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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Fiber optics for aircraft engine/inlet control

NASA programs that focus on the use of fiber optics for aircraft engine/inlet control are reviewed. Fiber optics for aircraft control is attractive because of its inherent immunity to EMI and RFI noise. Optical signals can be safely transmitted through areas that contain flammable or explosive materials. The use of optics also makes remote sensing feasible by eliminating the need for electrical wires to be connected between sensors and computers. Using low-level optical signals to control actuators is also feasible when power is generated at the actuator. Each application of fiber optics for aircraft control has different requirements for both the optical cables and the optical connectors. Sensors that measure position and speed by using slotted plates can use lossy cables and bundle connectors if data transfer is in the parallel mode. If position and speed signals are multiplexed, cable and connector requirements change. Other sensors that depend on changes in transmission through materials require dependable characteristics of both the optical cables and the optical connectors. A variety of sensor types are reviewed, including rotary position encoders, tachometers, temperature sensors, and blade tip clearance sensors for compressors and turbines. Research on a gallium arsenide photoswitch for optically switched actuators that operate at 250 C is also described.

Baumbick, R. J.↗
NASA NTRS1981

A new CT collimator for producing two simultaneous overlapping slices from one scan

A new CT collimator is developed which is capable of producing two simultaneous successive overlapping images from a single scan. The collimator represents a modification of the standard EMI 5005 collimator achieved by alternately masking one end or portions of both ends of the X-ray detectors at a 13-mm beamwidth so that a set of 540 filtered projections is obtained for each scan which can be separated into two sets of interleaved projections corresponding to views 3 mm apart. Tests have demonstrated that the quality of the images produced from these two projections almost equals the quality of those produced by the standard collimator from two separate scans. The new collimator may thus be used to achieve a speed improvement in the generation of overlapping sections as well as a reduction in X-ray dosage.

Kwoh, Y. S.↗
NASA NTRS1981

Brushfire arc discharge model

A one dimensional arc discharge model incorporating a brushfire-type propagation of a discharge wavefront was investigated. A set of equations, developed and their which include electrical, thermal and plasma parameters, were solutions shown to be consistent with a propagating brushfire wavefront. Voltage, current, plasma density, temperature, and resistivity profiles were obtained. Mechanical forces, magnetic and electrostatic were considered in evaluating the flashover to blowout current ratio, G', for arc discharges with the brushfire parameters developed in the model. This ratio is an important factor in determining the electromagnetic interference (EMI) impact of arc discharges on spacecraft electrical subsystems. The conclusion of the analysis is that electrostatic forces are much more important than magnetic forces. The magnitude of the G' factor obtained, 58.5 percent, is within the range of those obtained by experimental means. Improvements in the analytical model as well in the experimental approach are recommended.

Lnouye, G. T.↗
NASA NTRS1980

P78-2 engineering overview

Data from the P78-2 spacecraft are being used in verifying and validating analytical tools being developed for the design of spacecraft, such as NASCAP, for updating Military Standard 1541, for investigation of materials contamination, and for a study of the physics of charging. The analysis of this data has already resulted in changes in laboratory testing procedures, in a better understanding of some properties of materials exposed to the space environment, and in some insight into the EMI caused by discharges on spacecraft in a plasma environment. Some examples of early results from the engineering experiments are presented.

Vampola, A. L.↗
NASA NTRS1980

Rectenna system design

The function of the rectenna in the solar power satellite system is described and the basic design choices based on the desired microwave field concentration and ground clearance requirements are given. One important area of concern, from the EMI point of view, harmonic reradiation and scattering from the rectenna is also designed. An optimization of a rectenna system design to minimize costs was performed. The rectenna cost breakdown for a 56 w installation is given as an example.

Brown, W. C.↗
NASA NTRS1982

Measurements by the plasma diagnostics package on STS-3

A comprehensive set of measurements about the orbiter environment are provided by the plasma diagnostics package (PDP). Ion and electron particle densities, energies, and spatial distribution functions; ion mass for identification of particular molecular ion species; and magnetic fields, electric fields and electromagnetic waves over a broad frequency range are studied. Shuttle environmental measurements will be made both on the pallet and, by use of the remote manipulator system (RMS), the PDP will be maneuvered in and external to the bay area to continue environmental measurements and to carry on a joint plasma experiment with the Utah State University fast-pulsed electron generator. Results of orbiter environment EMI measurements and S-band field strengths as well as preliminary results from wake search operations indicating wake boundary identifiers are reported.

Shawhan, S. D.↗
NASA NTRS1983

The electromagnetic environment for the Space Shuttle orbiter

The electromagnetic environment of the Shuttle orbiter is discussed with respect to the electromagnetic compatibility of the orbiter and its cargo. Effects on payloads of the orbiter's Ku-band antenna are considered, along with the effects of unintentional emissions in the cargo bay, the magnetic fields produced by the orbiter and various payloads, lightning-produced magnetic fields, and noise and transients in the AC and DC power buses. Special EMI testing is described that was carried out to substantiate the orbiter's electromagnetic compatibility. It is concluded that the orbiter presents a very benign electromagnetic environment for cargo except for payloads or experiments that use very sensitive receivers or instruments that can measure low magnetic or electric fields.

