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On Thu, 29 Feb 1996, Timothy van der Linden wrote:

> >> 2. I'm concerned about the size and weight of the maser sail.  Actually I'm 
> >> concerned about anything that has a diameter of a sizable moon.  Do you have 
> >> any good idea as to how much the sail will weigh?  After all, if it gets 
> >> much above say 100,000 tons (E5 tons), it will probably be too heavy to 
> >> carry enough RM to stop.
> >
> >The sail can have a large area to weight ratio, because it can have large 
> >(~2cm) holes in it.  Like chicken wire, only not as thick.  Because the 
> >microwaves have such a large wavelength, they won't even "see" the holes.
> Eh, Kevin why do you think that micro waves are called MICRO waves? Assuming
> you see what I mean, I think that you agree that such big holes are not allowed.

Ah, Tim, i was asusuming that a good frequency for the maser would be 
21cm.  as the ship approached earth on it's return flight, it would have 
a gamma of about seven, so the wavelength would be reduced by seven times 
to about 3 cm.  All other portions of the trip would have longer wave- 
lengths, or at least, no significant change.  I always assumed that they 
were called _micro_ waves, because compared to radio waves (which can be 
in the 1 meter range), 21 cm seems very small indeed.

Microwaves have longer frequencies than IR, and i know that IR is about 
1 cm or shorter.