[alliecat]

"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.

[vpribish]

physics says no. There was something wrong with that demo if this was the conclusion.

[tlb]

Feynman says yes, except at very low speeds. https://en.wikipedia.org/wiki/Feynman_sprinkler

[xadhominemx]

Nah the demo was right. The impulse from the sucking (ie air molecules bouncing off the inside of the fan blade) is countered by the impulse from the air molecules bouncing off the inside off the back T-pipe. Different at a low Reynolds number with a reversible flow.