Astrophysics and Space Science

, Volume 11, Issue 2, pp 191–221 | Cite as

The relative motion of two spheroidal rigid bodies, II

  • Paolo Lanzano


This study constitutes the second phase of an effort devoted to the relative motion of two spheroidal rigid bodies.

An isolated binary system was considered whose components are bodies: (1) of comparable size; (2) of constant density; and (3) having the shape of an oblate ellipsoid of revolution with small meridional eccentricity.

The equations that determine the relative motion of the centroids and the angular motion for the two sets of body axes constitute a simultaneous system of seven nonlinear, second-order differential equations, for which solutions were obtained as power series in the two meridional eccentricities.

A recurrent procedure was formulated to ascertain the various approximations in terms of lower order terms; it gave rise to linear differential equations with constant coefficients for the angular variables and to differential equations of the Hill type for the other coordinates. The zero-order approximation for the motion of the centroids was assumed to be a Kepler elliptic orbit of small eccentricity.

The following contributions were made:
  1. (1)

    The general solution to the zero-order approximation of the rotational motion was obtained in terms of elementary functions;

  2. (2)

    Certain functionals, related to the Kepler motion and depending on two parameters, were expressed in terms of the mean anomaly up to the sixth power of the orbital eccentricity in order to evaluate the lower order terms of the various approximations;

  3. (3)

    The secular terms were eliminated from the first-order approximation;

  4. (4)

    The second-order approximation was also obtained; and

  5. (5)

    An alternate procedure was suggested that might be more appropriate for achieving higher order approximations.



Relative Motion Linear Differential Equation Elliptic Orbit Angular Motion Lower Order Term 


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Copyright information

© D. Reidel Publishing Company 1971

Authors and Affiliations

  • Paolo Lanzano
    • 1
  1. 1.North American Rockwell CorporationDowneyU.S.A.

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