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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 109 records · Page 6
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NASA NTRS1987

Initial estimates of Venus winds from ground-based radio tracking of the Vega balloons

A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere by the Vega spacecraft. Initial analysis of only radial velocities indicates that each balloon was blown westward about 11,500 kilometers (8000 kilometers on the night side) by zonal winds with a mean speed of about 70 meters per second. Excursions of the data from a model of constant zonal velocity are generally less than 3-meters per second; however, a much larger variation is evident near the end of the flight of the second balloon. Consistent systematic trends in the residual for both balloons indicate the possibility of a solar-fixed atmospheric feature.

Preston, Robert A.↗
NASA NTRSDate not supplied

The Feasibility of Motion Tracking Camera System for Magnetic Suspension Wind Tunnel Tests

The Entry Systems Modeling (ESM) Program at NASA has actively participated in the re-development of the Magnetic Suspension Balance System (MSBS) at the six-inch subsonic wind tunnel at NASA Langley Research Center. This initiative aims to enhance the MSBS system's capabilities, enabling the testing of stingless entry vehicle models at supersonic speeds. To achieve this, control algorithms are required to ensure magnetic levitation control and stability for models during free-oscillation dynamic responses. Currently, the system relies on electromagnetic position sensors to provide real-time 3 degrees of freedom in a rigid body. While this approach has proven successful for subsonic speeds, expanding testing under higher pressure conditions may necessitate the incorporation of real-time roll and pitch measurements to quantify the dynamic stability characteristics of the models in free-oscillation. In collaboration with Old Dominion University, the team at NASA Langley Research Center proposes the implementation of a motion-tracking camera system. This system will provide real-time five degrees of freedom output, which will be utilized within a closed feedback control system and a two-step system identification model to isolate aerodynamic forces from their corresponding magnetic forces. The motion-tracking cameras will offer precise and accurate control over the levitation system, facilitating precise and repeatable experiments within the wind tunnel. The real-time feedback provided by the cameras enables prompt adjustments to ensure the maintenance of stable levitation throughout the testing process.

Entry Systems Modeling↗
NASA NTRSDate not supplied

The Feasibility of Motion Tracking Camera System for Magnetic Suspension Wind Tunnel Tests

The Entry Systems Modeling (ESM) Program at NASA has actively participated in the re-development of the Magnetic Suspension Balance System (MSBS) at the six-inch subsonic wind tunnel at NASA Langley Research Center. This initiative aims to enhance the MSBS system's capabilities, enabling the testing of stingless entry vehicle models at supersonic speeds. To achieve this, control algorithms are required to ensure magnetic levitation control and stability for models during free-oscillation dynamic responses. Currently, the system relies on electromagnetic position sensors to provide real-time 3 degrees of freedom in a rigid body. While this approach has proven successful for subsonic speeds, expanding testing under higher pressure conditions may necessitate the incorporation of real-time roll and pitch measurements to quantify the dynamic stability characteristics of the models in free-oscillation. In collaboration with Old Dominion University, the team at NASA Langley Research Center proposes the implementation of a motion-tracking camera system. This system will provide real-time five degrees of freedom output, which will be utilized within a closed feedback control system and a two-step system identification model to isolate aerodynamic forces from their corresponding magnetic forces. The motion-tracking cameras will offer precise and accurate control over the levitation system, facilitating precise and repeatable experiments within the wind tunnel. The real-time feedback provided by the cameras enables prompt adjustments to ensure the maintenance of stable levitation throughout the testing process.

Entry Systems Modeling↗
NASA NTRS1986

Determination of Venus winds by ground-based radio tracking of the VEGA balloons

A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere near Venus midnight by the VEGA spacecraft on 11 and 15 June 1985. Initial analysis of only radial velocities indicates that each balloon was blown westward about 11,500 kilometers (8,000 kilometers on the night side) by zonal winds with a mean speed of about 70 meters per second. Excursions of the data from a model of constant zonal velocity were generally less than 3 meters per second; however, a much larger variation was evident near the end of the flight of the second balloon. Consistent systematic trends in the residuals for both balloons indicate the possibility of a solar-fixed atmospheric feature. Rapid variations in balloon velocity were often detected within a single transmission (330 seconds); however, they may represent not only atmospheric motions but also self-induced aerodynamic motions of the balloon.

