RE: starship-design: Beamed Power (was: Perihelion Maneuver)

["L. Parker" <lparker@cacaphony.net>]

On Monday, December 01, 1997 10:57 PM, Isaac Kuo [SMTP:kuo@bit.csc.lsu.edu] 
wrote:
>
> It is necessary because a coherent beam will travel with less spread.
> With a target spot of 1km, 1mm wavelength, and a target distance
> of 36,000,000,000km (2 week acceleration to .2c), an aperture with a
> diameter around 36,000km is needed.  Splitting that up into smaller
> emitters will require all of them to be emitting in the proper phase
> to produce a coherent beam.

Sorry, I should have explained myself better. I wasn't suggesting that an 
incoherent beam wouldn't spread, just that there were other ideas out there 
that ignore it.

There is/was a design for an extremely simple, MECHANICAL laser (trick 
optics) that could be easily mass produced. It incorporated it's own 
collector as part of the emitter and produced a collimated beam of 
incoherent (white) light. Technically, this isn't a laser, but it is darn 
close and because of the potential of mass producing them by the millions, 
you COULD build an array of them packed shoulder to shoulder 1,000 km 
across.

In essence, all it is doing is focusing 1,000 km of solar energy into a 
spot out to a considerable distance. True, since it isn't coherent, 
intereference will cause the beam to spread faster than a real laser, but 
the potential efficiency was limited only by the reflectivity of the 
material used to make the collector/emitter. It could go as high as 95 
percent. It vastly increases the acceleration envelope of a solar sail. It 
also has some interesting potential for industry.

Lee

                                                      (o o)
--------------------------------------------------oOO--(_)--OOo---------

Two people are traveling in a balloon over a landscape unknown to them.

"Where are we?" one calls down to a passerby.

The passerby looks carefully at them and finally yells back, "You're on a
balloon!"

"He must be a mathematician," says one of the travelers to the other.

"Why is that?"

"First, he thought awhile before answering. Second, his answer is
absolutely precise. And third, it's utterly useless."