Foam loss grounds shuttle fleet again
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: July 27, 2005
In a major setback for NASA, senior managers today grounded the shuttle fleet, saying no more missions will be launched until engineers figure out why large, potentially catastrophic pieces of foam insulation broke away from the shuttle Discovery's external fuel tank during launch Tuesday.
"I don't know if that's a month, I don't know if that's three months. We've got a lot of work in front of us to go figure that out."
See pictures of the tank here.
The unexpected problem, coming on the heels of what had appeared to be a triumphant return to space for Discovery and its crew, put a planned September flight by the shuttle Atlantis in clear doubt and raised the possibility of an extended hiatus that would put additional strain on the international space station and along with it, the nation's confidence in NASA.
The largest pieces of foam did not strike Discovery and engineers believe the ship's seven-member crew will be able to safely return to Earth Aug. 7 after a long-awaited mission to deliver supplies and equipment to the space station. If all goes well, commander Eileen Collins will guide Discovery to a linkup with the unfinished $30 billion outpost early Thursday.
But the foam problem took the luster off an otherwise successful mission, and for good reason. Deputy shuttle program manager Wayne Hale said if the largest piece of debris had fallen off earlier, while Discovery was still in the lower reaches of the atmosphere, "we think this would have been really bad. So it's not acceptable, OK?"
Discovery blasted off from the Kennedy Space Center at 10:39 a.m. Tuesday, two-and-a-half years after Columbia disintegrated during re-entry. The disaster was caused by damage to the ship's left wing that resulted from the impact of external tank foam insulation during launch 16 days earlier.
NASA's top priority in the wake of the accident - and the No. 1 recommendation of the Columbia Accident Investigation Board - was to redesign the way the foam is applied to the tank to minimize so-called foam shedding. Engineers were confident Discovery's tank would shed nothing larger than a marshmallow, repeatedly stating their belief that the new tanks were the safest ever built.
But during Discovery's climb to space, a few seconds after the ship's solid-fuel boosters separated two minutes and five seconds into flight, a relatively large, pillow-size piece of foam ripped away from an aerodynamic ramp intended to prevent turbulent airflow around cable trays and pressurization lines.
A new camera mounted on the external tank to monitor the tank's performance showed the debris lifting off and quickly tumbling away in the thin, supersonic airflow. Earlier, part of a heat shield tile near the nose landing gear door cracked off and fell away. That incident is still under study, but it appears relatively minor.
The tank debris passed under the shuttle's right wing and did not appear to come close to actually striking the orbiter. But the size of the yard-long piece of debris was a shock.
In addition, camera footage shot by Discovery's crew after the tank was jettisoned showed two other relatively large divots in the foam near the area where two struts held the shuttle's nose to the tank.
"We saw a couple of divots in areas that frankly are not satisfactory to us," Hale said. "We spent a lot of time working on what we call the liquid hydrogen interface ring, the LH2 interface, to make sure we would not loose pieces of foam and in fact, we see about a six- or seven-inch piece of foam that came off right there at that interface, which is unsatisfactory and we've got to work on that."
In the aftermath of Columbia, engineers discussed the possibility of eliminating the so-called protuberance air load - PAL - ramp, a long, hand-applied foam dam used to improve the tank's aerodynamics. Here is a description from NASA's STS-114 press kit:
"Our expectations when we went into this flight that we wouldn't have an unexpected debris event," Parsons said. "The program throughout the last two and a half years, we reviewed many areas on this tank and ways we can improve that. The PAL ramp was one of those areas we reviewed, whether we should make modifications to that or whether we had enough technical data that we felt it was OK to fly as is.
"There were some concerns about this ramp, that is a large piece of foam. So the community was very diligent about looking at this. We did realize that eventually one day we needed to put together a program to remove this PAL ramp if at all possible. But at the time, we didn't have enough data where we could technically do that and be safe.
"In the end, we had enough data to show we had had very few problems with the PAL ramp and we decided it was safe to fly as is. Obviously, with the event that we've had, we were wrong. ... We did not expect the PAL ramp to have the issue that it had, but it did."
Parsons said it likely will take engineers a fair amount of time to understand what caused the foam to separate and to come up with a fix.
"This is a test flight," he said. "We went off to take a good look at this vehicle and see how it would perform. And unfortunately, it didn't perform as well as we'd like it to perform. I can't say what the impact of this is until we get some good evaluation of this and try to understand what caused this to happen.
"We are going to go through and do a thorough evaluation and then we'll determine when it's safe to fly. Obviously, we can't fly with PAL ramps the size of this ramp coming off the way it did. I mean, obviously, we have to go fix this."
While the shuttle fleet will remain grounded while engineers troubleshoot the latest problem, Parsons said the nation should not lose confidence in NASA or the space shuttle.
"We think this vehicle is safe," Parsons said. "We think we can fly this vehicle and we think we can make this vehicle safe for the next flight. We feel very, very confident in our ability to make this vehicle safe."
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