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Space Ring Could Combat Global Warming
telstar writes "Though the debate continues around global warming, a new proposal suggests building an artificial space ring around the Earth to block the light of the sun and bring a balance to solar radiation, cloud cover, and heat-trapping greenhouse gases. The ring could be comprised of particles which would scatter the sunlight, or be built by an interconnected ring of spaceships aligned to block the light. The former proposal is estimated to cost anywhere from $6 trillion to $200 trillion dollars, while the spaceship solution would run approximately $500 billion. Halo fans rejoice."
Since the beginning of time man has yearned to destroy the sun...
In this world of fantasy (which we do not live in) it would be nice...however I'd much rather my tax dollars going towards more enviromental regulations and research than some high tech sci-fi wonder.
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How could this go wrong?
This would not work. Other planets would become jeleous and greedy, all of them wanting to get The Ring from us. There would be wars, many would die, and entire civilizations would die. What we need to do is get a neutral planet, one without such greed, who can take the ring, and hurl it into Jupiter. Then, the universe will be free.
Why not put a disk direct between us and the sun at a stable gravity point?
We know how well solar eclipses work... why not just a permanent 'dimming'?
Telcos have alot of dark fibre in the States. Most people assume that's optical fibre...but it's actually moral fibre.
Wouldn't it be cheaper, easier, and more effective to, I don't know, build energy systems that don't release carbon? Just a thought.
What kind of a hair brained scheme is this??? What happens when global warming ends because we haven't any more money for cars having spent it all on this ring?
Of the 6 trillion, why not spend the$ 3 trillion on environmentally safe energy (fusion plants, geothermal, solar panels in the deserts) and spend $3 trillion to buy off all the oil megacorporations.
Besides, moving the earth further away from the Sun is a much more hair brained idea, so why not do that?
You can buy a lot of solar cells for $6 trillion dollars.
Additionally, the ring could have solar panels on the outside and thus power the whole Earth cleanly...unless there is too little silicon on Earth to build that many solar panels...yes I know there is a lot, but that's a lot of solar panel...
And in related news, Al Gore has ridden the mighty moon worm.
They can't be serious. Who could fund this? Isn't World GDP only around $40-50T?
Tristan Yates
Or we could just cut down on pollution for FREE!
Honestly, how much would it cost to require an SUV to get 30+ MPG instead of 15?
I thought we could combat global warming with giant ice cubes mined from Haley's comet.
According to wikipedia global dimming might have actually masked the effects of global warming. Too bad we got reversed the effects of global dimming. The two forms of pollution were canceling each other out. http://en.wikipedia.org/wiki/Global_dimming
Ooo man the floppy drive is broken. No wait. The computer is just upside down.
That might even take the pressure off the environment, as you could probably shut down most of the world's coal-fired power stations.
Why would anyone engrave "Elbereth"?
For decades we've been told by the environmentalists, "if there's even the tiniest chance that global warming is real and man made, then it would be foolish to do nothing about it." This is Pascal's Wager, but applied to a different religion. But two can play at this game!
"If there's even the tiniest chance that global warming is NOT happening, then this would be an extremely foolish thing to implement, as it could trigger the next ice age..."
c.f. Niven's "Fallen Angels"
Don't blame me, I didn't vote for either of them!
They want their article back.
The entire world becomes depressed, due to the absence on natural light, kills themselves or simply stop having sex. Doesn't apply to humans only, most higher forms of animal life ceases to exist.
Of course, linux users are as chipper as ever due to the fact that they never seen natural light to begin with so they aren't as affected.
(As someone with seasonal affective disorder, I see this as a death sentence)
Get your Unix fortune now!
I think you meant to write "finding a way to eliminate dependence on foreign oil."
In other words, let's start using the energy we get from the sun to meet our current needs.
It's unbelievable that someone would suggest that we should restrict future energy delivery from the sun just so that we can keep on consuming energy stores from the past (oil) and pollute our sky with the smoke. Pure laziness. It's like a teenager cleaning his room by hauling his dirty laundry out of the house and burying it, wasting all the effort he ought to be using to just clean the clothes. Not that I've ever done this.
For some reason, I'm getting an image of a charred barren hillside a few miles from the collector. A bunch of people are running around on fire. Oh, wait, that's a SimCity 2k screenshot. Nevermind.
And we will get the raw materials for these ventures...how exactly?
For that kind of dough, wouldn't it be easier just to move the Earth to a higher orbit (further from Sol)?
