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Gravity Assist-Elliptical Trajectories

  1. Apr 26, 2014 #1
    Good evening,

    I am working my way through a JPL technical report I found online at


    Specifically, I am at page 17 which looks like


    and I am trying to understand the relation


    I basically, don't understand where this relationship comes from and why it is necessary.

    Any help would be appreciated.

  2. jcsd
  3. Apr 27, 2014 #2
    Well, there is a mistake in that equation. There should be another term inside the square root. The missing term is (r2)2. That triangular inequality simply expresses that r1' and r2' must add to something larger than the distance between P1 and P2 which can be found from r1, r2, and θ by use of the law of cosines.
    Last edited: Apr 27, 2014
  4. Apr 27, 2014 #3
    Thanks Dauto
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