Vortex (1983)

Publisher's blurb S.O.S. S.O.S. Starbase trapped in the vortex A blast of black light. The universe shakes and trembles and shrieks. Null-Space has spewed forth the Vortex, a deadly gravitational whirlpool. Your Starbase is immobilized by its unseen grip just as the Valtron fleet attacks. These methane-breathing aliens spiral into the coils of the Vortex to destroy Starbase, earth's farthest outpost. You must hold them on the frontier. But they're lightfast, suicidal, fanatical. Superhuman skill and dedication are called for... and you alone can answer.