Digest Number 88

To do it properly, you would have active control surfaces, on the
perimeter,and exact center of the sail keeping the stationary. The
active control surfaces would use light pressure to steer the main
sail and keep it into position.

Bill

--- In spacesettlers@y..., "Combs, Mike" wrote:
> From: Ed Minchau [mailto:ed_minchau@n...]
>
> At 1kg/km^2, the parasol would be only a
> few kilometers further from the sun before it acheived a stable
> orbit, at 1 gram per square kilometer the difference is only about
> 25000 kilometers. (napkin calculation)
>
> It would not need thrust to maintain a stable orbit; the stable
orbit
> is just slightly closer to the earth than the libration point.
>
> Wouldn't that be slightly closer to the sun? I was thinking that if
we're
> talking about the Lagrange point between the Earth and the sun,
which would
> be a balance of the centrifugal force and the competing forces of
gravity
> from the sun and the Earth, and if the effects of light pressure
were
> exerting a force away from the sun, the way to balance it would be
to locate
> slightly closer to the sun, so that that slight decrease in gravity
from the
> Earth would balance the light pressure.
>
> The L1, L2, and L3 points are all unstable on one axis. In the case
of the