A diametric drive uses negative matter to achieve propulsion without the need for a reaction mass. It juxtaposes a positive and negative mass in such a way that the negative mass always pulls toward the positive mass. This method creates a local gradient (an inclinating slope within space-time itself) that accelerates the ship. Powerful, localized electricial charges must be maintained to keep the negative mass from becoming unstable during operation.
The major drawback to the diametric drive is its constant need for maintenance and repair. Understanding of negative mass is sketchy at best, and it is this lack of understanding that makes the diametric drive prone to breakdown; the negative mass keeps on destabilizing. Although it has been speculated that the Centauran government has made breakthroughs in this field, no solution to this problem has been forthcoming.
Nevertheless, a diametric engine creates a powerful forward force that allows an approximate 10% increase in speed over the gravitic drive. Its effect is invisible.