"Concerned citizens" only hope for SPS......by Dr. Gerard K. O'Neill

In article ,
Sjouke Burry wrote:

Just how are we going to transport that energy SAFELY to earth?

Radio waves.

You realy want to be mircowaved(as in a magnetron)
by a space based power transdsmittor?

I'm bathed in radio waves this very moment. So are you, I bet. But of
course I *wouldn't* be bathed in the radio waves coming from an SPS,
because those would be a focussed beam (unlike the radiation from a
radio station, wireless hub, or cell phone tower), and I'd have no
reason to go wandering into the rectenna area. Indeed, hardly anyone
would be there apart from the cows grazing under the grillwork.

Even here on
earth, if you walk in front of a military high power
radar by accidence, people have been blinded or worse.

Not relevant to SPS, but I'd still like to see a reference to that.

I would not be surprised, that at the right frequency
you can set fire to a city within seconds.

I would, given that the energy density in an SPS power beam is about
half that of sunlight at noon. But even if there were such a magic
frequency that can ignite concrete and steel with such low power, do you
suppose that this is the frequency that would be chosen for a power beam?

Of course if you want a defence shield in space, maybe
this is the way to go....
You wont have trouble hitting somebody(and his neighbours).

Yes, if you want your enemies to receive free, abundant power with
hardware that's hardly any more complex than a metal grating, this would
certainly be the thing to use. (For the sarcasm-impaired, that was a
sarcastic remark meant to highlight the irony of proposing the use of a
harmless -- actually, beneficial -- power beam as a weapon.)

If this level of thinking occurs among decision-makers, it's no wonder
so much more money has been poured into fusion than into SPS.

"Rand Simberg" wrote in message
...
On 21 Oct 2006 17:21:12 -0700, in a place far, far away,
" made the phosphor on my monitor
glow in such a way as to indicate that:

Just how are we going to transport that energy SAFELY to earth?

microwaves pointed at earth concern me.

Yes, all manner of things concern scientific illiterates and morons
like you.


Why do you feel you must constantly knock other people down?
Is it to build yourself up?

Hint; it's not working.

On Mon, 23 Oct 2006 21:42:33 -0400, in a place far, far away,
"jonathan" made the phosphor on my monitor glow in
such a way as to indicate that:

"Rand Simberg" wrote in message
...
On 21 Oct 2006 17:21:12 -0700, in a place far, far away,
" made the phosphor on my monitor
glow in such a way as to indicate that:

Just how are we going to transport that energy SAFELY to earth?

microwaves pointed at earth concern me.

Yes, all manner of things concern scientific illiterates and morons
like you.


Why do you feel you must constantly knock other people down?

Why do you molest small children?

Is it to build yourself up?

No.

Hint; it's not working.

Hint; strawmen don't work either.

Joe Strout wrote:

:Yes, if you want your enemies to receive free, abundant power with
:hardware that's hardly any more complex than a metal grating, this would
:certainly be the thing to use. (For the sarcasm-impaired, that was a
:sarcastic remark meant to highlight the irony of proposing the use of a
:harmless -- actually, beneficial -- power beam as a weapon.)

And what's to stop you from simply refocusing the beam?

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

In article ,
Fred J. McCall wrote:

Joe Strout wrote:

:Yes, if you want your enemies to receive free, abundant power with
:hardware that's hardly any more complex than a metal grating, this would
:certainly be the thing to use. (For the sarcasm-impaired, that was a
:sarcastic remark meant to highlight the irony of proposing the use of a
:harmless -- actually, beneficial -- power beam as a weapon.)

And what's to stop you from simply refocusing the beam?

To do what? Deliver the energy to a different customer? Basically
nothing, though at high inclinations they'd have to put a little more
effort into the rectenna.

But if you mean, to focus it to a tighter spot so as to make it even
remotely useful as a weapon, then the answer is: the laws of physics.
The minimum spot size is a function of the distance and the size of the
transmitter. It'll already be as small as it can be (why would you
build your transmitter bigger than needed?), and at that spot size, the
power density is about half that of sunlight.

