Antimatter spacecraft's engine, illustration. Antimatter propulsion is a theoretical future spaceship technology that uses the energy released by the total annihilation that occurs when antimatter and matter meet. The efficiency is 100 percent as all the mass is converted to energy, producing 1000 times the energy of nuclear fission. The large amounts of energy would make travel to the outer planets easier, and travel to the stars would become feasible. Antimatter is currently formed in small amounts in particle accelerators.