[MCllorf]

I'm not trained in STEM at all but these discussions are always a little confusing for me because if our goal is to bootstrap mining/manufacturing in space, why does everyone jump to expensive, complicated and inefficient solutions like "energy lasers" when we've had power lines for like 150 years and can make them on-site much more easily?

[extrapickles]

Its likely because bringing a smelter and wire drawing machine don’t feel “space age”. Also most people think of small bases where its not cost effective to bring a bunch of manufacturing capacity as quite a few processes don’t scale down well. Mining is another issue as you would need to find good sources of each major metal within transportable distance of your base.

With the current capital cost of ~$50/W to beam power, its reasonable to think about for small endeavors, but for a base designed for 100k people making power lines onsite is better, as you will need that manufacturing capacity for other things anyway.

[sjansen]

The article mentioned why very quickly while discussing building multiple solar farms so that at least some aren't in shadow at the same time: sending enough cable up on rockets to connect all of them would be more expensive than the "expensive, complicated and inefficient solutions".

[whatshisface]

Well, cables are going to be cheaper at some distance and power beaming will be cheaper at a greater distance, and the question is, where's the crossover.

[h2odragon]

Look at the efficiency numbers on contact free charging pads. "Beaming" fails for power transmission immediately; it needs other factors to justify the efficiency hit; and once you're out of near field its much much worse.

[gpm]

Microwave transmission of power hits 70 or 80% efficiency http://large.stanford.edu/courses/2011/ph240/shu2/

What you're seeing with phones isn't microwave, but inductance, very different technology with very different benefits/drawbacks.

[wongarsu]

Solar panels are quite useful, and they are essentially just beamed power receivers. And if you focus the beam instead of just using a glowing ball of hydrogen, go with a more efficient wavelength and remove all the atmospheric losses, it actually becomes quite efficient.

[Sebb767]

> Solar panels are quite useful, and they are essentially just beamed power receivers

Yes, but they are because their power source is unbelievably large and free. If you look at their efficiency from the perspective of what the sun puts out, they're laughable.

Problem is, with the moon beams we don't have infinite and free source power to waste on inefficiency.

> And if you focus the beam instead of just using a glowing ball of hydrogen, go with a more efficient wavelength and remove all the atmospheric losses, it actually becomes quite efficient.

Focusing the beam is not that easy, you need to hit a moving spot of minimal size with an extremely powerful laser. Avoiding all atmospheric losses is probably not going to work, either. Lastly, you need to get those transmitters built on earth, which, as the OP points out, quite land intensive.

It is a theoretical option, but I would not call it efficient.

[wongarsu]

> Yes, but they are because their power source is unbelievably large and free

Power sources on earth are also plentiful and almost free, compared to building stuff on the moon (at least until we have a lot more infrastructure up there)

[jdavis703]

This question is answered in the article and I guarantee you, most STEM specialities will never discuss this particular problem.

Anyways, the TL;DR is all those cables weigh a lot, so launching them in to space isn’t cheap.

[Uke]

it might be a weight constrain?