Comment by chris_va | Hacker News Reader

Comment by chris_va | Hacker News Reader

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- Zero g manufacturing (good edit, has some potential)

You have something with the spaced based solar (SBSP). The unsolved problem there is the microwave power beaming, which has some technical hurdles (synchronizing microwave frequencies across multiple dishes is apparently hard, but necessary for power beaming, and there is an ozone problem). Any other space based power system has this same transmission problem (people have proposed attaching conductive tethers to orbiting NEOs to drag through the magnetic field).

The "nuclear reactors are dangerous" bit hasn't really been true in a long time (Chernobyl was the worst disaster, but killed a lot fewer people than hydro/coal/etc).

Space is actually not great for computers. Dielectrics change in vacuum, and cooling is actually a big problem (turns out space isn't actually "cold" in the traditional sense, it is insulating, and heat tends to build up). Quantum computers are probably a red herring, there is vey little difference on an atomic scale in/outside of micro-gravity.

Even if you solve the synchronization problem, you still have the main problem with power beaming of the massive sizes needed of the transmitter and receivers at space scale distances, thanks to diffraction.

Microwaves need prohibitively large transmitter/receiver arrays if you go beyond LEO (drag is an issue in LEO). While putting a kilometer^2 scale transmitter in orbit isn't a problem, putting the similarly sized receiver for it on the ground is. At optical or smaller wavelengths, the arrays can be much smaller, but they will still be large structures.

Disclaimer: I worked with a company that does terrestrial optical power beaming.

> putting a kilometer^2 scale transmitter in orbit isn't a problem, putting the similarly sized receiver for it on the ground is

Wow, I would have guessed the exact opposite. What's the reason(s) for the higher difficulty on the ground? Planning permission? Cost of the land? Needing multiple sites in multiple countries for non-geosynchronous orbits?

> Disclaimer: I worked with a company that does terrestrial optical power beaming.

That sounds fascinating. Could you elaborate? What's the power level and the application?

Building the structure itself isn't too hard as it will be mostly empty space. For microwave it will be an area packed with odd looking antennas, optical is basically an off the shelf solar farm (though the cells should be tuned for the application rather than general sunlight).

The hard bit getting all the regulatory ducks in a row, as you will need ground->space no fly zones, environmental approval, not be sited near anything else in case of alignment/focus/astigmatism (side lobes for rf) issues, etc. Generally out in the middle of nowhere there is some endangered animal (or its migration pattern) that will cause no end of issues regulatory wise for something this big/dangerous to wildlife unless you keep the energy density down below that of the sun (at that point you might as well use normal solar). You will also need controls to rapidly shutdown the system (or shunt to new location) in case an aircraft violates the no fly zone or another satellite is about to pass between the transmitter and receiver.

> That sounds fascinating. Could you elaborate? What's the power level and the application?

What they did when I was there was fairly diverse. The biggest was delivering 1kw at a distance of 1km with ~5-10% plug to plug efficiency. The primary application for that system was inflight refueling of electrically powered drones. They normally do much smaller/simpler (10w over dozens of meters) systems for oddball applications (eg: sensors that are sitting on something charged to 500+kv, etc) and power over fiber-optics.

Ha ha I knew someone would point out that vacuum isn't "cold", because lack of matter means heat can't transfer away from hot things. My comment about superconductors and computers tossed a bunch of stuff together I probably should have separated. I agree space wouldn't help for cooling conventional CPUs. Would it still help for superconductivity? (I have no idea.) Also for quantum computers I was wondering if vacuum would have any benefit for decoherence.

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