Thesis (Ph. D.)--Catholic University of America, 2001. / Includes bibliographical references (leaves 271-291).

Approved for public release; distribution is unlimited / The objective of this thesis is to investigate the requirements and limitations of boost phase ballistic missile intercept systems that contain an interceptor and its guidance sensors (both radar and infrared). A three- dimensional computer model is developed for a multi-stage target with a boost phase acceleration profile that depends on total mass, propellant mass and the specific impulse in the gravity field. The radar cross-section and infrared radiation of the target structure is estimated as a function of the flight profile. The interceptor is a multi- stage missile that uses fused target location data provided by two ground-based radar sensors and two low earth orbit infrared sensors. Interceptor requirements and limitations are derived as a function of its initial position from the target launch point and the launch delay. Sensor requirements are also examined as a function of the signal-to- noise ratio during the target flight. Electronic attack considerations within the boost phase are also addressed including the use of decoys and noise jamming techniques. The significance of this investigation is that the system components within a complex boost phase intercept scenario can be quantified and requirements for the sensors can be numerically derived. / Captain, Turkish Air Force

The Free Electron Laser (FEL) can provide the naval surface combatant with a directed energy weapon that can be used against a large target set. Due to space constraints in a shipboard installation, an exploration is conducted to show the feasibility of short Rayleigh length FELs using a FEL simulation. Low atmosphere engagements are discussed through the modeling of a turbulence module for laser propagation in cruise missile defense applications. In particular, this thesis explores the difficulties in engaging a short/medium range theater ballistic missile (TBM) in the terminal phase as an engagement scenario in support of littoral operations using HELCoMES, developed by SAIC, as an engagement analysis tool. A concept of operations (CONOPS) for the use of a FEL as an area TBM defensive weapon is explored, using a unitary, high explosive warhead model and extrapolations to other TBM warhead types.

We describe major enhancements to the missile defense planning aid "JOINT DEFENDER" (JDEF). JDEF is the first system that shows how to evaluate and exploit new and anticipated improvements in interceptors, long-range surveillance and tracking capabilities, networked communications, and the ability of detecting platforms to cue intercepting ones downrange. We want to improve system-wide effectiveness, gauged here by the reduction of expected damage inflicted. We defend an asset list (DAL) of targets, characterized by their locations and values to us. Our defenders include pure "LOOKERs," radars and sensors of enemy missile launches, and "SHOOTERs," platforms with means to both detect and intercept enemy launches. JDEF optimally positions platforms that can be moved, and prescribes what each platform should do. JDEF can estimate the value to either opponent of secrecy, deception, or intelligence. JDEF is the only missile defense planning system using formal optimization. Among many advantages this conveys, JDEF is able to unambiguously quantify the difference among disparate plans. Although the JDEF planner can manually control any detail, the planner is well advised to let optimization suggest where to start.

A near-optimal guidance law has been developed using the direct method of calculus of variations that maximizes the kinetic energy transfer from a surface-launched missile upon interception to a ballistic missile target during the boost phase of flight. Mathematical models of a North Korean Taep'o-dong II (TD-2) medium-range ballistic missile and a Raytheon Standard Missile 6 (SM-6) interceptor are used to demonstrate the guidance lawâ s performance. This law will utilize the SM-6â s onboard computer and active radar sensors to independently predict an intercept point, solve the two-point boundary value problem, and determine a near-optimal flight path to that point. Determining a truly optimal flight path would require significant computing power and time, while a near-optimal flight path can be calculated onboard the interceptor and updated in real time without significant changes to the interceptorâ s hardware. That near-optimal guidance path is then converted into a set of command functions and fed back into the control computer of the interceptor. By modifying the second and third derivatives of the two-point boundary value problem, the intercept conditions can be varied to study their effects upon the optimal flight path regarding the maximization of kinetic energy upon impact. / US Navy (USN) author.

Approved for public release; distribution is unlimited / The NATO Allies decided at the November 2002 Prague Summit to conduct a feasibility study concerning the protection of national territories, populations, and forces from the threat of ballistic missile attacks. This thesis examines current missile defense programs and analyzes their potential to protect the Alliance as a whole, thus maintaining the indivisibility of Allied security. The thesis investigates the political, military, economic, and technological challenges for a NATO full-spectrum missile defense and the major questions that the Allies have yet to resolve. It also examines the prospects for cooperation between NATO and Russia in missile defense and potential perils for international stability, including the non-proliferation regime. The thesis concludes that NATO missile defenses will probably enhance the transatlantic link. However, the most crucial challenges include the command and control issue and the potential reactions of Russia and China to defenses capable of protecting NATO homelands against ballistic missile attacks. / Hellenic Army author.

