As part of a US Department of Defense initiative, hypersonic scramjet engines have been tested using 3D printing technology.

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The aerospace and defense industry is experiencing a remarkable collaboration between Lockheed Martin, Velo3D, Vibrant, and the US Department of Defense’s LIFT Institute. These companies have joined forces to explore the potential applications of 3D printing in hypersonic ramjet engines.

Unlike turbojet engines, ramjet engines have a complex internal structure and minimal moving parts. They generate high pressure by “ramming” external air into the combustor using the aircraft’s forward speed. Compression occurs through a series of shock waves, which, along with the engine’s internal geometry, decelerate the air until it becomes subsonic in the combustion section.

To assess the viability of additive manufacturing techniques in producing certified mission-ready ramjet engines efficiently and reliably, the team manufactured and tested the components. Velo3D’s laser powder bed fusion (LPBF) technology was used to 3D print the engines, which were then subjected to Vibrant’s acoustics-based Process-Compensated Resonance Testing (PCRT). This rigorous testing process analyzed various physical properties, including stress state, part integrity, geometry, and surface finish.

The project has been deemed a success, prompting the team to shift their focus onto the next research phase. This stage will delve into the fatigue behavior of 3D printed components and aim to create “born-certified” parts. Dr. John Keogh, LIFT’s Engineering Director, commended the partnership between Velo3D, Lockheed Martin, and Vibrant, stating, “The team… are probably some of the closest – if not the closest – to solving this problem of qualification and validation or certification of AM components for mission-critical and safety-critical applications.” Keogh also expressed a desire to see hypersonic components that are certified straight from the 3D printer using the captured data stream.

The defense and aerospace industries have recognized the urgent need for propulsion systems capable of achieving supersonic and hypersonic flight speeds. 3D printing is gaining traction as a viable technology for manufacturing these complex engine designs, offering lighter weights and faster production times compared to traditional manufacturing methods.

In 2022, Hermeus, a US aerospace start-up, successfully tested its partially-3D printed hypersonic Chimera engine. The Chimera seamlessly transitioned from turbojet mode to a high-Mach speed ramjet model. Aerojet Rocketdyne also conducted flight testing of its 3D printed scramjet engine as part of a US hypersonic missile research project, further highlighting the potential of 3D printing in this field.

Through the LIFT Institute, the Department of Defense is investing resources to determine the reliability of additively manufactured engines under the extreme conditions present during hypersonic flight. The ramjet project is one of many under the ongoing “Hypersonic Challenge,” funded by the DoD’s Manufacturing Technology Program and overseen by the Office of the Under Secretary of Defense for Research and Engineering. This challenge aims to identify the most productive and efficient materials and manufacturing processes for hypersonic flight-capable vehicles and missiles.

During the ramjet project, the team sought to collect data streams throughout the LPBF 3D printing process. Using a well-established Design of Experiments, they analyzed these data streams to improve the technology. Lockheed Martin provided the quality assurance verification approach for the project.

Velo3D’s Sapphire 1 MZ LPBF 3D printer was utilized to print the ramjet engine using Inconel 718 metal alloy. The Sapphire 1 MZ can produce objects up to one meter in height, with the final ramjet piece measuring 751 mm tall. Additionally, the Sapphire system incorporates hundreds of sensors that monitor, report, and save metrics throughout the printing process.

With its extensive data collection capabilities and successful collaboration between industry leaders, this project represents a significant step forward in the development of 3D printed hypersonic engines. As additive manufacturing continues to evolve, we can anticipate more groundbreaking advancements in the aerospace and defense sectors.

In the world of additive manufacturing, innovation is constantly pushing the boundaries of what is possible. One company, Velo3D, has recently made waves with its groundbreaking 3D printing technology and the incredible capabilities it offers.

One of the standout features of Velo3D’s technology is its Intelligent Fusion and Sapphire’s patented recoater technology. These advancements eliminate the need for support material when 3D printing complex models, such as a ramjet engine. This is achieved through a meticulous process where a blade normalizes each layer of powder, followed by a vacuum that removes excess powder, leaving behind a flawless powder layer. This clever technique creates a gap between the blade and the growing part, minimizing the risk of collision and eliminating the need for supports.

Initially designed for inclusion in a supersonic jet engine, the team at Velo3D believes that with a few minor adjustments, their ramjet engine could easily be transformed into a scramjet engine. A scramjet, or supersonic combustion ramjet, is a modified version of a ramjet engine that maintains higher airflow speeds through the engine. Theoretically, this technology could power vehicles to hypersonic velocities exceeding Mach 5.

In addition to the ramjet engines, the team also utilized their 3D printing capabilities to create unique material test parts with intriguing names like “dog bone” and “detergent pacs.” These parts were used for various evaluations, including tensile pull testing, density assessment, and surface finish analysis.

To ensure the quality and integrity of their 3D printed components, the team turned to Vibrant’s Process Compensated Resonance Testing (PCRT) process. PCRT utilizes ultrasonic frequencies to excite the vibrational modes of the part, recording and analyzing the unique resonance frequencies. By comparing these resonance values against established metrics for high-quality parts, any outliers can be easily identified, ensuring manufacturing consistency and final product quality.

The PCRT process provides valuable insights into the stress state, geometry, surface finish, and material properties of the components. It can also assess various process parameters, such as energy density, scanning speed settings, raw material properties, build position, cooling rates, and post-processing methods. This non-destructive testing technique offers a volumetric and rapid approach that complements additive manufacturing perfectly.

John Keogh, technical lead at Velo3D, expressed excitement about the potential of integrating PCRT with additive manufacturing, stating, “This is a very attractive approach to couple with and complement additive manufacturing because it’s volumetric, rapid, and it doesn’t require destructive testing. It can provide indications of porosity, surface defects, aberration in the geometry, and so forth.”

The combination of Velo3D’s groundbreaking 3D printing technology and Vibrant’s PCRT process is revolutionizing the additive manufacturing industry. With their ability to create complex structures without the need for support material and ensure the quality and integrity of their components, Velo3D is pushing the boundaries of what is possible with 3D printing.

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The featured image showcases John Keogh, technical lead at Velo3D, and project manager Brad Friend holding a cut section of the 3D printed ramjet. The intricate design and flawless execution of this component exemplify the groundbreaking advancements in additive manufacturing.

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