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Rethinking Military Logistics in Contested Environments
In today’s era of multi-domain warfare, logistics has become as strategic as firepower. Modern battlefields, particularly in contested or resource-depleted environments, challenge the assumption of uninterrupted access to high-quality materials and long supply chains. The Defense Advanced Research Projects Agency (DARPA) recognizes this evolving reality and has launched the “Rubble to Rockets” (R2) initiative—a bold attempt to flip the script on how military assets are manufactured in theater.
Instead of depending on centralized, pristine supply lines, R2 envisions soldiers transforming discarded military scrap into critical aerospace components directly at the point of need. This pioneering initiative is transforming obsolete military hardware into aerospace-grade components, marking a radical shift in how we view waste, supply chains, and innovation in defense.
The Challenge: Mountains of Military-Grade Waste and Vulnerable Supply Chains
Every year, the U.S. military decommissions thousands of tons of high-performance materials—from the titanium in retired aircraft frames to armor-grade steel in tanks and missiles. While these materials still meet stringent mil-spec standards, they often end up stockpiled or scrapped due to obsolescence. This represents not only an environmental liability but also a lost opportunity for high-value reuse. In a world where raw material sourcing is under geopolitical pressure and supply chains are increasingly vulnerable, this stockpile could be a strategic goldmine.
Conventional defense manufacturing presumes access to purpose-engineered materials and precision processing environments. Current production systems are optimized for specific materials and conditions, making them inflexible. If the material input changes, it often necessitates a costly and time-consuming redesign. This rigidity is particularly problematic in a military context, where adaptability and speed are crucial.
Material conversion—such as atomization, wire extrusion, and sheet production—typically occurs in large foundries under tightly controlled conditions using pristine materials. This process is not feasible at the point of need, where materials may be scavenged and of varying quality. Structural applications of such materials are limited due to the extensive qualification and analysis required, and the presence of unknowns, such as alloy composition or surface conditions, further restricts their use.
These systems are inflexible; any deviation in material input or operations outside of a controlled factory setting necessitates costly redesigns due to the rigid production and design frameworks. Even minor material changes or alterations to single components require extensive analysis and testing, making the system inflexible and dependent on fixed inputs for fixed outputs.
These assumptions crumble in scenarios where logistics are constrained—whether due to active conflict, natural disaster, or remote deployment. Structural metals, ceramics, polymers, and composites that meet military specifications often end up as scrap when the original equipment is decommissioned. Ironically, this scrap, still rich in value and potential, is either discarded or warehoused indefinitely. DARPA’s R2 program addresses this paradox, aiming to repurpose obsolete and scavenged materials into vital aerospace structures such as rocket pressure vessels.
R2’s Vision: Decentralized, Agile Manufacturing
The R2 program is working toward a system where warfighters can gather discarded or scavenged materials—steel from wrecked vehicles, aluminum from dismantled infrastructure, or composites from defunct drones—and convert them into flight-ready components. The initiative hinges on three interdependent capabilities: material conversion, material characterization, and adaptive design.
For example, teams at the University of Miami, in collaboration with Teledyne Scientific and the University of Wisconsin-Madison, are using scrap alloys to create fine powders that can be 3D-printed into high-pressure aerospace-grade vessels. These parts will eventually be used in sounding rockets, a proof-of-concept platform selected for its complexity and high-performance demands.
Under the leadership of Professor Charles “Chip” Tomonto at the University of Miami College of Engineering, researchers are developing a system to convert military scrap into essential spaceflight hardware. The first targets? Sounding rockets—single-use vehicles that launch scientific experiments to altitudes between 80 and 150 kilometers. These rockets serve as ideal testbeds for validating lightweight structural components under extreme mechanical and thermal stress.
Flexible Frameworks for Unpredictable Inputs
One of the core innovations of the R2 initiative is its departure from rigid, factory-centric manufacturing. The key innovation lies in developing a design framework that can account for the system-level effects of materials and components. This would allow both existing and future systems to quickly adapt to new materials and fabrication methods, such as additive manufacturing, thereby significantly reducing the risks associated with adopting new technologies.
DARPA is specifically seeking a framework capable of producing versatile, adaptive designs rather than singular point solutions for given materials. Proposers must demonstrate the ability to rapidly update a government-provided sounding rocket design with new materials. They will be periodically challenged with government-provided material streams within their defined domains of applicability, for which they must predict material properties and update the design within the timeframes specified in the metrics table. Performers should also demonstrate the capability to vary payload size to achieve selected ranges while ensuring the overall design meets the minimum range of 35 km.
