(DE89-014272; LA-UR-89-2205; CONF-890711-1) Avail: NTIS HC A03/MF A01 The KrF laser was proposed for inertial confinement fusion (ICF) since its discovery in 1975. Since that time, the laser has seen significant development and was increased in energy many orders of magnitude to the several kilojoule energy level. The suitability of the KrF laser as a driver for ICF energy applications was continually reviewed. The latest assessments indicate that the KrF laser still appears to be the leading laser candidate. A worldwide effort exists to advance the KrF laser for ICF applications. N89-28008# Study. DOE Tokyo Univ., Tanashi (Japan). Inst. for Nuclear LASERTRON: A PULSED RF-SOURCE USING LASER Masakazu Yoshioka Dec. 1988 30 p (DE89-778130; INS-726) Avail: NTIS (US Sales Only) HC A03/MF A01 A new pulsed RF-source, Lasertron, are being developed as a possible RF power source for future electron-positron linear colliders. In a series of systematic study, a prototype lasertron has been fabricated and tested. A peak power of 80 kW is attained at 2.856 GHz RF-frequency in 1-ms time duration. The experimental results of the lasertron are described including the developments of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron. N89-28009# Lawrence Livermore National Lab., CA. PULSED LASER PROPULSION FOR LOW COST, HIGH VOLUME LAUNCH TO ORBIT DOE Jordin Kare 2 Jun. 1989 11 p Presented at the International Astronautics Federation Conference on Space Power, Cleveland, OH, 5 Jun. 1989 (Contract W-7405-eng-48) (DE89-014049; UCRL-101139; CONF-8906169-1) Avail: NTIS HC A03/MF A01 Pulsed laser propulsion offers the prospect of delivering high thrust at high specific impulse (500 to 1000 seconds) from a very simple thruster, using the energy of a remote ground-based laser to heat an inert propellant. Current analyses indicate that payloads of approximately 1 kg per megawatt of average laser power can be launched at a rate of one payload every 15 minutes and a marginal cost of $20 to $200 per kg. A 20 MW entry-level launch system could be built using current technology at a cost of $500 million or less; it would be capable of placing 600 tons per year into LEO. The SDIO Laser Propulsion Program has been developing the technology for such a launch system since 1987. The program has conducted theoretical and experimental research on a particular class of laser-driven thruster, the planar double-pulse LSD-wave thruster, which could be used for a near-term launcher. The double-pulse thruster offers several advantages, including extreme simplicity, design flexibility, and the ability to guide a vehicle remotely by precise control of the laser beam. Small-scale experiments have demonstrated the operation of this thruster at a specific impulse of 600 seconds and 10 percent efficiency; larger experiments now under way are expected to increase this to at least 20 percent efficiency. N89-28010# Ortel Corp., Alhambra, CA. BAND STRUCTURE ENGINEERING FOR ULTRA-LOW (AD-A208629) Avail: NTIS HC A03/MF A01 CSCL 09/3 DOE While semiconductor lasers of a high level of sophistication and reliability have been developed for present day fiberoptic telecommunications, demands for ultralow lasing threshold and ultrahigh modulation speed stem mainly from applications involving relatively short distance interconnections within a computer. The need for optics in computers arises from the increasing parallelism in modern computer architectures, which places heavy demands on input/output functions at gigahertz clock rates. Further consideration of using semiconductor lasers in computer optical interconnects shows that conventional semiconductor lasers are unacceptable for such purposes, the main problem being that they must be biased at or above lasing threshold for proper modulation behavior. This mode of operation requires a monitor photodiode and an active feedback circuit to stabilize the operating point. In a supercomputer where there are as many as a few hundred thousand interconnections, such feedback circuits will occupy a large amount of real estate and the bias current required will consume an unacceptable amount of power. GRA 21 Feb. 1989 138 p (AD-A209802; DIA-DST-2700Z-007-89; Rept-93) Avail: NTIS HC A07/MF A01 CSCL 09/3 This is the Soviet Laser Bibliography for January and February 