A couple of ideas that come with little knowledge, so take it with a big grain of salt: 1. "Electromagnetic Missile" with trajectory who's apogee is just below

A couple of ideas that come with little knowledge, so take it with a big grain of salt: 1. "Electromagnetic Missile" with trajectory who's apogee is just below the targeted space junk. Turn on the electromagnet when just below the space junk to drag down its trajectory slightly, or even down to a de-orbit trajectory. Obviously, this only works with satellites built with magnetic materials. It may just be my outsider's perspective, but non-orbital missiles seem much easier and cheaper than rockets that go into orbital trajectories. Handling the return of the missile is tricky, perhaps it can also self-detonate fairly high in the atmosphere. 2. Ion engines or space sails driven tugs for use in getting to the space junk. My understanding is ion engines have a really favorable specific impulse. An optional chemical engine could be used to quickly de-orbit the tug upon reaching the satellite. Another idea to speed up de-orbit without requiring the tug the whole way would be a spring that would "push" the junk once it reached it, throwing it into an orbit that would more quickly drop it into the atmosphere. Newton could be used to our advantage to also push the tug into a new orbit to reach the next junk satellite sooner. Obviously, arm-chair rocket scientist here, so feasibility of the above ideas can probably quickly be dis-proven.