Space may be the final frontier, but it's a well-tread one, to be sure -- especially this year, with the release of Alfonso Cuarón's breathtaking "Gravity" and the Orson Scott Card adaptation "Ender's Game" out this weekend.

"Ender's Game" takes place in a distant future in which Earth is still smarting from an attack by an alien race known as Formics (or colloquially, as buggers). Children are recruited from an early age to be tested and trained in anticipation of the extra-terrestrials' return. Ender Wiggin (played by Asa Butterfield) is one such recruit or, more accurately, the recruit. The school's administrators, including Harrison Ford's gruff Colonel Graff, have singled out the boy as the world's last chance for survival.

With extensive sequences in which Ender and his fellow launchies learn to adapt to a zero-G atmosphere, while also learning the tactical and strategic skills that will save their species, the young actors were put through their own boot camp to perfect their weightless performances.

"Those kids worked really hard. They were trained by Cirque du Soleil aerialists, and they also had the chance to go to a space camp, where they were able to speak with real astronauts about what it feels like to be in a weightless environment," Ford explained. "And believe me, it's hard. I have one tiny little scene hanging from wires. They're out in a green-screen volume where there's nothing to hang on to, where they're really responsible for balancing themselves on wires."

Many readers of Card's 1985 novel have pondered how the intricate scenes would be brought to life, and it was a concern shared by the movie's stars.

"When you read it, you wonder how they're going to do it, and then you find yourself doing it, and you don't really know what you're doing," Hailee Steinfeld, who plays Petra, said.

Steinfeld found the troupe of Cirque du Soleil performers invaluable while preparing for her high-flying role.

"They would show us what we were doing, and we're like, 'Oh, awesome. It looks great. It looks doable,' " she recalled. " And we get up there, and we're like, 'How is this humanly possible? How do you move your body that way?' They were so talented. They made it look so easy. They created these incredible rigs that really helped us pull off that zero-gravity feel."

"It was pretty much all green screen and just floating there with very little to react off of," agreed Butterfield. "It was quite interesting."