The Air Force Institute of Technology is a graduate school and provider of professional and continuing education for the United States Armed Forces and is part of the United States Air Force. It is located in Ohio at Wright-Patterson Air Force Base, near Dayton. Wikipedia.
Jackson J.A.,Air Force Institute of Technology
IEEE Transactions on Antennas and Propagation | Year: 2012
We derive an analytic scattering model for 3D bistatic scattering from a dihedral using geometrical optics (GO) and physical optics (PO). We use GO to trace ray reflections, and we evaluate the PO integral(s) for the field scattered by each plate of the dihedral. Multiple cases of reflection geometry are considered to account for effects of the dihedral plate size and antenna aspect angles. The complex-valued (amplitude and phase) scattering response is derived. The resulting parametric scattering model is presented in terms of the vertical and horizontal co-polarization and cross-polarization responses that correspond to the outputs of industry-standard numerical prediction codes. Comparing the derived model to available codes for method of moments (MoM), shooting and bouncing rays (SBR), and parametric models (PM), we demonstrate that the derived solution achieves the same accuracy as SBR, approximates MoM, is more accurate than PM, and does so in fast computation time comparable to a PM. © 2006 IEEE.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase II | Award Amount: 749.96K | Year: 2014
ABSTRACT: Given the results obtained in the Phase I effort, we are now in a position to advance to the next generation of High Power Phased Array Transceiver Systems. The new approach proposed here is to use enough elements in the phased array to ensure that significant wavefront compensation performance can be obtained with only piston commands. A system of this nature can be developed in two ways, using advanced target-based phasing technology, or by using conventional wavefront sensing technology to determine the relative piston commands in an array of fiber lasers. Both approaches result in system simplicity while eliminating the legacy difficulties associated with a single high power laser and high power deformable mirrors. Both of these new concepts will be evaluated in detail and compared with conventional AO transmitter systems, resulting in one or two conceptual designs that show promise. To ensure practical realizability, both the optical and electronic subsystem detailed designs, as well as the conceptual design for a well instrumented field testbed, will be developed. AFIT will provide analytical and laboratory testing of concepts of interest. Building and field-testing a full-up system will be reserved for Phase II enhancements or Phase III activities. BENEFIT: The proposed effort will develop validated conceptual designs that will serve as the next generation of light-weight laser weapons technology. The methodology for testing these and other concepts will also be developed and applied at our university partner (AFIT) facility.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 149.99K | Year: 2013
ABSTRACT: The proposed research will develop a method of compensating atmospheric disturbances in the transmitting subapertures of a phased array transceiver operating in the infrared. The aero-optical boundary layer and atmospheric turbulence create phase variations within each subaperture. To compensate these variations, an adaptive optical system will be used in each subaperture. The proposed wavefront sensor is a self-referencing interferometer, and the corrective element is a liquid crystal adaptive optic or other device suitable for use in phased arrays. The beacon for the wavefront sensor is the coherent high energy spot reflected from the target of the phased array. The main innovation in the proposed research consists of techniques to mitigate the corruption in the beacon phase caused by speckle, and other related difficulties associated with using the reflected spot as a beacon. The speckle phase that the phasing system estimates will be used to compensate the speckle phase in the adaptive optics system. BENEFIT: The primary product of this research will be the conceptual design of an adaptive optical (AO) system suited for use in phased array transceivers. This system will be available in future phased array design work to improve the performance of phased arrays as needed. The adaptive optical system will not depend on a particular phased array architecture, but will be available for use with a wide variety of architectures. The primary capability of the AO system will be in correcting the aero-optical boundary layer for airborne phased arrays. The use of the AO system also allows for more efficient configurations of the beam phasing system.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase II | Award Amount: 874.42K | Year: 2014
Proper design of Diode-Pumped Alkali Laser Systems (DPALS) is challenging because many interrelated processes impact their performance and critical kinetic rate coefficients are not well known. In response, our team is developing a comprehensive physics-based analysis/design tool, and experimentally determining key kinetic rate coefficients. The resulting product will be a user-friendly, high-fidelity, coupled Fluid-Thermal-Mechanical-Optical software package with accurate rate constants. During Phase I, we developed initial versions of the analysis tools, performed experiments to determine key rate constants, and performed parametric sensitivity analyses. In Phase II, we will develop a user-friendly, fully coupled, software package with a comprehensive set of experimentally determined rate constants. Approved for Public Release 14-MDA-7739 (18 March 14).
