"Sucking" doesn't actually generate any thrust - In highschool, my physics teacher did a demo with a T-shaped pipe with a fan in the middle, suspended from some string.
Without the T, the pipe moved as you'd expect. With the T directing the airflow in equal proportions perpendicular to the axis of the pipe, the pipe stayed still as if the fan wasn't on at all.
Without the T, the pipe moved as you'd expect. With the T directing the airflow in equal proportions perpendicular to the axis of the pipe, the pipe stayed still as if the fan wasn't on at all.