> > Spike Jones wrote:
> > > >...He suggested star sailing was not only impossible, but absurd,
> > > since solar gravity is stronger than light pressure, assuming a
> > > single atom thick layer of aluminum, and furthermore, solar
> > > gravity stays stronger than light pressure, regardless of the
> > > distance from the sun, since both drop off as the square of the
> > > distance.
> > >
Using a solar sail to thrust perpendicular to the vector of gravitational attraction is not necessary. Tacking across the solar wind to increase tangential orbital velocity is the key, and you do not need the solar wind to exceed gravity to do this.
Besides this, given a solar sail of a couple microns thickness over square miles of area is fine. The gravitational attraction is only important if sailmass X gravitationalacceleration > solarwindmass X windvelocity^2. The lighter the mass of your sail versus the area, the better.