When it comes to exploring space, we’ve only begun to scratch the surface. Humans have walked on Earth’s moon and landed rovers on Mars. But there is still so much of our own solar system to explore and discover – and that’s not even including what lies beyond in the larger galaxy.
While deep space exploration, manned missions to Mars, and other space missions may still seem like science fiction that is lightyears away, the technologies that will enable these missions are being developed and adopted today. And one of the most fundamental technologies that will enable Americans – and the rest of humanity – to reach beyond what we’ve already accomplished in space is the additive manufacturing advancements being made by NASA and its partners in private industry and academia.
Additive manufacturing is opening the door to new materials that are more heat resistant, stronger, more conductive, and more refractive. It’s enabling these new materials to be fabricated into essential spacecraft components. And it’s making the fabrication of components faster and cheaper.
In the future, additive manufacturing may even enable the construction of spacecraft in space.
To learn more about the ways additive and advanced manufacturing are changing the way we innovate and construct everything from spacecraft to propulsion systems, we went right to the source. We recently sat down with one of the individuals driving additive manufacturing experimentation and adoption within NASA, Paul Gradl, a Senior Propulsion Engineer that also serves as Principal Investigator and Co-Principal Investigator on several metal additive manufacturing projects at NASA’s Marshall Space Flight Center.
Here is what Paul told us:
GovDesignHub (GDH): What is the focus of NASA’s Marshall Space Flight Center? And, what is your role?
Paul Gradl: NASA Marshall Space Flight Center’s core capabilities include launch vehicles, propulsion systems, and advanced manufacturing and development. For more than six decades, NASA and the nation have relied on Marshall to deliver its most vital propulsion systems and hardware, flagship launch vehicles, world-class space systems, state-of-the-art engineering technologies, and cutting-edge science and research projects and solutions
I am a Senior Propulsion Engineer in a component design and development technology branch within the Propulsion Systems Department. Our group is responsible for the lifecycle of liquid rocket engine components such as combustion chambers, nozzles, injectors, turbomachinery, and ignition systems. We work development of early-stage technology and infusion into flight programs and all aspects as it relates to the hardware. This includes leading the conceptual and detailed design, analysis, integrating across detailed disciplines, manufacturing, testing of engine components, and documentation to allow adoption into industry.
I am Principal Investigator (PI) and co-PI on several projects that involve the application of metal additive manufacturing (AM) to these components. This includes the Rapid Analysis and Manufacturing Propulsion Technology (RAMPT) Project, Long Life Additive Manufacturing Assembly (LLAMA), and several industry partnerships under Space Act Agreements and collaborative opportunities.
We develop AM technologies for propulsion components, materials, and supplemental processes to infuse into NASA and other government missions as well as commercial space missions. We also lead many efforts involving the advanced manufacturing ecosystem with industry and academia partners to advance innovation and the manufacturing supply chain.
I also help educate industry and academia on the application of AM for propulsion and am involved in several industry professional and educational organizations advising on AM, teaching courses, and currently writing a book on metal AM with several colleagues.
GDH: Advanced manufacturing methods are making their way into many areas where traditional manufacturing has existed. How do you see 3D printing, additive manufacturing, and other methods aiding your mission?
Paul Gradl: Additive manufacturing is changing how we approach design and manufacturing for our propulsion components. The key benefits are affordability, schedule reduction, and the ability to create complexity within designs and new materials that is not possible with traditional methods.
We can manufacture and create prototypes significantly faster than traditional manufacturing techniques. In some cases, we have seen cost reductions by more than 50 percent and lead time reduced by up to 10x. This is substantial, but we certainly have a lot more learning about the AM technologies to understand the different AM processes, materials, design complexities, performance relationships to each other, and how to safely implement and certify.
We are able to conduct component testing at a substantially higher rate aided by faster hardware manufacturing enabled by AM. This allows a shortened development cycle and can provide more immediate development data to our direct projects and commercial space partners.
GDH: We recently talked with a firm called Elementum 3D which specializes in producing materials for advanced manufacturing. It seems that new alloys are providing greater capabilities for the alloys used in AM. What does that look like at NASA?
Paul Gradl: New and enabling materials will be key to some of our future space missions. Early metal AM used many traditional alloys that were difficult to process and had very long lead times in their wrought forms such as castings and forgings. Some of these materials are not the most “AM-friendly,” meaning they can be prone to cracking and other challenges in AM processing. While many of these AM alloys are commonly used, they may not be the optimal solution for all design requirements and the overall materials available for metal AM is limited.
Starting in 2014, NASA led an effort to advance GRCop-84, a copper-chromium-niobium alloy for application to combustion chambers. The team successfully printed GRCop-84 using laser powder bed fusion and hot-fire tested several chambers. We have since advanced another alloy developed at NASA Glenn Research Center called GRCop-42, which improves conductivity over GRCop-84, which is important in high heat flux combustion chambers.
