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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,045 records · Page 58

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NASA NTRS1983

Self-shadowing of orbiting trusses

The approach used to assess shadowing reductions on the heating of orbiting trusses involves determining the heating rates with slender member shadowing effects included and then obtaining the thermal response of the shadowed member. Steps taken to identify shadowers, find locations where shadowing occurs and calculate shadow intensity are listed. The finite element thermal structural analysis of cable stiffened space structure is delineated and the exact solution of the caternary problem is given. Typical cable surface heating rates are plotted. The structural analysis includes large deformation (nonlinear), thermal effect, and the pretension effect. Displacements and stresses are computed at different orbital positions for an orbit.

Mahaney, J.↗

NASA NTRS1983

Evolution of integrated panel structural design and interfaces for PV power plants

The evolution of integrated photovoltaic (PV) panel design at ARCO Solar is discussed. Historically, framed PV modules of about 1 x 4-ft size were individually mounted in the field on fixed support structures and interconnected electrically with cables to build higher-power arrays. When ARCO Solar saw the opportunity in 1982 to marry its PV modules with state-of-the-art heliostat trackers developed by ARCO Power Systems, it became obvious that mounting individual modules was impractical. For this project, the framed modules were factory-assembled into panels and interconnected with cables before being mounted on the trackers. Since then, ARCO Solar made considerable progress and gained substantial experience in the design and fabrication of large PV panels. Constraints and criteria considered in these design activities included static and dynamic loads; assembly and transportation equipment and logistics, structural and electrical interfaces, and safety and grounding concerns.

Arnett, J. C.↗

NASA NTRS1986

Plug-In RF Selector Switch

Short, direct link between switch and filters reduces signal loss. New switch attaches directly to filter housing, eliminating cables and connectors. As result, losses in transmitter and receiver paths reduced by about 0.4 dB. Because connectors and cables are not used, RF path loss for selected signal through switch and filter is smaller than usual.

Hwon, A. H.↗

NASA NTRS1986

Connectors and Wiring for Cryogenic Temperatures

Tests performed at Langley Research Center to find connectors, cables, and other electrical components suitable for use in cryogenic environment described. In addition, several electrical cables have to flex under cryogenic conditions. Tests necessary to qualify materials for use in National Transonic Facility (NTF), which operates at temperature range from 175 degrees to - 300 degrees F (353 to 89 K).

Turner, R. D.↗

NASA NTRS1986

Tester for Distress Beacons

Distress beacons on aircraft and boats checked for proper operation with aid of onboard monitor. Monitor mounted in aircraft cockpit or at wheel of boat. Connected to beacon electronics by cable. Monitor used with interface circuitry in beacon, which acts as buffer so that operation of beacon is not adversely affected if monitor is removed or if connecting cable is accidentally short circuited.

Wade, W. R.↗

NASA NTRS1984

A comparison of lightning and nuclear electromagnetic pulse response of tactical shelters

The internal response (electromagnetic fields and cable responses) of tactical shelters is addressed. Tactical shelters are usually well-shielded systems. Apart from penetrations by signal and power lines, the main leakage paths to the interior are via seams and the environment control unit (ECU) honeycomb filter. The time domain in three-dimensional finite-difference technique is employed to determine the external and internal coupling to a shelter excited by nuclear electromagnetic pulses (NEMP) and attached lightning. The responses of interest are the internal electromagnetic fields and the voltage, current, power, and energy coupled to internal cables. Leakage through the seams and ECU filter is accomplished by their transfer impedances which relate internal electric fields to external current densities. Transfer impedances which were experimentally measured are used in the analysis. The internal numerical results are favorably compared to actual shelter test data under simulated NEMP illumination.

Perala, R. A.↗

NASA NTRS1985

Parametric Stiffness Control of Flexible Structures

An unconventional method for control of flexible space structures using feedback control of certain elements of the stiffness matrix is discussed. The advantage of using this method of configuration control is that it can be accomplished in practical structures by changing the initial stress state in the structure. The initial stress state can be controlled hydraulically or by cables. The method leads, however, to nonlinear control equations. In particular, a long slender truss structure under cable induced initial compression is examined. both analytical and numerical analyses are presented. Nonlinear analysis using center manifold theory and normal form theory is used to determine criteria on the nonlinear control gains for stable or unstable operation. The analysis is made possible by the use of the exact computer algebra system MACSYMA.

