Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Current regulation”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

User type certification for advanced flight control systems

Advanced avionics through flight management systems (FMS) coupled with autopilots can now precisely control aircraft from takeoff to landing. Clearly, this has been the most important improvement in aircraft since the jet engine. Regardless of the eventual capabilities of this technology, it is doubtful that society will soon accept pilotless airliners with the same aplomb they accept driverless passenger trains. Flight crews are still needed to deal with inputing clearances, taxiing, in-flight rerouting, unexpected weather decisions, and emergencies; yet it is well known that the contribution of human errors far exceed those of current hardware or software systems. Thus human errors remain, and are even increasing in percentage as the largest contributor to total system error. Currently, the flight crew is regulated by a layered system of certification: by operation, e.g., airline transport pilot versus private pilot; by category, e.g., airplane versus helicopter; by class, e.g., single engine land versus multi-engine land; and by type (for larger aircraft and jet powered aircraft), e.g., Boeing 767 or Airbus A320. Nothing in the certification process now requires an in-depth proficiency with specific types of avionics systems despite their prominent role in aircraft control and guidance.

Gilson, Richard D.↗
NASA NTRS1997

Certification of a Modified Research Public Aircraft

NASA Ames Research Center has several aircraft that have been modified to conduct aeronautical and scientific research. NASA's purpose is to provide research to improve safety of flight and support scientific research for Mission to Planet Earth. Our research and platform aircraft have been modified to fit the needs of the scientific and research programs. Because NASA's aircraft have been modified and operated as public aircraft, certification of airworthiness on many are not current. Some of our aircraft are military aircraft and were never certificated. This paper discusses the process of bringing a modified B200 King Air aircraft certification current to meet Federal Aviation Regulations.

Forsyth, T. J.↗
NASA NTRS2003

Depth and Distribution of CO2 Snow on Mars

The dynamic role of volatiles on the surface of Mars has been a subject of longstanding interest. In the pre-Viking era, much of the debate was necessarily addressed by theoretical considerations. A particularly influential treatment by Leighton and Murray put forth a simple model relying on solar energy balance, and led to the conclusion that the most prominent volatile exchanging with the atmosphere over seasonal cycles is carbon dioxide. Their model suggested that due to this exchange, atmospheric CO2 partial pressure is regulated by polar ice. While current thinking attributes a larger role to H2O ice than did the occasional thin polar coating this model predicted, the CO2 cycle appears to be essentially correct. There are a number of observational constraints on the seasonal exchange of surface volatiles with the atmosphere. The growth and retreat of polar CO2 frost is visible from Earth-based telescopes and from spacecraft in Mars orbit, both at visible wavelengths and in thermal IR properties of the surface. Recently, variations in Gamma ray and neutron fluxes have also been used to infer integrated changes in CO2 mass on the surface. Measurements made by Viking's Mars Atmospheric Water Detector experiment were sensitive to atmospheric H2O vapor abundance. Surface condensates and their transient nature were detected by the Viking landers. The study here is motivated by recent data collected by the Mars Global Surveyor, affording the opportunity to not only detect the lateral distribution of volatiles, but also to constrain the variable volumes of the reservoirs. We elaborate on a technique first employed by Smith et al. By examining averages of a large number of topographic measurements collected by the Mars Orbiter Laser Altimeter (MOLA), that study showed that the zonal pattern of deposition and sublimation of CO2 can be determined. In their first approach, reference surfaces were fit to all measurements in narrow latitude annuli, and the time dependent variations about those mean surfaces were examined. In their second approach, height measurements from pairs of tracks that cross on the surface were interpolated and differenced, forming a set of crossover residuals. These residuals were then examined as a function of time and latitude. The initial studies averaged over longitude to maximize signal and minimize noise in order to isolate the expected small signal. In this follow-up study we now attempt to extract the elevation change pattern also as a function of longitude, and we focus on the crossover approach.

Aharonson, Oded↗
NASA NTRS1980

Minimizing spikes in switching-regulator circuits

Circuit, employing tapped inductor to back-bias rectifying diodes and extra diode to cummutate current, minimizes current spikes that cause premature transistor failure in switching-regulator circuits.

Mclyman, W. T.↗
NASA NTRS2020

HSYE-117RH Voltage Linear Regulator Total Ionizing Dose Test Report

The purpose of this test was to validate the Intersil HSYE-117RH-Q flight lot for use in the fabrication of Europa Clipper Propulsion subsystem flight hardware. This test shall serve as the radiation lot acceptance test (RLAT) for the flight lot date with wafer lot number G3X3CQC and lot date code (LDC) 1830. Low dose rate (LDR) irradiations have been performed by the manufacturer, but only to 100 krad(Si). This test was a follow-on to the original Radiation Lot-Specific Acceptance Testing (RLAT) performed on this LDC. Application-specific load currents were used for the line regulation and load regulation measurements. All other parameters were measured with standard bias conditions as specified in the datasheet.

