A 2005 NASA report found that it could take seven flights of the next-generation Ares I rocket before the new vehicle exceeds safety standards to serve as a space shuttle replacement. The study recommended five unmanned cargo flights in addition to two test launches to ensure safety before astronauts were allowed to board an Orion crew capsule atop the Ares I. Today, by contrast, NASA asserts that the Constellation system will be safe for astronauts after just one unmanned flight -- a key contention in the agency's battle against using commercial rockets, as recommended by the Augustine Commission.

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