Caltech to launch space solar power technology demo into orbit
caltech.edu
caltech.edu
Is this a really dumb idea? Any of you with a more relevant background could tell me where this could be so wrong?
That's not high enough to put you above bad weather (airliners fly higher, and they divert around storms.) Bad weather is bad news for airships and historically destroyed about as many as hydrogen fires. You'd need to bring your airships down into hangers when the weather got bad.
Also, wouldn't the graphene aerogel be filled with air and be heavier than air? Aerogel doesn't just float away. Unless you mean for these to be vacuum airships, but those seem very far fetched.
If so, I want one.
Wow what a fascinating idea! Just thinking out loud here, but the compressive force is proprtional to area, while the boyancy is proportional to volume. So I wonder if making it big enough would allow using some fairly standard materials. What about a cube made of 6 big (huge) sheets of some strong yet light material supported by a sort of skeleton inside?
Or maybe we can use electro-static repulsion to keep it from imploding? Like how a normal balloon compresses the air inside because the rubber tries to shrink but if you had a balloon that tried to expand instead, because of say electric repulsion, or maybe something else, then it would put the air inside at lower than atmospheric pressure.
[1] https://en.wikipedia.org/wiki/Buckling
But regarding your point that the columns would have to scale with volume you might be right about that. I was thinking that it should scale with the total force, but the bigger your structure the longer distance the force has to be transmitted. So yeah I think I got that one wrong.
Only a handful of countries use meters for measuring altitude, and as far as I'm aware they are feeling the pressure to reform to using feet for sake of consistency (read: safety).
Besides, denoting both meters and feet like I did will guarantee everyone will understand one way or another.
The idea is to have something that is tethered to the ground and held aloft by the winds at high altitude and that has wind turbines to generate power, which is sent back to the ground by cable.
There are pretty much always strong winds over much of the US at 5k-6k meters, so such a wind power generator would provide 24 hour a day power most of the time.
Here's a site showing the wind over the at around the height [1]. Click where it says "earth" in the lower left to change the height. The height is given in pressure. My link is for 500 hPa pressure which is somewhere around 5500 m. The 700 hPa option would be around 3000 m, and the 250 hPa option would be around 9000 m. Here's a site with a graph of pressure vs height if you want to know the heights for the other pressure options [2]. That graph uses kPa. 0.1 kPa = 1 hPa.
The proposals I've seen I've proposed a few different things to fly. One is basically just a kite carrying turbines. Another is a parasail. Another is some sort of rotor aircraft similar to a quad drone. I believe I've also seen some that use fixed wing aircraft with propellors.
The ones with the rotors or propellers would have electric motors powered from the ground that can be used to get the thing up to operating altitude, and then they switch the motors from taking electricity to drive the rotors/props to letting the wind drive the rotors/props to generate electricity.
[1] https://earth.nullschool.net/#current/wind/isobaric/500hPa/o...
[2] https://www.engineeringtoolbox.com/air-altitude-pressure-d_4...
One of my favorite engineering projects and documentaries, just because of the sheer ambition and scale, and the grit of the team to keep pushing through repeated failures. Sad the project was cancelled but it makes sense given the cost and complexity.
I’ll point out that a space-based solar array with a microwave power downlink was on the front cover of IEEE Spectrum around 1971. The article ran the numbers and pointed out the technical challenges.
So, this idea is not new, but it hasn’t gained enough support over the last fifty years to get a project off the ground.
The other big change is the prospect of $50/kg to LEO with Starship. Falcon Heavy's advertised price is already down to $600/kg.
I wonder where Asimov got his idea for the technology. Did he just make it up? Or was inspired by existing technology of the 1940s.
I am firmly of the belief that solar power is humanity's future of energy production.
Yes, beaming power to Earth is viable and could be economical. This pretty much solves the problem in variable power generation. I've seen estimates that a space-based power collector could generate about 6-8x what that same collector could on Earth (due to atmosphere, weather and day/night) so even with some power loss from beaming power to Earth, it's viable.
But there's an even better fguture for this.
The first is as the power source for space habitats. You literally just put them on the outside hull. These are incredibly efficient in creating living area per unit mass and ultimately would become a Dyson Swarm. I consider this inevitable.
