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Re: Re: RE: starship-design: Re: Perihelion Maneuver

In a message dated 11/24/97 11:45:08 AM, kuo@bit.csc.lsu.edu wrote:

>KellySt@aol.com wrote:
>>In a message dated 11/18/97 4:03:33 AM, lparker@cacaphony.net wrote:
>>>On Monday, November 17, 1997 11:23 PM, Isaac Kuo
>>>> No, it still needs a fresnel lens.  Without it, diffraction limits
>>>> are too severe.  The beam needs to fall on a spot 1km wide at a
>>>> range of 30,000,000,000km.  With a wavelength of 1mm, that requires
>>>> an aperture around 30,000km wide.  Don't tell me you're going to
>>>> make a microwave laser that big.
>>Why?  I thought everyone was prewtty comfortable with a phased array
>>cluster?  (See details in recent Fuel/Sail is dumb responce)
>It doesn't work.  I came up with the idea (and if I wasn't the one
>who suggested it, then I came up with the idea independently).
>However, it doesn't work.  This is actually pretty obvious when you
>do the numbers.
>A cluster of in phase emitters can only acheive the emitted power/m^2
>equivalent to a single emitter with an aperture of the same total
>aperture area.  However, this cluster is less effective than that single
>emitter in that this power/m^2 is emitted onto a smaller spot (the
>rest is lost in sidelobes).
>If you wanted an array to take the place of the single emitter, the
>best way would be to have an array of emitters sitting "shoulder to
>shoulder" in a hexagonal grid.  It still needs to be 30,000,000,000km
>in diameter, with lenses flush against each other.

Saying its not as efficent as a single emmiter, isn't the same as saying it
won't work.  Given you couldn't build one single emmiter of the size needed
to get the resolution needed.  We need a phased array system.  (Also the
phased array make construction repair and reuse of the beamed energy after
boosting easier.)

How inefficent is it?