Total Ionizing Dose (TID)↗
NASA NTRS2015

Toward Edge-Defined Holey Boron Nitride Nanosheets

"Holey" two-dimensional (2D) nanosheets with well-defined holy morphology and edge chemistry are highly desirable for applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. For example, holey grapheme is currently under extensive investigation for energy storage applications because of the improvement in ion transport due to through the thickness pathways provided by the holes. Without the holes, the 2D materials have significant limitations for such applications in which efficient ion transport is important. As part of an effort to apply this approach to other 2D nanomaterials, a method to etch geometrically defined pits or holes on the basal plane surface of hexagonal boron nitride (h-BN) nanosheets has been developed. The etching, conducted via heating in ambient air using metal nanoparticles as catalysts, was facile, controllable, and scalable. Starting h-BN layered crystals were etched and subsequently exfoliated into boron nitride nanosheets (BNNSs). The as-etched and exfoliated h-BN nanosheets possessed defined pit and hole shapes that were comprised of regulated nanostructures at the edges. The current finding are the first step toward the bulk preparation of holey BNNSs with defined holes and edges.

Lin, Yi↗
NASA NTRS1989

Cascaded resonant bridge converters

A converter for converting a low voltage direct current power source to a higher voltage, high frequency alternating current output for use in an electrical system where it is desired to use low weight cables and other circuit elements. The converter has a first stage series resonant (Schwarz) converter which converts the direct current power source to an alternating current by means of switching elements that are operated by a variable frequency voltage regulator, a transformer to step up the voltage of the alternating current, and a rectifier bridge to convert the alternating current to a direct current first stage output. The converter further has a second stage series resonant (Schwarz) converter which is connected in series to the first stage converter to receive its direct current output and convert it to a second stage high frequency alternating current output by means of switching elements that are operated by a fixed frequency oscillator. The voltage of the second stage output is controlled at a relatively constant value by controlling the first stage output voltage, which is accomplished by controlling the frequency of the first stage variable frequency voltage controller in response to second stage voltage. Fault tolerance in the event of a load short circuit is provided by making the operation of the first stage variable frequency voltage controller responsive to first and second stage current limiting devices. The second stage output is connected to a rectifier bridge whose output is connected to the input of the second stage to provide good regulation of output voltage wave form at low system loads.

Stuart, Thomas A.↗
NASA NTRS2003

Flow-dependent regulation of endothelial nitric oxide synthase: role of protein kinases

Vascular endothelial cells are directly and continuously exposed to fluid shear stress generated by blood flow. Shear stress regulates endothelial structure and function by controlling expression of mechanosensitive genes and production of vasoactive factors such as nitric oxide (NO). Though it is well known that shear stress stimulates NO production from endothelial nitric oxide synthase (eNOS), the underlying molecular mechanisms remain unclear and controversial. Shear-induced production of NO involves Ca2+/calmodulin-independent mechanisms, including phosphorylation of eNOS at several sites and its interaction with other proteins, including caveolin and heat shock protein-90. There have been conflicting results as to which protein kinases-protein kinase A, protein kinase B (Akt), other Ser/Thr protein kinases, or tyrosine kinases-are responsible for shear-dependent eNOS regulation. The functional significance of each phosphorylation site is still unclear. We have attempted to summarize the current status of understanding in shear-dependent eNOS regulation.

Non-NASA Center↗
NASA NTRS1969

Magnetically coupled emission regulator

Magnetic coupling between input and power handling circuits isolates high voltage. A feedback regulator samples the ion source bias current and provides deviation signals to a magnetic amplifier pulse modulator. The pulse modulator controls the dc to ac power inverter which in turn, controls the emission current.

Source record↗
NASA NTRS1972

Solar bus regulator and battery charger for IMP's H, I, and J

Interplanetary Monitoring Probe (IMP) spacecrafts H, I, and J utilize a direct energy transfer (DET) type of power system operating from a solar array source. A shunt type of regulator prevents the bus voltage from exceeding a preset voltage level. The power system utilizes a single differential amplifier with dual outputs to control the battery charge/shunt regulator and the discharge regulator. A two-voltage level, current limited, series charger and a current sensor control battery state of charge of the silver-cadmium battery pack. Premature termination of the battery charge is prevented by a power available gate that also initiates charge current to the battery upon availability of excess power.

Paulkovich, J.↗
NASA NTRS1985

Automatic Monitoring of Switching Power Supplies

Fast analysis of switching waveforms allows detection of impending failures. Switching power conditioner converts dc power from source such as battery or solar cell array to well regulated dc at convenient voltages and currents. Concept originally developed for space stations and spacecraft also suitable for power conditioning equipment in aircraft and in terrestrial photovoltaic power systems.

