Search NASA⌕ Search

SEARCH · Search NASA

Results for “Jet lag”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

High performance space computing with system-on-chip instrument avionics for space-based Next Generation Imaging Spectrometers (NGIS)

The emergent technology of system-on-chip (SoC) devices promises lighter, smaller, cheaper, and more capable and reliable space electronic systems that could help to unveil some of the most treasured secrets in our universe. This technology is an improvement over the technology that is currently used in space applications, which lags behind state-of-the-art commercial-off-the-shelf (COTS) equipment by several generations. SoC technology integrates all computational power required by next-generation space exploration science instruments onto a single chip. This presentation will describe a Xilinx Zynq-based data acquisition, cloud-screening and compression computing system that has been developed at the Jet Propulsion Laboratory (JPL) for JPL’s Next Generation Imaging Spectrometers (NGIS). The Xilinx Zynq-based Alpha Data hardware assembly fits into a 120mm by 190m by 40mm assembly and uses 9 watts at peak performance. The computing element is a Xilinx Zynq Z7045Q which includes a Kintex-7 FPGA (equivalent to 3 RAD Virtex5 FPGAs in terms of logic cell resources) and dual-core ARM Cortex-A9 Processors (equivalent to 10 RAD750 Power PCs in term of processing capability).

Dolinar, Sam↗
NASA NTRS2004

Frequency-Dependent Time Lags in Three Blazars

The work completed includes the analysis of observations obtained during Cycle 6 of the Rossi X-ray Timing Explorer (RXTE). The project is part of a longer-term, continuing program to study the X-ray emission process in blazars in collaboration with Dr. Ian McHardy (U. of Southampton, UK). The goals of the program are to study the X-ray emission mechanism in blazars and the relation of the X-ray emission to changes in the relativistic jet. The program includes contemporaneous brightness and linear polarization monitoring at radio and optical wavelengths, total and polarized intensity imaging at 43 GHz with a resolution of 0.1 milliarcseconds with the VLBA, and well-sampled X-ray light curves obtained from a series of approved RXTE programs. During RXTE cycle 6, the project was awarded RXTE time to monitor three quasars: PKS 1510-089 two times per week, and 3C 273 and 3C 279 three times per week each. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained 2-3 times per week in the centimeter-wave band with the Michigan radio telescope, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world. Since it is the long-term X-ray light curve that is of greatest value, this report includes discussion of all the data collected through August 2003 rather than just the Cycle 6 data.

Marscher, Alan P.↗
NASA NTRS1993

The infrared light curve of Periodic Comet Halley 1986 III and its relationship to the visual light curve, C2, and water production rates

The near-IR light curve of Periodic Comet Halley 1986 III is analyzed and compared with C2 production, water production, and the visual light curve. This is the most complete IR light curve compiled to date for any comet. The scattering phase function at small sun-comet-earth angles is shown to affect the slope of near-IR light curve significantly. P/Halley's dust production, as inferred from the IR light curve showed an increased production rate near perihelion which appears to be correlated with the onset of significant jet activity. The near-IR light curve, visual light curve, C2, and water production rates displayed different heliocentric variations, suggesting that one parameter cannot be accurately estimated from another. This is particularly true of the early preperihelion visual light curve. A peak of 0.3-0.5 magnitude in the visual magnitude, representing the integrated brightness of the comet's visible coma, lagged the other parameters by about a day. The near-IR color, J-H, was less red during periods of strong dust activity.

Morris, Charles S.↗
NASA NTRS2018

LiveCheckHSI: a Hardware/Software Co-verification Tool for Hyperspectral Imaging Systems with Embedded System-on-Chip Instrument Avionics

The emergent technology of system-on-chip (SoC) devices promises lighter, smaller, cheaper, and more capable and reliable space electronic systems that could help to unveil some of the most treasured secrets in our universe. This technology is an improvement over the technology that is currently used in space applications, which lags behind state-of-the-art commercial-off-the-shelf (COTS) equipment by several generations. SoC technology integrates all computational power required by next-generation space exploration science instruments onto a single chip. This paper describes hardware/software co-verification tools for the Xilinx Zynq-based control and data handling system that have been developed at the Jet Propulsion Laboratory (JPL) for visible-infrared imaging spectrometers. The system acquires and compresses images in real-time, in addition to programming the spectrometer (frame rate, exposure time), focus step motor, and heaters and reporting telemetry.

