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Introduction:
In the realm of defense, warfare, and explosive applications, the field of energetic materials and munitions technologies continues to push the boundaries of innovation. These technologies, ranging from explosives to propellants and pyrotechnics, play a crucial role in various industries, including defense, aerospace, mining, and entertainment. In this blog article, we will delve into the fascinating world of energetic materials and munitions technologies, exploring the latest advancements, their applications, and the impact they have on our modern world.
Applications in Defense and Beyond:
Energetic materials and munitions technologies find extensive applications in defense and security. They are the driving force behind ammunition, grenades, missiles, and various explosive devices used in warfare. Advancements in insensitive munitions, smart explosives, and energetic propellants contribute to enhanced performance, safety, and efficiency in military operations. However, the applications of energetic materials are not limited to defense alone. They also play a vital role in aerospace, mining, construction, entertainment, and even biomedical fields.
Impact on Defense
The recent Russia Ukraine war has proved once again that explosive power behind munitions like missiles, rockets, and artillery is key to asserting control of the battlefield. What these munitions have in common is that they rely on energetic materials — critical chemicals that help determine the range, size, and explosive power of missiles and rockets.
Energetic materials and munitions are used across DoD in mission critical applications such as rockets, missiles, ammunition, and pyrotechnic devices. In these applications, energetic materials and munitions must perform as designed to ensure success in both training and combat operations.
Despite their importance to much of what the military does, there has been little in the way of practical advancement since the end of World War II. For example, RDX, one of the mainstays of our explosive inventory, was patented in 1898, and entered manufacturing in 1940; another common explosive, HMX, is only slightly more recent, having entered service only a few years later.
Indeed, several recent studies sponsored by both the Defense Department and industry have highlighted the need for urgent action to address performance, production and supply chain shortfalls in the U.S. energetic materials enterprise.
According to a 2018 DoD study, China is “the sole source or a primary supplier for a number of critical energetic materials used in munitions and missiles.” The munitions supply chain also features an alarmingly high number of single points of failure: of 198 second- and third-tier suppliers in the industrial base, 98 percent rely on a single or sole source. And the materials that are produced in the United States tend to be made in in a handful of outdated, government-owned facilities using 20th century equipment.
Data from Georgetown’s Center for Strategic and Emerging Technologies suggests that over the past five years Chinese scientists have published nearly seven times as many papers relating to energetics materials than have their American counterparts. And the Energetics Technology Center has pointed out that China “heavily supports four top academic institutions to perform energetics research and develop their workforce.”
Energetics
Energetics come in three main forms: explosives; propellants, which produce thrust; and pyrotechnics (think flares or fireworks). This means that better energetics offer major advantages in combat. In some cases, depending on the system, they can boost the range of missiles by 40 percent or more — allowing the targeting of an adversary from a safer distance — while also improving lethality, upping the likelihood a target is destroyed on the first try. Improved energetics can help the Department of Defense build smaller munitions that still pack a punch. At the operational level, defending allies and partners such as Japan, South Korea, the Philippines, and Taiwan from Chinese aggression will require an ample supply of munitions powered by energetic materials.
Understanding Energetic Materials:
Energetic materials are substances that possess high energy content and have the ability to undergo rapid exothermic reactions. They are the powerhouse behind explosions, propulsions, and dazzling pyrotechnic displays. Explosives, propellants, and pyrotechnics are some of the key types of energetic materials. These materials consist of carefully formulated compositions, blending fuel and oxidizer components, with each component playing a vital role in energy release, stability, and performance.
Energetic materials, also known as explosives or propellants, are substances that release a large amount of energy when they are ignited or otherwise activated. These materials are used in a wide range of applications, including military, industrial, and civilian uses.
Some examples of energetic materials include:
- TNT (Trinitrotoluene): A common explosive that is widely used in military and industrial applications.
- C-4: A plastic explosive that is stable and easy to shape, often used in military operations.
- RDX (cyclonite): A high explosive that is often used in military applications, as well as in industrial blasting operations.
- HMX (octogen): A powerful explosive that is used in military and industrial applications, including rocket propellants.
