Reference 5 is https://arxiv.org/abs/1609.00709

They are proposing a tether that’s about 300,000 km long and 48,000 kg mass, so 0.16g/m

Which seems very small.

Density is about the same as water, so the diameter is about 0.12mm which (for fishing line) has a breaking strain of about 10N. UHMWPE’s strength is about 6 GPa, so (0.00012)^2 * 6e9 is about 100N.

Hmm.

I seem to recall a space elevator's tether is extremely nonuniform. Eg- it might need to be 100meter diameter at ground level and barely more substantial than aether 3/4ths the way up, then expand out more.

It’s not a tower, so it’s the other way around. At ground level, the cable only has to hold up the weight of a car. At a kilometer of height, it has to hold up that car plus a kilometer of tether.

At (about; adding cars to the tether changes things a bit) geostationary height (in this case I guess that could be called lunastationary), forces on the tether start going upwards, and tether size can go down as you go further up.

See https://en.wikipedia.org/wiki/Space_elevator#Cable