Giffin, B. L.↗
NASA NTRS1982

Description of the plasma diagnostics package (PDP) for the OSS-1 Shuttle mission and JSC plasma chamber test in conjunction with the fast pulse electron gun (FPEG)

The objectives, equipment, and techniques for the plasma diagnostics package (PDP) carried by the OSS-1 instrument payload of the STS-4 and scheduled for the Spacelab-2 mission are described. The goals of the first flight were to examine the Orbiter-magnetoplasma interactions by measuring the electric and magnetic field strengths, the ionized particle wakes, and the generated waves. The RMS was employed to lift the unit out of the bay in order to allow characterization of the fields, EM interference, and plasma contamination within 15 m of the Orbiter. The PDP will also be used to examine plasma depletion, chemical reaction rates, waves, and energized plasma produced by firing of the Orbiter thrusters. Operation of the PDP was carried out in the NASA Space Environment Simulation Laboratory test chamber, where the PDP was used to assay the fields, fluxes, wave amplitudes, and particle energy spectra. The PDP instrumentation is also capable of detecting thermal ions, thermal electrons suprathermal particles, VHF/UHF EMI levels, and the S-band field strength.

Shawhan, S. D.↗
NASA NTRS1984

Fiberoptics for propulsion control system

In aircraft systems with digital controls, fiberoptics has advantages over wire systems because of its inherent immunity to electromagnetic noise (EMI) and electromagnetic pulses (EMP). It also offers a weight benefit when metallic conductors are replaced by optical fibers. To take full advantage of the benefits of optical waveguides, passive optical sensors are also being developed to eliminate the need for electrical power to the sensor. Fiberoptics may also be used for controlling actuators on engine and airframe. In this application, the optical fibers, connectors, etc. will be subjected to high temperature and vibrations. This paper discussed the use of fiberoptics in aircraft propulsion systems together with the optical sensors and optically controlled actuators being developed to take full advantage of the benefits which fiberoptics offers. The requirements for sensors and actuators in advanced propulsion systems are identified. The benefits of using fiberoptics in place of conventional wire systems are discussed as well as the environmental conditions under which the optical components must operate.

Baumbick, R. J.↗
NASA NTRS1984

Upset susceptibility study employing circuit analysis and digital simulation

This paper describes an approach to predicting the susceptibility of digital systems to signal disturbances. Electrical disturbances on a digital system's input and output lines can be induced by activities and conditions including static electricity, lightning discharge, Electromagnetic Interference (EMI) and Electromagnetic Pulsation (EMP). The electrical signal disturbances employed for the susceptibility study were limited to nondestructive levels, i.e., the system does not sustain partial or total physical damage and reset and/or reload will bring the system to an operational status. The front-end transition from the electrical disturbances to the equivalent digital signals was accomplished by computer-aided circuit analysis. The Super-Sceptre (system for circuit evaluation of transient radiation effects) Program was used. Gate models were developed according to manufacturers' performance specifications and parameters resulting from construction processes characteristic of the technology. Digital simulation at the gate and functional level was employed to determine the impact of the abnormal signals on system performance and to study the propagation characteristics of these signals through the system architecture. Example results are included for an Intel 8080 processor configuration.

Carreno, V. A.↗
NASA NTRS1984

Definition, analysis and development of an optical data distribution network for integrated avionics and control systems. Part 2: Component development and system integration

Fiber optic transmission is emerging as an attractive concept in data distribution onboard civil aircraft. Development of an Optical Data Distribution Network for Integrated Avionics and Control Systems for commercial aircraft will provide a data distribution network that gives freedom from EMI-RFI and ground loop problems, eliminates crosstalk and short circuits, provides protection and immunity from lightning induced transients and give a large bandwidth data transmission capability. In addition there is a potential for significantly reducing the weight and increasing the reliability over conventional data distribution networks. Wavelength Division Multiplexing (WDM) is a candidate method for data communication between the various avionic subsystems. With WDM all systems could conceptually communicate with each other without time sharing and requiring complicated coding schemes for each computer and subsystem to recognize a message. However, the state of the art of optical technology limits the application of fiber optics in advanced integrated avionics and control systems. Therefore, it is necessary to address the architecture for a fiber optics data distribution system for integrated avionics and control systems as well as develop prototype components and systems.

Yen, H. W.↗
NASA NTRS1984

Measurements of electromagnetic interference on OV102 Columbia using the plasma diagnostics package

The third Space Shuttle mission's OSS-1 payload included 30 Hz-800 MHz and S-band receivers which assessed the intentional (transmitter) and unintentional (subsystem) EMI levels. It was noted that, at the pallet location, the UHF voice downlink transmitter field strengths did not exceed 0.1 V/m. At the remote manipulator system, the figure was 0.5 V/m. Below 300 kHz, the magnetic field noise was 30 dB pT + or - 20 dB, while the electric field noise was broadband and variable over at least 60 dB, depending on thruster firings and Orbiter attitude. This noise may have been generated by the Orbiter's interaction with the ambient plasma.

