The Orion is a non-starter ever since the Nuclear Test Ban Treaty and the Outer Space Treaty forbid the use of "weapons of mass destruction" in space. It simply won't happen.

We have not come close to generating a break-even nuclear fusion reaction on the ground (where size and mass isn't a concern), much less being able to build a flight propulsion system (where size and mass are crucial). Until you can build a fusion reactor that not only produces more energy than it consumes, but can be build light enough to launch into space, Daedalus is nothing but a beautiful pipe dream.

As for anti-matter, we can either find it or make it. Finding antimatter has proven pretty difficult and right now, our ability to make it is very limited. You see, e=mc^2 works both ways. It take a butt-load (precise scientific term) of energy to produce even a miniscule amount of matter. For example, if approximately 50 grams of matter were converted to energy, you'd get the equivalent of 1 megaton (1 million tons of TNT) of energy. Like I said, the equation works both ways - it would take the equivalent of 1 megaton of energy to produce 50 grams of matter (at 100% efficiency). Once you have the anti-matter and a containment system (that has to approach nearly 100% efficiency), you still have to find a way to harness the incredible energy produced to create some form of usable thrust.

And when it comes to reaching light speed, relativitistic effects becomes a substancial factor. For example, as something approaches light speed, it's mass increases exponentially. As the velocity approaches the speed of light, the mass approaches infinity, meaning the amount of energy required to accelerate the vehicle also approaches infinity. To date, relativity has held up to every test. Unless we find a way around it, there are limits to what we may ever be able to achieve.