"When manufacturing the rocket from metal, we decided to use additive manufacturing because the engine requires very good cooling and internal cooling ducts. Such a complex regenerative cooling system with its intricate structures cannot be conventionally milled or cast," says Mirko Riede, group manager at Fraunhofer IWS. The powder is applied layer by layer and then selectively melted by laser. Subsequently, the powder is sucked out of the channels. The demands on the metal: Temperatures of several 1000 degrees Celsius prevail in the combustion chamber. The material thus must remain solid and conduct heat well to ensure optimum cooling.
Following the production of a prototype, the project CFDμSAT has focused on the injection system since January. With this, the developers want to further increase the efficiency of the drive systems. Associated partners in the project are the ArianeGroup and Siemens AG. The production of the injectors places particularly high demands on design and production. The fuels are first used to cool the engine. During this process they heat up and are then introduced into the combustion chamber. Liquid oxygen and ethanol are supplied separately and brought together via an injector. The resulting gas mixture is ignited. It expands in the combustion chamber, then flows through a gap in the combustion chamber and is expanded and accelerated via the nozzle.
The prototype has already achieved a combustion time of 30 seconds on the test stand. Since there have hardly been any tests of aerospike nozzles to date, the Dresden researchers regard the test as proof that a functioning liquid engine can be produced using additive manufacturing.