Tethers can theoretically use more efficient propulsion because their thrust requirements are lower. The argon Hall effect thrusters on Starlink satellites have around 7x the specific impulse (fuel efficiency) of Starship engines while needing 7x the energy due to KE=mv^2/2 and having a tiny fraction of the thrust. This energy could come from a giant solar panel rather than the fuel, and every once in a while it could be refueled with a big tanker of liquid argon.
After looking into this a little more because it didn’t seem like ion thrusters would have the requisite thrust, it looks like this whitepaper from boeing explores using electrodynamic interaction with Earth’s magnetic field for thrust (see p. 34) - but they don’t find great numbers on how fast you can correct the orbit using that either, unfortunately.
The numbers for ion don’t seem crazy. To get the impulse to catch a 1,000 ton object every 2 weeks you would need 10,000 Starlink thrusters massing 21 tons, plus 42 MW of power, which is 14 hectares of solar panels at an average of 300 W/m^2. That’s only a couple dozen times the ISS.
Tethers can theoretically use more efficient propulsion because their thrust requirements are lower. The argon Hall effect thrusters on Starlink satellites have around 7x the specific impulse (fuel efficiency) of Starship engines while needing 7x the energy due to KE=mv^2/2 and having a tiny fraction of the thrust. This energy could come from a giant solar panel rather than the fuel, and every once in a while it could be refueled with a big tanker of liquid argon.
After looking into this a little more because it didn’t seem like ion thrusters would have the requisite thrust, it looks like this whitepaper from boeing explores using electrodynamic interaction with Earth’s magnetic field for thrust (see p. 34) - but they don’t find great numbers on how fast you can correct the orbit using that either, unfortunately.
This reminds me of a Brin short story which I think exactly discusses what you’re talking about: https://www.davidbrin.com/tankfarm.htm
The numbers for ion don’t seem crazy. To get the impulse to catch a 1,000 ton object every 2 weeks you would need 10,000 Starlink thrusters massing 21 tons, plus 42 MW of power, which is 14 hectares of solar panels at an average of 300 W/m^2. That’s only a couple dozen times the ISS.