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White, R.

Publications and source records attributed to White, R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Lyman Alpha Blobs in a Filament at z=2.38

Bright, extended Lyman-alpha nebulae (known as blobs) appear to be common in the densest environments at high redshift, and may be an important stage in galaxy evolution. Up to now, Chandra data have not distinguished between the possible excitation mechanisms, but suggest that we are seeing dense excitation mechanisms, but suggest that we are seeing dense intracluster gas either falling into forming galaxies (cooling flows) or being expelled into the intracluster medium, enriching it. Optical and X-ray evidence also suggests that some blobs harbor AGN. We took a 20 ksec exposure with Chandra of four Lyman-alpha blobs in a large filament at $z=2.38$, which completed the X-ray observations of all currently known blobs. We will present flux constraints for the blobs from the Chandra data and optical spectra of the field taken with the AAT+2dF (see accompanying poster by Woodgate et al.). Possible mechanisms for the extended emission of the Lyman-alpha blobs will be discussed.

Williger, G.↗
NASA NTRS2000

Virtual Reality Robotic Operation Simulations Using MEMICA Haptic System

There is an increasing realization that some tasks can be performed significantly better by humans than robots but, due to associated hazards, distance, etc., only a robot can be employed. Telemedicine is one area where remotely controlled robots can have a major impact by providing urgent care at remote sites. In recent years, remotely controlled robotics has been greatly advanced. The robotic astronaut, "Robonaut," at NASA Johnson Space Center is one such example. Unfortunately, due to the unavailability of force and tactile feedback capability the operator must determine the required action using only visual feedback from the remote site, which limits the tasks that Robonaut can perform. There is a great need for dexterous, fast, accurate teleoperated robots with the operator?s ability to "feel" the environment at the robot's field. Recently, we conceived a haptic mechanism called MEMICA (Remote MEchanical MIrroring using Controlled stiffness and Actuators) that can enable the design of high dexterity, rapid response, and large workspace system. Our team is developing novel MEMICA gloves and virtual reality models to allow the simulation of telesurgery and other applications. The MEMICA gloves are designed to have a high dexterity, rapid response, and large workspace and intuitively mirror the conditions at a virtual site where a robot is simulating the presence of the human operator. The key components of MEMICA are miniature electrically controlled stiffness (ECS) elements and Electrically Controlled Force and Stiffness (ECFS) actuators that are based on the sue of Electro-Rheological Fluids (ERF). In this paper the design of the MEMICA system and initial experimental results are presented.

NDE NDT composite materials defects inspection↗
NASA NTRS1994

Evaluation of a 256 x 256 Si:As IBC detector array for astronomy

256 x 256-element IBC Si:As arrays have been evaluated for applications in IR astronomy from space-borne platforms. Basic figures of merit were measured at IR flux levels simulating those expected in space-based astronomical observations. Results include dark current less than 20 e(-)/s, G-eta as high as 3.8, eta/beta of 20%, and read noise below 100 rms(e(-)).

Mckelvey, M. E.↗
NASA NTRS1992

ROSAT implementation of a proposed multi-mission x ray data format

Until recently little effort has been made to ensure that data from X-ray telescopes are delivered in a format that reflects the common characteristics that most X-ray datasets share. Instrument-specific data-product design hampers the comparison of X-ray measurements made by different detectors and should be avoided whenever possible. The ROSAT project and the High Energy Astrophysics Science Archive Research Center (HEASARC) have defined a set of X-ray data products ('rationalized files') for ROSAT data that can be used for distribution and archiving of data from other X-ray missions. This set of 'rationalized files' has been defined to isolate instrument-independent and instrument-specific quantities using standards FITS constructs to ensure portability. We discuss the usage of the 'rationalized files' by ROSAT for data distribution and archiving, with particular emphasis on discrimination between instrument-independent and instrument-specific quantities, and discuss application of this format to data from other X-ray missions.

Corcoran, M.↗
NASA NTRS1986

A multiwavelength investigation of the supernova remnant IC 443

Multiwavelength observations of the supernova remnant IC 443 at radio, infrared, optical, ultraviolet, and X-ray wavelengths are presented. This morphological study of IC 443 presents a detailed picture of an adolescent supernova remnant in a multiphase interstellar medium. Radio observations show that better than 80 percent of the continuum emission at 18 cm is in a large-scale (greater than 18 arcmin) component. Decomposition of the infrared data shows that radiatively heated dust, shocked blackbody dust emission, and infrared line emission are all important components of the observed IRAS fluxes. The morphology of the IC 443 region is consistent with a supernova blast in an interstellar medium with a nonuniform distribution of clouds. The bright northeast rim and the great extent of the remnant to the southwest are most easily explained by a cloud filling factor which is greatest in the northeast and falls off toward the southwest.

