>>12054404>>12054420(2/2)A slightly better explanation would be to replace those engines with a dynamite.
Assume it explodes inside of a cylinder with one face open. Also assumes it's exactly in the center. When it explodes, the explosion will force the cylindrical (not either lids aka perpendicular to direction of lids) to move. The net force will cancel because it is applied evenly in both directions. This is untrue for the parallel component as the shock wave will moe outside of the opening, essentially not applying any force on the rocket but the one directed to it's opposite face will push that face forward. Since there is an imbalance, the rocket will move forward.