Moon, F. C.↗

NASA NTRS1984

Concepts and effects of damping in isolators

A series of innovative designs and inventions which led to the solution of many aerospace vibration and shock problems through damping techniques is presented. The design of damped airborne structures has presented a need for such creative innovation. The primary concern was to discover what concepts were necessary for good structural damping. Once these concepts are determined and converted into basic principles, the design of hardware follows. The following hardware and techniques were developed in support of aerospace program requirements: shipping containers, alignment cables for precision mechanisms, isolation of small components such as relays and flight instruments, isolation for heavy flight equipment, coupling devices, universal joints, use of wire mesh to replace cable, isolation of 16-dB, 5000 lb horn, and compound damping devices to get better isolation from shock and vibration in a high steady environment.

Kerley, J.↗

NASA NTRS1985

Wavelength division multiplexing

Wavelength division multiplexing (WDM) represents an approach for expanding the communication capacity and for implementing special data techniques in a fiber optics system. This technology is implemented by adding optical sources of different wavelengths at optical transmitting locations. The present paper is concerned with some of the current efforts in WDM. WDM applications are related to long haul communications, local area data networks, spacecraft and aircraft data systems, fault tolerant computer networks, special sensor devices, high speed data processors, closed circuit and cable television, and submarine cable systems. Attention is given to the current state of wavelength division multiplexing applications, the availability and status of WDM components semiconductor lasers/transmitters, availability and status of fiber optic detectors/receivers, optical fibers/cables/connectors/taps/star couplers, wavelength multiplexers/demultiplexers, and future WDM for local area networks.

Hendricks, H. D.↗

NASA NTRS1986

Input impedance of a probe-fed circular microstrip antenna with thick substrate

A method of computing the input impedance for the probe fed circular microstrip antenna with thick dielectric substrate is presented. Utilizing the framework of the cavity model, the fields under the microstrip patch are expanded in a set of modes satisfying the boundary conditions on the eccentrically located probe, as well as on the cavity magnetic wall. A mode-matching technique is used to solve for the electric field at the junction between the cavity and the coaxial feed cable. The reflection coefficient of the transverse electromagnetic (TEM) mode incident in the coaxial cable is determined, from which the input impedance of the antenna is computed. Measured data are presented to verify the theoretical calculations. Results of the computation of various losses for the circular printed antenna as a function of substrate thickness are also included.

Davidovitz, M.↗

NASA NTRS1987

Hydraulic Calibrator for Strain-Gauge Balances

Instrument for calibrating strain-gauge balances uses hydraulic actuators and load cells. Eliminates effects of nonparallelism, nonperpendicularity, and changes of cable directions upon vector sums of applied forces. Errors due to cable stretching, pulley friction, and weight inaccuracy also eliminated. New instrument rugged and transportable. Set up quickly. Developed to apply known loads to wind-tunnel models with encapsulated strain-gauge balances, also adapted for use in calibrating dynamometers, load sensors on machinery and laboratory instruments.

Skelly, Kenneth↗

NASA NTRS1986

Design and fabrication of the 20 km/10 kV electromechanical tether for TSS-1 using high impact conductor (Hiwire)

The development of a 20-km electromechanical tether for the tethered satellite system (TSS) is described. The basic design requirements for electromagnetic cables and for conductors in cables subject to stresses and cyclic loading are discussed. The tether fabricatioon procedures involve: (1) conductor twisting around the core, (2) insulation extrusion, (3) strength member braiding, and (4) protective jacket braiding.