The second is you can do better than beaming power with orbital rings [2]. In short, you put a loop of conducting cables in orbit, run a current through them and float things on top with the magnetic field. The beauty of this is those things elevated on the ring are fixed to points on Earth. This means you don't need to speed up to Mach 30 to reach orbital speeds.
If you have an orbital ring, you can run cables down from space directly to the ground.
This was with microwaves from a phased array transmitter and a reference signal from the ground target, and the satellite in geostationary.
So, although it may be too expensive for Earth power, it can be very practical for moon power.
There's a famous-in-the-area ex-NASA blogger with good (not perfect) articles on the topic, but I can't Google and find him 'cause authoritative institutions now seems to trump and drown out mere experts on Google.
Others here cite him: https://caseyhandmer.wordpress.com/2019/08/17/blog-series-co...
Maybe better: nuke the moon and reduce a few key crater rims, then use much shorter towers. Could be that a series of regular bombs might be more effective and less likely to "alarm the horses (general public.)"
Dust.
There is near a Moon base, which is presumably where you’d need power.
> it's economically reasonable to loop the moon with a 600Ω conductor
Could you generate nontrivial power from the Moon's motion through the Earth's magnetic field?
Not sure, but my gut feeling says no: the Moon is a very long way from the Earth relative to the Earth's size, therefore the magnetic field is likely to be fairly uniform around the Moon and so that can't extract much work.
That said, one fun idea I've had is to just assume that the Dark Energy expansion of the universe is pushing the Moon away very slowly; 73 (km/s)/Mpc * distance to the moon ≈ 9.5e-10 m/s, which is pretty close to the actual current Moon-Earth recession speed.
Plugging that into the formula for far-field gravitational potential energy given the mass of Earth and the Moon, that's about 170 GW at the present time.
(But don't go trying to crowd-fund a Dark Energy field reactor on my say-so: At my [rather limited] level of understanding, it looks like physicists haven't yet reached any sort of consensus as to whether or not Dark Energy might work like that).
What would the cable layer look like? A huge robotic rover? Could you get all 10,000 km onto one spool, or deliver new spools to it?
It's a Starship-scale project: something like 100 launches, which is only feasible because Starship is targeting such low launch costs.
I don't know (see previous disclaimer) but I wouldn't be surprised if (assuming circumlunar power is even the chosen solution) this is done by sending up an aluminium factory instead and processing regolith.
1. A moon day is 28 earth days, thus 14 days of darkness
2. Ice are in permanently shaded areas near the poles of the moon, it might be easier to setup satellites to beam down power rather than setting up in 2 locations
For Luna it doesn't make as much sense as it would for say Mars, since there's no atmosphere to reduce efficiency and no shortage of ground real estate. You can save a bit of propellant to not bring the panel assembly down, but you'll need fuel for orbital stationkeeping instead anyway.
But I don't think powering a satellite from the ground makes much sense; you'd need ground stations around the world.
Radar was the only thing that came to my mind, too. (Didn't know about the project, though. Thanks!)
Problem is earth observation, as a market, sucks. With low-latency optical imaging en route, I'm not sure what premium radar would command.
> don't think powering a satellite from the ground makes much sense
Microwave power transmission through atmosphere is terrible, and we're nowhere close with laser. The idea would be large arrays in a high orbit beaming to lower-orbit birds. That's the only proximate case where space-based solar power makes sense: space to space. The only place where having the panels where you need power doesn't make sense is in the atmosphere. I just can't think of anything you'd want to do there that requires that much power.
One advantage of radar is that sometimes you can see through things that aren't transparent to visible light. I don't know if it's true, but I've heard that modern SAR sats can see through petroleum storage tanks and some warehouse roofs, so they can collect data which may be valuable to traders. These modern sort of radar satellites are apparently fine with solar power, but maybe they'd be even better with more power.
Something like 2/3 of all spaceX starship launches for the Artemis program will just be sending oxygen up to orbit.
http://www.niac.usra.edu/files/studies/final_report/1107Jack...
Not sure what the yields are, but the paper suggests that a capture array would be about 5 tons. Might be worth a try when Starship matures.
Antimatter is pretty valuable. I think SpaceX should look into this, antimatter harvesting could be lucrative.
The only reasonable option is to beam highly energetic beam back to Earth. Do we want us to be browned by l/masers from the orbit?
