Reducing the weight of military vehicles has been of interest to the U.S. Department of Defense for decades. For land vehicles, the objectives historically have been primarily to reduce fuel consumption and costs and improve transportability. For naval vessels, lightweighting of superstructures also improves balance, maneuverability, and speed. For aircraft, weight is a critical determinant of performance, payload capacity, maneuverability, and range.
Reducing vehicle weight without compromising other important attributes such as survivability or payload capacity has traditionally been accomplished through the substitution of lightweight materials for heavier ones within conventional design configurations. However, this narrow perspective limits the possibilities for and the impact of lightweighting.
Today, in the face of new and evolving threats, improving the survivability of a military vehicle and its occupants has become more important than reducing fuel use. However, as has been seen in recent years in the deployment of land vehicles in Iraq and Afghanistan, the need to counter new threats has sometimes compromised other performance capabilities. For instance, the need to “uparmor” some vehicles to increase survivability has, by increasing their weight, reduced their maneuverability and transportability and increased their fuel requirements. Lightweighting can now be viewed as a means of restoring or even improving such vehicles’ maneuverability and transportability and reducing their fuel consumption.
To help it take fuller advantage of the benefits of lightweighting, the Department of Defense (DoD) asked the National Research Council (NRC) to assess the current state of lightweighting in land, maritime, and air vehicles and to recommend ways in which the use of lightweighting might be better implemented in military vehicles, but also to address commercial vehicles.
As part of its assessment, the Committee on Benchmarking the Technology and Application of Lightweighting was asked to consider both lightweight materials and lightweight design; the availability of lightweight materials from domestic manufacturers; and the performance of lightweight materials and their manufacturing technologies. (Manufacturing technologies are those used to manufacture materials as well as the components, structures, and other shapes made from the materials.) It was also asked to consider the “trade space”—that is, the effect that use of lightweight materials or technologies can have on the performance and function of all vehicle systems and components.
The committee began by assessing the relevance of the definition of lightweighting in the materials community. Particularly mindful of the need to consider lightweighting and the trade-space of vehicle attributes holistically, the
committee developed the following broad definition of lightweighting in military systems:1 Lightweighting is the process of reducing the weight of a product, component, or system for the purpose of enhancing certain attributes, notably (1) performance, (2) operational supportability, and (3) survivability.
In developing this broad definition, the committee wished to emphasize that lightweighting should be viewed as a means of achieving a variety of desirable features:
- Improved fuel economy that would reduce both fuel expenditures and the logistical support needed to supply fuel to forces deployed in remote and hostile locations;
- Better performance in the form of, for example, increased speed, mobility, maneuverability, range, and payload capacity;
- Better operational supportability in the form of, for example, better transportability, durability, repairability, and maintainability; and
- Improved survivability.
Lightweighting is critical to optimizing vehicle performance and capability and to reducing fuel use and costs. Lightweighting can also confer the benefit of flexibility and adaptability. For example, a vehicle that can be made lighter without compromising survivability provides the flexibility to add new capability—e.g., to add armor in a modular fashion or to add payload—without increasing weight beyond the original weight or even while maintaining an overall lighter vehicle. In general, vehicles can be adapted for different uses, such as responding to evolving threats.
Lightweighting encompasses the design, development, and implementation of lightweight materials, components, and other technologies as well as the capability to manufacture and produce such materials and components at reasonable cost.
Under the committee’s broad definition, lightweighting demands a true systems approach. A focus on only one vehicle attribute may result in a weight reduction but may miss the more significant benefits that could be attained through a more systematic consideration of lightweighting throughout a vehicle system’s design cycle. Lightweighting must be done at the systems level to ensure proper balance with all other critical requirements. Use of advanced, lightweight materials, and optimization of all materials and structural configurations at the systems level, are key to achieving optimal systems performance and the lightest weight.
A systems approach to design might consider not only the development and use of lighter (low-density) and high-specific-performance2 materials, but also:
- Creative architectural and component designs that provide multifunctionality;
- Manufacturing methods that enable the use of new designs and material combinations as well as the reduction of manufacturing defects (thus improving durability and service life);
- Research to improve understanding of materials’ response and failure mechanisms; and
- Enhancement and broader use of computational models that can accelerate the materials development and qualification cycle through integrated computational materials engineering.
