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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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NASA NTRS1992

Measuring ionospheric electron density using the plasma frequency probe

During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes.

Jensen, Mark D.↗

DOE OSTI2023

Predictive understanding of the surface tension and velocity of sound in ionic liquids using machine learning

Knowledge of the physical properties of ionic liquids (ILs), such as the surface tension and speed of sound, is important for both industrial and research applications. Unfortunately, technical challenges and costs limit exhaustive experimental screening efforts of ILs for these critical properties. Previous work has demonstrated that the use of quantum-mechanics-based thermochemical property prediction tools, such as the conductor-like screening model for real solvents, when combined with machine learning (ML) approaches, may provide an alternative pathway to guide the rapid screening and design of ILs for desired physiochemical properties. However, the question of which machine-learning approaches are most appropriate remains. In the present study, we examine how different ML architectures, ranging from tree-based approaches to feed-forward artificial neural networks, perform in generating nonlinear multivariate quantitative structure–property relationship models for the prediction of the temperature- and pressure-dependent surface tension of and speed of sound in ILs over a wide range of surface tensions (16.9–76.2 mN/m) and speeds of sound (1009.7–1992 m/s). The ML models are further interrogated using the powerful interpretation method, shapley additive explanations. We find that several different ML models provide high accuracy, according to traditional statistical metrics. The decision tree-based approaches appear to be the most accurate and precise, with extreme gradient-boosting trees and gradient-boosting trees being the best performers. However, our results also indicate that the promise of using machine-learning to gain deep insights into the underlying physics driving structure–property relationships in ILs may still be somewhat premature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1998

Sounding Rocket

This project has resulted in 4 launches from the White Sands Missile Range of our payload in different stages of development, on: (1) 4 May 1991 Flight 36.062; (2) 16 June 1993 Flight 36.101; (3) 1 April 1995 Flight 36.104; and (5) 28 October 1996 Flight 36.149. For each flight, the following activities were accomplished: (1) prepare the experiment, including replacement and upgrading of critical components, at the University of Michigan; (2) integrate the payload either at the Wallops Flight Facility; (3) perform final far-UV calibration of instrument; (4) perform final alignment, integration, and electrical checks at WSMR (5) launch payload from WSMR (6) check condition of recovered payload (7) perform post-flight calibration, if necessary and applicable; and (8) reduce and analyze flight data. A description of the instrument is presented, along with overviews of the results of the four flights. We are presently preparing the payload for the next flight in 1998/99.

Clarke, John T.↗

NASA NTRS1973

Noise comparisons from full-scale fan tests at NASA Lewis Research Center.

The overall aero and acoustic design features of eight 6-foot-diameter, single-stage fans tested in an outdoor acoustic facility are described. A correlation of the acoustic results for subsonic tip-speed fans showed the total sound power to be proportional to the mechanical power imparted to the fan and the specific work performed on the air to within plus or minus 2 dB. The correlation was relatively insensitive to fan design variables over a broad range of operating conditions. Maximum perceived noise levels were generally proportional to the sound power levels with both noise levels exhibiting a relatively unique increase with fan pressure ratio when normalized by the delivered thrust. The spectra of broadband noise attributed to the fan exhibited a bimodal characteristic for most of the fans. A predominant mode centered near the blade-passage tone and another at 8 to 16 times the tone frequency.

Heidmann, M. F.↗

NASA NTRS2000

Examining INM Accuracy Using Empirical Sound Monitoring and Radar Data

Aircraft noise measurements were made using noise monitoring systems at Denver International and Minneapolis St. Paul Airports. Measured sound exposure levels for a large number of operations of a wide range of aircraft types were compared with predictions using the FAA's Integrated Noise Model. In general it was observed that measured levels exceeded the predicted levels by a significant margin. These differences varied according to the type of aircraft and also depended on the distance from the aircraft. Many of the assumptions which affect the predicted sound levels were examined but none were able to fully explain the observed differences.

Miller, Nicholas P.↗

NASA NTRS1972

Wind velocity profiles measured by the smoke-trail method at Wallops Island, Virginia, 1965 - 1969

Thirty-nine detailed wind profiles measured by the smoke-trail method at the Wallops Island Test Range during the years 1965 through 1969 are presented as west-to-east and south-to-north velocity components at height intervals of 25 meters. The overall altitude range of the wind profile data varies from about 1 to 23 km. The wind measurements, which were made under a variety of conditions, include velocities in excess of the annual 99-percent highest wind value (the wind value which will not be exceeded 99 percent of the time) for the Wallops Island Test Range. The report also includes a listing of the wind soundings and their maximum velocities and direction of the maximum velocities measured at Wallops Island from 1959 through 1969. Results of smoke-trail enhancement experiments are also indicated.