- Ammonium nitrate: A common ingredient in fertilizers, but also can be used as a powerful explosive when combined with fuel oil.
- Nitroglycerin: A highly sensitive and powerful liquid explosive, used in industrial blasting operations and in making dynamite.
- Black powder: One of the oldest known explosive, made of a mixture of saltpeter, charcoal, and sulfur, used in fireworks and some firearms.
Energetic materials are highly regulated due to their potential to cause damage and injury if they are mishandled or used improperly. The storage, transportation, and use of these materials are strictly controlled by government agencies to ensure public safety.
For in-depth understanding on Energetic Materials technology and applications please visit: Energetic Materials: From Science to Applications and Safety
New Energetic Material technologies
There are several new technologies that are being developed in the field of energetic materials, also known as explosives or propellants. These technologies are focused on improving the performance, safety, and environmental impact of these materials.
Some examples of new energetic material technologies include:
- Green Propellants: Researchers are working on developing new propellants that are safer and more environmentally friendly than traditional propellants. These “green” propellants typically use hydrogen peroxide or hydroxyl ammonium nitrate as the oxidizer, which are less toxic and less flammable than traditional oxidizers.
- Nanoenergetics: Researchers are working on developing new energetic materials at the nanoscale, which can have unique properties and performance characteristics. For example, nanoscale aluminum particles can be used to create more powerful and efficient propellants.
- Insensitive Munitions: The development of new energetic materials that are less sensitive to shock, friction, and heat, making them safer to handle and transport. This can reduce the risk of accidental detonation and improve the safety of military and industrial operations.
- Biobased Propellants: Researchers are working on developing new propellants that are made from renewable, biobased materials such as plant sugars, starches, and cellulose. These biobased propellants are expected to be more sustainable and less toxic than traditional propellants.
- Self-healing Energetic Materials: Researchers are working on developing new energetic materials that can repair themselves after being damaged. This can improve the safety and performance of the materials and reduce the need for maintenance and repair.
- Smart Energetic Materials: Researchers are working on developing new energetic materials that can be programmed to respond to specific triggers, such as temperature or pressure. This can improve the performance of the materials and allow for more precise control over the timing and intensity of the explosive reactions.
These are just a few examples of the new technologies being developed in the field of energetic materials. The energetic materials market is constantly evolving, and companies are investing in R&D to develop more advanced technologies to meet the evolving needs of customers.
Novel Energetic Materials consists of fundamental research programs to expand and validate physics-based models and experimental techniques to devise chemical formulations that will enable the design of novel insensitive high-energy propellants and explosives with tailored energy release for revolutionary Future Force lethality and survivability. This program supports demonstration of advanced energetic materials with ability to tune energy release for precision munition & counter-munition applications (e.g., propellants, explosives, thermobarics, multi-purpose warhead, APS).
These energetic materials may have the potential of providing factors of 3 to 4 in increased energy release rate compared with conventional formulations. The Army’s Novel Energetic Materials for the Objective Force effort seeks to mature advanced energetic materials to provide a 40% increase in deliverable energy from advanced gun propellant systems and a 20-50% increase in warhead effectiveness (munitions, active protection).
Like advanced initiation, improved energetic materials are enabling technology for the next generation of weapon systems that will be safer, smaller and more lethal. Under this program a combination of evolutionary and novel technologies are under development. Conventional chemistry has been used to develop more powerful, less sensitive explosives.
Nano-structured and engineered materials are being explored to increase energy density and energy on target by factors of three or more. In general, initiation and detonation properties of energetic materials are dramatically affected by their microstructural properties. It is generally known in material science that the mechanical, acoustic, electronic, and optical properties are significantly and favorably altered in materials called “nanostructures,” which are made from nanometer-scale building blocks. Modern technology, through sol-gel chemistry, provides an approach to control structures at the nanometer scale, thus enabling the formation of new energetic materials, generally having improved, exceptional, or entirely new properties.
