How much mass would you need for ion thrusters to offset that momentum? It wouldn't be a problem for a species with an active space economy to keep a few satel

How much mass would you need for ion thrusters to offset that momentum? It wouldn't be a problem for a species with an active space economy to keep a few satellites at L1. Should the species no longer have active space travel then eventually the planet would be screwed though, but how long is "eventually", and how long would the satellite have to be in place before the goal is met. As a species we struggle do 5 years projects, let alone 500 or 5000 year projects.