Joe Strout wrote:
In article ,
Fred J. McCall wrote:

Joe Strout wrote:

:Yes, if you want your enemies to receive free, abundant power with
:hardware that's hardly any more complex than a metal grating, this would
:certainly be the thing to use. (For the sarcasm-impaired, that was a
:sarcastic remark meant to highlight the irony of proposing the use of a
:harmless -- actually, beneficial -- power beam as a weapon.)

And what's to stop you from simply refocusing the beam?

To do what? Deliver the energy to a different customer? Basically
nothing, though at high inclinations they'd have to put a little more
effort into the rectenna.

But if you mean, to focus it to a tighter spot so as to make it even
remotely useful as a weapon, then the answer is: the laws of physics.
The minimum spot size is a function of the distance and the size of the
transmitter. It'll already be as small as it can be (why would you
build your transmitter bigger than needed?), and at that spot size, the
power density is about half that of sunlight.


OK , I am missing something here.

If the power beam from space is safe because quote: at that spot size,
the
power density is about half that of sunlight.unquote.


so you want to spend billions having a space based system that delivers
about half the amount of power that a terrestrial solar panel would
provide. ?

doesnt seem worthwhile somehow.

wrote:

so you want to spend billions having a space based system that delivers
about half the amount of power that a terrestrial solar panel would
provide. ?

doesnt seem worthwhile somehow.

Microwaves can be converted to electricity much more easily than
can sunlight, at higher efficiency, and by cheaper convertors.
The beam also shines on the ground receiver 24 hours a day at
full intensity.

Paul

In article . com,
wrote:
If the power beam from space is safe because quote: at that spot size,
the power density is about half that of sunlight.unquote.
so you want to spend billions having a space based system that delivers
about half the amount of power that a terrestrial solar panel would
provide. ?

Not quite. For one thing, with cheap solar arrays you're lucky to get 15%
of the light out as electricity, whereas the microwave conversion is 90%+
efficient (and the hardware should be a good deal cheaper, per square
meter, than even cheap solar cells).

For another, what happens when the Sun goes down, or it's cloudy? The
microwave beam is there *all the time*. (That advantage is even bigger
than it looks, because large-scale energy *storage* is difficult and very
expensive -- the payoff for needing *no* storage is much bigger than for
merely reducing the size of the storage.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

wrote:


so you want to spend billions having a space based system that delivers
about half the amount of power that a terrestrial solar panel would
provide. ?

doesnt seem worthwhile somehow.


It's the efficiency of the energy conversion of the microwaves versus
the solar array; it's far higher, plus cloudy days don't affect it.
They've already done quite a few experiments in transmitting electrical
energy via microwaves and the technology does work; I'm still concerned
about unexpected effects on the Earth's atmosphere from the beam passing
through it (birds, etc.) but if it wasn't for the monumental cost of
building this system, it might be a very workable concept, and better
than most forms of large scale power generation other than
hydroelectric or geothermal from an ecological viewpoint, even with some
microwave effects.
At the moment the only other technology liable to be employed in this
regard is nuclear fission, and that generates nuclear waste that is
difficult to deal with unless one starts toward breeder reactors in a
big way to decrease the amount of waste through plutonium fueled reactors.
There is this interesting idea also: http://www.enviromission.com.au/
If you ever were to build an actual arcology building/city, this would
be the thing to run up its core.
The suction at the base would give it a constant source of clean air, so
no smog, and the heat of human habitation going up the stack (air
conditioner exhaust, etc.) would generate even more power in its
turbines via the chimney effect than the greenhouse effect would alone.
Plus, the covered area spreading out from its base could be used for
growing of food and recreation.

Pat

Henry Spencer wrote:

Not quite. For one thing, with cheap solar arrays you're lucky to get 15%
of the light out as electricity, whereas the microwave conversion is 90%+
efficient (and the hardware should be a good deal cheaper, per square
meter, than even cheap solar cells).

For another, what happens when the Sun goes down, or it's cloudy? The
microwave beam is there *all the time*. (That advantage is even bigger
than it looks, because large-scale energy *storage* is difficult and very
expensive -- the payoff for needing *no* storage is much bigger than for
merely reducing the size of the storage.)

Better yet, rectennas aren't opaque like solar panels. They can be
deployed in a large open mesh that allows enough sunlight through to
allow agriculture underneath the rectenna. So one gets multiple land
use, too.

--
Dave Michelson