Higher risk efforts are also underway to explore the possibility of metastable High Energy Density Materials (HEDM). Using conventional chemistry, a number of new candidate molecules have been synthesized, characterized and formulated. The development of new materials is based on theoretical molecular design. The structure, performance and sensitivity of new molecules are predicted computationally, then synthesis is attempted. The focus is in two areas: molecules with significantly increased energy over current materials and very insensitive materials with reasonable energies.
Another emerging technology that holds promise in the energetic materials field is the use of biological processes for advanced manufacturing. In effect, Synthetic biology has turned the bioscience into the future manufacturing paradigm where Companies can engineer and manufacture an infinite quantity of things, cell by cell, from scratch. These bioengineered microorganisms, plants, and animals can produce pharmaceuticals, repair defective genes, develop new generations of vaccines, destroy cancer cells, detect toxic chemicals, break down pollutants, and generate hydrogen for the post-petroleum economy. Synthetic biology will also enable the production of complex molecules for use in next-generation energetic systems. It also offers the potential of environmentally benign manufacturing solutions.
Explosives
Explosive substances are solid or liquid substances or mixtures, which can, by chemical reaction, generate gases of such a high temperature, pressure and speed that they can cause destruction in their vicinity. Explosives means blasting agents, propellants, initiating agents, igniting agents, pyrotechnic mixtures. High explosives means detonating agents or compositions.
Explosives are used in munitions as the main charge in warheads and in the fuses, primers, and detonators used to initiate the main charge. The performance of explosive materials is often tied to environmentally objectionable materials such as lead and RDX. In addition, the synthesis processes for explosive compounds such as trinitrotoluene (TNT) and triaminotrinitrobenzene (TATB) generate significant amounts of hazardous waste or require environmentally harmful precursor materials. Projects are focused on developing explosives made with environmentally friendly synthesis processes and materials while not sacrificing performance.
Ammunition and Projectiles
Potential environmental hazards are associated with nearly all the components of a round of ammunition typically used by the military. Primer formulations use harmful lead compounds. Propellants contain nitrocellulose and significant amounts of hazardous waste are generated during their production. Projectiles are made of harmful materials such as lead and depleted uranium. Projects focus on the development and demonstration of alternatives that do not contain harmful materials or generate hazardous waste in production.
Rocket and Missile Propellants
Propellants mean agents made of solid or liquid deflagrating explosives that are used for propulsion.
To maintain the required performance of weapon systems, the propellants currently used in military rockets and missiles require environmentally harmful substances, such as ammonium perchlorate and lead compounds. Projects aim to develop and demonstrate new propellant formulations that do not contain perchlorates, lead compounds, RDX, or other environmentally objectionable materials.
Pyrotechnics
Pyrotechnic mixtures are substances or mixtures designed to generate an effect in the form of heat, light, sound, gas or smoke or a combination of these effects
as a result of nondetonative, self-sustaining, exothermic chemical reactions.
Pyrotechnics are critical components of devices used as decoys, obscurants, combat simulators, and signals. They are required to ignite and burn in a specific manner and produce specific colors and intensities of light or smoke. To fulfill these requirements, pyrotechnic formulations often contain harmful materials such as perchlorate, naphthalene, and hexachloroethane, as well as toxic metals. Projects in this area focus on developing new pyrotechnic formulations that do not contain these and other environmentally harmful materials.
Innovations in Energetic Materials:
The field of energetic materials is witnessing remarkable advancements aimed at enhancing their performance, safety, and sustainability. Researchers are constantly exploring new formulations, synthesis methods, and additives to optimize energy density, improve stability, and reduce environmental impact. The integration of nanotechnology, additive manufacturing, and computational modeling has revolutionized the design and development of energetic materials, allowing for precise control, customization, and multifunctionality.
Nanoscale energetic material systems
The overall goal is to engineer multi-dimensional nanoscale energetic materials systems whose energy release can be controlled in terms of its type, rate, spatial distribution, and temporal history. The goal is to manipulate individual atoms and molecules and control their assembly into a large-scale bulk energetic material. The possibility exists to build large-scale energetic materials with a very high degree of uniformity (few/no defects, perfect crystalline structure, composites with molecularly engineered uniformity, laminated composites with structures built molecularly controlled and selectable layers – – no stirring, mixing – – all done through self-assembly). It is also possible to embed molecular scale devices within the energetic matrix (embedded smart devices and sensors).
