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Although we are not yet living in the futuristic world many 20th-century science-fiction writers predicted, many recent technological advances were inspired by the stuff of fantasies.

Inventions such as GPS, Bluetooth headsets, tablet computers, automatic doors, big screen displays, real-time universal translators and teleconferencing among others all owe their genesis to Star Trek. Among the technology converted from fiction into real science is the replicator from Star Trek, a device capable of replicating machine parts, clothing, foodstuffs of acceptable “nutritional value” and even alcohol. Star Trek coined the scientific term for this technology: 3-D printing.

The Stockholm International Peace Research Institute (SIPRI) defines Additive Manufacturing (AM), or ‘3-D printing’, as processes in which layers of material are deposited and bonded together by a machine, to form an object of nearly any shape. The most widely known AM machines use plastic polymers in a process similar to the functioning of a common inkjet printer, thus often referred to as ‘3-D printing’.
Though not quite as capable as the replicator, the potential benefits of 3-D printing in aerospace and defence include waste reduction during production, as well as increases in production speed, shape complexity, eco-friendliness, and logistical efficiency, among others.

With such high hopes for 3-D printing technology, it’s no surprise then that aerospace and defence 3-D printing market is expected to reach US$3 billion at a CAGR of over 25%, during 2018-2023, the forecast period, according to a Mordor Intelligence study.

The market is mainly driven by the growing demand for lightweight components and parts, lightweight raw materials, such as steel, titanium, and a range of plastics that are used to increase fuel efficiency and the overall performance of an aerospace component. These plastics and raw materials help to shorten the supply timeline and, therefore, improve the performance of 3-D-printed aircraft parts and components for manufacturing aircraft, the report added.

The Present Scenario

3-D printing might be a disruptive force today, but it is not a new technology. The concept of 3-D printing has existed since the 1980s. Charles Hull, the father of 3-D printing, invented the solid imaging process known as stereolithography, the first commercial 3-D printing technology.

Over the last decade, the technology has advanced substantially. In 2015, Raytheon announced that “the day is coming when missiles can be printed”, having already created nearly every component (about 80%) of a guided weapon using additive manufacturing. The components include rocket engines, fins, parts for the guidance and control systems, and more.
The progress is part of a companywide push into additive manufacturing and 3-D printing, including projects meant to supplement traditional manufacturing processes. Engineers are exploring the use of 3-D printing to lay down conductive materials for electrical circuits, create housings for the company’s revolutionary gallium nitride transmitters, and fabricate fins for guided artillery shells.

A Marine makes small adjustments to a 3-D printer before loading a design during a class at Marine Corps Base Camp Lejeune, NC, 2 June 2016. (Photo: Cpl. Justin Updegraff, USMC )

Earlier this year, the US Air Force announced that it is looking into additive manufacturing to expand its hypersonic flight capabilities. Scientists with the Air Force Research Laboratory Aerospace Systems Directorate recently entered into a Cooperative Research and Development – Material Transfer Agreement with HRL Laboratories to test additively manufactured silicon oxycarbide (SiOC) materials. The geometric complexity of components that can be produced through additive manufacturing in conjunction with the refractory nature of ceramics holds enormous potential for a variety of future Air Force applications. One such possible application is hypersonic flight, which exposes materials to extreme environments, including high temperatures.

The United States may be paving the way for 3D printing, but American allies are quickly catching up to the technology. Earlier this year, the Royal Australian Navy announced that it was adopting additive manufacturing techniques to solve problems of regular occurrence onboard the HMAS WARRAMUNGA. According to the Navy, the WARRAMUNGA recently took full advantage of the new equipment when the ship experienced an issue with a pressure sensor. Able Seaman Electronics Technician Luke Pozzi used the new equipment to design, print and fit a temporary replacement part at sea, restoring full functionality, the statement explained. “We looked at our options and thought ‘why not just print a fix’ and within 24 hours we were able to print and fit the part”, said Able Seaman Pozzi. “Initially we weren’t sure if it would work, so it was quite a buzz when the system came up to the correct pressure.”

On-board tutorials for the new equipment were developed and tailored by the ship’s engineers who conduct weekly workshops on Computer-Aided Design (CAD), 3-D printing and software development. This workshop is based around a 3-D printer, new electronic kits and various civilian software tools.

On the other side of the world, the Netherlands Aerospace Centre (NLR) announced late last year that it had produced a metal compressor wheel for a microturbine using 3-D printing techniques and successfully tested the compressor wheel at speeds of up to 200,000 revolutions per minute.

