You forgot to explain why this is "pretty obviously a terrible idea".
- 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?