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Re: Orbit B

re Timothy van der Linden)

> >> All this is irrelevant, computers could calculate the path far in
> >> Besides that, the Asimov could follow the beam (up to certain limits).
> >
> >
> >Ha, you have a lot of misplaced faith.  Calculations only work when you
> >rely on acurate data.  In this case the data would be months old, and
> >have no way to know exactly what happend in the mean time.  Any slight
> >deviation or flutter (inevitable with these huge flimsy structure) and the
> >ship would not be doing exactly the speeds and accelerations we think it
> >would.

> But this means that any beam, from Earth or from some kind of retro-mirror
> would be impossible! (In fact this is one of the reasons I never really
> liked using a beam and always tried to think of taking all fuel along)

You'ld have to have a fixed aim beam of huge proportions.  Say 10-100 times
the diameter of the sail (maybe it would need to be more?).  No I don't think
the reflectors would work.

> Anyway since the retro-mirror flies in front, it would know what the path
> would be like for the Asimov, so it could calculate where
>  to direct using that data. 

But the ship would be reacting to the stern thrust of the earth beam months
before it would get to the mirror, and the mirror could respond.  Besides how
could you keep the mirror perfectly focused with all the random fluxuations
in the beam?  Keep the reflector tuned exactly to the sail, or know if the
sail drifted a little due to problems, or back thrust from earth (that the
reflector wouldn't see for months).

How the hell do you focus a lose flapping mesh sheet, the size of jupiter,
while its taking 100s-1000's-? of G in acceleration?