Showing papers by "General Dynamics published in 1982"

Characterizing delamination growth in graphite-epoxy

Abstract: As part of an overall effort to develop durability and damage tolerance methodology for graphite-epoxy composites, coupon specimens have been developed to measure the fundamental static fracture and subcritical growth behavior of delaminations. Two basic designs, one for the tensile opening mode (Mode I) and one for the forward shear mode (Mode II), are described. These specimens were used to characterize the behavior of two types of interfaces (0/0 and 0/90) for static fracture, constant amplitude fatigue, and spectrum fatigue. Fracture mechanics technology was applied through the principles of strain-energy release rate. Three-dimensional finite-element analyses were employed to interpret the experimental results. A simple growth law was shown to correlate the constant-amplitude and spectrum-growth data. It was found that the applied cyclic load must be nearly equal to the critical static load to obtain observable growth in the tensile opening mode. On the other hand, the graphite-epoxy delamination growth rate in the forward shear mode is comparable to the aluminum growth rate in tension, which suggests that shear is the chief subcritical growth mode for graphite-epoxy.

An Investigation of Cumulative Damage Development in Quasi-Isotropic Graphite/Epoxy Laminates

Abstract: Results of an experimental investigation of cumulative damage development in two unnotched quasi-isotropic graphite/epoxy laminates subjected to quasi-static tension and tension-tension fatigue are presented. Damage development in the form of transverse cracking in all off-axis laminae, longitudinal cracking, and delamination was monitored via the surface replication technique. Results of the study include a detailed description of the chronology of damage development prior to failure. Evidence also is presented in support of a damage model based on the concept of a characteristic damage state.

Digital circuit unit testing system utilizing signature analysis

Abstract: A system for testing digital circuit units at the design speed of the circuit. A first memory stores a minimized set of optimum generated predetermined test patterns for application to a unit under test. A second memory stores expected signature patterns corresponding to signature patterns that are derived from the unit under test in response to the predetermined test patterns when the unit under test is functioning properly. A signature analyzer derives signature patterns from a unit under test in response to the application of the test patterns to the unit. A comparator compares the derived signature patterns with the expected signature patterns and provides an indication of the results of the comparison. A clock provides a clock signal having a pulse rate that corresponds to the design speed of the unit under test; and a sequential counter responds to said clock signal by providing a sequential count to the first memory for addressing the first memory at storage positions therein having addresses corresponding to the sequential count to cause the predetermined test patterns to be read from the first memory and applied to the unit at a speed that corresponds to the design speed of the unit under test. The testing system further includes a backtracing system for enabling determination of the location of faults in the unit under test.

Method of making pressure point contact system

Abstract: A system of disassemblable contact junctions for prefabricated conductor paths, such as may be provided on printing wiring boards, flexible printed cables or the like, Each contact junction includes a pressure point contact attached to an associated conductor path. Both the pressure point contact and the opposed conductor path are coated with solder or equivalent. Rigid blocks on opposite sides of the two sets of circuit conductors with an interspersed pad of compliant material, such as rubber, hold the assembly together under substantial pressure. Each of the pressure point contacts is formed with a ridge along the contacting face which, under the pressure developed by the assembly, penetrates through the oxide surfaces of the contacting solder layers, breaking the oxide surfaces and forming a gas tight electrical connection provided by the cold flow of the solder. The assembly can be readily disassembled and rejoined in case repairs are needed or it is desired to substitute connections to another set of prefabricated conductor paths. The individual contacts may be formed by etching a sheet of copper alloy to develop a comb bearing the contacts, chemically milling the pressure point contact elements along the end of the comb to form the raised ridges on the base portions, coating and attaching the contacts with solder on a series of prefabricated conductors while temporarily mounting them in position by means of a soldering tool, and then breaking off the comb to leave the contacts in the desired positions.

Optical system to compute intensity moments: design.

Abstract: A frequency-multiplexed coherent optical processor is described that can compute the intensity moments of a gray-scale input image. The space-bandwidth product and dynamic range of the system's components are discussed. A major feature of the system is the ability to operate easily on its outputs to obtain bipolar moments and to correct for various component errors, nonlinearities, and nonuniformities.

