"There is a lot of evidence to suggest that the geometry drive isn't just a strange device we recovered in alien ruins. It is a device that has been specifically tailored to be easy to build and to use, even for a somewhat low-tech civilisation. An open-source faster than light device, if you will." -- quote attributed to Rani Spengler.

Fragments of a free-floating geometry drive.

Many a purist would argue that calling the geometry drive a faster-than-light device is somewhat misleading, as by definition the geometry drive doesn't allow a ship to travel faster than light. In truth, it doesn't allow a ship to travel at all. It is not an engine. It is a device that is capable of instantaneously translating an object from a location in three-dimensional space to virtually any other location, be it a centimetre or five thousand lightyears away. If the what of the geometry drive is well-understood, the how remains a complete mystery. Given that translations fully conserve momentum and ignore obstacles, it is assumed that geometry drives fold space in four dimensions to allow for teleportation with unlimited range. The actual process through which the drive folds space is completely unknown: it is only assumed that the drive is capable of performing this process by its mere existence, as it barely draws any power when installed aboard a ship. The accuracy of a drive is generally measured in hundreds of meters, which makes them inadequate for micro-jumps.

Punched paper cards containing basic translation data for a freighter drive*.

In very simple terms, a geometry drive presents itself under the shape of a cube or sphere, sometimes a cylinder with a size relative to the volume of the ship being displaced. Geometry drives are made of a crystalline compound harvested from pseudonigella stellaris flowers. They are stored in canisters which are to be installed as close as possible to the ship's centre of gravity - this is not a hard requirement but greatly facilitates navigation computation. Geometry drives are inert and transparent when not connected to a power source and start emitting a white-blue light when submitted to electrical current. Crewmembers commonly joke about geometry drives being the safest equipment aboard a spacecraft and they aren't wrong: the worst thing that may happen to a drive is to be shattered, in which case they immediately cease to operate. The fact that they only require a residual amount of power makes them the last element to fail in case of power loss.

To perform a translation, a ship is first required to have a correctly sized, powered geometry drive. Then, the crew has to calculate a translation solution. This is where the main limitation of the drive comes into play. In theory, a geometry drive has limitless range, in practice, this range is limited by the computing power required to calculate the translation. In fact, the faster-than-light capacity of a ship is often defined by its mass-to-computing-power ratio: the higher it is, the faster the ship can compute a translation. Most smaller ships rely on external navigation stations for their computations. The lack of a universal reference frame in space means that all translations have to be calculated separately, even for similar journeys. Upon exiting translation, ships conserve their momentum, which can be a problem for ships with limited delta-v.

The geometry drive is alien in origin, its design was directly taken from those found on the Needle, an alien which bore a series of plates carrying schematics in a strangely understandable form that were reverse-engineered by Rani Spengler's team. Though clearly the work of a more advanced civilization, it proved strangely simple to recreate and transpose into human ship, to the point some have wondered if its modular nature isn't intentional: like a gift, sent through the void to civilisations reaching for the stars. 

*Credit: Marcin Wichary.