PSL (Percentage of the Speed of Light) is an official Systems Commonwealth unit of measurement, but is universally accepted and used by virtually every other race in the Commonwealth as well as un-allied ones because it transcends cultural boundaries and remains an effective and representative way of measuring speed. It measures sublight speeds of spacecraft. Since any PSL above 3 percent would utterly destroy any organic life and even the ship that was accelerating. Because of the drastic and severe effects that acceleration or any sudden stop or turn done while traveling at almost any PSL, ships use a Gravity Field Generator, Anti-Gravity fields, and Inertial Dampeners to hold together the ships and allow space travel, galactic travel, and civilization to be possible.