The current emphasis in the nanoscale energetic materials area is on the preparation and characterization of single nanoscale energetic particles. These particles are then utilized in an otherwise conventional composite formulation, incorporating the nanoparticles (typically aluminum, the fuel) in a matrix with micron-sized oxidizer particles. While there is some performance improvement, the full extent of the anticipated performance gains of the nanoscale materials have not been realized. In large measure this is due the incompatibility of the length scales. What is needed is a formulation with all constituents at the nanoscale. If this were accomplished, the reactivity of the material would be characterized by the almost premixed gas-phase reaction rates of the nanomaterials; not limited by the slower, diffusion dominated reactions of micron-sized constituents. It may also be expected that the much smaller crystalline sizes of nanomaterials would be much less susceptible to shear-induced initiation and may be less responsive to some hazards.
Macroscale formulations of energetic materials that preserve the intrinsic nanoscale structure of the individual components are needed to realize the true potential of nanoscale energetic materials. An optimal material may be a macroscale three-dimensional, ordered array of nanoscale constituents, with spacing and interstitial/bonding materials chosen to optimize both stability and reactivity. At a minimum, these macroscale units would be on the order of millimeter size, which could then be processed into the centimeter to meter sizes needed for practical propellants and explosives. The advantages of this “bottom-up” approach to energetic materials are: a) developing a fundamental understanding of the evolution of properties with the size of the system, b) understanding the effects of the interaction of matter at different molecular-length scale with external stimuli, and c) developing a detailed understanding of the functionalities of matter at molecular-length scale.
The chemistry, physics and materials science of nanoscale energetic material preparation need to be developed, focusing on those processes that lead to well ordered structures, e.g. self-assembly, vapor deposition, etc. Computational methods are needed to assess the reactivity of candidate structures and to predict the stability of the energetic material structure, to both hazards (shock, spark, etc.) and to long-term degradation. These computations should also provide guidance to and receive validation from the experimental aspects of the program, specifically the formulation and characterization activities. Experimental methods of characterizing nanoenergetic structures are needed to verify structure and performance. This includes developments of techniques capable of the determination of the threedimensional structure of the nanoscale assembly and the orientation and bonding of the constituents. Characterization of reaction front progress through the nanostucture is also desirable.
One new explosive under development is LLM-105. It is dense, thermally stable and very insensitive. With 30% more energy than TNT it has possible detonator and booster applications and is an alternative to TATB in special purpose weapons such as hard target penetrators that have to survive high shock loading. The synthesis, scale-up, and characterization of this material have been completed and its use as insensitive booster material for Navy weapons applications is now being evaluated. Efforts to crystallize the pure form of a newly synthesized energetic material with predicted energy greater than CL-20, LLM-121 continued in FY 2001.
Two other very fast burning materials, BTATz and DHT, have been successfully synthesized and are under evaluation as enhanced performance gun and rocket propellant ingredients. Metastable Intermolecular Composites (MIC) developed under this program were the first successful examples of nano-structured energetic materials with significantly enhanced performance. They demonstrated that tailored, ultra-fine reactant particles could dramatically increase the energy release rate of thermite-like materials and provide twice the total energy of high explosives. The first application of this technology is for lead-free percussion primers for small arms ammunition, and this program is now in engineering development under SERDP funding. The current focus is on the optimization of this material for other weapons applications via better diagnostic and measurement methods.
A new bulk process for manufacturing nano-structured energetic materials using sol-gel chemistry has been developed with the promise of precise control of material homogeneity, properties, and geometry. Samples of this material were manufactured this year for testing and evaluation in support of reactive warheads that better couple energy to the target and applications that require very high thermal loading. Extended solid HEDMs are also under development. This work uses intense pressure and temperature to force elements into highly energetic bonding states that can be recovered to ambient conditions. Current synthesis techniques have produced CO-derived solids and a family of novel nitrogen materials, but in very small quantities. These materials are expected to be highly energetic, but characterizing them, and particularly verifying the energy content, has been difficult due to the microscopic quantities of material available.
