Markus Ortelt

Technological Aspects of Transpiration Cooled Composite Structures for Thrust Chamber Applications

The long-term development of transpiration cooled ceramic rocket thrust chambers at the German Aerospace Center (DLR) currently culminates in designs of self-sustaining fibre reinforced rocket engine chamber structures. This paper explains characteristic issues and potential benefits introduced by this new technology, which seem to be achievable in terms of weight and cost reduction, increased reliability and higher lifetime due to no longer existing thermal cycling sensitivity. The paper furthermore describes design and functional aspects of the chamber, the component manufacturing process and shows some experimental results of test campaigns with respect to structure and material relevance. DLR’s development road map is sketched and the technology readiness level achieved so far is discussed. Nomenclature ISP = specific impulse kd = coefficient of Darcyan permeability kf = coefficient of non-Darcyan (Forchheimer) permeability L = flow length pin = inflow pressure pout = outflow pressure T = temperature v = velocity Δp = pressure loss λ = thermal conductivity (CTC) e = porosity η = dynamic viscosity ρ = density

Transpiration-Cooled Ceramic Thrust Chamber Applicability for High-Thrust Rocket Engines

The development of ceramic rocket engine thrust chambers at the German Aerospace Center (DLR) currently concentrates on designs of self-sustaining, transpiration-cooled, fiber-reinforced ceramic rocket engine chamber structures. This paper discusses characteristic issues and potential benefits introduced by this technology. Achievable benefits are the reduction of weight and manufacturing cost, as well as an increased reliability and higher lifetime due to thermal cycle stability. This paper discusses the current status of DLRs ceramic thrust chamber technology and potential applications for high thrust engines. The test results of DLRs ceramic thrust chamber project KSK are used for a rough approximation of the performance of high thrust applications. Based on the KSK test results an extrapolation is performed. c*-efficiency and geometrical scaling effects are taken into consideration. Due to favorable scaling effects, high thrust applications will profit by all benefits of the discussed technology, while avoiding the most significant performance drawbacks.

Investigations on Fibre Reinforced Combustion Chamber Structures under Effusion Cooled LOX/LH2 Operation

The development of effusion cooled ceramic rocket thrust chambers at the German Aerospace Center (DLR) since more than one decade leads currently to first designs of selfsustaining fibre reinforced chamber structures. Within the German Research Network ‘Propulsion 2010’, a closed co-operation between the DLR and the German Space Propulsion Industry (EADS Astrium Space Transportation), the technology demonstration for a ceramic thrust chamber assembly until the end of 2010 is foreseen. The combination of a porous metal injector, an inner C/C combustion chamber liner, covered by load carrying CFRP, and a fuel cooled CMC nozzle extension is planned to be demonstrated at the European Research and Technology Test Bench P8 at DLR Lampoldshausen, in LOX/LH2 operation within the KSK project (KSK – Keramische Schub-Kammer). The final tests in 2010 will be conducted at 80 mm sub-scale level of inner chamber diameter. First a series of preliminary tests on 50 mm level have been performed in 2008, with the purpose of investigating both functional and structural principles.

Structural Investigations on Cryogenically Operated and Transpiration Cooled Fiber Reinforced Rocket Thrust Chambers

This paper will give a subsumption of the structural implementation of an integrated fiber reinforced rocket thrust chamber design, which took in the meanwhile more than one decade of development effort. Of particular interest in this case is a hybrid design approach showing Ceramic Matrix Composits as high temperature inner liner materials and a covering light weight Carbon Fiber Plastic Housing, whereas these principally different material components are joined by metallic flanges at the front edges in an extensively decoupled design philosophy, excluding compulsive loads as far as possible. In 2010 the long and intensive experimental work led into a test campaign at the European Research and Technology Test Facility P8 at DLR-Lampoldshausen using for the first time the fully integrated chamber design under cryogenic high performance conditions, using LOX/LH2. In this campaign the structural concept could be proved completely under all structurally relevant parameters. With respect to the demonstration of the system efficiency under optimized operational flow parameters a further test campaign early in 2012 had been performed at the recently renewed local P6.1-test bench. The paper discusses predominantly structural design aspects.

Empirical Verification of Effusion Cooled CMC Rocket Thrust Chambers

Thrust chambers are one of the most sensitive components in rocket propulsion systems due to safety and efficiency related to reasonable costs. Competitive space transportation systems ask for such low cost and high sophisticated solutions. A very promising approach in this field is the development of an effusion cooled CMC combustion chamber design, which offers a new perspective on the way to reliable future cryogenic rocket engines. The undoubted advantages of transpiration cooling under the critical view of efficiency, damage tolerance and low cost aspects can be accomplished with a relatively simple and low weight concept using carbon fiber composite materials. In the recent years DLR works on the application of effusion technology. The paper illustrates the empirical development steps accompanied by numerical simulations until a break through in form of the latest high performance tests early in 2005.