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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Prominence and Cool Loop Energetics Measured in the UV, EUV, and H-alpha

We investigate the thermal and dynamic properties of moving features in a prominence jet, a approx. 10(exp 5)K loop near a prominence channel, and an erupting prominence. In order to make measurements of the quickly moving features seen in prominences in the UV we use the SOHO/SUMER spectrograph to take a time series of exposures from a single pointing position, providing a measurement of spectral line properties as a function of time and position along the slit. The lines observed cover a broad range of temperatures from 80,000 - 1.6 million K. These measurements are combined with TRACE movies in transition region and coronal temperature bands and with ground based H-alpha data to obtain more complete information concerning prominence structure and motions. The resulting observations allow us perform DEM analysis and to calculate limits on densities, pressures, and the thermal and kinetic energies of the moving sources.

Kucera, Therese A.↗
NASA NTRS1998

Infrared Excess and Molecular Clouds: A Comparison of New Surveys of Far-Infrared and H I 21-cm Emission at High Latitudes

We have created a map of the large-scale infrared surface bightness in excess of that associated with the atomic interstellar medium, using region-by-region correlations between the far-infrared and 21-cm line surface brightness. Our study updates and extends a previous attempt with the Infrared Astronomical Satellite and Berkeley/Parkes H I surveys.

cosmology Diffuse Radiation Infrared ISM molecules↗
NASA NTRS2001

Detection of hydrazine (H) and (MMH) using cyranose E-nose

The Cyranose electronic nose (e-nose) has been used for the first time to detect hydrazine (H) and monomethyl hydrazine (MMH). The concentrations of hydrazine chosen in this study were 52 ppm (parts per million), 18 ppm, and 1.1 ppm and the concentrations of MMH was 14 ppm and 1 ppm. The Cyranose E-nose has detected hydrazine of 52 ppm and 18 ppm with a good response. The response of the E-Nose for 1.1 ppm hydrazine was insignificant. The response of E-Nose for 14 ppm MMH was significant and 1 ppm MMH was reasonably identifiable. The Cyranose E-Nose may be used to detect hydrazine and MMH with concentrations of at least 18 ppm and 1 ppm, respectively.

cyranose↗
NASA NTRS2006

Vibrational and rotational quenching of CO by collisions with H, He, and H2

Collisional quenching of molecular species is an important process in a variety of astrophysical environments including interstellar clouds, photodissociation regions, and cool stellar/planetary atmospheres. In this work, quantum mechanical scattering calculations are presented for the rotational and vibrational relaxation of rotationally-excited CO due to collisions with H, He and H2 for collision energies between 10(exp -6) and approx.15000/cm. The calculations were performed using the close-coupling approach and the l-labeled form of the coupled-states approximation. Cross sections and rate coefficients for the quenching of the v=0-2, j=0-6 levels of CO are presented and comparisons with previous calculations and measurements, where available, are provided.

Yang, Benhui↗
NASA NTRS2007

The Photodetachment of Ps ion and Low-Energy e(+) -H Collisions

Two calculations in the area of positron collisions are presented. The first is the calculation of the photodetachment cross section of the positronium negative ion (Ps-) using accurate variational wave functions for both the initial bound-state and the final P continuum state. The second is the calculation of partial wave cross sections for Ps(1s)-formation in ef -H(ls) collisions using the hyperspherical hidden crossing method. Since the S-wave Stiickelberg phase is close to pi, the very small S-wave Ps(1s) formation cross section can be understood in terms of destructive interference. Other examples in positron collisions are given where it is either known or expected that destructive interference is the cause of the small S-wave Ps(1s) formation cross section. In addition, examples are presented of processes in atomic physics where the Stiickelberg phase is a multiple of pi/2.

