Okay, let's back up. The conception of "tachyon" I learned (from the number two guy at LIGO no less) was that c, nature's speed limit, meant getting past the speed of light consumed all the energy in the universe thus you ain't gonna do it. However, since E=mc^2 can be solved hyperbolically as well as parabolically, relativity doesn't rule out particles that are just as bound to move faster than the speed of light, never to slow to it. However, you have to turn mass into an imaginary number and things null out real good when you try to cross the asymptote. I'm definitely the straight guy who delivers "but professor" exposition in these stage plays, though.Regarding detection, I'll need to do some further reading, but I think it's entirely dependent on the formulation.