U.S. Army Research Office
P.O. Box 12211
Research Triangle Park, N.C. 27709-2211
Commercial: (919) 549-4362
Fax: (919) 549-4354
Mechanical Sciences basic research is making significant contributions to the sustainment and advancement of Army aviation, ground vehicles/equipment, guns, armor, and other systems. Fundamental investigations in the areas of solid mechanics, structures and dynamics, combustion and propulsion, and fluid dynamics take advantage of major scientific and engineering opportunities to ensure that required future Army capabilities can be achieved.
The Mechanical Sciences Division supports the following research areas:
Dr. Ralph A. Anthenien
Dr. Matthew Munson
Research in fluid dynamics supports the development of improved or new technology for advanced helicopters, small-gas turbine engines, improved airdrop (parachute) systems, maneuverable high-speed missiles and high-performance gun-launched projectiles, and miniature unmanned air vehicles. While basic research studies that address the fundamental flow physics underlying these devices are solicited, innovative research in the specific topical thrust areas listed below is especially encouraged.
Vortex-Dominated Flows—In contrast to fixed-wing aircraft, rotorcrafts always operate under the influence of their own wakes. The prediction of rotor performance, vibratory loads, and blade-vortex interaction noise depends strongly on the accurate prediction of the rotor wake; the prediction methodology of this wake remains one of the major challenges in fluid mechanics. Current computational fluid dynamics (CFD) approaches are computationally intensive, especially for Eulerian methodologies where the vorticity diffuses numerically through the grid points and makes predication inaccurate. The process by which vorticity is shed by the blade and rolls-up to form vortex filaments is not now adequately simulated for rotorcraft load distributions. In fact, under certain flight conditions, multiple vortices are observed to form due to negative lift over the blade tip. The application of nonintrusive optical diagnostic techniques should yield new phenomenological understanding for the study of multiple vortices, wake structures, and wake development. New numerical algorithms or different techniques to increase accuracy and reduce the computational requirements are required.
Unsteady Aerodynamics—A high level of unsteady flow, which cannot be adequately predicted by steady or quasi-steady approaches, can characterize the flow field around many modern Army weapons systems. One classical example of very high Army relevance occurs on the retreating blade of a helicopter rotor, where the high angles of attack experienced by the retreating blade of the helicopter rotor leads to boundary-layer separation followed by load and pitching-moment overshoots. Mild separation causes increased vibration and reduces performance, while severe dynamic stall leads to unacceptably large vibratory loads and limits forward flight speeds, load, and maneuver capabilities. The physics of this flow phenomenon are known to depend on the Mach and Reynolds numbers of the flow, and hence, future research in this area needs to be performed under realistic flight conditions. Improved theoretical and numerical simulation is needed for understanding the unsteady separation process and evaluating concepts for separation control. The simulations must be capable of accounting for transition of the boundary layer (and under some circumstances, the transition in the separating free shear layer). Detailed experimental measurements of velocity and pressure are needed in the separating region for the fundamental understanding the separation process, the development of new turbulence models valid during the stall process, and the validation of numerical simulations; here, the current focus is on quantitative flow field measurements rather than merely quantitative measurements on the airfoil surface. These measurements will probably require the use of new nonintrusive optical methods. Combined experimental and numerical efforts toward control of unsteady separation using passive and active flow control (including the emerging field of Microadaptive Flow Control) are also sought.
A second example of the importance of unsteady aerodynamics occurs on maneuvering missiles and projectiles. As future emphasis in flight vehicle control and "smart" systems pervades munitions design, advances in aerodynamic phenomena, such as dynamic high-alpha separation, vortex shedding, control surface/vortex interaction, divert thruster/vehicle interaction, roll control stability, and propulsion system integration will be required. New composite material vehicles will have stringent thermodynamic limits and enhanced nonlinear aero elastic response to maneuver forces. Smart structures and micro-electro-mechanical systems (MEMS) technology will redefine control strategies, control surface shape and control surface dynamics, consequently driving fluid dynamics into new areas of research. All of these developments require the prediction and experimental verification of complex nonlinear transient flow fields. This will require improved CFD for turbulent flow separation prediction, large eddy simulation, vehicle vortex interactions, and accurate computations of gross flow field response to MEMS boundary layer flow perturbations. Parallel developments in experimental techniques will be required to measure these complex flow fields to help verify and guide the predictive technology.
