CEV

Next year, 33 years after its maiden flight, the space shuttle will retire. What happens after that has become subject to fierce debate within the space agency. The designated successor program, named Constellation, was the darling of previous NASA administrator Michael Griffin, but a new review now has the space agency looking elsewhere for a ride back into the firmament.

If you've ever worked on bikes or cars, you know how annoying it can be to work with both English/imperial and metric units at the same time; well, the same goes doubly with spacecraft, but NASA's theoretically modular and standards-adhering Constellation system is shaping up to be the odd one out in space, where the metric system rules.

When NASA administrator Michael Griffin unveiled the agency's plans for the Crew Exploration Vehicle (CEV), he described it as "Apollo on steroids." The resemblance is easy to seeeach is a blunt-nosed, cone-shaped capsule that's strapped to a rocket and sent to the moon, where it deploys a lunar lander and then returns to Earth for a parachute landing. There are important differences, however:

It's a scene reminiscent of NASA's glory days, back when men still walked on the moon. A space capsule descends under a canopy of three orange-and-blue parachutes, swaying gently in the breeze. The spacecraft splashes down in the Pacific at a leisurely 15 miles an hour, and the chutes settle into the water beside it. A recovery boat rumbles into position beside the spacecraft, and divers hit the water.

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 citizenwith 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.