Dolman, David↗
NASA NTRS1993

Multiwavelength monitoring of the BL Lacertae object PKS 2155-304. I - The IUE campaign

Daily monitoring of PKS 2155-304 with the IUE satellite throughout November 1991 revealed dramatic large-amplitude rapid variations in the UV flux of this BL Lac object. Many smaller, rapid flares are superposed on a general doubling of the intensity. During the five-day period when sampling was roughly continuous, the rapid flaring had an apparent quasi-periodic nature, with peaks repeating every 0.7 day. The short- and long-wavelength UV light curves are well correlated with each other, and with the optical light curve deduced from the Fine Error Sensor on IUE. The formal lag is zero, but the cross-correlation is asymmetric in the sense that the shorter wavelength emission leads the longer. The UV spectral shape varies a small but significant amount. The correlation between spectral shape and intensity is complex. The sign of the correlation is consistent with the nonthermal acceleration processes expected in relativistic plasmas, so that the present results are consistent with relativistic jet models, which can also account for quasi-periodic flaring.

Urry, C. M.↗
NASA NTRS2004

Gamma-Ray Burst Intensity Distributions

We use the lag-luminosity relation to calculate self-consistently the redshifts, apparent peak bolometric luminosities L(sub B1), and isotropic energies E(sub iso) for a large sample of BATSE bursts. We consider two different forms of the lag-luminosity relation; for both forms the median redshift, for our burst database is 1.6. We model the resulting sample of burst energies with power law and Gaussian dis- tributions, both of which are reasonable models. The power law model has an index of a = 1.76 plus or minus 0.05 (95% confidence) as opposed to the index of a = 2 predicted by the simple universal jet profile model; however, reasonable refinements to this model permit much greater flexibility in reconciling predicted and observed energy distributions.

Band, David L.↗
NASA NTRS2016

Parameter Uncertainty for Aircraft Aerodynamic Modeling using Recursive Least Squares

A real-time method was demonstrated for determining accurate uncertainty levels of stability and control derivatives estimated using recursive least squares and time-domain data. The method uses a recursive formulation of the residual autocorrelation to account for colored residuals, which are routinely encountered in aircraft parameter estimation and change the predicted uncertainties. Simulation data and flight test data for a subscale jet transport aircraft were used to demonstrate the approach. Results showed that the corrected uncertainties matched the observed scatter in the parameter estimates, and did so more accurately than conventional uncertainty estimates that assume white residuals. Only small differences were observed between batch estimates and recursive estimates at the end of the maneuver. It was also demonstrated that the autocorrelation could be reduced to a small number of lags to minimize computation and memory storage requirements without significantly degrading the accuracy of predicted uncertainty levels.

Grauer, Jared A.↗
NASA NTRS1974

Specialists Meeting on Rotorcraft Dynamics, Moffett Field, Calif., February 13-15, 1974, Proceedings

Analysis of specific problems in rotorcraft dynamics. Topics include hingeless rotor theory, dynamic stall modelling, periodic systems identification, analysis of complex systems with phasing matrices, flapping stability, flap-lag dynamics at high advance ratios, finite element analysis and fuselage free-vibration characteristics, coupled rotor/frame vibration methods, gust response characteristics with unsteady stall effects, antiresonance theory, cyclic feathering motions and dynamic loads, control load envelope shaping, rotor aeroelasticity, use of Floquet theory, theory of proprotors and tilt-rotors, two-bladed teetering rotors, stability of air and ground resonance, vertical-plane pendulum absorbers, multicyclic jet-flap control, engine/frame interface dynamics, and others. The minutes of the question and answer periods following the presentations are presented in the supplement. Individual items are announced in this issue.

