The Emthruster: Thrust without reaction?

[Drashner1]

Of course photon drives aren't reactionless drives. They are, however, functionally equivalent in that nothing material has to be chucked overboard to get the thrust. And since propellant mass is the major problem for reaction drives...

However, you have to consume something material to get the energy to generate the photons. And the efficiency of a photon drive is abysmal - something like 300+ MW of energy needed to generate a single pound of thrust IIRC.

Incidentally, I don't think antimatter would be quite such a magic fuel as some people think. The reason is that a significant proportion of the energy is generated in forms that are completely useless, such as neutrinos.

Suggest you read Forward's work on this. He did a pretty thorough analysis of antimatter propulsion for the Air Force before his death and addresses this issue pretty completely. The result is still a drive that leaves everything else in the dust.

Todd