Laser Aperture Size

["L. Parker" <lparker@destin.gulfnet.com>]

Applying basic optical diffraction theory (Rayleigh's Criteria) to determine
the required aperature (diameter) of the laser transmitter, using 0.5um
yellow light and have it just fill the sail 11 light years away at TC, the
aperature would have to be 400 km. Was somebody worrying about staying in
the beam? Better worry some more, it isn't going to be as wide as they were
thinking!

As far as your mirror problem, why bother? Why not just pass TC by, use
Lorentz Force Turning to swing around on a return course and then use the
original beam to decelerate into the TC system from behind?

Of course, this makes the mission longer....

The Fresnel lens has already been discounted on the basis that it introduces
chromatic aberrations into the beam, rendering it largely useless. A
reflecting optical system would work better.

If you must do it with mirrors, there is no need to get complicated, just
build a staged design (kind of like onion rings) where the main ship detachs
large chunks of sail to function as a deceleration stage, then a slightly
smaller chunk as an acceleration stage to leave TC, and decelerates back
into Sol on the unreflected beam. Each stage would function as a mirror to
propel the remaining ship and sail sections in the appropriate direction.
This method would probably still require a Fresnel lens though.

As much as I like the sail concept, I still think the RAIR concept is more
promising. Especially if you can boost fuel into its path to increase its
cruise velocity. I like the idea of using sails for the fuel, though.
Lee
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+  Weave a circle 'round him thrice, and close your eyes with holy dread...   +
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