Tractor Beam Explanation
You have to build a Tractor Beam and a Tractor Beam Target, then you have to configure the tractor beam by selecting the target and the projectile that you want to be guided.
Not all projectiles will be affected equally, some may require more than multiple Tractor Beams to feel the effect (huge asteroids for example).
If you have a Radar, select the projectile and you will see how it’s trajectory is changing.
If you did not disable the cosmetic particles, tractor beam will show swarm of particles flying towards the projectile and from projectile to the target, that’s the indication that it’s doing it’s job.