Attitude insensitive lubrication systems

Abstract: A lubrication system for a gearbox having a forced flow of lubricant around one or more flow loops using dynamic forces imparted to the lubricant by a major element, preferably one primarily serving another function, which acts as a pump and cooperates with the gearbox casing to provide a dynamic reservoir. The primary lubrication flow loop includes an efficient flow diverter to feed a lubricant distribution reservoir, dispensers, predetermined regulated flow paths to critical items and a centrifugal separator built into the pump to deaerate the lubricant.

Axial flow fan

Abstract: An axial flow fan has a plurality of impeller blades spaced around a hub assembly. The leading edge of each blade overlaps completely the trailing edge of the preceding blade, and the angular spacing between the radial center lines of the blades is unequal, preferably varying in a sinusoidal pattern, so that tonal noise of the fan is effectively attenuated.

Augmented proportional navigation in second order predictive scheme

Abstract: A method for augmenting a noise-adaptive predictive proportional navigation terminal guidance scheme. In a third order configuration with noise adaptive varying gain parameters calculated as a function of time-to-go, this system implements an optimal control law to augment proportional navigation with a target acceleration feed forward term and a navigation ratio which is a function of time-to-go and the control effort weighting factor. This third order system may also implement another optimal control law to even greater advantage, taking into account not only target acceleration but also missile acceleration in a feedback loop which, together with the navigation ratio, are both functions of time-to-go and autopilot dynamics, whereby first order autopilot time lag is accounted for. This system is particularly useful for high and medium altitude targets and results in significant miss distance improvement for terminal guidance against small maneuvering targets.

Conductive resealable pouch

Abstract: A pouch for protecting electrosensitive components contained therein from physical shock and electrostatic damage during handling and storage. In one embodiment, the pouch comprises two composite panels, each comprising a sheet of conductive material as the outside layer, a sheet of electrostatic-free material as the inside layer and a layer of open cell cushioning material sandwiched therebetween. Each panel is sealed to enclose the material therein and both panels are then sealed together on both sides and one end. The open end has an interlocking closure to allow components to be inserted into the pouch and for the pouch to be thereafter closed. In another embodiment, the pouch is formed of a pair of extruded, tubular members respectively constituting the conductive material layer and the electrostatic-free material layer with sheets of cushioning material sandwiched between them. The assembly is sealed at one end and provided with a releasable closure member at the other end. The pouch may also be formed as an elongated sandwich of the three material layers described, folded in half lengthwise and sealed along the side edges.

Heterodyne laser radar SNR from a diffuse target containing multiple glints.

Abstract: A coherent laser radar performance model is formulated using the Huygens-Fresnel principle for a near-field or far-field diffuse target which may contain a number of glints. The received signal is calculated for a truncated Gaussian-transmitted beam mixed with a matched Gaussian or a uniform local oscillator (LO) beam. In general, the uniform LO beam provides a good or better mixing than the matched Gaussian beam. The effects of beam truncation and receiver aperture size on the received signal level are presented. In the case of a far-field diffuse target, an increase in SNR is obtained if the receiver aperture increases to about three times the transmitter aperture, or if the transmitter aperture increases to about three times the receiver aperture. The target signature statistics and the weather statistics are considered as random parameters in the evaluation of receiver performance characteristics.

Durability Design Requirements and Analysis for Metallic Airframes

Abstract: Air Force durability design requirements are reviewed and durability analysis methodology capable of satisfying these requirements are presented. The proposed methodology includes (1) durability critical parts, (2) guidelines for economic life criteria, and (3) analytical procedures for quantifying overall structural damage due to fatigue cracking. Two analytical formats for quantifying economic life are proposed: probability of crack exceedance and ratio of repair cost/replacement cost. Although the analytical methodology has been developed and verified using a fastener hole crack as the prototype, the basic concepts and methodology apply to cracks in other structural details as well. The durability analysis methodology is based on a fracture mechanics philosophy, using a probabilistic format but with deterministic crack growth. The methodology accounts for initial quality, crack growth accumulation in a population of details, load spectra, and structural properties. Essential elements of the methodology are presented, including an evaluation and illustration of the analytical methodology using test results for the F-16 full-scale durability test article.

