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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The effects of lightning on digital flight control systems

Present practices in lightning protection of aircraft deal primarily with the direct effects of lightning, such as structural damage and ignition of fuel vapors. There is increasing evidence of troublesome electromagnetic effects, however, in aircraft employing solid-state microelectronics in critical navigation, instrumentation and control functions. The potential impact of these indirect effects on critical systems such as digital fly-by-wire (DFBW) flight controls has been studied by several recent research programs, including an experimental study of lightning-induced voltages in the NASA F8 DFBW airplane. The results indicate a need for positive steps to be taken during the design of future fly-by-wire systems to minimize the possibility of hazardous effects from lightning.

Plumer, J. A.↗
NASA NTRS1976

The effects of lightning on digital flight control systems

Present practices in lightning protection of aircraft deal primarily with the direct effects of lightning, such as structural damage and ignition of fuel vapors. There is increasing evidence of troublesome electromagnetic effects, however, in aircraft employing solid-state microelectronics in critical navigation, instrumentation and control functions. The potential impact of these indirect effects on critical systems such as digital fly by wire (DFBW) flight controls was studied. The results indicate a need for positive steps to be taken during the design of future fly by wire systems to minimize the possibility of hazardous effects from lightning.

Plumer, J. A.↗
NASA NTRS1986

A design study for the use of a multiple aperture deployable antenna for soil moisture remote sensing satellite applications

The instrumentation problems associated with the measurement of soil moisture with a meaningful spatial and temperature resolution at a global scale are addressed. For this goal only medium term available affordable technology will be considered. The study while limited in scope, will utilize a large scale antenna structure, which is being developed presently as an experimental model. The interface constraints presented by a singel Space Transportation System (STS) flight will be assumed. Methodology consists of the following steps: review of science requirements; analyze effects of these requirements; present basic system engineering considerations and trade-offs related to orbit parameters, number of spacecraft and their lifetime, observation angles, beamwidth, crossover and swath, coverage percentage, beam quality and resolution, instrument quantities, and integration time; bracket the key system characteristics and develop an electromagnetic design of the antenna-passive radiometer system. Several aperture division combinations and feed array concepts are investigated to achieve maximum feasible performacne within the stated STS constraints.

Foldes, P.↗
NASA NTRS1988

Lightning initiation on aircraft in thunderstorms

The physical model of the initiation of lightning flashes by aircraft in thunderstorms is presented. The model is based on the 'bi-directional uncharged leader' concept by Kasemir, and is verified with airborne data from lightning strikes to an instrumented airplane (NASA F-106B and FAA CV-580). The characteristics of electromagnetic processes during lightning attachment are identified by comparison with those studied in natural flashes, those triggered by wire trailing rockets, and laboratory discharges. A triggered flash starts with either a negative corona or a positive leader that depends on the ambient electric field vector and the airplane form factor. The positive leader with continuous current that increases with time is followed in a few milliseconds by the negative stepped leader with current pulses of a few kA. The two leaders develop in space simultaneously and bi-directionally from the oppositely charged extremities of the airplane.

Mazur, Vladislav↗
NASA NTRS1988

Lightning initiation on aircraft in thunderstorms

A physical model of the initiation of lightning flashes in thunderstorms is presented. The model is based on the bi-directional charged leader concept of Kasemir, and is verified with airborne data from lightning strikes to instrumented airplanes (NASA F-106B and FAA CV-580). The characteristics of electromagnetic processes during lightning attachment are identified by comparison with those studied in natural flashes, those triggered by wire trailing rockets, and laboratory discharges. A triggered flash starts with either a negative corona or a positive leader that depends on the ambient electric field vector and the airplane form factor. The positive leader with continuous current that increases with time is followed in a few milliseconds by the negative stepped leader with current pulses of a few kA. The two leaders develop in space simultaneously and bi-directionally from the oppositely charged extremities of the airplane.

