[ExI] More ranting on power sats

[david]

On Mon, 13 Aug 2012 10:50:48 -0400
John Clark <johnkclark at gmail.com> wrote:

> 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?  Did you forget that the plane of the ecliptic is
> > tilted 23 degrees from the orbit plane of the earth’s orbit about
> > the sun?  Of course for a few days in March and a few days in
> > September, your comment is partly right, if you don’t consider the
> > penumbra all the way out there.
> >
> 
> 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,
> assuming the gigantic receiving antenna was aimed at the satellite
> that was highest in the sky so it went through the least amount of
> atmosphere. This blackout is not such a big deal for communication
> satellites because they can run on chemical batteries for a hour or
> so, but the problem is not as easy to solve for power satellites, and
> even so battery aging is the main thing that limits the lifetime of
> communication satellites.
> 
>   John K Clark


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

-David.