1988, and is No. 93 in a continuing series on Soviet Laser developments. The coverage includes basic research on solid state, liquid, gas, and chemical lasers; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications systems; beam propagation; adaptive optics; computer technology; holography; laser induced chemical reactions; measurement of laser parameters; laser measurement applications; laser excited optical effects; laser spectroscopy; beam target interaction; and plasma generation and diagnostics. GRA N89-28012# Ortel Corp., Alhambra, CA. PIGTAILED SINGLE-MODE DIODE LASERS Final Report, 20 Sep. 1988 - 30 Apr. 1989 Norman Kwong 30 Apr. 1989 33 p (Contract N00014-88-C-2033) (AD-A209913) Avail: NTIS HC A03/MF A01 CSCL 09/3 In choosing a scheme for single mode fiber coupling, the final evaluation should of course be based on an experimental comparison between the alternative. However, such an evaluation will generally not reveal the essential limitations of any scheme. While the possible sources of less than ideal performance are well known, their relative significance is not so obvious. It is clear that in order to make significant improvements in the state of fiber coupling technology, the relevant limitations must be clarified in order to guide further efforts in fruitful directions. As such, an analysis was conducted for several aspects of the fiber coupling problem which is presented. Preliminary to the consideration of any particular system, the importance of the zeroth and first order properties of the coupling system are briefly discussed. To go beyond this, the higher order aberrations of the optical coupling system must be included in the analysis. To do this, an algorithm to calculate the mode coupling performance of any optical system NEW, EFFICIENT OPTICALLY PUMPED SOLID STATE This effort explored the effects on laser operation of ion-ion interactions in crystalline solids. The work on the doubly-doubly Nd,Er:YAG and Nd,Ho:YAG lasers has demonstrated not only simultaneous lasing of both ionic species but also drastic lifetime productions in the lower laser states of both Er and Ho. This work has enabled the prediction of crystals in which 4 level operations at 2.9 microns can be achieved and initial verification was obtained with Er,Nd:YALO. GRA N89-28014# Naval Civil Engineering Lab., Port Hueneme, CA. DEVELOPMENT OF A LIGHTWEIGHT, HIGH STRENGTH, COLLAPSIBLE HOSE Final Technical Report, Oct. 1984 - Jun. 1988 Laurence Nixon Feb. 1989 148 p (AD-A207292; NCEL-TN-1793) Avail: NTIS HC A07/MF A01 CSCL 13/11 An exploratory development effort to produce a 6-inch diameter, lightweight, high strength, collapsible, layflat hose using aramid yarn as the hose reinforcing material is reported. The design goals were to produce a hose with a 100,000-pound tensile strength and 1,800-psi burst pressure. The project had three phases: (1) a feasibility study, (2) manufacturing trials with a 4-inch hose, and (3) the design and fabrication of 6-inch hose on the production line. The work failed to produce the desired hose primarily because of strength losses incurred in the aramid during the manufacturing process. However, the project did produce a relatively high performance polyester reinforced hose (47,000-pound tensile strength) that may have applications for fuel transfer. GRA N89-28016*# Catholic Univ. of America, Washington, DC. Dept. of Electrical Engineering. JOINT-SPACE ADAPTIVE CONTROL OF A 6 DOF Charles C. Nguyen and Zhen-Lei Zhou Aug. 1989 16 p (NASA-CR-185861; NAS 1.26:185861) Avail: NTIS HC A03/MF A01 CSCL 131 The development is presented for a joint-space adaptive scheme that controls the joint position of a six-degree-of-freedom (DOF) robot end-effector performing fine and precise motion within a very limited workspace. The end-effector was built to study autonomous assembly of NASA hardware in space. The design of the adaptive controller is based on the concept of model reference adaptive control (MRAC) and Lyapunov direct method. In the development, it is assumed that the end-effector performs slowly varying motion. Computer simulation is performed to investigate the performance of the developed control scheme on position control of the end-effector. Simulation results manifest that the adaptive control scheme provides excellent tracking