Will the successes of NASA’s RAMFIRE project lead to an operational aerospike engine? 

In addition to the February 2024 Momentum article, which established the viability of additive manufacturing (AM) aluminum rocket nozzles with A6061-RAM2 powder, the RAMFIRE project used A6061-RAM2 to print a 36-inch diameter aerospike nozzle with complex integral coolant channels.


For nearly seven decades rocket engineers have considered an alternate nozzle design beyond the bell-nozzle rocket engine, the aerospike design breaks free from the traditional bell nozzle rocket engine design, which is efficient at only one point in the rocket’s trajectory.

What exactly makes this nozzle so enticing, especially after the bell-nozzle has more than proved its capabilities throughout the history of human spaceflight? 


The Aerospike’s inside-out rocket nozzle plume travels externally rather than exiting inside of the traditional bell-shaped nozzle. The main advantage of aerospike nozzle is that, as the rocket climbs, atmospheric and airstream pressure act on the plume to keep it at an optimum setting along the entire trajectory. This allows for a very efficient engine performance in flight, capable of delivering higher payloads while decreasing overall rocket weight and improved performance over a range of pressure altitudes.


So, if the aerospike nozzle design is considered a more efficient way to propel rockets to outer space, why has it never been seriously tested on the launchpad?


The lack of actual flight test data has precluded use of these nozzles in current as well as next generation space launch vehicles. In addition, the configuration of an aerospike nozzle presents unique challenges to the designer and fabricator.


The mindset of the past is changing with the introduction of AM. NASA recently validated data from hot fire tests on their 3D printed aerospike engine and reported that recent advancements in 3D printing can overcome some of the engine’s design challenges—specifically, how to manage its temperature. The positive results have green-lighted NASA engineers to develop a larger version.


NASA’s RAMFIRE (Reactive Additive Manufacturing for the Fourth Industrial Revolution) project commissioned Elementum 3D to work closely with their engineers and scientists and RPM Innovations to develop and print a 36” diameter aluminum aerospike rocket nozzle out of A6061-RAM2 material. The build was performed using RPM Innovations’ large format laser powder direct energy deposition (LP-DED) process.


Why has it taken almost 70 years to successfully produce a lightweight, high-strength aluminum rocket engine?


For one thing, conformal cooling channels are needed to keep the nozzle well below the material’s melting temperature. Curved internal voids are a specialty of additive manufacturing; these would be far more complex to achieve using a casting process and machining them would not be possible. Secondly, metal additive manufacturing via laser melting processes only became industrialized in the past few decades as computer, automation, and laser technology became simultaneously increasingly sophisticated and affordable. And finally, additive manufacturing of aerospace grade aluminum materials has only been possible since Elementum 3D invented its RAM technology in the past decade.

Aluminum alloys are highly prone to a type of cracking called hot tearing under the rapid heating and cooling conditions inherent to laser welding processes, and some popular wrought aluminum alloys including AA6061 are widely considered unweldable for this reason. Elementum 3D’s RAM chemistry serves to control the solidification process, resulting in crack free, fine-grained microstructures and printed material with strength equal – and in some cases, superior – to wrought aluminum.


Will the combination of optimized thermal and mechanical properties of A6061-RAM2 generated from RAM technology and the design freedom of additive manufacturing be the path to an operational aerospike rocket engine?


Only time and further research can answer that question. The research data acquired from the optimization of A6061-RAM2 aluminum alloy for large blown powder DED brings incredible confidence in enabling the production of an operational aerospike nozzle. NASA engineers plan to use the demonstration nozzle as a proof of concept to inform future component designs.

Learn how software is impacting the advancement of AM quality.


Additive Manufacturing (AM) relies on the synchronization of design, hardware, software, and materials to successfully produce high-quality prints. On May 1 at 11am ET, the 1.5 hour “Bridging the Gap” webinar will zero in on how software is revolutionizing the advancement of AM technology and what role it is playing in predictive modeling, build optimization, real-time production monitoring, design innovation, quality control, production efficiency, material capabilities, and ultimately, grow market adoption. 


This live webinar, hosted by Elementum 3D, features AM software experts from industry leading companies. They will disclose valuable real-world insights into the ever-widening capabilities of software and how it is transforming the additive manufacturing industry. An interactive Q&A session follow the presentations.


Registration NOW on the Elementum 3D website Events page.

Purdue University Space Program students select A6061-RAM2 for their TADPOLE propulsion system

Additive manufacturing (AM) is transforming the impossible into possible. It’s also transforming how the next generation of innovators will design and manufacture the products of tomorrow. The rapidly expanding successes in 3D printing space-related applications (i.e. NASA’s RAMFIRE program) have inspired a team of fifty enthusiastic undergraduate students on Purdue University’s Active Controls team to optimize the benefits of AM to advance vertical take-off and vertical-landing (VTVL) technology.


