I've seen a lot of articles in various science magazines focusing on how difficult it is to store antimatter. There is, of course, a possible way around this. The way around the problem is to **only generate the antimatter when it is needed**.
If you look at the problem that way, then the antimatter storage problem goes away, and it now becomes a matter (excuse the pun) of creating the antimatter (from ordinary matter). That would itself be difficult, but it would still be enormously easier than trying to store antimatter.

"the current cost of that gram of antimatter is roughly estimated at about a trillion US dollars."
this is why our monetary economy doesnt work. all these technological advancements that would be ready immediately if the resources were given to it, but in this current world, money is all that matters to survive...
follow the zeitgeist movement for a new economic system!

@Tony Zeitgeist!
As soon as I read that, I thought the same thing... A fantastic energy source who could be available and perfected with experiments as of right now is being delayed. And so is our development.

re; mooseman
How much energy and mass does it require to produce antimatter? hint you never get more energy out of a system than you put in.
It sounds to me like you're trying to solve one problem by creating a bigger one.

A rocket is capable of moving faster than its exhaust. Remember, it's the reaction to the exhaust in the same frame of reference that provides the acceleration, not the "absolute" velocity of the exhaust. So the fact that the exhaust travels at .69 c would not impede the craft using the engine from greater velocities, including those very close to the speed of light. Other factors (especially radiation from collisions with the rare but present particles in space) would limit the speed of the craft, not the exhaust velocity.
Wouldn't it be possible to collect anti-protons or positrons in near Earth space? To collect positrons you'd use something like a mass spec where you'd electrostatically accelerate negatively charged anti-protons around a curved track and put an as yet hypothetical "anti-matter collector bottle" where negatively charged particles of the proton's mass would go. The charge would separate anti-protons from the positively charged protons and the mass would separate the anti-protons from electrons. A similar collection apparatus could be used to collect positrons. I wonder why I've not seen this idea anywhere- so there must be a fault in it.

@Tony So we should all surrender our freedoms and becomes slaves to work for this purpose so you can travel through space ? Zeitgeist = collectivist = global poverty

Antimatter is hard to be produced, stored, and manipulated for propulsion. Better is the fusion-powered plasma turbine. http://www.youtube.com/watch?v=ro5-QYqqxzM

You're not thinking, people. Interstellar travel will come, but lets build this puppy and try it out around the solar system. Dr. Robert Forward described the problems of "containing" antimatter and using it for an interplanetary drive 25 years ago. Among the things he mentioned is that antimatter costs so much because we've only been using it for research. We have never tried to optimize the process to mass produce it. Check with the National Space Society. I bet somebody there still has copies of his work. I'm just going by memory.

re; John J. Peloquin
While true, the lower the exhaust velocity the more propellent that is required to accelerate a specified mass to any specified velocity.
re; fruitsalad
Well said.