AFRL Thermal Protection System Tests Validate Tile Concepts

  • Published
  • By Air Vehicles Directorate
  • AFRL/VA
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  AFRL recently conducted a series of thermal protection system (TPS) tests aimed at determining the performance and durability of various TPS tile concepts under extreme environmental conditions. Researchers are developing concepts wherein various ceramic matrix composite (CMC) materials are wrapped around silica-based insulating tiles to increase tile durability and decrease maintenance requirements. Researchers conducted micrometeoroid orbital damage (MMOD) testing at the University of Dayton (Ohio), evaluating oxide- and nonoxide-CMC-wrapped tiles in order to determine which variation performed best under projectile impacts of 7 km/sec. They performed a second set of tests in AFRL's Combined-Environment Acoustic Chamber (CEAC), evaluating the performance of the similarly wrapped tiles under simulated launch and reentry thermal and acoustic conditions.

The MMOD tests revealed that high-density (14 lb/ft3) tiles with an oxide CMC wrap or a carbon silicon carbide (C/SiC) wrap performed best; in both variations, the tile wrapping was totally shattered but the base plate (representing the surface of the vehicle skin) was completely undamaged. As a baseline measurement, the researchers also tested unwrapped tiles, similar to some of those used on the space shuttle. These tiles failed to provide adequate damage protection, leaving a 1 in. hole in the base plate. All wrapped tiles that were tested outperformed the baseline (unwrapped) tiles.

During CEAC testing, researchers subjected an array of eight wrapped tiles to thermal conditions ranging from 800°F to 2300°F and acoustic levels up to 165 dB. The array included a single unwrapped tile (which served as a control), two C/SiC-wrapped tiles, and five oxide CMC tiles. Test results showed that the oxide CMC tiles performed best, experiencing no delamination or loss of tile faces.

Overall results of the test series indicate that oxide-CMC-wrapped tiles offer superior performance under all simulated environmental conditions. CMC-wrapped tiles represent an attractive option for TPS components because they provide an outer covering that is extremely durable and a foam interior that is very lightweight. Once the data from this test series has been compiled into a final report, scientists will use it for ongoing TPS research. Ultimately, the project's goal is to offer a durable, low-maintenance TPS concept for future reentry vehicles.