International Space Station Approaches for Ensuring Utilization through 2020
“NASA’s approach to determining, obtaining, and delivering necessary spare parts to the ISS is reasonable to ensure continued utilization of the station through 2020. The statistical process and methodology being used to determine the expected lifetimes of replacement units is a sound and commonly accepted approach within the risk assessment community that considers both manufacturers’ predictions and the systems’ actual performance. To date NASA has given equal weight to manufacturers’ predictions and actual performance, and currently has no plans to reassess this decision. However, as time goes on, the resulting estimates could prove to be overly conservative, given that NASA has found failure rates for replacement units to be lower than manufacturers’ predictions.”
