The basic physics at work here is conservation of momentum. Rockets work because they are sending mass in the opposite direction of the main vessel. If you draw

The basic physics at work here is conservation of momentum. Rockets work because they are sending mass in the opposite direction of the main vessel. If you draw a box around the whole system (rocket + spent fuel), you have net zero momentum. There is a whole separate device called an EM Drive, which claims to basically violate conservation of momentum. It is highly controversial, and unlikely to be anything other than a measurement mistake.