A recent social media post caught my eye, something that could be described as the antithesis of LinkedIn. Instead of the typical self-congratulatory product launch or inflated performance claims, it was a blunt video clip of a combustion chamber tearing apart under pressure.
During hot-fire testing, an additively manufactured GRCop-42 combustion chamber failed and with it, offered a powerful failure analysis case study in the unforgiving physics of propulsion hardware. The incident demonstrates how a pause in build continuity can cascade into structural defects like lack of fusion and porosity, ultimately compromising mission-critical components.
At NASA’s Marshall Space Flight Center, Gabriel Demeneghi leads a team of material scientists working with advanced manufacturing and space-grade reliability. “My team is very diverse,” he says. “We have people doing microgravity experiments, in-space welding, alloy development, and full characterization: from optical microscopy to mechanical testing.”
Demeneghi’s own focus spans two fronts: supporting high-level PhDs in removing technical roadblocks and executing his own projects, which emphasize mechanical characterization, fatigue testing, and failure analysis. “We’re doing fatigue bending for materials that cannot sustain shear forces, like lunar regolith or nuclear fuel,” he explains.
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Public Data, Private Capabilities
Unlike many commercial laboratories, NASA’s work doesn’t stay behind closed doors. One core mission is to make material performance data publicly available, lowering barriers for smaller aerospace companies unable to fund exhaustive testing. “Large companies can spend millions on mechanical tests,” says Demeneghi, “but if you get a smaller company, they don’t have the same capability. So NASA takes on that burden and makes the data public.”
The goal is to build accessible databases of test results, from tensile strength and porosity to thermal cycling, enabling downstream users to make informed decisions about alloys, treatments, and design margins.
Failure analysis at NASA is as much forensic science as engineering.
For example, consider the United Launch Alliance tank failure. The scale of the wreckage, multi-meter fragments, means the process often begins with visual inspection and macro photography before moving into higher-resolution techniques like scanning electron microscopy.
As additive manufacturing technologies proliferate, Demeneghi’s team is tasked with determining their practical limits. “Everyone’s trying to sell the next best thing since sliced bread,” he says. “But we have to find the limitations.”
Much of that work centers on surface topography and microstructural anomalies. AM-produced parts often contain features that serve as fatigue crack initiation sites. “We look at everything from as-printed parts to post-processing, including heat treatments like HIP to reduce porosity,” he explains. Data from this process informs whether surface polishing or machining can mitigate defect risks without compromising the component.
Microgravity Metallurgy, and the Edge of AM Qualification
NASA’s material choices reflect the brutal thermal and mechanical regimes of rocketry. GRCop-42, a copper-based alloy designed to retain strength at high temperatures, is frequently used in combustion chambers. “On one side of a one-millimetre wall you have cryogenic temperatures; on the other, combustion at 400-700°C,” Demeneghi notes. GRCop retains 70–80% of pure copper’s conductivity while offering superior mechanical performance.
Where higher structural strength is required, alloys like Inconel or NASA HR-1 come into play. For nozzles and environments demanding extreme heat resistance, C-103 (a refractory niobium alloy) is preferred. “It’s not one alloy fits all,” he adds. “It’s always about designing for the application.”
When it comes to fatigue failure, NASA’s strategy is application-specific. “For combustion chambers, we’re concerned with thermal mechanical fatigue, especially at low cycle strain rates between 0.5% and 2%,” says Demeneghi. “But for turbine blades, it’s high-cycle fatigue that matters.” While the team tailors test regimens to expected use, they still perform a full characterization to ensure broad usability of the dataset.
The relationship between materials and design in space-grade engineering remains tightly coupled. “It’s a chicken-or-egg situation,” says Demeneghi. One steel alloy resistant to hydrogen embrittlement, possibly A286, illustrates the point. “It’s not printable,” he explains. To address this, NASA developed HR-2 (Hydrogen Resistant alloy version two) tailored for compatibility with additive processes while retaining performance under hydrogen-rich conditions.
GRCop and the Heat Barrier
The pursuit extends to cost-driven substitutions for high-temperature refractory alloys. While GRCop-42, a copper–chromium–niobium alloy, is increasingly deployed in combustion chamber builds, its costs remain a concern. “Niobium is extremely expensive,” Demeneghi notes. “But if you need strength at high temperatures, you need that Cr–Nb ratio. Both have low solubility in copper and high affinity to each other, forming a precipitate that reinforces the microstructure.” Copper–chromium alone breaks down under elevated conditions. “It’s only effective to around 500°C. Then it dissolves and loses strength,” he says. NASA is actively engaged in the search for both alternatives and works to engineer new materials that maintain the required performance.
