This paper summarizes the findings of a comprehensive study commissioned by NASA’s space architect and conducted by graduate students and faculty at MIT during spring 2004. The goal of the study was to broadly analyze implications of NASA’s new space exploration initiative at the value, system architecture and vehicle levels. The space exploration system is expected to accomplish a wide variety of defined and undefined mission objectives throughout its lifetime, while doing so with limited resources. As a result, the traditional view of designing an optimal system that satisfies current mission objectives is no longer an effective design approach. A new approach is needed in which the system’s lifecycle is considered throughout the design process, and environmental factors such as political and budgetary uncertainty are incorporated alongside more traditional factors such as technology development and scientific interests. To promote a sustainable system design, the first step in the design process is the identification of the true value delivered by the system to its stakeholders. In this paper we argue that the true value of an exploration system is knowledge acquisition, not simply transportation of humans and cargo to planetary surfaces. The new design process is defined and then applied to the space exploration system with decisions and analysis guided by knowledge delivery as the ultimate purpose, resulting in the design of a sustainable exploration system.