Torsion plate

Torsion plates are a maneuver drive system employed almost ubiquitously aboard Forerunner starships. The plates convert harvested energy into a form of inertia-less thrust (presumably torsion fields), and are considered so simple and widely-applicable they are near-universally used across the Forerunner fleet. Other forms of propulsion are used, though they are generally used for extremely specific niche or aesthetic purposes.

Supernal Spiral-class keyships such as Anodyne Spirit are equipped with torsion drivers, as are more terrestrial (though still floating) structures such as skydocks.