Top: L75 flow schematic. A Thrust Chamber Assembly (TCA) employs a regenerative combustion chamber and dump-cooled nozzle extension, both cooled by the fuel. The turbo pump assembly (TPA) comprises an oxidizer pump, a fuel pump and a supersonic axial-flow turbine with partial admission, all assembled on a single shaft. Combustion gases from a LOX-ethanol gas generator (GG) feed the turbine. The main propellant valves have pyrotechnical actuation, and the two regulation valves are servo-actuated. Pyrotechnic igniters are used in the TCA and the GG. A pyrotechnic gas generator provides spin start for the turbo pump. Bottom: 3D rendering of the L75. Soares de Almeida et al. (2016) Click to enlarge.

In order to find the optimum technology for the propulsion of a future German-Brazilian rocket, two injection heads based on different concepts were developed in parallel. In this first series, we have achieved all our major test objectives. A total of 42 ignitions were successfully carried out over a period of 20 days. During these tests, we were able to closely analyze, among other things, the ignition behavior and stability of the system during ignition and start-up of the thrust chamber. From this we have gained important insights for further engine development.

—Lysan Pfützenreuter, project manager at the DLR Space Administration

The L75 thrust chamber has three main sub-assemblies: the injection head, the cavity ring and the combustion chamber. For testing, the three su-assemblies are bolted together, allowing for easy exchange of combustion chambers and injection heads. Soares de Almeida et al. (2016) Click to enlarge.

The tests took place at the P8 test facility of the DLR Institute of Space Propulsion at the Lampoldshausen site between July and December 2016.

The two injection heads differ in how the fuel is sprayed into the combustion chamber and mixed. One system was developed by the Instituto de Aeronáutica e Espaço (IAE) in Brazil; the other developed and built in Germany by Airbus Safran Launchers as part of the SALSA project (system design of an alcohol LOX propulsion as a substitute for storable fuels).

The new technology makes it possible to use ethanol as fuel. Ethanol, like methane, is being considered as a greener alternative that is more environmentally friendly and has less adverse health effects than the hydrazine compounds generally used for space travel. In addition to these positive effects, these new fuels can also significantly reduce the cost of space travel, since the cost for safe storage and handling of these substances is significantly lower than that for hydrazine.

In Europe, how long hydrazine will continue to be approved as a fuel under the REACH regulation (Registration, Evaluation, Authorization and Restriction of Chemicals) is questionable. This European Union regulation has been controlling the authorization and use of chemical substances since it came into force in 2007.

In Europe, there is only one facility for testing engine components for orbital rockets—i.e. rockets that can transport a payload into orbit—with ethanol fuel: the P8 test facility at the DLR site in Lampoldshausen.

The test facility had already been extended with a high-pressure ethanol supply in the spring of 2016. This means that another green fuel is available on the P8 alongside the existing oxygen, hydrogen and methane fuels. For Europe, the P8 covers almost the entire range of the current fuel combinations of interest for the technology development and thrust chamber testing for launchers.

—Jan Alting, SALSA project manager at Airbus Safran Launchers GmbH

The burn test series is part of a German-Brazilian partnership that was initiated in 2011 between the German Aerospace Center and the Brazilian space agency Agência Espacial Brasileira (AEB). It focuses on cooperation in the areas of engine development, high-altitude research rockets and research into weightlessness.

The L75 engine and one of the two injection heads were developed, built and financed by the Instituto de Aeronáutica e Espaço in Brazil. The planning, execution and evaluation of the test series, as well as the production of the second injection head, were coordinated by Airbus Safran Launchers GmbH on behalf of the DLR Space Administration and carried out with funding from the German Federal Ministry for Economic Affairs and Energy (BMWi).

Resources

• Daniel Soares de Almeida, Cristiane Maria de Moraes Pagliuco, Bernardo Reis Dreyer de Souza, Holger Burkhardt, Claus Lippert, Axel Preuß, Günter Langel (2016) “Cooperative Development Of L75 LOX Ethanol Engine: Current Status With Focus On Capacitive Chamber Testing” Space Propulsion 2016

• Daniel Soares de Almeida, Cristiane Maria de Moraes Pagliuco (2014) “Development Status of L75: A Brazilian Liquid Propellant Rocket Engine” J. Aerosp. Technol. Manag. doi: 10.5028/jatm.v6i4.386