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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 NTRS1992

Electron-impact vibrational relaxation in high-temperature nitrogen

Vibrational relaxation process of N2 molecules by electron-impact is examined for the future planetary entry environments. Multiple-quantum transitions from excited states to higher/lower states are considered for the electronic ground state of the nitrogen molecule N2 (X 1Sigma-g(+)). Vibrational excitation and deexcitation rate coefficients obtained by computational quantum chemistry are incorporated into the 'diffusion model' to evaluate the time variations of vibrational number densities of each energy state and total vibrational energy. Results show a non-Boltzmann distribution of number densities at the earlier stage of relaxation, which in turn suppresses the equilibrium process but affects little the time variation of total vibrational energy. An approximate rate equation and a corresponding relaxation time from the excited states, compatible with the system of flow conservation equations, are derived. The relaxation time from the excited states indicates the weak dependency of the initial vibrational temperature. The empirical curve-fit formula for the improved e-V relaxation time is obtained.

Lee, Jong-Hun↗
NASA NTRSDate not supplied

800 °C Demonstrated kHz SiC IC Electronics and Pressure Sensors as Technical Foundation for Realizing MHz DARPA HOTS Goals

The HOTS program will develop a technology for high-bandwidth, high-dynamic-range sensing at high temperature. Performance will be validated through the development and demonstration of a pressure sensor module (i.e., integrated transducer and signal-conditioning microelectronics) achieving the following performance goals: NASA Glenn has unique technology experience in extreme environment pressure sensors & IC electronics, including at 800 °C in air, providing significant risk reduction in meeting DARPA HOTS goals. Appropriate partnership and tech transfer should accelerate realization of DARPA HOTS hard technical challenges.

SiC pressure sensor electronics high temperature↗
NASA NTRS2011

Performance of the Micropower Voltage Reference ADR3430 Under Extreme Temperatures

Electronic systems designed for use in space exploration systems are expected to be exposed to harsh temperatures. For example, operation at cryogenic temperatures is anticipated in space missions such as polar craters of the moon (-223 C), James Webb Space Telescope (-236 C), Mars (-140 C), Europa (-223 C), Titan (-178 C), and other deep space probes away from the sun. Similarly, rovers and landers on the lunar surface, and deep space probes intended for the exploration of Venus are expected to encounter high temperature extremes. Electronics capable of operation under extreme temperatures would not only meet the requirements of future spacebased systems, but would also contribute to enhancing efficiency and improving reliability of these systems through the elimination of the thermal control elements that present electronics need for proper operation under the harsh environment of space. In this work, the performance of a micropower, high accuracy voltage reference was evaluated over a wide temperature range. The Analog Devices ADR3430 chip uses a patented voltage reference architecture to achieve high accuracy, low temperature coefficient, and low noise in a CMOS process [1]. The device combines two voltages of opposite temperature coefficients to create an output voltage that is almost independent of ambient temperature. It is rated for the industrial temperature range of -40 C to +125 C, and is ideal for use in low power precision data acquisition systems and in battery-powered devices. Table 1 shows some of the manufacturer s device specifications.

Patterson, Richard L.↗
NASA NTRS2004

Contraints on Solar Wind Plasma Properties Derived from Coordinated Coronal Observations

The goal of the proposed research was to increase the understanding of coronal plasma phenomena by making use of different observational approaches and combine the observations with the necessary theoretical considerations. During the funding period we studied the formation of spectral lines in the corona and transition region. We compared the spectral line ratios that would arise from the type of temperature profile commonly used to explain in situ ion fractions with the actual observed line ratios. We also carried out a theoretical study to investigate how large the electron temperatures can be in the near sun region. We carried out more detailed studies to show that differential flow speeds between ions of the same element can not bridge the above gap between low coronal electron temperatures and high in situ ion fractions. To investigate the drift between core and halo in the electron distribution function, which is observed in situ in the solar wind, we developed the first solar wind model with two electron populations. It was found that the anomalous frictional forces acting on the halo electrons are the dominant factor inhibiting the core-halo drift in the East solar wind. We used kinetic modeling to investigate the Alfvenic turbulence in the extended corona. In these studies we also included the effects of proton heating.

Esser, Ruth↗
NASA NTRS1990

Solar activity variation of ionospheric plasma temperatures

The present status of understanding and modeling of the variation of electron and ion temperatures with solar activity is reviewed. All atmospheric and ionospheric densities and temperatures are positively correlated with solar activity except the electron temperature, which exhibits a rather complex variation pattern during a solar cycle. The ion temperature at low altitudes closely follows the variation patterns of the neutral temperature. The electron temperature at high altitudes increases with increasing solar activity; the increase is larger during day than during night and exhibits a latitudinal variation. At low altitudes during daytime, tha amplitude of the seasonal variation of the electron temperature increases toward the solar maximum. At 400 km during daytime, the summer electron temperatures for Millstone Hill increase slightly toward higher solar activities, whereas the winter temperatures decrease distinctly. For Arecibo, an opposite trend is noticeable.

