Lunar Solar Satellites at L1

>
> > >From what I've been able to gather, on Earth the rectenna farm
for a
> >
> > SPS would be about 10 kilometers in diameter, more if it is
situated
> > at a higher latitude.
> >
> > My assumption is that it must be this size because we want to
limit
> > the microwave power density, and thus are optimizing rectenna
size
> > to power density. If we had a "Death Ray" beam dense with
microwave
> > we could do with a smaller rectenna. Is this correct? Of course,
I
> > understand why we don't want a powerful beam.
> >
> Partially true. Another point is that having a low
concentration
> beam allows the use of a relatively small transmitting antenna.
> Getting a tighter beam involes launching a bigger antenna.
>
> > If my assumption is correct in that beam strength can be
multiplied,
> > then would it be possible to have multiple Lunar Solar Satellites
> > supporting the mining and launching operations on the moon, and
have
> > ALL of the LSS beaming down to one rectenna farm on the moon.
> >
> I am sorry, I do not follow this at all.
>
> Why have multiple lunar satellites ? One not just one big one ?

As I've discovered, launching mass via a mass driver is a very
energy intenisve endeavor. If you're interested in the actual
numbers I've been able to derive, I've been posting most of my
calculations over in the space settlers group.

I'm just pursuing an intellectual exercise, trying to see what is
involved in getting an infrastructure in place. My curiousity
started with the mamoth task of an Island 3, but now that I'm
further into it, I'm working at a bootstrapping scenario.

To answer your question, I'm inclined to favor the position of
having multiple 5 GW SPS in lunar L1 orbit, because when, or if, the
lunar operations need less power, those SPS could, with some effort,
be transferred to GSO.

Also, I'm assuming that a 5 GW SPS would be "on-line" sooner than a
10 GW, etc. It gets the power to the lunar operation that much
sooner.

>
> > Anybody have any indormation on the limits of power density that
a
> > rectenna farm can absorb, or do you really need a 10 km diamter
farm
> > PER 5 GW satellite?
> >
> No hard data. Note that as the power density increases, the
waste heat
> per unit area will increase, so the rectenna will run at higher
> temperatures. Heat rejection on the Moon is a difficult problem,
and
> this would make it more difficult.
> If the rectenna gets too hot the conversion elements will burn out.

Good points. I wonder what the limits are? Doing some simple math, a
10 KM diamter rectenna field, absorbing 5 GW would average at 63.63
watts/meter ^2. How much more could be absorbed? 5x 10x?

I wonder how much heat absorption the panels would take on the moon
before we could kill two birds with one stone. Circulate a fluid to
pick up the waste heat from the rectenna's and make use of that heat
for additional energy.