IFAs have occurred on every Space Shuttle flight and Boeing, as the original manufacturer of the Orbiters, often has the responsibility of investigating and resolving them as part of its contract with United Space Alliance.

Tim Reith, Boeing Orbiter Integration manager and deputy chief engineer, says although it's not unusual to have IFAs on every flight, they must be fully understood before the next flight.

"When we have an unexpected result, we'll investigate and troubleshoot for the given conditions on whether the hardware acted properly," said Reith.

"If the problem can be isolated to a specific piece of hardware, then it will be replaced with a spare. For situations deemed "unexplained" because the root cause cannot be determined, or if we can't recreate an IFA, we do a thorough assessment of all the things that could happen and determine if we have sufficient redundancy and work-arounds and measure the level of risk.". In unexplained cases NASA makes the ultimate decision to accept that risk.

Following the Columbia accident, NASA rewrote the definition of IFAs and, as a result, more were listed on the last flight.

The process of troubleshooting an IFA begins as soon as Boeing engineers learn about the problem. "We'll start looking at it right away to determine the impact to the mission," said Reith. "For many of the problems, if there is not a big impact we can often wait until the Shuttle lands to troubleshoot."

All IFAs on the last flight had either a workaround or could be accepted as is with no safety impact.

Troubleshooting usually begins with engineers trying to recreate the problems on the ground to isolate and narrow down the problem further. Problem resolution teams define troubleshooting procedures to get a better understanding of the failure.

"If we are successful, then the component is replaced and we go into an investigative phase to figure out why the component failed," said Reith. "Traveling to space is a complicated engineering marvel and we do all we can to make it as safe as possible. Working with NASA and USA on IFAs is just one example of a robust process designed into the Shuttle program," added Reith.

Boeing Engineers Assist NASA In Shuttle Tile Work
Houston (SPX) Jan 26 - Boeing engineers, working closely with United Space Alliance (USA) and NASA, have found a way to prevent gap fillers, thin spacers between the Space Shuttle's heat resistant tiles, from protruding from the belly of the Orbiter.

On the last Shuttle mission, two gap fillers were protruding about an inch between the tiles and had to be removed during a spacewalk when analysis showed it could cause increased heating on the Thermal Protection System (TPS) during reentry into the Earth's atmosphere.

Determining what caused the gap fillers to come out took a little detective work by an integrated team of Boeing, NASA and USA engineers. "The first thing we looked at was the installation process," said Dan Bell, Boeing TPS subsystem manager. There were multiple possible contributing causes why some of the gap fillers were found with various protrusions after the last flight. The cause was narrowed down to the installation process and a new method was developed.

Work is underway on the vehicles to remove those gap fillers. NASA expects to have them removed and replaced on both Atlantis and Discovery in the priority one region (subjected to higher heating) before the next shuttle flight.

"We ended up saving about 15 percent of those gap fillers that were installed with the old process, while all others in our first priority region were replaced," said Bell. About 3,000 gap fillers will be replaced in the priority one area. Bell says all gap fillers will be eventually checked and replaced if needed.

"These changes have made all the difference. It has been a real success," Bell said.

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