Microadaptive Flow Control—Microadaptive Flow Control (MAFC) technologies enable control of large-scale aerodynamic flows using small-scale actuators. MAFC technologies combine adaptive control strategies with advanced actuator concepts like microscale synthetic jets; MEMS-based microactuators; pulsed-blowing, plasma actuators; and combustion actuators. These techniques are used to cause the delay or prevention of fluid flow separation, induce flow separation in previously unseparated flow, alter supersonic flow shock structure, or otherwise alter the large-scale flowfield and provide overall system benefit. Army systems for which MAFC is currently being investigated include on-blade controls; dynamic stall control on helicopter rotor blades; separation control for drag and buffet reduction on helicopters; surge and stall control within Army gas turbines; and dispersion reduction and terminal guidance of subsonic, transonic, and supersonic Army projectiles.
While recent successful demonstrations of the efficacy of MAFC technology have taken place, much of this research has tended to be somewhat Edisonian in nature. Basic research needs to enhance and focus the adoption of this technology to include developing a fundamental understanding of the method by which MAFC actuation alters the overall flowfield, developing robust and efficient MAFC actuators featuring greater control authority and higher bandwidth, developing computational analysis methodologies capable of accurately and efficiently predicting the effect of unsteady MAFC actuation on the entire flowfield, and integrating all these technologies into Army systems.
Dr. Asher Rubinstein
The light, lethal, survivable, continental United States (CONUS)-based modern Army with quick power projection capabilities around the globe has abiding interest in building the most effective fixed and mobile assets with advanced materials and systems. Weapons, platforms, ammunition, and ground structures are designed with severe weight and volume restrictions and are frequently limited by material strength and failure. Innovative use of material combinations for specific applications necessitates understanding the behavior of materials and structures under complex and severe constraints. Solid mechanics research plays a crucial role in the prediction of strength, damage initiation and progression, and failure of Army material systems under extreme loading conditions, such as blast and impact. Two major research aims in solid mechanics are to reduce development cost by minimizing the need for expensive testing and to optimize performance. The program seeks approaches based on the underlying physics of solids that form the foundation of optimization tools to enhance performance while minimizing weight and volume for the design of actual systems. The program focuses on the material and system response to blast, shock, impact, and penetration as well as the mechanics of heterogeneous systems including computational modeling-based Solid Mechanics Research. Thrust areas that are related to the development of better protective systems against blast and impact loading are directly related to the challenges facing the current and future Army. Under these conditions, the Army faces research problems with the unique constraints of very high strain rates, large deformations, high pressures, and rapid changes in temperature. Hence, a fundamental understanding of the behaviors of a variety of complex materials and systems, including engineered materials and soft human tissue, is needed. Research approaches should consider the topological effects (both micro and macroscale), specific material geometry, layering, and interface properties on the response to blast and impact loading. In addition, it may also address nontraditional concepts including nanotechnology, biologically inspired hierarchical structures, active protection, and the functional degradation of electronic components. Interrelated analytical, experimental, and computational formulations are needed to address these difficult multiphysics problems. Predictive models, validated by well-characterized experiments, are needed to identify dominant mechanisms at relevant scales.
Blast, Shock, Impact, and Penetration—This research topic addresses the need to understand the response of Army assets to impact and explosive detonation. It integrates approaches based on finite deformation, high pressure and high-strain rate, damage, and failure mechanics. Research should be conducted through a combination of physically based experiments, analysis, and computations. No single material will fulfill all of the Army's functional requirements. Therefore, combinations of materials such as polymer-, metal-, and ceramic-matrix composites, ceramics, metals, active materials, and functionally graded materials will be needed to achieve the desired thermo-mechanical response. The complexity of Army systems comprised of these materials is compounded by their highly anisotropic and heterogeneous nature, and the severe gradients and complex stress states resulting from blast and impact loading environments. Paramount to this effort is a better understanding of the mechanics of interfaces and impact mechanisms, such as high velocity behaviors that might occur at the penetrator/target interface or within developing cracks at macroscopic and microscopic scales. An important aspect of this research area is the deformation and fracture of materials under high-strain rates (up to 107 s-1), large strains (up to 500 percent), high temperatures (up to the melting point), and high pressures (up to 5 GPa). Innovative research on processes in materials and structures that absorb energy, deflect penetrators, and/or laterally disperse momentum is strongly encouraged.
