U.S. Air Force Summer Faculty Fellowship Program

U.S. Air Force Summer Faculty Fellowship Program

U.S. Air Force Summer Faculty Fellowship Program

U.S. Air Force Summer Faculty Fellowship Program

AFRL/RQ Edwards AF Base, California

SF.30.03.B6678: Computational Studies of Energetic Materials for Rocket Propulsion ApplicationsComputational Studies of Energetic Materials for Rocket Propulsion Applications

Boatz, J. (661) 275-5364

This research focuses on the application of high-level quantum chemical computations to the study of advanced energetic compounds for space and missile propulsion applications. These calculations are used to predict the thermodynamic and kinetic stability, performance, spectroscopy, potential synthesis routes, reaction pathways, and other properties of candidate molecules. These results aid in the initial screening of new energetic compounds for subsequent experimental synthesis, characterization, and scaleup. Specific classes of compounds of interest include energetic ionic liquids, polynitrogen/high-nitrogen compounds, nanoclusters, and energetic solid ingredients. Because of the large size and complexity of many of the compounds of interest, utilization of high-performance computing methods and resources is an essential component of this research effort. A critically important resource for these studies is state-of-the-art high-performance computing systems made available to DOD researchers through the High Performance Computing Modernization Program.

Keywords: Energetic materials; Quantum chemistry; Computational molecular chemistry; High-performance computing

Eligibility: Open to U.S. citizens

SF.30.03.B6921: Advanced Polymer Composites for Propulsion Applications

Mabry, J. (661) 275-5857

The development of polymer nanocomposites and fiber-reinforced polymer matrix composites has resulted in significant improvement in thermal, mechanical, and physical properties in many aerospace applications. The property improvements enabled by these materials have resulted in their use in many defense-related applications. In addition to property improvement, production of functional composites at reduced cost is also desired. AFRL/RQ is recognized as a leader in the field of composite materials research. An opportunity exists for research in the area of polymer nanocomposites and fiber-reinforced polymer matrix composites. The Rocket Propulsion Division, Propellants Branch conducts both basic and applied research, leading to the development of advanced materials for use in various applications. Chemical aspects of the research involve the synthesis and characterization of monomers, polymers, resins, and composites. Research is performed by both scientists and engineers, working together as an interdisciplinary team. US citizenship is required for this position. Please state prominently in any correspondence that you are a US citizen.

References:

Mabry J, et al: Angewandte Chemie International Edition 47: 4137, 2008

Chhatre SS, Mabry JM, et al: ACS Applied Materials & Interfaces 2: 3544, 2010

Moore BM, Mabry JM, et al: Journal of Organometallic Chemistry 696: 2676, 2011

Guenthner AJ, Mabry, JM, et al: Macromolecules 454: 211, 2012

Keywords:

Polymer; Resin; Composite; Nanocomposite

Eligibility: Open to U.S. citizens

SF.30.03.B7524: Multifunctional Composite Structures for Space and Missile Propulsion and Power

Guenthner, A. (661) 275-8020

Higher efficiency propulsive systems represent a key need for future space and missile platforms in both civilian and military applications. In particular, the development of lighter weight structures using advanced materials has long been recognized as an important enabling technology for achieving higher efficiency. An unconventional approach to achieving weight reduction is through the use of structures that perform multiple functions, such as load bearing, protection from harsh operational environments, and energy storage, saving both space and weight. In energy conversion devices such as propulsion systems, the co-located availability of multiple forms of energy creates an especially attractive opportunity to exploit multifunctional structures. Embedded sparse networks provide a means of dedicating a portion of a structure to a second function while minimizing the negative impact on mechanical properties, whereas embedded electroactive organic materials and nanoparticle reinforcements in composite matrices provide a mechanically robust venue for combining sensing, energy storage, and structural reinforcement in a single component.

