A modification of a pressure-actuated joint has been proposed to improve its pressure actuation in such a manner as to reduce the potential for leakage of the pressurizing fluid. The specific joint for which the modification is proposed is a field joint in a reusable solid-fuel rocket motor (RSRM), in which the pressurizing fluid is a mixture of hot combustion gases. The proposed modification could also be applicable to other pressure- actuated joints of similar configuration.

The Modified RSRM Field Joint would be the same as the unmodified one, except for the introduction of the pockets.

The RSRM field joint (see figure) includes a pressure- actuated member denoted the J-leg, which is part of a body of insulation. A pressure- sensitive adhesive (PSA) is used to bond the sealing surface of the J-leg to the sealing surface of another body of insulation. The pressure actuation is supposed to push these two sealing surfaces together. However, experience with the joint indicates that it may not behave as a truly pressure-actuated system.

The modified version of the joint would be the same as the unmodified version, except that pockets of empty volume would be introduced into the body against which the J-leg is pressed. The size, shape, and orientation of the pockets would be such upon the application of pressure to the hot-gas side of the J-leg, the volumes of the pockets would not change significantly and hence the pressures in the pockets, would not change significantly; the net result would be that the pockets would support the buildup of enough differential pressure across the J-leg so that the joint would behave more nearly like a truly pressure-actuated system.

The breakup of the empty volume into multiple pockets would counteract the tendency toward leakage that would be incurred by introducing a single larger pocket. In the unlikely event that a gas path penetrated the joint, only one pocket would be compromised, while the others would continue to maintain the differential pressure needed for pressure actuation.

This work was done by John R. McGuire of Thiokol Propulsion for Marshall Space Flight Center.

Title to this invention has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457(f)} to Thiokol Propulsion. Inquiries concerning licenses for its commercial development should be addressed to

Thiokol Propulsion
PO Box 707
Brigham City, UT 84302-0707
Tel. No.: (435) 863-3511
Fax No.: (435) 863-2234

Refer to MFS-31652, volume and number of this NASA Tech Briefs issue, and the page number.

NASA Tech Briefs Magazine

This article first appeared in the April, 2003 issue of NASA Tech Briefs Magazine.

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