Blast and impact into brittle materials presents special challenges due to cracking and comminution of material ahead of the penetrator, high-speed granular flow of comminuted material, and the mixing of eroded penetrator material and comminuted target material. Ceramics and geological materials exhibit extreme sensitivity to defects and loading histories, which may result in highly rate dependent failure strengths and the propagation of failure waves. Metals are susceptible to inelastic deformations leading to ductile failure under low to medium loading rates, but transition to more brittle behavior under higher loading rates. In addition, heat generation and thermal softening occur in metals, further complicating the behavior of these materials under extreme loads and loading rates. Blast and impact of composite systems present still another set of challenges that result from their complex microstructure, material boundaries, and the number of different and coupled failure modes that may occur. Since personnel protection is a key objective for Army platforms, an understanding of the response of biological tissue to blast and impact is essential.
All of this requires greatly improved understanding, effective modeling, and efficient computational schemes. Because blast and impact events often involve erosion and sliding of both the projectile and the target, explicit modeling of these processes with friction-based theories and computational techniques are essential. Computational methods for treating discontinuities in a three-dimensional context are required. These methods must concentrate not only on the techniques required to track a moving boundary, but also on the relevant physics and mechanics associated with those surfaces. Examples might include boundaries between dissimilar materials, shock fronts, elastic/plastic boundaries, phase boundaries, shear bands and cracks, as well as penetrator/target interfaces. Constitutive models should be three-dimensional and should allow for system nonlinearities.
In blast and impact environments, complex interactions between the shock and release waves usually initiate damage mechanisms in the target; accurate modeling of the target behavior will require controlled, high-fidelity experiments. Therefore, innovative experimental techniques that incorporate high-speed data acquisition and imaging are necessary to capture the deformation processes and relative motion between surfaces. Accurate experimental techniques are required to delineate the nature, timing, and evolution of damage and failure in heterogeneous materials. An important aspect of this area of research is the development of novel experimental techniques that can be used to generate data for the wide ranges and combinations of strain rates, strains, temperatures, and pressures of interest.
Mechanics of Heterogeneous Systems—The mechanics of heterogeneous structures involves the development of integrated analytical, computational, and experimental approaches to investigate the response of hybrid structures that may include combinations of high strength and lightweight engineered composites, ceramics, and functionally graded materials. Heterogeneity at all scales should be considered from nanomaterials to systems created through combinations of different materials at larger scales. Experimental and computational techniques are needed to optimize material microstructure as well as the topology of systems to provide the desired structural response for specific boundary and loading conditions. Physically based structural design guidelines for energy absorbing structural systems comprised of tailored combinations of materials and heterogeneities at different length and time scales are sought. There are continuing technology barriers that need to be overcome if reliable Army structures such as helicopters, ground vehicles, bridges, and weapons systems are to be designed, manufactured, and maintained over a long period of time. Of special interest to the Army is the thermo-mechanical response at strain rates encountered in high-speed impact or explosive loading. Probabilistic as well as deterministic approaches are encouraged. Phenomena of interest are wave propagation, scattering, dispersion, damage evolution, and failure.
At appropriate length and time scales, the quantitative prediction and measurement of parameters related to dominant heterogeneities and mechanisms are needed for specific material systems in order to relate nano and micro effects to the macroscale. Deterministic and statistical scaling methodologies for toughness, strength, and geometrical effects that account for the multitude and variability of heterogeneities such as interfaces, interphases, particulate dispersion, fiber volume fraction and distribution, constituent shape, and their combined effects on failure are needed. Innovative methods and models to control material properties and damage by graded interfaces, coatings, and mechanical impedance mismatches are required. Constitutive relations for multiscale mechanisms should include failure and damage criteria, which are mechanism-based and experimentally verifiable. The determination of universal scaling laws that can be used to bridge physical scales would greatly enhance our understanding and prediction of phenomena such as inelastic deformations, localization, distributed damage and failure, and fragmentation.