Radiation hard MOS devices and methods for the manufacture thereof

Abstract: Radiation hard, N-channel MOS devices comprising active regions surrounded by field oxide protected by an underlying region of heavily doped p-type material. The guard region is doped heavily enough to provide field inversion voltages in the range of 50 V to 60 V prior to irradiation. The guard region is separated from the source and drain regions to provide acceptably high breakdown voltages. The devices are produced with minor variations to well known, high density local oxidation of silicon-type processes.

Shock wave end cap removal device

Abstract: A missile launch cannister end cap removal device utilizing the pressure pulse of a traveling shock wave within the cannister is disclosed. A pressure chamber, the interior of which is separated from the interior of the cannister by a diaphragm having a selected rupture pressure. Gas pressure is generated in the chamber by the firing of an explosive charge at the appropriate time in the missile launch sequence. The diaphragm is ruptured by the pressure developed in the chamber introducing a traveling shock wave into the interior of the missile cannister. The pressure pulse of the shock wave removes the end caps fitted over the open ends of the cannister.

Armored missile launch/shipping container

Abstract: A missile launch system includes a missile launch support structure mounted on a launch platform and including a pair of spaced apart rails having longitudinal slots formed therein, and a cooperating missile launch container having a cylindrical bore for receiving and supporting a missile for launching includes radially extending ribs spaced and oriented to engage and slide along the slots in the rails for supporting the missile launch container for launching of the missile.

Fourth order predictive, augmented proportional navigation system terminal guidance design with missile/target decoupling

Abstract: A method for augmenting a noise-adaptive predictive proportional navigation terminal guidance scheme. In a fourth order configuration with noise adaptive varying gain parameters calculated as a function of time-to-go, this system implements an optimal control law to augment proportional navigation with target and missile information terms and a navigation ratio which is a function of time-to-go. By employing a fourth order system, enhanced use may be made of information already available in the guidance computer and missile control system to decouple target motion information from the missile control signals. Decoupled target motion information facilitates blind-mode operation in the end game, the last few seconds before intercept. Decoupled missile control information enables the airframe to be controlled to predefined orientations for aimed warhead applications. This system is particularly useful for high and medium altitude targets and results in significant miss distance improvement for terminal guidance against small maneuvering targets. The system has additional benefits in that it results in nearly optimal miss distance behavior with sensitivity to unmodeled errors being substantially less than that in modern guidance systems.

Fatigue crack initiation and strain-controlled fatigue of some high strength low alloy steels

Abstract: Initiation and growth of fatigue microcracks were investigated in several Nb and V alloyed high strength low alloy steels, including conventional and dual phase microstructures. Fatigue microcracks initiated along prominent slip bands. Macrocracks formed by linking up of small microcracks. At low applied stress or strain, the number of cycles to crack initiation increased with the cyclic yield stress. Comparing the cyclic stress-strain curves to the monotonie stress-strain curves, cyclic hardening or softening occurred, depending upon strain amplitude. Plateau regions were observed in plots of cyclic stress amplitudevs cyclic plastic strain amplitude obtained by increasing the total strain amplitude in steps after 30 cycles at each step. In polycrystalline 0.03 pct Nb steel, the plateau region was identified with prominent slip band formation, as others have observed in single crystals of copper, C-doped iron, and other metals.

Method of making a thin-film solar cell

Abstract: A method of making a thin gallium arsenide solar cell having a reflecting back surface and coplanar electrical contacts. A photovoltaic cell comprising gallium arsenide is produced in a self-supporting thickness by conventional methods. A pattern of contact lines and a bus contact are formed on the front surface of the cell and a transparent coverslide is bonded thereover. The back of the cell is chemically etched away until the minimum effective thickness is reached, then etching in the bus contact region is continued until the bus is exposed. Any stop-etch material used to prevent excessive etching of the cell material is removed and a reflective contact material is applied to the back of the cell. The resulting solar cell is light in weight and both front and back connections can be made from the back of the cell, making it particularly suitable for use in space-based arrays.

