Actually the only vaguely plausible-ish (though by no means convincing) designs I've heard of for physically realisable time machines work like this. You do some horrendous things with spacetime curvature and you get something that can send you back in time, but no further back than the point at which you constructed your horrendously curved spacetime thingy.

Paul Davis has a short book How To Build A Time Machine which does it this way, if I recall correctly (it's been a while since I read it).