It seems NASA is looking at the feasibility of using a positron reactor as the main engine of a mission to Mars. Although the NASA article notes several advantages of using an anti-matter engine (you only need about 10mg of positron fuel for the entire mission), it would cost upwards of $250 million to create the amount of fuel required and who knows how much to create the magnetic containment field to hold it.
I'm no rocket scientist so maybe the problems of building such a reactor can be solved. Or maybe not. But if they can, it could be another giant leap for mankind (to coin a phrase -Ed.).