Scala, E.↗

NASA NTRS1986

General equilibrium characteristics of a dual-lift helicopter system

The equilibrium characteristics of a dual-lift helicopter system are examined. The system consists of the cargo attached by cables to the endpoints of a spreader bar which is suspended by cables below two helicopters. Results are given for the orientation angles of the suspension system and its internal forces, and for the helicopter thrust vector requirements under general circumstances, including nonidentical helicopters, any accelerating or static equilibrium reference flight condition, any system heading relative to the flight direction, and any distribution of the load to the two helicopters. Optimum tether angles which minimize the sum of the required thrust magnitudes are also determined. The analysis does not consider the attitude degrees of freedom of the load and helicopters in detail, but assumes that these bodies are stable, and that their aerodynamic forces in equilibrium flight can be determined independently as functions of the reference trajectory. The ranges of these forces for sample helicopters and loads are examined and their effects on the equilibrium characteristics are given parametrically in the results.

Cicolani, L. S.↗

NASA NTRS1986

High frequency power distribution system

The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

Patel, Mikund R.↗

NASA NTRS1989

Interface For Fault-Tolerant Control System

Interface unit and controller emulator developed for research on electronic helicopter-flight-control systems equipped with artificial intelligence. Interface unit interrupt-driven system designed to link microprocessor-based, quadruply-redundant, asynchronous, ultra-reliable, fault-tolerant control system (controller) with electronic servocontrol unit that controls set of hydraulic actuators. Receives digital feedforward messages from, and transmits digital feedback messages to, controller through differential signal lines or fiber-optic cables (thus far only differential signal lines have been used). Analog signals transmitted to and from servocontrol unit via coaxial cables.

Shaver, Charles↗

NASA NTRS1989

Compliant Prosthetic Or Robotic Joint

Rotation partly free and partly restrained by resilience and damping. Joint includes U-shaped x- and y-axis frames joined by cables that cross in at center piece. The y-axis frame rotates about y-axis on roller bearing within predetermined angular range. The y-axis frame rotates slightly farther when arm strikes stop, because cables can twist. This mimics compliant resistance of knee joint reaching limit of its forward or backward motion. Used in prosthetic device to replace diseased or damage human joint, or in robot linkage to limit movement and cushion overloads.

Kerley, James J.↗

NASA NTRS1988

Successful expert systems for space shuttle payload integration

Expert systems are successfully applied to solve recurring NASA Space Shuttle orbiter payload integration problems. Recurrence of these problems is the result of each Space Shuttle mission being unique. The NASA Space Shuttle orbiter was designed to be extremely flexible in its ability to handle many types and combinations of satellites and experiments. This flexibility results in different and unique engineering resource requirements for each of the payload satellites and experiments. The first successful expert system to be applied to these problems was the Orbiter Payload Bay Cabling Expert System (EXCABL), developed at Rockwell International Space Transportation Systems Division. The operational version of EXCABL was delivered in 1986 and successfully solved the payload electrical support services cabling layout problem. As a result of this success, a second expert system, Expert Drawing Matching System (EXMATCH), was developed to generate a list of the reusable installation drawings available for each EXCABL solution. EXMATCH went operational in 1987. As a result of these initial successes, the need for a third expert system was defined and is awaiting development. This new Expert System, called Technical Order Listing Expert System (EXTOL), will generate a list of all the applicable reusable installation drawings available to support the total payload bay mission provisioning and installation effort. This paper describes these expert systems, the individual problems that they were designed to solve, their individual solutions, and the degree of success achieved. These expert systems' instantiate the applicability of this technology to the solution of real-world Space Shuttle payload integration problems.

Morris, Keith↗

NASA NTRS1988

Simulation and control of a 20 kHz spacecraft power system

A detailed computer representation of four Mapham inverters connected in a series, parallel arrangement has been implemented. System performance is illustrated by computer traces for the four Mapham inverters connected to a Litz cable with parallel resistance and dc receiver loads at the receiving end of the transmission cable. Methods of voltage control and load sharing between the inverters are demonstrated. Also, the detailed computer representation is used to design and to demonstrate the advantages of a feed-forward voltage control strategy. It is illustrated that with a computer simulation of this type, the performance and control of spacecraft power systems may be investigated with relative ease and facility.

Wasynczuk, O.↗