Until a working prototype is built, I will be treating the field of warp drives (even sublight warp) with a healthy dose of skepticism. Glad people are working on it though.
It's not faster than light speed. So not so sci-fi. But yes, with the current tehnology is not possible to make. BUT the theory checks out. Maybe in 50 years.
More than that. Gravity is weak; gravity-based technologies inevitably need insane amounts of material to work. This particular metric also involves shedding mass, y'know, like a rocket would have anyway.
Wasn't this story posted already here? I don't want to rehash if I don't have to.