excellence. This study looks at one specific challenge the engineering team faced, the design, delivery, and integration of a backup propulsion module to maintain the ISS in low earth orbit. This study is of interest because it included engineering as well as significant programmatic issues. As with many engineering studies there is no correct solution. Rather, there is a range of solutions each with favorable and less than favorable characteristics. This study illustrates the trade study process as well as how it was applied to better frame and to understand the feasible solution space for the design team.