CNES explores space propulsion system improvements with 3D printed ceramics

New research from the French Space Agency (CNES) is studying how 3D printed oxide ceramic materials could improve the design of crucial subsystems for space propulsion.

The research is focused on developing an optimized yttrium aluminum garnet (YAG) xerogel that provides desirable strength and creep resistance properties when 3D printed in complex shapes.

According to CNES, these additively manufactured YAG ceramics could form the basis of metal alloys used in future turbine blades for deep space exploration.

3D printed YAG ceramic structures. Image via Scientific Reports.

Ceramic 3D printing for space

3D printed ceramics are increasingly being explored for a range of space-related applications, due to the desirable mechanical properties of materials and geometric design possibilities enabled by additive manufacturing technologies.

For the past few years, 3D printed ceramics have been used to create improved components in next-generation rocket engines, alongside other new aerospace applications. A company at the forefront of ceramic innovation is CeramTecwho has already worked with European Space Agency (ESA) and Airbus produce a new generation of ceramic sample containers for a space experiment facility aboard the international space station (ISS).

The ISS also houses Made in space ceramic manufacturing facility, the Turbine Ceramic Manufacturing Module (CMM), which contains an SLA 3D printer to demonstrate the feasibility of manufacturing one-piece ceramic turbine components in microgravity environments.

More recently, Digital Composite Manufacturing (DCM) 3D printing platform developer Strengthen has partnered with a ceramic 3D printing specialist 3D Tethon develop new technical ceramics for additive manufacturing, including extreme temperature parts such as rocket nozzles.

Elsewhere, 3D printing service desk 3DCeram has teamed up with CNES spin-out Anywaves to design 3D-printed ceramic antennas for small satellites, while Austrian engineering firm Anvil currently working with ESA and ceramic 3D printing specialist Lithoz to explore how metal waste available on the lunar surface could be processed to 3D print spare parts for lunar stations.

NASA engineer Kate Rubins next to the CMM installed on the ISS.  Photo via NASA.
NASA engineer Kate Rubins next to the CMM installed on the ISS. Photo via NASA.

Improving the design of space propulsion systems

CNES’s latest research and development efforts on oxide ceramics hope to improve the design of crucial space propulsion subsystems to improve the performance of liquid-propelled rocket engines.

Currently, the maximum allowable turbine temperature, imposed by the strength of metal alloys, limits the performance of liquid-propelled rocket engine cycles. According to the agency, the introduction of creep-resistant oxide ceramics for turbine parts could help increase the cycle temperature and therefore improve performance during deep space exploration missions.

YAG was chosen because of its desirable high temperature mechanical properties, in particular its high strength, good creep behavior at temperatures above 1000 degrees Celsius, low thermal conductivity, physical and chemical stability and high strength. corrosion by water vapour.

Currently, due to its low cost and ease of use, extrusion is one of the most widely used technologies for the direct shaping of ceramics. While additive manufacturing has been used to print YAG ceramics in the past, the team identified potential challenges to scaling up the process and producing larger quantities, such as the formation of impurities.

As a result, they embarked on improving and intensifying the process of preparing a YAG xerogel – the solid left over from the evaporation of liquid from a gel at room temperature – and investigated the printability of the xerogel-based paste obtained.

The protocol for the preparation of YAG xerogel.  Image via Scientific Reports.
The protocol for the preparation of YAG xerogel. Image via Scientific Reports.

Cost reduction and energy saving

Using this technique, the CNES team succeeded in scaling up production of the YAG xerogel by modifying a protocol designed for “lab-scale” synthesis. The researchers used dried YAG xerogel to formulate a paste that could be 3D printed using a Delta WASP 2040 clay 3D printer from a construction 3D printing company. WASP.

The printed rope structures were then calcined at different temperatures to follow the transformation of the xerogel into a crystalline YAG ceramic. Thanks to this process, the team proved the possibility of sintering and obtaining cohesive ceramic parts after heat treatments between 1550 and 1700 degrees Celsius.

The team also observed that their combined preparation and 3D printing process was able to reduce costs and energy, and would therefore be “appreciated by the industrial sector” as an energy-efficient process. In particular, the CNES team sees the fabrication of ceramic turbine parts for space exploration as a promising application for their 3D-printed YAG xerogels.

Further information on the study can be found in the document entitled: “Synthesis and robocasting of xerogel YAG: one-step conversion of ceramics”, published in the journal Scientific Reports. The study is co-authored by N. Flores-Martinez, L. Quamara, F. Remondiere, J. Jouin, G. Fiore, S. Oriol and S. Rossignol.

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Featured image shows 3D printed YAG ceramic structures. Image via Scientific Reports.

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