NSSO on Space Based Solar Power

apsmith writes "About a year ago some of the people at the US National Security Space Office began looking into space-based solar power (SBSP) as a technology in the near-term strategic interests of the United States. At first the participants were skeptical, and the "phase 0 study" went along with no official funding. In a rather innovative move, they organized the study as a series of internet-based (bulletin-board and email) discussions, with the wordpress site open to the public, and a closed experts-only discussion using Google Groups. Initially expecting only a dozen or so interested parties, the discussion grew to include over 170 people with past expertise and interest in the issues. The final report was released Wednesday morning; it provides an excellent broad-brush review of the status of SBSP, showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project. The big question is where it goes from here — NASA? DARPA? The new ARPA-E? Or something new? I was able to attend the press conference, which included Buzz Aldrin in an announcement of a new alliance to push for implementing the recommendations of the report."

Comments

cool

[spykemail]

Maybe the solar satellites can double as a baseball cap for the Earth :).

Ok, someone explain it to me

[iamlucky13]

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.

Convince me.

Re:Ok, someone explain it to me

[apsmith]

Saves on transmission and storage.

No weather, and a clear view (no atmosphere at all in the way).

That gives you a factor between 5 and 10 over on-the-ground systems to start with.

If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.

Re:Ok, someone explain it to me

[Jubedgy]

Portability and extensibility. The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA). In any case...

Portability:

By using an orbital energy collection system, you can simply re-route the beam to any place on the planet within the system's FOV...done right, you can get full 4*pi sr coverage of the Earth 24/7. Design a portable ground station, and you can provide power to a disaster area that has been removed from the rest of the power grid (paraphrased directly FTA).

Extensibility:

If, once in place and a standard orbital collection platform design has been established, more power is required, simply launch the spare unit. Proper formation flying techniques (something currently at about the cutting edge of orbital design) should allow the new unit to 'hook in' to the system to boost the amount of available power. This may be in the article, I have not finished reading it yet.

The LISA mission provides a pretty good overview of how I see the entire system distributing power from the collectors to the emitters (the things that will transmit the power down to the surface), though I may be totally off base from what the authors have in mind. The LISA mission will consist of three satellites forming an equilateral triangle with leg lengths of 5 million Km shooting lasers at each other. Last time I checked, anyway.

It is currently not economical, nor is it really achievable yet. I encourage you to at least browse through the article as it does discuss some of your questions in a more cogent manner than I have.

Re:Ok, someone explain it to me

[timmarhy]

just how do you propose to get the electricity back to earth from venus.

how do you propose we maintain them from that distance? yes, solar cells aren't this eternal source of power people think they are. expect to need to do rolling replacments every 10 years atleast, if not more under those conditions.

Re:Ok, someone explain it to me

[lgw]

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency It's better because now you have a hugely powerful microwave cannon in orbit that can fry anyone you need it to. Thinking about an orbital power station other than as a weapon is probably misguided. This is probably a feature for the "National Security Space Office".

Re:Ok, someone explain it to me

[Lloyd_Bryant]

There is no nighttime in space, nor any clouds, nor any seasons, nor any atmosphere. Solar panels in orbit deliver full power 24 hours a day 7 days a week 365 days a year with no need for fuel or maintenance. And they don't have to be, and probably shouldn't be, in orbit. Inject them into an orbit between Venus and Mercury, or closer still. Solar radiation falls off with the square of the distance. The closer we get them to the sun, the more power they will generate, by orders of magnitude. First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

And how exactly do you keep the power beam locked onto the target, when the target is on a sphere rotating once per day?

Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

And maintenance *will* be required, for the foreseeable future. Someday we may be able to build solar cells that don't need to be periodically replaced, but not today.

Furthermore, it's been noted that Earth orbit is "halfway to anywhere in the solar system" (attributed to Heinlein). So we'll need serious orbital capability to build these things, regardless of where we put them.

Re:Ok, someone explain it to me

[TripMaster Monkey]

Actually, carbon nanotubes ("buckytubes") are quite good conductors of electricity.

So that problem's solved...leaving only the original problem of manufacturing enough defect-free tubes in enough industrially-significant quantities to make the skyhook in the first place...

Re:Ok, someone explain it to me

[QuantumG]

The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA). Hmm.. the first number is correct, but we don't have 100% efficient solar panels and won't any time soon (if ever) so you've gotta down rate that.

