Successful Hot-Fire Test of Metal 3D Printed Fuel Injector from Elementum 3D & Masten Space Systems

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Colorado-based AM research and development company Elementum 3D develops and supplies advanced metal, ceramic, and composite materials, and started its partnership with aerospace manufacturing startup Masten Space Systems, in California, back when the two were both working on a NASA Tipping Point program to make an aluminum MMC combustion chamber for Masten’s 25k Broadsword Engine with Elementum’s RAM 3D printing process. Fast forward to now, and as part of a NASA Phase I SBIR project, the two recently completed a successful hot-fire test of the PermiAM metal 3D-printed fuel injector they developed together.

Masten Space Systems Chief Engineer Matthew Kuhns had originally taken notice of an experimental build being developed by Elementum’s president and founder Dr. Jacob Nuechterlein. That’s when the two companies began collaborating in order to refine the Reactive Additive Manufacturing (RAM) technology for use in aerospace applications, like combustion and rocket engine devices.

“This exciting work with Masten is leading us to new and exciting technologies only possible with 3D printing. We see PermiAM making a significant impact on all sorts of industries, from diesel engines to complex heat exchangers to carbon sequestration,” said Dr. Nuechterlein. “Like many space innovations, we are applying our joint technology to a wide variety of terrestrial applications as well.”

L-R: Unmodified “standard” 2024 aluminum alloy without RAM addition exhibits columnar grain growth, and Elementum 3D’s A6061-RAM2 aluminum alloy with RAM addition exhibits ductal behavior. (Image: Elementum 3D)

As a result, the two began working on the patent-pending PermiAM laser powder bed fusion (L-PBF) AM process, which allows for material-agnostic transpiration cooling: a thermodynamic process where a liquid or gas is moved through the wall of a structure to cool it by absorbing some of its heat energy. In fact, some of the NASA engines that have seen the most action, like the RS-25 and RL10, use injector faces with this type of cooling.

However, most of these injectors are fabricated out of a porous metal filter element called Rigimesh: basically several stainless steel mesh layers pressed and sintered together into a stiff but permeable screen. The issue is that Rigimesh is quite old, and can’t be 3D-printed. Elementum and Masten’s jointly-created PermiAM process makes it possible to additively manufacture complex rocket engine injectors with face cooling.

PermiAM can tweak a part’s structural and flow performance, as the process can achieve varied material density. Parts with varied material density can be stiff, strong, and lightweight at the same time, and this helps boost the engine thrust-to-weight ratio. This allows for novel injector geometries, with structural members, to be embedded in porous, transpiration-cooled faces, and the integration of small-scale porous flow paths into structural elements.

In comparison with conventional methods of manufacturing, the process is also able to form micro-scale porosity, which, as Elementum explains, enables high injector performance through “high-fluid resistivity and controllable pressure drops.” By partnering dense structures with areas of controlled permeability in one injector component, the design is much simpler, which means the schedule speeds up, and costs go down as well.

In the business world, a process or technology is considered a game-changer if cost-savings meet, or exceed, 60%, which is exactly what Masten has figured out that PermiAM can achieve. Additionally, because PermiAM cooling could make it possible to replace Inconel parts with aluminum ones, there’s a possibility for future time savings of more than 90%, and 50-70% weight savings for the hot structure, in comparison to Rigimesh rocket injector faces.

“This collaboration is the prime example of how US industry is staying at the forefront of business,” noted Sean Mahoney, the CEO of Masten Space Systems. “The value of this technology is unlocked where it turns into applications – and that is precisely what Elementum and Masten are doing. This partnership is already helping improve systems here on Earth, and unlocking the Moon for our future.”

Masten and Elementum have successfully hot-fired their PermiAM fuel injector with Elementum’s AMCopper-100 (pure copper) and A1000-RAM10 materials, and tests are pending for both its GR-Cop42 and Inconel 625. The jointly-developed technology can also be used in environments other than space, such as automotive fuel injection and commercial jet engines.

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(Source: Metal AM)

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