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[b]No stage re-contact, but two parachutes failed[/b]
NASA's Ares I-X mission manager Bob Ess briefed the media on Friday, providing more details about the performance of the test flight.
"Everything went really, really well. In fact, everything flew just right down the middle of the pipe," commented Ess. "Everyone's still pretty ecstatic. It just showed we got our models right in all areas, the ascent part of it, the (guidance and control) part of it, the flexible body interaction, all the really hard stuff."
Ess however did acknowledge a problem with two of the three main parachutes used to recover the first stage. Divers, working to salvage the booster from the ocean, discovered a large dent along the side of one of its lower segments.
"There was an indication that we had a parachute problem," said Ess, explaining that only one of the three 150-foot parachutes inflated fully. Of the other two, one failed to deploy and the other only partially inflated.
The result was a harder than expected splashdown, but the damage to the booster was not of concern to Ess' team.
"We don't plan on reusing [the stage]. We got the data and a good test of the parachutes," he said, noting that the "parachute guys were 'ecstatic'" about the flight.
Ess said they expect to know the cause of the two failed parachutes by next week.
"If it was something to do with the separation event and there was scorching, that gives you some indications," he said. "We don't think that's the case."
Speaking of stage separation, Ess said that his comment after the launch that they had seen something "different" than what their computer models had predicted was wrong.
"Two days ago at the press conference I used the phrase... 'a little different', recalled Ess. "We went back and looked at all the 5,000 disperse cases that we ran and we found thousands of them that matched what we saw. So my comments were incorrect when I said 'a little different.'"
"In fact, we have animations that were done a couple of months ago showing almost exactly what you would see in the video," he added.
The two stages tumbling had led some to believe that the first stage may have struck the upper stage upon separation.
"We looked at the video and multiple video views and we did not see any re-contact between the upper stage and the first stage," said Ess.
Instead, given the dispersion of weight on the vehicle, Ess said that the tumble should have and was expected.
"There's about 130,000 pounds of ballast total; 100,000 of it is at the very back-end of the upper stage that simulates where the liquid oxygen would be for Ares I. There's about 30,000 pounds further forward in the upper stage to simulate where the the liquid hydrogen would be."
"So the center of gravity is very far aft in this thing once it's by itself and the center of pressure is more towards the middle... so it's inherently unstable," he said. "So with about 90 or so pounds per square foot of dynamic pressure and an unstable vehicle, it's no wonder the simulations showed just what we saw, that once you separate, there's nothing to control it."
"As a reminder, for Ares I, there's an attitude control system on it. So as soon as you separate, there are attitude control motors that will keep the upper stage where it needs to be and then the J-2 engine will kick off as well and we'll have active control. So that is something that's very, very different between I-X and Ares I is the upper stage," Ess said.
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Ultimate Bulletin Board Version 5.47a
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