Re: Yet more FengYun debris

From: Christian Kjrnet (
Date: Wed Feb 14 2007 - 16:44:14 EST

  • Next message: George Olshevsky: "Re: Yet more FengYun debris"

    I don't know what launch site was used, but I doubt very much that the
    ASAT-weapon performed a high-speed U-turn, which could cause the weapon to
    disintegrate from high g-forces.
    There is of course the possibility that the ASAT-weapon was launched from a
    fighter jet, similar to the U.S. test launch of an ASAT-weapon from a
    specially instrumented F-15.
    I still have not found any debris pieces from the Chinese test 11 January
    that are traveling in the opposite direction of the target satellite (i. e.
    with an inclination of ca. 81.4 degrees). This leads to the conclusion that
    the target was indeed struck from behind and the impact between the two
    bodies created debris pieces in orbits with similar inclination around 98.6
    degrees, as I explained in the previous message to the list.
    This also means that the ASAT-weapon must have had an orbital speed larger
    than the target at impact, leading to a majority of debris particles
    traveling in orbits with apogee larger than the target, Feng Yun 1C,
    original orbit.
    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.
    The piece with the present largest apogee and with perigee of ca. 850 km
    provides an indication of the minimum limit speed  of the ASAT at impact:
    The speed of the ASAT must have been greater than 7.1 km/s at impact in
    relation to Earth's surface, or more than 550 m/s faster than the target
    satellite speed - that's like a fast cannon projectile, only this one was
    much larger!. Still, it did hit the small target satellite, max 27 feet
    Christian Kjśrnet
    On 14-02-07 11:10, "Marco Langbroek" <> wrote:
    > Christian Kjśrnet wrote:
    >> Given that all the debris pieces now travel in the same direction as the
    >> target and in about the same orbital plane, one can conclude that the ASAT
    >> weapon did strike from behind, with approximately a coplanar trajectory
    > In that case Xichang cannot have been the launch site of the interceptor. The
    > missile then would have had to make a complete U-turn.
    > - Marco
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