The Ares I rocket will consist of a single five-segment solid-fueled rocket (for the first stage) and a single liquid-fueled rocket powered by a J-2X engine (for the second stage).

NASA awarded PWR, a company with United Technologies, the cost-plus $1.2 billion contract on a sole-source basis—meaning that no other company was able to meet the contract requirements.

The J-2X rocket engine is based from the J-2 rocket, which was used for the second-stage of the Saturn IB and Saturn V rockets (which lifted the Apollo capsules into Earth orbit for their eventual trip to the Moon) and the J-2S rocket, which was developed and tested in the 1970s but never flown.

Although the J-2X rocket originated from a 40-year-old J-2 rocket, just about all of its parts have incorporated new technologies and various new composite materials not available to the rocket designers in the Apollo era. Consequently, the new rocket will be able to perform more reliably and much more powerfully than its predecessor based on these high-tech improvements.

According to Aviation Week, the J-2X cryogenic main engine, which uses liquid-oxygen and liquid-hydrogen fuels, will have 294,000 pounds of thrust (about 60,000 pounds more than the J-2s used with Apollo) and a specific impulse (or, thrust per unit weight of propellant per unit time) of 448 seconds.

The over 15-foot tall, 5,450-pound engine will have the ability to re-start once turned off. It will be turned on for the first time at about 30 miles in height into its mission—after the reusable first-stage solid rocket booster (SRB) rocket has separated away. The J-2X will then power the Orion spacecraft, which will hold up to six astronauts, into an elliptical, low-Earth orbit—about 85 miles in altitude.

When the crewmembers are ready to travel to the Moon or Mars, the engine is designed to start up again to take the Orion spacecraft (formally called the Orion Crew Exploration Vehicle) out of Earth orbit and onto a lunar or martian trajectory.

The contact awarded to PWR, which goes through December 2012, entails building eight of the J-2X rocket engines—in which six of them will be developmental engines and the final two will be test engines. The first engine ground test, which will be performed at the Stennis Space Center in Mississippi, is scheduled for March 2010. Then, from March 2010 to late 2012, NASA will perform around 279 additional tests on the engines.

Once these engine tests are completed successfully, the first test flight is scheduled in September 2012. NASA is tentatively scheduling the first manned flight in the September-October 2013 time frame.

The J-2X engines, which have been under pre-design development at PWR since June 2006, will be built at its Desoto Park manufacturing facility in Canoga Park, California, which is in southern part of the state.

The J-2X engines will also be used for the second stage of the Ares V, a rocket that will be used to carry heavy amounts of cargo, equipment, and various space exploration payloads into space. Ares V will use, for its first stage, five RS-68 liquid-oxygen/liquid-hydrogen engines on an external tank (similar to but larger than the ones used for the space shuttles) and two five-segment solid rocket boosters (like the SRBs used for the space shuttles but with one additional segment).

By the end of 2007, NASA is expecting to have contacts awarded on all aspects of the Ares I launch vehicle. Besides other major components, Alliant Tech Systems (ATK) Thiokol is already working on the pre-development design of the solid rocket boosters for the first-stage of Ares I.

For addition information on the Constellation program, Orion spacecraft, and Ares I and Ares V launch vehicles, go to NASA website at: http://www.nasa.gov/mission_pages/constellation/main/index.html. It includes a story on the J2-X engine and the PWR contract.

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