The Space Transportation Systems group at the Chair of Space Systems at Technische Universität Dresden, in Dresden, Germany, has reported a breakthrough in space technology. As part of the ASPIRER project funded by the European Space Agency (ESA) researchers successfully conducted what is believed to be the world’s first hot gas test of an additively manufactured aerospike engine using a more sustainable fuel combination of highly concentrated hydrogen peroxide and kerosene. The project is being carried out in cooperation with the Fraunhofer Institute for Material and Beam Technology IWS, ArianeGroup, and the Warsaw Institute of Aviation.
Aerospike engines save a significant amount of fuel and score highly in terms of efficiency compared to conventional rocket engines with bell nozzles. However, they are also more complex and difficult to control.
During the test campaign, the engine operated in both monopropellant and bi-propellant modes. The monopropellant mode involves hydrogen peroxide being decomposed by an integrated chemical catalyst at high temperatures; this results in only water vapour and oxygen remaining as end products, making the fuel a more environmentally friendly alternative to conventional fuels.
In contrast, in the bi-propellant mode, kerosene is injected, causing the mixture to ignite spontaneously without the need for additional mechanical components. The engine is designed for an operating pressure of 20 bar and delivers 6 kilonewtons of thrust at full load. One kilonewton is roughly equivalent to the weight of a mass of 100 kilograms.
The main challenge with aerospike engines is cooling. These engines can only be designed and manufactured effectively through the use of modern Additive Manufacturing processes such as Laser Powder Bed Fusion (PBF-LB). The scientists also successfully tested a newly developed, heat-resistant ceramic coating for the combustion chamber elements.
Due to their lightweight and compact design, aerospike engines are suitable for various mission scenarios, such as launch vehicles, expeditions to Mars and Saturn’s moon Titan, on lunar modules. Especially in the latter application scenario, aerospike engines could represent a more sustainable alternative to conventional, hydrazine-based engines, the use of which is viewed critically due to health and environmental risks. The unique shape of the engines also allows for more flexibility in design, enabling lunar modules to be built flatter. This simplifies loading and unloading by astronauts and the deployment of rovers.
The Institute of Aerospace Engineering is examining the feasibility of alternative methods for controlling engines and exploring their advantages over conventional systems. The long-term goal is to address the low level of technological maturity and the associated uncertainties related to aerospike engines.