Rhyne, R. H.↗

NASA NTRS1972

A program of high resolution X-ray astronomy using sounding rockets

Two Aerobee 170 sounding rocket payloads were flown at the White Sands Missile Range: (1) a focusing X-ray collector on 31 March 1972; and (2) a high resolution telescope on 4 August 1972. Data has been reduced from each of these flights. In the first flight both the rocket and the experiment instrumentation performed adequately, and it is clear that at least the minimum scientific objectives were attained. In the second flight the attitude control system failed to point the telescope at the target for a sufficient length of time. However examination of final preflight checkout data and some flight data indicate that the instrumentation for this rocket payload was functioning according to expectations.

Source record↗

NASA NTRS1972

Subsonic and supersonic jets and supersonic suppressor characteristics

Convergent and parallel flow nozzles were used with room temperature air to investigate the flow and acoustic characteristics over a Mach number range of 0.6 to 1.5. For subsonic jets the maximum sound pressure levels occurred at 19.1 from the axis and the sound pressure level decreased monotonically with increasing angle. But for supersonic jets the sound pressure was nearly constant over most of angular positions. The power spectra for subsonic jets were similar with the peak occurring at 4 KHz and for a Mach 1.4 jet the peak occurred at 5 KHz. Near field sound pressure level distributions were quite similar for subsonic jets, but for supersonic jets the distributions were quite different. Mean and fluctuating velocity contours were determined for a convergent nozzle with the impact and piezoelectric impact pressure gage probes for Mach numbers of 0.6 to 1.4. A supersonic suppressor of 191 tubes and shrouds was investigated at Mach numbers of 1.4 and 0.7.

Nagamatsu, H. T.↗

NASA NTRS1981

A wide-field soft X-ray camera

A wide-field soft X-ray camera (WFSXC) sensitive in the 50 to 250 eV band is described. The camera features Wolter-Schwarzschild optics with an 8 degree field of view and 300 cu cu collecting area. The focal plane instrument is a microchannel plate detector. Broad-band energy discrimination is provided by thin-film filters mounted immediately in front of the focal plane. The WFSXC is capable of detecting sources with intensities greater than 5 percent of HZ 43 during typical sounding rocket exposures, and it would approach the same sensitivity range as EUVE during a typical exposure from the Shuttle.

Petre, R.↗

NASA NTRS1982

Evaluation of the user requirements processes for NASA terrestrial applications programs

To support the evolution of increasingly sound user requirements definition processes that would meet the broad range of NASA's terrestrial applications planning and management needs during the 1980's, the user requirements processes as they function in the real world at the senior and middle management levels were evaluated. Special attention was given to geologic mapping and domestic crop reporting to provide insight into problems associated with the development and management of user established conventional practices and data sources. An attempt was made to identify alternative NASA user interfaces that sustain strengths, alleviate weaknesses, maximize application to multiple problems, and simplify management cognizance. Some of the alternatives are outlined and evaluated. It is recommended that NASA have an identified organizational point of focus for consolidation and oversight of the user processes.

Source record↗

NASA NTRS1982

Mechanics aspects of NDE by sound and ultrasound

Nondestructive evaluation (NDE) is considered as a means to detect the energy release mechanism of defects and the interaction of microstructures within materials with sound waves and/or ultrasonic waves. Ultrasonic inspection involves the frequency range 20 kHz-1 GHz with amplitudes depending on the sensitivity of the test instrumentation. Pulse echo systems are most frequently used in NDE. Information is extracted from the signals through measurements of the signal velocity, attenuation, the acoustic emission when stress is applied, and calculation of the acoustoelastic coefficients. Fracture properties, tensile and shear strengths, the interlaminar shear strength, the cohesive strength, yield and impact strengths, the hardness, and the residual stress can be assayed by ultrasonic methods. Finally, attention is given to analytical treatment of the derived data, with mention given to transition matrix, integral equation, and eigenstrain approaches.

Fu, L. S.↗

NASA NTRS1983

McIDAS III - A modern interactive data access and analysis system

A powerful facility for meteorological analysis called the Man Computer Interactive Data Access System (McIDAS) was designed and implemented in the early 1970's at the Space Science and Engineering Center of the University of Wisconsin-Madison. Hardware and software experience gained via extensive use of that facility and its derivatives have led to a newer implementation of McIDAS on a larger computer with significant enhancements to the supporting McIDAS software. McIDAS allows remote and local access to a wide range of data from satellites and conventional observations, time lapse displays of imagery data, overlaid graphics, and current and past meteorological data. Available software allows one to perform analysis of a wide range of digital images as well as temperature and moisture sounding data obtained from satellites. McIDAS can generate multicolor composites of conventional and satellite weather data, radar and forecast data in a wide variety of two- and three-dimensional displays as well as time lapse movies of these analyses. These and other capabilities are described in this paper.