$200 trillion (2.0 x 10e14 dollars), or even $1 trillion, is a big chunk of change to go spending on something we don't even know would fix the problem. What if it's not enough? How much money do you dump down the hole (or in this case, throw into the air) before you start thinking about alternate solutions?
How much seawater could you pump into the central Sahara for $1 trillion? Make a giant salt marsh the size of say, Texas. Still plenty of desert left over, don't worry. But how much cooler would that make the globe? Don't even use 4-degree Celsius water from the Atlantic, but get 20C water from the Red Sea. It'll fill back up.
Or, maybe we could just accept the changes in climate as the natural order of things (even if they're our fault - we're natural, too). If the oceans rise, move to higher ground.
Raise your children as if you were teaching them to raise your grandchildren, because you are.
Then we'd still be getting the heat. The whole point is to reduce the flux absorbed and trapped by the earth.
Can you be Even More Awesome?!
Supposing you take the cheapest option, the $500 Billion Spaceships idea, over the course of 20 years -- that's $25 Billion per annum. Very doable.
There's a bigger problem, though. How do you convice 6 billion to put up with constant illumination of the night sky? Not to mention, the Astrologer's Union would be rioting in the streets.
Because it's easier to convince people to let you put a bajillion microsatellites into orbit than it is to convince them to let you build another nuclear power plant.
If you're willing to blow 6 trillion on this, you should certainly be willing to blow 10% of that on reducing greenhouse emissions, weaning the world off of oil onto "greener" energy sources, etc, etc.. What the hell ever happened to practicality?
But that heat would be taken out of the chunk we produce when we consume energy from other sources, so it is still a net gain on the inward flux. Reducing emissions by closing coal plants would increase the outward flux. This also reduces the energy expended on getting at our current sources of energy, so less heat is produced by us. We win on all fronts.
Personally, I'd like to have the huge space-bound solar collector with microwave transmitter, but in a place where it doesn't reduce the sunlight on earth. If we clean up our act with emissions we should have plenty of breathing room and not have to block out the sun just yet. And sunlight is useful for so many things.
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For those who don't remember, the sport-utility robots (Bender included) get on a single island and blow fuel from their exhausts (read: asses) to propel the Earth away from the sun.
That episode freakin' ruled.
So, does anyone even bother to think about where those 'fossil fuels' originally came from? Oh, oh, I know! It's the remains of vast swamp lands! So the fossil fuels are old concentrations of plant matter that's been fossilized & turned into hydrocarbons of various lengths and types. So all that stuff we mine up was once on the surface as living plants that took water and CO2 and sunlight to make the sugars that were the basis of our hydrocarbon fuels. So when we burn it, we are releasing matter that was already on the surface and in the environment. Thus, as long as we have some sort of reserves of fossile fuels left, there will be fewer greenhouse gasses (CO2, CO) in the atmosphere than before all those durn swamps photosythecised it into solid material. I make no argument against global warming per se, just against the assumption that "we caused it" and that we "we need to stop or the world will end." FUD, FUD, FUD. Life existed very well before the concentrations of materials lead to the fossile fuel deposits, and it will continue just damn fine even if we end up buring it all back out into the atmosphere that it came from anyway. Take a moment to step back a few levels from the general aruments of human-caused global warming and give it some real critical thinking of what is going on. Climates cycle, and that's a fact. Live with it, deal with it. You're going to have to 'cause we aren't going to do anything to stop it, nor should we. JDP
Now, let's orbit these solar cells at 500 km altitude, i.e. a diameter of 13,756.3 km or circumference of 43,217 km. The article doesn't say how wide the ring should be, but to block 1.6% of the sunlight to a circle 12,756.3 km in diameter would require a strip about 160 km wide. That's 6.9 million square kilometers of solar cells in the full ring.
Now the silicon wafer in a solar cell is really quite thin, typically around 300 microns thick, so that's only 2.074 cubic kilometers of silicon all up. Density is 2330 kg/m3, so that's 4,833 megatonnes of silicon required, or about 0.0000005% of the earth's resources. I think we have enough.
Of course, the energy required to manufacture that sort of area of solar cells would be pretty high, but think of the returns. The earth receives about 1370 W/m2 in orbit, so multiply that by the area of cells facing the sun (2.04 million square km), and you get about 2.8 billion MW of incident radiation :-) Let's say these cells aren't particularly efficient, maybe 10%, plus transmission losses of another 70%, and you still have 84 million MW of usable energy, all day, every day.
