Hugh Pickens DOT Com writes "Miriam Kramer writes at Space.com that in the new movie Elysium, Earth is beyond repair, and the rich and powerful have decided to leave it behind to live in a large, rotating space station stocked with mansions, grass, trees, water and gravity. 'The premise is totally believable to me. I spent 28 years working on NASA's International Space Station and retired last summer as the director of ISS at NASA Headquarters. When I took a look at the Elysium space station, I thought to myself, that's certainly achievable in this millennium,' says Mark Uhran, former director of the International Space Station Division in NASA's Office of Human Exploration and Operations. 'It's clear that the number-one challenge is chemical propulsion.' Nuclear propulsion could be a viable possibility eventually, but the idea isn't ready for prime time yet. 'We learned an incredible amount with [the International Space Station] and we demonstrated that we have the technology to assemble large structures in space.' The bottom line: 'If you threw everything you had at it, could you reach a space station of the scale of Elysium in 150 years?' says Uhran. 'That's a pretty tall order.'"