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NASA NTRS2009

Physics of Reconnection and MMS Mission

Reconnection is the most important process driving the Earth's magnetosphere. Key to the success of the MMS science plan is the coupling of theory and observation. Determining the kinetic processes occurring in the diffusion region and physical parameters that control the rate of magnetic reconnection are among primary objectives of the MMS mission. Analysis of the role played by particle inertial effects in the diffusion region where the plasma is unmagnetized will be presented. The reconnection electric field in he diffusion region is supported primarily by particle non-gyrotropic effects. At the quasi-steady stage the reconnection electric field serves to accelerate and heat the incoming plasma population to maintain the current flow in the diffusion region the pressure balance. The primary mechanism controlling the dissipation in the vicinity of the reconnection site is incorporated into the fluid description in terms of non-gyrotropic corrections to the. induction and energy equations. The results of kinetic and fluid simulations illustrating the physics of magnetic reconnection will be presented. We will dem~:tistrate that kinetic nongyrotropic effects can significantly alter the global magnetosphere evolution and location of reconnection sites.

Kuznetsova, M. M.↗

NASA NTRS1977

Change detection in coastal zone environments

A study was conducted with the objective to develop and evaluate various change detection techniques based upon computer-aided analysis of Landsat multispectral scanner (MSS) data to monitor coastal zone environments. The study site selected includes a portion of the Matagorda Bay estuarine system located along the Texas Coast. The principal data sources for the study were MSS data collected on November, 27, 1972 and February 25, 1975. The MSS data were processed and a multidata eight-channel data set at a scale of 1:24,000 was obtained. A description is presented of four change detection techniques which were designed and implented for evaluation, taking into account postclassification comparison change detection, delta data change detection, spectral/temporal change classification, and layered spectral/temporal approach. The results of the investigation are discussed.

Weismiller, R. A.↗

NASA NTRS1992

The BATSE experiment on the Compton Gamma Ray Observatory: Status and some early results

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (GRO) is a sensitive all-sky detector system. It consists of eight uncollimated detectors at the corners of the spacecraft which have a total energy range of 15 keV to 100 MeV. The primary objective of BATSE is the detection, location, and study of gamma ray bursts and other transient sources. The instrement also has considerable capability for the study of pulsars, solar flares, and other discrete high energy sources. The experiment is now in full operation, detecting about one gamma ray burst per day. A brief description of the on-orbit performance of BATSE is presented, along with examples of early results from some of the gamma ray bursts.

Fishman, G. J.↗

NASA NTRS2010

An Experimental Study of Fan Inflow Distortion Tone Noise

The tone noise generated when a fan ingests circumferentially distorted flow was studied by an experiment conducted with the Advanced Noise Control Fan at the NASA Glenn Research Center. The inflow was distorted by inserting cylindrical rods radially into the duct. The rods were arranged in circumferentially irregular patterns in three of the five configurations tested. Rods were held in place using a mounting ring with 30 equally spaced holes placed at an axial location one rotor chordlength upstream of the fan. Acoustic pressure was measured in the inlet and exhaust duct of the fan using the Rotating Rake fan tone measurement system. Sound power levels, calculated from the measured data, were plotted as a function of circumferential mode. An analytic description of the unsteady pressure distribution at the interaction plane between the stationary rods and the fan rotor is presented in a form suitable for representing the circumferentially irregularly placed rods. Terms in the analytical description for sound power were proven to be useful in determining the dominant circumferential modes measured in the experiment and the differences in mode power level between the configurations tested. Insight gained through this work will be useful in the development of tools to compute fan inflow distortion tone noise.

