Well, the key is to not take thousands of years about it. Honestly, I doubt we will ever have thousand year missions, unless our lifespans commensurately grow,

Well, the key is to not take thousands of years about it. Honestly, I doubt we will ever have thousand year missions, unless our lifespans commensurately grow, as humans don't have a great track record when it comes to long term projects. There are ways, but they are expensive and not without risk. Nuclear pulse propulsion (orion) can yield vast acceleration, and fusion rockets, while unproven, are feasible. You then have less exotic options such as laser driven light-sails and nuclear powered ion drives. If we were prepared to throw half a trillion bucks at the problem we could see a flyby in our lifetimes - but without a damn good reason, it won't happen.