R A Preston↗
NASA NTRS2008

Atmospheric Dynamics of Titan

Titan. after Venus, is the second example of an atmosphere with a global cyclostrophic circulation in the solar system, but one with a strong seasonal modulation in the middle atmosphere. Direct measurement of Titan's winds, particularly observations tracking the Huygens probe at 10degS, indicate that the zonal winds are generally in the sense of the satellite's rotation. They become cyclostrophic approx.35 km above the surface and generally increase with altitude, with the exception of a sharp minimum centered near 75 km, where the wind velocity decreases to nearly zero. Zonal winds derived from the temperature field retrieved from Cassini measurements using the thermal wind equation, indicate a strong winter circumpolar vortex, with maximum winds of 190 m/s near 300 km at mid-northern latitudes. One of the most intriguing findings is that the pole of stratospheric temperatures and winds appears to be offset from the IAU definition of Titan's pole by approx. 4deg. The mean meridional circulation can be inferred from the temperature field, and the meridional distribution of organic molecules and condensates and hazes.

Flasar, F. Michael↗
NASA NTRS1996

Quality and Control of Water Vapor Winds

Water vapor imagery from the geostationary satellites such as GOES, Meteosat, and GMS provides synoptic views of dynamical events on a continual basis. Because the imagery represents a non-linear combination of mid- and upper-tropospheric thermodynamic parameters (three-dimensional variations in temperature and humidity), video loops of these image products provide enlightening views of regional flow fields, the movement of tropical and extratropical storm systems, the transfer of moisture between hemispheres and from the tropics to the mid- latitudes, and the dominance of high pressure systems over particular regions of the Earth. Despite the obvious larger scale features, the water vapor imagery contains significant image variability down to the single 8 km GOES pixel. These features can be quantitatively identified and tracked from one time to the next using various image processing techniques. Merrill et al. (1991), Hayden and Schmidt (1992), and Laurent (1993) have documented the operational procedures and capabilities of NOAA and ESOC to produce cloud and water vapor winds. These techniques employ standard correlation and template matching approaches to wind tracking and use qualitative and quantitative procedures to eliminate bad wind vectors from the wind data set. Techniques have also been developed to improve the quality of the operational winds though robust editing procedures (Hayden and Veldon 1991). These quality and control approaches have limitations, are often subjective, and constrain wind variability to be consistent with model derived wind fields. This paper describes research focused on the refinement of objective quality and control parameters for water vapor wind vector data sets. New quality and control measures are developed and employed to provide a more robust wind data set for climate analysis, data assimilation studies, as well as operational weather forecasting. The parameters are applicable to cloud-tracked winds as well with minor modifications. The improvement in winds through use of these new quality and control parameters is measured without the use of rawinsonde or modeled wind field data and compared with other approaches.

Jedlovec, Gary J.↗
NASA NTRS1994

Investigation of water vapor motion winds from geostationary satellites

Water vapor imagery from geostationary satellites has been available for over a decade. These data are used extensively by operational analysts and forecasters, mainly in a qualitative mode (Weldon and Holmes 1991). In addition to qualitative applications, motions deduced in animated water vapor imagery can be used to infer wind fields in cloudless regimes, thereby augmenting the information provided by cloud-drift wind vectors. Early attempts at quantifying the data by tracking features in water vapor imagery met with modest success (Stewart et al. 1985; Hayden and Stewart 1987). More recently, automated techniques have been developed and refined, and have resulted in upper-level wind observations comparable in quality to current operational cloud-tracked winds (Laurent 1993). In a recent study by Velden et al. (1993) it was demonstrated that wind sets derived from Meteosat-3 (M-3) water vapor imagery can provide important environmental wind information in data void areas surrounding tropical cyclones, and can positively impact objective track forecasts. M-3 was repositioned to 75W by the European Space Agency in 1992 in order to provide complete coverage of the Atlantic Ocean. Data from this satellite are being transmitted to the U.S. for operational use. Compared with the current GOES-7 (G-7) satellite (positioned near 112W), the M-3 water vapor channel contains a superior horizontal resolution (5 km vs. 16 km ). In this paper, we examine wind sets derived using automated procedures from both GOES-7 and Meteosat-3 full disk water vapor imagery in order to assess this data as a potentially important source of large-scale wind information. As part of a product demonstration wind sets were produced twice a day at CIMSS during a six-week period in March and April (1994). These data sets are assessed in terms of geographic coverage, statistical accuracy, and meteorological impact through preliminary results of numerical model forecast studies.

