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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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152 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

31 Cygni: The B star and the wind

I have followed photospheric and wind absorptions in International Ultraviolet Explorer (IUE) spectra over much of the orbit of this K4 Ib+B3-4 binary system, using interstellar lines to transform all the velocities to a scale with the interstellar medium at -10.1 km/s. Results are as follows: Interstellar Fe II lines give NL (Fe(+)) = 1-2 x 10(exp 14)/sq cm with a Doppler width of 7 km/s; depletions of heavy elements along the line of sight to this star are similar to those for other stars with low interstellar densities. Photospheric lines yield a new velocity amplitude for the B star, K(sub B) = 23.2 +/- 1.0 km/s, which gives the mass ratio M(sub K)/M(sub B) = 1.66 and masses M(sub B) = 7.1 solar mass and M(sub K) = 11.7 solar mass. Existing photometry gives R(sub K) = 197 solar radius, R(sub B) = 5.2 solar radius, and i = 87.19 deg. Breadths of photospheric lines imply the rotational velocity of the B star is V sin i = 70-80 km/s. Most of the wind features are formed in a shell much larger than the binary system for which the terminal velocity seems to be 73 +/- 2 km/s, but it may be as high as approximately 90 km/s. The Doppler width (approximately 13 km/s) of Fe II shell lines likely results from acceleration of the wind, although it could reflect orbital motion of the K supergiant. Shell lines of Mg II and Si II are roughly consistent with Fe II, although their strengths are phase dependent, while S II requires a somewhat thicker shell in S(+) than in Fe(+) with a greater spread in expansion velocity. Shell lines of O I and N I are abnormally weak, if detected at all, and this implies that hydrogen is ionized throughout much of the wind. Lines of highly ionized species (C IV, Si Iv, and N V) appear sporadically in the spectrum and have inverse P Cyg profiles implying collapse (probably of an accretion disk) onto the B star. They do not seem to be isolated at particular phases as might be expected for formation in a conical shock front around an accretion column. I argue that the wind is roughly isotopic and is accelerated slowly, in agreement with existing ideas about winds.

Eaton, Joel A.↗
NASA NTRS2008

Displaying CFD Solution Parameters on Arbitrary Cut Planes

USMC6 is a Fortran 90 computer program for post-processing in support of visualization of flows simulated by computational fluid dynamics (CFD). The name "USMC6" is partly an abbreviation of "TetrUSS - USM3D Solution Cutter," reflecting its origin as a post-processor for use with USM3D - a CFD program that is a component of the Tetrahedral Unstructured Software System and that solves the Navier-Stokes equations on tetrahedral unstructured grids. "Cutter" here refers to a capability to acquire and process solution data on (1) arbitrary planes that cut through grid volumes, or (2) user-selected spheroidal, conical, cylindrical, and/or prismatic domains cut from within grids. Cutting saves time by enabling concentration of post-processing and visualization efforts on smaller solution domains of interest. The user can select from among more than 40 flow functions. The cut planes can be trimmed to circular or rectangular shape. The user specifies cuts and functions in a free-format input file using simple and easy-to-remember keywords. The USMC6 command line is simple enough that the slicing process can readily be embedded in a shell script for assembly-line post-processing. The output of USMC6 is a data file ready for plotting.

Pao, S. Paul↗
NASA NTRS2004

Blackbody Cavity for Calibrations at 200 to 273 K

A laboratory blackbody cavity has been designed and built for calibrating infrared radiometers used to measure radiant temperatures in the range from about 200 to about 273 K. In this below-room-temperature range, scattering of background infrared radiation from room-temperature surfaces could, potentially, contribute significantly to the spectral radiance of the blackbody cavity, thereby contributing a significant error to the radiant temperature used as the calibration value. The present blackbody cavity is of an established type in which multiple reflections from a combination of conical and cylindrical black-coated walls are exploited to obtain an effective emissivity greater than the emissivity value of the coating material on a flat exposed surface. The coating material in this case is a flat black paint that has an emissivity of approximately of 0.91 in the thermal spectral range and was selected over other, higher-emissivity materials because of its ability to withstand thermal cycling. We found many black coatings cracked and flaked after thermal cycling due to differences in the coefficient of expansion differences. On the basis of theoretical calculations, the effective emissivity is expected to approach 0.999. The cylindrical/conical shell enclosing the cavity is machined from copper, which is chosen for its high thermal conductivity. In use, the shell is oriented vertically, open end facing up, and inserted in a Dewar flask filled with isopropyl alcohol/dry-ice slush. A flange at the open end of the shell is supported by a thermally insulating ring on the lip of the Dewar flask. The slush cools the shell (and thus the black-body cavity) to the desired temperature. Typically, the slush starts at a temperature of about 194 K. The slush is stirred and warmed by bubbling dry air or nitrogen through it, thereby gradually increasing the temperature through the aforementioned calibration range during an interval of several hours. The temperature of the slush is monitored by use of a precise thermocouple probe.

