Orion/Ares Stack Moves Preliminary Design

"This is a period where you really get to a lot of reality, [where] you compare the allowances you've allocated with the actual components that come out of the preliminary design," says Cleon Lacefield, Lockheed Martin's Orion program manager. "You're not out of the woods until you get to CDR [critical design review], but this allows us to really put a lot of engineering into maintaining where we're at."

In some areas subsystem designs are well understood and can be inserted in Orion with "high confidence," Lacefield says. Those include fans, fan motors, heat exchangers and even the mechanism to deploy the circular solar arrays that give Orion its distinctive appearance in space. Those arrays and their deployment devices are drawn from the Phoenix Mars probe Lockheed Martin built for NASA, which is due to land in the north polar region of the red planet next May.

"There are some others that we're trying to put some real engineering into to make sure we haven't missed anything," Lacefield says, mentioning the fairing panels on the sides of the Orion service module that will be jettisoned after the upper-stage engine ignites to save weight.

Manufacturing already has started at Ares I first-stage prime contractor ATK on building the initial five-segment ground-test version of the four-segment space shuttle solid rocket booster that forms the basis for the stage. The mandrel that will be used to pour propellant for the stage's new forward segment is nearing completion, and other components are underway as well.

The Saturn-heritage J2-X Ares I upper-stage engine remains the pacing item for the whole stack from a technical standpoint. Hot-fire power-pack testing could begin at Stennis Space Center early next month, depending on preliminary cold-flow testing getting underway now. A new test stand is under construction at Stennis to permit high-altitude start tests of the engine. But even with design heritage going back to the 1960s, NASA managers concede, the J2-X will essentially be a new engine.

Overall, though, advances in the computer analysis used to design new vehicles are helping Ares I engineers identify problems earlier in the design cycle. Work remains on track for a four-segment "Ares I-X" flight test with a dummy fifth segment, upper stage and Orion that is also scheduled for April 2009. Like the five-segment ground test that month, the flight test will generate more data for the computers on the complex forces at work as the long, narrow "single-stick" solid/liquid hybrid launcher lifts off.

Across NASA and its contractors, work is already underway on the infrastructure changes that will be needed to accommodate the new vehicles in the post-shuttle era. Nowhere will that be more evident than at Kennedy Space Center, where the final vehicles will be assembled, and where managers already are wrestling with the task of switching launch facilities to test the new vehicle while still flying the old one.

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