[ExI] Obama Transition Team Examining Space Solar Power
rpicone at gmail.com
Tue Dec 23 10:21:39 UTC 2008
On Tue, Dec 23, 2008 at 2:08 AM, Robert Picone <rpicone at gmail.com> wrote:
> On Mon, Dec 22, 2008 at 9:33 AM, Kevin H <kevin.l.holmes at gmail.com> wrote:
>> On Sun, Dec 21, 2008 at 5:53 PM, Keith Henson <hkeithhenson at gmail.com>wrote:
>>> it largely depends on the cost to lift power sat parts to GEO.
>> It's probably the most realistic near-term method, unless we're looking to
>> NASA, ESA, etc. Looking at the numbers, if we can somehow do this from a
>> lower orbit it would be much cheaper. I know a low earth orbit would have
>> some of the same disadvantages as on earth: only twelve hours of sunshine a
> I'd think it'd be much much worse than on earth, you would need several
> rectennas per satellite, driving up the costs greatly. I'd expect that
> atmospheric absorption of the microwaves would start to play a much bigger
> role when you're forced to use extreme angles as well, which would negate a
> lot of what energy savings you're getting from the height alone. Unless I'm
> missing something, a low earth orbit would be the worst of both worlds,
> intermittent power generation at a relatively low efficiency combined with
> extremely high costs.
>> Someone mentioned a sun-synchronized orbit, but I don't see how that is
>> possible. The satellite would have to orbit the earth once every year,
>> which would be way to slow and, to my knowledge, much higher than GEO. But
>> it seems that full GEO isn't necessary, we could tolerate a couple hours of
>> night every day, and the costs savings would probably add up when you're
>> doing this on a large scale.
> Remember, GEO isn't just about distance, it's about actually being able to
> synch with the ground... A couple hours may not seem like a huge deal, but
> if an object is orbitting 15 times a day like the ISS, and you only get
> efficient power generation at, say, an angle less than 30 degrees, then a
> given rectenna only is capable of receiving about 4 hours of power a day.
> These are spaced out relatively evenly throughout the day
> Lower orbits degrade much more quickly anyway,
Heh, that somehow got sent mid-typing, but I suppose the thought was pretty
much as complete as it was going to get other than clarifying that it is my
understanding that ion thrusters can be used relatively cheaply to transit
to a higher orbit when compared to the equivelant pure launch cost.
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