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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Initial Results From The Chandra High Energy Transmission Grating Spectrometer

The High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-ray Observatory provides spectral resolving powers of 200-1000 over the range 0.4-8.0 keV (1.5-30 A) with effective area of 2-200 square centimeters. Initial observations during the activation and calibration phases of the mission show that the HETGS is performing as predicted prior to Chandra launch. The talk presented very preliminary results that illustrate the power of the HETGS for performing detailed studies of a wide range of celestial sources, including plasma diagnostics. This written version gives a brief summary of that talk with examples of preliminary spectra of Capella, the Crab pulsar, SS433 and the SNR E0102-72.

Canizares, C. R.↗
NASA NTRS2000

The Low Energy Effective Area of the Chandra Low Energy Transmission Grating Spectrograph

The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present the preliminary results from the in-flight calibration of the low energy response of the High Resolution Camera spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrograph (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (T = 25000 K and log g = 9.0) for comparison with the Chandra observations of Sirius B. The pre-flight calibration of the LETGS effective area only covered wavelengths shortward of 44 A (E less than 277 eV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths leads to an overestimate of the effective area by an average factor of about 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 44-185 A. We make an independent test of our results by the comparison of a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.

Pease, D.↗
NASA NTRSDate not supplied

Alternating Direct Current (ADC) - A New Form of Efficient Energy Transmission for Renewable Sources

The prevailing means of electricity transmission through Direct Current (DC) and Alternating Current (AC) have limitations with the ongoing transition to renewable energy sources. In this paper, we discuss a new form of energy transmission, known as alternating direct current (ADC) that would provide significant savings in energy consumption and simultaneously allow efficient utilization of generated energy from renewable sources. This has become possible due to substantial advances in electronics and optoelectronics technologies since the days of Nicholas Tesla and Thomas Edison. Recent efforts of implementing the proposed ADC technology in relevant environments have demonstrated significant energy savings and opened a new paradigm that has the potential to provide an efficient and cost-effective pathway for transition to renewable energy sources even with the existing grid infrastructure. The DC power utilization initiated by Thomas Edison can be stored in battery arrangement but suffers from line loss and hence is not efficient for long-distance transmission. However, AC power developed by Nicholas Tesla cannot be stored efficiently but can be transmitted over long distances due to significantly lower line losses. Currently, AC power is the global foundational energy transmission methodology used because of events that took place over 135 years ago involving Edison, Tesla, and Westinghouse, and since AC power can transmit long distances from power plants to end users efficiently and economically. Approximately 50 years ago, the introduction of semiconductors in commercialized electronic devices and products changed the way people consume electricity. Also, over the years, the expanding adaptation of nonlinear loads has adversely affected the grid stability and hence the utility infrastructures worldwide.

AC↗
NASA NTRS1986

The high energy transmission grating spectrometer for AXAF

Attention is given to a high energy transmission grating spectrometer that operates over the range 0.4-8 keV, giving resolving powers of 100-1000 and effective areas of 10-200 sq cm. The instrument, which is part of the MIT high resolution X-ray spectroscopy investigation, consists of a single array of grating facets of two types: medium energy gratings of 0.6-micron period, 0.5-micron thick silver mounted behind the outer three AXAF mirrors, and high energy gratings of 0.2-micron period, 1.0-micron thick gold mounted behind the inner three mirrors. The gratings are oriented so as to correct for coma and so that the medium and high energy spectra form a shallow 'X' at the AXAF focal plane. Likely targets include normal stars, binary X-ray sources, active galactic nuclei and quasars. The HETGS can also be used to give moderate resolution spectra of slightly extended sources and monochromatic images of sources with strong lines, such as supernova remnants in nearby galaxies.

Canizares, C. R.↗
NASA NTRS1977

Seismic energy transmission in an intensively scattering environment

In order to account for some special features of lunar seismograms, namely, the gradual build-up of the signal, the extremely prolonged tail, and the lack of apparent coherence among three orthogonal components of ground motion, a statistical approach is proposed for describing transmission of seismic energy through a medium in which strong scattering takes place. A seismic diffusion theory is presented for a medium with randomly distributed scatterers of a given size distribution. A solution of the resulting diffusion equation for an impulsive energy source gives a curve which fairly closely reproduces the envelope of typical lunar impact seismograms. Since the model is based on constant diffusivity, long-range transmission will require a combination of diffusion and wave propagation treatments for accurate description.

Nakamura, Y.↗
NASA NTRS2003

Probing the Inflow/Outflow and Accretion Disk of Cygnus X-1 in the High State with the Chandra High Energy Transmission Grating

Cygnus X-1 was observed in the high state at the conjunction orbital phase (0) with Chandra High Energy Transmission Grating (HETG). Strong and asymmetric absorption lines of highly ionized species were detected, such as Fe xxv, Fe xxiv, Fe xxiii, Si xiv, S xvi, Ne x, etc. In the high state the profile of the absorption lines is composed of an extended red wing and a less extended blue wing. The red wings of higher ionized species are more extended than those of lower ionized species. The detection of these lines provides a way to probe the properties of the flow around the companion and the black hole in Cyg X-1 during the high state. A broad emission feature around 6.5 keV was significantly detected from the spectra of both the Chandra/HETG and the RXTE/Proportional Counter Array. This feature appears to be symmetric and can be fitted with a Gaussian function rather than the Laor disk line model of the fluorescent Fe K(alpha) line from an accretion disk. The implications of these results on the structure of the accretion flow of Cyg X-1 in the high state are discussed.

