c∗-Efficiency evaluation of transpiration cooled ceramic combustion chambers

Achievable benefits of the transpiration cooled ceramic thrust chamber are the reduction of weight and manufacturing cost, as well as an increased reliability and higher lifetime due to thermal cycle stability. The transpiration cooling principle however reduces the engine performance. In order to evaluate the performance losses a c ∗ -analysis is performed. Due to the transpiration cooling the characteristic velocity decreases with increasing coolant ratio. The goal of the chamber development is therefore to minimize the required coolant mass flow. The paper discusses the test specimen set up for the ceramic thrust chamber tests. Chamber operating parameters are listed. The paper discusses the impact of transpiration cooling on the calculated c ∗ efficiency. The evaluation is based on test results with the ceramic combustion chamber conducted in four separate test campaigns between 2008 and 2012.