The NLR measured an existing compressor wheel using a 3D optical scanner and then redesigned it using special software. The redesign was aimed at ensuring printability and weight reduction rather than any aerodynamic improvements. During the redesign process, calculations were performed to determine the stress levels due to the weight reduction under the expected operating conditions, the NLR explains on its website.”With this new 3-D-printed compressor wheel, NLR has taken a new step in the field of additive manufacturing. After producing a statically loaded component for the NH-90 helicopter in late 2016, further progress has now been made in applying 3-D printing techniques to a rotating component subjected to critical loads. NLR’s Metal Additive Manufacturing Technology Centre (MAMTeC) in Marknesse, the Netherlands, offers advanced 3-D scanning and printing capabilities,” the statement added.

The Promise of 3-D Printing

A cutaway model showing the printable components of a small missile. (Photo: Raytheon)

The tactical advantages of 3-D printing are enormous. Growing at breakneck speed, 3-D printing could essentially alter how militaries around the world operate. Or as the US Army Research, Development and Engineering Command envisions it: “Additive manufacturing will allow soldiers deployed in remote outposts around the world to ‘print’ virtually anything they need, from food to shelter to weapons or even print new skin cells to repair burned skin.”

Rapid Prototyping

The first stage of fabricating a tool is usually protracted and repetitive. Enter rapid prototyping: an ingenious method using three-dimensional CAD data to quickly fabricate a scale model of a part or assembly.

Besides being significantly faster, the advantage of 3-D printing prototypes is that it allows developers to immediately conduct design reviews, find flaws in parts, make revisions, and get a product to market much faster.

In December 2017, the US Navy partnered with E&G Associates to turn explosives into custom shapes using commercial 3-D printing techniques. The idea is to allow the Navy to figure out “how to turn plastic explosives into a nylon powder that can be fed into an off-the-shelf Hewlett Packard 3-D printer to make explosives charges of varying shapes,” according to a report in the Times Free Press.

In 2016, the US Navy announced that it had developed a next-generation, futuristic, 3-D-printed prototype called the Divers Augmented Visual Display (DAVD) to erase the problem of low visibility underwater. By adding smart glasses to the inside of the helmet, divers will be able to receive sonar images showing their location, as well as text messages and schematics of underwater objectives.

Weapons Development

In 2017, the US Army 3-D printed a grenade launcher, aptly named RAMBO. RAMBO (Rapid Additively Manufactured Ballistics Ordnance) is the culmination of six months of collaborative effort by the US Army Research, Development and Engineering Command (RDECOM), the US Army Manufacturing Technology (ManTech) Program and America Makes, the national accelerator for additive manufacturing and 3-D printing, the Army explained in a statement.

Scientists at the Wake Forest Institute for Regenerative Medicine print ear, finger bone and kidney structure scaffolds using a 3-D printer. (Photo: WFIRM)

Every component in the M203A1 grenade launcher, except springs and fasteners, was produced using AM techniques and processes. The barrel and receiver were fabricated in aluminium using a direct metal laser sintering (DMLS) process.

“The barrel and receiver took about 70 hours to print and required around five hours of post-process machining. The cost for powdered metals varies but is in the realm of US$100 a pound. This may sound like a lot of time and expensive material costs, but given that the machine prints unmanned and there is no scrap material, the time and cost savings that can be gained through AM are staggering,” the statement added.

Wearable Sensors and Clothing

Future combat uniforms will be designed for a network-centric battlefield. 3-D-printed uniforms will be better suited to the harsh combat environment, comfortable and lighter than current uniforms and will be able to incorporate ballistics materials and sensors into the wearer’s clothing. These wearable sensors and devices will be able to constantly monitor a soldier’s vitals and wirelessly transmit information back to the base.
Researchers from India’s National Institute for Interdisciplinary Science and Technology announced last year that they have developed “a lightweight, flexible and water-repellent wearable antenna which can be 3-D printed and embedded into textiles for applications in military uniforms.”

According to the study, the wearable antenna is 3-D printed from a conductive silver ink and it is flexible and lightweight, and, because it is silver and not copper, it will not oxidise. The bottom electrode on the polyester fabric the antenna was embedded into was 3-D printed, as was the E-shaped patch antenna itself.