Koch, L. Danielle↗

NASA NTRS2004

A Resonator for Low-Threshold Frequency Conversion

A proposed toroidal or disklike dielectric optical resonator (dielectric optical cavity) would be made of an optically nonlinear material and would be optimized for use in parametric frequency conversion by imposition of a spatially periodic permanent electric polarization. The poling (see figure) would suppress dispersions caused by both the material and the geometry of the optical cavity, thereby effecting quasi-matching of the phases of high-resonance-quality (high-Q) whispering-gallery electromagnetic modes. The quasi-phase-matching of the modes would serve to maximize the interactions among them. Such a resonator might be a prototype of a family of compact, efficient nonlinear devices for operation over a broad range of optical wavelengths. A little background information is prerequisite to a meaningful description of this proposal: (1) Described in several prior NASA Tech Briefs articles, the whispering-gallery modes in a component of spheroidal, disklike, or toroidal shape are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. (2) For the sake of completeness, it must be stated that even though optical resonators of the type considered here are solid dielectric objects and light is confined within them by total internal reflection at dielectric interfaces without need for mirrors, such components are sometimes traditionally called cavities because their effects upon the light propagating within them are similar to those of true cavities bounded by mirrors. (3) For a given set of electromagnetic modes interacting with each other in an optically nonlinear material (e.g., modes associated with the frequencies involved in a frequency-conversion scheme), the threshold power for oscillation depends on the mode volumes and the mode-overlap integral. (4) Whispering-gallery modes are attractive in nonlinear optics because they maximize the effects of nonlinearities by occupying small volumes and affording high Q values

Iltchenko, Vladimir↗

NASA NTRS2021

Reference Guide for Project-Control Account Managers

The purpose of this guide is intended to be a quick reference for a Project-Control Account Manager (P-CAM) or technical manager empowered with a project’s cost, schedule, and technical responsibilities of a control account(s) when Earned Value Management (EVM) is required. The overall objective is to support the P-CAM in performing their responsibilities as they relate to EVM. In addition, the reference guide describes at a summary level how the scope, schedule, and budget of a project integrate for optimal planning and control of prime contracts and in-house projects. Because NASA implements a diverse and unique portfolio of projects, those projects have traditionally created project-specific systems to manage planning and performance analysis. However, establishment and implementation of a project management system that is common across all centers and mission directorates will facilitate the adoption of best business practices. In addition, the application of timely and predictive analysis, as well as, providing all stakeholders with greater insight into project performance will enhance opportunities for project success. For more detailed information, refer to the NASA EVM System Description; Integrated Baseline Review (IBR) Handbook; EVM Implementation Handbook; Schedule Management Handbook; Work Breakdown Structure (WBS) Handbook; and other agency/industry documentation. In addition, you may contact your local center’s EVM Focal Points. All this information and more can be found at and/or the NASA Engineering Network located at https://nen.nasa.gov/web/pm.

Christopher Lewis Sadler↗

NASA NTRS1981

A comparative study of nonreflecting far-field boundary condition procedures for unsteady transonic flow computation

Various nonreflecting far-field boundary condition procedures are compared by implementing them in the computer code LTRAN2. This code solves the implicit finite-difference representation of the small-disturbance equations for transonic flows about airfoils. The first- and second-approximate nonreflecting conditions, as proposed by Engquist and Majda, are compared with the condition derived from the full-characteristic equation. The far-field boundary conditions and the description of the algorithm for implementing these conditions in LTRAN2 are discussed. Various cases are computed and compared with results from the older, more conventional procedures. One concludes that the full-characteristic equation produces the most effective results, thus allowing the far-field boundary to be located closer to the airfoil; this decreases the computer time required to obtain the solution because fewer mesh points are required.

Kwak, D.↗

NASA NTRS1981

Flow visualization using a computerized data acquisition system

A computer-driven traversing mechanism combined with mass data storage, data reduction programs, and general-purpose graphics programs permits a visualization of complex flows. A unique seven-hole probe is used which permits reasonably accurate measurements of all average flow properties if the local flow angle does not exceed 80 degrees. A description is given of the wake of a lifting canard surface as this wake passes over a wing. The flow includes concentrated and dissipating vortices, large regions of reduced total pressure, and local flow angles up to 60 deg. All these features can be clearly seen and accurately located in the graphical output.

Gallington, R.↗

NASA NTRS1988

Parallel algorithm for determining motion vectors in ice floe images by matching edge features

A parallel algorithm is described to determine motion vectors of ice floes using time sequences of images of the Arctic ocean obtained from the Synthetic Aperture Radar (SAR) instrument flown on-board the SEASAT spacecraft. Researchers describe a parallel algorithm which is implemented on the MPP for locating corresponding objects based on their translationally and rotationally invariant features. The algorithm first approximates the edges in the images by polygons or sets of connected straight-line segments. Each such edge structure is then reduced to a seed point. Associated with each seed point are the descriptions (lengths, orientations and sequence numbers) of the lines constituting the corresponding edge structure. A parallel matching algorithm is used to match packed arrays of such descriptions to identify corresponding seed points in the two images. The matching algorithm is designed such that fragmentation and merging of ice floes are taken into account by accepting partial matches. The technique has been demonstrated to work on synthetic test patterns and real image pairs from SEASAT in times ranging from .5 to 0.7 seconds for 128 x 128 images.