Source record↗
NASA NTRS1978

Vision-based guidance for an automated roving vehicle

A controller designed to guide an automated vehicle to a specified target without external intervention is described. The intended application is to the requirements of planetary exploration, where substantial autonomy is required because of the prohibitive time lags associated with closed-loop ground control. The guidance algorithm consists of a set of piecewise-linear control laws for velocity and steering commands, and is executable in real time with fixed-point arithmetic. The use of a previously-reported object tracking algorithm for the vision system to provide position feedback data is described. Test results of the control system on a breadboard rover at the Jet Propulsion Laboratory are included.

Griffin, M. D.↗
NASA NTRS1956

Experimental Investigation of Dynamic Relations in a 48-inch Ram-jet Engine

Engine dynamics were investigated for supercritical operation of the ram jet at Mach 2.75 over a range of simulated altitudes from 68,000 to 82,000 feet. Indicial-and frequency-response tests were conducted with fuel flow as the input variable. For a wide range of operating points, the response of static or total pressure to fuel flow consisted of a dead time followed by a response form that generally approximated a linear, first-order, lead-lag. The dead time varied significantly only with distance from the combustion zone. The rise ratio and the time constant of the lead-lag function were nearly independent of the pressure sensed.

Hurrell, Herbert G↗
NASA NTRS1998

Comparison of the X-Ray and Radio Light Curves of Quasar PKS 1510--089

We present results for the X-ray-bright superluminal AGN PKS 1510-089 (z=0.36) monitored weekly with the Rossi X-Ray Timing Explorer for the past four years in order to study the origin of X-ray emission from this extremely variable blazer. These RXTE data are compared with weekly cm-band flux and polarization observations from the Michigan Diameter telescope, to identify correlated activity and associated frequency-dependent time delays for constraining X-ray emission models; and bimonthly 7mm VLBA total and linearly polarized intensity imaging to identify temporal associations between X-ray events and the ejection of superluminal components and disturbances in the magnetic field, to test if the X-ray energy release is related to changes in the inner jet flow. Both the X-ray (2-20 keV) and radio flux are highly variable on timescales of weeks. The VLBA mas structure is dominated by a bright core with a weak jet; both the ejection of very fast superluminal knots and changes in the fractional polarization and EVPA of the core on timescales of one to four months are identified. Two outbursts in 1997 are well-resolved in both the centimeter and X-ray bands. Both the strong temporal association and the similar outburst shape support a causal relation, and a discrete cross-correlation analysis identifies that the X-ray lags the radio by 16 days during the bursts. Starting in 1998 the behavior changes: the correlation is weaker with the X-ray possibly leading the radio by six days. During the full time window there is a correlation between bands as expected if the radio photons are upscattered to X-ray energies. The time correlations and difference between the flat X-ray spectral index (0.0 <= alpha <= 0.5 where F(sub v) is proportional to v(exp -alpha)), and the mm-wave synchrotron spectrum (alpha = 0.8) are discussed within the framework of viable SSC models.

Aller, M. F.↗
NASA NTRS1994

Computational Analysis of Forebody Tangential Slot Blowing on the F/A-18

An overview of the computational effort to analyze forebody tangential slot blowing for use on the F/A-18 aircraft is presented. Tangential slot blowing generates side force and yawing moment which may be used to control the aircraft flying at high angle of attack. Computations using the isolated forebody are obtained at full-scale wind tunnel test conditions for direct comparison with available experimental data. The effects of jet exit conditions, jet length, and jet location are also studied using the isolated forebody. In addition, these computations are used to predict the effect of slot blowing at transonic maneuvering flight conditions. The effects of over- and under-blowing on force and moment production are analyzed. Non-time-accurate solutions are obtained to determine the steady-state side force and yawing moments generated by tangential slot blowing. Time-accurate solutions are obtained to study the force onset time lag of tangential slot blowing. The effect of blowing on the burst point location are then analyzed by obtaining computations using the aircraft geometry, which includes the wing, empennage, and faired-over inlets. The effect of blowing on the buffet loads on the vertical tails are analyzed using time-accurate computations. Comparison with available experimental data from full-scale wind tunnel and sub-scale wind tunnel tests are made. This computational analysis compliments the experimental results and provides a detailed understanding of the effects of tangential slot blowing on the flow field about the F/A-18.