Feng, Y. X.↗
NASA NTRS2018

New Constraints on the Geometry and Kinematics of Matter Surrounding the Accretion Flow in X-Ray Binaries from Chandra High-Energy Transmission Grating X-Ray Spectroscopy

The narrow, neutral Fe Kα fluorescence emission line in X-ray binaries (XRBs) is a powerful probe of the geometry, kinematics, and Fe abundance of matter around the accretion flow. In a recent study it has been claimed, using Chandra High-Energy Transmission Grating (HETG) spectra for a sample of XRBs, that the circumnuclear material is consistent with a solar-abundance, uniform, spherical distribution. It was also claimed that the Fe Kα line was unresolved in all cases by the HETG. However, these conclusions were based on ad hoc models that did not attempt to relate the global column density to the Fe Kα line emission. We revisit the sample and test a self-consistent model of a uniform, spherical X-ray reprocessor against HETG spectra from 56 observations of 14 Galactic XRBs. We find that the model is ruled out in 13/14 sources because a variable Fe abundance is required. In two sources a spherical distribution is viable, but with nonsolar Fe abundance. We also applied a solar-abundance Compton-thick reflection model, which can account for the spectra that are inconsistent with a spherical model, but spectra with a broader bandpass are required to better constrain model parameters. We also robustly measured the velocity width of the Fe Kα line and found FWHM values of up to approx. 5000 km/s. Only in some spectra was the Fe Kα line unresolved by the HETG.

Tzanavaris, P.↗
NASA NTRS1986

An Investigation of Energy Transmission Due to Flexural Wave Propagation in Lightweight, Built-Up Structures

A technique to measure flexural structure-borne noise intensity is investigated. Two accelerometers serve as transducers in this cross-spectral technique. The structure-borne sound power is obtained by two different techniques and compared. In the first method, a contour integral of intensity is performed from the values provided by the two-accelerometer intensity technique. In the second method, input power is calculated directly from the output of force and acceleration transducers. A plate and two beams were the subjects of the sound power comparisons. Excitation for the structures was either band-limited white noise or a deterministic signal similar to a swept sine. The two-accelerometer method was found to be sharply limited by near field and transducer spacing limitations. In addition, for the lightweight structures investigated, it was found that the probe inertia can have a significant influence on the power input to the structure. In addition to the experimental investigation of structure-borne sound energy, an extensive study of the point harmonically forced, point-damped beam boundary value problem was performed to gain insight into measurements of this nature. The intensity formulations were also incorporated into the finite element method. Intensity mappings were obtained analytically via finite element modeling of simple structures.

Mickol, John Douglas↗
NASA NTRS1980

Microwave power - An energy transmission alternative for the year 2000

Recent technological advances related to the feasibility of efficient RF-dc rectification make it likely that by the year 2000 the transmission of power through space will have become a practical reality. Proposals have been made to power helicopters, aircraft, balloons, and rockets remotely. Other proposals consider the transfer of power from point to point on earth via relay through space or a transmission of power from large power sources in space. Attention has also been given to possibilities regarding the transmission of power between various points in the solar system. An outline is provided of the microwave power transmission system envisaged for the solar power satellite, taking into account the transmitting antenna, the receiver on earth, aspects of beam formation and control, transmitter options, the receiving antenna design, and cost and efficiency considerations.

Nalos, E.↗
NASA NTRS2001

In Situ Observation of Carbonaceous Material in the Matrices of CV and CM Carbonaceous Chondrites: Preliminary Results from Energy Filtered Transmission Electron Microscopy

Energy filtered transmission electron microscopy shows that organic matter can be detected in situ in the matrices of carbonaceous chondrites at a spatial resolution of at least 1 nm. In CM chondrites, carbon is often associated with sulfide particles. Additional information is contained in the original extended abstract.

Brearley, A. J.↗
NASA NTRS2002

Heterogeneous Distribution of Carbonaceous Material in Murchison Matrix: In Situ Observations Using Energy Filtered Transmission Electron Microscopy

Energy filtered TEM (Transmission Electron Microscopy) has been used to study the location of carbonaceous material in situ in Murchison matrix. Carbon occurs frequently as narrow rims around sulfide grains, but is rare in regions of matrix that are dominated by phyllosilicates. Additional information is contained in the original extended abstract.

Brearley, Adrian J.↗
NASA NTRS1978

Medical tomograph system using ultrasonic transmission

Ultrasonic energy transmission in rectilinear array scanning patterns of soft tissue provides projection density values of the tissue which are recorded as a function of scanning position and angular relationship, .theta., of the subject with a fixed coordinate system. A plurality of rectilinear scan arrays in the same plane for different angular relationships .theta..sub.1 . . . .theta..sub.n thus recorded are superimposed. The superimposition of intensity values thus yields a tomographic image of an internal section of the tissue in the scanning plane.

