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View Diary: UPDATED: Quietly, SpaceX makes a revolutionary launch (67 comments)

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  •  How do they control attitude of the 1st stage (2+ / 0-)
    Recommended by:
    foresterbob, FarWestGirl

    when it reignites?  Or does it just naturally fall with the engines facing down?

    •  There are small rockets (7+ / 0-)

      near the top of the first stage that control rotation around the x and y axis. Not sure if that includes rotation around the longitudinal axis (which is the vertical axis normally), but that's not really too important anyway.

      The smaller rockets are called "Draco" engines, and several of those will also be used in the upcoming man-carrying Dragon capsule as escape engines.

      We are all in the same boat on a stormy sea, and we owe each other a terrible loyalty. -- G.K. Chesterton

      by Keith Pickering on Sun Sep 29, 2013 at 03:26:33 PM PDT

      [ Parent ]

      •  Looks like they need to work on roll control. (3+ / 0-)
        Recommended by:
        eOz, buddabelly, FarWestGirl

        I suppose in theory, the 1st stage would have enough in the way of RCS thrusters to control pitch, yaw and roll.

        But in this launch, the 1st stage started rolling uncontrollably when it was doing it's final burn in the landing test, and that caused all the fuel to spin out to the sidewalls of the tank, causing the engine to go out.

        Well, that's why they do tests.

    •  And yes, the first stage should normally (6+ / 0-)

      fall engines-downward, because that's where the weight is when it's unloaded: at the bottom. Just like a arrow with a heavy arrowhead.

      We are all in the same boat on a stormy sea, and we owe each other a terrible loyalty. -- G.K. Chesterton

      by Keith Pickering on Sun Sep 29, 2013 at 03:28:47 PM PDT

      [ Parent ]

      •  Two domains here... (2+ / 0-)
        Recommended by:
        FarWestGirl, elfling

        1) Above 200,000' or so, the air is so thin that the first stage is in free-fall. Up here, small rockets can orient the stage readily; drag has relatively little effect.

        2) Below 200,000' or so, the starts to thicken and have effects. If the first stage hits this rockets first, it should continue to fly stably in that configuration. If it should arrive in a transverse or upside down configuration, it would likely be broken up by the aerodynamic loads as it tried to flip ends. (IIRC, an X-15 was lost when it broke up due to a control failure that caused it to be misoriented when it returned into atmosphere.)

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