This report describes the collision of the French satellite Cerise with a piece of Ariane rocket debris (object no. 18208) in 1996: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1997ESASP.393..589A&defaultprint=YES&filetype=.pdf

The approach angle between the two objects was 158.9 degrees (nearly head-on).

Near the end of section 4.4, the report states: "It is astonishing to note that the period and hence the semi-major axis of object no. 18208 increased during the presumed collision whereas the two objects were going in opposite directions. The delta-V in the trajectory of debris no. 18208 is in the direction of its velocity and not in the opposite direction."

Has the increase in delta-V of the Ariane debris ever been satisfactorily explained? If not, what are some possible explanations for how a near head-on collision of two orbital bodies could increase the period and semi-major axis of one of the objects?

  • $\begingroup$ +1 This is a really interesting question! A good answer will have several parts; 1) establish that this is really "astonishing" to begin with and not just counterintuitive, 2) find out if it has "ever been satisfactorily explained" and 3) include a summary of the explanation. $\endgroup$
    – uhoh
    Jun 21 '20 at 22:46
  • $\begingroup$ i.stack.imgur.com/08wTa.png from here $\endgroup$
    – uhoh
    Jun 22 '20 at 0:30
  • $\begingroup$ @uhoh this redirection you showed in the link would not add deltaV to the objects. The object redirected "upside" would gain Apoapsis hight, but it would lower the periapsis. And another point is: you cannot apply elastic bumbs in orbital speeds. $\endgroup$
    – CallMeTom
    Jun 22 '20 at 10:37
  • $\begingroup$ @CallMeTom what makes you think so? Can you demonstrate this rigorously using math? If so then that would address point 1) in my first comment. If not, then for now we'll just have to call it "counterintuitive". In the mean time, if a ping-pong ball and a bowling ball collide with equal and opposite velocities, does not the ping-pong ball recoil with a higher speed than before the collision? $\endgroup$
    – uhoh
    Jun 22 '20 at 10:42
  • $\begingroup$ @uhoh assuming both objects (1 and 2) in the figure you showed are on a (near) circular orbit, this would mean: a horizontal line is parallel to earths surface up is zenit, down is nadir. after the collision just looking at the "new orbit" would come from a lower alt and go to a higher alt, so it would be elliptical with a periapsis lower, and a apoapsis higher than before the crash $\endgroup$
    – CallMeTom
    Jun 22 '20 at 10:57

... what are some possible explanations for how [...to] increase the period and semi-major axis of one of the objects?

This does not work out for point masses, but only for extended masses: Imagine for example a dumbbell shaped object. Now imagine this object is spinning. One end of this object would be faster than the orbital speed, the other end slower, Center of Mass would have the orbital speed needed. Now, during the collision the pole-like part of the dumbbell would broke. This would result in 2 masses, one with a positive deltaV and one with a negative.


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