Mazur, Vladislav↗
NASA NTRS1994

The 1994 International Geoscience and Remote Sensing Symposium (IGARSS 1994)

The papers presented at the symposium focus on remote sensing, particularly on global monitoring of the earth with emphasis on the solution of environmental problems. Topics discussed include remote sensing of clouds and earth troposphere, sea ice remote sensing, optical remote sensing, land monitoring and thermal sensing, atmospheric sounding and monitoring, atmospheric correction, and satellite imaging data. Other subject areas are ecosystems and vegetation monitoring; ocean winds and surface scattering; ocean waves, currents and bathymetry; satellite oceanography; SAR for remote sensing; neural nets application to remote sensing; geographical information systems; and electromagnetic wave propagation. Also discussed environmental monitoring using ERS-1; Topex/Poseidon results; spaceborne instruments; image processing and classification algorithms; and future space missions.

Source record↗
NASA NTRS1989

Considerations for a Next Generation UV/Optical Space Telescope

During the past 25 years, a remarkable scientific revolution, has occurred in astrophysics as a result of convergence on two advancing fronts. First, instruments and telescopes have been developed to make sensitive measurements throughout the entire electromagnetic spectrum. Secondly, access to space has permitted observations above the obscuring and distorting "dirty window" of our atmosphere. Beginning around the middle of the next decade, a third major path - the availability of the permanently manned Space Station Freedom - will join with the earlier two capabilities, to not only continue this revolution, but to accelerate the quest for answers about the universe that have puzzled mankind for centuries. Beyond Earth-orbit, NASA is actively studying the possibility of a return to the Moon, which would provide a valuable platform for astrophysics observations during the next century. The studies discussed in this paper indicate that the technology requirements associated with the transportation to orbit and the assembly of these telescopes in orbit are major driving forces in the selection of generic design concepts. Ultimately, optical advances which are now becoming available through advanced manufacturing must be matched by technology advances in orbital operations, system modularization, and assembly by man and machine.

Nein, M. E.↗
NASA NTRS1999

Design Challenges of Power Systems for Instrumented Spacecraft with Very Low Perigees in the Earth's Ionosphere

Designing a solar array to power a spacecraft bus supporting a set of instruments making in situ plasma and neutral atmosphere measurements in the ionosphere at altitudes of 120km or lower poses several challenges. The driving scientific requirements are the field-of-view constraints of the instruments resulting in a three-axis stabilized spacecraft, the need for an electromagnetically unperturbed environment accomplished by designing an electrostatically conducting solar array surface to avoid large potentials, making the spacecraft body as small and as symmetric as possible, and body-mounting the solar array. Furthermore, the life and thermal constraints, in the midst of the effects of the dense atmosphere at low altitude, drive the cross-sectional area of the spacecraft to be small particularly normal to the ram direction. Widely varying sun angles and eclipse durations add further complications, as does the growing desire for multiple spacecraft to resolve spatial and temporal variations packaged into a single launch vehicle. Novel approaches to insure adequate orbit-averaged power levels of approximately 250W include an oval-shaped cross section to increase the solar array collecting area during noon-midnight orbits and the use of a flywheel energy storage system. The flywheel could also be used to help maintain the spacecraft's attitude, particularly during excursions to the lowest perigee altitudes. This paper discusses the approaches used in conceptual power designs for both the proposed Dipper and the Global Electrodynamics Connections (GEC) Mission currently being studied at the NASA/Goddard Space Flight Center.

Moran, Vickie Eakin↗
NASA NTRS2010

A Discovery-Class Lunette Mission Concept for a Lunar Geophysical Network

The Lunette mission concept for a network of small, inexpensive lunar landers has evolved over the last three years as the focus of space exploration activities in the US has changed. Originating in a concept for multiple landers launched as a secondary payload capable of regional science and site survey activities, Lunette has recently been developed into a Discovery-class mission concept that offers global lunar coverage enabling network science on a much broader scale. A particular mission concept has been refined by the Lunette team that would result in a low-cost global lunar geophysical network, comprised of two landers widely spaced on the near side of the moon. Each of the two identical landers would carry a suite of instruments that would make continuous measurements of seismic activity, heat flow, and the electromagnetic environment during the full lunar day/night cycle. Each lander would also deploy a next-generation laser retroreflector capable of improving on distance measurement accuracy by an order of magnitude over those emplaced by the previous Apollo and Lunokhod missions. This paper presents a comprehensive overview of the Lunette geophysical network mission concept, including mission and flight system design, as well as the key requirements and constraints that guided them.

