Comment Re:Top Speed ? (Score 2, Informative) 229
Also, maneuverability, as I just don't see most of those sailing techniques working in a vacuum.
Solar sails don't, and have never been intended to, use "sailing techniques". In that sense "solar sail" is an unfortunate misnomer. Solar sail maneuvers typically take advantage of the fact that changing the sail orientation enable you to direct the resultant force from the solar radiation pressure either along or counter to the orbital velocity vector. Depending on which way you point the sail you either increase or decrease your orbit energy. Increases in orbit energy correspond to increases in orbit radius (or semi-major axis if in a non-circular orbit), while decreases in energy decrease the radius of the orbit. There's no "tacking" in the sense of ocean sailing.