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Data-driven 3D printing unlocking hypersonic travel

Ramjet on display

The ramjet design originated from an undergraduate aerospace engineering assignment (Image: Lockheed Martin)

In a significant leap towards achieving hypersonic flight capabilities, a pioneering collaboration between Velo3D, Lockheed Martin, Vibrant, and the US Department of Defense's Lightweight Innovations for Tomorrow (LIFT) Institute is pushing the boundaries of aerospace technology. 

This partnership is centred around the development and certification of materials and methods for additively manufactured aerospace systems.

The hypersonic revolution, now

Hypersonic flight vehicles and missiles are no longer the stuff of science fiction, but are fast becoming reality – the global race to develop propulsion systems capable of achieving hypersonic speeds (above Mach 5) has intensified. 

In this quest for speed and efficiency, 3D printing technology has become an emergent game-changer, allowing for the creation of complex, single-piece engine designs that are significantly lighter and quicker to produce than traditional manufacturing methods.

Leading the way in materials and manufacturing 

While the promise of 3D printing in aerospace is clear, the US Department of Defense recognises the need for meticulous evaluation and certification, beginning with a deep dive into materials science and manufacturing. LIFT, a nonprofit public-private partnership with an aim to scale new technologies into commercialisation, is at the forefront of this mission.

Operated by the American Lightweight Materials Manufacturing Innovation Institute, LIFT is engaged in various projects, including a ‘hypersonics challenge’, funded by the Department of Defense's Manufacturing Technology Program. The goal of this challenge is to identify the most efficient materials and manufacturing processes for hypersonic flight vehicles and missiles.

3D-printing and testing a ramjet engine 

One standout project within the ‘hypersonics challenge’, led by an external team with Lockheed Martin as the industry prime and team lead, recently concluded the first phase of a study involving a 3D-printed ramjet engine. 

The ramjet engine was printed using Velo3D's Sapphire 1 MZ system, capable of creating objects up to one metre in height. Velo3D's technology eliminates the need for support materials, thanks to intelligent fusion and the Sapphire's patented recoater technology. This not only streamlines the printing process, but also results in better surface finishes for complex geometries.

Dr John Keogh, LIFT's Engineering Director, and Dr Amberlee Haselhuhn, Director for Materials & ICME, played key roles in overseeing this project, collecting data during the 3D printing process.

Showcasing the engine parts

Dr John Keogh of LIFT displaying the inside structure of the 3D printed ramjet engine (Image: LIFT)

Keogh said: “AM is a relatively new manufacturing process and there’s a need to validate and certify parts for service and mission-critical applications. Our goal was to identify the signatures of physical quality found in process data and rapid post-process inspection for accurately certifying a component for the rigours of hypersonic flight.” 

This data-driven approach sought to directly certify 3D printed components, rather than relying on traditional statistical methods that involve producing multiple parts and then testing them. The focus was on identifying ‘echoes of quality’, ensuring the components meet the rigorous demands of hypersonic flight.

From student assignment to big aerospace reality

The ramjet design itself originated from an undergraduate aerospace engineering student's assignment at Purdue University. Inspired by the J-58 turbojet used on the SR-71 Blackbird, Jay Blake, the student involved, envisioned consolidating complex engine components into a single 3D-printed structure. 

The idea remained on the drawing board, until he joined Velo3D and, armed with advanced digital tools, brought his concept to life.

Blake said: “My thought was that, using 3D printing, you could incorporate the volume of the inlet spike of a ramjet into the turbojet, to act as a heat exchanger to warm the fuel so it combusts more efficiently. The early ramjets had hundreds of different parts – injectors, struts, internal details – that required welding and brazing and took months to produce; my design idea was to consolidate all those parts into one so it could be printed in a matter of days.” 

3D printed ramjet engine

The 3D printed ramjet engine (Image: LIFT)

The project then garnered the attention of aerospace giant Lockheed Martin, who recognised the potential for single-piece engine geometries in hypersonic applications. The ramjet design, originally intended for supersonic engines, underwent modifications to potentially reach hypersonic velocities exceeding Mach 5.

The collaboration between Velo3D, Lockheed Martin, and LIFT focused on evaluating the maturity of metal 3D printing for aerospace applications and ensuring the fidelity of materials used in the process. 

Quality assurance through resonance testing

To test the approach, the team utilised Process-Compensated Resonance Testing (PCRT) from Vibrant, an innovative approach to quality assurance.

This technique relies on ultrasonic frequencies to analyse the natural resonance frequencies of printed parts, which are unique to their geometry and material properties. PCRT allows for the detection of stress, part integrity, geometry, and surface finish issues without the need for destructive testing.

Next steps: born-certified hypersonic components

The success of this programme has set the stage for the next phase of research, which will focus on the fatigue behaviour of 3D-printed components. The ultimate goal is to produce ‘born-certified’ parts directly from the 3D printer, leveraging the data streams collected to back up their certification for mission-critical and safety-critical applications.

As the LIFT Institute continues its cutting-edge research, it emphasises collaboration among industry, laboratories, and government to drive innovation and reduce risks in the pursuit of hypersonic flight capabilities. 

This landmark project proves that innovative ideas, even those originating from students, can play a pivotal role in shaping the future of aerospace technology.

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