Spacers

Genetically engineered humans that have been created to endure the rigors of 4th dimensional space-jump travel.

The folding of time and space is incomprehensible and unkind to the human mind, driving many crazy if they are awake during the journey.

For that reason, spacers are genetically engineered humans with the ability to function and perform their duties under these rigorous conditions.

With elongated limbs and torsos, electronic electrodes implanted and circumnavigating their bodies, they barely resemble their human ancestors.

Cleon XIII even said he "barely considers them human". S1E6.

Prior to the Spacers operating the controls of the jump ships, the navigational officer on a jump ship had to have a special surgery allowing him to communicate with the ship's AI. This surgery involved implanting an access port at the base of the skull so the officer could be hard-wired directly into the ship's navigational systems. Jumping, apparently, is as much art as science, and required a human touch.