# RE: Orbit B

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From: T.L.G.vanderLinden
To: KellySt; stevev; jim; zkulpa; hous0042; rddesign; David; lparker;
bmansur
Subject: Orbit B
Date: Tuesday, March 05, 1996 11:50PM

Brian 5:10 PM CT 3/5/96

David?
>But I suppose it isn't critical for our discusion.  Assumeing a beam
>diameter 40 times the dimeter of earth.  4.76Km/s will still have you cross
>the beam in 31 hours.

>Tim
>Yes, but theoretically you could build the beam-array much farther away
from
>the Sun. I guess the only limit is where the gravitational acceleration of
>the Sun becomes less than that of nearer bodies or less than the
>acceleration caused by the beaming itself.
>Besides that, you assume the array is moving perpendicular to its beaming
>direction. Since the array is slowly moving in a circle it could start
>beaming at a time where it's own motion is in about the same direction as
as
>the direction of the beam. This way the perpendicular movement is much
less.

You guys seem to have forgotten that the reason why I wanted a slow orbital
velocity for the mirror is so that the massive thing  has less momentum to
overcome when it needs to brake into the beam for reaccel phase.  Because it
has been stopped in the beam and is now being pushed by the beam, it doesn't
have to worry nearly as much as falling out of it.

>Brian
>Don't we already have computers that could be programed to reasonably
>figure this aiming problem out?
>
>Kelly
>They could given current accurate info.  But given that the info has to
>travel at the spped of light, it would be months out of date by the time
>the mirror systems got it.  Given that the actuall rates will varry back
>and forth a bit durring the interveaning time (given random flexing of the
>sail, and random variations of the beam), and we can't predict what these
>variations will be.  The aiming calculations will be precise calculations
>bases on very bad information.  I.E. computer generated guesses.  Even
>assuming not one unexpected thing ever happens on the ship or mirror.  If
>you guess wrong even once.  You're aiming the beam into empty space and
>the ship is racing away from where you think it is.
>
>Just to complicate things.  The mirror is moring at a high fraction of the
>speed of light.  So relatavistic distortion will distort the beam, mirror,
>and apparent space.

Brian
What do you mean by  that last paragraph?  What kind of relativistic