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Green Laser Powder Bed Fusion Enables High-Quality Additive Manufacturing of Regenerative Cooling Structures for Aerospace Thrust Chambers

Additive Manufacturing (AM) is a process that builds 3D objects by depositing material layer by layer. It provides exceptional geometric flexibility, which is often difficult to achieve through traditional manufacturing methods. The aerospace industry was among the earliest adopters of AM, which has gradually been applied to the rapid production of precision components such as rocket combustion chambers, engine nozzles, turbine parts, and aircraft rudder.

In today's aerospace manufacturing landscape, one of the key challenges is to efficiently produce components that meet increasingly stringent standards of precision and quality. These components often have Intricate geometries and multifunctional roles, requiring complex manufacturing processes and extended production cycles. With the rapid development of AM technologies in recent years, it is emerging as a vital solution to meet these evolving demands.

Figure 1 An example of a fully additively manufactured rocket thrust chamber assembly hot-fire tested at NASA Marshall Space Flight Center (Courtesy NASA)

Laser-based AM technologies are generally divided into two categories: Laser Powder Bed Fusion (LPBF) and Directed Energy Deposition (DED). Of these, LPBF has developed rapidly and is favored in both scientific research and industrial applications. LPBF uses a laser as the energy source to selectively fuse metal powder layer by layer on a powder bed. It offers key advantages such as tool-free production, direct one-step manufacturing, and high dimensional accuracy. These features give LPBF strong potential in aerospace, particularly for the integrated and lightweight manufacturing of critical components in liquid rocket engine thrust chambers, contributing significantly to overall reliability.

Figure 2 Live imaging of the green laser powder bed fusion (GL-PBF) process (Courtesy ADDIREEN)

LPBF can be used to produce structural components of thrust chambers, including combustion chambers, injectors, and nozzle extensions. Traditional manufacturing processes involve complex workflows, multiple process steps, and high costs, which pose challenges to meeting the needs of high-frequency rocket launches. By adopting LPBF as the primary AM technology, it becomes possible to achieve the integral formation of densely packed regenerative cooling channels within the combustion chamber walls, which significantly reduces lead time and costs. According to a case study by Paul Gradl (2022), using multiple metal AM technologies to produce a thrust chamber reduced the schedule from 18 months to 5 months (a 72% reduction), and cut the cost from $310,000 to $125,000 (a 60% reduction).

Figure 3 Comparison of manufacturing time and cost between traditional and AM approaches for rocket combustion chambers (Source: https://ntrs.nasa.gov/)

In recent years, LPBF-manufactured liquid rocket thrust chambers have been successfully developed and validated through functional testing. One representative application is the integrated fabrication of regenerative cooling channels inside the combustion chamber. These chambers incorporate dense, intricately internal cooling channels, which demand high manufacturing precision. LPBF enables the single-step fabrication of such components with fined internal features, eliminating the need for traditional welding or assembly. This not only enhances structural integrity but also improves thermal performance by allowing greater geometric freedom in channel design. For instance, a copper alloy combustion chamber jointly developed by Linde and Ariane Group was manufactured using LPBF. Through process optimization, the team achieved cost-effective manufacturing, reduced lead times, and maintained excellent product quality, demonstrating the suitability of LPBF for producing aerospace components with complex structures.

Figure 4 Copper alloy 3D-printed rocket combustion chamber by Ariane Group (Courtesy TCT Magazine)

However, the physical properties of certain materials can pose challenges to stability during the LPBF process. Combustion chamber liners typically use copper-based alloys with high thermal and electrical conductivity to support efficient regenerative cooling. Yet, copper's high reflectivity and strong thermal conductivity often result in poor laser energy absorption in traditional LPBF, leading to instability in the melt pool. This may cause low density, high porosity, and difficulty in manufacturing fine features, along with risks of cracking or delamination that compromise final part quality.

The laser absorption rate of materials is a key factor influencing the quality of LPBF performance. For pure copper and copper alloys, the absorption rate decreases steadily with increasing wavelength, dropping sharply above 550 nm. Comparative studies show that copper absorbs more than 10 times as much energy from green lasers (λ=532nm) than from infrared lasers ((λ =1064nm). Green lasers therefore offer a significantly more efficient energy absorption to the metal powder, improving melt pool stability and printing reliability. As a result, green-laser-based LPBF has emerged as an effective approach to address the challenges of printing highly reflective and refractory materials.

Figure 5 Absorption rate of various metal materials (%) (Courtesy ADDIREEN)

Compared to infrared lasers, green lasers offer several technical advantages, including a smaller spot size, higher energy density, a wider processing window, and reduced spatter during printing. These features make green lasers particularly well-suited for AM of demanding materials. To meet these needs, ADDIREEN has self-developed a green fiber laser specifically for metal 3D printing, which is integrated into its 3D printing systems. The multi-laser XH-M660G equipment is designed for producing large copper-based components, offering reliable and efficient green laser powder bed fusion (GL-PBF) solutions for aerospace and other high-performance applications.

Figure 6 ADDIREEN's Green laser metal 3D printing systems (Courtesy ADDIREEN)

The XH-M660G system is compatible with high-strength, high-thermal-conductivity aerospace grade alloys. It supports rapid material testing and process validation across various metals and enables direct one-step manufacturing of complex cooling channels. As shown in Figure 7, multiple thrust chamber products have been successfully manufactured using GL-PBF, showing outstanding build quality, consistency, and surface finish. The copper components achieve densities greater than 99.8%, with surface roughness (Ra) controlled between 4–8μm, allowing most surfaces to be used directly without additional finishing. This not only reduces post-processing effort but also improves product quality and shortens overall lead time.

Figure 7 Aerospace thrust chamber (Courtesy ADDIREEN)

GL-PBF technology offers broad benefits across multiple dimensions, including structural design, material utilization, quality control, cost reduction, and production efficiency. It has become an important method for the efficient and integrated manufacturing of complex aerospace components. ADDIREEN's GL-PBF systems provide exceptional forming precision and enable direct, high-speed manufacturing. They are particularly well-suited for high-heat-load structures like thrust chambers, paving the way for high-efficiency manufacturing and high-quality delivery.

￭ Thick-layer printing: Supports layer thicknesses up to 120 μm, enchancing build efficiency and reducing print time, making it ideal for batch production and rapid delivery.

￭ Material compatibility: Capable of stably printing highly reflective and refractory metals, especially pure copper and pure tungsten, while ensuring both precision and surface quality.

￭ Accelerated development cycles: Compared to traditional methods that may take over a month, the XH-M660G can produce a combustion chamber in as little as ten days, enabling faster testing and iterative development.

Figure 8 Liquid rocket engine combustion chamber 3D-printed by ADDIREEN (Courtesy ADDIREEN)

ADDIREEN remains committed to advancing the large-scale and industrial application of green laser metal 3D printing. By staying aligned with industry trends and continuously driving innovation, the company is focused on providing optimized GL-PBF solutions for high-end sectors. Looking ahead, ADDIREEN will continue to deepen its technologies in metal additive manufacturing, addressing challenges in material compatibility, printing efficiency, cost control, and post-processing optimization. Through ongoing process refinement and technology upgrades, ADDIREEN aims to further expand the application of green laser metal AM in high-performance materials, accelerating its integration into next-generation advanced manufacturing ecosystems.

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