NASA has signed a $1.2 billion contract with Pratt & Whitney Rocketdyne to develop the J-2X engine the U.S. space agency needs to power the upper stages of its Ares 1

crew launch vehicle and Ares 5

heavy-lift rocket.

Pratt & Whitney Rocketdyne of Canoga Park, Calif., has been working on the engine, an updated version of the Apollo-heritage J-2, since June 2006 under a temporary contract awarded without a competition. That contract called for the company to start work on five development versions of the engine followed by two certification engines.

With the new contract, NASA has added one additional development engine to its order, for a total of eight.

“This is huge,” Scott Horowitz, chief of NASA’s Exploration Systems Directorate, said during a July 16

teleconference with reporters about

the new contract. “It’s a big deal that we now have the J-2X contract signed and ready to go because it’s a big piece in getting this rocket ready to fly.”

NASA’s Ares 1

rocket is a two-stage booster designed to launch NASA’s capsule-based space shuttle successor – the Orion Crew Exploration Vehicle – into low-Earth orbit. The larger Ares 5

, meanwhile, is slated to haul heftier payloads into space such as lunar landers and other hardware. Both the Ares 1

and Ares 5

rockets will rely on J-2X engines to power their second stages. NASA plans to award a separate contract down the road for the production of engines for operational missions.

Mike Kynard, NASA’s J-2X program manager, told reporters that buying an additional development engine would allow NASA to begin its testing program sooner and conduct roughly 60 more tests than previously planned. Kynard said some 280 tests are now planned between 2010 and late 2012, when NASA expects to conduct the first test flight of a full-up Ares 1

rocket and an unmanned Orion Crew Exploration Vehicle.

If all goes smoothly, Orion’s first crewed flight could occur as early as September 2013. However, NASA officials readily concede that March 2015 is the more realistic date given the snags that tend to crop up in big development programs like Orion and Ares.

With the announcement of the J-2X contract, NASA moved a step closer to its goal of having the entire Ares 1 rocket under contract by the end of 2007. The Orion prime contract was awarded last August to Denver-based Lockheed Martin Space Systems.

“We needed to press forward so that we could still harvest some of the experience from Apollo,” said Jeff Hanley, NASA’s Constellation program manager for the agency’s new manned spacecraft, adding that J-2X engineers sought input from Apollo program veterans well-versed in the new engine’s J-2 predecessor. “That’s really been a treat, I think, for the team … to be able to go back and interact with that generation.”

Steve Cook, manager of the Exploration Launch Projects Office at NASA’s Marshall Space Flight Center, Huntsville, Ala., said the agency expects to finalize a contract with AlliantTechSystems by mid

August for the development of Ares 1’s solid-rocket-booster-based main stage. Similar to Pratt & Whitney Rocketdyne, AlliantTechSystems got started on its Ares 1

work last year under a temporary $120 million contract signed in late 2005.

By late August, Cook said, NASA should be ready to announce which team it has selected to build the Ares 1

upper stage. That competition is pitting Boeing against an AlliantTechsytems-led team that includes Orion prime contractor Lockheed Martin Space Systems and Pratt & Whitney Rocketdyne. The contract is expected to be worth roughly $900 million.

A separate contract for the rocket’s avionics system, or instrument unit, is slated for award around early December, he said. Five teams are finalizing bids for the contract, which is expected to be worth roughly $400 million. The competing teams are led by BAE Systems, Ball Aerospace and Technologies, Boeing, Honeywell, and Raytheon.

SPACE.com staff writer TariqMalik contributed to this story from New York.