SCIENCE HELP, Especially if you're good at FORCE!?

In the both movies Alien and Aliens, in the ending scenes the main character Ripley opens the hatch of her spaceship and sucks the alien into outer space. What force(s) cause the alien to be sucked out of the ship so quickly, violently, and effectively? Would the same solution to get rid of the alien off the ship work if Ripley’s spaceship were on the surface of a planet like Earth? Explain.