But with the ability to beam power anywhere in the solar system, you don't need to launch from Earth. Everything can be mined, refined, manufactured, and deployed in zero-g or micro-g.

The Earth-based outlay would not be in the form of close solar orbit panels. It would be self-replicating machinery deployed to the asteroid belt. Possibly even deployed from Earth's moon (which admittedly still traces back to initial launches from Earth). But the vast bulk of the grid would not be launched from Earth.

Also, consider that rockets themselves emit lots of CO2 as they launch. Sure, you can use a hydrogen/oxygen rocket, but then you need a source for hydrogen. And if you don't want greenhouse emissions, that means you need a huge plant cracking water into H2 and O2. In other words, you effectively need to build a huge energy storage facility. You could just attach a fuel cell to your rocket H2/O2 plant and skip the rocket launch entirely. It is possible to create green rocket launches, but the equipment needed is essentially already a massive base load solar/wind plant.

A Falcon Heavy costs $90M for up to 141,000 lbs to LEO, for a total cost of $638/lb. And the Heavy isn't fully reusable, so the main cost is the upper stage that gets thrown away. If Starship or something similar works out, the price will drop to about $30/lb. At that price, space solar starts to make sense.

I plugged that number into the cost estimates from the book The Case for Space Solar Power, which has detailed numbers based on NASA's SPS-ALPHA project, and it came out to 4 cents/kWh including everything (manufacturing, ground station, etc), which is pretty great for clean power on demand without needing storage.

Starship is fueled by methane which can be made pretty easily from water and CO2. With a clean energy source, the whole project could be carbon neutral.

If Starship can bring that cost down to 10 per lb the economics start to look feasible. Big if, but this is Futurology after all.

well it's how the Dyson Sphere tech starts, Except that humans are 5,000+ years behind the rest of the universe. We're pretty pathetic.

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You do realize that if they wanted to cause mass destruction they already have nukes.

The defense from weapons of mass destruction is the same no matter the type, it's retaliation. China could build an ion cannon on the fucking moon and the threat would not be significantly larger than a nuclear weapon, because if they used their death ray the US would retaliate with nukes.

Humans already have the technology to render our planet devoid of life. A new weapon of mass destruction is not some dramatic leap in lethality, because you can't get extra dead.

For that matter, China is already extremely reluctant to have WMD. They maintain only 100 300 nukes to dissuade other countries' nuclear aggression, even though they are much much richer than Russia and could easily afford thousands. They also have a standing policy of No First Use, which is a commitment to allowing their enemy to nuke China first, before they retaliate with subs. They do this because they never want nuclear escalation and so the USA won't see a malfunctioning launch detector and immediately assume a nuclear strike.

oh no what if china gets a weapon whatever will we do, they've never had weapons before!

Yes but almost all SPS designs are microwave. If you use laser then you get blocked by clouds. A 2GW microwave transmitter in geostationary will give a footprint of several square miles. Birds could fly through the beam without harm.

Assuming you're using a phased-array transmitter, which is the only practical method, the only way to get even that much focus is to use a reference signal from the ground target.