NASA eyes 3D-printed rocket nozzles for deep space missions

Additive manufacturing might not be for everyone, but rocket makers seem to like it

NASA has tested a 3D-printed rocket engine nozzle made of a weldable type of aluminum with the aim of adding more payload to deep space missions.

Mass is key in spacecraft, and aluminum is almost an ideal material. It has a lower density and can be used for high-strength and lightweight components.

However, it isn't great when it comes to heat and also tends to crack during welding. Furthermore, a typical rocket nozzle may need a thousand or so individually welded parts.

NASA's Space Technology Mission Directorate (STMD) has funded the Reactive Additive Manufacturing for the Fourth Industrial Revolution (RAMFIRE) project to work on the issue.

Under RAMFIRE, engineers designed lightweight, 3D-printed aluminum rocket nozzles with internal channels to keep the nozzle cool enough to prevent melting. It also makes use of a novel aluminum variant called A6061-RAM2.

Building the nozzle as a single piece means far fewer bonds and reduced manufacturing time.

Paul Gradl, the RAMFIRE principal investigator, said: "We've reduced the steps involved in the manufacturing process, allowing us to make large-scale engine components as a single build in a matter of days."

It's impressive stuff, and while the RAMFIRE nozzle itself won't see action on a spacecraft, engineers plan to use it as a proof of concept to inform future designs. Two nozzles have also completed multiple hot-fire tests using liquid oxygen and liquid hydrogen over nearly 10 minutes of run time and 22 starts.

3D printing rocket components has proven popular within the space community. Rocket Lab's Rutherford engine is the world's first 3D-printed, electric-pump-fed engine, while UK-based Skyrora also intends to use 3D printing for the engines of its orbital launch system.

Orbex too is making use of the technology. CEO of the company, Martin Coates, told The Register today: "We use 3D printing to create components including the turbopump assembly and engine chambers of the Orbex Prime microlauncher.

"The technique allows us to print our full main stage rocket engines and associated parts in a single print run. This means we don't need to join smaller sections with welds, bolts or flanges. This eliminates the need for any unreliable hot joints and avoids outdated and error-prone additional processing steps.

"It reduces mass and fully automates production. The components are printed using a superalloy which allows us to create parts that can withstand the extreme environment in space and, therefore, we understand why the NASA RAMFIRE project is adopting this manufacturing process."

However, Coates also cautioned that setting up the process was technically challenging and costly, requiring investment in design, equipment, and powder. Although, once running, the process could knock out components expeditiously.

Speaking at this month's Canalys EMEA forum, HP CEO Enrique Lores noted that despite high hopes for 3D printing technology, widespread adoption had yet to happen. However, there were opportunities for 3D printing to create products that could not be made using traditional processes.

He cited sectors such as healthcare, fashion, and "in some fairly complex parts for the auto industry."

To that, one can add space.

However, Lores also warned: "If we try to use printers just to replace equivalent process, the economics are not there." ®

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