Gee, Ken↗
NASA NTRS2013

Implicit Coupling Approach for Simulation of Charring Carbon Ablators

This study demonstrates that coupling of a material thermal response code and a flow solver with nonequilibrium gas/surface interaction for simulation of charring carbon ablators can be performed using an implicit approach. The material thermal response code used in this study is the three-dimensional version of Fully Implicit Ablation and Thermal response program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation method. Coupling between the material response and flow codes is performed by solving the surface mass balance in flow solver and the surface energy balance in material response code. Thus, the material surface recession is predicted in flow code, and the surface temperature and pyrolysis gas injection rate are computed in material response code. It is demonstrated that the time-lagged explicit approach is sufficient for simulations at low surface heating conditions, in which the surface ablation rate is not a strong function of the surface temperature. At elevated surface heating conditions, the implicit approach has to be taken, because the carbon ablation rate becomes a stiff function of the surface temperature, and thus the explicit approach appears to be inappropriate resulting in severe numerical oscillations of predicted surface temperature. Implicit coupling for simulation of arc-jet models is performed, and the predictions are compared with measured data. Implicit coupling for trajectory based simulation of Stardust fore-body heat shield is also conducted. The predicted stagnation point total recession is compared with that predicted using the chemical equilibrium surface assumption

Ablation↗
NASA NTRS1986

Steps toward 8m honeycomb mirrors. VIII - Design and demonstration of a system of thermal control

Directed jets of ambient temperature air are proposed for the maintenance of low internal temperature gradients and conformity with ambient temperatures in honeycomb-structure borosilicate glass telescope mirrors. The use of greater airflow on thicker sections, to match cooling rates, and the cooling or heating of the internal, back, and edge surfaces of the mirror at the same rate established by convection on the front surface, have been tested on a full scale glass thermal model of a single honeycomb cell from an 8-m diameter mirror. The internal thermal gradient (less than 0.1 C) and ambient-temperature-change lag (less than 0.24 C) ensure minimum image degradation.

Cheng, A. Y. S.↗
NASA NTRS2015

Solar Signals in CMIP-5 Simulations: The Stratospheric Pathway

The 11 year solar-cycle component of climate variability is assessed in historical simulations of models taken from the Coupled Model Intercomparison Project, phase 5 (CMIP-5). Multiple linear regression is applied to estimate the zonal temperature, wind and annular mode responses to a typical solar cycle, with a focus on both the stratosphere and the stratospheric influence on the surface over the period approximately 1850-2005. The analysis is performed on all CMIP-5 models but focuses on the 13 CMIP-5 models that resolve the stratosphere (high-top models) and compares the simulated solar cycle signature with reanalysis data. The 11 year solar cycle component of climate variability is found to be weaker in terms of magnitude and latitudinal gradient around the stratopause in the models than in the reanalysis. The peak in temperature in the lower equatorial stratosphere (approximately 70 hPa) reported in some studies is found in the models to depend on the length of the analysis period, with the last 30 years yielding the strongest response. A modification of the Polar Jet Oscillation (PJO) in response to the 11 year solar cycle is not robust across all models, but is more apparent in models with high spectral resolution in the short-wave region. The PJO evolution is slower in these models, leading to a stronger response during February, whereas observations indicate it to be weaker. In early winter, the magnitude of the modeled response is more consistent with observations when only data from 1979-2005 are considered. The observed North Pacific high-pressure surface response during the solar maximum is only simulated in some models, for which there are no distinguishing model characteristics. The lagged North Atlantic surface response is reproduced in both high- and low-top models, but is more prevalent in the former. In both cases, the magnitude of the response is generally lower than in observations.