Computational Modeling Based Solid Mechanics Research—Over the past decades, the finite element methods that were developed in the mechanics community have had a tremendous impact on engineering practice and Army designs. Although these methods have been highly effective for linear and some nonlinear analyses, substantial breakthroughs are needed for failure modeling and representations of blast and impact live-fire tests. Commercially developed algorithms that rely on the deletion of elements to model the nucleation and propagation of cracks are inadequate. These algorithms are highly sensitive to the size and mesh arrangement and distribution. Furthermore, no convergence theories or even empirical evidence of convergence has been obtained so far for these methods. New theories are needed that can overcome the limitations of traditional continuum fracture models that are based on crack-tip singularities. New principles need to be devised for the construction of failure surfaces and cohesion strength. New methodologies are needed to account for energy dissipation due to crack progression, large-scale yielding, and interfacial separation. It has become important to be able to develop material properties in terms of subscale models, because with the rapid advent of new material systems, testing is becoming prohibitively time consuming and expensive. New theoretical approaches are needed to develop hierarchical methods for failure that account for the inherent statistical aspects of failure. Methodologies that explore fracture processes at the microscale and relate them to the meso and macroscopic levels should be investigated. Computational models for the creation of free surfaces that are mesh independent and that incorporate evolving time-dependent boundary conditions and physically based failure initiation criteria need to be developed. These computational models should capture the complex interactions of failure processes and defects in three dimensions. To achieve the requisite accuracy in three-dimensional problems, effective adaptive methods that can treat crack propagation, shear band formation, and other failure modes are needed. The capability to model fragmentation, contact, and penetration is also of strong interest.
Complex Dynamics and Systems
Dr. Samuel Stanton
The Complex Dynamics and Systems Program emphasizes fundamental understanding of the dynamics, both physical and information theoretic, of nonlinear and nonconservative systems as well as innovative scientific approaches for engineering and exploiting nonlinear and nonequilibrium physical and information theoretic dynamics for a broad range of future capabilities (e.g. novel energetic and entropic transduction, agile motion, and force generation). A common theme amongst all programmatic thrust areas is that systems of interest are "open" in the thermodynamic sense (or, similarly, dissipative dynamical systems). The program seeks to understand how information, momentum, energy, and entropy is directed, flows, and transforms in nonlinear systems due to interactions with the system's surroundings or within the system itself. Research efforts are not solely limited to descriptive understanding, however. Central to the mission of the program is the additional emphasis on pushing beyond descriptive understanding toward engineering and exploiting time-varying interactions, fluctuations, inertial dynamics, phase space structures, modal interplay and other nonlinearity in novel ways to enable the generation of useful work, agile motion, and engineered energetic and entropic transformations. Further information on the current scientific thrust areas are detailed in the paragraphs that follow.
Dynamics of Nonlinear and Nonconservative Systems – Classical dynamics has produced limited fundamental insight and theoretical methods concerning strongly nonlinear, high-dimensional, dissipative, and time-varying systems. For over a century, qualitative geometric approaches in low-dimensions have dominated research in dynamics, dissipative processes are mostly relegated to phenomenological models, and reduced-order-modeling of high-dimensional dynamics are often premised on empirical and statistical model fitting and are incapable of capturing the effects of slowly growing instabilities and memory. Experimental efforts have similarly faded. There is prescient need for a return to fundamental investigations and new theoretical and experimental frameworks for high-dimensional nonlinear and nonconservative systems. At the same time, however, a number of exciting and new research problems are emerging. Research in this thrust concentrates on (but is not limited to):
- Spatially Extended and High-Dimensional Dynamics Far-from-Equilibrium – Develop novel theoretical and experimental methods for understanding the physical and information dynamics of driven dissipative continuous systems and novel reduced-order-modeling methodologies capable of retaining time-dependent and global nonlinearities. Novel research pertaining to the analysis and fundamental physics of time-varying nonlinear systems and transient dynamics is a high-priority. Programmatic interests also include unifying advances in nonequilibrium statistical mechanics with Statistical Energy Analysis (SEA), developing new methods for vibratory regimes outside the scope of overly-simplistic SEA assumptions (e.g. non-trivial modal overlap, mid-frequency range problems, and non-Gaussian stochastic processes), and novel research in experimental structural dynamics. This thrust also has special interest in pioneering research on creating and controlling nontraditional nonequilibrium critical phenomena and critical dynamics.
- Nonsmooth Dynamics and Interactions – Nonsmooth dynamics, for even a single degree-of-freedom, are extremely counter-intuitive and poorly understood yet they arise in many Army-relevant contexts spanning wave propagation in interconnected structures, autonomous system dynamics (e.g. locomotion and jumping), suddenly applied loads, etc. Novel and fundamental investigations concerning the experimental and theoretical physics for a variety of nonsmooth dynamical systems are of interest. Programmatic interests herein extend to the emerging field of experimental and theoretical terradynamics, especially in the domain of low-inertia systems and novel, non-wheeled and biomechanical propulsion mechanisms where Bekker's theories and assumptions are invalid.
