The 'Impossible' EM Drive Is About to Be Tested in Space It uses electromagnetic waves as ‘fuel’, creating thrust by bouncing microwave photons back and forth inside a cone-shaped closed metal cavity. This causes the ‘pointy end’ of the EM Drive to accelerate in the opposite direction that the drive is going. The pointy end is sucked in the direction of the larger end. I'll skip truisms about large ends sucking less and just note that the way the the drive is described, the small end pulls the device backward (negative thrust). People are used to rocket nozzles where the big end pushes. EMDrive is exactly backwards. The small end pulls. So the device goes the reverse direction from a similarly shaped rocket nozzle.