radius vector The line joining an orbiting body to its center of motion at any instant, directed radially outward. For a circular orbit, the center of motion coincides with the center of the circle; for a parabolic or hyperbolic orbit, the center of motion is the focus, and for an elliptical orbit it is one of the two foci. Related category • CELESTIAL MECHANICS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |