Romulan ships do not make use of matter/antimatter reactors like most vessels but instead of that they make use of an quantum singularity drive. The Quantum Singularity Reactor is one of the greatest Romulan acheivements. Quantum singilarity is the same what happens in a black hole. This so called artificial gravity well can generated a tremendous amount of energy which gives the ships their thrust. An quantum singularity reactor can only be shut down at a docking station due to the fact that it cannot be restarted in space. The reactor itself houses a singularity: a point in space where the laws of physics supposedly break down. What happens here is that matter is continuously fed into the singularity. The gravity from the singularity pulls the matter together, forcing it to not only fuse, but to bump into each other, etc. This causes an enormous amount of energy to be obtained, and we never have to worry about fuel: it is all around us. It is not only more efficient then matter/antimatter drive but also much more powerfull. One of the problems that Federation scientists have had with artificial singularity reactors is that they simply cannot see how the ship can move with this masssive gravtiational anamoly within the heart of the ship. The solution, although the Federation is too egotistical to realize it is that we use the same thing that they do to control gravity: we place a Inertial Dampening Field around the reactor. This way, we trick the ship into thinking the reactor isn't even there at all. This way, our ships are even lighter than Federation ships, allowing us to move faster and respond more quickly to external stimuli. Indeed, this process releases the equivalent of a standard Federation Matter/Antimatter Reaction Assembly.