Re: shoot down questions

From: Phil Karn (
Date: Thu Feb 21 2008 - 14:45:38 UTC

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    George Roberts wrote:
    > I read that this will be a kinetic only kill (no warhead explosion)
    > which implies that most of the delta v will slow down the satellite
    > pieces which might mean much of the debris will come down within half an
    > orbit.
    It's my understanding that at these extremely high velocities there is very
    little momentum exchange between the two colliding bodies. They basically
    liquify on contact and fly through each other. It's almost as if each exploded
    on its own at the same time and in the same place, but with their individual
    center of masses continuing on almost as if they hadn't hit. It's *not* as if
    the nearly-stationary impactor removed a big chunk of the spacecraft's orbital
    velocity and thus caused it to fall out of the sky.
    That has implications for the delta-v's applied to the fragments of the
    spacecraft (the impactor won't stay up as it's moving well below orbital
    velocity). That is, the fragments will fly out from the explosion but the center
    of mass of those fragments will remain in pretty much the same orbit as the
    spacecraft before the hit. Until their different altitudes and drag coefficients
    start to bring them down, of course.
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