You could direct the waste in two beams perpendicular to the plane of the galaxy, in order to balance net thrust.<p>I question how stealthy that would really make you, though.  If someone was bothering to look for stealthy civilizations, they&#x27;d just have to scatter some observatories around their region of the galaxy, then watch.  Eventually, your structure would occult a star from the POV of one of those observatories, or they&#x27;d pick up your beam scattering in interstellar gasses or dust clouds.