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Comment by eloff | Hacker News Reader

I didn’t read the article, but you could also write one about why you should never say never or why pessimists tend to be wrong in the long arc of history.

My dad is fond of talking about how his Astronomy professor said we’ll never be able to detect planets outside our solar system, and proceeded to prove it through optics calculations. That didn’t age well.

We’ll get to fusion too. It might take a ridiculously long time to be economically competitive, or it might not. But it will happen.

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Fusion is happening right now for free. Our whole planet is in the chamber we call the solar system and receives 1370 watts per square meter. About 173,000 terawatts received continuously. I often wonder if we need a fusion chamber on earth and if it is possible for it to exist as an energy generating device without it being a sun or a bomb.

the earth receives the tiniest fraction of the sun's output. Space-based solar panels would have an almost unlimited amount of energy at their disposal...but how to get ithat energy down the well without James Bonds-ish laser beams?

Space based solar is dumb. Let’s be generous and say you can get 2x output by having 24/7 sunlight, and that somehow we can beam it down efficiently enough that it’s a wash with gains from not having clouds or atmosphere in the way. Then the cost must be less than 2x for it to make sense over ground based solar. That’s just not realistic.

Now when we have mining and manufacturing in space, and can use the energy there, that’s a different story.

A panel in geostationary gets five times as much energy as a panel on the ground. It's like noontime sun around the clock, plus none of the light is blocked in the atmosphere. And the biggest advantage isn't that 5X, it's eliminating the need for overcapacity and storage.

https://illumin.usc.edu/space-based-solar-power-a-new-path-t...

But isn't it infinitely cheaper and more efficient to just cover the earth with 5x as many panels?

Losses in transmission from space would be significant (I'm seeing 9.6% microwave efficiency) and never mind that it costs $1000/kg to put something in space.

https://en.wikipedia.org/wiki/Space-based_solar_power

Definitely wouldn't be feasible unless Starship works out at scale. If it does, launch costs go under $50/kg.

Here is NASA's SPS-ALPHA study, which estimates 15 cents/kWh with $500/kg launch cost and minimal technological development (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_20...

That's just not going to happen. You could put 5x panels on the ground plus batteries and still have budget left over compared to launching it into orbit.

That depends on launch costs and satellite design.

The old designs from the 1970s would have been absurdly expensive. Modern designs like NASA's SPS-ALPHA are cheap to manufacture at scale. The book The Case for Space Solar Power has a detailed cost breakdown and puts a 2GW geostationary plant at 15 cents/kWh, but was published before SpaceX did much. I plugged in Starship launch costs and it came to 4 cents/kWh, which is pretty great for 24/7 clean power without storage.

Here is NASA's study (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_20...

But why are lasers a bad option?

I guess because they can be used as weapons, if the said lasers can transfer enough energy with enough accuracy to cover real energy needs.

Also because they get blocked by clouds. If you're not getting 24/7 power, you might as well put your solar panels on the ground.

Microwave power transmission seems like the obvious answer, but is fundamentally flawed due to the thinned-array curse:

> It states that a transmitting antenna which is synthesized from a coherent phased array of smaller antenna apertures that are spaced apart will have a smaller minimum beam spot size, but the amount of power that is beamed into this main lobe is reduced by an exactly proportional amount, so that the total power density in the beam is constant.

https://en.wikipedia.org/wiki/Thinned-array_curse

People promoting space-based solar invariably pick Rube Goldberg complex designs that will reliably fail.

A big, very low-mass reflector concentrating sunlight on laser tubes tuned for various wavelengths found in sunlight, and beaming visible light at only solar intensity onto wavelength-matched solar PV farms on the ground, at night, would substitute for storage. Since the light intensity is no more than in sunshine, there is no danger.

Of course it's possible, we've already established that much. The question is can it be economically competitive with solar and wind plus storage? I think that could take a while depending on how many resources we dedicate to it.

You should probably at least have read the first few paragraphs of the article, then. The article is about the economic competitiveness of it. (It notes that just because MythBusters built a lead balloon once, that doesn't mean there will ever be any commercial lead balloon flights.)

I think that's the question with fusion right? I think we've already answered that we can do it in the affirmative. I think that will happen too eventually. It's a question of technology, engineering, manufacturing, and scale. That takes time and investment. Anyone who says it can't be done is being a fool. You don't know what you don't know. Betting against innovation with an open timeline is not a smart bet.

There are opposing pessimists in the energy sector (e.g. renewables/nuclear), so it is very likely that at least some of the pessimists will be proven right.

That seems like a non sequitur. You want to explain what you were thinking here?

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