By looking at historical schedule and cost growth, the past can be used to established reserve guidelines for future missions. This paper looks at recent NASA cost and schedule growth history, categorizes the reasons for growth, isolates growth due to external programmatic reasons versus internal technical reasons, assesses relationships for causality and provides guidance for the proper cost and schedule reserves to be carried at both the Program and Project levels. Mission cost and schedule growth history from both planetary and Earth-orbiting programs, such as Mars Exploration, Discovery, Medium and Small Explorer, Earth System Science Pathfinder, New Millennium and others, are investigated. The reserve guidelines developed are compared to industry standard guidelines and rules of thumb to determine if these standard practices continue to be valid.
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