Now, in 1997 we used 380 quadrillion BTUs, globally, or about 111 quadrillion watt-hours. That's an average consumption of 12 million MW, comfortably within our budget for some time. An energy-producing system with a capacity of 7 times the entire global requirements is worth quite a bit.
There's only one downside to this - if we divert all this energy down to earth & use it, it all ends up as heat in the end, which completely nullifies the original purpose of the ring (if you remember) of preventing global warming! D'oh!
Why would anyone engrave "Elbereth"?
Well as they don't know 100% what is causing global warming, if it is actually happening and if it's not normal. The warming could be a cycle. At any rate, I could just see them over compensate and then "Opps...."
I just don't think they really know what is really happening, there are a lot of inner dependencies and not all are fully known or understood yet.
- Justin
Fusion plants didn't melt down, that was the Nuclear plants. The Fusion plants were stable.
Of course, we all know the tornadoes were the best.
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Why is it that when you believe something it's an opinion, but when I believe something it's a manifesto?
This is exactly why you'll never make a good super villian. You think too small.
Or we could, ya know, spend 1% of that and colonize Mars, fund pollution free energy sources, control human over population, and, ya know.. STOP SCREWING UP THE EARTH. Yeah, let's build impossibly-large space structures with money that *could* go to solving the root causes (our bad ecological practices) instead of just behaving ourselves and taking care of the Earth, that's MUCH easier. What utter stupidity.
ERROR 144 - REBOOT ?
Massive chemical cleanup from production, massive ramping up of existing infrastructure, massive use of land to meet required energy levels.
You can never go home again... but I guess you can shop there.
Come on! No one is going to make a Highlander solar shield comment!?!?!
Now that's a death ray!
Though the debate continues around global warming...
What an excellent opening sentence. The problem is, which debate is he referring to? Is he talking some real scientific debate? Or maybe a politically motivated debate based on non-science in which the powers that be try to confuse the public into believing there is no scientific consensus, with the goal being to maintain the status quo and avoid angering the energy lobby.
Because, scientifically, there is no real debate anymore over whether or not man is impacting the climate and causing global warming.
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Because it's easier to convince people to let you put a bajillion microsatellites into orbit than it is to convince them to stop burning gas in their SUVs.
lets spend billions of dollars to put a ring around the earth. tons of fuel would have to be burned to do this. they could just throw some glitter into orbit. heres a better idea. have everyone on the planet plant at least one tree. trees would help cool the earth. because they hold more water. trees also help water evaporate so there will be more rain. more rain = cooler weather.
Any such solar radiation blocking device would most likely be in the equatorial plane - right above the equatorial rainforests.
The rainforests getting less radiation means diminished CO2 absorbing capacity of the whole planet. If not done carefully, this could lead to dangerous levels of CO2 in atmosphere.
Indian.
How the hell do you actually estimate that something will cost 6 trillion dollars? Trying to get an estimate for something that can run upwards of a million dollars would be extremely hard.
I mean, sure, if you're off by a couple million then it's not a big deal in the scheme of things but has there ever been a more "pulled out of our ass" estimate ever?
Sounds like saying "We don't know but it'll be lots!"
Then where will all the good posts come from?
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Now I know anything to do with space and the words "global warming" tend to induce a frontal lobotomy in many Sladot readers, but there are people actually taking this seriously??? Come on, there's gotta be something left in that cavernous skull to realize this has got to be one massive joke. I mean, somebody seriously misplaced the foot icon here.
Look at it this way... You've got $6 trillion to $500 trillion dollars burning a hole in your "save the earth" pocket. Dontcha think that maybe, just maybe you could put that money to better use by throwing it at something that doesn't require lobbing multiton roman candles into orbit? I mean $500 trillion . You honestly can't think of an industry or two here on the ground you could revolutionize overnight, let alone in the time it'd take to assemble THIS project?
Speaking of that, what sort of time frame are we talking? Any mention of such is amazingly absent. And we haven't EVEN gotten into the fact that the scientific community is still deeply divided on the exact cause of global warrming. Everything from man's impact to the natural warming and cooling cycles of the earth come into play. Hell, there are even published scientifc reports that say the Sun is hotter than previously measured. We still don't have a conclusive clue and these people want to throw a reflective tarp over a portion of the earth. What is the damn environmental impact of THAT? What happens to the plant and animal life UNDER it? Not as much heat or sun, that's for sure. Draw your own conclusions.
I'm sorry, but this is a prime example of what happens when people who think they're smart smoke crack. They find implausible and extrodinairy ways to waste our money.
