No, I wasn't eyeballing, but perhaps someone else was. I went looking for the dielectric strength of vacuum and I found a chart with values for a bunch of different things including vacuum.
And I don't understand the connection to the Van Allen belts--I'm talking about sunlight knocking electrons off your conductors.
> I went looking for the dielectric strength of vacuum and I found a chart with values for a bunch of different things including vacuum.
That's even more wrong than looking up the value of acceleration due to gravity and applying "9.8m/s/s" to the full length of a structure several times Earth's radius (which was also being done in these comments).
Think critically: when you're reducing pressure, at what point does it become "a vacuum"? Answer: there is no hard cut-off point.
> And I don't understand the connection to the Van Allen belts
You mentioned free electrons. The thing Van Allen belts are, is fast-moving charged particles captured by Earth's magnetic field.
> I'm talking about sunlight knocking electrons off your conductors.
Very easy to defend against photoelectric emission.
Just to re-iterate, if you're lifting something up with a magnetic field, it's non-contact. You can hide the conductors behind any thin non-magnetic barrier you want and it still works.
Say, Selenium, with a work function of 5.9 eV. Tiny percentage of the solar flux is above that.
Even just shading them from the sunlight would work. Like, a sun-shade held off to one side.
Also, you could just have the return line inside the tether: If the supply is on the outside, return on the inside, you can even use the structure of the tether itself as shielding — coaxial voltage differential, so the voltage difference between supply and return lines due to load creates negligible external electrical field.
Honestly, this feels like you've just decided it won't work and are deliberately choosing the worst possible design to fit that conclusion. Extra weird as "but we can't actually build carbon nanotubes longer than 55 cm yet" is a great deal more important than all the stuff I've listed that we can do.
And I don't understand the connection to the Van Allen belts--I'm talking about sunlight knocking electrons off your conductors.