Some of the ideas are long-standing concepts, while others are relatively new. Many of the safety-related upgrades, for example, arise from contractor sustaining engineering based on ongoing evaluations of flight and test data, anomalies, failures, and mishaps. Many obsolescence and supportability upgrades originate from USA corporation logistics activities. The Space Shuttle Program Development Office coordinates the flow of all new upgrade concepts through the study, analysis, and approval system. Prioritization is necessary because there are many more upgrade candidates than dollars to fund them.
Many factors influence the prioritization process.
Another is the projected cost of developing and implementing the upgrade, including cost savings that would result from the change. Advice from within the agency, including the HEDS enterprise, the Safety and Mission Assurance Office, and the NASA Advisory Council, as well as from outside sources, such as Congress, the Aerospace Safety Advisory Panel, and the National Research Council, may also be considered. Several tools are being developed to support the upgrade prioritization process. The agency is also beginning to use quantitative approaches more often to help prioritize nonsafety-related upgrades. However, these quantitative tools are only one component of the decision process, which includes many other technical and programmatic considerations.