“Our goal is to make a wearable antenna which can be embedded in the jacket worn by soldiers in remote locations,” said Dr. P. Mohanan of Cochin University of Science and Technology, who also worked on the study. “We can connect the antenna to different sensors such as temperature, pressure and ECG sensors, and the data can be transmitted to a remote server. The antenna can sense and communicate data in a non-intrusive manner. This way we can monitor the health of soldiers,” Dr. Mohanan added.

Customised Food

Fabricating foods such as chocolates, pizzas and pasta is another mind-boggling application of 3-D printing. In 2014, US Army researchers announced that they “are investigating ways to incorporate 3-D printing technology into producing food for soldiers.”
According to the US Army Natick Soldier Research, Development and Engineering Center’s, or NSRDEC’s, Lauren Oleksyk, a food technologist, the technology could be applied to the battlefield for meals on demand, or for food manufacturing, where food could be 3-D printed and perhaps processed further to become shelf stable. Then, these foods could be included in rations.

The advantage is that the nutrient requirement can be sent to a 3-D food printer so that meals can be printed with the right amount of vitamins and minerals to meet the individual nutritional needs of the fighter. “We have a three-year shelf-life requirement for the MRE [Meal Ready-to-Eat],” Oleksyk said. “We’re interested in maybe printing food that is tailored to a soldier’s nutritional needs and then applying another novel process to render it shelf stable, if needed.”

Natick food technologists are working to incorporate 3-D printing technology into foods for the warfighter. (Photo: David Kamm, NSRDEC)

The US Army is currently looking at ultrasonic agglomeration, which produces compact, small snack-type items. Combining 3-D printing with this process could yield a nutrient-dense, shelf-stable product. Army food technologists hope to further develop 3-D printing technologies to create nutrient-rich foods that can be consumed in a warfighter-specific environment, on or near the battlefield, according to an official statement.

In the Field of Medicine

Recent technological advances in 3D printing have had a profound impact on the healthcare sector. Militaries around the world are actively investing in regenerative medicine and 3-D bioprinting with the aim of helping injured servicemen and women. 3-D bioprinting is one tool that US Army scientists are developing in the field of regenerative medicine. It is an early discovery technology being used to address extremity injury and skin, genitourinary and facial repair by Armed Forces Institute of Regenerative Medicine, or AFIRM, investigators.

So how does it work? “In translating this technology to the clinic, scientists will take healthy cells and, using a device similar to an inkjet printer, load the cartridges with two types of skin cells – fibroblasts and keratinocytes – instead of ink. Fibroblasts make up the deep layer of skin, and keratinocytes compose the top layer,” according to a statement released by the US Army in 2014.

After the team completes a scan of the burn and constructs a 3-D map of the injury, the computer tells the printer where to start printing and what type of cells to use, depending on the depth of the injury and the layer being reconstructed. The bioprinter deposits each cell precisely where it needs to go, and the cells grow to become new skin.

Engines

The benefits of using additive manufacturing in building engine components vary from saving costs to reduced lead times. Several major players in the aerospace industry are already experimenting and testing 3-D printing to develop engine components.
In January this year, Finland’s first 3-D-printed aircraft engine part installed on the F/A-18 HORNET fighter had its successful maiden flight.

The additive-manufactured RAMBO system includes an NSRDEC-designed standalone kit with printed adjustable buttstock, mounts,
grips and other modifications. (Photo: US Army)

According to Patria, the part was designed in accordance with the Military Design Organization Approval (MDOA) and was manufactured using the Inconel 625 superalloy. “For this part, the development work has been done over the last two years, with the aim of exploring the manufacturing process for 3-D-printable parts, from drawing board to practical application. Using 3-D printing to make parts enables a faster process from customer need to finished product, as well as the creation of newer, better structures. We will continue research on additive manufacturing methods, with the aim of making the new technology more efficient,” says Ville Ahonen, vice president of Patria’s aviation business unit.

In 2017, GE announced that it is developing the world’s largest laser-powered 3-D printer that prints parts from metal powder under a new unit, GE Additive. The printer will be able to make parts that fit inside a cube with 1-metre sides. “The machine will 3-D print aviation parts suitable for making jet engine structural components and parts for single-aisle aircraft,” said Mohammad Ehteshami, vice president and general manager of GE Additive. “It will also be applicable for manufacturers in the automotive, power, and oil and gas industries.”

