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DIRECTED
ENERGY
PROFESSIONAL
SOCIETY
Journal of Directed Energy
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Volume 3, Number 3 |
Winter 2009 |
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The papers listed below constitute Volume 3, Number 3 of the Journal of Directed Energy.
Print copies of this, and other issues of the Journal of Directed Energy are available through the
DEPS online store.
Access complete technical paper(s) through links in the paper titles.
Capability Assessment of the High-Energy Laser Liquid Area Defense System (HELLADS)
(1,400 KB)
Ryan S. Ponack, 14 AF/A9 and J.O.Miller, Air Force Institute of Technology
High-energy Laser (HEL) technology continues to improve, and its planned place in the battlefield is ever
evolving. The Defense Advance Research Projects Agency (DARPA)-envisioned HEL Liquid Laser Area Defense
System (HELLADS) has two main advantages over any HEL predecessor. One, the configuration is small and
light enough to be carried on more tactical aircraft such as fighters. Two, the thermal management
greatly increases HEL firepower by increasing dwell time on target. To assess HELLADS operational
capabilities, the test community has been challenged with how to effectively examine the advantages and
limitations in a cost-effective manner. Where field testing is infeasible, modeling and simulation
emerges as a relatively low-cost and robust assessment tool. Specifically, this research effort focuses
on the assessment of operational capabilities for a yet-to-be-developed HEL weapon system patterned after
HELLADS. An Air Force Standard Analysis Toolkit mission-level model, the Extended Air Defense Simulation
Model (EADSIM), is used in this study along with the HEL End-to-End Operational Simulation (HELEEOS) to
model atmospheric propagation. Of particular interest is the investigation of the envisioned HELLADS
operational envelope and the potential advantages it offers over other HEL systems. Scenarios are
developed to represent the homeland defense arena in which HELLADS is envisioned to operate.
KEYWORDS: Computer simulation, High-energy laser, Liquid laser, Mission-level combat modeling
PAGES 193-211
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Diagnostic Array for Characterizing Narrow-Band High-Power Microwave Sources
(550 KB)
P.D.Coleman, Sandia National Laboratory; and C.W.Woods and G.S.Nelson, Air Force Research Laboratory
Accurate characterization of radiated antenna patterns is critical to successfully developing high-power
microwave (HPM) sources. Accurately measuring the intense fields and radiation patterns of these dynamic
sources is a difficult task. This paper details the design and operation of a 31-element, time-resolved
diagnostic array that has been used in the development of various HPM sources.
KEYWORDS: Antenna, Diagnostic, Array, HPM
PAGES 213-221
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Broad-Spectrum Optical Turbulence Assessments from Climatological Temperature, Pressure, Humidity, and Wind
(1,050 KB)
Steven T. Fiorino, Richard J. Bartell, Matthew J. Krizo, Brandon T. McClung, J. Jean Cohen, Robb M. Randall, and Salvatore J. Cusumano; Air Force Institute of Technology
The effects of optical turbulence on high-energy laser propagation have been well documented. The optical
turbulence is typically characterized using the index of refraction structure parameter, Cn2. The value
and three-dimensional variation of Cn2 can be accurately diagnosed for the surface boundary layer
(lowest 50 m of the atmosphere) from values of temperature, pressure, humidity, and wind velocity using
meteorological similarity theory. Examples of such similarity theory Cn2 calculators include the Tunick
model for overland applications and the Navy Surface Layer Optical Turbulence (NSLOT) model for ocean
scenarios. Both the Tunick and NSLOT models are limited in their applicability to relatively small
portions of the spectrum in the visible and infrared; generally they are valid from 400 to 3,000 nm and
from 7.8 to 19 microm. This study expands the valid spectral range of the Tunick Cn2 model to 400 nm-8.6 m,
continuously. This is accomplished by adapting the Tunick model for use with the Air Force Institute of
Technology Center for Directed Energy HELEEOS (High Energy Laser End-to-End Operational Simulation) and
LEEDR (Laser Environmental Effects Definition and Reference) models. The derived Cn2 values can be
wavelength tuned and compared to scintillometer and radar measurements of Cn2
KEYWORDS: Anomalous dispersion, Atmospheric effects, NSLOT model, Optical turbulence, Surface layer, Tunick model
PAGES 223-238
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Ablative Polymeric Materials for Near-Infrared High-Energy Laser Beam Diagnostics
(1,050 KB)
Christopher T. Lloyd, Robert F. Cozzens, and Collin J. Bright, Naval Research Laboratory; and D. Jason (Jake) Sames, Larry K. Myers, and Peter D. Kazunas, The Electro-Optics Center
One-micron lasers are of high interest for industrial and military applications fueled by recent developments
in fiber lasers. There exists a large gap in data collection for the ablation of polymeric materials
with near-infrared (IR) lasers. It is necessary to understand how and why chemical structural properties
such as aromaticity, heteroatomic content, and degree of cross-linking affect near-IR ablation of
polymers, as well as thermal stability and optical properties. More so, properties such as these are
useful for determining which polymers are best suited for laser beam diagnostic measurements. Polymers
such as clear Plexiglas have been used as beam diagnostic materials at 10.6 microm. in the past.
