National Aeronautics and Space Administration safety watchdogs are flagging their concerns about the agency’s plan to transport astronauts into orbit using private spacecraft built by SpaceX and Boeing. Originally scheduled to start last year and now pushed back until at least 2019, the commercial crew transportation program came under fire Thursday from a safety panel commissioned by NASA. The panel stressed that unconventional rocket-fuel systems and the bombardment of aircraft in orbit by tiny meteor fragments and space debris raised the statistical probability of fatal accidents to an unacceptable level. (The agency had set a bar of no more than one fatal accident per 270 flights.)
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