Solar sail orbit operations.

摘要

The inherent capabilities of solar sails and the fact that they need no onboard supplies of fuel for propulsion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of asteroids. In this dissertation, both hovering points and orbiting trajectories about point-mass asteroids using equations of motion for a perfectly reflecting solar sail spacecraft are found as discussed in Chapter I. The orbiting trajectories are stable and offer good coverage of the asteroid surface, although restrictions on sail acceleration and spacecraft altitude are needed for smaller asteroids.; Variations are then made to the solar sail and asteroid size and shape in Chapter II. It is shown that even under these circumstances, hovering points and stable orbiting trajectories still exist. The effect of the imperfectly reflecting sail is seen to cause a diminished solar radiation pressure force along the sun line and modifies the possible hovering locations. The effect of a non-spherical asteroid is modeled by using the J ₂ gravity field contribution. Explicit predictions for the coupling between the (assumed dominant) solar radiation pressure and the gravity field perturbation are found.; Chapter III examines the idea of having a solar sail spacecraft use an Earth swing-by maneuver in order be in a position to go to an asteroid with a greater velocity when the best time opportunity comes. Simulations show that a sail can be flown toward the Sun and then back inside the Earth's gravitational sphere of influence with increased velocity such that the sail would then be in position to fly quickly toward an incoming Near-Earth Asteroid. Once the swing-by maneuver is accomplished, position and velocity of the spacecraft can be predicted in order to achieve a wide variety of situations for meeting Earth-approaching asteroids in shorter periods of time.