References

Guenthner AJ; Hess DM; Cash JJ: Journal of Polymer Science, Part B: Polymer Physics 48: 396, 2010

Stenger-Smith JD, Guenthner AJ, et al: Journal of the Electrochemical Society 157: A298, 2010

Keywords: Polymers; Propulsion; Multifunctional; Energy storage; Electroactive; Lightweight;

Eligibility: Open to U.S. citizens

SF.30.04.B0202: High Pressure and Supercritical Combustion

Talley, D. (661) 275-6174

The objective of this work is to investigate atomization and combustion of liquid propellants at high pressures including supercritical pressures. Current understanding of spray combustion processes is based mostly on low pressure, subcritical mechanisms, whereas future Air Force propulsion and other combustion applications will increasingly emphasize high pressures. Atomization and spray combustion mechanisms may be different in these regimes. At pressures exceeding the critical point of the propellant (731 psi for liquid oxygen), the sharp distinction between gas and liquid phases can entirely disappear, and we can question whether droplets can even exist. Such flows will likely exhibit properties, which at some times are like those of turbulent jets and at other times are more like those of sprays. Even subcritical high pressures pose substantial challenges for combustion diagnostic techniques, most of which were developed for low-pressure applications. To be overcome are obstacles such as dense sprays, beam steering, molecular quenching, and spectral line broadening. Numerous research opportunities are available to work with an established team of scientists and engineers to improve technology in this area.

Keywords: Liquid propellants; Supercritical fluids; Drops (liquids)

Eligibility: Open to U.S. citizens

SF.30.04.B0203: Plasma Physics of Electric Propulsion Devices

Holmes, Michael (661) 275-3206

The objective of this research is to investigate the operating physics of existing electric propulsion devices to predict and improve thruster performance and lifetime, as well as to develop new schemes for highly efficient plasma acceleration for spacecraft propulsion applications. Important study areas include plasma physics, pulsed power system design and coupling, Taylor cone formation, thruster energy loss mechanisms, and heat transfer. Of particular interest is improving the understanding of the turbulent plasma mechanisms that govern electron transport within partially magnetized plasmas through a combination of advanced non-intrusive diagnostics, numerical simulation, and theoretical models. Other areas of interest include efficient use of chemical propellants in electric propulsion systems and improved understanding of ground test methodologies

SF.30.04.B5781: Experimental Methods for Solid Propellant Mechanical Behavior Characterization

Miller, T. (661) 275-5323

Solid propellants are a unique class of materials that behave in a viscoelastic manner but also develop damage as an effect of aging. Methods for characterizing propellant mechanical properties have been adapted from linear elastic, small strain experimental methods, but these approaches are lacking in fidelity. We are interested in developing advanced experimental methods of determining the mechanical behavior parameters of propellants in various stress states so that the results can be used to predict the mechanical response of the propellant grain. Properties such as Prony series, Williams-Landel-Ferry (WLF) parameters, fracture parameters (J-integral and fracture toughness KIC), and damage parameters are considered important. Although the time and temperature dependent nature of these parameters is important, other environmental factors may also be investigated (for example, pressure, or humidity). Using techniques such as Digital Image Correlation or Dynamic Mechanical Analysis, we would like to develop algorithms that successfully improve the characterization of these properties and that give additional insight into the nature of solid propellant mechanical behavior under conditions experienced by solid rocket motors.

Keywords: solid rocket propellant, digital image correlation, dynamic mechanical analysis, Prony series, WLF parameters, fracture mechanics, damage mechanics

Eligibility: Open to U.S. citizens

SF.30.05.B0204: Materials Science of High Temperature Materials

Hoffman, W. (661) 275-5768

Although carbon-carbon composites are excellent high-temperature structural materials and are employed extensively in many operating systems, research is needed to extend their use into different applications and environments, as well as to greatly reduce their cost. Our composites research focuses on low-cost rapid densification techniques for carbon fiber preforms, the use of nanophase materials in novel oxidation protection systems, as well as methods to enhance the interlaminar properties of these composites. Research is also being performed in the areas of nano-reinforcement of carbon fibers, control of wettability utilizing surface geometry, supercritical fluid deposition of refractory materials, and microtube technology. These microtubes can be made in various cross-sectional and axial shapes from practically any material. To date, microtubes with an ID as small at 0.1 microns have been fabricated, although the lower limit is thought to be 5 nm. Microtubes may be made free-standing or may form tubes or channels in monolithic bodies.