Additive machines fuse together fine layers of powdered metal with a laser beam and print three-dimensional objects directly from a computer file. With few limits on the final shape, the method gives engineers new freedoms and eliminates the need for factories filled with specialised machines or expensive tooling.

These parts were made using additive manufacturing, which creates plastic items and other durable components by adding material, layer by layer, using 3-D printers. (Photo: US Army)

And the year before, Orbital ATK announced it had successfully tested a 3-D-printed hypersonic engine combustor at the NASA Langley Research Center. The combustor, produced through an additive manufacturing process known as powder bed fusion (PBF), was subjected to a variety of high-temperature hypersonic flight conditions over the course of 20 days, including one of the longest-duration propulsion wind tunnel tests ever recorded for a unit of this kind.

“Analysis confirms the unit met or exceeded all of the test requirements. One of the most challenging parts of the propulsion system, a scramjet combustor houses and maintains stable combustion within an extremely volatile environment. The tests were, in part, to ensure that the PBF-produced part would be robust enough to meet mission objectives,” Orbital explains on its website.

Complex geometries and assemblies that once required multiple components can be simplified to a single, more cost-effective assembly. However, since the components are built one layer at a time, it is now possible to design features and integrated components that could not be easily cast or otherwise machined.

Drones

Additive manufacturing has had a significant effect on the development of unmanned systems. Among the benefits of 3-D printing drones is the freedom to create custom UAVs, upgrade and modify for specific missions, and perform better thanks to the use of new lightweight materials.

In December 2017, the US Army unveiled a 3-D-printed, on-demand aerial drone programme “that would allow for soldiers to enter mission parameters and then get a 3-D-printed aviation asset within 24 hours.”

Earlier in 2017, the US Army also flight-tested 3-D-printed unmanned aircraft created with a new on-demand system.
“We’ve created a process for converting soldier mission needs into a 3-D-printed on-demand small unmanned aircraft system, or ODSUAS, as we’ve been calling it,” explained Eric Spero, team leader and project manager.

The programme now plans to work on improving noise reduction, standoff distance, and agility, as well as increasing the 3-D-printed drone’s payload capacity.
Meanwhile, BAE Systems and the University of Glasgow envisage that small Unmanned Air Vehicles (UAVs) bespoke to specific military operations, could be ‘grown’ in large-scale labs through chemistry, speeding up evolutionary processes and creating bespoke aircraft in weeks, rather than years.

Introduced in 2016, a radical new machine called a CHEMPUTER could enable advanced chemical processes to grow aircraft and some of their complex electronic systems, conceivably from a molecular level upwards.

“This unique UK technology could use environmentally sustainable materials and support military operations where a multitude of small UAVs with a combination of technologies serving a specific purpose might be needed quickly. It could also be used to produce multifunctional parts for large manned aircraft,” according to a BAE Systems statement.

Limitations and Challenges

While there is no doubt of the advantages additive manufacturing offers the A&D industry, the technology still has its limitations. As it stands, 3-D printing technology cannot compete with traditional manufacturing processes. AM is predominantly dependent on a handful of polymers and metal powders to print parts, and it is limited to the size that can be manufactured. Conversely, traditionalmass production processes are significantly cheaper and faster, and they don’thave the same size restrictions.

“In 2013, AM thermoplastics cost about US$200 per kilogramme, while those used in injection molding cost only US$2. Similarly, the stainless steel used in AM costs about US$8 per square centimetre, which is more than 100 times the cost of commercial-grade stainless steel used in traditional manufacturing methods,” Deloitte explains in a study titled “3-D opportunity for aerospace and defence” published in 2014.

However, this may not always be the case. As research and development in the AM field continues to mature, the cost of 3-D printing will decline as materials selection improves in the coming years. Government agencies and educational institutions from around the world are already working to evolve 3-D printing from a prototype tool into a production one.
For instance, in February 2018, Boeing announced a five-year research agreement with Switzerland-based supplier Oerlikon to develop standard materials and processes for titanium powder bed additive manufacturing. Soon after that, Boeing announced its investment in Morf3D, a company specialising in lighter and stronger 3-D-printed parts for aerospace applications.

Despite its limitations, the inherent capability of 3-D printing to reduce weight, waste and quickly print stopgap solutions aligns perfectly with the needs of the aerospace and defence industry.
With 4-D printing already on the horizon, 3-D printing will undoubtedly make its mark in the A&D value chain.

Bindiya Carmeline Thomas is a specialist defence and aerospace journalist and a regular contributor to ESD.