The committee addressed its charge by reviewing illustrative examples of lightweighting in air, sea, and land vehicles, with a focus on military applications. It also considered some of the opportunities available to implement lightweight solutions. Although not definitive, the review found good examples of lightweighting implementation in military vehicles, but there is still much that can be done. Viewing lightweighting broadly, as defined by the committee, and at the systems level may help bring opportunities to light.
1 Although this definition also applies to civilian vehicles, the main focus of the report is military vehicles, and so the attributes of interest and the wording used are tailored for military applications.
2 For example, high specific strength, which is defined as strength divided by density.
The committee also identified barriers to further lightweighting, one of the most important of which involves the extended period required for materials development and qualification. “Gated” processes for developing new products or systems, such as those specified by the Defense Acquisition Guide and DoD Instruction 5000.02, require that technologies be relatively mature by the initiation of a program. Hence, the considerable time and cost required to reach the requisite level of maturity for a new material must be expended in the preacquisition phase, before a program is actually initiated. As a result, the development and qualification cycle for materials is often “out of sync” with the design cycle for vehicles, making it difficult to insert new materials early in the design cycle.
A second barrier to lightweighting is that the use of advanced materials, such as magnesium and titanium alloys and polymer matrix composites, can be hampered by high costs, manufacturing challenges, and the lack of domestic, commercially available supplies. It can even be difficult to obtain high-strength steels, which, when combined with manufacturing innovations, can contribute to reducing weight and enhancing performance.
Another important obstacle is that neither the specification of technical requirements for contractors nor the acquisition process for new vehicles and equipment promotes innovation. Detailed specifications offer no flexibility to meet performance requirements in creative ways. When several contractors are involved in the development of a vehicle or system, poor communication can result in less than optimal solutions. Moreover, development and acquisition programs for vehicles are often risk-averse, resulting in the exclusion of new technologies and materials that could contribute to lightweighting. Under these conditions, implementation of a systems approach can be severely impeded.
The committee developed the following findings and recommendations on approaches to better implement lightweighting solutions in aircraft, maritime vessels, and land vehicles.
DIGITAL DESIGN TOOLS FOR SYSTEMS ENGINEERING
Finding 1: One consequence of lengthy acquisition processes is that changes in threats and operational requirements in areas of conflict can outpace development of new military vehicles and vehicle technologies. The ability to keep up with evolving requirements could be improved by both reducing the time required for development and improving the capability to design flexibility and adaptability into vehicle systems. Both goals require increased capability in digital design, especially for the integration of materials and design configurations. Such capability could significantly improve the effectiveness of current systems engineering processes.
Recommendation 1:3 The DoD should initiate a program to develop and integrate high-fidelity models of materials, processes, and performance into a comprehensive digital system-design process for future air, maritime, and land vehicles. Although many individual models exist or are being developed, these models often are not integrated, and the focus of a larger organization such as the DoD is required to facilitate coordination.
Finding 2: In addition to the models themselves, a framework for their effective integration into the vehicle design environment is required. An important element of this framework is integrated computational materials engineering (ICME), a strategy that extends from materials design through structural design in an integrated fashion, thereby including the ability to design new materials as part of achieving optimal structural performance. In the committee’s judgment, ICME tools and methods offer the greatest opportunity to accelerate the development and validation of new materials and processes for lightweighting, which would bring the current lengthy development cycle for these new materials and processes more into line with the generally much shorter design cycles for vehicles and products. Although numerous programs and specific applications have demonstrated the feasibility and benefits of ICME, broad development and implementation will require comprehensive, sustained effort and investment, along with coordinated actions among numerous stakeholders, to have a significant effect on future components, vehicles, and systems.
