This paper addresses the challenges encountered in planning and developing the next generation space suit as NASA embarks on the ensuing phase of human exploration with the Constellation Program (CxP). The enabling portion of this program is the development of innovative spacefaring vehicles and space suits, to meet the extreme environments using ground-breaking methods not yet attempted. (1,2,3) In the summer of 2006, the Constellation Space Suit Element (CSSE) 4 was challenged by the CxP to develop a single-suit system that will enable astronauts to not only survive, but to perform work nominally for severe environments such as: cold water Earth survival; launch, entry, and launch abort survival; long-duration vehicle depressurization survival, scheduled microgravity extravehicular activities (EVAs); lunar and Martian surface EVAs; lunar and Martian emergency survival situations; off-nominal landing accelerations; and extreme thermal and chemical survival in and around the launch and landing vehicle hardware. Historically, multiple suits were used to manage these diverse environments. These environments were commonly divided into multiple missions or an accepted level of risk was associated with certain mission phases, and minimal, if any, protection was provided. In the human, space-faring political environment of today, the acceptable risk is minimal and overlapping missions challenge NASA space suit engineers to rethink the approach to space suit design. Today's engineers must consider how suits should function and how to address mutually exclusive and opposing requirements while maintaining maximum performance and functionality, all while minimizing launch mass and maximizing safety. The EVA Systems CSSE addressed this challenge by fully embracing "clean-sheet" or "textbook" systems engineering methodology by first defining the operational concepts, which focused on the development of an architecture with all defined design reference missions (DRMs) and an eye on life cycle program costs. Historically, NASA has not exercised all of these methodologies completely, either due to existing contracts modified to allow NASA to achieve deliverables or missions, or because heritage or legacy systems were used, which were developed before systems engineering became a formal discipline. Once the needs, goals and objectives were identified, the operational concepts and functional requirements were documented and a resource- loaded project schedule and budget, based upon the requirements, was defined. The CSSE then proceed with trade studies, prototype development, and technology development to validate these requirements in addition to embarking on preliminary design while documenting, trade results, architecture changes and philosophy, as well as design decisions. A comprehensive review of the functional designs, strengths, and limitations of previous U.S. space suits, in addition to what is known of Russian space suits, took place to deduce historical lessons learned based not only on what did not work, but more importantly, to learn what worked right. The current strategy to accomplish the rather daunting task of meeting all space suit design requirements in the extreme environments previously detailed with a single system hinges on an arrangement that not only uses common hardware across multiple mission phases (to reduce developmental and logistics costs), but features an open architecture that can be reconfigured and can leverage off components used during other mission phases, where possible.
