Re: Yet more FengYun debris

From: George Olshevsky (george.olshevsky@gmail.com)
Date: Wed Feb 14 2007 - 18:38:38 EST

  • Next message: Duncan Kitchin: "Re: Yet more FengYun debris"

    On 2/14/07, Christian Kjśrnet <ckjarnet@broadpark.no> wrote:
    
    > It's all simple mechanics of impact, really: Some pieces are the result of
    > an elastic collision (like two billiard balls striking, but keeping the
    > total energy maintained - the result is one piece with high apogee and
    > perigee ca 850 km, and the other piece with apogee ca 850 km and perigee
    > very low). Some other pieces are the result of an inelastic collision (like
    > two pieces of clay clinging together after collision and with some energy
    > dissipated at collision - the result is two pieces with perigee ca. 850 km,
    > and apogee a little higher). Most collisions seen here are probably
    > something in between the perfectly elastic and perfectly inelastic
    > collision. The total result is a mess of debris all over the orbital plane
    > and most pieces are still in orbit.
    
    My guess is that the relative kinetic energy of the impact was almost
    entirely dissipated in the resulting explosion. Above a certain
    relative satellite/impactor velocity, the momentum of the fragments
    has rather little to do with the momentum of the impactor; which is
    "lost" in the much greater momentum imparted by the explosion. If the
    impactor came from behind and it was not a very off-center hit, there
    would have been less relative kinetic energy and the fragments would
    have a significantly narrower velocity distribution than if it came
    from in front. Given the considerable spread in orbital elements of
    the resulting fragments, the collision must have been quite energetic,
    so I suspect the impactor arrived from ahead, where its velocity would
    be added to that of the satellite, not subtracted.
    
    There is a similar effect with respect to lunar craters. The shapes of
    the craters are pretty much circular regardless of the direction the
    impacting object arrived at, unless the direction was nearly
    horizontal. The craters are formed in almost spherical explosions.
    
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