Moser, R. L.↗
NASA NTRS1985

Continuous laminar smoke generator

A smoke generator capable of emitting a very thin, laminar stream of smoke for use in high detail flow visualization was invented. The generator is capable of emitting a larger but less stable rope of smoke. The invention consists of a pressure supply and fluid supply which supply smoke generating fluid to feed. The feed tube is directly heated by electrical resistance from current supplied by power supply and regulated by a constant temperature controller. A smoke exit hole is drilled in the wall of feed tube. Because feed tube is heated both before and past exit hole, no condensation of smoke generating occurs at the smoke exit hole, enabling the production of a very stable smoke filament. The generator is small in size which avoids wind turbulence in front of the test model.

Weinstein, L. M.↗
NASA NTRS2010

Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

Patterson, Richard↗
NASA NTRS2013

Simulator Study of Indoor Annoyance Caused by Shaped Sonic Boom Stimuli With and Without Rattle Augmentation

The National Aeronautics and Space Administration's High Speed Project is developing a predictive capability for annoyance caused by shaped sonic booms transmitted indoors. The predictive capability is intended for use by aircraft designers as well as by aircraft noise regulators who are considering lifting the current prohibition on overland civil supersonic flight. The goal of the current study is to use an indoor simulator to validate two models developed using headphone tests for annoyance caused by sonic booms with and without rattle augmentation. The predictors in the proposed models include Moore and Glasberg's Stationary Loudness Level, the time derivative of Moore and Glasberg's time-varying short-term Loudness Level, and the difference between two weighted sound exposure levels, CSEL-ASEL. The indoor simulator provides a more realistic listening environment than headphones due to lowfrequency sound reproduction down to 6 Hz, which also causes perceptible tactile vibration. The results of this study show that a model consisting of {PL + (CSEL-ASEL)} is a reliable predictor of annoyance caused by shaped sonic booms alone, rattle sounds alone, and shaped sonic booms and rattle sounds together.

Rathsam, Jonathan↗
NASA NTRS2015

Dynamic Open-Rotor Composite Shield Impact Test Report

The Federal Aviation Administration (FAA) is working with the European Aviation Safety Agency to determine the certification base for proposed new engines that would not have a containment structure on large commercial aircraft. Equivalent safety to the current fleet is desired by the regulators, which means that loss of a single fan blade will not cause hazard to the aircraft. NASA Glenn and Naval Air Warfare Center (NAWC) China Lake collaborated with the FAA Aircraft Catastrophic Failure Prevention Program to design and test a shield that would protect the aircraft passengers and critical systems from a released blade that could impact the fuselage. This report documents the live-fire test from a full-scale rig at NAWC China Lake. NASA provided manpower and photogrammetry expertise to document the impact and damage to the shields. The test was successful: the blade was stopped from penetrating the shield, which validates the design analysis method and the parameters used in the analysis. Additional work is required to implement the shielding into the aircraft.

Shielding↗
NASA NTRS2015

Analysis and Testing of a Composite Fuselage Shield for Open Rotor Engine Blade-Out Protection

The Federal Aviation Administration is working with the European Aviation Safety Agency to determine the certification base for proposed new engines that would not have a containment structure on large commercial aircraft. Equivalent safety to the current fleet is desired by the regulators, which means that loss of a single fan blade will not cause hazard to the Aircraft. The NASA Glenn Research Center and The Naval Air Warfare Center (NAWC), China Lake, collaborated with the FAA Aircraft Catastrophic Failure Prevention Program to design and test lightweight composite shields for protection of the aircraft passengers and critical systems from a released blade that could impact the fuselage. In the test, two composite blades were pyrotechnically released from a running engine, each impacting a composite shield with a different thickness. The thinner shield was penetrated by the blade and the thicker shield prevented penetration. This was consistent with pre-test predictions. This paper documents the live fire test from the full scale rig at NAWC China Lake and describes the damage to the shields as well as instrumentation results.

safety↗
NASA NTRS2016

Analysis and Testing of a Composite Fuselage Shield for Open Rotor Engine Blade-Out Protection

The Federal Aviation Administration is working with the European Aviation Safety Agency to determine the certification base for proposed new engines that would not have a containment structure on large commercial aircraft. Equivalent safety to the current fleet is desired by the regulators, which means that loss of a single fan blade will not cause hazard to the Aircraft. The NASA Glenn Research Center and The Naval Air Warfare Center (NAWC), China Lake, collaborated with the FAA Aircraft Catastrophic Failure Prevention Program to design and test lightweight composite shields for protection of the aircraft passengers and critical systems from a released blade that could impact the fuselage. LS-DYNA® was used to predict the thickness of the composite shield required to prevent blade penetration. In the test, two composite blades were pyrotechnically released from a running engine, each impacting a composite shield with a different thickness. The thinner shield was penetrated by the blade and the thicker shield prevented penetration. This was consistent with pre-test LS-DYNA predictions. This paper documents the analysis conducted to predict the required thickness of a composite shield, the live fire test from the full scale rig at NAWC China Lake and describes the damage to the shields as well as instrumentation results.

Composite↗