The second number, however is totally wrong. If you're going to talk about what "the sun provides", i.e., the theoretical 100% efficiency solar panel, then you get a figure of about 1000W/m^2 on the Earth's surface. You could say it is more like 800W/m^2 when you take cloud cover into consideration.. and then there's the fact that you only get that during daylight hours, so halve it to get 400W/m^2 but that's still a lot more than 250W/m^2. It *feels* like someone is downplaying the possible efficiency of solar panels on the Earth's surface vs the same solar panel in space in order to make their argument stronger. As you took that figure straight from the article, I'll give you the benefit of the doubt, but that's what it sounds like.

It's still a heck of a lot of difference though. You're talking nearly 3.5 advantage to putting your solar panels in space over leaving them on the ground.. but there *are* losses to transmitting the power as microwaves through the atmosphere, and there is the astronomical cost of launching anything into space.

Whenever I hear people talk about solar power satellites I'm reminded of the episode of Seinfeld where they stock the mail truck with bottles to collect the 5c deposit in the adjacent state. If you can get a free ride you might be able to make solar satellites work, but you've still gotta crunch a lot of numbers first, and no-one has done that successfully.

Re:Ok, someone explain it to me

[modecx]

If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.

Actually, I'm quite sure someone has built an earth bound a set of devices capable of comparable beam energy density to a proposed orbit power system. IIRC, the efficiency of the receiving antenna can be around 90%, not sure about that of the transmitter.

Personally, I'm sure an array of heat engines could provide more power density than currently comparably priced solar panels, it's silly to pass them up.

Re:Ok, someone explain it to me

[CrimsonAvenger]

Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

No. An equatorial orbit only goes into Earth's shadow during two short periods a year, near the Equinoxes. Off the cuff, I think the sats will be able to enter Earth's shadow once daily for about three weeks every Equinox.

The rest of the time, the axial tilt of the Earth is enough to keep the sats in light 24 hours a day.

Re:Ok, someone explain it to me

[QuantumG]

Ya know, I think you should probably put down the crack pipe.

It's space, dude.

The orbit is 264,869 km around.

Re:Ok, someone explain it to me

[B3ryllium]

At least it would ward off that dreaded Global Cooling disaster we've all been hearing about.

Re:Ok, someone explain it to me

[QuantumG]

hehe, did you even look at any of the results?

Re:Ok, someone explain it to me

[AJWM]

Brilliant idea!

Thank you, but it's not original.

Let's put the receivers and transmitters right next to the gigawatt microwave antenna! That will surely fix all those problems!

Yep. Unless you're trying to watch satellite TV in the middle of a rectenna farm, of course -- although even there they'd likely have the transponders for that particular region mounted on a different satellite. It's not like everything on the powersat has to point in the same direction, you know, or operate at the same frequency.

Beyond the Orange-Bellied Parrot

[Nefarious Wheel]

It's not really a bad idea, provided there are no orange-bellied parrots in the way. The real fun is when you have to explain to greenies that yes, it's really solar power, and yes, it's also thermonuclear.

I like the idea of a separate organisation dedicated to this technology, as it's clear none of the existing organisations can do it. Set it in motion, get it done before the bloat sets in. Also like the idea of the solar-electric HEO ferry -- anyone have a link to an artist's perception of it (a real one I mean)?

Re:Beyond the Orange-Bellied Parrot

[RyanFenton]

Indeed - and because of the potential for unparalleled amounts of energy that are possible with more and more direct forms of solar energy extraction, new things become possible. Dark matter-based energy storage systems and/or weapons become closer to practical, matter fabrication factories manipulating atoms using nuclear interactions (think renewable nuclear fuels), all kinds of uses for the astounding amounts of energy we can't practically transport directly back to earth, but have flowing out at all times. New kinds of engineering and uses for high-energy physics.

That's the enormous potential lying just out there, and also something that almost justifies the apprehension that one can feel about nuclear weapons. Dark matter weapons would be to a nuclear weapon as a nuclear weapon is to fireworks. Of course, that's the same kind of problem that exists with any kind of space travel - anyone can get ahold of a big enough rock and manipulate existing forces send it towards anyone else to pose the kind of threat that would also make a joke of existing nuclear weapons.

But we can't stop threats - they come from nature just as much as they do from man. Learning how to face such danger is much more valuable than refusing to ever touch such ostensibly 'dangerous' forces. And I'd much rather have 10, then 100, then thousands of earths able to start up, rather than stagnating ourselves just to force this one earth to hold our entire future potential. Of course, that isn't the real choice we have either - in almost everyone's ideals, we should care for ourselves, care for eachother, and expand to be a peaceful force of diverse enlightenment rather than spending all our resources on war and revenge. We should care for our world, while we embrace the dangerous potential around us, so that we can grow to a point where the potential danger doesn't have to be so terrifying.

