vansig wrote:

Just a matter of finding out how to build 40000 klicks of carbon nanotube cable that weighs less than a conventional rocket can carry and you’re halfway there.

What’s this i hear about colossal carbon tubes being a better choice for tether material? they’re already macroscopic, and when you look at breaking length, they exceed nanotubes because they are less dense.

http://en.wikipedia.org/wiki/Colossal_carbon_tube

Looks good at first glance. The last sentence says it’s strong enough, and I’m reading the ability to make very long continuous lengths into the article. 69,000 miles long, though, is still going to be a BIG spool or few. But at least that would move the engineering from the tether to deploying the tether. Much nicer challenge to have.