# Re: Orbit B

```To Kelly,

>> 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.

But I planned the retro-mirror would be at about the same size as the
earth-array. (Sounds awful doesn't it?)

>> 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.

No, the back- and forward beam aren't at the same place, they are at besides
each other.

>Besides how
>could you keep the mirror perfectly focused with all the random fluxuations
>in the beam?

With the capture and retransmit array (that has to be just about as large as
the beam)

>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?

I still don't agree with the size of the sail and the beam. The sail should
at maximum be 1 kilometre radius and the beam max 100 km radius.
And if we can make this thing work, I assume the accuracy could be made
better too.

The mirror would not accelerate any faster than the Asimov, since we are
smart enough to add some extra weight (if it isn't heavy from itself).

Tim

```