“Black Engine” is the name of a transpiration-cooled ceramic thrust chamber technology developed at DLR Institut of Structures and Design. Taking advantage of the favorable material properties of ceramic matrix composites (CMC), the combustion chamber is cooled by transpiration of the fuel through the combustion chamber wall. This highly efficient cooling method with its low pressure requirement in contrast to conventional regenerative cooling, combined with the high temperature resistance of the material, potentially results in a very efficient overall system.
Video: Black Engine
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Video: Black Engine
“Black Engine” is the name of a transpiration-cooled ceramic thrust chamber technology developed at DLR Institut of Structures and Design. Taking advantage of the favorable material properties of ceramic matrix composites (CMC), the combustion chamber is cooled by transpiration of the fuel through the combustion chamber wall. This highly efficient cooling method with its low pressure requirement in contrast to conventional regenerative cooling, combined with the high temperature resistance of the material, potentially results in a very efficient overall system.
The thrust chamber - consisting of the injection head, combustion chamber and expansion nozzle - as part of a rocket engine is one of the most thermally and mechanically stressed parts of a rocket and therefore has a major influence on the performance, reliability and costs of a launcher system. The combination of modern composite materials and innovative design concepts and cooling methods as part of the "Black Engine" technology promises advantages in terms of simplified production, reliability and reusability.
The name "Black Engine" is derived from the predominantly black carbon fibres used to date for the composite components in the hybrid design:
CFRP for the outer supporting shell
porous, fibre-reinforced ceramic for the inner combustion chamber liner, and
dense CMCs (ceramic matrix composites) for the supersonic expansion nozzle.
Adapted to the material properties of the fibre-reinforced ceramic, the combustion chamber is cooled by transpiration of the fuel through the combustion chamber wall. For this purpose, part of the operating media (usually fuel) is used for cooling instead of combustion. However, this extremely efficient cooling method, together with the low pressure loss in the overall cycle compared to conventional regenerative cooling and the high temperature resistance of the material, results in a potentially very efficient engine system. The modular and load-decoupled structural design of the combustion chamber also ensures a significant reduction in structural fatigue. The CFRP support shell is designed to be fatigue-resistant to absorb the mechanical vibration and pressure loads, while the CMC inner liner is designed independently of this to balance the thermal loads. Coupled with the extremely low thermal expansion of the materials used, the Black Engine can therefore be expected to offer a significantly increased level of durability, reliability and reusability. The modularity of the structural design also promises favourable simplifications in production.
The multi-shell CMC expansion nozzle is cooled using the fuel film transpired through the porous inner wall and no longer requires additional active cooling due to its high temperature resistance in the supersonic section. This significant system simplification further increases the safety and efficiency of the entire rocket engine system by reducing the requirements on the cooling system and the general complexity of the integrated thrust chamber design.
In previous developments, the functionality of the technology in combustion chamber operation with the combustion of liquid hydrogen and liquid oxygen has been demonstrated in tests of up to 3 tonnes of thrust and test durations of up to 120 seconds, e.g. at the European Research and Technology Test Bed P8 at DLR-Lampoldshausen.
Future development goals for the technology are the transfer of the technology to the oxidiser/propellant combination LOX/LCH4 as well as general further development within the scope of the potential still to be expected for increasing efficiency and reusability.
