[ExI] More ranting on power sats

[spike]

>... On Behalf Of david
Subject: Re: [ExI] More ranting on power sats

> On Sun, Aug 12, 2012 at 3:27 PM, spike <spike66 at att.net> wrote:
> 
> *>>…*solar power satellites…wouldn't work for up to 72 minutes a day when
> >> the earth eclipses anything in geosynchronous orbit…   John K Clark
> >>
> > ** **
> >
>> > ...Indeed sir? ...spike
> 
>>... Between February 28 and April 11 and between September 2 and October
> 14 the sun will be eclipsed by the earth every day for anything in 
> geosynchronous orbit, the time in shadow varies reaching a maximum of
> 72 minutes at the 2 equinoxes. It's particularly unfortunate that it 
> occurs at around noon local time the busiest part of the day...   John K Clark


>...I think you have misread the time. Geostationary orbits are eclipsed at approximately midnight on the point below them.

-David.
_______________________________________________

Good catch David, I missed that too.  I was too busy trying to mentally estimate the penumbra time of a geosat, for which I get only a few minutes of penumbral eclipse.  So John's comment about 70 minutes of total eclipse on the equinoxes isn't far off the mark, 5 or 6 minutes of penumbral eclipse on either side of about an hour of totality twice a year is about right.  This isn't a show stopper, considering the temporary outage always occurs at midnight.

My contribution to all this is that a geo powersat wouldn't necessarily be at zero latitude.  I can think of some good reasons to not park it there.  Set it at 1 degree inclination.  Then of course it appears to move a degree above and below the plane of the ecliptic, and it would require some station keeping and some pointing authority, but these things are light, so tilting it a degree over 12 hours using light pressure from the sun wouldn't be that hard.  Besides that, you need to actively aim the thing anyway.

spike