Manohar, M.↗

NASA NTRS1992

Thermal control system for Space Station Freedom photovoltaic power module

The electric power for Space Station Freedom (SSF) is generated by the solar arrays of the photovoltaic power modules (PVM's) and conditioned, controlled, and distributed by a power management and distribution system. The PVM's are located outboard of the alpha gimbals of SSF. A single-phase thermal control system is being developed to provide thermal control of PVM electrical equipment and energy storage batteries. This system uses ammonia as the coolant and a direct-flow deployable radiator. This paper presents the description and development status of the PVM thermal control system.

Hacha, Thomas H.↗

NASA NTRS2010

Modeling Harris Current Sheets with Themis Observations

Current sheets are ubiquitous in nature. occurring in such varied locations as the solar atmosphere. the heliosphere, and the Earth's magnetosphere. The simplest current sheet is the one-dimensional Harris neutral sheet, with the lobe field strength and scale-height the only free parameters. Despite its simplicity, confirmation of the Harris sheet as a reasonable description of the Earth's current sheet has remained elusive. In early 2009 the orbits of the 5 THEMIS probes fortuitously aligned such that profiles of the Earth's current sheet could be modeled in a time dependent manner. For the few hours of alignment we have calculated the time history of the current sheet parameters (scale height and current) in the near-Earth region. during both quiet and active times. For one particular substorm. we further demonstrate good quantitative agreement with the diversion of cross tail current inferred from the Harris modeling with the ionospheric current inferred from ground magnetometer data.

Kepko, L.↗

NASA NTRS2001

Flight Performance of a Functionally Gradient Material, TUFI, on Shuttle Orbiter

TUFI (Toughened Uni-Piece Fibrous Insulation), a functionally gradient material has been successfully flying on the Shuttle Orbiters in several locations on two insulation substrates over the past few years. TUFI is composed of insulation and a gradated surface treatment. The locations it has flown include the base heat shield where damage had been observed after every flight before its application. It was also applied to the body flap, the bottom of the body flap and around selected windows and doors where damage had been observed in the past. A description of the types of processing used including substrates will be presented and its overall performance will be reviewed.

Leister, Daniel B.↗

NASA NTRS2003

A Chandra X-Ray Study of NGC 1068 IL the Luminous X-Ray Source Population

We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a approx. 50 ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0 B-mag/arcsec isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models. The power-law model provides the better description of the spectrum for 18 of these sources. For fainter sources, the spectral index has been estimated from the hardness ratio. Five sources have 0.4 - 8 keV intrinsic luminosities greater than 10(exp 39)ergs/ s, assuming that their emission is isotropic and that they are associated with NGC 1068. We refer to these sources as intermediate-luminosity X-ray objects (ISOs). If these five sources are X-ray binaries accreting with luminosities that are both sub-Eddington and isotropic, then the implied source masses are approx greater than 7 solar mass, and so they are inferred to be black holes. Most of the spectrally modeled sources have spectral shapes similar to Galactic black hole candidates. However, the brightest compact source in NGC 1068 has a spectrum that is much harder than that found in Galactic black hole candidates and other ISOs. The brightest source also shows large amplitude variability on both short-term and long-term timescales, with the count rate possibly decreasing by a factor of 2 in approx. 2 ks during our Chundra observation, and the source flux decreasing by a factor of 5 between our observation and the grating observations taken just over 9 months later. The ratio of the number of sources with luminosities greater than 2.1 x 10(exp 38) ergs/s in the 0.4 - 8 keV band to the rate of massive (greater than 5 solar mass) star formation is the same, to within a factor of 2, for NGC 1068, the Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This suggests that the rate of production of X-ray binaries per massive star is approximately the same for galaxies with currently active star formation, including "starbursts."

