Orion: NASA's Next Big Mission Prepares to Blast Off

Unmanned rocket could carry astronauts to Mars in the future.

This unmanned test mission will launch on Dec. 4 at 7:04 a.m. ET on a Delta IV rocket from Cape Canaveral and will land four and a half hours later with a splashdown 600 miles off the coast of San Diego in the Pacific Ocean.

While in orbit, the spacecraft will circle Earth twice at an altitude of 3,600 miles.

Orion will make re-entry at 20,000 mph with temperatures hitting 4,000 degrees.

NASA will be watching closely to see how Orion holds up during the flight. If successful, the capsule could be used for future long term missions into deep space, including trips to Mars.

Orion seats four astronauts -- one more than NASA's Apollo spacecraft.