8 thoughts on “The Atlas V”

    1. Trent,
      Maybe. Cygnus was ~90% of the capacity of an Atlas V 401 to that altitude. Not all DoD launches use >90% of the launch capacity of the Atlas they fly on. And most of them are going to higher altitudes which means for most DoD launches they probably would’ve failed to reach their target orbit, but come close enough that the payload might have been able to make up the deficit (but at a big hit to orbital lifetime). Which isn’t quite as bad as putting it into the drink, but still would clearly be a mission failure, and still is something that ULA will probably work their backsides off to avoid happening.

      ~Jon

    2. Trent,
      Maybe. Cygnus was ~90% of the capacity of an Atlas V 401 to that altitude. Not all DoD launches use >90% of the launch capacity of the Atlas they fly on. And most of them are going to higher altitudes which means for most DoD launches they probably would’ve failed to reach their target orbit, but come close enough that the payload might have been able to make up the deficit (but at a big hit to orbital lifetime). Which isn’t quite as bad as putting it into the drink, but still would clearly be a mission failure, and still is something that ULA will probably work hard to avoid happening.

      ~Jon

  2. Nice story. ULA did very well to pull out a success. Awesome that the software can recompute so many complicated factors, so quickly.

  3. The RD-180 must have been running very O2 rich to cause that much of a shortfall, and running that O2 rich would cause the chamber temps to go far above normal. The RD-180, when operating normally, is really pushing the boundaries, so I’m amazed they didn’t have a RUD.

    They are indeed fortunate that they happened to have the margins on this flight to allow it to be saved.

    I also (I think?) learned something from this article regarding F9/Dragon launches to ISS – the reason why F9 has to use an instantaneous launch window, while Atlas has a 30 minute window. Apparently, the difference is the guidance system on the F9, which can’t do the right ascension of ascending node adjustments on the fly the way Centaur can.

    1. No, the reason is that they don’t have the performance margin. Even a minimum Atlas is way oversized for a Cygnus mission to ISS. That’s what saved them with this anomaly.

      1. Thanks.

        I figured that was true in the past, but with the new F9 1.2 (or full thrust) version, I didn’t think it was true even with RTLS margins.
        However, it looks like I was underestimating the mass of Dragon plus the trunk cargo.

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