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Re: starship-design: Re: Required microwave-antenna size. 100-light-year trip.

At 12:16 PM 10/28/96, Timothy van der Linden wrote:
>Kelly replied to me:
>>> To overcome difficulties, building it on a moon would
>>> not be a bad idea
>>No moon is large enough, nore would any point on them have a clear view of
>>the ship at all times, and/or a clear view of the sun (assuming you want
>>solar powered.
>I cannot agree with both:
>Moons can have a clear view all the time, you are probably thinking in 2
>dimensions. Think of the polar star, it never goes under the horizon (that
>is on most places of the Northern half of the World). So while some
>locations on a moon indeed won't have a clear view all the time, lots of
>other places on that moon will.

That would of course depend on which star your going to.  Few of interest
are near the poles.  Also I also mentioned a clear view of the ship and/or
sun.  Planets and moons rotate, so a solar powered maser array would have a
problem in local night.

>About the size, not being large enough, that depends on what interstellar
>distances we want, and what wavelength we are going to use. (See today's
>reply to Rex.)

I was assuming Rexes antenna size limits which would be to large for any of
our local moons.

>For a clear view, in the best case we can use an entire half of a moon to
>build on. (In the worst case we have nothing to build on, if our destination
>is within the solar plane).
>I've even been thinking of finding an asteroid and bringing it in the
>optimal orbit. I know this sounds as if I'm creating a bigger problem than
>the initial one, but all this depends on the mass of the asteroid. Getting
>not too heavy asteroids in the right orbit may take far less energy than to
>get our starship accelerated, since its final velocities are 4 orders of
>magnitude lower. (8 orders less energy needed)
>Of course one can also build a frame of lasers, instead of a lot of loose
>ones (as Zenon proposed), the problem I see there is that their weight may
>be too little, so that gets blow away too easely by its own "photon-recoil".
>(I have some ideas how to get rid of this, but some are a bit complicated.)

Photo recoil is a concern given the power levels were talking about, but
that assumes the transmitters aren't massive.


Kelly Starks                    Phone: (219) 429-7066    Fax: (219) 429-6859
Sr. Systems Engineer                                     Mail Stop: 10-39
Hughes defense Communications
1010 Production Road, Fort Wayne, IN 46808-4106
Email:  kgstar@most.fw.hac.com