Can a magnetic field be made around a satellite for a split second to gain or loose momentum from another satellite or debris with a few passes with a near-miss trajectories on larger debris? Could a less precise method be used by keeping the magnetic field on while passing the object slinging it out of orbit?
A magnetic field is one way for one satellite to exert a force on another, changing the orbits of both. Since satellites are mostly made of aluminium, titanium and carbon fibre based composites, however, it is not a very efficient one, a powerful magnet would be needed to produce a small force.
Also, if the "predator" is in a similar orbit to the target, it won't tend to pull it out of orbit, and if it's in a very different orbit, they will only be in range of any feasible magnet for a few milliseconds, which won't do much.
So, while it's not against the laws of physics, it doesn't seem likely to be a good engineering solution.
No, the range of a magnetic field is too short to be usable.
- Magnetic field strength is proportional to 1/r3, so a magnetic field is only effective at very short distances (less than 10 meters), and quickly becomes way too effective when the debris is in range.
- You can only attract other objects using a magnet, you can't repel them. So you have to be very careful, or the debris will ram your magnetic device at high speed.
- Switching an electromagnet off quickly is difficult. Switching the magnet off causes a voltage spike in the circuit, the net effect is that the magnetic field takes a while to disappear. Not what you want when you're attracting debris at high speed.
The strongest magnets in commercial use today are in MRI scanners. These typically use superconducting magnets with a field strength in the region of 1 T. When you put a metal object in the same room as the MRI scanner, it will be attracted by the magnetic field, shoot across the room and be trapped in the center of the magnet. Outside the MRI room (say 5 meters away) the magnetic force is too small to be noticeable. That's how small the usable range of a magnet is.
If you use a superconducting magnet, switching it off is even slower as you have to dissipate the current gradually (preferably without boiling the coolant).