The approach to material property prediction in the R2 program emphasizes working “in reverse”—using new materials to predict property data, rather than starting with material data to predict new materials. This involves predicting the properties of the feedstock and final manufactured product, including any necessary heat treatment or post-processing to enhance material performance. The primary goal is not to fully characterize the material but to efficiently establish a lower bound design value that captures system-level effects. To achieve this, multiple standard mechanical testing and statistical methods can be employed to build and validate predictive models, balancing the improvement of material properties with minimizing errors across a broad solution space.
The program is developing frameworks that can accept mixed and contaminated materials in various forms—wires, powders, chunks, or particulates. These materials are then characterized using a combination of rapid testing and predictive modeling to determine their properties and suitability. A key milestone is achieving a material conversion throughput of 0.1 m³/day, with components verified through pressure tests simulating the mechanical loads of rocket launches.
Equally crucial is the adaptive design software. Developing an adaptive design framework that can quickly update a component’s design based on the available materials. This system would need to be efficient enough to run on a standard laptop, enabling soldiers to make real-time decisions about the trade-offs between material quality, structural integrity, and mission requirements.
Material Property Prediction and Adaptive Design Framework
The program also focuses on developing an adaptive design framework characterized by low computational size, weight, and power (C-SWaP). The objective is to efficiently update a base design to accommodate structural changes for components with newly predicted material properties, ensuring they meet or exceed specified performance metrics. Proposers are encouraged to explore various evolving technologies, such as change propagation analysis and machine learning/artificial intelligence (ML/AI)-assisted finite element analysis (FEA), while alternative or integrated approaches are also welcome to meet the program’s goals.
The adaptive design framework assumes a fixed outer mold line (OML) and maximum flight loads for the government’s sounding rocket design. Proposers are challenged to develop a trained model capable of rapidly (within one hour) updating the design, confirming its viability, and predicting impacts on performance metrics like range based on the available materials. The designs should be manufacturable within the complete system CONOPS, integrating the target manufacturing approach, and require the production of demonstration components to validate both material properties and design performance.
DARPA wants field-deployable tools that can run on standard laptops, allowing engineers or even soldiers to modify rocket designs based on the material properties they have available. This means making real-time trade-offs between payload, range, and structural resilience, empowering mission-tailored manufacturing in austere conditions.
From Discarded Metals to Aerospace-Grade Components
The process begins by taking in scrap metal from forward-operating bases. At the University of Miami’s Advanced Materials Innovation Lab, engineers melt these materials into ingots, which are then ground into fine powder using ball mills and lathes. An inductively coupled atomizer spheroidizes the powder to ensure it is printable. With this powder, the team can use metal 3D printing to fabricate high-strength, lightweight pressure vessels suitable for sounding rockets.
Material Families and Processing Parameters: Unlocking the Potential of Diverse Feedstocks
The R2 program adopts a comprehensive classification system to organize and process a wide range of salvaged materials, each grouped into distinct material families based on their composition and processing requirements. These families include metals, ceramics, plastics, composites, and natural materials—each further categorized by its base material. For example, metals are identified by their dominant elements like iron (Fe), aluminum (Al), nickel (Ni), and titanium (Ti); ceramics by compounds such as aluminum oxide and yttrium-stabilized zirconia (YSZ); plastics by polymer groups like PVC, PEEK, or polycarbonate; and composites by resin-reinforcement combinations like epoxy with carbon fiber. Even organic feedstocks such as wood or paper are categorized based on primary compounds like cellulose.
Each class of material—metals, ceramics, plastics, composites, and natural materials—is studied for its unique processing needs and limitations. The program classifies materials by family, purity, and form, allowing for a broad domain of applicability. Models are then trained to predict mechanical properties like yield strength, thermal resistance, and ductility. These predictions feed into design frameworks capable of adjusting dimensions or geometries of parts to maintain structural integrity even with lower-quality materials.
In addition to composition, the purity and form of the material play critical roles in determining its processability and suitability for structural applications. Purity refers to the percentage of the base material within the mass of a given material stream—higher purity typically correlates with more predictable mechanical performance. Material form describes the condition in which the material enters the conversion process—whether it is in bulk (e.g., armor plates), particulate (e.g., ground scrap), wire, or powder form. The flexibility of the R2 program lies in its ability to handle not just single, clean material types, but also blended streams containing varying compositions and forms—thus minimizing the need for time-consuming cleaning or sorting at the point of need.
