Anti-matter will yield 200% efficiency. Matter+Anti-Matter = No Matter, all energy. E=MC/\2. Imagine having an object of one gram. E = 1 * (the
speed of light)/\2. That's a lot of energy. (By the way, energy is written in Joules... or so I'm lead to beleive).
yeah, the problem with anti-matter is that theres matter. doesnt bode well for keeping anti-matter. you'd need to build anti-matter storage
containers in a vacuum so we dont go anihilating things we want to fire at the stars.