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Shuttle remodel. (Power Transmission and Motion Control).

A pair of bellows creates sealed passages between two high-pressure pumps and the Space Shuttle's power head, according to Mike Paytas of Pratt & Whitney in West Palm Beach, Fla. Paytas, project engineering manager for the Space Shuttle's main engine turbopump program, said the turbopumps began delivering liquid oxygen to the shuttle engines in 1995 and liquid hydrogen in 2001. The pumps replaced an earlier design in an effort to increase the number of flights between overhauls. The turbopumps last 10 missions between rebuilds.

The bellows maintain passageways for the gases, while accommodating thermal expansion and isolating the pumps from engine vibration. The machined bellows replace an earlier hydroformed version.

Hydrodyne of Burbank, Calif., machines the bellows from a single piece of metal, according to engineering vice president Jeff Bluen. There are no welds, even at the flanges. Machined bellows open a wider range of material possibilities than either formed or welded bellows can, Bluen explained. Material thickness through the tubular shell or the flat plate sections can be made wider or narrower to account for stress distribution and to be sure that the material stays within its non-yielding levels, he added.

Bluen mentioned another potential application for machined bellows. Because walls lend themselves to tight thickness control, the force that a bellows exerts can be governed precisely as well. Unlike a bolted seal, which pushes against the sealing material hardest under the bolts, a bellows seal exerts the same force around the entire circumference. Its flanges can thus be made lighter, Bluen said, an important consideration in aerospace applications.

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Title Annotation:Product Information
Comment:Shuttle remodel. (Power Transmission and Motion Control).(Product Information)
Author:Sharke, Paul
Publication:Mechanical Engineering-CIME
Article Type:Brief Article
Geographic Code:1USA
Date:Mar 1, 2002
Words:259
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