Heyser, Richard C.↗
NASA NTRS1989

Power from space for use on earth: An emerging global option

The concept of the Earth as a closed ecological system is addressed from the point of view of the availability and use of energy from space and its potential influence on the economies of both developed and developing countries. The results of past studies of the solar power satellite (SPS) are reviewed, and the current international activities exploring various aspects of an SPS are mentioned. The functions of an SPS, including collection of solar energy in orbit, conversion to an intermediate form of energy, transmission of energy from orbit to Earth, and conversion to useful energy in the most appropriate form are discussed. Directions for future developments are addressed including a suggested planning framework. Salient aspects of SPS technologies are presented, and the potential benefits of the uses of lunar materials for the SPS construction are outlined. Scenarios within the context of international participation in a global SPS system are presented. The conclusion is drawn that an SPS system is one of the few promising, globally applicable power generation options that has the potential to meet energy demands in the 21st Century and to achieve the inevitable transition to inexhaustible and renewable energy sources.

Glaser, Peter E.↗
NASA NTRS2000

Chandra and the Emission Line Project

Calibration data obtained for the Chandra High Energy Transmission Grating and the Low Energy Transmission Grating Spectrometers are allowing us to test plasma spectral models against bright coronal sources with a range of electron temperatures. The three Emission Line Project targets - Capella, Procyon, and HR 1099 - are bright, well-studied X-ray and EUV emitters. The goals of the Emission Line Project are to determine and verify accurate and robust diagnostics; to identify and prioritize problems in fundamental spectroscopy; and to accelerate the improvement of the atomic database needed for modeling.

Brickhouse, N. S.↗
NASA NTRS1993

Science Instruments for the Advanced X-Ray Astrophysics Facility (AXAF)

The AXAF program has undergone major changes since the Announcement of Opportunity was extended by NASA Headquarters in 1983. The Science Instruments (SI's) for AXAF have also experienced several design changes since they were competitively selected in 1985. Moreover, two separate complementary missions are now being baselined for AXAF; one is designated AXAF-I for imaging and will include the high precision Wolter type I optics, and the other is called AXAF-S for spectroscopy. The resulting less-costly AXAF will still be superior to any previous x-ray observatories. Both missions continue to be managed. AXAF-I contains two focal plane SI's, the High Resolution Camera (HRC), and the AXAF Charge-Coupled Device (CCD) imaging spectrometer (ACIS), as well as the High-Energy Transmission Grating Spectrometer (HETGS) and the Low-Energy Transmission Grating Spectrometer (LETGS). Optics/Cryogenics Division (BECD). AXAF-S features only one focal plane SI, the X-Ray Spectrometer (XRS). The grazing incidence mirrors for this mission are mainly to provide a large collecting area and to concentrate these x-ray photons onto the XRS detector. Precise focusing, although preferred, is of secondary importance. Nested conical foil mirrors are currently baselined; however, replicated imaging optics are being evaluated for collecting efficiency and cost. AXAF-S is scheduled to be launched in late 1999. It has been designated as an MSFC in-house project. In addition to overall management, MSFC is fully responsible for the design, development, integration, and test of the complete AXAF-S observatory, including the XRS which will be furnished by the Goddard Space Flight Center (GSFC). Together, AXAF-I and AXAF-S constitute the third of NASA's series of Great Observatories, joining the Hubble space telescope (HST) and the Gamma-Ray Observatory (GRO) which are already operational. The develop- ment, launch, and operation of the Space InfraRed Telescope Facility (SIRTF) will follow later to complete the Great Observatory series. This paper summarizes the impact these changes have had on the SI's.

Carl E Winkler↗
NASA NTRSDate not supplied

Space Based Solar Power

Space based solar power (SBSP) entails in-space collection of solar energy, transmission of that energy to one or more stations on Earth, conversion to electricity, and delivery to the grid or to batteries for storage. Experts in both the aerospace and energy sectors are debating the benefits of SBSP as more organizations globally begin SBSP technology development programs. We conducted a study to evaluate the potential benefits, challenges, and options for NASA to engage with growing global interest in SBSP. We performed a first order lifecycle study of two representative SBSP designs for 2 GW utility-scale power generation that, for the purposes of the study, are presumed to begin in 2050. We assumed baseline capabilities to develop, assemble, operate, maintain, and dispose of the SBSP systems are a mix of capabilities that are above, below, or comparable to capabilities demonstrated to date. We then compared the lifecycle cost of electricity and lifecycle GHG emission intensity of the SBSP designs to alternative terrestrial renewable electricity production technologies. Our findings indicate the SBSP designs may produce lifecycle GHG emissions per unit of electricity that are comparable to terrestrial alternatives, pending further studies of upper atmosphere responses to launch emissions. We find the SBSP designs are more expensive than terrestrial alternatives and may have lifecycle costs per unit of electricity that are 12-80 times higher. Though, we do find cost competitiveness may be achieved if a favorable combination of cost and capability improvements related to launch and manufacturing that are beyond the advancements assumed in the baseline assessment can be attained.

Erica Rodgers↗