A mechanical device has been developed for applying an adhesive patch, from the outside, to the wall of a spacecraft module that has lost pressure because of penetration by a meteoroid or a piece of orbital debris. This device will make it possible to seal and re-pressurize the affected module during space flight. Devices identical or similar to this one might also prove useful in the repair of other pressurized bodies and similar objects, including gas and oil pipes and ship hulls, for example.
The device includes a patch frame, which is moved toward the hole to be patched from the exterior side of the damaged wall by use of handles. The device also includes a flexible outer sealing ring that becomes molded against the wall. Another component of the device is a probe that includes a right-hand-threaded shank and is equipped with an assembly of spring-loaded sprags at its penetrating tip.
The probe is inserted in the hole. When the probe has passed through the hole in the wall to the interior side, the sprags spring outward. Next, the probe is turned counterclockwise to draw the sprag assembly toward the patch frame; as a result, the sprags are forced against the inside edge of the hole in the wall. As the probe continues to turn, the sprag assembly stays in place and the flexible outer sealing ring on the patch frame becomes pushed against the wall on the outside; this action creates a seal between the patch frame and the wall.
Next, the volume enclosed by the patch frame, wall, and outer sealing ring (called the "patch body volume" for short) is filled with a liquid adhesive sealant material to create a permanent seal and strong adhesion between the patch and the wall. The adhesive sealant is injected into the patch body volume through quick-connect/quick-disconnect fittings that are similar to automotive grease fittings and that are located in several positions on the patch frame. Although the patch is not a substitute for the loss of structural strength caused by the penetration, the adhesive bond between the patch frame and the wall is strengthened by an adhesive-interface plate on the patch frame: as the adhesive flows into the patch body volume, it flows onto and around hooks that protrude from the adhesive-interface plate. Once the adhesive hardens, the patch is held in place against the tensile loads induced by re-pressurization of the interior of the spacecraft module, pipeline, or other volume enclosed by the wall.
Success in the use of the patching device does not depend on the prior installation of structural fastening devices on the wall to be repaired. Another advantage of this device is that its flexible outer sealing ring makes it adaptable to a variety of external wall configurations, structures, and radii.
This work was done by Joel Williamsen, Kathryn Horton, and Bruce Weddendorf of Marshall Space Flight Center.
This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to
MSFC Commercialization Assistance Lead
Refer to MFS-31173.