of several test paths. Author N89-28017*# Catholic Univ. of America, Washington, DC. Dept. of Electrical Engineering. DESIGN OF AN ADAPTIVE CONTROLLER FOR A (NASA-CR-185863; NAS 1.26:185863) Avail: NTIS HC The design of a joint-space adaptive control scheme is presented for controlling the slave arm motion of a dual-arm telerobot system developed at Goddard Space Flight Center (GSFC) to study telerobotic operations in space. Each slave arm of the dual-arm system is a kinematically redundant manipulator with 7 degrees of freedom (DOF). Using the concept of model reference adaptive control (MRAC) and Lyapunov direct method, an adatation algorithm is derived which adjusts the PD controller gains of the control scheme. The development of the adaptive control scheme assumes that the slave arm motion is non-compliant and slowly-varying. The implementation of the derived control scheme does not need the computation of the manipulator dynamics, which makes the control scheme sufficiently fast for real-time applications. Computer simulation study performed for the 7-DOF slave arm shows that the developed control scheme can efficiently adapt to sudden change in payloads while tracking various test trajectories such as ramp or sinusoids with negligible position errors. Author N89-28019# Stanford Univ., CA. Dept. of Computer Science. ROBOT MOTION PLANNING: A DISTRIBUTED Jerome Barraquand and Jean-Claude Latombe May 1989 (Contracts DAAA21-89-C-0002; N00014-88-K-0620) (AD-A209890; SU-STAN-CS-89-1257) Avail: NTIS HC A04/MF A01 CSCL 12/9 In this paper, we propose a new approach for planning the motion of robotic systems among obstacles, which is based on a distributed representation of the world model. Within this approach, we designed and implemented a general purpose path planner with five new capabilities: (1) It is able to generate very complex motions for robots with many degrees of freedom. In particular, we succeeded in generating complex paths for a 10 DOF non-serial manipulator arm made with both revolute and prismatic joints. (2) It is drastically faster (between 1 and 2 orders of magnitude) than existing systems on a sequential computer. We generated complex paths for a 3 DOF bar in a 2D workspace in about 1 second on a MIPS-based workstations, as opposed to minutes or even tens of minutes for other algorithms. The planner outputs a path for the robot in configuration space, while the goal is specified in operational space. Hence, the inverse kinematic problem is completely avoided. Furthermore, any kind of redundancy of the robot arms can be handled without modification. GRA (Contract N00014-82-K-0520) (AD-A209941) Avail: NTIS HC A04/MF A01 CSCL 11/8 The objective of the proposed research was to create hard layers on metallic surfaces in boundary-lubricated sliding and to investigate their tribological behavior. In addition, the goal was to investigate the basic mechanism of friction of lubricated metallic surfaces. We have investigated the following aspects: (1) experimental investigation of the tribological behavior of metallic and coated surfaces in boundary lubrication, and (2) finite element analysis of friction and wear of the coated surfaces, and the delamination process at the interface. GRA N89-28021# Cornell Univ., Ithaca, NY. Dept. of Computer Science. GENERIC SINGULARITIES OF ROBOT MANIPULATORS Dinesh K. Pai and M. C. Leu 1988 7 p Prepared in cooperation with New Jersey Inst. of Technology (Contracts N00014-88-K-0591; N00014-86-K-0281; NSF MSM-84-51074; NSF DMS-86-17355) (AD-A210116) Avail: NTIS HC A02/MF A01 CSCL 12/9 The singularities of the differential kinematic map, i.e., of the manipulator Jacobian, are considered. We first examine the notion of a generic kinematic map, whose singularities form smooth manifolds of prescribed dimension in the joint space of the manipulator. For 3-joint robots, an equivalent condition for genericity using determinants is derived. The condition lends itself to symbolic computation and is sufficient for the study of decoupled manipulators, i.e., manipulators which can be separated into a 3-joint translating part and a 3-joint orienting part. The results are illustrated by analyzing the singularities of two classes of 3-joint positioning robots. GRA 38 QUALITY ASSURANCE AND RELIABILITY Includes product sampling