To accommodate this diversity, the R2 framework emphasizes defining the domain of applicability for each proposed material-processing approach. This domain reflects the range of material streams a technology can handle, both qualitatively and quantitatively. Metrics like density, elastic modulus, melting point, and grain size distribution help delineate the domain and ensure that a wide spectrum of material types—from shredded aluminum aircraft panels to mixed plastic waste—can be processed reliably. Proposers are encouraged to cast a wide net, designing systems capable of dealing with real-world unpredictability in material quality and origin, while also specifying the limitations and constraints of their approach.
Equally important is the characterization of these salvaged materials to ensure reliable performance in aerospace applications. The R2 program calls for advanced material informatics to predict key mechanical properties—such as tensile strength, ductility, and fatigue life—based on a given material stream. This will require not only updated databases and statistical models but also real-time analysis tools like torque sensors during extrusion or rapid hardness testing post-processing. By integrating such data-driven methods into the material conversion pipeline, R2 aims to create an agile, predictive design system—one capable of transforming discarded materials into high-performance structural components on demand, in any environment.
Inside the Process: From Scrap to Spaceflight in Four Steps
The R2 initiative brings circular engineering to life through a novel four-step workflow:
1. Scrap Collection
Decommissioned systems from forward bases—ranging from armored plates to aircraft skin—are harvested for their high-quality alloys. These materials are fully traceable and meet or exceed original military specifications.
2. Material Conversion
Collected scrap is melted into ingots and mechanically ground into fine particles using high-precision tools like a ball mill. An inductively coupled atomizer is used to spheroidize these particles into uniform metal powder ideal for additive manufacturing. Developing technologies that can transform diverse, often contaminated, materials into usable forms. This might include processes like friction stir extrusion of wire from shredded aluminum or the conversion of pulverized glass and metal into new, structurally sound components. R2 aims to demonstrate material conversion at a rate of 0.1 m³/day from scavenged and processed feedstock. This will be verified through iterative design trials and pressure testing of representative rocket motor chambers to simulate peak load survivability.
3. Additive Manufacturing
This metal powder is fed into industrial-grade 3D metal printers to fabricate pressure vessels, which are core structural elements in sounding rockets. These vessels must endure internal pressures and vibrations during launch, making them excellent test cases for performance validation.
4. Quality Assurance
At the University of Miami’s Advanced Materials Innovation Lab, each fabricated part undergoes intensive mechanical and structural testing. This includes pressure testing, ultrasonic inspections, and material composition analysis to ensure aerospace readiness.
Advancements in material conversion techniques and a better understanding of how contaminants affect materials could unlock new possibilities for using widely available, lower-risk materials. This would also improve the supply chain’s resilience and reduce the energy footprint associated with material processing. The R2 program seeks to open these new avenues, making it possible to utilize scavenged materials for structural applications in challenging environments.
Characterization and Prediction: The Science Behind the Magic
DARPA’s Rubble to Rockets (R2) program is charting a bold path toward redefining how materials are sourced, processed, and deployed in high-performance aerospace systems. Central to this vision is the use of material informatics and advanced manufacturing technologies to transform irregular, scavenged inputs into structurally sound, mission-ready components. The initiative emphasizes a rapid, iterative design approach, where components are not only fabricated quickly but also validated through rigorous subscale pressure testing. Ultimately, the program aims to demonstrate that even pulverized or contaminated vehicle frames, building debris, and complex metallic waste can be converted into reliable feedstock for aerospace applications.
Material informatics plays a central role in the R2 program. By leveraging AI-assisted finite element analysis (FEA), change propagation algorithms, and statistical models, R2 researchers can predict how unknown or mixed materials will behave under stress. Rather than conducting full characterization, which is time-consuming and often infeasible in the field, the focus is on estimating conservative bounds for performance. These bounds are enough to adapt existing designs on the fly while maintaining mission safety.
Moreover, the R2 design framework is being optimized for low size, weight, and power (SWaP), allowing rapid iteration even on basic computing hardware. The framework assumes fixed outer mold lines and mission load profiles, allowing for flexibility in internal architecture while meeting flight requirements like a minimum range of 35 km.
A Phased Roadmap for Real-World Impact
DARPA’s R2 program is structured across multiple phases. The initial 18-month base phase focuses on pristine, local materials and establishing end-to-end proof-of-concept for material conversion and adaptive rocket design. The second phase, also 18 months, will introduce mixed and less pristine material inputs, challenging the system’s robustness and refining the models.
