The aerospace industry was one of the first places to embrace additive manufacturing (AM). As early as 1989, Aerospace & Defense (A&D) companies started to use 3D printing technologies. A couple of decades later, the use of additive manufacturing within A&D has increased substantially, fuelling the rapidly expanding multi-billion market.
Why? AM offers aerospace engineers a unique set of opportunities like the fabrication of low-cost parts, hyper-customization, low cost-prototyping, and fast turnaround times. Within the Aerospace and Defense industry, 3D printing technologies are commonly used as a rapid prototyping solution to speed up product development or as a manufacturing technology to produce end-use parts.
In short, the technology presents aerospace companies and institutions with a very appealing value proposition. Engineers can use additive manufacturing to create more robust and lighter parts than the parts made using traditional manufacturing. Logically, in a design world where weight, cost, and performance are directly correlated, AM emerges as a powerful tool.
Our previous article introduced the role of additive manufacturing within aerospace, focusing on the realms of aeronautics, i.e., companies like GE Aviation, Boeing, and Airbus.
Throughout that overview, we explored how aerospace engineers use various 3D printing materials and additive manufacturing techniques to fabricate advanced engineering materials and complex geometries. This article will continue this trend. Nonetheless, today we will focus primarily on AM applications in the military and astronautics.
Additive manufacturing offers military forces around the world rapid tactical solutions in the field. From on-demand UAVs to essential weapons components, rapid manufacturing is slowly being embraced by the military. Beyond the earth's atmosphere, 3D printing technologies are accelerating the capabilities of astronautical engineering. Private institutions and space agencies are placing big bets on additive manufacturing. Not only is it helping us design better rockets, but AM could also become a vital tool in humanity's collective goal of colonizing Mars. Here are some of the most compelling examples of AM adoption within this industry.
The Australian military is testing supersonic 3D Deposition printers.
In August of this year, the Australian Army tested a metal 3D printer's capabilities and usefulness during a successful two-week field trial. During the "practice mission," soldiers from the 1st Combat Service Support were given access to a novel 3D printer developed by SPEE3D, an Australian manufacturer of metal additive manufacturing technology.
Using the "WarpSPEE3D" Supersonic 3D Deposition (SP3D) metal 3D printer, soldiers were able to print crucial metal parts for equipment and metal tools while in the field quickly and at low cost. Compared to other common additive manufacturing techniques used to manufacture functional parts like Selective Laser Melting (SLM), or Direct Metal Laser Sintering (DMLS), SP3D is much faster.
During the SP3D process, a rocket nozzle fires metal powder onto the carrier plate at around three times the speed-of-sound. Adhesion of the metal particles for your 3D model to the plate does not happen through the process of melting. Rather, it is caused by the extremely high kinetic energy of the ejection.
In the case of SPEE3D and their metal 3D printer, a "rocket engine" is used to accelerate gas, creating air speeds of approximately 950 m/s. Within the printer, this causes the powder to be launched through the supersonic nozzle at tremendous speeds. Upon dispersion from the nozzle, the metal powder makes contact with the build plate. The powder's kinetic energy keeps the powder in place, causing it to build up into a solid mass layer by layer without changing phase.
The SP3D additive process used by the WarpSPEE3D large format metal 3D printer is 100 to 1000 times faster than traditional 3D metal printing. This metal printer has a deposition rate of 100 g/min, a maximum part build-size of ø 1000 x 700mm, and a top part weight of 45 kg.
Using the SP3D additive process, the Australian Army was able to produce industrial components in a matter of hours that would typically take 6-12 months using traditional manufacturing methods. Specialized multi-tools for armored vehicles or essential metal mounting brackets for bulk fuel support modules could be printed on demand while in the field.
The US Marines are using Atomic Diffusion Additive Manufacturing to create on-demand weapons.
United States soldiers, part of the III Marine Expeditionary Force stationed in the Indo- Pacific are utilizing metal additive manufacturing to produce crucial vehicle and weapons parts. Again, part repairs can be costly. Additionally, repairing components for vehicles and weapon systems usually equates to milling parts out of blocks of metal. This can be both wasteful and time-consuming.
Known as subtractive manufacturing, this process often requires specialized tools and high levels of monotonous precision. Metal 3D printing technologies offer US soldiers a solution to their problems.