- Formalisms for Engineering Complexity and Resilience – Developing an engineering science of complexity and resilience to understand complex engineered systems as well as enabling the next generation of engineering systems capable of exhibiting hallmark features of complex systems (e.g engineering robustness, fragility, propensity for self-organization) requires new mathematical methods, uncertainty propagation techniques, and clever leveraging of many recent advances and insight from complex systems science. Proposals taking a fundamental and rigorous scientific approach are encouraged.
Passive Dynamics and Underactuation – This scientific thrust seeks to develop deeper understanding through supporting theory and experiment of the role of embodiment and dynamics on a physical system's capability to process information and transform energy and entropy. Generally, this thrust strongly leverages advances in, and approaches from, sensory biomechanics, neuromechanics, underactuated systems theory, and mechanical locomotion dynamics to understand the motion of both articulated and continuum dynamical systems operating in highly-dynamic environments. The scientific principles sought, however, are not limited to biological movement and manipulation. Proposals are strongly encouraged that view morphology in an abstract sense. For example, understanding morphology as a system's symmetry, its confinement (e.g. chemical reactions), or its coupling topology.
Force Generation, Work and Power in Nonequilibrium Dynamical Systems – This thrust pioneers novel and innovative approaches, grounded in nonequilibrium and dissipative dynamical systems theory, for novel thermodynamic "engines" and new ways of generating forces, producing useful work and power, and transforming information to energy (e.g. Szilard engines) in both artificial and biological systems. Recently, advances in physics have suggested that nontraditional work cycles featuring non-ergodic intermediate steps (where processes cannot relax or are prohibited from reaching equilibrium) can potentially exceed Carnot efficiency bounds. However, more research is needed to explore this novel regime, connect ideas with modern concepts in information dynamics, as well as to perform experiments. Other major interests include enabling novel synthetic emulation capabilities by exploring universal features in biological "prime movers" (e.g. molecular motors, actin, dynein) as well as principles underlying biological force generation, dissipation, and load transfer via the nonlinear dynamics of muscles.
Strategic Program Challenges – strategic program challenges focus on questions relevant to the programmatic scientific focus areas deemed beyond the scope of single investigator awards. The challenges emphasize high-risk, high-reward exploratory research to create breakthroughs, push science in truly novel directions, or to support mathematical abstractions and precise physical foundations for emerging technologies deemed likely to be of significant future Army and DoD impact. Potential investigator teams are encouraged to contact the program manager for further information concerning any Strategic Program Challenge topic.
For each topic, proposed efforts should be limited to 48 months and $1.5 million. There is no formal limit on the number of investigators, but white papers should clearly indicate significant, complementary, and meaningful intellectual commitment by each proposed team member. Potential individual investigators interested in a particular aspect of any topic are welcome to discuss single investigator proposals with the program manager. Related single investigator efforts will be considered, with support at a commensurate level.
Topic 1: Energetic Versatility of Muscles: Principles and Emulation
Discern, through both theory and experiment, the fundamental physical principles underlying the energetic versatility of muscles in dynamic operating conditions (e.g. force generation, shock absorption, energy dissipation, power conversion and distribution etc.). Of complementary interest are novel experimental approaches with sustained in-vitro electromechanical coupling as well as compelling new ideas to leverage biophysical principles to potentially engineer new classes of soft active matter exhibiting muscle-like energetic versatility.
Topic 2: Controlling Hyperelastic Matter
Bring together soft condensed matter physics, continuum mechanics, neuromechanics, and under-actuated systems theory to generate novel frameworks for directing complex spatial motions and wave propagation capabilities within soft continua with nonlinear material properties. Theoretical principles are expected to be integrated with novel experimental platforms, possibly leveraging advances in printed programmable matter. New interests relevant to this topic include coupling advances in printing bionic programmable matter with new understanding of scaling and regeneration of self-organized patterns to push towards new capabilities to engineering biological plasticity.
Topic 3: Theory of Morphological Energetics
Develop a formal abstraction of the principles underlying the efficiency of information processing, control, and energetic transformation on the intricate coupling with, and exploitation of, a physical system's shape (either articulated or amorphous), topological structure (functional morphology), and nonlinear dynamics (including transient and non-smooth dynamics). Emphasize the less-considered dynamics of energy and entropy transformations in the context of the challenge objective and present generality of the results across a broad range of data sets and experimental test beds.