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If that's really a problem, then use a large number of smaller objects in orbit around L1. (SOHO does this already, so you can't tell me its impossible.)
;~)).
;~)
:~). Not trying to be some cynical asshat shooting down what you say, although I do admit I probably come across that way in text mode. Technology like this *is* fun to consider :~)
:~)
Actually, I was a student of one of the primary engineers of the SOHO orbit. She discussed it in class, and showed us the orbits and the fuel estimates etc. I assure you that we DO NOT have the ability to model a large number of objects around L1. We certainly could create this capability, but you are talking worse-than-realtime calculation times in our current state of technology (for many-multiple objects that aren't allowed to collide). The problem is already 'intractable' in the sense that it is multi-body dynamics -- no solution, must model via iteration.
The SOHO craft's orbit looks like a seriously drunk dolphin chasing a drunk fish. Just looking at it made me fear going for a masters in orbital mechanics (which I didn't end up doing...hmmm
Thanks for the distances, had forgotten them. I really should do the math on the visual arc of the sun and compare to some random object at distance 'x', but I am really really lazy
I agree: it could be done. Iff we needed it. I just think that a better idea, in terms of preserving the human race, would be to get some people the hell off of Earth! Eggs in one basket and all of that.
The '100 years' thing I tossed out was related to your statement re: space-elevator: in 100 or so years, doing this will be stupid cheap/easy compared to trying it today. Not actually cheap, nor easy: just in comparison to today
If we were to cover 1/2 the land area we've paved in the US with solar panels of standard efficiency, we'd generate as much electricity as we consume in all forms of energy in the US. The rest of the world is quite parsimonious by comparison, though they could so too meet all their needs and live as profligately as we do without environmental impact.
It has been suggested by people not bothering to do the math that the change in albedo from the solar cells themselves would cause warming, but we've already paved twice that area.
Biofuels are relatively inefficient compared to solar cells, but fairly simple as well and carbon net-neutral. Biofuels and solar hydrogen could meet our mobile and nightime needs easily.
We can live as we do, with all the juice and cars and whatnot, so long as we do not too grossly expand our population, in a closed loop, steady state system. We could live quite comfortably if we overturned the Ford coup of the 1920s and reversed the graft-based decision to build roads and the 1950's military decision to build suburbs. With a predominantly urban population moving by train (or working close to home/at home) we could buy the solar cells with a few year's oil expenditures.
Unfortunately Solar doesn't have the profit margin of oil, so there's no political/industrial interest. There's $10 trillion worth of oil in Iraq we took ownership of for a mere $1 trillion in military expenditures (at the current burn rate, given the time it will take to pump it out). The usual profit sharing (if we chose to share with the Defeated People) is 50/50, meaning at least 5:1 profit on that adventure for the country as a whole, but since Haliburton is actually getting paid for their efforts (and then some) and the profit will accrue directly to the oil companies and not back to We the People, it's an amazingly shrewd business deal, the greatest heist in the history of mankind: $10 trillion. Almost the entire US gross domestic product for a year.
Nobody building solar factories is going to see that kind of profit, and without it they can't compete in the congressional auction. Laws aren't bought flat rate, they're sold to the highest bidder and no industry can outbid the oil industry.
It would be far cheaper to convert the global energy economy to solar (as a combination of solar-thermal, solar-electric, and solar-biofuel with the only other long-term viable power source as a backup--breeder nuclear, which (not ignoring the very real waste problem) is the only other energy source we have that can meaningfully contribute to our long term power needs) than to build a great space ring. The low range costs are small compared to the current value of the known oil reserves (roughly $80 trillion, proven plus mid-range USGS unproven estimates at $40/bbl).
It's technically easy to solve, but politically impossible.
Uh-oh, I'll bet it's not...
have everyone on the planet plant at least one tree.
This could be going in the right direction...
trees would help cool the earth.
Yes, okay, and now for the science...
because they hold more water.
... Okay, not what I was expecting, but let's go with it...
trees also help water evaporate so there will be more rain.
But, I thought we were storing water, not helping it evaporate? There must be some logical reasoning behind this...
more rain = cooler weather.
Oh. Dear. God.
"I assumed blithely that there were no elves out there in the darkness"
Around the year 1000 for example, it was much warmer than today. There's a reason why "Greenland" is called that: it had thawed and the Vikings could colonize and farm it.
Then it cooled off some time later, and the colony was all but abandoned.
The fun part is, the humans didn't go extinct, the gulf stream didn't reverse, ocean fauna didn't all float belly-up because of melting glaciers being sweet water, etc.
