Roko Mijic

It also doesn't require any wires or electronics in the runway itself. The runway is functionally just a conductive tube with no frills. Admittedly it masses 1000+ tons and is in orbit, but during the acceleration phase there is nothing going on apart from passive effects. (6/)

The runway loses momentum in order to bring a spacecraft up to speed. Its orbital parameters change, and some energy is lost as heat. There are also various structural considerations, sound waves, etc. Many details need to be filled in here, but we think it's doable. (7/)

To mitigate the various hardships that the capture causes to the runway, it will mass somewhere between 150 and 1000 times the mass of the ship it captures, with my guess being around the higher end of that range. For a 1000 ton BFR, this would be up to 1 megaton! (8/)

The main component is a strong vertical tether with a dense counterweight at the lower end and solar panels at the top. The runway is shown as a tube inside a truss structure, supported by cables that attach to the upper and lower counterweights. (10/)

The benefit of having such a runway in operation is that it is a lot easier to get a given payload up to a position ~250km above earth than to get it up and also give it enough tangential velocity to be in orbit. (13/)