Recommendation 2a:4 The DoD should expand its leadership role as a champion of integrated computational materials engineering. It should develop and lead a comprehensive, sustained, multi-agency ICME program, with some specific focus on lightweighting materials and technologies. The program should:
- Identify and support foundational engineering problems5 that specifically address lightweighting for air, maritime, and land applications;
- Foster the development and stewardship of national curated knowledge repositories relevant to light-weighting materials;
- Coordinate with other stakeholders in the training and education of an ICME workforce; and
- Support the development of a suite of predictive tools for materials manufacturing, sustainment, and maintenance. These should address processes, performance, and properties and should include physics-based materials models of behavior under extreme loading conditions.
Recommendation 2b:6 The DoD should foster the development, maturation, and advancement of physics-based materials models as well as numerical simulation tools and codes.
TRANSITION OF MATERIALS AND TOOLS INTO PRODUCTS
The rigorous, gated approaches taken to developing and certifying new technologies require that new technologies and materials be relatively mature by the time system architecture decisions are made. Extensive testing may be required to demonstrate this maturity. Because the time required for developing and certifying new materials is often longer than that for designing and developing product applications, strategies are needed to accelerate the application of new materials that have not yet been qualified.
The committee notes that the advanced technology demonstration (ATD) process has been very successful in introducing breakthrough technologies into DoD platforms and could be used to accelerate the introduction of lightweighting technologies into demonstration systems. A well-managed ATD can reduce the need for testing and compress overall development times, while including all requirements in the design. Thus, ATDs could help to rapidly bridge what has come to be called the “valley of death” between the development of a technology and its implementation in products and processes.
Finding 3: Advanced technology demonstration programs have, in numerous instances, proven to be successful in introducing breakthrough technologies into DoD platforms.
The risk with the ATD approach is the potential for unexpected consequences when using new materials, manufacturing techniques, and designs that have not been rigorously tested. This risk can be mitigated by requiring that all system-level and operational requirements be included in the design and application of new technologies, even if those ATDs address components rather than full-scale systems. Not shortcutting this portion of the approach can significantly reduce the risk to field operations that has been experienced with some ATDs.
By making it possible to design, produce, and evaluate entire vehicles and major components under real-world conditions, ATDs facilitate the use of the rigorous systems engineering needed to exploit the full potential of lightweighting.
Recommendation 3: The DoD should expand the use of ATDs to implement lightweighting technologies rapidly in air, maritime, and land demonstration platforms. To improve the transition value of ATDs for lightweighting, it
5 NRC. 2008. Integrated Computational Materials Engineering: A Transformational Discipline for Improved Competitiveness and National Security. Washington, D.C.: The National Academies Press. Available at http://www.nap.edu/catalog.php?record_id=12199.
is important that the DoD incorporate all system and operational requirements into projects, so that lightweighting technologies can be fully optimized from the outset.
Chapter 6 contains a list of possible committee-proposed guiding principles for developing effective light-weighting ATD projects.
MANUFACTURING CAPABILITIES AND AFFORDABLE MANUFACTURING TECHNOLOGY TO FACILITATE LIGHTWEIGHTING
Lightweighting of vehicles poses particular manufacturing challenges. Improvements are needed in joining technology; parts consolidation and miniaturization; tool-less fabrication of low-volume production parts; nondestructive examination methods; and virtual process modeling. Consideration must also be given to the production of structural commodities in particular forms (such as plates and resins), the capability for which may reside outside the United States. Enhancement of fabrication technology is also needed for advanced fibers and composite materials, which in some cases are also available primarily from overseas sources.
The declining domestic capability for manufacturing hampers the ability of the DoD and commercial organizations to achieve the integrated lightweighting solutions inherent in the committee’s definition of lightweighting. At the same time, support for the manufacturing capability needed for lightweighting could be part of a national strategy to rebuild cutting-edge manufacturing capabilities in the United States.
The committee believes that the DoD’s Manufacturing Technology (ManTech) program has an appropriate framework for the development of advanced lightweighting strategies. However, the current focus of ManTech projects is to address a tightly defined manufacturing challenge and show a direct transition to a specific military platform.
Domestic manufacturing capabilities for advanced materials and for military applications using them are limited or even declining in some areas, particularly when there is no parallel commercial demand for lightweight transportation systems. The boom-to-bust cycle that ties defense contractors to the DoD’s procurement cycle threatens the maintenance of a robust defense industrial base.