procedures and techniques; and quality control. N89-28022# University of Southern California, Los Angeles. Dept. of Electrical Engineering. BASIC RESEARCH IN RELIABILITY FOR REAL SYSTEMS (Grant AF-AFOSR-0269-84; AF Proj. 2304) (AD-A209649; AFOSR-89-0783TR) Avail: NTIS HC A02/MF A01 CSCL 12/7 The goal of this research is to develop practical models and efficient algorithms to analyze the reliability, availability and maintainability of complex systems in which component failures are statistically dependent and each component is subject to degradations before complete failure. The Event-Based Reliability Model (EBRM) was developed to model and analyze the reliability of a network in which component failures are statistically dependent. In EBRM, the events that could cause component failures were modeled explicitly. This approach required much fewer parameters than the traditional model employing conditional probabilities. The EBRM was also proved to be a completely general model which could be applied to various types of failure dependencies. For reliability evaluations, many existing algorithms for computing network reliability could be used with minor modifications and no significant increase in computational complexity. An improved algorithm for the approximate evaluation of network performance was also developed. For multi-state systems, ordered enumeration was used to approximate and bound system reliabilities and other performance measures, and an efficient algorithm was developed for this purpose. The author has been studying network management algorithms which are GRA resilient to network failures. N89-28023# Illinois Univ., Chicago. Dept. of Mathematics Statistics and Computer Science. DESIGN OF EXPERIMENTS AND RELIABILITY MODELS Final Report, 1 Aug. 1985 - 31 Oct. 1988 51 P A. S. Hedayat and E. El-Neweihi 1 May 1989 The research in design of experiments included the following areas: (1) efficient designs for experiments involving several factors; (2) efficient designs for repeated measurements models; (3) trade off in designs; (4) flexible orthogonal arrays; (5) efficient designs for comparing test treatments with controls; and (6) designs for collecting data through sampling. The research in reliability was mainly directed to the following areas: multistate reliability models; optimal assembly of coherent systems (both in the binary and multistate cases); redundancy importance and allocation of spares in coherent systems; closure properties of classes of life GRA distributions; and optimal inspection policies. N89-28028# Naval Research Lab., Washington, DC. Condensed THE INADEQUACIES OF DAMAGE ENERGY AS A MEASURE (AD-A207376; NRL-MR-6443) Avail: NTIS HC A03/MF A01 CSCL 07/4 The Lindhard, Nielson, Scharff and Thompson equations for the partitioning of an ion's energy into electronic and damage portions are widely used to estimate the number of displacements produced in a solid by an impinging ion. The LNST approach was extended by including a displacement energy at all stages of the calculation, which allows the formation an integral equation that yields the number of displacements Nv(E) directly, rather than estimating it from the damage energy D(E). The results are compared with both the LNST approach and with the collision simulation code MARLOWE. The approach is found to approximate the MARLOWE results reasonably well, but the the damage energy is a poor estimator of displacement damage, because Nv(E) and D(E) have different dependencies on the interatomic potential and on the low energy portion of the inelastic loss function. GRA N89-28029*# National Aeronautics and Space Administration. Lewis Research Center, Cleveland, OH. A DATA ACQUISITION AND CONTROL PROGRAM FOR A computer program was developed for data acquisition and control of axial-torsional fatigue experiments. The multitasked, interrupt-driven program was written in Pascal and Assembly. This program is capable of dual-channel control and six-channel data acquisition. It can be utilized to perform inphase and out-of-phase axial-torsional isothermal fatigue or deformation experiments. The program was successfully used to conduct inphase axial-torsional fatigue experiments on 304 stainless steel at room temperature and on Hastelloy X at 800 C. The details of the software and some