Howell, Dane↗
NASA NTRS2010

Design Considerations of Polishing Lap for Computer-Controlled Cylindrical Polishing Process

The future X-ray observatory missions, such as International X-ray Observatory, require grazing incidence replicated optics of extremely large collecting area (3 m2) in combination with angular resolution of less than 5 arcsec half-power diameter. The resolution of a mirror shell depends ultimately on the quality of the cylindrical mandrels from which they are being replicated. Mid-spatial-frequency axial figure error is a dominant contributor in the error budget of the mandrel. This paper presents our efforts to develop a deterministic cylindrical polishing process in order to keep the mid-spatial-frequency axial figure errors to a minimum. Simulation studies have been performed to optimize the operational parameters as well as the polishing lap configuration. Furthermore, depending upon the surface error profile, a model for localized polishing based on dwell time approach is developed. Using the inputs from the mathematical model, a mandrel, having conical approximated Wolter-1 geometry, has been polished on a newly developed computer-controlled cylindrical polishing machine. We report our first experimental results and discuss plans for further improvements in the polishing process.

Khan, Gufran S.↗
NASA NTRS2004

Tool for Insertion of a Fiber-Optic Terminus in a Connector

A tool has been developed for the special purpose of inserting the terminus of an optical fiber in a cable connector that conforms to NASA Specification SSQ- 21635. What prompted the development of the tool was the observation that because of some aspects of the designs of fiber-optic termini and of springs, sealing rings, and a grommet inside the shell of such a connector, there is a tendency for the grommet to become damaged and detached from the sealing rings during installation. It is necessary to ensure the integrity of the grommet for proper sealing and proper functioning of the connector. The special-purpose tool provides the needed protection for the grommet. The grommet-protection tool resembles a funnel into which an axial slit has been cut (see figure). Prior to insertion, the grommet-protection tool is rolled so that one side of the slit overlaps the other side. The rolled-up grommet-protection tool is inserted in one of the connector holes that accommodate the fiber-optic termini and is pushed in until the flange (the wider of the two conical portions) of the tool becomes seated on the connector grommet. Then a special-purpose installation tool is inserted in the flange of the grommet-protection tool and pressed in until it becomes seated in the flange. This operation expands the narrower of the two conical portions of the grommet-protection tool. The installation tool is removed and the grommet-protection tool remains expanded due to the flat surfaces on the axial slit. By use of a standard contact-insertion tool, a fiber-optic terminus is inserted, through the grommet-protection tool, into the connector cavity. By use of a pair of forceps or needle-nose pliers, the grommet-protection tool is then pulled out of the cavity. Finally, the grommet-protection tool is removed from around the installed fiber-optic cable by pulling the cable through the axial slit. Unlike in some prior procedures for installing the fiber-optic termini in the connector, the procedure that involves the use of the present grommet-protection tool does not include the use of lubricants that can contaminate the interior of the connector. The grommet-protection tool is made of a fluoropolymer, taking advantage of the flexibility of such polymers and further taking advantage of the inherent slipperiness of fluoropolymers. Although the tool is designed primarily for insertion of a fiber-optic terminus, it might also be useful for extracting a previously installed fiber-optic terminus.

King, Wes↗
NASA NTRS1994

A study of a high resolution IUE spectrum of AM Canum Venaticorum

We have obtained the first high resolution IUE spectrum of the helium-rich, cataclysmic variable star AM CVn. The spectrum is greatly underexposed, but we can still detect both wide and narrow line profiles. We report broad, shortward-shifted, P-Cygni-like absorption and in some cases emission lines in the far UV high ionization resonance lines of C, N, O, and Si, but the profiles are considerably disk/boundary layer outflows, absorption disk continuum light in H-rich CVs. The highest ionizations show evidence of a narrow jet or conical flow. For other, lower ionized lines, we find some evidence of a stellar origin. The broad He II (lambda 1640 A) absorption profile with blue shifted emission core has a remarkably similar overall structure to the He II (lambda 1640 A) broad absorption trough in the IUE spectrum of the prototypical cool DO white dwarf HZ 21. The sharp absorption lines seem most convincingly in the resonance doublets of N V (lambda 1238 A, lambda 1242 A) and C IV (lambda 1548 A, lambda 1550 A) and in He II (lambda 1640 A) exhibit a precise velocity coincidence. These sharp features are almost certainly due to circumbinary matter because they are obviously unaffected by the rapid orbital motion (or rapid stellar rotation) in this short period system during the long (9.3 hour) IUE echelle exposure. Our observations support an evolution through shell episodes of a close binary system which ends up with an expanding envelope as seen for HZ 21, and suggests one possible evolutionary channel for production of DOs (DBs).