Elliott, John↗
NASA NTRS2020

Parametric Cost Model for Ground and Space Telescopes

Parametric cost models can be used by designers and project managers to compare cost between major architectural cost drivers and allow high-level design trades; enable cost-benefit analysis for technology development investment; and, provide a basis for estimating total project cost between related concepts. The NASA Marshall Space Flight Center has developed a 5-parameter first-article optical telescope assembly cost model OTA$ (FY17) = $20M x 30(S/G)x D(1.7)x λ(-0.5)x T(-0.25)x e(-0.028) (Y-1960)Where S/G = 1 for space and 0 for ground telescopes, D = diameter, λ= diffraction limited wavelength, T = operating temperature and Y = year of development. The model explains 92% (Adjusted R2) of the cost variation in a database of 47 total ground and space telescope assemblies (OTA). The MSFC model estimates the most likely cost for only the OTA. Where an OTA is defined as the subsystem which collects electromagnetic radiation and focuses it (focal) or concentrates it (afocal) into the science instruments. An OTA consists of the primary mirror, secondary mirror, auxiliary optics and support structure (such as optical bench or truss structure, primary support structure, secondary support structure or spiders, straylight baffles, mechanisms for adjusting the optical components, electronics or power systems for operating these mechanisms, etc.). Finally, duplication only reduces cost for the manufacture of identical systems(i.e. multiple aperture sparse arrays or interferometers). And, while duplication does reduce the cost of manufacturing the mirrors of segmented primary mirror, this cost savings does not appear to manifest itself in the final primary mirror assembly(presumably because the structure for a segmented mirror is more complicated than for a monolithic mirror).

Space Telescope Cost Model, Parametric Cost Model↗
NASA NTRS1998

Magnetospheric Constellation and Tomography Mission Concept

We describe the basic principles, instrumentation, and feasibility of a multi-satellite mission that combines in situ observations of plasma and electromagnetic fields with radio tomography imaging. We show that a 16-satellite radio tomography experiment can produce two-dimensional images of plasma density in the earth's magnetosphere at sufficient spatial (1/2 R(sub E)) and temporal (approximately 10s) resolution to address key problems of magnetospheric physics. The same mission can incorporate electron and ion analyzers, magnetometers, and electric field instruments on the same spacecraft. We suggest that the large-scale images are more valuable when combined with in situ observations, supporting an unambiguous interpretation of the in situ data and an investigation of the interdependence of small- and large-scale plasma processes.

Ergun, R. E.↗
NASA NTRS1998

The Application of Beowulf-Class Computing to Computational Electromagnetics

Current computational developments at the Jet Propulsion Laboratory (JPL) are motivated by the NASA/JPL goal of reducing payload in future space missions while increasing mission capability through miniaturization of active and passive sensors, analytical instruments and communication systems.

beowulf-class↗
NASA NTRS1993

Optical properties and emissivities of liquid metals and alloys

This paper presents the results from our on-going program to investigate the optical properties of liquid metals and alloys at elevated temperatures. Ellipsometric and polarimetric techniques have been used to investigate the optical properties of materials in the 1000 - 3000 K temperature range and in the 0.3 - 0.1 mu m wavelength range. The ellipsometric and polarimetric techniques are described and the characteristics of the instruments are presented. The measurements are conducted by reflecting a polarized laser beam from an electromagnetically levitated liquid metal or alloy specimen. A Rotating Analyzer Ellipsometer (RAE) or a four-detector Division-of-Amplitude Photopolarimeter (DOAP) is used to determine the polarimetric properties of the light reflected at an angle of incidence of approximately 68 deg. Optical properties of the specimen which are calculated from these measurements include the index of refraction, extinction coefficient, normal spectral emissivity, and spectral hemispherical emissivity. These properties have been determined at various wavelengths and temperatures for liquid Ag, Al, Au, Cu, Nb, Ni, Pd, Pt, Si, Ti, Ti-Al alloys, U, and Zr. We also describe new experiments using pulsed-dye laser spectroscopic ellipsometry for studies of the wavelength dependence of the emissivities and optical properties of materials at high temperature. Preliminary results are given for liquid Al. The application of four-detector polarimetry for rapid determination of surface emissivity and true temperature is also described. Characteristics of these devices are presented. An example of the accuracy of this instrument in measurements of the melting point of zirconium is illustrated.