of the results generated to date are presented. Author N89-28030*# National Aeronautics and Space Administration. Lewis Research Center, Cleveland, OH. PROBABILISTIC STRUCTURAL ANALYSIS METHODS OF HOT ENGINE STRUCTURES C. C. Chamis and D. A. Hopkins Jun. 1989 17 p Presented at the 34th International Gas Turbine and Aeroengine Congress and Exposition, Toronto, Ontario, 4-8 Jun. 1989; sponsored in part by ASME (NASA-TM-102091; E-4855; NAS 1.15:102091) Avail: NTIS HC A03/MF A01 CSCL 20K Development of probabilistic structural analysis methods for hot engine structures at Lewis Research Center is presented. Three elements of the research program are: (1) composite load spectra methodology; (2) probabilistic structural analysis methodology; and (3) probabilistic structural analysis application. Recent progress includes: (1) quantification of the effects of uncertainties for several variables on high pressure fuel turbopump (HPFT) turbine blade temperature, pressure, and torque of the space shuttle main engine (SSME); (2) the evaluation of the cumulative distribution function for various structural response variables based on assumed uncertainties in primitive structural variables; and (3) evaluation of the failure probability. Collectively, the results demonstrate that the structural durability of hot engine structural components can be effectively evaluated in a formal probabilistic/reliability framework. N89-28031# Oak Ridge National Lab., TN. Author THE SIGMAJIG: AN IMPROVED HOT-CRACKING TEST (Contract DE-AC05-84OR-21400) (DE89-013029; CONF-8906135-1) Avail: NTIS HC A02/MF A01 A comprehensive stress analysis was performed for a bimaterial plate subjected to a uniform change of temperature. The steel and brass portions of the specimen were bonded along a common edge. Whole-field measurements were made by high-sensitivity moire interferometry. A companion finite element numerical analysis of a similar body was conducted to help interpret the experimental results. The experiments documented a strong free-edge effect along the entire perimeter of the joint, an effect akin to a line singularity along the perimeter. High stresses in the edge-effected zone were determined from measurements, and enormous stress gradients were deduced by analysis. The largest stresses were found at the corner, where two edge-effected zones intersected. Lawrence F. Reardon Jun. 1989 39 p The environmental aspect of elevated temperature and its relationship to the science of strain gage calibrations of aircraft structures are addressed. A section of a wing designed for a high-speed aircraft structure was used to study this problem. This structure was instrumented with strain gages calibrated at both elevated and room temperatures. Load equations derived from a high-temperature load calibration were compared with equations derived from an identical load calibration at room temperature. The implications of the high temperature load calibration were studied from the viewpoint of applicability and necessity. Load equations derived from the room temperature load calibration resulted in generally lower equation standard errors than equations derived from the elevated temperature load calibration. A distributed load was applied to the structure at elevated temperature and strain gage outputs were measured. This applied load was then calculated using equations derived from both the room temperature and elevated temperature calibration data. It was found that no significant differences between the two equation systems existed in terms of computing this applied distributed load, as long as the thermal shifts resulting from thermal stresses could be identified. This identification requires a heating of the structure. Therefore, it is concluded that for this structure, a high temperature load calibration is not required. However, a heating of the structure is required to determine thermal shifts. Author N89-28035*# National Aeronautics and Space Administration. Kay S. Bales Apr. 1989 95 p (NASA-TM-101592; NAS 1.15:101592) Avail: NTIS HC A05/MF A01 CSCL 20K The Objectives, FY 1989 Plans, Approach, and FY 1989 Milestones for the Structural Mechanics Division's research programs are presented. Fiscal year 1988 Accomplishments are presented where applicable. This information is useful in program |