Bilitza, D.↗
NASA NTRS1982

Trichite growth during oxidation of titanium and TA6V4 alloy by water vapor at high temperatures

Analysis by electron scanning microscope detected the formation of rutile trichites on the surface of specimens of titanium and titanium alloy TA6V4 oxidized in water vapor in the temperature range 650 to 950 C and the water vapor pressure range from 0.5 to 18 torr. In all specimens, two sublayers of rutile were formed: an external layer of basalt-like appearance, and a microcrystalline inner layer. Morphology of the trichites depends on temperature and the material (whether metal or alloy), but not on vapor pressure.

Coddet, C.↗
NASA NTRS2007

An Overview of Wide Bandgap Silicon Carbide Sensors and Electronics Development at NASA Glenn Research Center

A brief overview is presented of the sensors and electronics development work ongoing at NASA Glenn Research Center which is intended to meet the needs of future aerospace applications. Three major technology areas are discussed: 1) high temperature SiC electronics, 2) SiC gas sensor technology development, and 3) packaging of harsh environment devices. Highlights of this work include world-record operation of SiC electronic devices including 500?C JFET transistor operation with excellent properties, atomically flat SiC gas sensors integrated with an on-chip temperature detector/heater, and operation of a packaged AC amplifier. A description of the state-of-the-art is given for each topic. It is concluded that significant progress has been made and that given recent advancements the development of high temperature smart sensors is envisioned.

Hunter, Gary W.↗
NASA NTRS2004

Communications Transceivers for Venus Surface Missions

The high temperature of the surface of Venus poses many difficulties. Previous Venus landers have only operated for short durations before succumbing to the heat. NASA Glenn Research Center conducted a study on communications for long duration Venus surface missions. I report the findings in this presentation. Current technology allows production of communications transceivers that can operate on the surface of Venus, at temperatures above 450 C and pressures of over 90 atmospheres. While these transceivers would have to be relatively simple, without much of the advanced signal processing often used in modern transceivers, since current and near future integrated circuits cannot operate at such high temperatures, the transceivers will be able to meet the requirements of proposed Venus Surface mission. The communication bands of interest are High Frequency or Very High Frequency (HFNHF) for communication between Venus surface and airborne probes (including surface to surface and air to air), and Ultra High Frequency (UHF) to Microwave bands for communication to orbiters. For HFNHF, transceivers could use existing vacuum tube technology. The packaging of the vacuum tubes may need modification, but the internal operating structure already operates at high temperatures. Using metal vacuum structures instead of glass, allows operation at high pressure. Wide bandgap transistors and diodes may be able to replace some of the thermionic components. VHF communications would be useful for line-of- sight operations, while HF would be useful for short-wave type communications using the Venusian ionosphere. UHF and microwave communications use magnetically focused thermionic devices, such as traveling wave tubes (TWTs), magnetron (M-type) amplifiers, and klystrons for high power amplifiers, and backward wave oscillators (BWOs) and reflex klystrons for oscillators. Permanent magnets are already in use in industry that can operate at 500 C. These magnets could focus electron beam tubes on the surface of Venus. While microwave windows will need to be designed for the high pressure, diamond windows have already been demonstrated, so high-pressure microwave windows can be designed and built. Thus, all of these devices could be useful for Venus surface missions. Current electronic power conditioners to supply the high voltages used in these microwave devices cannot operate at high temperatures, but earlier electronic power conditioners that used vacuum tubes can be modified to work at high temperature. Evaluating the various devices in this study, the M-type traveling wave tube (where a traveling wave structure is used in a crossed-field device, similar to the Amplitron used on the Apollo missions) stood out for the high power amplifier since it requires a single high voltage, simplifying the power supply design. Since the receiver amplifier is a low power amplifier, the loss of efficiency in linear beam devices without a depressed collector (and thus needing a single high voltage) is not important; a low noise TWT is a possible solution. Before solid-state microwave amplifiers were available, such TWTs were built with a 1-2 dB noise figure. A microwave triode or transistor made from a wide bandgap material may be preferable, if available. Much of the development work needed for Venusian communication devices will need to focus on the packaging of the devices, and their connections, but the technology is available to build transceivers that can operate on the surface of Venus indefinitely.

Force, Dale A.↗
NASA NTRS1993

Radiation and temperature effects on electronic components investigated under the CSTI high capacity power project

The effects of nuclear radiation and high temperature environments must be fully known and understood for the electronic components and materials used in both the Power Conditioning and Control subsystem and the reactor Instrumentation and Control subsystem of future high capacity nuclear space power systems. This knowledge is required by the designer of these subsystems in order to develop highly reliable, long-life power systems for future NASA missions. A review and summary of the experimental results obtained for the electronic components and materials investigated under the power management element of the Civilian Space Technology Initiative (CSTI) high capacity power project are presented: (1) neutron, gamma ray, and temperature effects on power semiconductor switches, (2) temperature and frequency effects on soft magnetic materials; and (3) temperature effects on rare earth permanent magnets.