Basically that's what gets me pissed off about this _political_ "waah, we're all DOOMED if you don't follow ME" hype about global warming. It's mis-representation and scare tactics.
As was said, it's only the bullshit media and political speeches where global warming is a certainty, and certain doom is just around the corner. The media loves a good scare story. That's what sells. Actual scientific facts don't.
The science part is a lot more ambiguous and not fully understood yet. It's not just that the earth has cooled off just fine before. It's also that:
- The "Global Warming" measured, that started the whole hype, was actually based on limited data from only a tiny portion of the world. And it was only a 1 degree Celsius over a _century_ increase.
- The Earth has periodic warming and cooling cycles, ranging roughly between 6 degrees Celsius cooler than today in the last glaciations, and some 6 degrees warmer in the times of the dinosaurs. Think roughly a sine wave spanning whole ages. With a lot of noise superimposed.
And we're roughly in the middle. It's _normal_ to rise slowly on the average. Not this fast, but basically a century of it might well be measuring just the noise in the real signal. Especially given that:
- Actual satellite data that covers a helluva lot more of the whole globe (you know, the "global" part of "global warming") actually shows a global _cooling_ for the last 20 years straight. There is actually a theory that we might be heading into a "mini ice age". (Not that it will stop journalists and politicians from presenting a _cooling_ as an effect of global _warming_.)
- Also for this last interval, there is data indicating that the average temperature on Earth just faithfully follows fluctuations in the Sun's energy output. Think, for example, how we got a very warm winter between 2003 and 2004, because of solar flares. We can actually observe and measure those things nowadays, and blimey, temperature on Earth seems to just follow them.
Is it that unbelievable, since Sun is where that heat comes from in the first place? We're talking some 0.3% temperature difference in this "global warming." It only takes _minor_ fluctuations in the energy input to produce that.
- Humans never accounted for more than 2% of greenhouse gasses. If not only we stopped driving cars, but if humanity as a whole even stopped breathing, it still just wouldn't make that much of a difference.
A polar bear is a cartesian bear after a coordinate transform.
Suppose that you get a big country like the US to invest something like US$5B into this project.
.1 millionths of the sun's radiation. You need about a million tons to shield 1% of the sun's radiation, requiring only 25 thousand space shuttle flights.....
Fine. Now you are blocking the sun on bunch of other countries that A) didn't pay for it B) don't want you to block their sun.
This thing would be way TOO big not to block unwanted countries.
If my math is correct, For each 8 tons of gold (or similar material that you can make very thin) you can create a ring of 1m wide, 10nm thick around the earth. (I did the math for "just above sealevel", or about where the spaceshuttle flies).
This 8 ton ring would block
You have on the one hand a peer reviewed, falsifiable, reproducible study that says one thing by a bunch of folks (perhaps in lab coats) who studied and workd 8-10 years of their lives to get to the point where they could be 'peer' reviewed.
On the other hand you have something called a study with none of the above features (except the authors often have a TLA in something, though maybe not anything to do with atmospherics or even physics).
But the press thrives on conflict, so it reports both studies as being by 'noted scientists' or maybe one was a fictional tale by some guy who wrote alot of SCIENCE (fiction).
Most folks have no idea what 'falsifiable', 'peer review', or 'reproducible' have to do with anything important like the price of gas, so they believe the press when it tells them that the different 'studies' represent two sides of the issue (fair and balanced).
And with enough money on both sides to support new 'studies' the debate could well go on until every last icecube in Greenland turns into liquid oxygen dihydride.
Then the big controversy will be whether to build giant seawalls around the coastal cities or to run screaming for higher ground.
And you can bet the press will present that story with two nicely balanced sides, as well.
Even if the climate change is natural, we may have the power to keep our planet at the temperature we want it at.
After all, don't you like tropical islands? A working gulf stream?
What if we could alter the amount of solar radiation received and tailor it to our needs to make more of the planet inhabitable and comfortable.
More than that with a ship ring, we could get all the annoying people to crew the ring (or at least serve prison sentences on it).
While the science may not know exactly why the earth warms and cools over thousands of years.
It is to do with changes in orbits circularity and axis tilt.
The fact is that is does, and the last time I checked there were no cars around thousands of years ago during the last warming cycle.
The problem is not change, it is fast change. Current warming is occuring on a timescale of decades, not millenia.
As recently proven (look it up yourself), every time a volcano goes off it produces more green house gasses than mankind has ever created since the industrial revolution.