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase I | Award Amount: 124.95K | Year: 2014
The key innovation in this project is the implementation of an Imaging Fourier Transform Spectrometer (IFTS) for in situ metal additive manufacturing process monitoring. In this Phase I STTR project, Mound Laser & Photonics Center, a developer of laser based additive manufacturing processing, will collaborate with the Air Force Institute of Technology, with expertise and innovative hardware for spectroscopy, to implement the IFTS in a Selective Laser Melting (SLM) R&D test bed to demonstrate advanced strategies for process control and in situ quality assurance such as: (1) automatic detection of the molten area in various layers, (2) in situ release of stresses induced by temperature gradients, and (3) real-time control of alloy composition and minimization of contaminants. These capabilities with facilitate the manufacture of parts with complex geometries with improved microstructures and properties. In Phase I we intend to: (1) prove the utility of the IFTS for monitoring SLM processing of metals and alloys, (2) determine surface temperatures with a statistical accuracy of better than 4 oC, systematic accuracy of better than 10 oC and a dynamic range of up to 2000 oC, and provide rapid (1 kHz), automatic identification of the molten area, (3) track changes in chemical composition due to evaporation, oxidation, and melt expulsion, (4) reduce data dimensionality and correlate these IFTS sensor features with manufacture quality metrics, and (5) design the concept for a Phase II prototype sensor suite that focuses on key aspects of the IFTS datascape to inexpensively emulate the IFTS. In Phase II, a prototype optical sensor will be developed for process control of metallic additive manufacture of lightweight, reliable, low cost structures.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase II | Award Amount: 748.82K | Year: 2012
ABSTRACT: The proposal outlines work and time tables associated with finalizing the development of wear model concepts developed in Phase I work to predict the wear of two materials sliding with respect to each other while being subjected to high velocities and/or high pressures. In parallel with this, a severe wear bench test fixture design will be finalized, built, and utilized to validate the severe wear model, which will be further developed to a state where it can be easily utilized to predict wear for a range of materials and material systems. The final result will represent a significant expansion of the capability to model, validate, and utilize technology to select material for severe wear applications. BENEFIT: Severe wear applications exist in a range of components within various mechanical systems utilized in commercial devices. A few examples of these from the many existing are valve seats and valve faces in internal combustion engines, railroad wheels and track surfaces, and sliding surfaces in various lawn and cutting devices. Presently the selection and application of materials for severe wear applications is based on experience (which may not result in the use of an optimum material system) and/or trial and error. Both methods result in significant cost. An effective severe wear model and validating bench test fixture would result in substantial cost savings in the development of such products.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase II | Award Amount: 749.99K | Year: 2012
ABSTRACT: Building on Phase I research that demonstrated the feasibility of target-based phasing for phased array beam control, the proposed Phase II research consists of analysis and a laboratory experiment. The four key topics of the research are phasing at the target, correcting stair mode (also known as array tilt), imaging the target with high resolution, and correcting beam overlap errors on the target. The Phase II experiment is designed to address these four issues in the laboratory, validating the research performed in Phase I and Phase II. The phasing approach, combined with a technique for array tilt correction, can correct all beam piston errors at the target. Moreover, the phase calculations also estimate the speckle field due to reflection of the high energy lasers off the target, allowing for high-resolution speckle imaging of the target in the area of the aim point. The research will also determine if the phasing measurements contain information about beam overlap errors on the target that can be used to correct such errors. This effort is performed in conjunction with AFIT, and will enhance their work in the area and provide partial support to at least one Ph.D. candidate. BENEFIT: The anticipated benefit from this research is the experimental validation of beam control techniques for phased array transceivers. The technology developed in this research will allow phased arrays to achieve their primary design goal of phasing an array of laser beams at a target. As such, the technology is critical in the development of phased arrays. The primary commercial application of this technology will be in high energy laser (HEL) phased array weapons, in which it will be a central component. The technology also produces image data that are useful in HEL beam control as well as active imaging applications. A secondary commercial application exists in active imaging.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase I | Award Amount: 99.97K | Year: 2013
Diode-Pumped Alkali Laser Systems (DPALS) have great potential for missile defense and other applications. Proper design of these systems is challenging because many interrelated processes impact their performance and critical kinetic rate coefficients are not well known. In response, our team proposes to develop a comprehensive physics-based analysis/design tool, and determine key kinetic rate coefficients experimentally. The resulting product will be a user-friendly, high-fidelity, coupled Fluid-Thermal-Mechanical-Optical software package with accurate rate constants. MDA representatives and others will use this software to design laser systems, predict performance, conduct sensitivity analyses, and assess experimental results. This achievement will help advance high energy laser (HEL) systems for a variety of applications. Our team is well-suited to succeed because we have extensive experience with laser systems, atomic and laser kinetic experiments, and customized numerical analyses. During Phase I, we will develop critical analysis tools, determine key rate constants, and perform parametric sensitivity analyses. We will then develop a user-friendly, fully coupled, software package with a comprehensive set of experimentally-determined rate constants during Phase II.
Agency: NSF | Branch: Interagency Agreement | Program: | Phase: | Award Amount: 1.30M | Year: 2012
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 149.77K | Year: 2015
ABSTRACT: The next-generation Global Positioning System (GPS) in congested and contested environments is expected to exploit Spectrum Holes (SH) in order to provide uninterrupted Position Navigation and Timing (PNT) service worldwide. Innoflight has teamed with the Air Force Institute of Technologys (AFITs) Autonomy and Navigation Technology (ANT) Center to develop a system based on cognitive radio (CR) that uses spectrum monitoring stations to instrument L- through C-Bands for temporal and spatial SH. Once the desired frequencies of operation are identified, they are passed to the operational tasking function in order to provide the appropriate plan for the GPS space and user equipment segments. Future generations of spectrum monitoring receivers incorporated into Military GPS User Equipment (MGUE) will be able to form a spectrum monitoring ad hoc network in deployed operations.; BENEFIT: Military applications include advanced GPS systems and operations, communication systems and electronic warfare systems. Civilian applications include PNT systems and communication systems.