stratosphere↗
NASA NTRS1998

Principal Investigator Microgravity Services: USMP-3

Two accelerometers provided acceleration data during the STS-75 mission in support of the third United States Microgravity Payload (USMP-3) experiments. The Orbital Acceleration Research Experiment (OARE) and the Space Acceleration Measurement System (SAMS) provided a measure of the microgravity environment of the Space Shuttle Columbia. The OARE provided investigators with quasi-steady acceleration measurements after about a six hour time lag dictated by downlink constraints. SAMS data were downlinked in near-real-time and recorded on-board for post-mission analysis. These two accelerometer systems are briefly described. Using a combination of data analysis techniques, the microgravity environment related to several different Orbiter, crew, and experiment operations is presented and interpreted. The microgravity environment represented by SAMS and OARE data is comparable to the environments measured by these instruments on earlier microgravity science missions. Thruster activity on this mission seen in the SAMS data appear to be more frequent than on other microgravity missions with the combined firings of the F5L and F5R jets producing significant acceleration transients. Of the events studied, the crew activities performed in the middeck and flight deck, SPREE table rotations, a waste collection system compaction, and a fuel cell purge had negligible effects on the microgravity environment of the USMP-3 carriers. The Ku band antenna repositioning activity resulted in a brief interruption of the ubiquitous 17 Hz signal in the SAMS data. In addition, the auxiliary power unit operations during the Flight Control System checkout appeared to have a significant impact on the microgravity environment.

Rogers, Melissa J. B.↗
NASA NTRS1997

Analyses of Technology for Solid State Coherent Lidar

Over past few years, considerable advances have been made in the areas of the diode-pumped, eye-safe, solid state lasers and room temperature, wide bandwidth, semiconductor detectors operating in the near-infrared region. These advances have created new possibilities for the development of reliable and compact coherent lidar systems for a wide range of applications. This research effort is aimed at further developing solid state coherent lidar technology for remote sensing of atmospheric processes such as wind, turbulence and aerosol concentration. The work performed by the UAH personnel under this Delivery Order concentrated on design and analyses of laboratory experiments and measurements, and development of advanced lidar optical subsystems in support of solid state laser radar remote sensing systems which are to be designed, deployed, and used to measure atmospheric processes and constituents. Under this delivery order, a lidar breadboard system was designed and analyzed by considering the major aircraft and space operational requirements. The lidar optical system was analyzed in detail using SYNOPSIS and Code V optical design packages. The lidar optical system include a wedge scanner and the compact telescope designed by the UAH personnel. The other major optical components included in the design and analyses were: polarizing beam splitter, routing mirrors, wave plates, signal beam derotator, and lag angle compensator. This lidar system is to be used for demonstrating all the critical technologies for the development of a reliable and low-cost space-based instrument capable of measuring global wind fields. A number of laboratory experiments and measurements were performed at the NASA/MSFC Detector Characterization Facility, previously developed by the UAH personnel. These laboratory measurements include the characterization of a 2-micron InGaAs detectors suitable for use in coherent lidars and characterization of Holographic Optical Element Scanners. UAH personnel actively participated in the development of performance and operational requirements for the development of the high pulse energy transmitter laser and frequency-agile local oscillator laser, that are in-progress at NASA Langley Research Center and Jet Propulsion Laboratory.

Amzajerdian, Farzin↗
NASA NTRS2003

Oil-Free Turbomachinery Research Enhanced by Thrust Bearing Test Capability

NASA Glenn Research Center s Oil-Free Turbomachinery research team is developing aircraft turbine engines that will not require an oil lubrication system. Oil systems are required today to lubricate rolling-element bearings used by the turbine and fan shafts. For the Oil-Free Turbomachinery concept, researchers combined the most advanced foil (air) bearings from industry with NASA-developed high-temperature solid lubricant technology. In 1999, the world s first Oil-Free turbocharger was demonstrated using these technologies. Now we are working with industry to demonstrate Oil-Free turbomachinery technology in a small business jet engine, the EJ-22 produced by Williams International and developed during Glenn s recently concluded General Aviation Propulsion (GAP) program. Eliminating the oil system in this engine will make it simpler, lighter (approximately 15 percent), more reliable, and less costly to purchase and maintain. Propulsion gas turbines will place high demands on foil air bearings, especially the thrust bearings. Up until now, the Oil-Free Turbomachinery research team only had the capability to test radial, journal bearings. This research has resulted in major improvements in the bearings performance, but journal bearings are cylindrical, and can only support radial shaft loads. To counteract axial thrust loads, thrust foil bearings, which are disk shaped, are required. Since relatively little research has been conducted on thrust foil air bearings, their performance lags behind that of journal bearings.

Bauman, Steven W.↗