is still struggling to develop a solid business case--including firm requirements, mature technologies, a knowledge-based acquisition strategy, a realistic cost estimate, and sufficient funding and time--needed to justify moving the Constellation program, witch includes the two main spaceflight components, the Ares I Crew Launch Vehicle and the Orion Crew Exploration Vehicle, forward into the implementation phase, the GAO stated.

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The GAO cites significant technical and design challenges for the Orion and Ares I vehicles, such as limiting vibration during launch, eliminating the risk of hitting the launch tower during lift off, and reducing the weight of the Orion vehicle that must be overcome in order to meet safety and performance requirements.

The GAO went on to say poorly phased funding that runs the risk of funding shortfalls in fiscal years 2009 through 2012, resulting in planned work not being completed to support schedules and milestones. The overall approach has limited NASA's ability to mitigate technical risks early in development and precludes the orderly ramp up of workforce and developmental activities, the GAO stated.