Conjoiner drives were starship engines built by the Conjoiners that used quantum mechanics to propel starships up to relativistic speeds, giving such ships the name "lighthuggers". It should be noted that the Conjoiners did not actually invent the drive themselves, but received the instructions for it via the Exordium Project.
Integration into ships
The drives had six manual control dials that allowed the power of the engines to be varied. Lighthuggers mounted a pair of Conjoiner drives, both of which were controlled in tandem. Drives would be mounted at the end of spars to protect Demarchist or ultranaut crew and passengers from the radiation they produced.
Principles of operation
Conjoiner drives contained a small wormhole linked to the very deep past, through which they draw their propulsion energies from the Quark-gluon plasma created by the Big Bang.
A pair of drives is controlled by a disembodied Conjoiner brain that performs rapid calculations to control the internal drive reactions.
As the drive power was increased, so did the risk of an uncontrolled, ship-destroying explosion. If the turbulence within the drive exceeded the ability of the brain to compensate for, the drive would explode. It would also explode if the gap between the two drives of any one ship grew too large; this occurred because the Conjoiner brain was housed within one of the engines and controlled the other remotely, and thus once the remotely controlled drive passed out of the brain's control, the internal reactions would quickly spiral out of control. The drive was also designed to explode if non-Conjoiners attempted to open it for reverse engineering purposes.
While each pair of drives represents a conjoiner who volunteered to fill this role and could 'retire' at any time, and while innards of the drive were designed not to be tampered with by any non-conjoiner, the location of the drives at a given moment would be dependent on the crew of the ship they powered; drives were often carefully salvaged from ships to be transferred to others by reattaching them to new spars, while maintaining the proper distance between drives all the while.
The emission of tau-neutrinos by the drives was eventually found to attract the Inhibitors, and, subsequent to a 100-year suspension of their production, successful experiments resulted in the "quiet" Conjoiner Drive.
A small part of the workings of the drives is revealed in the short story "Galactic North", and a drive is a major part of the plot of the short story "Weather", both collected in the short story collection also called Galactic North.