This is how we should do it. But we can’t. Fortunately, the sat-to-sat laser folks are working on that kit. In the meantime, these proposals tend to focus on microwaves.
In any case, to the degree this one day has an economic case around Earth, it’s in powering low-orbit satellites. Not punching through the atmosphere. That said, I don’t have any obvious near-term high-power use cases for a LEO constellation.
Ah, it will be masers then ... and so together with masks we will wear saucepans ...
We do not need additional energy to be delivered to the Earth from outside, we are warming it already.
Instead we need to harvest energy that is heating up Earth surface already.
Waste heat isn't our problem.
> we need to harvest energy that is heating up Earth surface already
If we're being artistic that's what an in-orbit solar panel, which at least part of the time blocks photons from reaching the Earth, does.
I try to imagine it like a fog: all kinds of radiation makes it through to the ground but then the heat from that radiation cannot simply radiate into space, because the sky is all dense fog and scatters in the infrared. We're effectively making a more diffuse lamp out of Earth.
Of course, if your solar array projected area as seen from the sun is approaching the Earth's own projected area, then you're overdoing it again.
It does. (Ozone and water absorb microwaves. This is how your microwave oven works.)
https://www.gi.alaska.edu/news/using-microwaves-see-through-...
What frequency spectrum is that? And for bonus points: can this project fry commercial planes?
What would the minimum power loss be for thick cloud/hurricane? Dunno.
This also seems to be the last nail in the coffin for terrestrial radio astronomy, now that you mention it.
Not kilowatts.
Nope. The transparent bands are in the visible spectrum and far infrared(8-14um). Microwaves are mostly uniformly absorbed by water molecules:
The atmosphere is almost transparent to long-wavelength microwave [1]. The tradeoff is in power density.
[1] https://earthobservatory.nasa.gov/features/RemoteSensing/rem...
That's an urban legend. If it was true, they'd be great rather than "meh" at melting ice, and (I appreciate most don't do this anyway) we wouldn't be able use domestic ovens for glass-working or melting alumina to make synthetic sapphires and rubies.
• https://youtu.be/XojnG2IFfTo
If a material is dense enough (metal being the prime example) it'll block. I've nowhere argued that you could send microwave power through solid walls - whether brick or sapphire economically.
> SSPP got its start in 2011 after philanthropist Donald Bren, chairman of Irvine Company and a lifetime member of the Caltech Board of Trustees, learned about the potential for space-based solar energy manufacturing in an article in the magazine Popular Science. Intrigued by the potential for space solar power, Bren approached Caltech's then-president Jean-Lou Chameau to discuss the creation of a space-based solar power research project. In 2013, Bren and his wife, Brigitte Bren, a Caltech trustee, agreed to make the donation to fund the project. The first of the donations to Caltech (which will eventually exceed $100 million in support for the project and endowed professorships) was made that year through the Donald Bren Foundation, and the research began.
"Ok nobody tell him it's a bad idea and we get like 50 PhDs and 5 professors!"
- A satellite will have to transmit power through the entire atmosphere from space, which will have substantial losses even in perfect conditions
- A satellite constellation in orbit would need many ground stations to transmit power to from space
- Weather will get in the way of transmission to the ground, just like it does with ordinary solar
- The cost of getting a PV array into orbit is very expensive relative to the amount of power it can generate and transmit
Balancing this is at least a half an order of magnitude difference in collection efficiency.
> Weather will get in the way of transmission to the ground, just like it does with ordinary solar
True. But there are extraterrestrial atmospheres where water vapor and ozone aren’t a problem. (I’ve only seen this proposed with microwave.)
> cost of getting a PV array into orbit is very expensive relative to the amount of power it can generate and transmit
This is the killer. That said, this is a long-term research endeavour. If we contemplate such an array around the Moon or on Mars, or in a world with in-space resource extraction and manufacturing, the economics shift.
The economics of anything on Mars or the Moon amounts to 'try to convince a government to throw tons of money at you.' A technology which only makes sense in that economic context is very limited.
If this were a start-up I’d be roundly criticising it. It’s not. It’s a research project. And each of its sub-projects—testing new PVs in space, a novel deployment mechanism, power transmission—has clear value outside a space-based solar context.