Ryan Fenton

Re:Beyond the Orange-Bellied Parrot

[jambox]

FTA: "...then beamed toward a reference signal on the Earth at intensities approximately 1/6th of noon sunlight." Seems like they're intending to beam the energy back in a coherent, but rather diffuse beam to a large rectenna, rather than a tight, high intensity laser blast as is often assumed. Does this make sense? If the beam sent down to Earth is only 1/6th of the intensity of sunlight, what's the point? If this is true though, then the bird-slaughtering potential of SBSP is a misunderstanding. It'd also reduce concerns about it being used as an Akira-style orbital laser cannon.

Because you don't need batteries...

[Goonie]

There are several advantages space solar power has:

• higher intensity sunlight than even a cloudless day, 24 hours a day
• you've always got direct sunlight, so you can use cheap mirrors to focus the light on a very expensive but efficient solar cell (you can do this on Earth as well, but it doesn't work as soon as you get clouds)
• No need for backup power. That's worth a lot of money.
• The ground based gear is much smaller and lighter than equivalently-powerful terrestrial solar panels. This is a big advantage for the military, who are the proposed initial customers.

I'm skeptical too, but it's not quite as crazy as it sounds.

Re:Because you don't need batteries...

[polar red]

higher intensity sunlight than even a cloudless day And how are you going to transmit that energy from space through clouds ?

Re:Because you don't need batteries...

[Xiaran]

The earths atmosphere is transparent to certain microwave frequencies.

The difference between... cannot go wrong

[cumin]

Douglas Adams - "Mostly Harmless"
- The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.

Lets build in some redundancy shall we? (Just in case.)

I think you covered the list pretty well but corrosion is also a factor that space should mitigate. Well, mostly aside from the wandering bit of space debris.

I haven't RTFA, probably won't, but I'd like to throw in the additional suggestion we look into Von Neumann devices to build most of the components on a lunar base. (Earth first, and strip-mine the moon later.)

Gerard K. O'Neill

[Chris Daniel]

http://en.wikipedia.org/wiki/The_High_Frontier:_Human_Colonies_in_Space http://en.wikipedia.org/wiki/Solar_power_satellite

It is a gun, a really big gigawatt class gun.

[forgotenpasswerdmoro]

A big beam, needs a big mirror. Be it microwave, infrared or visible light it's a huge gun in orbit, untouchable by IEDs and lesser nations. It doesn't even need to work that well, just 10 x amplification from nominal and any spot on earth is unlivable. Or operate as a great psychological weapon when a given region is bathed in light 24 hours a day. It is a very bad idea, like SDI was a bad idea, like the further militarization of space is a bad idea.

Won't happen until one world, united.

[tygt]

Face it, we're already concerned about relying on an unstable Middle East for our energy.

We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.

Re:Won't happen until one world, united.

[DerekLyons]

We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.

Nope.
 
These things will be high up - in GSO, which takes it right out of the range of any ICBM based launcher. Unless you can figure out how to pack propulsion, power, guidance, and a Dangerous Payload into a five to ten pounds or so... (And no, the classic 'handful of sand' or 'paint chip' or 'styrofoam cup' won't cut it here - the interception geometry is different from that with orbital debris in LEO. Not to mention these things are Very Big - and hitting the very few, and very small, critical targets in the array is going to be Very Hard.) Guidance and control are going to be major headaches.
 
A major spacefaring nation might be able to carry it off with a few years R&D - but the launches aren't going to be stealthy and whodunit is going to be very obvious.

Point source vs. directed beam.

[melstav]

First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

Actually, no.

Light intensity from the sun drops off at the square of the distance because the sun radiates as a point source in all directions.

If you put your collector array closer to the sun, you collect significantly more sunlight. Then you use that energy to power a laser. If you can keep that beam tightly focused, you won't have much loss in the beam at all.

we will indeed need serious orbital capability

[alizard]

meaning mainly, lower launch to orbit costs. Doing this not only gets us power, it gives us a platform for space industrialization.

Jimmy Carter must be laughing his ass off

[theolein]

I remember, back in 1980 or so, when all the Reagan fans were jumping for joy because the actor was more popular than a naval nuclear engineer (yes; Carter actually knew his shit), Carter had proposed a system of orbital solar power stations. It would have been more or less the same thing as they are proposing today. Those of you who have access to Time magazine's archives will find an article on it.

So, here we are today, some 27 years later, and the same proposal gets floated.

Imagine if laziness hadn't dropped the issue back then. Iran, Iraq and the whole business of 9/11 would have been less critical than they now are.

Fatal error in their assumptions?

[jambox]

FTFA:

"Conflict prevention is of particular interest to securityproviding institutions such as the U.S. Department of Defense."

Hmmmm - not on recent evidence!