THE WRAPAROUND SUN

摘要

In it was shown that to escape the solar system using only a solar sail, there are big gains to be made by first flying as close to the sun as possible. This was quite a general result ― to pick up lots of speed, you should consider going where the photons are. In principle, an edge on sail could fly arbitrarily close to a tiny sun; but, in the real world, thermal effects put limits on how close one could fly. The main difficulty is that photons arrive from a spread of directions; so some heating occurs at all sail orientations, an effect that worsens the closer you go. A further complication is that the sun's visible disk does not appear uniformly bright. Data taken from is used to model this effect. The basic reflection and thermal models follow those of; but here, the incident power-is integrated over the visible solar disk. While how close you can go depends strongly on the details of sail design, a procedure is assembled for determining sail temperature and solar pressure force. Examples are given, based on plausible design parameters. The analysis becomes considerably more difficult if the sail attitude can exceed the "shadow limit"; i.e., if both sides of the sail are illuminated, a situation not encountered in the point sun approximation. Within the shadow limit, both temperature and force are analyzed; but, at this writing, only the temperature has been determined beyond the limit. It is hoped to complete the force analysis in future work.