Identification of two commercial polymers was made for laser beam profiling and diagnostic purposes at
near-IR wavelengths. Differences in ablation and beam diagnostics using carbon black-loaded plastics
were observed. Several synthesized and commercial polymeric materials were irradiated with a 10-kW,
1.07- microm. fiber laser, and corresponding ablation energies were obtained. Ablation energies are
dependent on the molecular structure of polymers, especially aromatic and heteroatomic character and
thermal degradation processes. This study was aimed at understanding how near-IR radiation ablates
polymers and to evaluate different polymers for use as potential irradiance diagnostic tools (witness
plates).
KEYWORDS: Carbon black, HEL irradiation, Irradiance diagnostics, 1.07 micrometer fiber laser, Polymer ablation
PAGES 239-256
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Measurements of Improved ElectricOIL Performance, Gain, and Laser Power
(1,100 KB)
J.W.Zimmerman, G.F.Benavides, and B.S.Woodard, University of Illinois at Urbana-Champaign; D.L.Carroll, A.D.Palla, and J.T.Verdeyen, CU Aerospace; and W.C.Solomon, University of Illinois at Urbana-Champaign
Ongoing experiments have led to continued improvements in the electric oxygen-iodine laser (ElectricOIL)
system that significantly increased the performance, gain, and laser power output. Experimental
investigations utilize radio-frequency discharges in O2/He/NO mixtures in the pressure range of 30-60
torr. The goal of these investigations was maximization of both the yield and flow rate (power flux) of
O2(a1delta) in order to produce favorable conditions for subsequent gain and lasing in our ElectricOIL
system. Numerous measurements of O2(a1?), oxygen atoms and discharge excited states are made to
characterize the discharge. A gain of 0.22% cm-1 was measured with a corresponding outcoupled power of
28 W. Modeling with the BLAZE-IV code is in good agreement with data and helps to guide our
understanding of the complex hybrid laser system.
KEYWORDS: ElectricOIL, Oxygen-iodine laser, Singlet oxygen
PAGES 257-275
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Finite Element Analysis and Dynamic Simulation of Target Thermal Response to High-Energy Lasing
(700 KB)
Christopher Larson, Clay Canning, Gunnar Tamm, and John Hartke, United States Military Academy
High-energy laser (HEL) systems on the order of 100 kW are under development to neutralize stationary and
mobile targets. Modeling the thermal response of the target will identify both requirements for the
laser system and means to protect the target against such laser systems. Analytical solutions are
limited, and computational solutions are accurate only if they consider boundary conditions and material
properties varying with time, temperature, and location. A transient three-dimensional finite element
solution has been developed that employs dynamic simulation techniques. Stationary and mobile targets
are evaluated under loading by a continuous-wave laser with various beam profiles, with particular
attention to mortar rounds in flight. Results from the target thermal model support complementary
analyses of the 100-kW HEL system completed at the U.S. Military Academy.
KEYWORDS: Finite element, Heat transfer, High-energy laser
PAGES 276-288
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Volume 3, Number 3, Journal of Directed Energy
Last updated: 6 September 2017
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