Flight of the aerospike

Spanish additive manufacturing company Aenium describes its recent bid to develop an aerospike engine using a prestigious NASA metal alloy.

GRCop 42, manufactured by NASA, is a high conductivity, high-strength alloy which can cope with high heat flux applications such as liquid rocket engines and other combustion devices. Recently, NASA developed a process for additive manufacturing (AM) of GRCop-42 alloy to establish parameters, characterize the material, and complete testing of components with complex internal features. According to NASA, 3D printing processes used are powder bed fusion (PBF) and selective laser melting (SLM).

Recently, AM company Aenium, specialized in material science, additive manufacturing, complex manufacturing and advanced postprocessing based in Valladolid, Spain, in partnership with rocket specialist PANGEA Aerospace, won a contract to have exclusive use of the GRCop 42 alloy in Europe.

Aenium plans to, for the first time, develop and commercialize GRCop 42 based propulsion systems for the European aerospace market, using AM , complex post-processing and multi-material components. The companies also plan to bring to the EU market the first GRCop 42 industrialised unit to enable other space companies to access 3D printed GRCop 42 alloy propulsion systems as well.

According to Miguel Ampudia, CEO of Aenium, GRCop 42 can be very successfully used to make aerospike and other rocket engines using AM, challenging in terms of material science and processing but unique in thermomechanical performance. Aerospike engines are a type of rocket engine featuring a plug nozzle that can direct the exhaust of a rocket engine in one direction, generating thrust in the opposite direction.

“The aerospike engine can radically transform space propulsion thanks to its higher efficiency (up to 15% than currently used rocket engines), reusability capabilities and very low-cost and rapid manufacturing,” Ampudia told Metal Powder Report.

Engineering difficulties

Several aerospike engines have been developed or conceptualized in history (J-2T, XRS-2200 and RS-2200) but none has ever flown due to the engineering difficulties historically linked with aerospike nozzles: cooling and manufacturing. Now, AM techniques and new materials such as GrCop42 are increasing the possibility of building a functional and economically viable aerospike engine at much less cost and in a shorter period.

“GRCop42 based alloys are one of the key solutions that allow us to solve the thermal challenges of an aerospike nozzle rocket engines,” said Adrià Argemi, CEO of Pangea Aerospace. “We are now ready to offer this unique capability to all the European aerospace sector.”

Metal Powder Report spoke to Miguel Ampudia about how his company achieved the license for researching, qualify and process GRCop42. “It was a complex procedure with many validation steps from the US. After all these first steps we invest more than 120k€ in direct researching and metallurgy qualification of the process and much more in the capex capabilities for being processed. We achieved full material and process qualification for ensuring high performance under the most demanding boundary conditions and reaching orbit.”

By researching materials and structure, Aenium was able to make an GRCop 42 combustion devices with up to 25% of mechanical properties at creep, 30% of heat transfer conductivity increase and higher corrosion resistance for ensuring reusability.

“That’s a big deal, because commonly one kilo of material costs around $25,000 in terms of distributed costs,’ Ampudia said. “Reducing weight and increasing efficiency here means that you can increase payload elsewhere, thus saving more cost.”

AM in Europe

We asked Miguel Ampudia about how he sees the AM industry in Europe now.

“The European space market is growing really fast, with large companies such as Airbus, Isar Aerospace and Rocket Factory based in Germany and Ariane Space based in France amoung others. But I think AM is divided in two industries right now,” he told the magazine. “There’s rapid prototyping or 3D printing where there is less need to certify the process and materials. Businesses working in the file are more like service providers – you email a file, you get a 3D printed part back. My industry, which is completely different, is more about responsible, certified components but also innovative research and material science. There are only a few companies in this field in in Europe, because they need to not only own AM machines, but also have know-how with regards to metallurgy, material science, post processing, qualification.

“But taking the time to certifying AM parts is worth it, for three reasons. Firstly, to make the most of the complex geometries, which are obviously very important in rocket parts. Secondly, because the lead time can be really short. Thirdly, we can have so much control over the part voxel. Depending on the cooling ratio applied by the laser, we can achieve different microstructures in a component. One side can be very conductive in terms of heat transfer, while another part can be not conductive at all, because we change how the laser is applied.”

Was heat transfer an important factor in making the aerospike part? “Absolutely, and that’s why the space sector needs a real material science focus when using or developing complex alloys. There are also hundreds of cooling channels around the part, which can only be achieved with 3D printing.”

While materials science is important, industrialising AM processes and parts is important too, according to Ampudia. “While we can research and process definition for a lot of new and very useful powder alloys, certification and testing can only take place when industrialisation is on hand. And that’s the best way to see if an alloy really works or not.”

Ampudia suggests that the space industry is going to be a big driver for AM. “At the start of the Covid lockdown, we were really worried about what was going to happen, because the aviation market went completely dead in just a few days, But the space and aerospace industry is still growing. Right now, there are around 7500 satellites in space, but it’s expected that in 2030, those will grow to 22,000.”

What are the big drivers in the space industry? “Right now, the main investors are telecoms – both for defense and commercial use. Private providers such as Space X, are big players as well. Space is belonging increasingly to the private sector.”

Future developments and outcomes

What’s next for Pangea and Aenium? The former is reportedly manufacturing a liquid oxygen and methane aerospike engine demonstrator designed to characterize and validate the use of methane as a fuel, as well as the part’s dual regenerative cooling system. It also plans to test the design for reusability. A hot-fire campaign was planned for the end of 2021 and represented a huge success, more than 5 fire runs and 160s of hot firing (attached image of the engine firing). This was the first MethaLOx aerospike firing in the world until today.

According to a press release, Pangea has already started the preliminary design of a larger, commercially ready aerospike engine and its subsystems.

According to Miguel Ampudia, this could lead to the European aerospace sector having better access to cutting edge materials such GRCop-42 alloy. Aenium is also considering using its materials and 3D printing technology for other markets. “We are researching what capabilities we can achieve in terms of super conductivity through complex alloying and programming elements on the parts. Energy is also a big market in Europe – particularly nuclear fission and fusion and oil&gas industry. We are also interested in health and have done some research into complex alloy custom implants for the human body.”