Schwarze, Gene E.↗
NASA NTRS1993

Fabrication of photovoltaic laser energy converterby MBE

A laser-energy converter, fabricated by molecular beam epitaxy (MBE), was developed. This converter is a stack of vertical p-n junctions connected in series by low-resistivity, lattice matched CoSi2 layers to achieve a high conversion efficiency. Special high-temperature electron-beam (e-beam) sources were developed especially for the MBE growth of the junctions and CoSi2 layers. Making use of the small (greater than 1.2 percent) lattice mismatch between CoSi2 and Si layers, high-quality and pinhole-free epilayers were achieved, providing a capability of fabricating all the junctions and connecting layers as a single growth process with one pumpdown. Well-defined multiple p-n junctions connected by CoSi2 layers were accomplished by employing a low growth temperature (greater than 700 C) and a low growth rate (less than 0.5 microns/hour). Producing negligible interdiffusion, the low growth temperature and rate also produced negligible pinholes in the CoSi2 layers. For the first time, a stack of three p-n junctions connected by two 10(exp -5) Ohm-cm CoSi2 layers was achieved, meeting the high conversion efficiency requirement. This process can now be optimized for high growth rate to form a practical converter with 10 p-n junctions in the stack.

Lu, Hamilton↗
NASA NTRS2011

Assessment of Durable SiC JFET Technology for +600 C to -125 C Integrated Circuit Operation

Electrical characteristics and circuit design considerations for prototype 6H-SiC JFET integrated circuits (ICs) operating over the broad temperature range of -125 C to +600 C are described. Strategic implementation of circuits with transistors and resistors in the same 6H-SiC n-channel layer enabled ICs with nearly temperature-independent functionality to be achieved. The frequency performance of the circuits declined at temperatures increasingly below or above room temperature, roughly corresponding to the change in 6H-SiC n-channel resistance arising from incomplete carrier ionization at low temperature and decreased electron mobility at high temperature. In addition to very broad temperature functionality, these simple digital and analog demonstration integrated circuits successfully operated with little change in functional characteristics over the course of thousands of hours at 500 C before experiencing interconnect-related failures. With appropriate further development, these initial results establish a new technology foundation for realizing durable 500 C ICs for combustion engine sensing and control, deep-well drilling, and other harsh-environment applications.

Neudeck, P. G.↗
NASA NTRS2013

Extreme Environment Capable, Modular and Scalable Power Processing Unit for Solar Electric Propulsion

This paper is to present a concept of a modular and scalable High Temperature Boost (HTB) Power Processing Unit (PPU) capable of operating at temperatures beyond the standard military temperature range. The various extreme environments technologies are also described as the fundamental technology path to this concept. The proposed HTB PPU is intended for power processing in the area of space solar electric propulsion, where the reduction of in-space mass and volume are desired, and sometimes even critical, to achieve the goals of future space flight missions. The concept of the HTB PPU can also be applied to other extreme environment applications, such as geothermal and petroleum deep-well drilling, where higher temperature operation is required.

Electronics↗
NASA NTRS2005

500(deg)C electronics for harsh environments

Solid state vacuum devices (SSVDs) are a relatively new class of electronic devices. Innosys is a leading producer of high frequency SSVDs for a number of applications, including RF communications. SSVDs combine features inherent to both solid state and vacuum transistors. Electron transport can be by solid state or vacuum or both. The focus of this talk is on thermionic SSVDs, in which the primary vacuum transport is by thermionically liberated electron emission.

high temperature electronics↗
NASA NTRS1999

Silicon Carbide Being Developed for High-Definition Television (HDTV) Transmitter Modules

Through a Space Act Agreement, the NASA Lewis Research Center has helped develop the base silicon carbide (SiC) epitaxial growth technology for Westinghouse's efforts to bring silicon carbide products to the marketplace. SiC is a high-temperature, high-voltage semiconductor that can deliver greater than three times the power of conventional silicon devices. The technology was initially disclosed in the 1994 R&T report. NASA Lewis High Temperature Integrated Electronics and Sensors (HTIES) team is developing SiC as a material for advanced semiconductor electronic device applications because SiC-based electronics and sensors can operate in hostile environments where conventional silicon-based electronics cannot function. SiC transmitters hold great promise for television stations because they can convert broadcasts from analog to digital signals. A modular solid-state design provides broadcasters with an option to gradually add modules, increasing the power of their transmitters as they expand their high-definition television (HDTV) coverage. Using these high-power transistors will significantly reduce the space needed for high-power transmitters at television stations and will offer a solid-state solution, reducing long-term maintenance costs. Thus, transmitter manufacturers will be able to abandon their reliance on tube-based technology for high-power transmitters and will be able to build smaller, high-power, solid-state transmitters.

Costello, Donald E.↗
NASA NTRS2013

The Need and Challenges for Distributed Engine Control

The presentation describes the challenges facing the turbine engine control system. These challenges are primarily driven by a dependence on commercial electronics and an increasingly severe environment on board the turbine engine. The need for distributed control is driven by the need to overcome these system constraints and develop a new growth path for control technology and, as a result, improved turbine engine performance.

Distributed control↗