Metric Technology

Metric technology is a category of technologies that enable gravity manipulation, and its name refers to the metric tensor, the "shape of spacetime" or the gravity field in general relativity. This is the basis of both FTL and fast reactionless propulsion, which is carried out by a device called a Metric Drive.
Transhuman metric drives are only enabled by the NSET Brane, which allows a drive to circumvent the requirement for planetary quantities of dense stress-energy (or mass-energy roughly speaking) in order to produce a sharp enough curvature or warp. Kardashev metric drives are thought to be capable of fielding colossal energies generated natively by Kardashev technology, freeing them from the constraints of the NSET brane where necessary.

Utility

Metric technology is widely employed in many sectors of industry besides their use in cheap starflight, though limitations due to the NSET brane prevent Kardashev Type 2+ energies from being realized on small scales.
Metric utility ships are the largest ship type and carry the most powerful metric drives, allowing them to carry large capital ships and freighters to travel with at the maximum speeds possible, lay wormholes, affect precision metric engineering, and perform other critical infrastructure duties.

Access & Availability

Metric drives are widely available in civilian starflight, though generally Jumptrucks are the smallest class of vehicle that carry them.

Complexity

The core of metric technology is powerful electromagnets, similar in engineering complexity to those required by torch drives, as well as the critical "capture kernel" that bombards a Planck-scale wormhole with charged particle accelerator streams until it is large enough to stably control using electromagnets. One mouth of the tiny control wormhole is then extruded into the NSET brane, where it can then be oscillated in a programmed pattern that "summons" the requisite gravity sources into existence and maneuvers them around the ship.

Discovery

Early work on metrics that permit faster-than-light travel in a relativistic framework was already under way in Einstein's day, and by the 21st century researchers had produced a number of notable metrics that could conceivably be used for interstellar travel by a Kardashev Type 2+ society. Among them, the wormhole metrics elaborated by Hayward and Morris, Thorne, & Kuhfittig plus the "warp drive" metric advanced by Alcubierre helped to captivate the popular imagination, while the lesser known work by Krasnikov on his "superluminal subway" provided a solution to the problems faced by an Alcubierre warp bubble attempting to go FTL (pushing the bubble FTL would require tachyons, but the subway or Krasnikov tube provided a spacetime tunnel where no component has to push any other component FTL in its local reference frame).