More than 100 companies across the country will mark a significant milestone April 4, with the launch of Space Shuttle Atlantis: The Shuttle is getting a new lift -- three improved Main Engines that will make the world's only reusable launch vehicle safer and more reliable than ever before.

Companies in 17 states provide parts and materials for the Shuttle's "new" Main Engines.

A shuttle main engine turbopump is carefully assembled. Photo: Pratt & Whitney

One of the most sophisticated rocket engines ever designed, the Space Shuttle Main Engines were developed by NASA's Marshall Space Flight Center in Huntsville, Ala., together with Boeing Rocketdyne of Canoga Park, Calif., and Pratt and Whitney of West Palm Beach, Fla.

The enhanced engines -- called Block II Main Engines -- incorporate an improved high-pressure fuel turbopump with a stronger integral shaft/disk and tougher bearings. The improvements make the "new" engines safer and more reliable, potentially increasing the number of flights between major overhauls.

"NASA's suppliers and their products are an integral part of the Space Shuttle program," said Art Stephenson, director of the Marshall Center.

"Each individual who contributes to the production and delivery of the Shuttle Main Engine is a valued member of our NASA team," Stephenson added. "Each should be proud of the Space Shuttle technologies that have benefited U.S. industry, improved our quality of life and created jobs for Americans."

A single Block II Main Engine was demonstrated in July 2001 on the STS-104 mission, and again on the STS-108 mission in December 2001. The upcoming mission marks the first time the Shuttle will be powered by three of the new engines.

Developed in the 1970s by engineers at the Marshall Center and Rocketdyne, the Shuttle Main Engine performs at greater temperature extremes than any mechanical system in common use today. At minus 423 degrees Fahrenheit, the liquid hydrogen fuel is second only to liquid helium as the coldest liquid on Earth. When it and the liquid oxygen are combusted, the temperature in the main combustion chamber of the engine is 6,000 degrees Fahrenheit, hotter than the boiling point of iron.

If the three engines pumped water instead of fuel, they could drain an average-sized home swimming pool in 25 seconds. At lift off, each engine produces 417,975 pounds of thrust.

"Our suppliers' diligent attention to detail is critical to the safe and reliable performance of the Shuttle's Main Engine," said George Hopson, manager of the Space Shuttle Main Engine Project Office at the Marshall Center. "Each one is responsible for preserving the safety of the world's astronaut corps."

The new fuel turbopump -- made by Pratt and Whitney -- is not much larger than an automobile engine, yet it generates 360 times the horsepower.

Boeing Rocketdyne is responsible for the manufacture of the Space Shuttle Main Engine. NASA's Stennis Space Center in Mississippi tests the engines.

The Marshall Center is a key leader in NASA's development of space transportation and propulsion systems. The Space Shuttle Projects Office at Marshall oversees the Main Engines, the Space Shuttle's Solid Rocket Boosters and Reusable Solid Rocket Motors, and the External Tank.

Editor's Note: The companies providing parts and supplies to the Shuttle Main Engine program are located in Alabama, Arizona, California, Connecticut, Florida, Indiana, Massachusetts, Michigan, Minnesota, New Jersey, New York, New Hampshire, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia.