Digital manufacturing is likely to be one of the key disruptive technologies of the 21st century. Described by The Economist as the foundation of a third industrial revolution,  digital manufacturing enables individuals and communities of designers to manufacture products themselves rather than relying on large factories with global supply chains.
While digital manufacturing holds significant potential as an engine of economic change, its potential effects on the proliferation of missiles and other weapons has not been adequately explored. The production and proliferation of missiles is foundationally an industrial process. Developing missile capability currently requires specialized industrial capabilities and expertise. Proliferation involves worldwide supply and transport chains similar to that of any modern globalized industry, albeit operating in secret. Just as digital manufacturing is likely to change the way household goods are produced, it will affect how missiles and other weapons are developed and proliferated.
What is Digital Manufacturing?
Digital manufacturing combines desktop design software – the sort that can be run from your home computer- and both traditional and new manufacturing equipment including 3D printers, Computer Numerical Control (CNC) machines that use digital instructions to operate a variety of cutting and millings tools, and laser cutters.
Digital manufacturing begins with software. Using software that has been used by industrial designers for decades, one can design and render a 3D model of the object for production. Designers need not start from scratch. The open source movement- a worldwide movement of inventors, programmers and designers who make their work available to others free of charge- provides a wide range of designs that can be directly manufactured or built on to create custom designs for particular needs. Designers can also take advantage of 3D scanners which can make a digital model of a physical object, saving the designer the trouble of redesigning the object from scratch and allowing the production of exceedingly exact copies.
The designer can then upload their work to digital manufacturing machines that can craft a range of products. 3D printers have received the lion’s share of attention in popular press due to the novel way they function. Rather than subtracting mass from a piece of raw material by cutting or molding, it adds material together to create a product. Printers equipped with print heads similar to the one of desktop inkjet printers spray layers of plastic to create products. More advanced machines use lasers to harden powder or liquid in layers to create objects, and can fashion products out of a wide range of metals including steel and titanium. CNC machines can be equipped with various tools that allow them to cut or mill a block of material into a desired shape or product. Laser cutters slice sheets of metal or wood into 2-dimensional objects and components. 
Digital manufacturing inverts traditional industrial mass production. Mass production creates very large numbers of identical objects. Digital manufacturing tools are more flexible- each machine can be used to produce a wide range of objects without requiring the often expensive and lengthy retooling traditional mass production would require. As digitally manufactured objects are produced individually there are no additional costs for additional complexity or customization in an object, allowing products to be designed to fit extremely specific requirements. This individualized production, however, means that digital manufacturing doesn’t capture the economies of scale seen in traditional mass production- the 100th or 1000th digitally manufactured object will cost as much as the first, whereas mass production requires a significant upfront investment that pays for itself over the manufacture of many hundreds or thousands of copies of a product.
Another advantage of digital manufacturing is that it enables local production. A file can be sent to a digital manufacturing machine anywhere in the world and produce an object on demand. Rather than outsourcing the manufacture of a product to a factory in China or elsewhere in the world (a process that can take weeks or months and introduces significant supply chain risks), a designer or customer can immediately make a product to meet a local need. The localization of manufacturing is potentially one of the most important effects of digital manufacturing as it could shift manufacturing (and manufacturing jobs) away from China and other low-cost global powerhouses back to the West and to local markets. The local advantage of digital manufacturing, beyond potentially changing the nature of the global economy, also encourages the spread of digital manufacturing capabilities. As 3D printers and other machines become available in local economies throughout the world, they will also become increasingly available to state and non-state actors who could harness them to produce missiles and other weapons.
The automotive and aerospace industries have been early adopters of digital manufacturing technologies. Ford uses 3D printers for rapid prototyping of automobile parts. In 2012, GE Aviation purchased Morris Technologies, a company heavily invested in 3D printing and other digital manufacturing technologies, which produces components for commercial jet engines. 3D printing reduces the amount and weight of the material in these engine parts, resulting in a more efficient jet engine. On a grander scale, Airbus is reported to be developing a 3D printer large enough to manufacture entire aircraft wings.
Digital manufacturing has also been embraced by the U.S military. The U.S. Army Research, Development and Engineering Command uses computer design software, 3D scanners, and 3D printers for the development and rapid prototyping of equipment before it is mass produced using conventional manufacturing techniques. Starting in 2012, mobile laboratories equipped with digital manufacturing capabilities have been forward deployed to support the logistics needs of troops in Afghanistan. The mobile labs allow the U.S. Army’s Rapid Equipping Force to manufacture spare parts and new components in Afghanistan based on collaborations from designers and engineers both in the United States and deployed in Afghanistan.
The proliferation of missiles and other complex systems is, at heart, an industrial process. Digital manufacturing will disrupt that process and allow for the production of more effective missile components, using a wider variety of facilities and equipment, by a larger number of actors. Digital manufacturing tools themselves would not be capable of producing a complete missile but they could be used to fabricate many key missile components, thereby reducing the challenge faced by a new weapons state from the manufacture of a weapon from scratch to the simpler assembly of a missile from its digitally produced parts.
Digital manufacturing can be used to produce components for missiles that are more effective than those produced by traditional industrial processes. NASA is currently using selective laser melting, a process similar to 3D printing which uses a laser to harden layers of metallic powder into an object, to produce components for the Space Launch System(SLS). The SLS is a heavy lift rocket intended to carry robotic and manned missions to “nearby asteroids and eventually to Mars.” As digital manufacturing allows rocket components to be produced in a single piece, rather than welding together smaller parts produced using traditional processes, the components are stronger and more resilient increasing the reliability of the launch vehicle. Digital manufacturing would likely produce similar benefits for the production of components for ballistic missiles, which share many common features with space launch vehicles.
Missile warheads and fuel may also be made more effective by digital manufacturing. 3D printing could be used to produce warheads with specific geometries that would produce enhanced effects when detonated. Similar methods could also be used to produce propellants shaped to provide better and more efficient burn rates for rockets and ammunition. 
A greater proportion of digital manufacturing equipment than its traditional industrial counterparts will be dual-use technology. Digital manufacturing tools are inherently flexible and can produce a wide range of products without requiring retooling or other substantial modification. Governments and non-state actors could take advantage of civilian digital manufacturing capabilities to produce components for missiles and other weapons systems without needing to modify the equipment or the facilities that house it. The number of facilities that could be used for proliferation activities would be significantly greater making detecting and tracking a missile program more difficult. This would also complicate efforts to disable or delay a missile program through sabotage or an overt military attack. Lastly, the greater number of proliferation-sensitive facilities would make transparency and confidence building more difficult even in the absence of intent to acquire missiles or other weapons.
Digital manufacturing would also allow proliferators to better leverage limited human capital. Design software requires less expertise to use than traditional design methods. Digital manufacturing systems themselves are automated, reducing the number of skilled machinists and technicians needed to produce missile components.  While the assembly and integration of components into a functioning missile system would still require a pool of experienced engineers and technicians, proliferators would still require less design and production expertise than traditional industrial production processes would demand.
Digital manufacturing would also benefit non-state proliferators. Non-state actors generally lack access to facilities to produce anything beyond crude artillery rockets and depend on support from state sponsors. As digital manufacturing capabilities become increasingly available throughout the world, non-state actors will be able to access local manufacturing capabilities to produce weapons based on designs provided by their state benefactors or to improve home built capabilities. Hamas, for instance, has made extensive use of crude artillery rockets, the accuracy and effectiveness of which would be significantly improved if engine parts and other components currently made with drills and lathes were produced with greater precision by digital manufacturing machines.
A key advantage of digital manufacturing is the ability to easily convert a design from a file directly into a physical object. As cyber-crime, efforts to crack down on software and music piracy and Wikileaks have demonstrated, information is very difficult to protect, contain, and control. Rather than attempting to prevent the shipment of missiles or components from states like North Korea or Iran to new weapons states or non-state actors, the non-proliferation regime will be faced with the problem of controlling the movement of information. It would most likely be easier for North Korea, for instance, to transfer data to allow a customer to manufacture missile components using local digital manufacturing facilities than to ship missiles or components that could be tracked and intercepted as they traveled from Northeast Asia to the Middle East or other hotspots. A proliferating state could leverage digital manufacturing to shift its business model to the sale of weapon design information rather than complete weapons or to reduce the scale of shipments to make them more difficult to track.