Keywords: Carbon-carbon composites; High-temperature composites; Fiber composites; Microtubes; Microdevices

Eligibility: Open to U.S. citizens

SF.30.05.B7618: Computational Physics of Nonequilibrium Plasma for Space Propulsion

Koo, Justin (661) 275-5908

This research topic in applied physics and mathematics focuses on the development and application of advanced numerical methods and physical models applied to plasma dynamics for conditions relevant to various applications of interest to the Air Force, particularly electric propulsion systems. Physical regimes range from rarefied plasma to ideal MHD, weakly to fully ionized, and with temperatures up to 100 eV. We are particularly interested in multiscale methods, hybrid methods, and innovative mathematical and numerical approaches to solving plasma kinetics. Fluid (MHD) and multi-fluid models, collisional-radiative (CR) kinetics, particle-in-cell (PIC), and Monte-Carlo collisions (MCC) methods are of typical interests, as well as Vlasov/Fokker-Planck approaches and their combination.

References: Kapper MG, Cambier JL: Journal of Applied Physics 109: 113308, 2011

Kapper MG, Cambier JL: Journal of Applied Physics 109: 113309, 2011

Keywords: Plasma; Nonequilibrium; Collisional-radiative; MHD; PIC; Vlasov

Eligibility: Open to U.S. citizens

SF.30.06.B6891: Synthesis of Novel Polymer Composite Monomers and Resins

Mabry, J. (661) 275-5857

The chemical synthesis of novel molecules and reactive monomers, as well as their use in thermoplastic and thermosetting polymer nanocomposites, has resulted in significant improvements in a wide variety of polymer composite systems. Property improvements enabled by these materials have resulted in their use in several rocket propulsion and other defense-related applications. In addition to property improvement, synthesis of functional molecules and compounds at reduced cost is also desired. AFRL/RQ is a leader in the field of reinforced polymer composite research. An opportunity exists in the Air Force Research Laboratory at Edwards AFB for research in the synthesis of novel molecules, compounds, and polymer composites. A qualified candidate will have experience in organic, inorganic, organometallic, or polymer synthesis, or a combination of these areas. The Rocket Propulsion Division, Propellants Branch conducts both basic and applied research, leading to the development of advanced materials for use in rocket propulsion and other defense applications. Chemical aspects of the research involve the synthesis and characterization of new materials and polymer composites. These materials can be utilized for the modification of polymer properties, such as resistance to wetting by water and hydrocarbons, oxidation-resistance, thermal stability, and ease of processing. Aspects of this work involve the design and synthesis of monomers and polymers, as well as functional nanomaterials with novel architectures and composite resin development. Research is performed by both scientists and engineers, working together as an interdisciplinary team. US citizenship is required for this position. Please state prominently in any correspondence that you are a US citizen.

References:

Tuteja A, Choi W, et al: Science 318: 1618, 2007

Mabry JM, et al: Angewandte Chemie, International Edition 47: 4137, 2008

Mabry JM, et al: Langmuir 27, 10206, 2011

Mabry JM, et al: Journal of the American Chemical Society 133, 20084, 2011

Keywords: Synthesis; Polymer; Oleophobic; Nanocomposite; Nanomaterial; Composite; Hydrophobic

Eligibility: Open to U.S. citizens

SF.30.13.B1110: Computational Algorithm Development for Rocket Propulsion Flowfield Simulations

Sankaran, V. (661) 275-5534

Rocket propulsion flowfields offer significant challenges to computational modeling because of the complex turbulent reacting multiphase physics, the presence multiple length and time scales, and the unsteady nature of the flow phenomena. This topic concerns the investigation of numerical algorithmic aspects to address these challenges from the viewpoint of ensuring solution accuracy, robustness, efficiency and scalability. Specific areas of interest include improved flux schemes that can preserve uniform accuracy at all Mach, Reynolds, and Strouhal numbers; high-order accurate spatial and temporal discretizations; enhanced implicit solution techniques; and automated time-step control for the robust solution of stiff and highly nonlinear problems. The technical approach will involve the use of numerical analysis tools such as von Neumann stability, asymptotic theory, and the method of manufactured solutions as well the development and implementation of the algorithms in candidate computational fluid dynamics codes. Particular emphases will be placed on unsteady flow simulations with DES or LES models for turbulence, generalized equations-of-state for high-pressure super-critical problems, finite-rate chemical kinetics, and stochastic-PDF methods for turbulent combustion. Verification and validation will be targeted towards canonical spray and combustion problems, as well as practical rocket flowfield simulations involving solid motors, liquid rocket engines, cryogenic turbomachinery, and/or electric thrusters.