Krishnan, Shankar↗
DOE OSTI2024

A novel means to generate high pressure

Diamond anvil cells are the most popular means of generating pressures above 2 GPa. However, in many experiments, such as nuclear magnetic resonance and x-ray absorption, the metallic pressurizing gasket (which confines much of the sample) represents an occluding barrier that requires a low Z gasket material (e.g., Be), a split gasket, or other means to enable better coupling of the sample to electromagnetic radiation. In this paper, we demonstrate a novel method for generating high pressures that confines the sample just above the plane of the gasket by using a diamond with a laser hole drilled into the center of the tip. The sample is then confined by the hole, which is sealed by a flat gasket that fits over the hole. When load is applied to the diamonds, metal flows from the deformed gasket into the hole thereby pressurizing the sample similarly to how a piston pressurizes gas inside a cylinder. The pressurized sample is above the metallic gasket plane just inside the tip of the diamond, and thus easily accessible via x rays or visible light that skims just above the plane of the gasket providing an enhanced aperture of radiation collection. Furthermore, we have demonstrated the utility of this method by obtaining Raman spectra of SnC 2 O 4 and x-ray diffraction spectra of seleno-DL-cystine, all at high pressures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Improvements to the characterization of Agfa x-ray film for use on opacity spectroscopy diagnostics

The National Ignition Facility uses a soft x-ray opacity spectrometer for x-ray spectral imaging in high-energy-density experiments. The increased demand for a better spectral resolution prompted the investigation into the Agfa D4 film. Characterization is already under way for the film. A Manson x-ray source using six different anodes was used to expose film to the linear optical density (OD) region. This is a continuation of the previous work, and the updated analysis process is communicated here. The identified uncertainties have been reduced with the updated steps that improve the results of the characterization process. In conclusion, when the Stanford Synchrotron Radiation Lightsource Beamline 16-2 was operational, the film was characterized at that source. Its beam offered a higher fluency with a lower exposure time needed to reach saturation. Results for both sources are compared in this paper.

47 OTHER INSTRUMENTATION↗
NASA NTRS1980

Lightning Technology: Proceedings of a Technical Symposium

Several facets of lightning technology are considered including phenomenology, measurement, detection, protection, interaction, and testing. Lightning electromagnetics, protection of ground systems, and simulated lightning testing are emphasized. The lightning-instrumented F-106 aircraft is described.

Source record↗
NASA NTRS1984

Molecular astronomy at submillimeter wavelengths

It is pointed out that the region of the spectrum from 300 to 3000 GHz (100 to 1000 microns), which is referred to as the submillimeter, is one of the least explored areas in the electromagnetic spectrum. The reasons for this situation are related to a lack of adequate instrumentation for detecting the radiation and an almost complete absorption of the radiation by the earth's atmosphere. The vast majority of the rotational transitions of molecules occur in the millimeter and submillimeter wavelength region of the spectrum. The strength of the lines increases at higher frequencies until a condition is reached in which the energy levels are no longer populated. The study of molecular clouds at submillimeter wavelengths promises to provide new important results. Attention is given to the design of suitable submillimeter receivers, problems of atmospheric transmission, and galactic molecular lines.

Buhl, D.↗
NASA NTRS1985

The Earth Observing System - A multidisciplinary system for the long-term acquisition of earth science data from space

The development of the Earth Observing System (EOS) requirements is examined. An envisioned, EOS is to be NASA's multidisciplinary approach to acquisition of earth science data in the 1990s. The rationale and assumptions for the EOS are presented, together with a discussion of anticipated operations and use environments. Planned instrumentation concepts are discussed, involving a broad array of multiuse sensors operating across the electromagnetic spectrum from the ultraviolet to the microwave and including both active and passive techniques. Concepts for the near-polar orbiting observatory system, and essentially permanent man-serviced and -tended facility, are presented, along with concepts for information capture, processing and distribution and for common data-base referencing of acquired data. Milestones are indicated that are to be passed before a commitment to program execution can be made later in this decade.

Broome, D. R., Jr.↗