Description: Hypersonic aircraft, especially reusable hypersonic aircraft, require significant advancements in high temperature materials because of the extreme temperatures resulting from frictional heating. One aspect of this problem is making seals that can function through a very large temperature range, perhaps up to 1000 °C or higher. Metallic springs essentially lose their ability to function at 600 °C or less. Ceramic springs, principally made of silicon nitride, can function throughout that temperature range, but lack the strength required for most applications. They also undergo very limited deformation before failure. TDA has been improving the feedstocks and developing a highly automated process for manufacturing ceramic springs. During this project, TDA will further the development of our ceramic springs in three ways: 1) Establish methods for rapid, non-destructive quality control; 2) Using the materials properties of the ceramic that were determined during Phase II, optimize the physical dimensions of the springs; and 3) Conduct high heat rate testing of the springs at Southern Research Institute.

Benefits: Ceramic springs are primarily being developed for preloading of high temperatures seals in scramjet engines. However, high temperature – capable springs could also solve problems in the control surface and/or leading edge thermal protection system. These needs are particularly acute for re-usable hypersonic transports, including the descendants of the National Aerospace Plane. High-temperature springs with sufficient strength could also potentially be used to create a seal between the hot structure and the back shell of (re-)entry vehicles.

The most obvious application is in the seals of single-use hypersonic weapon systems, since they have very similar needs to NASA hypersonic systems. Ceramic springs that allow high(er) temperature seals to be made between smaller, simpler pieces of tooling can reduce manufacturing costs by obviating the need for larger, more complex tooling.