Topic 4: Control and Creation of Critical Dynamics
Steer statistical physics towards a science of the artificial. The goal is to develop an experimentally tested theoretical framework for controlling and creating new types of critical dynamics, phase transitions, and universality classes by bringing together theory and physical principles in statistical dynamics with control and dynamical systems theory. Questions of interest for this challenge include: Can we develop the concept of an active universality class? Can we dynamically stabilize, through feedback, nonequilibrium states of matter that have no equilibrium counterparts? Can renormalization group theory be unified with control theory through geometry? What is the role of information dynamics in the control of critical dynamics? Proposed efforts should have a strong experimental component to test theoretical abstractions.
Propulsion and Energetics
Dr. Ralph A. Anthenien
Propulsion and Energetics research supports the Army's need for higher performance propulsion systems. These systems must also provide reduced logistics burden (lower fuel/propellant usage) and longer life than today's systems. Fundamental to this area are the extraction of stored, chemical energy and the conversion of that energy into useful work for vehicle and projectile propulsion. In view of the high temperature and pressure environments encountered in these combustion systems, it is important to advance current understanding of fundamental processes as well as to advance the ability to make accurate, detailed measurements for the understanding of the dominant physical processes and the validation of predictive models. Thus, research in this area is characterized by a focus on high-pressure, high-temperature combustion processes and on the peculiarities of combustion behavior in systems of Army interest.
Engines—Research on combustion in engines is focused on intermittent, reacting flows encountered in diesel combustion chambers and on continuous combustion characteristics of small, gas turbine combustors. Optimizing engine performance, through understanding and control of in-cylinder combustion dynamics, while retaining high-power density, is a major objective. This focus leads to a strong emphasis on fuel injection processes, jet break-up, atomization and spray dynamics, ignition, and subsequent heterogeneous flame propagation. Research on heterogeneous flames requires supporting study into kinetic and fluid dynamic models, turbulent flame structure, soot formation and destruction, flame extinction, surface reactions, multiphase heat transfer, and other factors that are critical to an understanding of engine performance and efficiency. An additional consideration is the high-pressure/temperature environment, encountered in advanced engines, which influences liquid behavior and combustion processes at near-critical and supercritical conditions. Of particular interest are investigations of fundamental characteristics related to highly stressed engines, such as elevated temperature combustion, accelerated mixing, and transient heat transfer. Engine performance degradation under low-temperature conditions, due to reduced fuel volatility, high-oil viscosity, poor atomization and vaporization, etc., is a major concern. Fundamental research is needed in many areas, including low-temperature physical and chemical rate processes, instantaneous friction and wear mechanisms, and combustion instability effects at low temperatures. With advances in sensing, modeling, and control architectures, it is becoming possible to further optimize the performance of combustion systems. Providing the foundations for such active control is also a major goal of the program.
Propellant Combustion Processes—Research on propellant combustion processes is focused on understanding the dynamics of the planned and inadvertent ignition and subsequent combustion of energetic materials used for propulsion in gun and missile systems and in ordinance. The program is also addressing the characterization of advanced energetic materials, e.g., those based on nanoscale structures and/or ingredients. Basic research is needed in several areas, including plasma- and laser-induced ignition; thermal pyrolysis of basic ingredients and solid propellants; flame spreading over unburned surfaces (particularly in narrow channels); surface reaction zone structure of burning propellants; chemical kinetics (including possible ion kinetics in the presence of plasmas) and burning mechanisms; propellant flame structures; characterization of physical and chemical properties of propellants and their pyrolysis products; and coupling effects among the ignition, combustion, and mechanical deformation/fracture processes with or without the presence of a plasma. The use of advanced combustion diagnostic techniques for reaction front measurements, flame structure characterization, and determination of reaction mechanisms is highly encouraged. This includes characterization of radiative and convective stimuli delivered by plasma injection sources as well as the thermal, kinetic, and mechanical responses of the propellant. Complementary model development and numerical solution of these same ignition and combustion processes are also essential. There is also need to understand the unplanned or accidental ignition of energetic materials due to stimuli such as electrostatic discharge, impact, friction, etc. This requires, for example, research on the processes of energy absorption and energy partitioning in the materials, the effect of mechanical damage on the ignition events, and other topics relating to the safety of energetic materials.