Smith, David A.↗

NASA NTRS2020

Discovery of a Nearby Young Brown Dwarf Disk

We report the discovery of the youngest brown dwarf with a disk at 102 pc from the Sun, WISEA J120037.79−784508.3 (W1200−7845), via the Disk Detective citizen science project. We establish that W1200−7845 is located in the 3.7 (+4.6,-1.4) Myr old ε Cha association. Its spectral energy distribution (SED) exhibits clear evidence of an infrared (IR) excess, indicative of the presence of a warm circumstellar disk. Modeling this warm disk, we find the data are best fit using a power-law description with a slope α = −0.94, which suggests that it is a young, Class II type disk. Using a single blackbody disk fit, we find T(eff,disk)= 521 K and L(IR)/L(*) =0.14. The near-IR spectrum of W1200−7845 matches a spectral type of M6.0 γ ± 0.5, which corresponds to a low surface gravity object, and lacks distinctive signatures of strong Paβ or Brγ accretion. Both our SED fitting and spectral analysis indicate that the source is cool (T(eff) = 2784–2850 K), with a mass of 42–58 M(Jup), well within the brown dwarf regime. The proximity of this young brown dwarf disk makes the system an ideal benchmark for investigating the formation and early evolution of brown dwarfs.

Maria C. Schutte↗

NASA NTRS1971

The MIT OSO-7 X-ray experiment. A five color survey of the positions and time variations of cosmic X-ray sources

The all-sky, X-ray measurements are made in five broad energy bands from 0.5 to 60 keV with X-ray collimators of one and three degree FWHM response. Working with the onboard star sensor source locations may be determined to a precision of plus or minus 0.1 deg. The experiment is located in wheel compartment number three of the spacecraft. A time division logic system divides each wheel rotation into 256 data bins in each of which X-ray counts are accumulated over a 190 second interval. Measurement chain circuits include provision for both geometric and risetime anticoincidence. A detailed description of the instrument is included as is pertinent operating information.

Taylor, R. S.↗

NASA NTRS1979

Analysis of turbulent free-jet hydrogen-air diffusion flames with finite chemical reaction rates

A numerical analysis is presented of the nonequilibrium flow field resulting from the turbulent mixing and combustion of an axisymmetric hydrogen jet in a supersonic parallel ambient air stream. The effective turbulent transport properties are determined by means of a two-equation model of turbulence. The finite-rate chemistry model considers eight elementary reactions among six chemical species: H, O, H2O, OH, O2 and H2. The governing set of nonlinear partial differential equations was solved by using an implicit finite-difference procedure. Radial distributions were obtained at two downstream locations for some important variables affecting the flow development, such as the turbulent kinetic energy and its dissipation rate. The results show that these variables attain their peak values on the axis of symmetry. The computed distribution of velocity, temperature, and mass fractions of the chemical species gives a complete description of the flow field. The numerical predictions were compared with two sets of experimental data. Good qualitative agreement was obtained.

Sislian, J. P.↗

NASA NTRS1993

Vortex flap flight test operations, a safe approach

A flight test experiment was conducted at the Langley Research Center to evaluate a wing leading-edge vortex flap concept designed for use on an aircraft with highly swept wings. The flap concept was designed as a modification to the wing leading edge of an F-106B airplane. The flight testing required operations at conditions that would exceed the structural load envelope of the basic airplane in order to acquire desired research data for the modified configuration. Accordingly, the operational envelope of the modified aircraft was incrementally expanded and real-time monitoring of airframe strains at critical wing locations was mandated to insure safety of flight. The flight tests were conducted in two phases: Phase I to establish baseline data with the unmodified wing, and Phase II to determine the effects of the vortex flap on performance, handling qualities, and flow field characteristics. This paper focuses on a description of the approach and procedures used to provide the strain-gage monitoring to insure structural integrity. Highlights of the wing modification and the overall operation are also included. Within a -year period, 110 research flights were successfully completed, providing researchers with sufficient data to assess the potential benefits ascribed to the vortex flap concept without encountering severe structural problems or mishaps.

Dicarlo, Daniel J.↗

NASA NTRS1993

Payload/GSE/data system interface: Users guide for the VPF (Vertical Processing Facility)

Payload/GSE/data system interface users guide for the Vertical Processing Facility is presented. The purpose of the document is three fold. First, the simulated Payload and Ground Support Equipment (GSE) Data System Interface, which is also known as the payload T-0 (T-Zero) System is described. This simulated system is located with the Cargo Integration Test Equipment (CITE) in the Vertical Processing Facility (VPF) that is located in the KSC Industrial Area. The actual Payload T-0 System consists of the Orbiter, Mobile Launch Platforms (MLPs), and Launch Complex (LC) 39A and B. This is referred to as the Pad Payload T-0 System (Refer to KSC-DL-116 for Pad Payload T-0 System description). Secondly, information is provided to the payload customer of differences between this simulated system and the actual system. Thirdly, a reference guide of the VPF Payload T-0 System for both KSC and payload customer personnel is provided.

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