Compression Force Response and Leak Rate Quantiflcation of Candidate Static Silicone Space Seals

In order to successfully mate two pressurized vehicles or structures in space, advanced seals are required at the interface to prevent the escape of breathable air. The National Aeronautics and Space Administration (NASA) has been developing a new main interface seal to be used on current and future docking mechanisms for space exploration missions. The assembly is mounted to the surface of the docking system forming a face seal. One of the candidate main interface seal designs is a composite assembly of four silicone elastomer seal bulbs vacuum molded into an aluminum retainer. Two of the four seals are dynamic and they interact with the mating counter-face from the adjoining spacecraft. The other two seals are static and they prevent gas from leaking between the seal assembly and the pressure vessel to which it is attached. This paper investigated three candidate static seal designs across a range of temperatures to determine their respective performance. The force required to compress the static seals was quantied at temperatures between 75 C and 125 C. In addition, the paper also demonstrated the sealing capabilities of the candidate material and designs by quantifying the leak rates through the seal when tested in a simulated operational environment. The test specimens used in this study were nearly identical in design and varied only in seal bulb width. It was found that the force required to fully compress the static seals, in general, increased with the test temperature, as well as with the seal bulb width. A force of 30:0 lb/in. was required at 125 C to achieve full compression of the widest bulb. Similarly, the leak rate values, measured at a range of temperatures from 50 C to 50 C, were found to increase with test temperature, but also decrease with increasing seal bulb width. The highest leak rate of 9:82 10 7 lbmair/day/in. was measured at 50 C for the narrowest seal bulb.