Monday, October 6, 2003

Marshall redesign efforts set to raise the bar on safety: "A two-foot-long explosive bolt and its holding assembly, which can be described as the linchpin of the space shuttle, is being reworked by Marshall Space Flight Center engineers to improve safety margins so NASA can return the shuttle to flight. ...

"The explosive bolts keep the 149-foot-long solid rocket boosters pinned to the 184-foot-long external fuel tank. They also support the 4.5 million-pound shuttle on the ground and endure 3.3 million pounds of rocket thrust from each booster while the shuttle flies.

"When the 70-pound bolt's job is done, it is blown apart, releasing the boosters to be parachuted back to Earth. The bolt pieces blow back into a bolt-catcher assembly. The catcher, filled with an alloy fashioned into a honeycomb, slows the bolt, which is traveling about 80 mph when it is blown, and keeps pieces of it from hitting the fuel tank or booster. Tests show there is a possibility the bolt catcher could fail. ...

"Every bolt catcher we fired the bolt into never failed during a launch," [David Martin, head of Marshall's Solid Rocket Booster Program office,] said. "We found a lack of (safety) margins, but we never found a situation where it failed. But you never know how close you are to having one fail. The hardware appears to have worked very well, but if you don't have the margins you want, you go back to a redesign."

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