Microstructure Control at High Temperatures and 3D Printing in Space
Refractory AM systems present fresh challenges for microstructure stability. Beyond copper alloys, NASA is also exploring materials like tungsten–tantalum carbides and ceramics, which require extreme print temperatures to prevent particle agglomeration. “You need a 50% overlap during the build to keep particles dispersed,” says Demeneghi. “But you can’t do that at the contour layer, which leads to clustering.”
The team has yet to reach the elusive goal of full control over microstructure evolution in additive builds. “Additive was supposed to be fully controllable. Some people showed results, but I don’t know if they were ever replicated.”
NASA’s ongoing research includes direct comparisons between welds made in space and on Earth. While the results are not yet public, Demeneghi hints at future findings. “We’re looking at how heat transfer and solidification differ with gravity. Microgravity may lead to more homogeneous materials, but we don’t know yet.”
Short-duration zero-G experiments via parabolic flights are limited to fast-solidifying systems, like dental amalgam, due to the tight 30-second window. To replicate the full spectrum of space conditions (vacuum, radiation, thermal extremes, etc.) NASA is building environmental chambers.
Demeneghi remains cautious: “I don’t think microgravity is better or worse. It’s just different. It will require full recharacterization.”
A prominent trend in AM for spaceflight involves combining multiple processes to sidestep scale and resolution constraints. “We can do fine features with laser powder bed fusion and then add bulk via directed energy deposition (DED),” says Demeneghi. “Or combine additive with subtractive or casting.” Laser powder bed retains advantages due to finer powders, typically half the size of DED, and tighter surface tolerances. “You get fewer surface discontinuities,” he explains. But pushing this process to propulsion-scale components is where qualification hurdles emerge.
Failure, Restart, and Process Control
Back to that aforementioned nozzle failure in a chamber, which provided a dramatic reminder of additive’s sensitivity to production variables. “There was an interruption during the build, possibly a power outage or powder refill, that led to lack of fusion, porosity, maybe oxidized powder,” Demeneghi says. “The restart protocol wasn’t followed properly.”
Witness specimens printed under controlled restart conditions showed no defects, affirming that it was a procedural oversight, not a fundamental flaw with laser powder bed fusion. Asked about the role of thermal simulation in additive manufacturing, Demeneghi indicates that, while useful, simulation alone cannot replace rigorous testing. The complexity of material behavior, particularly under extreme conditions, still requires empirical data. “You need tight control, but you also need verification. Models are useful tools, but they can’t capture everything.”
Establishing standards and producing test coupons remains central to mitigating risk. “With every fabrication, maybe produce witness specimens and test at different build heights,” he suggests. He is pragmatic regarding the role of simulation in additive manufacturing. “It’s a trust but verify situation,” he says. While physics-based models help, they are not infallible. “We can predict fatigue failure very well, and still 90% of failures are due to fatigue. So predicting is not always correlated to avoiding it.”
He also highlights the pace mismatch between private firms and government agencies. “We cannot work at the pace that they work. We have a lot more red tape, but also people with 40 years of experience. It’s a good partnership. They move fast, and we help with qualification.”
Replicability vs. Repeatability and Next-Gen Hardware Needs
In his view, NASA’s greatest contribution may be in its measured, test-heavy culture. Private launch firms may be able to move faster, but Demeneghi emphasizes the value of deep materials knowledge. “We’re always involved. Weekly meetings with SpaceX and Blue Origin. They benefit from the experience we bring, even if we don’t share their tempo.”
While Demeneghi focuses on characterization rather than machine development, he sees AM’s bottlenecks as lying less in hardware and more in procedural control. Ultimately, he views AM in propulsion as moving fast, but only as fast as its weakest parameter allows. “You need to control the process very tightly. Especially in rocketry. Loads are extreme. There’s no room for error.”
Personal or professional opinions expressed in this article are Gabriel Demeneghi’s and do not, in any way, represent the opinion or policy of NASA.
Join AM leaders on July 10th at Additive Manufacturing Advantage: Aerospace, Space & Defense. Spaces are limited for this free online event. Register now.
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Featured image is series illustrating how the thrust chamber assembly (TCA) failed during testing. Photo via ScienceDirect.
