Hubert et al.

Part 2

Now let's look at the requirements of your solar array. To collect one megawatt in space would require a steerable array about 1/2 the size of a football field. My little home town west of Boston runs on an average of 10 megawatts -- which would require an acre of solar arrays. Boston runs on roughly a gigawatt -- requiring a square mile. Yet Boston isn't even close to 1% of national electrical consumption. To provide just 5% of our national electrical usage from space would require 21 gigawatts -- or 21 square miles of collection area.

This is where the wanna-bees run off the rails, because 21 square miles doesn't sound like a lot. Yet it isn't just the area that causes problems (from assembly and steering complexities, solar photon pressure and tidal forces). At 5 watts per pound you would need to launch 2 million metric tons of panels up to geosynchronous altitudes. Even if you're right and my original estimate was off by a factor of 20 -- that's still 200,000 metric tons. An Atlas V is typically rated for ~ 15 metric tons to GEO -- so you're looking at 12,000 launches based on your numbers, and more like 10 times that based on reality. Even if your pounds per dollar to orbit and your mass estimates are correct, you're still looking at launch costs of $1,000 x 200,000,000 kg, or roughly 100 trillion dollars -- just to launch enough panels to make just 5% of our electricity for the next 20 years (yes, solar cells, especially in space, do wear out). If MY estimates are right, the cost is more like 10 quadrillion dollars.

This is where the wanna-bees wax poetic about reusable launch vehicles and other nearly free methods for access to space. Yet we tried that -- it was called the Space Shuttle -- and it was very far from free and just barely reusable.

Okay so let's ignore all of those realities. Even still, you're not out of the woods yet. You still need to design and build huge clean-room facilities to fabricate the panels -- and as part of this, buy the exotic rare-earth elements to grow the solar cells (or make a bunch of Chinese companies rich by outsources all of this). But before anyone gets rich or saves any portion of the planet you still need to find some way to pay for this long before any power is beamed from space. And the money isn't just for technology. You'll also need to lease the land for your microwave collectors -- who pays the rent? If you somehow launch the system -- who fixes it when it breaks? Sorry, spacecraft at geostationary-altitudes are inaccessible unless you're planning on a human flight component to the plan. And before you go any further, those geo slots are auctioned to the highest bidder. Have you looked into those costs? -- typically they're auctioned at tens of millions per slot. Are there even any slots left for sale? The last I heard most over the USA are locked up.

Okay, so let's just skip the geo orbits -- yet any other orbit would require continuous steering of the microwave downlink antenna -- aiming this continuously at a fixed point on the planet -- with mayhem the price of missing the mark by any sort of wide margin. The problems of attitude control of spacecraft grow exponentially with size. If you lose your downlink lock, several megawatts of microwave energy could drift across a schoolyard playground, and suddenly your goal of saving the Earth heads exactly in the opposite direction. Satellites go rouge and become zombies at times. And you'd better hire the best security team on the planet -- because this would be the most awesomne terorist weapon ever conceived.

Beyond this, we haven't even scratched the earth-based operational and business side of the story. Who buys your electricity? If you can't sell it in bulk for way less than ~ 10 cents per kw hr, you'll never bring in a single dime of revenue. And even if you managed to charge $1,000/kw/hr -- the system would still never pay for itself.

Solar power from space for mass consumption on the earth does not need anyone to "damn" the idea since, as far as I can tell, those with potential funding dollars already understand how far removed this notion is from practicality -- now and for as many years into the future the futurists dare to predict.

Hubert et al.

Part 1

As Gerry points out -- there are terrific working alternatives to generate usable power at reasonable costs now and immediately ahead that do not require fantasy or magic. I wish to be kind about this however, since my goal in life is to illuminate, not to condemn. Sometimes this goes over the top when I see just how far astray from plausible reality a vaporous notion is carrying decent and well-meaning people.

Here's just a snapshot of things to consider....

"The best hope the world has for a prosperous future" begins with a sober assessment of physical and economic reality. Your "20X is too high" works out to 50 pounds for a 4KW system. That is inconceivable for a space-rated assembly. Okay, maybe I'm a bit high in my estimate -- yet I like my spacecraft to survive 10 g's and 165 db of sound pressure during launch. Typical commercial panels are 5 watts per pound. For just the panels we're looking at 800 pounds for a 4KW system. With framework, deployment motors and power conversion, we're easily over 1,000 pounds. You can try to work around this with expensive and exotic mass-saving designs, but it won't come close to solving any problems on the scales you're talking about.

Considering launch mass per dollar -- the economics are rooted in physics. If someone could have cracked this nut, it would have been cracked 50 years ago. Due to limits on energy from chemical fuels, only 1% of total launch mass can make it into orbit as a working payload. You can throw money at this to kick that percentage up a tiny bit -- but you won't save any money by doing that. On a cost-basis, that takes you in the wrong direction. Instead, everybody talks about cheaper launch costs. Yet every single estimate and promise underestimates or outright ignores the real costs. SpaceX (or any other launch vehicle company) can quote whatever they want -- but it doesn't reflect the $billions invested up front.

After launching Shuttles at $1b per pop, it should be obvious by now that the economies of launch vehicle systems have nothing to do with the survival of NASA. What matters most is favorable public opinion that translates into congressional support, plus designs that keep jobs in the districts of those who support NASA the most.

