The Fission Drive (also called the Anti-Matter Drive) works in the same way the Fussion Drive does, only in reverse. The Fission Drive is used for normal space propulsion (not Extra Solar, as the Fussion Drive.) Though the Drive is nowhere near perfection, it has been developed enough to be used by special ships.
Ships using the Fission Drive have to be specifically modified. Cargo areas are used to store small quantities of Anti-Matter which are fed into the main engine core. The drive core then breaks down the Anti-Matter into electrons which exit the main exhaust ports as electron "clouds." These clouds propel the ship the same way as the standard Ion Drive, only much more efficiently and at much higher speeds.
No ill effects have been caused by the Fission Drive as of yet, either to the pilots or their craft. However, pilots should still be aware of the dangers in flying Fission Drive ships. In order to carry the Fission Drive, ships must lighten hull strength and carry lighter shields. Weapons capability usual suffers several. Strict weight limits are always placed on Fission Drive ships.
Another danger of these advanced ship types are the extremely powerful shockwaves caused by a Fission Drive reaching critical status. These shockwaves can be as powerful as a small cruiser explosion.
With a few more years of testing the Fission Drive could very possibly take the place of the Ion Drive. Until such a time, the only fighters equiped with the Fission Drive are the experimental Eclipse and Athena II bombers.