Thursday, March 16, 2000

Flawed seals in Atlantis Shuttle's engine to be replace before launch By MARCIA DUNN -- The Associated Press

Space shuttle Atlantis CAPE CANAVERAL, Fla. (AP) -- In another embarrassing mix-up for NASA, flawed engine seals that should have been thrown away are believed to be in space shuttle Atlantis.

It's the second time in a few months that defective seals have turned up on a space shuttle instead of in the trash.

Two seals intended for the garbage are apparently in one of Atlantis' main engines, chief engineer Len Worlund said Wednesday. As a result, NASA will replace that engine before the shuttle blasts off next month with supplies for the international space station.

Worlund said the flawed seals are probably safe to fly, but as a precaution will be removed along with the rest of the engine. The work is not expected to delay Atlantis' launch, targeted for around April 17.

"Since we know that the seals that were delivered to us, there's a high probability that there is a defect in that part ... we think it's prudent for us to go off and take those out," he said.

The problem with the seals arose in late January, when NASA discovered that a rejected seal ended up in an engine that helped propel Discovery to orbit in December.

The defective seal had, in fact, flown on three shuttle launches, but went unnoticed until the nickel plating separated in one spot and was rubbed by turbine blades. The damage occurred during Discovery's liftoff on the Hubble Space Telescope repair mission.

The seals -- made of six 6-inch segments located in the main engine fuel turbopumps -- help direct hot gas into the turbine blades to increase performance. If a seal should fail, the engine could shut down, forcing an emergency landing.

NASA proceeded with Endeavour's launch in February, even though engineers could not verify that all its seals were certified for flight. Managers said the likelihood of more defective seals turning up was very low.

It was in the course of verifying all of its approximately 100 seal segments that NASA discovered the problem with two aboard Atlantis, said Worlund. All the other pieces were found to be good, including those that flew on Endeavour last month.

Records showed that the seal manufacturer had scrapped two pieces way back in the late 1980s because of a defect in the metal.

To Worlund and everyone else's amazement, the two junked seal segments were still around. But they checked out fine, which meant that the bad pieces were sent to NASA as flight units, Worlund said. The paperwork showed those two pieces to be on Atlantis.

"Since this vendor's discard pile contains two good parts, he must have sent us two bad parts," Worlund said. He blamed it on mislabeling.

The two defective seal segments already have flown once in space, during Discovery's launch in October 1998 with John Glenn.

Obviously, Worlund and other shuttle managers are not pleased.

"What it really says, to us, is that we have an issue that we have to go off and work," Worlund said. He quickly noted: "It doesn't happen very often."

http://www.canoe.ca/CNEWSSpace0003/16_atlantis.html

-- Martin Thompson (mthom1927@aol.com), March 16, 2000