“Additive manufacturing is changing how we approach design and manufacturing for our propulsion components. The key benefits are affordability, schedule reduction, and the ability to create complexity within designs and new materials that is not possible with traditional methods.” – Paul Gradl
Seeing the need for new alloys, NASA continues to develop processes for other alloys such as NASA HR-1, a strength material for use in high-pressure hydrogen environments, developed at Marshall. Some colleagues are also developing refractory alloys using AM, which have advantages in extreme temperature applications.
There are several other alloys we are exploring including new superalloys and aluminum-based materials, designed specifically for AM. With each of these alloys, we must develop and characterize the AM process to build specimens and components, but also demonstrate hardware in an actual rocket engine environment.
GDH: What is Directed Energy Deposition? What advantages does this bring to bear for NASA?
Paul Gradl: Directed Energy Deposition, or DED, is a category of metal AM that allows for freeform manufacturing “outside” of a powder build box. There are several types of DED that are categorized by the feedstock and the energy source. The feedstock can be metal powder or wire and energy sources consist of a laser, electron beam, or electric arc.
The DED techniques allow us to manufacture parts significantly larger, although complimentary, to powder bed fusion techniques. We use this to build components that are final shape or near-net shape, which can replace a casting or forging.
We have fabricated complex parts such as channel-cooled nozzles with thousands of thin-wall integral channel features at 1.5 meters in diameter and 2 meters in height. This large scale also provides the potential for significant cost and schedule reductions over traditional manufacturing, where lead times can be months or years. For example, a laser powder DED nozzle pathfinder was fabricated in 90 days, which is a significant reduction compared to traditional methods and can reduce the number of parts by two orders of magnitude.
The DED processes allow for high deposition rates and the ability to use multiple materials within the same build. This provides new design opportunities to further optimize components for mass reduction by building, or depositing, material upon itself.
GDH: What concerns, or issues, need to be overcome to see new alloys and methods fully integrated into space flight manufacturing?
Paul Gradl: AM does not need to be used for every component application. It should be used where it makes sense. Many traditional techniques will be better suited than AM. It needs to be properly traded for each application.
While there are many uses for AM, we must apply it safely and test with rigor to understand these materials and new processes. Each AM process produces slightly different grain structures due to different heating and cooling rates, which can result in varied properties. This requires extensive characterization of the material along with heat treatments, mechanical and thermophysical testing, non-destructive evaluations, and other post-processing operations.
New and enabling materials will be key to some of our future space missions. Early metal AM used many traditional alloys that were difficult to process and had very long lead times in their wrought forms such as castings and forgings. – Paul Gradl
There is complementary work to be completed on post-processing, such as surface finishes of AM parts. The as-built AM surface roughness tends to be higher compared to traditional manufacturing, such as machined surfaces. This can impact end-use performance of these materials or functional performance of the fluids or heat transfer, so needs to be well characterized and understood.
Other efforts are needed, including modeling and simulation, to help better inform AM build strategies and reduce process failures. NASA is also leading efforts to develop standards to certify and qualify the AM processes for hardware used for human spaceflight.
GDH: How are partnerships with the private sector and with universities helping to advance technologies to aid your mission?
Paul Gradl: NASA is engaged in many public-private partnerships and academia collaborations to accelerate AM technology, including widespread adoption. Through these partnerships, we are able to increase our chances of success by sharing ideas and resources to better understand the technology and advance the supply chain.
Under our RAMPT project, NASA has a partnership with Auburn University. Through this partnership and other NASA investments, we are collaborating with over 20 U.S. companies that invest a minimum of 25 percent cost share of their own resources to develop AM and supplementary technologies for large-scale thrust chambers. These collaborations aim to help establish a healthy supply chain for NASA and commercial space use to achieve our missions.
The DED processes allow for high deposition rates and the ability to use multiple materials within the same build. This provides new design opportunities to further optimize components for mass reduction by building, or depositing, material upon itself. – Paul Gradl
NASA has several collaborative contract and grant efforts with industry partners to develop new alloys, techniques, modeling, and larger-scale AM. NASA also uses Space Act Agreements to help the commercial space sector and other industrial companies benefit from the technology investments NASA has made in AM.
GDH: What do you see is the future impact that AM will make on space flight?
Paul Gradl: Technology drives exploration. NASA is investing in lower technology readiness level (TRL) processes and materials and taking on the early technology development risk. We collect data and share it with industry to help enable new materials and implementation of the technology into propulsion applications.
As a result, commercial space companies have used AM to reduce their development cycles. Advanced manufacturing helps reduce overall vehicle development and production costs.
To learn more about advanced manufacturing, fill out the form below to download a complimentary copy of, “Groundbreaking INNOVATION: Additive Manufacturing for Government Agencies.”