Not to be heard as anything more than a re-framing of the facts -- NASA is little more than a governmental public relations firm that occasionally launches robots and people into space to keep our attention. Sending people into space makes no economic sense -- therefore all arguments surrounding the economies of human space flight and the related costs of hardware are irrelevant. NASA can't cede deep space exploration vehicles to the private sector because it would end their best public reason for existence.

Bad ideas never die, they just fade away until the skeptics move on to critiquing other bad ideas. Then these ideas work their way back, eventually pitched to a new generation. Part of the problem with critiquing this or any other monumentally infeasible notion is how the critique itself -- no matter how damaging -- lends an air of respectability to the idea from the undue attention it receives.

Keeping in mind that I have no intention to lend this notion credibility (other than perhaps to offer further evidence of our human capacity for fallacious thinking) ... I will state the obvious example:

Roof-mounted photovoltaic panels now cost ~ $1 per watt. These are typicality middle of the road performers since most houses have plenty of roof surface. Of course there is the added cost of the mounting hardware, power interfaces and installation. In the end, the cost is more like ~ $5 per watt. Bottom line: a typical house making ~ 4KW might cost ~ $20,000 to install, or ~ $1,000 per year spread over 20 years.

4KW of panels that are gussied up for space-rated flight and engineered for automated deployment would weight perhaps a metric ton. At even at an insanely low launch cost of $4,000 per kilogram, just lofting our 4KW system into space would cost $4m.

But wait! There's more.

That 4KW system will need to beam power back to the Earth and this will need to be collected by acres of wire mesh then processed and pumped into the grid. Insurance will be hugely expensive since our orbiting system at least to the minds of the liability experts) is nothing other than a long-range microwave oven minus the protective metal case. To build a power service for just 1,000 houses the price tag for the launch alone balloons to $4b (1,000 metric tones would require dozens of Atlas V launches). Assuming that the installation cost is actually paid by the users of this electricity (the only honest method of cost analysis), the amortized price per family just to launch their portion of the system would be $200,000 per year for 20 years. More realistically, given the upfront R&D, regulatory issues, launch survival and space environment hardening, marketing and institutional overhead -- just to turn a profit you would need to charge each family at least $1,000,000 per year for electricity I could make on my roof for ~$1,000 / year.

Yet much like global warming naysayers who are unwilling to assess the evidence, the myth of space-based power will be around for as long as there is bandwidth on the internet to repeat baseless claims of this that or some other reason where somehow by ill-defined magic unwrites the laws of economics.

My summer after college I worked with a crusty old carpenter who lived by the principle of "Do what'chu CAN with watcha GOT!"

Wasn't that the essence of Apollo 8? (besides worrying that the Soviets were about the steal that same thunder). The LM wasn't ready, but the Saturn V was good to go -- and among so many other rewards, we were stunned when we saw our first Earthrise. Indeed Apollo 8 was a practical step to a landing on the moon, and yet like all ventures into the unknown this also awoke some of us to our place in the Universe.

We just need to find the imagination to do something practical with what we got -- and if truly something new (and not gimmick), in the process we'll discover something magnificent that wasn't hyped ahead of time by the PR wonks. Most people won't care. But that is nothing new and those who do care need to accept this fact.

It's far more practical to place a comm relay satellite at L2 and operate lunar back-side rovers from the ground. A one-second round-trip delay between astronauts sitting in a halo orbit at L2 versus an earth-based three or four second delay isn't worth the MASSIVE overhead of a crewed flight. What's so special about a lunar orbit rendezvous anyway? The fuel from the moon to reach L2 is more than the fuel straight back to Earth. Why not direct sample return? Astronauts can be very valuable investigators in situ, but running robotics from L2 is a -poor- use of their skills and of already scarce funding resources.

Since August, 1969 firing the imagination of the public has been a wasted effort. Instead, pick a worthwhile mission. Do it in the most sensible way. Publicize to those who care. Forget about inspiring the public. Just make sure that each member of congress gets a piece of the pork -- because THAT is how these things are really funded -- not with reasonableness of argument or pie in the sky.

actually DOD (missed that) - sorry -- but the essence of the comments is the same.

Not really. One is civilian with all technology free to US corporations and individuals. The other, by definition, needs to be far more secretive. Further, it would not be a merger -- the DOD being 50x larger. Also, this still would not bring all US space agencies together, nor all the work done by commercial outfits. Lastly, beyond a certain scale, merging giant bureaucracies with poorly aligned missions (science versus surveillance, for example) does not result in savings. If anything, it adds another layer of bureaucracy.

I'm all for international cooperation, and aspects of the story here along those lines are encouraging. I just wish those with notions of beaming solar power from space would work through a serious cost estimate versus producing the same amount of solar power on Earth.

At most, a tripling of efficiency versus a desert venue could not possibly justify a space-based infrastructure easily costing 1000x more per watt.

Even though I understand how this might not be a popular conclusion -- powering cities from space as a commercial venture is nothing more than science fiction with no feasible economic model whatsoever.

Looking back over this sub-thread, it would be wise to point out how I am actually pro-space-tourism, and here I'm simply trying to counterbalance notions of this being an easy nut to crack. Few reading this online journal need the attached lecture -- since most of you already know the true hurdles of anything space-related. So please accept my comments accordingly.