This past year the Marines started incorporating metal additive manufacturing in their tactical environment. Using a Metal X 3D printer by the Boston-based company Markforged, the team of soldiers rapidly manufactured gauges for .50-caliber machine guns, sockets for wrenches, and a piece to test weapon optics at the armory.
ADAM sits at the intersection of extrusion printing and metal injection molding. Compared to the WarpSPEE3D printer mentioned above, the Metal X uses a proprietary process known as Atomic Diffusion Additive Manufacturing (ADAM) to print stainless steel, tool steel, Inconel 625, Copper, and Titanium.
ADAM prints parts layer by layer using metal powder contained in a plastic binder. The entire part is sintered at once to create exceptional strength. Furthermore, printing metal powder bound in a plastic matrix eliminates the safety risks associated with traditional metal 3D printing while enabling new features like closed-cell infill for reduced part weight and cost.
Overall, according to the Markforged team, ADAM is 10x less expensive than other more common forms of metal additive manufacturing. In many cases, additive manufacturing offers custom solutions or low-volume production in a tactical environment. The growing accessibility of metal 3D printing technologies is helping to facilitate the mass adoption of AM within the military. The long-term goal for various military forces across the globe is to manufacture parts as close to a warzone as possible. Additive manufacturing will help get them there.
Robotics 3D printers are being used to construct strategic buildings.
The US Military is exploring a wide range of experimental 3D printing solutions. These approaches include 3D printing meals for soldiers, field-ready drones, 3D-printed grenade launchers, 3D-printed ship hulls, skin 3D printers for rapidly healing wounds. One growing area of additive manufacturing within the US military is rapid construction.
3D printing technologies are currently being used as a new construction technique. Using oversize printers, startups around the world are able to construct functional living spaces cheaply and quickly. The US military is currently using rapid construction to build small strategic buildings while in the field.
In August of this past year, the United States Marines Defense Innovation Unit partnered with the additive manufacturing construction technologies company ICON to help integrate AM into the military. Utilizing 3D printing robotics, software, and cement-based materials, ICON has been able to provide rapid, affordable, and low-cost housing in select regions around the world.
The Marines are looking to leverage this 3D printing technology to supply rapid construction capabilities to support military crisis response efforts. In their collaborative project in August, ICON was tasked with fabricating a structure capable of hiding military vehicles.
Using ICON's novice-friendly, tablet-operated robotic printer, integrated material delivery system, and proprietary cement mixture, the team could print a durable structure 7.29 cm in length x 3.96 cm x 4.52 cm height. All of this was done in just under 36 hours using a team of 8 people.
The project was completed thanks to the rapid construction company's massive 3D printer, The Vulcan.
The flagship 3D printer uses an additive manufacturing technique that shares some similarities with Fused Deposition Modeling (FDM) printing. Their Lavacrete 3D printing material has some unique properties:
It has a compressive strength of 6,000 MPa.
The material is reliant, capable of withstanding extreme weather conditions.
Lavacrete has been designed to take advantage of the high thermal mass of concrete to maximize both living comfort and efficiency.
Overall, the ICON wall system created using Lavacrete removes the need for traditional cladding, framing, and sheetrock. The cement-based mixture is designed to be explicitly pumped for the Vulcan's extruder. Logically, this helps slash construction costs.
The printer itself weighs 1723 kilos and can print up to 185 sq meters. Its robotic gantry system supports the printer head along the X/Y axis as it moves around to print the intended building.
The Vulcan only needs 3-4 people to operate it and can print wall structures up to 2.5 meters tall and print 17cm a second. The US military is currently exploring 3D printing technologies like the one provided by ICON to create operational concrete barracks and improvised bridges while out in the field.
NASA is pushing the boundaries of additive manufacturing.
Turning our gaze to the stars, the National Aeronautics and Space Administration, or NASA, has become one of the leading proponents of additive manufacturing. 3D printing technologies and 3D printing materials are weaving their way into the DNA of missions outside of earth, becoming an essential part of astronautical engineering.
In one of the most compelling examples, NASA's Rapid Analysis and Manufacturing Propulsion Technology project (RAMPT) is advancing the development of an additive manufacturing technique to 3D print rocket engine parts using metal powder and lasers.
The novel additive technique looks to reduce overall mission and support costs, associated schedules, and improve performance of rocket thrust chamber "assemblies."
