Stardrive

While all spacefaring cultures yearn to bypass the universal speed limit that is C, only a handful actually manage to do it, and only a handful of a handful do it right: enter the Stardrive. Rather than fussing about with exotic matter or hyperspace shortcuts, the Stardrive (sometimes referred to as a "string drive" or "that awful black box we don't touch") uses M-theory principles to create a split-second superstring connection between two gravity wells, which the vessel then "rides" as it collapses. External observers estimate average speeds around 3600C, allowing most drive-equipped vessels to travel about 10LY per day without invoking the grim specter of time dilation. Ships with low mass - or larger, more power-hungry drives - can travel significantly faster.
While the most common use of the Stardrive is, as the name implies, to travel between stars, nearly any gravity well can serve as a drive anchor - planets, moons, dangerous spacetime anomalies, etc. - although top speed is significantly lower when using sub-stellar masses. It is also possible to make a "Wild Jump" by allowing the drive to make blind connections, though this is extremely dangerous to both ship and crew. Even targeting an unknown star that you can see is safer than targeting no star at all - explore with care!

Manufacturing

The construction of a Stardrive is fairly simple, though it requires a handful of exotic materials that can only be mined in space.

Inventor(s)

The first inventor of the Stardrive is lost the aeons, though it has certainly been lost and rediscovered many times.

Access & Availability

Stardrive is fairly common amongst spacefaring cultures, due to the self-selection process of becoming an interstellar culture in the first place, though there are a handful still getting by with jump gates or cryosuspension.