Solheim, J.-E.↗
NASA NTRS2010

Computer-Controlled Cylindrical Polishing Process for Large X-Ray Mirror Mandrels

We are developing high-energy grazing incidence shell optics for hard-x-ray telescopes. The resolution of a mirror shells depends on the quality of cylindrical mandrel from which they are being replicated. Mid-spatial-frequency axial figure error is a dominant contributor in the error budget of the mandrel. This paper presents our efforts to develop a deterministic cylindrical polishing process in order to keep the mid-spatial-frequency axial figure errors to a minimum. Simulation software is developed to model the residual surface figure errors of a mandrel due to the polishing process parameters and the tools used, as well as to compute the optical performance of the optics. The study carried out using the developed software was focused on establishing a relationship between the polishing process parameters and the mid-spatial-frequency error generation. The process parameters modeled are the speeds of the lap and the mandrel, the tool s influence function, the contour path (dwell) of the tools, their shape and the distribution of the tools on the polishing lap. Using the inputs from the mathematical model, a mandrel having conical approximated Wolter-1 geometry, has been polished on a newly developed computer-controlled cylindrical polishing machine. The preliminary results of a series of polishing experiments demonstrate a qualitative agreement with the developed model. We report our first experimental results and discuss plans for further improvements in the polishing process. The ability to simulate the polishing process is critical to optimize the polishing process, improve the mandrel quality and significantly reduce the cost of mandrel production

Khan, Gufran S.↗
NASA NTRS2013

Hyperspectral Microwave Atmospheric Sounder (HyMAS) Architecture and Design Accommodations

The Hyperspectral Microwave Atmospheric Sounder (HyMAS) is being developed at Lincoln Laboratories and accommodated by the Goddard Space Flight Center for a flight opportunity on a NASA research aircraft. The term "hyperspectral microwave" is used to indicate an all-weather sounding that performs equivalent to hyperspectral infrared sounders in clear air with vertical resolution of approximately 1 km. Deploying the HyMAS equipped scanhead with the existing Conical Scanning Microwave Imaging Radiometer (CoSMIR) shortens the path to a flight demonstration. Hyperspectral microwave is achieved through the use of independent RF antennas that sample the volume of the Earth s atmosphere through various levels of frequencies, thereby producing a set of dense, spaced vertical weighting functions. The simulations proposed for HyMAS 118/183-GHz system should yield surface precipitation rate and water path retrievals for small hail, soft hail, or snow pellets, snow, rainwater, etc. with accuracies comparable to those of the Advanced Technology Microwave Sounder. Further improvements in retrieval methodology (for example, polarization exploitation) are expected. The CoSMIR instrument is a packaging concept re-used on HyMAS to ease the integration features of the scanhead. The HyMAS scanhead will include an ultra-compact Intermediate Frequency Processor (IFP) module that is mounted inside the door to improve thermal management. The IFP is fabricated with materials made of Low-Temperature Co-fired Ceramic (LTCC) technology integrated with detectors, amplifiers, A/D conversion and data aggregation. The IFP will put out 52 channels of 16 bit data comprised of 4-9 channel data streams for temperature profiles and 2-8 channel streams for water vapor. With the limited volume of the existing CoSMIR scanhead and new HyMAS front end components, the HyMAS team at Goddard began preliminary layout work inside the new drum. Importing and re-using models of the shell, the scan head computer, and the slip rings developed for CoSMIR was the starting point. The next step was to modify the antenna faceplate to accommodate the dimensions of the three dual polarization Gaussian Optics Antenna (GOA) assemblies. Two mechanical concepts for the core technology, the hyperspectral IFP, were captured in a design tradeoff. Connector models considered minimum bend radii for the IFP analog connectors. Hyperspectral imaging is accomplished by strategically using a short wavelength intermediate frequency of 18-29 GHz, and thus reducing the size of components in the connection of the front end to the IFP. The SMK (2.92mm) Series connector will lay near the hinge line to minimize its flexing. The digital output of the IFP will use a Serial Peripheral Interface (SPI) that must be accommodated by the scan head computer. To make that computer more reliable, maintainable, and forward compatible with the 52 HyMAS channels, a testbed of the scan head, calibration, and archive computers and the PIC24 microprocessor that resides on the IFP is in development. The computers will be programmed using a new framework application called Interoperable Remote Component (IRC). This software allows flexibility to program computers that communicate with each other and can adapt easily to the emerging HyMAS requirements for data format, algorithms, and graphical user interface (GUI). It is expected that the CoSMIR instrument will cut over to the IRC after it is adapted on an updated CoSMIR testbed.

Hilliard, Lawrence↗