Space based solar might not take a form where we just put mirrors in space to boost the output of existing terrestrial solar cells. The benefit is that the receivers on the ground can receive energy directly from the sun when the sun is up, and the space mirrors can be used to provide light to areas that are completely dark in winter.

I don’t think microwave beaming is ever viable

Most fusion concepts are thermal power plants. Those have inherent downsides that have nothing to do with the nuclear energy providing the heat for the steam turbines. So they will never fully replace renewables. Helion’s concept might work. But that remains to be seen.

Space based solar (lens or microwave) is a non starter for one simple reason - it would be an ideal supervillain weapon to anyone who could steer it.

Keeping A bombs out of the hands of supervillains is much much more trickier, yet we managed to do that for the last 70 years.

The station couldn't be used as a threat. And its use would be very limited in time.

Taking out the rogue orbital power station would be a competition between very trigger happy militaries. Who wouldn't want to demonstrate their satellite killers on a legitimate target?

Anything which could transmit meaningful power to the ground is going to have no issue destroying anything approaching it from below.

And why wouldn’t one of those powers be the ones installing such an installation in the first place?

Stuff in space is very vulnerable due to the high cost of shielding. How would an energy weapon in space fare against its hardened counterparts on the ground? How would it defend against clouds of shrapnel?

First you have to get the shrapnel off the ground, and into orbit.

A non trivial problem if whatever is on the ground trying to launch is being heated white hot by a maser, no?

And getting there has non trivial flight time too, plenty of time for it to be melted on its way.

Orbit is the ‘high ground’.

High ground is beneficial because you have direct line of fire where the enemy hasn't. But there is no ground to hide behind in orbit.

So what about this orbiting duck of yours, the power station recently turned rogue?

Look, the satellites you share an orbit with are adjusting their trajectories to intercept yours. Undisturbed, they will pose collision hazards within the next days. You must fry them all before they complete the adjustments. Do you have a real time feed of their position for targeting? Bet you do, you're a supervillain after all.

But some satellites are passing behind earth, they will complete their manouvers before they emerge from earth's shadow. The first hit is predicted in just 130 hours.

But hey a bunch of missiles took off on the other side of earth, they are now on a ballistic trajectory that intercepts your station's orbit. Thanks to your flawless targeting, you manage to melt some of them. Their debris will hit anyway, your station has 19 minutes left before impact.

Meanwhile, some subs poke laser scopes out of the sea, taking shots at your station. You divert your energy from the incoming missiles, but when you try to hit one, the scope is submerged again. You produce a plume of steam.

And what is this? What was supposedly a radar array starts to beam microwaves your way. Your station overheats in seconds because it has almost no mass and lots of surface. You could've taken out maybe one of the hundreds of antennas in the array if your comms hadn't already been crippled by a laser.

As you lift your gaze from the now useless controls, the sky is lit by a tactical nuke that was hiding in a spy satellite. It happened to be close enough for a crippling EMP blow.

Fin.

You realize most aimable power systems can also aim sideways, right?

And any significant orbital power station is going to have to be pretty big. Or it’s pretty pointless.

Which means it’s going to have a lot of mass.

Funny you mention it, the (reinforced?) solar panels will be an obstacle when aiming at other satellites.

Sure

What would those downsides be?

Once we start making these predictions with no single one of such project even planned, then people start predicting about all sort of bat shit crazy ideas "within the next 100 years" and there is no philosophical razor we can employ to discern them from the legit ones.

I've read "in 100 years" about many technologies that we'd supposedly have in our current era.

It's an often used qualifier to dodge what can turn out to be meritless predictions. Just long enough into the future to sound promising, but also far enough into the future to not tempt a need for supporting evidence.

In my view if we don't have the underpinnings or motivation today to support such forward looking statements, then there is no genuine foundation for claiming that the situation will improve merely as time moves on. Technology only comes about when we make it, and only develops rapidly when there is a significant motivation for putting serious manpower behind it.

One could just as easily say that we'll have small and portable fusion reactors that completely satisfy our energy needs.

Why? When will it be cheaper to deploy in space than in some remote area somewhere?

I'm pretty sure someone will figure out how to make a working solar sail that captures energy and beams it to earth via microwaves.