I have. This is nonsense.
From "Volcanoes and Society" published the University of Michigan:
"Carbon dioxide is one of the main causes of the Greenhouse effect, but there are not significant amounts for the carbon dioxide emitted from volcanic eruptions to contribute to the Greenhouse effect. Humanity is responsible for emitting 110 billion tons of carbon dioxide each year, while volcanoes only contribute 10 billion tons".
So sure, we know green house gasses warm the planet and that pollution is bad on a local level, but if you think the small amount of damage mankind has done to the planet is going to raise global temperatures even by 2 degrees every hundred years, then your ego is about the size of most of the politicians baking the idea.
Pollution is bad globally. The CO2 concentration in the atmosphere has risen more more than 30% in the past couple of centuries, and that is due to us, not volcanoes. This increase is getting much faster. Your '2 degrees every hundred years' could well be an underestimate.
C'mon Dad, how many times do I need to ask you to stay off the internet when you're drunk?
I think, therefore I am. I think?
This is one of the things that frustrates me about "climate change"--all evidence is unritically adopted to support the theory. The change in terminology, from "global warming" to "climate change" is itself a shift designed to support exactly this sort of pseudo-scientific scullduggery.
"He who would learn astronomy, and other recondite arts, let him go elsewhere. " -- John Calvin, commenting on Genesis 1
I think you need to familiarize yourself with Viking history and Greenland a bit more, probably through Collapse: How Societies Choose to Fail or Succeed by Jared Diamond.
Greenland has a lot of lushness on the shoreline, but has always had harsh ice areas inland, with pockets that could almost be compared to an oasis in desert. Vikings farming and herding, mostly by clear cutting, let the very light soil be carried off by the wind as it originally would (volcanic activity outputs very light and nutrient rich particles). Overgrowth trapped that soil... clearing it for farming allowed it to be swept away...
Not going into excesive detail, because there are other factors, but it wasn't Climate Change that solely ended Viking societies in Greenland.
"The more pity, that fools may not speak wisely what wise men do foolishly" - Touchstone,Shakespeare's "As You Like It"
For some reason, I'm getting an image of a charred barren hillside a few miles from the collector.
That was examined in considerable detail a few decades ago, with an eye to preventing exactly that scenario (along with things like microwave-cooked birds falling out of the sky ready to eat). A fine solution was found:
First: Pick a frequency that, unlike the band used in microwave ovens, is NOT readily absorbed by the water composing most obstructions or potentially damagable natural structures (clouds, birds, cows, plants) or by other materials found in lifeforms. (There are some fine bands for this in the milimeter wavelengths.)
Second: Put up a "rectenna" site (antennas with microwave semiconductors - "Crystal sets of Inconcevable Power" to quote a pardoy of Doc Smith). This covers tens or hundreds of acres, and catches essentially all of the energy while letting most of the sunlight through. (You can graze cattle under it if it's not at Fort Stinkin' Desert - and even there it won't bother the lifeforms beneath it once the constructin is done.) Even if the beam were pure heat it would only be a large-single-digit multiple of the amount of sunlight shining on the area on a clear day, and it's nearly all caught by the rectenna.
Third: Transmit a "pilot carrier" from an antenna in the middle of the array to synchronize the transmitters spread out across the broad structure of your solar collectors (or across a number of them).
The result is a "synthetic aperture" antenna of large size, tightly focussing the return power on the receiving rectenna site. If the pilot signal is lost the beam immediately defocusses - within milliseconds - as the syncronization is lost, with most of the energy missing the entire planet and the rest being orders of magnitude weaker than a distant radar site. (Ditto for the energy from an individual transmitter that loses sync - it stops being combined with the rest of the beam and turns into a much smaller microwave beacon.)
From synchronous orbit the earth is a small fraction of the visible sky, and any target on it is not visible to the naked eye. If the energy from the beam were all visible light and defocussed you'd have a hard time spotting it in daylight.
You could do the same pilot beam hack with laser light. But why bother? Lasers are less efficient, more more would be absorbed by the atmosphere, and less converted to useful power at the output. Even with the tech available in the '70s you could get 85% or better from DC in at the satellites to power to the grid on Earth.
Construction costs would be comparable to those of an earthbound plant. Then fuel is free for the life of the plant and there's no waste to dump (except the plant itself if you ever decommission it, or any burned-out parts).
Semiconductors on the ground. Vacuum transmitting tubes in orbit. (Vacuum tubes are EASY in orbit, and very efficient. B-) )
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way