Simplified frequency scheme for coherent transponders

Abstract: A coherent transponder having a transmitter and a receiver operating at different frequencies with each including a numerically controlled oscillator for controlling the frequency thereof through a single-sideband modulator and various outputs from a phase-locked loop the frequencies of the numerically controlled oscillators and the phase-locked loop being referenced to a single crystal controlled oscillator.

Virtual time base direct synchronizer and method therefor

Abstract: A system for virtual time base direct synchronization in which a hopping sequence signal grossly synchronized with a received hopped base band has a fine synchronization correction performed by a virtual time shift of the hopping reference through first derivative subtraction of the phase of a hopped carrier signal, which in effect brings the hopping sequence signal into time alignment with the received hopped base band.

Gyroscopically steerable bullet

Abstract: A projectile body has a gyro mounted therein including a rotor and a mechanism for supporting the rotor for rotation about a spin axis initially coincident with the longitudinal axis of the projectile body and pivotable away from the longitudinal axis of the projectile body. The rotor is initially locked to the projectile body so that it is spun with the projectile body during launch. Thereafter, the rotor is unlocked and the projectile body is de-spun to a relatively slow rate of rotation while transferring angular momentum to the free spinning rotor which continues to rotate at a high rate relative to the projectile body. Rotationally phased steering commands, which are generated from on-board homing sensor signals or up-link data signals received from a remote error sensor, are applied to a linear actuator within the projectile body. The actuator pivots the spin axis of the rotor away from the longitudinal axis of the projectile body. The resulting precession torque of the spinning rotor induces a change in the angle of attack between the projectile body axis and the actual velocity vector of the projectile thereby inducing midcourse trajectory shaping.

Whisker Growth during Epitaxy of GaAs by Molecular Beam Epitaxy

Abstract: GaAs whiskers, many of them originating from one point, were observed on GaAs epitaxial layers grown by molecular beam epitaxy. Very small pools of Ga and/or In are believed to precipitate the whiskers which grow at a relatively rapid rate. This whisker growth process is similar to the vapor-liquid-solid (VLS) growth and may not necessarily be a result of any particular substrate defect.

F-16 Flutter Suppression System Investigation Feasibility Study and Wind Tunnel Tests

Abstract: A study was conducted to determine the feasibility of employing active controls on the F-16 to suppress wing- store flutter for several external store configurations. It was determined that the existing flaperons, with modifications to the integrated servoactuators, were effective in suppressing flutter. The F-16 flutter model was tested with active flaperons. Open-loop frequency response functions (FRF's) were successfully measured in the wind tunnel environment both with the feedback loop physically opened and with the loop closed. These measurements provided guidance in the selection of sensor locations and feedback control laws to suppress flutter. Control law variations were made to obtain the desired FRF characteristics. A 100% increase in dynamic pressure above the flutter dynamic pressure was demonstrated. IGHTER aircraft are required to carry a very large number of external store configurations. The probability is high that at least a small subset of these configurations will flutter within the desired operational envelope of the airplane. This probability is further increased as new stores are added to the operational airplane inventory. When wing-store flutter problems occur, the solution requires a modification of the airplane (usually a change in stiffness and weight) and/or a speed restriction which reduces the operational envelope of the airplane. Flutter suppression with active controls is another solution which has been investigated in recent years. Several approaches have been taken to design these sys- tems.1-3 One of the more promising approaches to the design of calibrated active control systems is the frequency response method. This approach is attractive because of the state of development of methods for computing oscillatory aerodynamic pressure distributions, because frequency response functions (FRF's) are experimentally measurable, and because the military specification for the stability of aeroservoelastic systems is based on the Nyquist criteria. This method was applied in a flutter suppression system (FSS) feasibility study4 for the F-4. The results of this study indicate that the milder flutter modes and the lower flutter frequencies associated with wing-store configurations could be relatively easily suppressed with active controls. The initial design approach for the active control system for the YF-17 semispan flutter model was the root locus method.5 However, a modified Nyquist approach was subsequently used.6 The Nyquist stability criteria has been applied extensively by Turner.7 The Nyquist criteria was employed as the principal design tool in the F-16 FSS investigations. For the system with negative feedback shown in Fig. 1, the transfer function for the closed loop system is

Airborne missile launcher

Abstract: An airborne missile launcher for air launching of man-portable, tube-launched missiles includes a central support frame with attachment means for detachable attachment to an aircraft or other launching platform, with a central frame member having a launch tube saddle support assembly at each side of the frame member with quick detachable clamp means and an alignment guide for quickly positioning and securing launch tubes into position with auto connecting means for automatically connecting the electronics control system and coolant gas to the launch tube assembly upon clamping the assembly into position. An aerodynamic shell encloses the support structure and includes a quick release cover for providing access to the tube clamp assemblies for loading and unloading launch tubes.