Thrust chamber assemblies are the most costly parts of a rocket engine. Comprising of a combustion chamber, nozzle, and joints, thrust chamber assemblies are exceedingly complex and take a long time to manufacture. Moreover, they are the heaviest parts of the rocket. RAMPT's additive manufacturing method is called Blown Powder Directed Energy Deposition. This AM technique is able to produce complex components like engine nozzles with internal coolant channels and combustion chambers.
The blown powder directed energy deposition method developed by NASA injects metal powder into a laser-heat pool of molten metal. For the process to work, the blown powder nozzle and laser optics are consolidated into a print-head.
Attached to a robot, the print head moves in a set pattern determined by a computing printing specified component layer by layer. This fabrication method has a wide range of advantages, like the ability to fabricate massive components limited only by the size of the room in which they are created. In one instance, NASA was able to print a copper combustion chamber covered with a carbon fiber composite wrap resulting in a weight savings of up to 50%.
Additionally, NASA used this AM method to produce nozzles 101 cm in diameter and standing 96 cm tall with fully integrated cooling channels. Compared to more traditionally welding methods that take nearly one year, the nozzle was fabricated in just 30 days. NASA's Space Launch System is working to certify the blown powder directed energy deposition fabrication process for future spaceflight missions to the Moon and beyond. The day could come soon.
In 2019, NASA successfully hot-fire tested a 3D-printed copper alloy combustion chamber capable of 2,400 lbs of thrust. This test successfully demonstrated that the materials are durable enough to withstand associated heat and structural loads.
Additive manufacturing will lighten the load of space travel.
Aside from being used as a useful tool to optimize weight in systems built to reach space, AM could be used to solve the challenges of long-duration space flight. Printing tools, parts, and food in zero gravity is no longer reserved to just the realms of science fiction.
Astronauts traveling to the space station need to have a place to eat, sleep, relax, and exercise during their extended stay. According to NASA, to make all of this possible, 3175 kg of spare parts are sent to the space station annually, with an estimated 1315 kilograms of hardware spares are stored aboard the station with another 17690 kilos ready to fly if needed. This is an ok temporary solution. Nonetheless, it is not practical for future missions to the Moon and Mars. NASA believes 3D printing technologies could provide a solution.
The ISM project at NASA Marshall Space Flight Center (MSFC) is currently testing various AM technologies in zero gravity. In 2014, the team sent the first 3D printer to the International Space Station. Developed by their commercial partner Made in Space, the printer uses the Filament Fabrication (FFF) process. The method works by feeding a continuous thread of plastic through a heated extruder and onto a tray layer by layer to create a three-dimensional object.
During their 3D Printing in Zero Gravity study, NASA was able to produce dozens of parts while on ISS. The investigation revealed that microgravity had no engineering-significant effects on the process.
Building off of this project's success, Made in Space created the Additive Manufacturing Facility (AMF). The AMF can fabricate parts out of a wide variety of thermo-polymers, including engineered plastics, while on the ISS.
Some of the prints included an antenna part, an adaptor to hold a probe in an air outlet on the station's oxygen generation system, and a part to connect two free-flying robots used for research on the space station.
3D printing food in space could become a reality in the near future, too, helping reduce travel weight and costs.
As of right now, NASA supplies ISS astronauts with individually wrapped, shelf-stable dishes, many of which simply require heating in the ISS food warmer. Temporary residents also have access to freeze-dried side dishes and beverage packets that require hot or cold water. However, these only last six months and refrigeration is considered "an inefficient use of precious resources." Finally, "space food" is notorious for being unappetizing. 3D printing could change this, taking space food further.
Additive manufacturing could open the doors to rapid food creation that provides astronauts with precise, personalized, 3D-printed nutrition in microgravity. One company leading the charge is Columbus and Silicon Valley-based startup BeeHex. The flagship "Chef 3D robot" can print 30 cm pizzas in less than five minutes. Cartridges in the printer are filled with all the necessary ingredients. Resembling FDM or FFF printing, the robot's nozzle starts layering a liquefied dough onto a build plate followed by a set group of toppings, sauce, and melted cheese.
However, unlike traditional additive manufacturing technologies, Chef 3D relies on pneumatic systems to move ingredients around. BeHex is working with NASA to bring pizza to space. If you are not interested in having pizza every day, 3D printed meats could be a viable option. In 2019, food-tech startup Aleph Farms oversaw the growth of meat in space for the first time, with the help of a 3D printer.
