Launch for small satellites! Fraunhofer releases a 3D printed plug nozzle engine

Miniaturization of satellites has become an industry trend. In the future, small satellites will play an increasingly important role, and develop towards practical and operational development, and their application capabilities in such fields as communications, earth observation, space science, and technical testing will be further improved. Between 2018 and 2022, the number of microsatellites launched globally will rise from 263 to 460. It is estimated that the global market for small satellites below 500 kg will reach 7.179 billion US dollars in 2022.[1]

The research and development of launchers for small satellite launches has also been active. The NSR report shows that China plans to lead the manufacture of small satellite launchers and the number of small satellite launches in the next 10 years. Domestic policy support is part of the driving force of the plan. .[2]Small satellite launcher manufacturing field for3D printingThe application of technology is also quite active. Recently, the Fraunhofer Institute (Fraunhofer IWS) in Germany revealed a kind of additive manufacturing-3D printingPlug nozzle engine, this engine is used in micro-satellite launchers with a payload of up to 350 kilograms. Compared with the traditional design, this engine has obvious advantages in light weight and fuel saving.

3D printingPlug nozzle display. Source: Fraunhofer IWS

Designed to save fuel and increase payload

This plug nozzle engine was developed in cooperation with the team of Fraunhofer IWS and the Dresden University of Technology. The fuel injectors, combustion chambers and nozzles in the engine use powder bed laser melting (L-PBF)3D printingTechnology made. The nozzle consists of a spike-shaped central body, which is designed to accelerate gas combustion. The Dresden University of Technology is responsible for the design of the engine, and Fraunhofer IWS is responsible for the manufacturing and material verification. The first step of the research team is to optimize the design to make it suitable for additive manufacturing technology. Then, print material selection and characterization.Next, use powder bed selective laser melting technology (L-PBF) to manufacture the two components of the engine, and3D printingThe functional surfaces of the components were reworked, and then the two components were joined together by laser welding. The quality inspection method used by the research team is computer tomography. This non-destructive inspection method is used to check for pores and other defects, and to determine whether the cooling channel is blocked by residual printing powder.

3D printingPrototype of plug nozzle engine. Source: Fraunhofer IWS

According to Fraunhofer IWS,3D printingThe plug-nozzle engine is expected to save about 30% of fuel compared to traditional engines. It is mainly due to two reasons. On the one hand, the compactness of the design reduces the weight of the entire engine, and every gram of weight reduction is of great significance to the spacecraft, because it means the required launch Fuel reduction and increase in payload. also,3D printingThe nozzle is better adapted to the changing pressure from the earth to the orbit, helping to improve efficiency and burning less fuel compared to conventional engines.

Engines have high requirements for cooling performance. The research team designed a cooling system with complicated internal pipes. Due to the high complexity, this structure cannot be realized by traditional milling or casting techniques. The selective laser melting equipment used by the research team can manufacture parts with a one-millimeter-wide cooling channel, which is a conformal cooling channel designed to follow the contour of the combustion chamber. After the printing is completed, the metal powder remaining in the channel during the process needs to be sucked up.

There is a high temperature of several thousand degrees Celsius in the combustion chamber. The material of the nozzle must meet the strict requirements, maintain a solid state at high temperature, and conduct heat well to ensure the best cooling effect. Fraunhofer IWS did not disclose the printing materials used this time.

The research team is still optimizing the engine’s injection system to further improve engine efficiency. The related project is called CFDμSAT, which started in January 2020 and is a collaboration with Ariane Group and Siemens. The design and manufacture of fuel injectors are the main challenges in the CFDμSAT project. When the engine is running, the fuel will first be used to cool the engine, and when they become hot, they are introduced into the combustion chamber. After liquid oxygen and ethanol are added separately, they are mixed through an injector. The ignited mixed gas expands in the combustion chamber, then flows through the gap in the combustion chamber, and is decompressed and accelerated by the nozzle.

At present, the research team has3D printingThe prototype plug nozzle engine was subjected to a hot fire experiment, and the combustion time reached 30 seconds.

Reference materials:

[1] Zhiyan Consulting, “Analysis Report on the Development Trend and Future Prospects of China’s Satellite Industry in 2020-2026”;

[2] Aerospace Great Wall-China Great Wall Industry Group “NSR｜Small Satellite Launch Market Situation”.

(Editor in charge: admin)