Comment by ACCount36
1 day ago
This is the kind of transmission line design I've seen proposed for use on the Moon - where hydrocarbons are basically nonexistent, but aluminium and silicon are abundant.
Glass insulated cable sounds like a tech that should be prototyped on smaller scales - and could be somewhat useful on those smaller scales.
> Glass insulated cable sounds like a tech that should be prototyped on smaller scale
Take a close look at an incandescent light bulb... There is an inch of glass insulated cable there...
Yes, but it's just an inch - and we need a continuous extruded wire at least a dozen meters long. Even on the scale of an inch, thermal expansion coefficient mismatch problems exist - this was a notorious issue with manufacturability of early vacuum tubes.
Turns out it's rather tricky to make glass bond to metal well enough.
The glass in a lamp is not for electrical isolation, it's intended to prevent the cable from literally burning up by keeping oxygen out and protective gas in.
When you're on the moon, why bother with glass? You're surrounded by vacuum and dry rock.
I mean, sure, you can't go over 1022 kV or you get positron-electron pair production from free electrons, but that's still true on your outer surface even with insulation.
Would coaxial HVDC let you go further, because there's no external voltage gradient? I assume so, but mega-scale high-voltage engineering in space combines three hard engineering challenges, so I wouldn't want to speak with confidence.
That said, vacuum is also a fantastic thermal insulator, so perhaps you could do superconducting cables more easily.
I've heard of ballistic conductors*, I wonder if that would scale up… basically the same as the current flowing around a magnetosphere at that scale? https://en.wikipedia.org/wiki/Ring_current
On the other hand, you'd have to make the magnetosphere on the moon first, and "let's use the sky as a wire" sounds like the kind of nonsense you get in the "[Nicola] Tesla: The Lost Inventions" booklet that my mum liked, and therefore I want to discount it preemptively even if I can't say why exactly.
* Not superconducting in the quantum sense, but still no resistance because there's nothing to hit: https://en.wikipedia.org/wiki/Ballistic_conduction
"Just burying your wires in lunar regolith" is another proposed option for long range transmission lines, yes!
We don't know how well that would work in practice though, because there's still a few unknowns about how properties of lunar regolith change across distance.
Some wire applications do require isolation though. For example, motor wiring and other coils.
It would be extremely challenging to make usable coils out of glass coated magnet wire - but it's not like there's oil on the Moon waiting to be made into polymer coatings.
Bury? I was thinking just leave it exposed on the surface. Two chonky lines 2-3 meters apart, double use as a railway.
You make a good point about the other uses of insulation, and ISRU, on the moon.
Would ceramics work for transformers?
1 reply →