An upgraded Space Shuttle engine block 2 engine sits in the Space Shuttle Main Engine Processing Facility.

An upgraded Space Shuttle main engine (block 2 engine) sits in the Space Shuttle Main Engine Processing Facility. The new engine will be installed for its first flight on the orbiter Atlantis, on mission STS-104. The Block II Main Engine configuration is manufactured by Boeing Rocketdyne in Canoga Park, Calif., and includes a new Pratt & Whitney high-pressure fuel turbo pump. Engine improvements are managed by NASA’s Marshall Space Flight Center in Huntsville, Ala. Each Space Shuttle Main Engine is 14 feet (4.3 meters) long, weighs about 7,000 pounds (3,175 kilograms), and is 7.5 feet (2.3 meters) in diameter at the end of the nozzle