USA-193 Interception

From: Bob Christy (
Date: Tue Feb 19 2008 - 14:00:10 UTC

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    Using the Fengyun interception as a reference, the evidence is that the
    interception cannot be treated as the sort of ballistic collision that we
    saw in school science experiments.
    At the point of collision, two objects will come together with a closing
    speed near that of orbital velocity. The catastrophic disruption of USA-193
    and its interceptor will produce a debris cloud spreading evenly in all
    directions but, overall, still having USA-193's original orbital
    Witin the cloud will be a collection of trajectories near to the original
    inclination but spreading either side, and there will be a range of apogees
    and perigees due to the vertical component of the spreading.
    Fragments leaving the cloud with the lowest orbital velocity will hit the
    upper atmosphere fairly quickly - it's a little like Soyuz or Shuttle having
    fired a retro-rocket. My guess (intentional word) is that the first
    re-entries will occur about one quarter to one half orbit after the
    fragmentation. The remainder will be spread over a number of days.
    The choice of the interception orbit ground track is a very good one.
    Optical observation is possible immediately after the collision, and the
    next three circuits of the Earth pass over very little land. 
    The area laid out in the NOTAM is not to defined catch post-collision
    fragments because there will not be any heading in that direction. The SM-3
    missile is three-stage so the area covers the splashdown of stages 1 and 2,
    and, in the event of a miss, stage 3 and it's warhead also.
    I have posted some expanded notes and some maps here:
    Bob Christy
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