Ward, S.J.↗
NASA NTRS2009

NEXT Long-Duration Test After 11,570 h and 237 kg of Xenon Processed

The NASA s Evolutionary Xenon Thruster (NEXT) program is developing the next-generation ion propulsion system with significant enhancements beyond the state-of-the-art in ion propulsion to provide future NASA science missions with enhanced mission capabilities at a low total development cost. As part of a comprehensive thruster service life assessment utilizing both testing and analyses, a Long-Duration Test (LDT) was initiated to validate and qualify the NEXT propellant throughput capability to a qualification-level of 450 kg, 1.5 times the mission-derived throughput requirement of 300 kg. This wear test is being conducted with a modified, flight-representative NEXT engineering model ion thruster, designated EM3. As of September 1, 2007, the thruster has accumulated 11,570 h of operation primarily at the thruster full-input-power of 6.9 kW with 3.52 A beam current and 1800 V beam power supply voltage. The thruster has processed 237 kg of xenon surpassing the NSTAR propellant throughput demonstrated during the extended life testing of the Deep Space 1 (DS1) flight spare. The NEXT LDT has demonstrated a total impulse of 9.78 10(exp 6) N(dot)s; the highest total impulse ever demonstrated by an ion thruster. Thruster performance tests are conducted periodically over the entire NEXT throttle table with input power ranging 0.5 to 6.9 kW. Thruster performance parameters including thrust, input power, specific impulse, and thruster efficiency have been nominal with little variation to date. Lifetime-limiting component erosion rates have been consistent with the NEXT service life assessment, which predicts the earliest failure sometime after 750 kg of xenon propellant throughput; well beyond the mission-derived lifetime requirement. The NEXT wear test data confirm that the erosion of the discharge keeper orifice, enlarging of nominal-current-density accelerator grid aperture cusps at full-power, and the decrease in cold grid-gap observed during NSTAR wear testing have been mitigated in the NEXT design. NEXT grid-gap data indicate a hot grid-gap at full-power that is 60 percent of the nominal cold grid-gap. This paper presents the status of the NEXT LDT to date with emphasis on comparison to the NSTAR extended life test results.

Soulas, George C.↗
NASA NTRS2011

H-II Transfer Vehicle (HTV) and the Operations Concept for Extravehicular Activity (EVA) Hardware

With the retirement of the Space Shuttle fleet imminent in 2011, a new operations concept will become reality to meet the transportation challenges of the International Space Station (ISS). The planning associated with the retirement of the Space Shuttle has been underway since the announcement in 2004. Since then, several companies and government entities have had to look for innovative low-cost commercial orbital transportation systems to continue to achieve the objectives of ISS delivery requirements. Several options have been assessed and appear ready to meet the large and demanding delivery requirements of the ISS. Options that have been identified that can facilitate the challenge include the Russian Federal Space Agency's Soyuz and Progress spacecraft, European Space Agency's Automated Transfer Vehicle (ATV), and the Japan Aerospace Exploration Agency's (JAXA s) H-II Transfer Vehicle (HTV). The newest of these options is the JAXA's HTV. This paper focuses on the HTV, mission architecture and operations concept for Extra-Vehicular Activities (EVA) hardware, the associated launch system, and details of the launch operations approach.

Chullen, Cinda↗
NASA NTRS2011

The Detector Subsystem for the SXS Instrument on the Astro-H Observatory

The Soft X-ray Spectrometer (SXS) instrument on the Astro-H observatory is based on a 36 pixel x-ray calorimeter array cooled to 50 mK in a sophisticated spaceflight cryostat. The SXS is a true spatial-spectral instrument, where each spatially discrete pixel functions as a high-resolution spectrometer. Here we discuss the SXS detector subsystem that includes the detector array, the anticoincidence detector, the first stage amplifiers, the thermal and mechanical staging of the detector, and the cryogenic bias electronics. The design of the SXS detector subsystem has significant heritage from the Suzaku/XRS instrument but has some important modifications that increase performance margins and simplify the focal plane assembly. Notable improvements include x-ray absorbers with significantly lower heat capacity, improved load resistors, improved thermometry, and a decreased sensitivity to thermal radiation. These modifications have yielded an energy resolution of 3.5-4.0 eV FWHM at 6 keV for representative devices in the laboratory, giving considerable margin against the 7 eV instrument requirement. We expect similar performance in flight

Porter, Frederick↗
NASA NTRS2011

Design of a 3-Stage ADR for the Soft X-Ray Spectrometer Instrument on the Astro-H Mission

The Japanese Astro-H mission will include the Soft X-ray Spectrometer (SXS) instrument, whose 36-pixel detector array of ultra-sensitive x-ray microcalorimeters requires cooling to 50 mK. This will be accomplished using a 3-stage adiabatic demagnetization refrigerator (ADR). The design is dictated by the need to operate with full redundancy with both a superfluid helium dewar at 1.3 K or below, and with a 4.5 K Joule-Thomson (JT) cooler. The ADR is configured as a 2-stage unit that is located in a well in the helium tank, and a third stage that is mounted to the top of the helium tank. The third stage is directly connected through two heat switches to the JT cooler and the helium tank, and manages heat flow between the two. When liquid helium is present, the 2-stage ADR operates in a single-shot manner using the superfluid helium as a heat sink. The third stage may be used independently to reduce the time-average heat load on the liquid to extend its lifetime. When the liquid is depleted, the 2nd and 3rd stages operate as a continuous ADR to maintain the helium tank at as low a temperature as possible - expected to be 1.2 K - and the 1st stage cools from that temperature as a single-stage, single-shot ADR. The ADR s design and operating modes are discussed, along with test results of the prototype 3-stage ADR.

