The job of procuring expendable launch vehicle services for NASA's scientific missions has gotten more complicated since United Launch Alliance (ULA) discontinued production of the medium-lift Delta 2 rocket, which for years has served as a highly reliable and affordable workhorse. The production shutdown, driven by a U.S. Air Force decision to discontinue using the vehicle, left NASA heavily dependent on ULA's larger but far more expensive Atlas 5 rocket for launching its medium-size to large satellites. Meanwhile, back-to-back failures of Orbital Sciences Corp.'s Taurus XL rocket curtailed NASA's options for smaller payloads.
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