Suomi, V. E.↗

NASA NTRS1989

Experimental assessment of helicopter rotor turbulence ingestion noise in hover

An experiment was conducted to assess the accuracy of a theory for non-isotropic turbulence ingestion. In order to generate non-isotropic turbulence in a controlled environment, a scale model rotor in a closed chamber was used so that the turbulence generated by the rotor was reingested by the recirculating flow. Simultaneous measurements of turbulence inflow properties and far field acoustics were acquired. Measurements confirmed that the inflow turbulence was highly non-isotropic. The measured aerodynamic properties were used as inputs for the noise prediction procedure. The general agreement between the non-isotropic noise prediction procedure and the experiment was good, although the procedure generally overpredicts the quasi-tonal low to mid range frequencies and underpredicts the higher broadband signals. The predicted sound power level as a function of polar angle was in close agreement with measurements, except near the rotor plane, which is not modeled by the present analysis. It is determined that the most sensitive parameter influencing the predicted noise was the turbulence intensity.

Simonich, J. C.↗

NASA NTRS1988

Aerosol backscatter variability at 10.6 microns over Colorado high plains during JAWS experiment

This paper describes the aerosol backscatter profile measurements obtained by an airborne CW focused CO2 Doppler lidar (the Laser True Airspeed System) during the 1982 Joint Airport Weather Studies (JAWS) field experiment. The backscatter sounding flights were made in the lee of the front range of the Colorado Rocky Mountains, at about 1650 m above mean sea level. The qualitative relationships between the backscatter and the vertical distribution of temperature and water vapor are described.

Rothermel, Jeffry↗

NASA NTRS1989

Plasma properties of hot coronal loops utilizing coordinated SMM and solar research rocket observations

Three improvements in photographic x-ray imaging techniques for solar astronomy are presented. The testing and calibration of a new film processor was conducted; the resulting product will allow photometric development of sounding rocket flight film immediately upon recovery at the missile range. Two fine grained photographic films were calibrated and flight tested to provide alternative detector choices when the need for high resolution is greater than the need for high sensitivity. An analysis technique used to obtain the characteristic curve directly from photographs of UV solar spectra were applied to the analysis of soft x-ray photographic images. The resulting procedure provides a more complete and straightforward determination of the parameters describing the x-ray characteristic curve than previous techniques. These improvements fall into the category of refinements instead of revolutions, indicating the fundamental suitability of the photographic process for x-ray imaging in solar astronomy.

Moses, J. Daniel↗

NASA NTRS1990

Segmentation, modeling and classification of the compact objects in a pile

The problem of interpreting dense range images obtained from the scene of a heap of man-made objects is discussed. A range image interpretation system consisting of segmentation, modeling, verification, and classification procedures is described. First, the range image is segmented into regions and reasoning is done about the physical support of these regions. Second, for each region several possible three-dimensional interpretations are made based on various scenarios of the objects physical support. Finally each interpretation is tested against the data for its consistency. The superquadric model is selected as the three-dimensional shape descriptor, plus tapering deformations along the major axis. Experimental results obtained from some complex range images of mail pieces are reported to demonstrate the soundness and the robustness of our approach.

Gupta, Alok↗

NASA NTRS1995

Flight safety programs and enhancements for sounding rockets at Wallops Flight Facility

Sounding rocket programs are becoming larger and more complex, thus range safety personnel are required to be central to vehicle and mission design and operations planning. In response to this, the Wallops Flight Facility (VA), is upgrading range facilities, tracking systems, mobile systems and real-time safety systems. These enhancements will improve safety and reliability while augmenting mission success. Flight safety requirements and responsibilities are summarized, and the range safety's future upgrades for wind weighting, real-time analysis and displays, and the mobile safety systems for rocket programs, are considered.

Balach, Dean↗

NASA NTRS2011

Aeroacoustic Characterization of the NASA Ames Experimental Aero-Physics Branch 32- by 48-Inch Subsonic Wind Tunnel with a 24-Element Phased Microphone Array

The Aero-Physics Branch at NASA Ames Research Center utilizes a 32- by 48-inch subsonic wind tunnel for aerodynamics research. The feasibility of acquiring acoustic measurements with a phased microphone array was recently explored. Acoustic characterization of the wind tunnel was carried out with a floor-mounted 24-element array and two ceiling-mounted speakers. The minimum speaker level for accurate level measurement was evaluated for various tunnel speeds up to a Mach number of 0.15 and streamwise speaker locations. A variety of post-processing procedures, including conventional beamforming and deconvolutional processing such as TIDY, were used. The speaker measurements, with and without flow, were used to compare actual versus simulated in-flow speaker calibrations. Data for wind-off speaker sound and wind-on tunnel background noise were found valuable for predicting sound levels for which the speakers were detectable when the wind was on. Speaker sources were detectable 2 - 10 dB below the peak background noise level with conventional data processing. The effectiveness of background noise cross-spectral matrix subtraction was assessed and found to improve the detectability of test sound sources by approximately 10 dB over a wide frequency range.

Costanza, Bryan T.↗