Phase 1, a foundational 18-month effort, will focus on pristine materials to establish proof-of-concept. The primary goal is to create a deployable manufacturing platform that can predict material properties and dynamically adapt sounding rocket designs—particularly those within the 200–350 mm diameter range—based on the behavior of the feedstock. This phase will also refine processing methods such as friction stir extrusion, a technique already showing promise in converting shredded aluminum into usable wire, and introduce advanced tooling that accommodates wide variability in material quality and form.
Phase 2, also spanning 18 months, shifts the challenge toward converting less pristine, more complex materials. It will test the resilience of the R2 framework against real-world conditions—materials with unknown composition, embedded contaminants, or degraded mechanical properties. This phase aims to further enhance the platform’s adaptability and reliability.
The final, Phase 2 Demonstration, envisioned as a live launch of a sounding rocket built entirely from converted scrap, will serve as the ultimate validation of the system’s full-cycle capability—from battlefield rubble to a functioning flight system. It would culminate in a live demonstration: launching a sounding rocket entirely built from repurposed scrap. If successful, this would mark a transformative moment in military logistics, showing that high-performance equipment can be assembled from rubble in theater.
To meet DARPA’s ambitious vision, competitive proposals must demonstrate end-to-end integration: innovative material conversion technologies, in-line characterization systems, and design tools capable of quickly adjusting to material variability. These systems must accommodate a broad range of material families—including metals, plastics, glass, and composites—while being lightweight and rugged enough for field deployment. Proposals must also detail how these systems fit into larger operational frameworks (CONOPS), supporting not just rocket manufacturing but broader applications like emergency infrastructure, unmanned systems, and space-based platforms. The future of resilient, sustainable defense manufacturing is here—and it’s being built one recycled bolt at a time.
Beyond Rockets: Strategic and Sustainable Impact
The implications of R2 go well beyond rocket science. At its core, the program is about building resilience and adaptability in military and aerospace logistics.
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Operational Autonomy: In conflict zones or disaster-hit regions where traditional supply lines are compromised, mobile R2 units could provide on-demand manufacturing using scavenged materials.
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Cost Efficiency: By recycling high-quality scrap, the program reduces material procurement costs by as much as 80%, while also shrinking the carbon footprint of defense manufacturing.
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Versatility: R2’s adaptive framework has potential applications in producing spare parts for ships and aircraft, repairing damaged infrastructure, and even supporting extraterrestrial construction for habitats on the Moon or Mars.
Beyond its battlefield applications, R2 could have ripple effects across industries such as aerospace, construction, and disaster relief. The ability to convert waste into high-performance materials would reduce the environmental impact of defense operations, lower costs, and decentralize production. It also aligns with growing global interest in sustainable engineering, as highlighted by student engineers like Reese Simancek and Mary Goncharenko, who see the program as a launchpad for careers in green innovation.
DARPA program manager Hunter Martin encapsulates this vision:
“We aim to make manufacturing possible from anything, anywhere, at any size. It’s about resilience through material independence.”
Educating the Next Generation of Circular Engineers
This initiative also serves as a real-world training ground for aspiring engineers. Students at the University of Miami, including mechanical engineering senior Reese Simancek, are gaining invaluable hands-on experience in sustainable aerospace technology.
“This project merges circular design with aerospace innovation. It’s not just academically rewarding—it’s the future of green engineering,” said Simancek.
Fellow student Mary Goncharenko echoed the sentiment:
“Being involved in something that connects 3D metal printing, sustainability, and space applications has shaped the direction of my career.”
The Future of Military Manufacturing
Looking ahead, DARPA aims to scale the R2 model to include a wider array of materials—composites like carbon fiber, advanced polymers, and even natural materials like cellulose-based composites. Future phases could see mobile recycling labs deployed in active conflict zones, and on-orbit manufacturing using scrap collected in space.
DARPA’s Rubble to Rockets program exemplifies a new vision for agile, resilient logistics. By combining additive manufacturing, advanced materials science, and AI-driven design, R2 could render supply chain vulnerabilities a thing of the past. In the future, discarded equipment and battlefield debris might not be waste—they might be the raw materials for the next mission-critical launch.
This is not just a technological shift; it is a paradigm shift that could redefine the future of warfare, logistics, and sustainability. The program may ultimately redefine how we approach both defense logistics and global sustainability, proving that resourcefulness can be just as strategic as firepower. As Professor Tomonto points out:
“Why mine asteroids when we have mountains of aerospace-grade scrap right here on Earth?”