Velden, Christopher S.↗
NASA NTRS2000

Comparison of Three Wind Measuring Systems for Flight Test

A preliminary field test of the accuracy of wind velocity measurements obtained using global positioning system-tracked rawinsonde balloons has been performed. Wind comparisons have been conducted using global positioning system (GPS) and radio automatic theodolite sounder (RATS) rawinsondes and a high-precision range instrumentation radar-tracked reflector. Wind velocity differences between the GPS rawinsondes and the radar were significantly less than between the RATS rawinsondes and the radar. These limited test results indicate a root-mean-square wind velocity difference from 4.98 kn (2.56 m/sec) for the radar and RATS to 1.09 kn (0.56 m/sec) for the radar and GPS. Differences are influenced by user reporting requirements, data processing techniques, and the inherent tracking accuracies of the system. This brief field test indicates that the GPS sounding system tracking data are more precise than the RATS system. When high-resolution wind data are needed, use of GPS rawinsonde systems can reduce the burden on range radar operations.

Teets, Edward H., Jr.↗
NASA NTRS2000

Comparison of Three Wind Measuring Systems for Flight Test

A preliminary field test of the accuracy of wind velocity measurements obtained using global positioning system-tracked rawinsonde balloons has been performed. Wind comparisons have been conducted using global positioning system (GPS) and radio automatic theodolite sounder (RATS) rawinsondes and a high-precision range instrumentation radar-tracked reflector. Wind velocity differences between the GPS rawinsondes and the radar were significantly less than between the RATS rawinsondes and the radar. These limited test results indicate a root-mean-square wind velocity difference from 4.98 kn (2.56 m/sec) for the radar and RATS to 1.09 kn (0.56 m/sec) for the radar and GPS. Differences are influenced by user reporting requirements, data processing techniques, and the inherent tracking accuracies of the system. This brief field test indicates that the GPS sounding system tracking data are more precise than the RATS system. When high-resolution wind data are needed, use of GPS rawinsonde systems can reduce the burden on range radar operations.

Teets, Edward H., Jr.↗
NASA NTRSDate not supplied

Robust Path-following Controller for Multirotor Vehicles in Uncertain Wind Conditions

This paper presents simulations of L1 adaptive controller on a multirotor vehicle for compensation of convective winds. There are increasing efforts to utilize unmanned vehicles for fighting wildfires, but such vehicles need to be able to compensate for convective updrafts and other uncertainties (e.g., wind shear and turbulence) caused by the wildfire. Other application domains, such as urban air mobility, also must account for convective or uncertain winds present in urban microclimates. Geometric controllers have great tracking performance properties in environments without uncertainties, but the tracking performance degrades when wind disturbances and external loads are present in the environment. Introducing L1 adaptive control into the controller architecture compensates for these wind disturbances and reduces the tracking error caused by such disturbances. The controller architecture is implemented on a small quadrotor. The simulations demonstrate the advantages of the L1 adaptive augmentation for a sample figure-eight trajectory while encountering unknown variable wind conditions with an external load.

John L Bullock↗
NASA NTRSDate not supplied

Robust Path-following Controller for Multirotor Vehicles in Uncertain Wind Conditions

This paper presents simulations of L1 adaptive controller on a multirotor vehicle for compensation of convective winds. There are increasing efforts to utilize unmanned vehicles for fighting wildfires, but such vehicles need to be able to compensate for convective updrafts and other uncertainties (e.g., wind shear and turbulence) caused by the wildfire. Other application domains, such as urban air mobility, also must account for convective or uncertain winds present in urban microclimates. Geometric controllers have great tracking performance properties in environments without uncertainties, but the tracking performance degrades when wind disturbances and external loads are present in the environment. Introducing L1 adaptive control into the controller architecture compensates for these wind disturbances and reduces the tracking error caused by such disturbances. The controller architecture is implemented on a small quadrotor. The simulations demonstrate the advantages of the L1 adaptive augmentation for a sample figure-eight trajectory while encountering unknown variable wind conditions with an external load.

