crandles wrote:
> Eric Swanson wrote:
> >
> > This is  81 million metric tons, still a very large quantity, to be
> > sure.
>
> Certainly still a very large quantity if you are talking about lifting
> from earth's surface into orbit. Just wondering about attaching a solar
> sail to an asteroid to alter its course towards an fly past another
> asteroid so that it heads towards the La Grange point (with further
> steering via the solar sail). How much material could be transported to
> the LaGrange point in this manner? Sure, flattening it could be
> challenging to say the least but should such ideas be rejected without
> consideration?

You appear to be forgetting orbital mechanics.  Moving an astroid from
one orbit to another involves deceleration as well as acceleration.  A
solar sail won't stop the mass, once it has been placed in an orbital
trajectory from the astroid belt toward the L1 point.

http://www.esa.int/esaSC/SEMM17XJD1E_index_0.html

> I appreciate the comments about active control being a problem. If any
> odd mass could be used for some sort of drive, then the mass can
> probably be provided cheaply enough from somewhere other than earth. It
> is engineered mass that would be expensive.

Yes, please note that the calculations were for a mass of aluminum.
The very thin reflector would need to be kept perpendicular to the
Sun-Earth vector, which would require that there would need to be
active control.  The structure would need to rotate once each year to
match the change in the direction of the vector.  Even if many smaller
satellites were placed in orbit at L1, I think this would still be a
very big problem.


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