With a lot of scrubbing and starting over behind them, engineers working on NASA' Orion crew exploration vehicle and its Ares I launcher are moving into detailed design on a stack they believe can deliver its targeted payload to orbit with thousands of pounds to spare.
On the Orion capsule, prime contractor Lockheed Martin's engineers are beginning to flesh out the latest vehicle concept for preliminary design review next September. The Ares I program is moving into early production on the first of its five-segment shuttle-derived solid-fuel first stages, for a static test on the ground in April 2009, and settling on the advanced tooling that will be used to build the cryogenic upper stage at the Michoud Assembly Facility in New Orleans.
Technical issues remain open across the stack, including how the Orion will land and how to meld the powerful solid-fuel first stage and capsule. But engineering managers across the Orion/Ares I organizations consider those issues typical of a spacecraft at this relatively early stage of development, and solvable. After two months of reviews and top-level briefings, their bosses at NASA headquarters agree.
"It's very interactive" says Caris A. (Skip) Hatfield, who shepherded the Orion through its weight scrub as program manager. "It's not like you can create a launch vehicle and life is good, without doing any additional assessment. Issues come up as the design matures. And as load cases become more clear, we have to go back and look at them jointly. Changes we make affect the launch vehicle. Changes the launch vehicle makes affect us. But overall we're working very closely together to make sure we mitigate all those, and at this point there are no showstoppers."
But while senior managers consider the technical issues within bounds, money remains the ultimate pacing item for a U.S. return to human spaceflight after the shuttle is retired in 2010. Right now the best estimate for Orion's first docking at the International Space Station is March 2015, at current funding levels.
"If we had all the money we could use, we could bring Ares and Orion back to fall 2013, notionally September," says Administrator Michael Griffin. "Now, that would require a total of about $2 billion spread over the next three or four years. Beyond that, we can't do it no matter how much money you give us."
Overall, Griffin says, the men and women developing the vehicles are doing "incredibly well." Mass is always a problem in spacecraft development, he notes, and the Orion and Ares I programs have handled it while retaining a collective margin for growth of more than 20% reflecting the latest mass margins for missions to the ISS and the Moon.
"We need to focus on kilograms from day one until launch, but with ample mass margin across the vehicle we can close the lunar architecture today, and I expect it will only get better," Griffin says.
Getting there wasn't easy for the Orion program, which has just finished a top-to-bottom weight scrub that essentially involved starting over . Now, Lockheed Martin can tackle finding out what the vehicle actually weighs.
"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.