Boron-powered missiles
In Sep 2022 it was reported that China is developing a supersonic anti-ship missile that will be able to travel further and faster than any traditional torpedo. The 5 metre (16.4 feet) missile will be able to cruise at 2.5 times the speed of sound at about 10,000 metres (32,800 feet) – the same altitude as a commercial airliner – for 200km (124 miles) before diving and skimming across the waves for up to 20km.
One of the biggest challenges for the developers is the power system, because of the need to produce considerable thrust while breathing in either air or water. But Li’s team said the problem could be solved by using boron – a light element that reacts violently when exposed to both, releasing a huge amount of heat. The team, from the college of aerospace science and engineering in the National University of Defence Technology in Changsha, Hunan province, unveiled a blueprint for the missile’s power system in the September 8 issue of the peer-reviewed Journal of Solid Rocket Technology, published by the Chinese Society of Astronautics.
Boron was briefly added to jet fuel by the US Air Force in the 1950s to increase the power of supersonic bombers. But the project was abandoned because the ignited boron particles were hard to control and formed a layer of debris that gradually reduced engine performance.
A Nasa study funded by the US Navy last year found that nanotubes made using boron nitride, a combination of boron and nitrogen, could potentially be used to power hypersonic weapons travelling at speeds above 6,400km/h (4,000 miles per hour).
But most boron-powered engines are designed to work only in the air. Researchers usually choose aluminium or magnesium as fuel to drive supercavitating torpedoes as they react more easily with water. Li’s team said they had designed a boron-powered ramjet engine that could work both in the air and underwater.
There are some unique components, such as adjustable inlets and exhaust nozzles to maintain the boron’s burn efficiency in different environments, but the biggest change is in the fuel rods, according to their paper.
Boron usually accounts for about 30 per cent of the total fuel weight in an air-breathing missile because of the many other chemicals required to control and prolong the strong combustion.
Li’s team has doubled the share of boron in the fuel and estimates the result could produce a thrust greater than that of aluminium in water.
“The cross-media ramjet uses a fuel-rich solid propellant, which burns with the external air or seawater entering into the ram to generate high-temperature gas and generates thrust through the nozzle,” the paper said.“It has the high specific impulse and simple structure as an ideal power source for a cross-media anti-ship missile.”
5E Advanced Materials, Estes Energetics, announced in Dec 2022 to produce boron-based materials for rockets. In a press release, the companies said that the ultimate goal of their collaboration is supporting the US space and military industries and the specific focus will be on solid rocket motor ignitors.
Machine learning
Researchers have developed a machine-learning-assisted method for accelerating the discovery of new energetic materials via efficient prediction and quick screening. Suitable neural networks are established for accurately predicting the detonation properties of various N-containing molecules based on their structures, including density (ρ), detonation velocity (D), and detonation pressure (P).
Purdue, AAE play key research role in MURI grant focused on energetic materials and machine learning
In collaboration with six universities, Purdue was awarded a Multidisciplinary University Research Initiative (MURI) award from the Department of Defense (DoD) to build a capability to allow scientists to predict the behavior of energetic materials using advanced machine learning tools, which cover a wide range of applications including military munitions, propellants, pyrotechnics, and industrial explosives. The University of Missouri is the principal investigator on the project that includes researchers from Purdue, the University of Illinois, the University of Iowa, the University of Illinois-Chicago, Columbia University, and the Rensselaer Polytechnic Institute in New York.
AAE Professor Vikas Tomar says the project, “Integrating Multiscale Modeling and Experiments to Develop a Meso-Informed Predictive Capability for Explosives Safety and Performance,” will address a long-standing problem that never has been addressed before. “So far, a significant focus of energetic materials research has been on material processing. However, microstructures for such materials have random character making them unsuitable for systematic microstructural characterization tools available for other materials such as metals or ceramics,” Tomar says. “This characteristic makes these materials also suitable for data science tools incorporating machine learning, a focus of the proposed work. Purdue’s Interfacial Multiphysics Lab has unique capabilities to perform high throughput experimental measurements of thermal and mechanical properties in energetic materials at nanometers to micrometers length scales with picosecond time resolution, a key requirement for models needed for the proposed work.”