To do this team extracted cells from a cow through a small biopsy back here on earth. These cells are placed in a nutrient broth in closed vials. Finally, the cells were inserted in a magnetic printer from the Russian company 3D Bioprinting Solutions, on the ISS. Here the printer replicated those cells to produce consumable muscle tissue. No one consumed the meat on the space station, but it was an impressive proof of concept.
Ultimately, AM will become an essential part of future exploration missions, allowing for those missions to be more independent of Earth. Being able to print food, supplies, and tools on our own could help us to get to the Moon and beyond.
Polylactic Acid with aluminum particles could be used as rocket fuel in the future.
Researchers from James Cook University in Australia are 3D printing fuel grains to power a hybrid rocket motor. As a response to companies' increase in private space exploration, the novel process could be imperative to meeting the demand for propellant energy. The team printed a wide range of thermoplastics like ABS, PLA, PP, ASA, PTEG, and AL circular grains with initial dimensions of 100mm in length, 20mm in diameter, and a 6 mm straight circular combustion port.
"We wanted to explore the viability of using commercially available 3D printing materials in the manufacture of hybrid rocket fuel grains. We knew that the common plastic ABS had shown promise, so we decided to test that against other compounds," says Dr. Antunes, one of the lead researchers on the team.
During the tests, two fuel grains of each material were subjected to static burns for three seconds inside the motor. Grains were then dissected for further analyses. The team reported that there were noticeable differences between the higher-performing materials and the common plastics. Though the AL showed poor performance, the researchers believe it shows potential.
Companies like Rocket Crafters Inc have begun commercializing their Hybrid Rocket Engine (HRE) technology. The companies are developing 3Dprinted rocket fuel technology to produce feedstock rocket fuel from a blend of thermoplastic and high-energy nanoscale aluminum particles. The rocket fuel uses nanoscale particles of pure aluminum, which is highly reactive.
Future colonies could be 3D printed using moon dust.
3D printing has the added benefit of operating with little to no human involvement. You could send a 3D printer to the Moon or Mars ahead of the scheduled crew in theory. There the automated 3D printer would start manufacturing important parts, components, and living spaces.
Even more so, rather than use specialized filaments, we would engineer components using the materials found on the planet. Thanos Goulas and his colleagues at Additive Manufacturing Research Group at Loughborough University are exploring 3D printing with moon dust. The surface of the Moon is covered with a material called regolith.
Regolith is a loose, powdery material formed from millions of years of meteors bombarding the Moon's surface that is soil-like in nature and is less than a few millimeters across. Goulas believes that this material could be used as a filament for our moon-based structures. Back here on earth, the team explored the additive possible using JSC-1A Lunar regolith simulant powder.
To create their moondust components, the team uses Laser Melting (LM) type additive manufacturing. The laser fuses grains of regolith together using a minimal amount of heat to form a solid thin slice of material. By repeating this process layer by layer, the team is able to create 3D dimensional objects. Layers of the object have a 1mm thickness. Though this method is not ideal for the fabrication of large structures, it could be useful for the creation of high-detail components like dust or water filters, items that need holes less than a micron.
There could be another route towards multi-planetary additive manufacturing. In 2019, New York-based design agency AI SpaceFactory was awarded the top prize in a NASA competition to 3D print a habitat that could be used on the Moon or Mars. Dubbed Marsha, this tall and slim abode was designed to be fabricated on a vertically telescoping arm attached to a rover.
Unlike some of their concrete competitors, the building is made of a biopolymer basalt composite, a biodegradable and recyclable, derived from natural materials found on Mars. Marsha's tall and elongated design is to reduce the need for construction rovers on unfamiliar terrain. The structure only took 30 hours to print and required no human assistance. Automated 3D printed structures like these could play a vital role in humanity's pursuit toward colonization.
An ever-evolving relationship
From the airfield to the Moon, additive manufacturing will continue to play an evolving role within the aerospace industry, helping the industry reach new heights. As we mentioned in our previous article, additive manufacturing has its limitations. AM still falls behind subtractive manufacturing in areas like mass production and part quality control. Nonetheless, the AM process has moved beyond just a rapid prototyping tool and has gone on to become the go-to method for custom low-production end parts.
This emerging technology will continue to fuel the revolutionary innovation within aerospace. It will be interesting to see how additive manufacturing and aerospace engineering’s closely knitted relationships will continue to blossom over the next decade.