Combined rocket motor warhead

Abstract: A solid fuel rocket in which the rocket casing acts as a warhead. Solid propellant rocket motors require relatively heavy cases to contain the 1000-2000 psi combustion pressure needed for efficient performance. This casing can be used as a fragmentation warhead by forming longitudinal grooves in the elongated rocket casing, causing the casing to fracture along the grooves and allowing the pressure within the casing to disperse the fragments. The resulting strip-like fragments are particularly useful against "soft" equipment targets, such as anti-vehicle and anti-radar applications. Several different methods for rupturing the case along spaced, parallel longitudinal lines are disclosed. This system eliminates the need for a separate warhead including case and explosive at the cost of a slight increase in propellant case thickness and weight.

Dielectric resonator controlled planar IMPATT diode oscillator

Abstract: An IMPATT diode oscillator wherein the diode is coupled to a first transmission line in turn coupled to a bias port at one end and to a coupled line transformer formed with a second transmission line at the other A stabilizing load is coupled to the first transmission line between the diode and the bias port A first tunable resonator controlling the fundamental frequency of the oscillator and a second tunable resonator controlling the second harmonic frequency of the oscillator are coupled to the first transmission line between the diode and the stabilizing load so that independent control of the fundamental and the second harmonic is attained in a temperature stable device

Numerically controlled oscillator

Abstract: A radio frequency numerically controlled oscillator comprising N one bit adders each providing sum and carry outputs to one of N two bit registers. Sum, carry and frequency selection inputs are combined by each adder to form sum and carry outputs. These results are held by the associated register when triggered by a clock input. A fast parallel adder/latch is employed which has two stages connected serially to generate sums on opposite phases of a two phase clock.

Stability of a matrix polynomial in discrete systems

Abstract: Two sufficient conditions that the determinant of a nonsingular real ( m \times m ) matrix polynomial of n th order has all its roots inside the unit circle have been obtained. These conditions are represented in terms of rational functions of the coefficient matrices. Therefore, these conditions do not require the computation of the determinant polynomial. The first condition is given in terms of the positive definiteness of an ( mn \times mn ) symmetric matrix, while the second condition is expressed by the positive definiteness of an ( m \times m ) Hermitian matrix which is a function of z, |z| \leq 1 . The first condition implies the second, and hence is more restrictive than the second.

Fiber optic matrix multiplier

Abstract: A matrix multiplier system incorporating an integrated fiber optic coupling array in combination with an arrangement for individually modulating the signals on the respective optical fiber transmission lines to develop the matrix multiplication. Each of the individual couplers accomplishes the coupling of an input signal into a bi-directional fiber optic transmission line with high efficiency and unilateral coupling effect. The signal thus coupled into the bi-directional transmission line is reflected back to the coupler output after multiplication by the modulating vector component for the individual coupler element. Because of the fabrication of a large number of identical fiber optic couplers in a compact, integral array and the manner in which the light signals can be modulated, the matrix multiplier system is extremely effective in pattern recognition, signal discrimination, selected signal enhancement, and the like.

Steering mechanism for an explosively fired projectile

Abstract: A projectile trajectory correction system, the projectile itself including a unique steering arrangement. The projectile, initially part of a shell cartridge, is fired, and its position is automatically sensed. A corrected trajectory necessary to hit a target is calculated and data commands are transmitted to the projectile. The data command signals are sensed by an antenna on the projectile. The antenna in turn generates a signal which is fed to the projectile steering mechanism which is deflected in response thereto to steer the projectile onto the correct trajectory. The steering mechanism includes an elongated rod extending from the rear of the projectile into the surrounding air stream. Deflection of the rod provides the actual steering.