[ExI] Trying for a minimum technical comment

[Tomasz Rola]

On Fri, 14 Dec 2012, Thirdeye Of Eris wrote:

> You plan to beam the power down by microwave? The slightest variation 
> would send the "beam" skittering across the landscape, burning 
> everything in it's path. This is why we have not sent up the satellites 
> that have been on the drawing board since the 70's...

I started to wonder myself and ended with some quick back of envelope 
calculations. First of all, if we try to send a beam from GEO, it's 
35000km. Let's assume we can position a pow-sat with 1 arcsecond accuracy, 
this translates to this many radians:

[7]> (/ pi (* 3600 180))
4.848136811095359936L-6

(L stands for E like in scientific notation, only here indicates I have a 
long double number)

So if our sat sways on the sides within 1 arc second range up there, it 
translates to the other end of beam going this many meters sideways 
(sinus of very small angle is equal to angle itself):

[8]> (* (/ pi (* 3600 180)) 35000000)
169.68478838833759777L0

So it ends up lighting up, burning things in about 85 meters radius from 
target.

However, according to page on HST:

[ http://en.wikipedia.org/wiki/Hubble_Space_Telescope ]

"HST's guidance system can also be used as a scientific instrument. Its 
three Fine Guidance Sensors (FGS) are primarily used to keep the telescope 
accurately pointed during an observation, but can also be used to carry 
out extremely accurate astrometry; measurements accurate to within 0.0003 
arcseconds have been achieved."

So our burn radius down on Earth can - in theory - be at least 100 times 
smaller (I assume the above mentioned possible accuracy would make it 3333 
times smaller but in real life it may be very hard to sustain it, so 100x 
should be both possible and sustainable). This gives inacuracies in beam 
placement in range of 2 meters down on Earth.

A pow-sat, being much larger than HST, should be easier to keep in right 
position and direction.

Of course I have neglected many factors that I don't know about (because I 
don't know about them) and I may have erred with calculations, so please 
correct me anybody.

Regards,
Tomasz Rola

--
** A C programmer asked whether computer had Buddha's nature.      **
** As the answer, master did "rm -rif" on the programmer's home    **
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**                                                                 **
** Tomasz Rola          mailto:tomasz_rola at bigfoot.com             **