Tommy Sewell, a professor at Missouri who is the PI on the project, says the team will use artificial intelligence or machine learning to sift through mountains of experimental and simulated data and to identify correlations in the data that scientists might miss. But he also says machine learning will only take his team so far. “If all that you seek is knowledge, maybe that is good enough for some purposes, but it’s not good enough for us,” Sewell says. “What we seek is understanding, and that comes from ‘carbon-based’ computing (human thought and physical models), not silicon-based. A long-term goal is to minimize the amount of experimentation and the assorted costs and do most of the work in computer simulations, and then use experimentation to validate the results. If we’re successful, we will end up with a framework that can be adapted to treating the initiation phenomenon for a wide variety of explosives.”
Another goal is to reduce accidents involving energetic materials, Sewell says. If rocket propellant transitions from a stable burn over to a detonation, it can result in catastrophic consequences. “What we are trying to do … is to develop a theoretical framework that will allow us to derive the next generation of reactive burn models that are far more predictive than models currently in use,” Sewell says. “The goal is to reduce accidents, to improve safety, and to be able to design energetic formulations that would have much more tightly tailored performance.”
3D Printing of Energetic Materials and Components
Additive manufacturing of energetic materials is an enabling technology in that it affords unique geometries and unprecedented control over dynamic behavior. This for example could be a complex energetic materials structure, or a component of an energetic system.
3D printing involves the layer-by-layer deposition of one, or more, materials. The spatial placement of the material, if carefully controlled, can influence a desired static or dynamic property. The use of 3D printing to build complex and unique energetic components is at the center of LLNL’s architected energetic materials and structures effort. LLNL has developed several different methods for using 3D printing to create articles of energetic materials applicable to high explosives, propellants, and pyrotechnics. Methods being explored include direct printing of energetic materials as well as creating unique scaffold structures for integration with energetics. Scaffolds can be fabricated with metal, polymer, plastic, ceramic, and reactive composites, and some applications are charge liners, fragmentation packs, plane-wave generators, and reactive casings.
Major benefits of 3D printing of energetics range from reducing the cost and footprint of manufacturing, to rapid prototyping of energetic components. Additionally, performance and safety properties can be controlled in new ways through the spatial control offered by additive manufacturing. This, for example, could include an assembly of two or more energetic materials spatially arranged in such a way that the collective effect yields a new or optimized behavior. Another benefit of 3D printing is that, if the performance can be optimized, it allows for the use of less mass of material. This attribute is beneficial from both a cost and safety standpoint. The versatility of 3D printing of energetic components allows much more flexibility in the design of explosive, propellant, and pyrotechnic systems.
The Role of Safety and Regulations:
While the potential of energetic materials is immense, their use must be approached with the utmost caution and responsibility. Safety protocols, regulatory compliance, and risk assessment play a critical role in ensuring the safe handling, storage, and transportation of these materials. Adherence to stringent regulations ensures public safety, protects the environment, and minimizes the risks associated with their use.
Trends and Future Prospects:
The evolving landscape of energetic materials and munitions technologies holds exciting prospects for the future. Innovations focus on enhancing performance, sustainability, and safety. Advancements in energy storage, green formulations, micro- and nano-energetic systems, and computational modeling are expected to revolutionize the field further. The integration of emerging technologies and the collaborative efforts of multidisciplinary teams will drive breakthroughs and shape the future of energetic materials and munitions technologies.
Conclusion:
The world of energetic materials and munitions technologies continues to evolve, paving the way for groundbreaking advancements in defense, aerospace, and various industries. These technologies have transformed warfare, propulsion systems, and entertainment displays, providing the power, safety, and precision required for diverse applications. As research and innovation progress, the responsible use, safety, and sustainability of energetic materials remain of utmost importance to ensure their benefits are harnessed while mitigating risks. With the right balance of innovation and responsibility, the field of energetic materials will continue to propel us towards a safer, more efficient, and technologically advanced future.
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