Rocket engine comes out of the printer
The market for small satellites is expected to boom in the coming years. Great Britain is planning the first spaceport on European soil in the north of Scotland, and Germany is also mulling the construction of a launch site. From there, small to medium-sized rockets will carry research instruments and small satellites weighing up to 350 kg into space. An efficient way to propel these microlaunchers are so-called aerospike engines. These not only offer the prospect of a considerable reduction in mass, but also a significant saving in fuel.
A research team of the TU Dresden and the Fraunhofer Institute for Material and Beam Technology IWS has now developed, manufactured and tested such an aerospike engine. The special feature: Fuel injector, combustion chamber and nozzle are manufactured layer by layer by Laser Powder Bed Fusion (L-PBF), an additive manufacturing process. The nozzle itself consists of a spiked central body through which the combustion gases are accelerated.
Although the technical concept of aerospike engines is already around 60 years old, it is only the additive manufacturing process with its high degree of design freedom as well as the embedding of this technology in conventional process chains that makes it possible to build such engines. Aerospike rocket engines promise fuel savings of around 30 percent compared to conventional rockets. They are also more compact and lightweight than conventional systems.
“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.
More information:
https://www.materials.mw.tu-dresden.de
https://www.iws.fraunhofer.de/en.html
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