Spacecraft orbits under continuous radial thrust

The orbits of spacecraft under radial thrust in the two-body problem were investigated. Firstly, the equations of motion of spacecraft under radial thrust were established in inertial coordinate frame. And the characteristics of momentum and energy of spacecraft under constant radial thrust were analyzed; the analysis shows that the momentum vector is constant and the energy is determined by initial energy, the magnitude of the radial thrust acceleration, and the difference between radius and initial radius. Then, escape conditions of spacecraft under constant radial thrust were discussed through putting the energy to zero. Orbits under constant radial thrust were analyzed and classified into three types according to the escape conditions. Finally, circular orbits under constant radial thrust were studied. And the qualifications for spacecraft under constant radial thrust in circular orbits were obtained. And their orbits characteristics were compared with the corresponding Keplerian circular orbits which have the same radius or the same angular velocity (the same period).