Aerospace defense contractors have benefited from using similar or the same materials and lightweighting technologies in defense and commercial markets, both of which are driven by the effect of weight on system capability and cost. For land combat vehicles, there is a parallel commercial market in heavy wheeled equipment and heavy trucks that may afford opportunities. The U.S. maritime industry also has the opportunity to benefit from military and commercial overlap, as indicated by the U.S. Navy’s joint high-speed vessel and littoral combat ship, which are derivatives of fast-ferry designs developed overseas.
The economic viability of fast ferries is extremely weight-sensitive. If a viable, national high-speed ferry network were to develop, it would have the potential to foster a domestic, competitive capability for manufacturing lightweight ships.
Finding 4: The cost of fielding military systems that incorporate lightweighting solutions is high in part because production volumes are low and performance requirements are highly exacting. The focus on reducing acquisition costs has resulted in increased reliance on foreign technology sources,7 thus eroding U.S. strategic manufacturing advantages. The problems are exacerbated by the lack of parallel commercial markets that could significantly reduce the costs of technology development and make initial investments more attractive.
7 “DOD Undertakes Crash Study on Defense Industrial Base,” Manufacturing & Technology News, May 31, 2011, Vol. 18, No. 9, pp. 1-2; “DOD Industrial Policy Shop Adds Manufacturing to Its Mission,” Manufacturing & Technology News, April 29, 2011, Vol. 18, No. 7, p. 7; “Rising Labor Costs in China Are Still 96% Lower Than Those in the US,” Manufacturing & Technology News, April 15, 2011, Vol. 18, No. 6, pp. 3-4.
Recommendation 4a:8 The DoD should establish broad manufacturing initiatives—using the ManTech program framework as a model—that encompass a variety of lightweighting strategies, materials, and technologies, with the goal of achieving quantum improvements in performance, affordability, sustainability, and reliability.
Recommendation 4b:9 In concert with other government agencies, the DoD should explore the merits and requirements of parallel commercial markets that could reduce the development and acquisition costs of military vehicles as well as accelerate the availability and use of lightweighting materials and technologies.
Finding 5: The committee believes that there remains insufficient high-level DoD awareness of and stratetic vision for ensuring sustained domestic supplies of materials that are essential to the realization of effective lightweighting and would facilitate revolutionary advances in military systems. Although there is growing recognition of the importance of individual metals and rare-earth elements, the domestic availability, supply, sustainment, maintenance, and manufacturing of lightweighting-enabling materials, such as high-performance SiC fibers, thick-section magnesium, and polyethylene fibers, must become targeted priorities of the DoD for lightweighting to become widespread.
One existing program, the Defense Production Act Title III program, includes a number of materials projects relevant to lightweighting, such as production of SiC powder for ceramic armor, low-cost titanium, and continuous-filament boron fiber, but does not include some of the materials and manufacturing processes that the committee believes would have the greatest impact on lightweighting.
The cost of advanced materials extraction, reduction, and processing can be prohibitive, and there is a lack of domestic manufacturing infrastructure to fabricate the primary metal alloys or the intermediate engineering forms, or to manufacture final, shaped products. This lack of infrastructure affects opportunities for use of lightweighting materials in defense and civilian applications.
Recommendation 5: In cooperation with other agencies, the DoD should establish a federal investment strategy that (a) determines which structural materials are most important to future lightweighting and (b) establishes the resources to ensure continuous development of these materials and their associated manufacturing processes.
As part of this holistic approach, the existing Title III program should be expanded to include a larger number of materials critical to lightweighting of military aircraft, vessels, and vehicles. In expanding the program, the DoD should recognize the need for the long-term, continuous development of these materials and of the manufacturing techniques and capacity needed to produce them.
In summary, the committee’s view is that lightweighting materials, design, and technologies could have far-reaching benefits: implementation of lightweighting as defined above not only would address optimization of military vehicles but also could have security and economic benefits for the nation:
- Energy use. Reduced energy consumption and cost for both military and commercial vehicles;
- Competitiveness. Increased competitiveness of future U.S. products stemming from system-level integration of materials science and engineering; and
- Jobs. Preservation and creation of high-end jobs in manufacturing and engineering.