Based on the underlying structure of fabric materials, a three-scale model is constructed to describe the mechanical behavior of fabric materials. The current model assumes that fabric materials take on an overall behavior of anisotropic membranes, so membrane scale is taken as the macroscopic or continuum scale of the model. Following the membrane scale, yarn scale is introduced, in which yarns and their weaving structure are accounted for explicitly and the yarns are modeled as extensible elasticae. A unit cell consisting of two overlapping yarns is used to formulate the weaving patterns of yarns, which governs the constitutive nonlinear behavior of fabric materials. The third scale, named fibril scale, zooms to the fibrils inside a yarn and incorporates its material properties. Via a coupling process between these three scales, the overall behavior and performance of the complex fabric products become predictable by knowing the material properties of a single fibril and the weaving structure of the fabrics. In addition, potential damage during deformation is also captured in the current model through tracking the deformation of yarns in fibril scale. Based on the multi-scale model, both static and dynamic simulations were implemented. Comparison between the static simulations and experiment demonstrates the model abilities as desired. Through the dynamic simulations, parameter research was conducted and indicates the ballistic performance and mechanical behavior of the fabric materials are determined by a combination of various factors and conditions rather than the material properties alone. Factors such as boundary conditions, material orientation and projectile shapes etc. affect the damage patterns and energy absorption of the fabric. / Mechanical Engieering

Multiwalled carbon nanotubes (MWNTs) are shown to be ballistic conductors at room temperature, with mean free paths of the order of tens of microns. The electrical transport measurements are performed both in air and in high vacuum in the transmission electron microscope on nanotubes pointing out of a nanotube-containing fiber that contact with a liquid metal. These measurements demonstrate that metallic MWNTs are one dimensional conductor that have quantized conductance nearly 1G0 (~{!V~}(12.9 K~{ and 8~})-1). The intrinsic resistance per unit length is found to be smaller than 100 ~{ and 8~}/~{ and L~}m, indicating a mean free path l> 65 ~{ and L~}m. The nanotube-metal contact resistances are in the range from 0.1 to 1 k~{ and 8 and L~}m. Contact scattering can explain why the measured conductances are about half of the expected theoretical value of 2G0. Current-to-voltage characteristic are in accord with the electronic structure. The nanotubes can survive high current (up to 1 mA, i.e., current density on the order of 109 A/cm2). In situ electron microscopy shows that a relative large fraction of the nanotubes do not conduct (even at high bias), consistent with the existence of semiconducting nanotubes. Discrepancies with other measurements are most likely due to damage caused to the outer layer(s) of the nanotubes during processing. The measured mean free path of clean, undamaged arc-produced MWNTs is several orders of magnitude greater than that for metals, making this perhaps the most significant property of carbon nanotubes.

The ballistic impact of Twaron CT709® plain weave fabrics is studied using an explicit finite element method. Many existing approximations pertaining to woven fabrics cannot adequately represent strain rate-dependent behavior exhibited by the Twaron fabrics. One-dimensional models based on linear viscoelasticity can account for rate dependency but are limited by the simplifying assumptions on the fabric architecture and stress state. In the current study, a three-dimensional fabric model is developed by treating each individual yarn as a continuum. The yarn behavior is phenomenologically described using a three-dimensional linear viscoelastic constitutive relation. A user subroutine VUMAT for ABAQUS/Explicit® is developed to incorporate the constitutive behavior. By using the newly developed viscoelasticity model, a parametric study is carried out to analyze the effects of various parameters on the impact behavior of the Twaron fabrics, which include projectile shape and mass, gripping conditions, inter-yarn friction, and the number of fabric layers. The study leads to the determination of the optimal number of fabric layers and the optimized level of inter-yarn friction that are needed to achieve the maximum energy absorption at specified impact speeds. The present study successfully utilizes the combination of 3D weave architecture and the strain rate dependent material behavior. Majority of the existing work is based either on geometry simplification or assumption of elastic material behavior. Another significant advantage with the present approach is that the mechanical constitutive relation, coded in FORTRAN®, is universal in application. The desired material behavior can be obtained by just varying the material constants in the code. This allows for the extension of this work to any fabric material which exhibits a strain-rate dependent behavior in addition to Twaron®. The results pertaining to optimal number of fabric layers and inter-yarn friction levels can aid in the manufacturing of fabric with regard to the desired level of lubrication/additives to improve the fabric performance under impact.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 225 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 210-225).