As a focussing mechanism, SBSP is neat because each problem needing to be solved to make it economically viable is immediately valuable on the ground. (Save for power transmission. That’s still niche.)
Isn't that the entire point? Putting solar panels in space has been done regularly the 1950s.
Might be ill-advised for a whole mass of reasons that I, as a software engineer, know naught of; but it would be a use case.
Musk will find a way. Another stepping stone to Mars.
But for Earth, even if it was free to put the PV in Earth orbit, the ground stations need to have an incredibly low total cost to make sense.
I can't remember how low exactly.
Also, cheapest ground-based PV in the world is 1.04¢/kWh (Saudi Arabia), and the cheapest in the USA is 1.50¢/kWh (New Mexico), so 0.7¢/kWh is already a large percentage.
https://commercialsolarguy.com/lowest-solar-power-prices-in-...
At ideal locations, ground solar is super cheap, but the microwave receiver works anywhere. Not needing storage is a big difference, too.
(I really should get around to blogging what I think is wrong with this whole approach to space solar, where it works despite that, and how to improve on it for Earth usage; it comes up here every so often, and linking to my blog is easier than disjointed comments without images).
In response to his famous question "what's the conversion rate," the answer is about 50%, according to the book The Case for Space Solar Power. That's not bad considering a panel in geostationary collects five times as much energy in 24 hours as a panel on Earth.
Completely off-topic, but would "half an order of magnitude" be sqrt(10)? I've just never heard someone refer to a factor of ~3 as "half an order of magnitude".
Last time I looked, the estimates ranged from 270% to 50x. Seeing the latter, my brain went into astronomer mode and then I guess just ran with it.
Advertised price on Falcon Heavy is already just $600/kg to LEO. A big part of that is the throwaway upper stage, which Starship eliminates.
I'm sure Starship will be better, but 40 times cheaper? I doubt it.
https://www.spacex.com/media/Capabilities&Services.pdf
The biggest cost is throwing away hardware. If you're not doing that, you can amortize your entire hardware cost over the number of launches. At Falcon's launch cadence that's still going to be significant. But Starship is designed to do hundreds of launches per year, and if they manage it then hardware cost per launch is almost nothing. Then you're mainly paying for fuel and ground services, which are about a million dollars each. 100 tonnes to LEO for $2M gives just $20/kg, leaving plenty of margin for SpaceX at $50.
It might seem hard to envision putting that much cargo into space every year, but if we did solar power satellites at scale, that's exactly what we'd need.
No, $97M is for a launch with reused boosters. 63,800 kg to LEO is when the boosters are dispended.
The payload is definitely for expended boosters (check the footnotes). I agree it's not very clear about the price. Wikipedia could be out of date I guess and they're not giving a discount for booster reuse? But then why would anyone ask for reuse?
Because solar back on earth makes a lot of sense, whereas solar back in space to beam down on earth make no sense.
https://www.nrel.gov/news/features/2020/renewables-rescue-st...
These concerns are not really brought up by the media.
It's like how virtual keyboards on smartphones are not as good as a full physical keyboard (arguably) but nobody really talks about it anymore because the disadvantages of physical keyboards are so overwhelming that it doesn't matter.
The problems of solar as a scalable renewable are very fair to talk about, considering that Africa and India NEED energy to grow their societies. The only solutions that scale are oil or nuclear. The idea you can just hand wave any concerns about renewables doesn't seem very rationale if you genuinely care about the problem.
https://www.greentechmedia.com/articles/read/germanys-stress... https://fee.org/articles/solar-panels-produce-tons-of-toxic-... https://www.science.org/doi/10.1126/sciadv.abj6734
You cannot simply ignore and hand wave off "inconvenient facts" because you have a strong dislike for "climate deniers".
Where are you replying from?
https://en.m.wikipedia.org/wiki/Old_College,_University_of_E...
Street view from the courtyard: https://maps.app.goo.gl/f2o6V8JFpPtMW5R47
It's an incredible and beautiful 200+ year old building that's been continually used for teaching since it was built. On the one end of time, it's construction was halted because the Napoleonic wars cost too much. On the other, I had lectures about machine learning in it.
The rest of the university is more modern, but that place always felt like the soul of the Uni to me.
[Edit] https://www.fcc.gov/document/fcc-adopts-new-5-year-rule-deor...