Shirron, Peter J.↗
NASA NTRS2012

The Astro-H Soft X-Ray Mirror

The Astro-H is led by the Japanese Space Agency (JAXA) in collaboration with many other institutions including the NASA Goddard Space Flight Center. Goddard's contributions include two soft X-ray telescopes (SXTs). The telescopes have an effective area of 562 square cm at 1 keV and 425 square cm at 6 keV with an image quality requirement of 1.7 arc-minutes half power diameter (HPD). The engineering model has demonstrated 1.1 arc-minutes HPD error. The design of the SXT is based on the successful Suzaku mission mirrors with some enhancements to improve the image quality. Two major enhancements are bonding the X-ray mirror foils to alignment bars instead of allowing the mirrors to float, and fabricating alignment bars with grooves within 5 microns of accuracy. An engineering model SXT was recently built and subjected to several tests including vibration, thermal, and X-ray performance in a beamline. Several lessons were learned during this testing that will be incorporated in the flight design. Test results and optical performance are discussed, along with a description of the design of the SXT.

Robinson, David↗
NASA NTRS2012

The High Resolution Microcalorimeter Soft X-Ray Spectrometer for the Astro-H Mission

We are developing the Soft X-Ray Spectrometer for the JAXA Astro-H mission. The instrument features a 5 eV, 36-pixel array of micro calorimeters designed for high spectral resolution from 0.3-12 keV at the focus of an x-ray mirror, providing a field of view of3 x 3 arcmin. The principal components of the spectrometer are the microcalorimeter detector system, a 3-stage ADR and dewar. The dewar is a long-life, hybrid design with a superfluid He cryostat, Joule-Thomson cooler, and Stirling coolers. We describe the present design of the SXS instrument and initial engineering model test results.

Kelley, Richard L.↗
NASA NTRS2012

Dynamics of Galaxy Clusters and Expectations from Astro-H

Galaxy clusters span a range of dynamical states, from violent mergers -- the most energetic events in the Universe -- to systems near hydrostatic equilibrium that allow us to map their dark matter distribution using X-ray observations of the intracluster gas. Accurate knowledge of the cluster physics, and in particular, the physics of the hot intracluster gas, is required to realize the full potential of clusters as cosmological probes. So far, we have been studying the cluster dynamics indirectly, deducing merger geometries, cluster masses, etc., using X-ray brightness and gas temperature mapping. For the first time, the calorimeter onboard Astro-H will provide direct measurements of line-of-sight velocities and turbulent broadening in the intracluster gas, testing many of our key assumptions about clusters. This talk will summarize expectations for cluster dynamic studies with this new instrument.

Markevitch, Maxim↗
NASA NTRS2012

The High-Resolution X-Ray Microcalorimeter Spectrometer, SXS, on Astro-H

The science and an overview of the Soft X-ray Spectrometer onboard the STRO-H mission are presented. The SXS consists of X-ray focusing mirrors and a microcalorimeter array and is developed by international collaboration lead by JAXA and NASA with European participation. The detector is a 6 x 6 format microcalorimeter array operated at a cryogenic temperature of 50 mK and covers a 3' x 3' field of view of the X-ray telescope of 5.6 m focal length. We expect an energy resolution better than 7 eV (FWHM, requirement) with a goal of 4 eV. The effective area of the instrument will be 225 square centimeters at 7 keV; by a factor of about two larger than that of the X-ray microcalorimeter on board Suzaku. One of the main scientific objectives of the SXS is to investigate turbulent and/or macroscopic motions of hot gas in clusters of galaxies.

Mitsuda, Kazuhisa↗
NASA NTRS2012

Laboratory Measurements of the Dielectronic Recombination Satellite Transitions of He-Like FE XXV and H-Like FE XXVI

We present laboratory spectra of dielectronic recombination (DR) satellite transitions attached to the He-like and H-like iron resonance lines obtained with the NASA Goddard Space Flight Center X-ray calorimeter and produced by a thermal plasma simu1ation technique on the EBIT-I electron beam ion trap at the Lawrence Livermore National Laboratory. We demonstrate that the calorimeter has sufficient spectral resolution in the 6-9 keV range to provide reliable measurements not only of standard DR satellite to resonance line intensities but also of DR satellite to DR satellite ratios that can be used to diagnose nonthermal electron distributions. Electron temperatures derived from the measured line intensities are consistent with the temperature of the simulated plasma. Temperature measurements based on DR satellite transitions have significant advantages over those based on collisional ionization equilibrium or continuum shape. Thus, successful demonstration of this method with the X-ray calorimeter is an important step fur its application in X-ray astronomy.

Gu, M. F.↗