Negamass

Negamass is a special form of exotic matter not found in nature that has [negative mass]. It exhibits very strange properties such as being repelled by normal matter, and accelerating towards any force applied to it instead of in the direction of that force. Its most common uses are in stabilizing the microwormholes of Daedalus ships, stabilizing wormholes that connect the inhabited universe, and acting as a core and primary propulsion system of Daedalus ships. It is also occasionally used as a power source and in weaponry, almost exclusively by the Free Persephone Union.