The space shuttle may be in the best shape of its life, but in the forward-looking world of space travel, it’s a grizzled senior citizen–with mandatory retirement looming in 2010. The race is on to develop a replacement.

Still on the drawing board, NASA’s next-generation spacecraft will be called the “Crew” Exploration Vehicle, or CEV. It’s expected to begin carrying astronauts to low-Earth orbit by 2014 and to the moon by 2020.

Eleven aerospace-industry teams are vying for two NASA contracts to develop CEV concepts; the winners will be announced by early September. The most prominent contenders are Lockheed Martin and Northrop Grumman (which is partnered with Boeing). The two winning teams will demonstrate their concepts in unmanned flights in 2008, and one team will then be chosen to build the CEV.
For now, teams are mum about design details, but it´s likely that the CEV will be a capsule that rides into orbit onboard another vehicle and that it will be considerably smaller than the shuttle. Unlike the shuttle, CEV will be reconfigurable for a lunar journey. Cleon Lacefield, Lockheed Martin´s CEV program manager, says that additional components could be attached to the craft in low-Earth orbit that would send it to the moon-making a giant rocket like the Saturn V unnecessary. â€It´s more of a modular approach than what we´ve seen in the past,†he says.