Shawhan, S. D.↗
NASA NTRS1984

Upset susceptibility study employing circuit analysis and digital simulation

An approach to predict the susceptibility of digital systems to signal disturbances is described. Electrical disturbances on a digital system's input and output lines can be induced by activities and conditions including static electricity, lightning discharge, electromagnetic interference (EMI), and electromagnetic pulsation (EMP). The electrical signal disturbances employed for the susceptibility study were limited to nondestructive levels, i.e., the system does not sustain partial or total physical damage and reset and/or reload brings the system to an operational status. The front-end transition from the electrical disturbances to the equivalent digital signals was accomplished by computer-aided circuit analysis. The super-sceptre (system for circuit evaluation of transient radiation effects) programs was used. Gate models were developed according to manufacturers' performance specifications and parameters resulting from construction processes characteristic of the technology. Digital simulation at the gate and functional level was employed to determine the impact of the abnormal signals on system performance and to study the propagation characteristics of these signals through the system architecture. Example results are included for an Intel 8080 processor configuration.

Carreno, V. A.↗
NASA NTRS1983

Monolithic short wave infrared (SWIR) detector array

A monolithic self-scanned linear detector array was developed for remote sensing in the 1.1- 2.4-micron spectral region. A high-density IRCCD test chip was fabricated to verify new design approaches required for the detector array. The driving factors in the Schottky barrier IRCCD (Pdsub2Si) process development are the attainment of detector yield, uniformity, adequate quantum efficiency, and lowest possible dark current consistent with radiometric accuracy. A dual-band module was designed that consists of two linear detector arrays. The sensor architecture places the floating diffusion output structure in the middle of the chip, away from the butt edges. A focal plane package was conceptualized and includes a polycrystalline silicon substrate carrying a two-layer, thick-film interconnecting conductor pattern and five epoxy-mounted modules. A polycrystalline silicon cover encloses the modules and bond wires, and serves as a radiation and EMI shield, thermal conductor, and contamination seal.

Source record↗
NASA NTRS1986

Description of a 20 Kilohertz power distribution system

A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution link; mulitphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

Hansen, I. G.↗
NASA NTRS1985

Fiber optics for propulsion control systems

In aircraft systems with digital controls, fiberoptics has advantages over wire systems because of its inherent immunity to electromagnetic noise (EMI) and electromagnetic pulses (EMP). It also offers a weight benefit when metallic conductors are replaced by optical fibers. To take full advantage of the benefits of optical waveguides, passive optical sensors are also being developed to eliminate the need for electrical power to the sensor. Fiberoptics may also be used for controlling actuators on engine and airframe. In this application, the optical fibers, connectors, etc. will be subjected to high temperature and vibrations. This paper discussed the use of fiberoptics in aircraft propulsion systems together with the optical sensors and optically controlled actuators being developed to take full advantage of the benefits which fiberoptics offers. The requirements for sensors and actuators in advanced propulsion systems are identified. The benefits of using fiberoptics in place of conventional wire systems are discussed as well as the environmental conditions under which the optical components must operate.

Baumbick, R. J.↗
NASA NTRS1985

Shuttle environment database

The proceedings of a workshop on the development of a data base for the Space Shuttle environment are summarized. The data base is intended for use by experimenters in designing scientific payloads for Shuttle missions. The status of currently available data on the Shuttle environment is reviewed, with emphasis given to ten specific topics which are believed to be of concern to Shuttle experiment designers. These topics include: flight dynamics, vibration and acoustics, orbiter motion effects, EMI, and thermal and humidity effects. Attention is also given to: the Shuttle particulate environment; surface interactions inside and on the exterior of the spacecraft, and the natural Shuttle environment. Recent experimental results concerning Vehicle Glow on the spacecraft surface material are discussed in detail. A schematic diagram describing the functional organization of computer hardware for the Shuttle environment data base is provided.

Lauriente, M.↗
NASA NTRS1987

G-300: The first French Getaway Special microgravity measurements of fluid thermal conductivity

Thermal conductivity measurements on liquids are difficult to perform on Earth because of thermal motions due to convection. In microgravity, the convection due to buoyancy is evanescent, and a strong reduction of Rayleigh and Nusselt numbers can be expected. Three low viscosity liquids are selected to carry out the measurements; distilled water (standard) and two silicone oils. A modified hot plate method with a simplified guard ring is used; the reduction of convective motions permitted the use in the experimental cells of larger interplate distances and/or temperature differences than in Earth measurements, improving the accuracy. Comparisons between Earth and orbit results may help to understand the convection occurrence in the cells. Thermal, vibrational, and EMI tests have proved that the design satisfies the NASA requirements.

Perron, J. C.↗