John Bullock↗
NASA NTRS1976

A comparison between Nimbus 5 THIR and ITPR temperatures and derived winds with rawinsonde data obtained in the AVE 2 experiment

During the period of May 11 and 12, 1974, NASA conducted its second Atmospheric Variability Experiment (AVE II) over the eastern United States. In this time interval, two Nimbus 5 orbits crossed the AVE II area, providing a series of ITPR soundings as well as THIR data. Horizontal temperature mapping of the AVE II cloud field is examined using two grid print map scales. Implied cloud top heights are compared with maximum radar-echo top reports. In addition, shelter temperatures in areas of clear sky are compared with the surface temperatures as determined from 11.5 micrometer radiometer data of the THIR experiment. The ITPR sounding accuracy is evaluated using interpolated radiosonde temperatures at times nearly coincident with the ITPR soundings. It was found that mean differences between the two data sets were as small as 1.3 C near 500 mb and as large as 2.9 C near the tropopause. The differences between ITPR and radiosonde temperatures at constant pressure levels were sufficient to induce significant differences in the horizontal temperature gradient. Cross sections of geostrophic wind along the orbital tracks were developed using a thermal wind buildup based on the ITPR temperature data and the radiosonde temperature data. Differences between the radiosonde and ITPR geostrophic winds could be explained on the basis of differences in the ITPR and radiosonde temperature gradients.

Arnold, J. E.↗
NASA NTRS1978

The benefits of using short interval satellite images to derive winds for tropical cyclones

During the 1975, 1976, and 1977, NOAA's National Environmental Satellite Service and NASA's Goddard Space Flight Center conducted a cooperative program to determine the optimum resolution and frequency of satellite images for deriving winds to study and forecast tropical cyclones. Rapid scan images were obtained at 7.5 minute interval from SMS-2 for hurricane Eloise and cyclone Caroline, and at 3 minute intervals from GOES-1 for tropical storms Belle, Holly, and Anita. Cloud motions were derived from these images using the Atmospheric and Oceanographic Information Processing System. Winds that were derived from the movement of upper and lower tropospheric level clouds using rapid scan data were compared with the 15 and 30 minute interval data. Greater than 10 (5) times as many clouds could be tracked to obtain winds using 3 and 7.5 minute rapid scan images as when using 15 or 30 minute interval images. A few bright areas within the central dense overcast which appeared to be moving with the winds at low levels were tracked.

Rodgers, E.↗
NASA NTRS2001

Galileo Probe Doppler Residuals as the Wave-Dynamical Signature of Weakly Stable, Downward-Increasing Stratification in Jupiter's Deep Wind Layer

Doppler radio tracking of the Galileo probe-to-orbiter relay, previously analyzed for its in situ measure of Jupiter's zonal wind at the equatorial entry site, also shows a record of significant residual fluctuations apparently indicative of varying vertical motions. Regular oscillations over pressure depth in the residual Doppler measurements of roughly 1-8 Hz (increasing upward), as filtered over a 134 sec window, are most plausibly interpreted as gravity waves, and imply a weak, but downward increasing static stability within the 5 - 20 bar region of Jupiter's atmosphere. A matched extension to deeper levels of an independent inertial stability constraint from the measured vertical wind shear at 1 - 4 bars is roughly consistent with a static stability of approximately 0.5 K/km near the 20 bar level, as independently detected by the probe Atmospheric Structure Instrument.

Allison, Michael↗
NASA NTRS2013

Adaptive Disturbance Tracking Theory with State Estimation and State Feedback for Region II Control of Large Wind Turbines

A theory called Adaptive Disturbance Tracking Control (ADTC) is introduced and used to track the Tip Speed Ratio (TSR) of 5 MW Horizontal Axis Wind Turbine (HAWT). Since ADTC theory requires wind speed information, a wind disturbance generator model is combined with lower order plant model to estimate the wind speed as well as partial states of the wind turbine. In this paper, we present a proof of stability and convergence of ADTC theory with lower order estimator and show that the state feedback can be adaptive.

Balas, Mark J.↗
NASA NTRS1977

Automatic flight performance of a transport airplane on complex microwave landing system paths

Essential characteristics of the U.S. microwave landing system (MLS) and the TCV B-737 aircraft used in flight demonstrations are described, with special emphasis on the analysis of the approach paths. MLS is used to provide the aircraft with guidance for automatic control on complex, curved descending paths with precision turns into short final approaches terminating in landing and rollout, even when subjected to strong and gusty tail- and cross-wind components and severe wind shear. The tracking performance achieved on these paths under MLS guidance is examined in detail, and the wind environment where the flights are conducted are quantified. The flights demonstrate the utility of the wide-area coverage of MLS for curved, descending paths commencing with a standard RNAV approach into a terminal area and continuation of this approach throughout the MLS coverage and onto the runway.

Walsh, T. M.↗