Please enough of them far away from Earth and you get pretty much unlimited energy all year round.

You get the same if you place solar panels in places around the equator, without all the messiness of orbital repairs and GW death rays. I can't see this being cheaper than just some panels on the ground.

The funny thing about solar panels is that they are the most efficient at very low temperatures. They'd be more efficient at the poles or high up in the mountains where they can be kept cool.

A solar panel in space would be highly efficient.

The death ray might be the feature that sells the whole thing.

I like the way you think.

Why would you want to do orbital repairs? For the amount of effort required, you'd just send up a replacement.

And we're saying that deploying new solar sails (with integrated power transmitters) to orbit is cheaper than replacing a solar panel on earth?

Not at the moment, but at some point it might be. Real estate on earth has lots of competing uses, so it has a lot of opportunity costs.

Eventually, the limiting factor will be how to get rid of the waste heat.

Even if you can turn 100% of the energy you received from space into electricity, in the end it'll all turn to heat.

Ok, so we get a really big heat pump that sends all the heat to space.

If only thermodynamics was this easy. Heat pumps ain't magic, alas, they are still subject to physical limitations, including the laws of thermodynamics.

Also keep in mind that cooling the hot part of your space heat pump is very limited: there's no convection nor conduction in space. You can only lose heat energy via radiation or ablation (= shooting away hot pieces).

Waste heat from microwave energy? Am I missing something?

I'm talking about waste heat from when you use the electricity.

Almost no matter what machine you are powering, be it a a toaster or a computer or an electric car or a washing machine, eventually turns all of the electric energy into heat.

(You can contrive some counter-examples. Eg if you point a sufficiently strong laser pointer at the sky, some of the energy will escape earth before turning into heat here.)

Inventing the Dyson Sphere one step at a time

> Why? When will it be cheaper to deploy in space than in some remote area somewhere?

When land becomes the limiting factor on earth.

Land will never become the limiting factor on earth, at least not for solar power.

Assuming the worst-case predictions of climate change come true, there will be more than enough desert capacity along the equatorial areas to provide power for the rest.

> Land will never become the limiting factor on earth, at least not for solar power.

What makes you think so? There's always more you can do with more energy. 'Never' is a long time. And there are opportunity costs from other uses you could put land on earth to.

You are right that it will be a while before remote corners on earth become more expensive than space for solar power generation. But not 'never'.

(Btw, if you think really big, the limit for how much power we can use on earth is given by how much waste heat we can radiate into space.

At some point, you don't want to keep beaming down energy from space into earth, even if you somehow could convert 100% of the received power into electricity with no losses: because at the end all the electrical power used will still turn into heat. Heat that we will have to get rid of.

At that point in time, you might want to use the electricity directly in space, eg to run data centres there, and just beam the results of the computations down.)

> Assuming the worst-case predictions of climate change come true, there will be more than enough desert capacity along the equatorial areas to provide power for the rest.

While climate change might become unpleasant, I have no clue what it has to do with any of this? The surface of the earth will stay roughly constant and so will its orbit, and the sun will shine regardless of what happens on earth. (And I assume that if you wanted to badly enough, you could easily float solar panels on top of the ocean; at least easier than blasting them into space.)

> What makes you think so? There's always more you can do with more energy. 'Never' is a long time. And there are opportunity costs from other uses you could put land on earth to.

The entire world's power supply could be met by sacrificing just 3.27% of the US [1]. The Sahara desert is already economically useless as it is completely and utterly inhospitable, unable to support life beyond a few shrubs, insects and felines.

> While climate change might become unpleasant, I have no clue what it has to do with any of this?

Simple, the amount of desertified space will grow, and so space that is now unusable for solar power because it can actually be used at the moment can then be used for power.

[1] https://www.axionpower.com/knowledge/power-world-with-solar/

> The entire world's power supply could be met by sacrificing just 3.27% of the US [1]. The Sahara desert is already economically useless as it is completely and utterly inhospitable, unable to support life beyond a few shrubs, insects and felines.

So? We can always grow our energy consumption to meet supply.

> Simple, the amount of desertified space will grow, and so space that is now unusable for solar power because it can actually be used at the moment can then be used for power.

The oceans are a lot bigger than all the deserts put together.