Mufson, S. L.↗
NASA NTRS1985

Over-the-Wing Propeller Reduces Wing Drag

Airflow favorably altered if propeller placed above and behind wing. Relocating propeller induces flow over wing airfoil leading edge, which produces leading-edge suction forces not usually attainable by wing in free-stream flow. Concept reduced drag significantly on aircraft model in 12-foot (3.7-meter) wind tunnel. Relocation also helps to reduce cabin noise.

Johnson, J. L., Jr.↗
NASA NTRS1983

Autonomous satellite navigation by stellar refraction

This paper describes an error analysis of an autonomous navigator using refraction measurements of starlight passing through the upper atmosphere. The analysis is based on a discrete linear Kalman filter. The filter generated steady-state values of navigator performance for a variety of test cases. Results of these simulations show that in low-earth orbit position-error standard deviations of less than 0.100 km may be obtained using only 40 star sightings per orbit.

Gounley, R.↗
NASA NTRS1979

Full-scale wind-tunnel investigation of an Ayres S2R-800 Thrush Agricultural Airplane

This paper summarizes the significant results of recent full-scale wind tunnel tests at the NASA-Langley Research Center of the Ayres S2R-800 Thrush Agricultural Aircraft. The purpose of the tests was to provide fundamental aerodynamic, performance, and stability and control information of the airplane and dispersal equipment; and to study near-field wake interaction characteristics behind the aircraft. The aerodynamic tests included the use of a propeller thrust-torque balance to measure the efficiency of the propeller in the presence of the engine and to provide data for determining slipstream interference effects and slip-stream drag.

Johnson, J. L., Jr.↗
NASA NTRS1975

Advanced Earth Observation System Instrumentation Study (aeosis)

Various types of measurements were studied for estimating the orbit and/or attitude of an Earth Observation Satellite. An investigation was made into the use of known ground targets in the earth sensor imagery, in combination with onboard star sightings and/or range and range rate measurements by ground tracking stations or tracking satellites (TDRSS), to estimate satellite attitude, orbital ephemeris, and gyro bias drift. Generalized measurement equations were derived for star measurements with a particular type of star tracker, and for landmark measurements with a multispectral scanner being proposed for an advanced Earth Observation Satellite. The use of infra-red horizon measurements to estimate the attitude and gyro bias drift of a geosynchronous satellite was explored.

White, R.↗
NASA NTRS1975

Beryllium reflected cavity reactor for UF6 critical experiments

Experiments and theoretical studies are being conducted for NASA on critical assemblies with one-meter diam by one-meter long low-density cores surrounded by a thick beryllium reflector. These assemblies make extensive use of existing nuclear propulsion reactor components, facilities, and instrumentation. Due to excessive porosity in the reflector, the initial critical mass was 19 kg U(93.2). Addition of a 17-cm-thick by 89-cm-diam beryllium flux trap in the cavity reduced the critical mass to 7 kg when all the uranium was in the zone just outside the flux trap. A mockup aluminum UF6 container was placed inside the flux trap and fueled with uranium-graphite elements. Fission distributions and reactivity worths of fuel and structural materials are available. These results will be used to guide the design of a prototype plasma core reactor which will test energy removal by optical radiation.

Jarvis, G. A.↗
NASA NTRS1973

Investigation of configuration effects on entry heating distributions at Mach no. equal 8.0 (OH41)

Aerodynamic heating data were obtained on 0.006 scale models of four Rockwell International SSV double delta wing Orbiters in the Mach 8 variable density tunnel. A model of two previously tested Rockwell International Orbiters which are identified in the Configuration Description of this report were also tested. Orbiter surfaces were thermally mapped from the laminar through turbulent flight regimes during re-entry. Various modifications were made to model lower surfaces to determine the cause of transition in the vicinity of 3.0 million Reynolds number per foot. Re-entry data were acquired for angles of attack from 25 through 35 degrees at nominal Reynolds numbers per foot of 1.0, 2.0, 2.3, 2.5, 3.0, 3.5, 4.5 and 6.0 million utilizing the phase change paint technique. Launch data were acquired on the model upper surfaces for angles of attack of 0 and -5 degrees at nominal Reynolds numbers per foot of 3.0 and 6.0 million. A total of 70 orbiter heating runs and 6 material sample sphere runs were completed.

Gorowitz, H.↗