NASA has awarded Pratt and Whitney Rocketdyne a contract change to provide additional sea-level and simulated-altitude ground tests for the J-2X rocket engine. Under the revised contract, engineers will conduct an additional 38 sea-level and 27 simulated-altitude tests on the J-2X engine at Stennis Space Center.

The additional testing will increase data accuracy and reliability for development of the J-2X engine, which will power the new Ares I and Ares V launch vehicles.

NASA's Ares vehicles will carry future astronauts to the International Space Station and the moon. Testing is expected to begin in late 2010.

"This contract will allow us to move from the development stage to the certification stage with a more mature engine design," said John Vilja, J-2X program manager, Pratt and Whitney Rocketdyne.

"Our goal is provide 100 percent mission success for the future Ares I and V launch vehicles."

The simulated-altitude ground tests will be conducted in a NASA test stand being built at Stennis Space Center specifically for the J-2X engine.

The new test stand will allow engineers to simulate conditions at altitudes up to 100,000 feet by generating steam to reduce pressure in the test cell.