You are thinking of the Alcubierre drive, Gorwo. Issac covered it on the FTL series. The problems are you need to discover some form of matter with negative mass and you would have to build the ship to withstand temperatures similar to those inside the cores of the largest stars. And, yes, the expansion of spacetime due to dark energy creates new spacetime. And, since spacetime itself has a certain intrinsic energy, the total energy of the universe is always increasing. Imagine the universe continuing on past heat death(which assumes a continuing expansion) - possibly infinite energy but no way to use any of it. Bummer.