Digital manufacturing is also deeply linked with the open source hardware movement which has developed tools to allow for the easy sharing of hardware designs as well as collaboration on new projects. This approach has been adopted for military projects in the United States; the Defense Advanced Research Projects Agency (DARPA) currently sponsors a project to design a new amphibious tank for the U.S. Marine Corp that uses online collaboration tools to allow far flung networks of researchers to collaborate on designs.  Similar tools would facilitate collaboration among global proliferation networks such as the Iranian-North Korean partnership for the development of ballistic missiles. Non-state actors could also use such tools to leverage the efforts of sympathetic engineers and designers throughout the world. Proliferators could also take advantage of the blueprints made available by members of the open-source movement elsewhere in the world. Designers with an interest in space systems or aerodynamics could unwittingly provide assistance to a foreign missile design program.
Proliferators could also benefit from design information from Western governments and industry. The computer networks of the U.S. government and defense contractors are frequent targets of cyber-attacks from a variety of sources. While technical specifications and other design information obtained via cyber-espionage would already be useful to proliferators, digital manufacturing would exacerbate this vulnerability. Designs intended for digital manufacture – either for rapid prototyping or for the production of final components – would be easier for proliferators to use. Rather than needing to interpret and replicate the production of a component or system from stolen design files, proliferators could simply enter the data into compatible digital manufacturing machines to produce an exact physical copy of the stolen design.
Digital manufacturing has security implications beyond missile proliferation. The information sharing and streamlined production processes that make the proliferation of missiles easier could also enable nuclear proliferation. Digital manufacturing would have little effect on the production of nuclear weapons themselves or their requirement for significant quantities of highly enriched uranium or weapons grade plutonium. The design and production of uranium enrichment centrifuges and other equipment necessary for a nuclear program, however, would be simplified by digital manufacturing much as missile production would be.
Digital manufacturing could also be used to produce small arms. Open source networks are collaborating on the design of small arms including Defense Distributed, a U.S. based group that is working to design and produce 3D printable firearms including the controversial AR-15 rifle. As digital manufacturing becomes more widespread such projects will serve to significantly undermine domestic gun control laws as well as undercut international efforts to control the trade in small arms.
The manufacture of spare parts, as currently undertaken by the U.S. military, could also serve to undermine sanctions regimes intended to curtail proliferation. Iran, for instance, has a significant number of aircraft and weapons systems obtained from the West before the Islamic Revolution. While Iran’s F-14 fighter aircraft are less capable than the most advanced aircraft flown by the United States and its regional allies, they could still pose a potent threat. The difficulty in obtaining spare parts and other maintenance supplies from the U.S. has grounded most of the Iranian Air Force’s F-14s and forced Iran to develop clandestine networks to secretly obtain spare parts under the cover of legitimate business deals. In the future, a state placed under an arms embargo could use digital files- obtained legally before the sanctions or clandestinely afterwards- or 3D scans of existing components to produce new parts and maintain their military capabilities despite sanctions.
Proliferation in the Digital Future
Digital manufacturing will change the production and proliferation of missiles and other weapons in much the same way it will transform civilian industries. Rather than depending on a small number of states with the capability and will to proliferate missile systems or technologies, state and non-state actors will be able to leverage the civilian manufacturing sector and global networks of missile expertise to obtain weapons.
This new industrial model for proliferation will require new concepts for counter-proliferation. Missile and other weapons technologies will be available to a wider number of actors. Future counter-proliferation efforts will be faced with less visible footprints for missile production and ethereal web-based networks of missile expertise and data proliferation. Non-proliferation and cyber security experts will need to collaborate to understand how to track and defeat the information sharing capabilities that digital manufacturing enables. Stopping the flow of missile technology around the world has been a difficult task faced with many setbacks. As digital manufacturing comes of age, preventing further missile proliferation will only become more difficult.
Matthew Hallex is a defense analyst who lives and works in northern Virginia. He holds a Masters in Security Policy Studies from George Washington University.
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