The Purdue Space Program-Active Controls (PSP-AC) team is under an umbrella student organization on Purdue University's campus that aims to empower students to innovate in space exploration. Their current project satisfies the milestones of the Collegiate Propulsive Lander Challenge (CPLC) which has challenged student teams to create self-landing rockets. This challenge gave rise to PSP-AC’s TADPOLE propulsion system.

"This team operates under a greater vision to prepare the current and future classes of engineers to be more attuned to the current technological trends in space exploration," said Pavit Hooda, PSP-AC project manager and co-founder.

 

The TADPOLE propulsion system is part of PSP-AC's journey of creating a bipropellant hopper vehicle. Such a vehicle requires a propulsion system with long burn times, a regenerative cooling circuit, and thrust vector control capabilities. To produce a thrust chamber assembly (TCA) that can achieve these extreme specifications with complex geometries and precise tolerances, PSP-AC chose Elementum 3D to print the aluminum combustion chamber, cooling circuit, and nozzle in a single component using laser powder bed fusion. 

“We are honored to offer our team’s AM knowledge, expertise, and technology to inspire all the students involved in the Purdue Space Program to push the limits of conventional thinking and print the first ever A6061-RAM2 thrust chamber assembly,” said Dr. Jacob Nuechterlein, Elementum 3D founder and president.

 

At a chamber pressure of 250 psi and a thrust class of 550 lbf, PSP-AC determined that Elementum 3D's advanced RAM technology was necessary for making this project a reality. The aluminum alloy A6061-RAM2 material provides the proper yielding characteristics required for the operating conditions of TADPOLE and offers an extended lifespan to the TCA enabling the team to include more tests in their test campaign, ultimately allowing them to learn more from this experience of designing and testing a propulsion system.


PSP-AC selected aluminum to print the thrust chamber assembly because of its great thermal properties, light weight, and low cost. The team was enthusiastic to discover Elementum 3D’s aluminum alloy does not have the drawbacks that we found with other AM aluminum powders, such as rough surface finish. The thrust chambers printed with A6061-RAM2’s had a very smooth surface finish, which is good for heat transfer and better thermal and mechanical properties than the competing alloys.

 

Another challenge of 3D printing a TCA is the post-processing and depowdering of the internal channels. The PSP-AC team worked very closely with Elementum 3D engineers to develop viable solutions and dimensions to allow for adequate powder removal. A big “a-ha” moment was realized when the team found it generally easier to depower than the industry standard GR-COP alloys, which is a big advantage. Additionally, the PSP-AC team enjoyed working closely with Elementum 3D’s engineers to get detailed material property information on the alloy, which was something they struggled to get from other vendors. This allowed them to understand and model the performance and functionality of the TCA and ultimately compare to experimental data generated during engine testing.

“The whole process is a great engineering challenge and learning experience that was made possible by Elementum 3D’s support. PSP-AC will use these simulations and experimental results to design their next engine,” said Andrew Radulovich, PSP-AC chief engineer.

 

There are many organizations that are invested in the success of the PSP-AC team. We are delighted to be one of them. Aiding them in their journey to print an aluminum thrust chamber goes well beyond propelling space technology to greater heights; it ultimately builds confidence in the reliability and repeatability of AM.

Sister company Fortius Metals awarded $1.25M AFWERX contract

Focused on qualifying IN625-RAM2 wire alloy for the large-scale AM of components for hypersonic applications

Fortius Metals, a company specializing in metals for robotic 3D printing/WAAM technology, has been awarded a $1.25M AFWERX Direct-to-Phase II SBIR contract focused on qualifying IN625-RAM2 wire alloy for the large-scale AM of components for hypersonic applications.


Nickel superalloys are important for high-performance defense applications. Fortius Metals’ Reactive Additive Manufacturing (RAM) technology improves alloy grain structure to double IN625 yield strength at room temperature and increase yield strength up to 50% at 800°C, without sacrificing ductility or toughness. Hypersonic applications are extremely demanding on materials, and next-generation alloys are needed to solve tomorrow’s engineering design challenges. Fortius will print large-format hypersonic prototypes using its advanced IN625-RAM2 and wire Directed Energy Deposition (wire DED) robotic welding cells.


FULL ARTICLE

Elementum 3D

400 Young Court, Unit 1, Erie, Colorado

720-545-9016

www.elementum3d.com

Facebook  Twitter  LinkedIn  YouTube