There are lots of designs for electromagnetic thrusters, ion drives, etc. They all work in theory but in practice there are problems with them.
Barring science fiction, the only way to make something move in space is to throw something out the back and rely on Newton's 3rd law. It then becomes a matter of how much (mass) and how hard (velocity) you can throw stuff out the back. A rocket motor throws a lot of stuff very fast. Electromagnetic drives throw infinitesimally small stuff extremely fast. It works but, so far, not good enough.
Things like EMdrive claim that they will violate conservation of momentum; i.e.: they will give the effect of throwing something out the back without actually throwing something at all. In terms of the physics involved it's not just a free lunch it's a self-licking free ice-cream cone. Calling that kind of stuff "quack science" usually insults the quacks, who like to pretend to be at least bound by physical law as it appears to be. EMdrive makes as much sense (and has as much experimental science behind it to back it up) as jumping up in the air a clicking your heels to get somewhere. Sure, it might happen. But don't get excited until it actually does.
That things like EMdrive get ink at all is due to two things:
- A lot of fringe scientists are relentless in promoting their ideas. Oddly, they prefer to go around talking to reporters about secret stuff, rather than generating actual testable results. They are either con-artists or delusional. But, because they're not actually doing, you know, repeatable experiments and establishing the scientific framework in which those experiments can be interpreted, they have a lot of time to give interviews, write books, and talk to journalists.
- Science journalism is dead. The number of things a typical scientific journalist gets wrong almost always outnumber the actual facts in any given situation. With the advent of internet journalism, in which any bonehead who can set up Wordpress can run a "news site" it's even worse.
Tl;dr
Don't get excited.
