"It has to be a great time for my son. I can't miss him," she said before she would star in the space thriller
Credit: Warner Bros.

Without giving away any plot details, how did Sandra Bullock stomach all the weightless special effects she had to contend with while making Gravity – which, with an estimated $55.6 million box-office take this weekend, has set a record for the biggest October movie opening of all time?

Though Bullock had costar George Clooney often at her side, “I would feel sorry for her all the time,” director Alfonso Cuarén told the Associated Press about his leading lady.

Lightening that burden, Bullock said, was the warm atmosphere Cuaré provided on the set, which was further enhanced by having her 3½-year-old son, Louis, with her.

” ‘It has to be a great time for my son. I can’t miss him. If I miss him, I will be of no use to you,’ ” Bullock recalled telling Cuarén and the movie’s producers before she accepted the role.

” ‘You know, he’s just learning how to walk. So guess what’s going to happen? I have to go! He’s taking steps!’ ”

Everyone cooperated in that department, she says. “They made it so. It was a family film. Everyone had kids. So everyone knew the value of that. So they said, ‘If we make it amazing for him right where you are, will you be okay?’ And I said, ‘Yeah.’ ”

For the actual shooting of the production, Bullock, 49, was all by herself in front of the camera on a London soundstage, attached to newly devised rigs that simulated constant free fall in space and weightlessness. (Cuarén, whose direction is drawing critical raves, not only cowrote the screenplay with his son Jonas, but he spent four years developing the film using new technology for the visual effects, reports AP.)

“You’re frustrated because you can’t accomplish something,” Bullock, who plays NASA medical engineer Ryan Stone, said of defying gravity, as well as meeting the physical demand of positioning her body to match precise lighting and camera cues – a sensation she likens to therapy.

“There’s no control,” said the Oscar winner. “I was always out of my element. I learned so much on a daily basis. And I just went, Wow, isn’t that funny how being miserable every day physically and then emotionally because of work then turns – makes you open to whatever is coming your way.”