 

Keywords:

Computational fluid dynamics; Algorithm development; Propulsion flowfields; Liquid rocket engines; Solid rocket motors; Cryogenic turbomachinery;

*Eligibility: Citizenship: Open to U.S. citizens.

SF.30.13.B1111: Novel Meshing Paradigms for Rocket Propulsion Flowfield Simulations

Sankaran, Venke (661) 275-5534

This research focuses on the exploration of novel meshing paradigms for computational fluid dynamics simulations of internal rocket flowfields. Current meshing paradigms have both strengths and weaknesses. Cartesian meshes are efficient and accurate, but are not suitable for capturing near-wall boundary layer phenomena; curvilinear structured meshes are efficient, accurate, and suitable for boundary layers, but the grid generation is complex and tedious; unstructured meshes are much easier to generate and are well-suited to boundary layers, but they are relatively inefficient and are typically restricted to second-order accuracy at best. The technical approach is to combine different mesh types within a single flowfield simulation so that the domain is effectively mapped by the grid-types best suited to the local requirements. Thus, the off-body region can be represented by Cartesian meshes, while the near-body region is governed by body-fitted structured or unstructured meshes. Connectivity between the different mesh systems is usually accomplished using overset grid technology. We anticipate that the judicious combination of such mesh types can lead to over two orders of magnitude savings in computational time and provide significant enhancements of solution accuracy. The specific topic of interest is the development of such a multiple-mesh infrastructure for internal flowfields that are representative of rocket propulsion flowfields. Additional areas of interest include (1) automated adaptive mesh refinement technology, (2) effective domain decomposition and load balancing algorithms, and (3) improved overset interpolation and/or conservative flex-exchange methods for inter-mesh information transfer. Research and development will be conducted within an existing code infrastructure and the methods applied to rocket propulsion flowfields including solid motors, liquid engines, cryogenic turbomachinery and/or electric thrusters.

 

Keywords:

Computational fluid dynamics; Overset grids; Internal rocket flowfields; Adaptive mesh refinement;

*Eligibility: Citizenship: Open to U.S. citizens.

SF.30.13.B1112: Combustion and Ignition Chemistry of Energetic Propellants

Vaghjiani, Ghanshyam (661) 275-5657

Our research centers on fundamental chemical kinetics and applications in combustion chemistry of energetic propellants. The rates of elementary reactions are measured using various direct time-resolved techniques such as pulsed laser photolysis, coupled with laser-spectrometric or mass-spectrometric probing of the short-lived species in the gas phase. We also use rapid-scan FTIR absorption spectroscopy to probe the formation of stable products in these reactions. Heterogeneous processes, such as the reactions of aerosolized propellant fuel in various oxidizing gaseous environments, are studied using the VUV-PI-TOFMS experimental set-up of the Chemical Dynamics Beamline 9.0.2.3 at the Advanced Light Source Synchrotron Facility at the Lawrence Berkeley National Laboratory in Berkeley, CA. Direct molecular dynamics simulations are also performed to identify pertinent chemical processes in the combustion of propellant mixtures. Chemical models of these processes are constructed using ab initio quantum chemical, TST and RRKM theories to understand the mechanisms. The laboratory data is extrapolated to operational conditions in the prediction of ignition delay times, a quantity of significant importance in the design of rocket engines.

*References:

Sun H, Vaghjiani GL: J. Chem. Phys., 142, 204301 (2015).

Newsome DA, Vaghjiani GL, Sengupta D: Propellants, Explosives & Pyrotechnics, 40, 759 (2015).

Perez JPL, Yu J, Anderson SL, Sheppard AJ, Chambreau SD, Vaghjiani GL: Appl. Mat. Interfaces. 7, 9991 (2015).

*Keywords:

Combustion chemistry; Propellant ignition; Reactions kinetics; Time resolved laser spectroscopy; FTIR spectroscopy; TOF mass spectrometry; Chemical mechanisms; Quantum chemical calculations; Molecular dynamics simulations;

*Eligibility: Citizenship: Open to U.S. citizens.

AFRL/Aerospace Systems

Dr. Frank S. Gulczinski III
AFRL/RQ
2130 Eighth Street
Wright Patterson Air Force Base, Ohio 45433-7542
Telephone: (937) 938-4805
E-mail: frank.gulczinski@us.af.mil