Langley aerospace test highlights, 1985

The role of the Langley Research Center is to perform basic and applied research necessary for the advancement of aeronautics and space flight, to generate new and advanced concepts for the accomplishment of related national goals, and to provide research advice, technological support, and assistance to other NASA installations, other government agencies, and industry. Significant tests which were performed during calendar year 1985 in Langley test facilities, are highlighted. Both the broad range of the research and technology activities at the Langley Research Center and the contributions of this work toward maintaining United States leadership in aeronautics and space research, are illustrated. Other highlights of Langley research and technology for 1985 are described in Research and Technology-1985 Annual Report of the Langley Research Center

Sonic Booms in Atmospheric Turbulence (SonicBAT): The Influence of Turbulence on Shaped Sonic Booms

The objectives of the Sonic Booms in Atmospheric Turbulence (SonicBAT) Program were to develop and validate, via research flight experiments under a range of realistic atmospheric conditions, one numeric turbulence model research code and one classic turbulence model research code using traditional N-wave booms in the presence of atmospheric turbulence, and to apply these models to assess the effects of turbulence on the levels of shaped sonic booms predicted from low boom aircraft designs. The SonicBAT program has successfully investigated sonic boom turbulence effects through the execution of flight experiments at two NASA centers, Armstrong Flight Research Center (AFRC) and Kennedy Space Center (KSC), collecting a comprehensive set of acoustic and atmospheric turbulence data that were used to validate the numeric and classic turbulence models developed. The validated codes were incorporated into the PCBoom sonic boom prediction software and used to estimate the effect of turbulence on the levels of shaped sonic booms associated with several low boom aircraft designs. The SonicBAT program was a four year effort that consisted of turbulence model development and refinement throughout the entire period as well as extensive flight test planning that culminated with the two research flight tests being conducted in the second and third years of the program. The SonicBAT team, led by Wyle, includes partners from the Pennsylvania State University, Lockheed Martin, Gulfstream Aerospace, Boeing, Eagle Aeronautics, Technical & Business Systems, and the Laboratory of Fluid Mechanics and Acoustics (France). A number of collaborators, including the Japan Aerospace Exploration Agency, also participated by supporting the experiments with human and equipment resources at their own expense. Three NASA centers, AFRC, Langley Research Center (LaRC), and KSC were essential to the planning and conduct of the experiments. The experiments involved precision flight of either an F-18A or F-18B executing steady, level passes at supersonic airspeeds in a turbulent atmosphere to create sonic boom signatures that had been distorted by turbulence. The flights spanned a range of atmospheric turbulence conditions at NASA Armstrong and Kennedy in order to provide a variety of conditions for code validations. The SonicBAT experiments at both sites were designed to capture simultaneous F-18A or F-18B onboard flight instrumentation data, high fidelity ground based and airborne acoustic data, surface and upper air meteorological data, and additional meteorological data from ultrasonic anemometers and SODARs to determine the local atmospheric turbulence and boundary layer height

Aeronautical Engineering: A special bibliography with indexes, supplement 74

This special bibliography lists 295 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1976

Adaptation to transient postural perturbations

This research was first proposed in May, 1986, to focus on some of the problems encountered in the analysis of postural responses gathered from crewmembers. The ultimate driving force behind this line of research was the desire to treat, predict, or explain 'Space Adaptation Syndrome' (SAS) and hence circumvent any adverse effects of space motion sickness on crewmember performance. The aim of this project was to develop an easily implemented analysis of the transient responses to platform translation that can be elicited with a protocol designed to force sensorimotor reorganization, utilizing statistically reliable criterion measures. This report will present: (1) a summary of the activity that took place in each of the three funded years of the project; (2) discussion of experimental results and their implications for future research; and (3) a list of presentations and publications resulting from this project

US and USSR Military Aircraft and Missile Aerodynamics 1970-1980. A selected, annotated bibliography, volume 1

The purpose of this selected bibliography (281 citations) is to list available, unclassified, unlimited publications which provide aerodynamic data on major aircraft and missiles currently used by the military forces of the United States of America and the Union of Soviet Socialist Republics. Technical disciplines surveyed include aerodynamic performance, static and dynamic stability, stall-spin, flutter, buffet, inlets nozzles, flap performance, and flying qualities. Concentration is on specific aircraft including fighters, bombers, helicopters, missiles, and some work on transports, which are or could be used for military purposes. The bibliography is limited to material published from 1970 to 1980. The publications herein illustrate many of the types of aerodynamic data obtained in the course of aircraft development programs and may therefore provide some guidance in identifying problems to be expected in the conduct of such work. As such, this information may be useful in planning future research programs

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Dynamics of the Solar Magnetic Network. II. Heating the Magnetized Chromosphere

We consider recent observations of the chromospheric network, and argue that the bright network grains observed in the Ca II H & K lines are heated by an as yet unidentified quasi-steady process. We propose that the heating is caused by dissipation of short-period magnetoacoustic waves in magnetic flux tubes (periods less than 100 s). Magnetohydrodynamic (MHD) models of such waves are presented. We consider wave generation in the network due to two separate processes: (a) by transverse motions at the base of the flux tube; and (b) by the absorption of acoustic waves generated in the ambient medium. We find that the former mechanism leads to an efficient heating of the chromosphere by slow magnetoacoustic waves propagating along magnetic field lines. This heating is produced by shock waves with a horizontal size of a few hundred kilometers. In contrast, acoustic waves excited in the ambient medium are converted into transverse fast modes that travel rapidly through the flux tube and do not form shocks, unless the acoustic sources are located within 100 km from the tube axis. We conclude that the magnetic network may be heated by magnetoacoustic waves that are generated in or near the flux tubes.Comment: 30 pages, 8 figures, Accepted in Astrophysical Journa

Free-field propagation of high intensity noise

Observed spectral data from supersonic jet aircraft are known to contain much more high frequency energy than can be explained by linear acoustic propagation theory. It is believed that the high frequency energy is an effect of nonlinear distortion due to the extremely high acoustic levels generated by the jet engines. The objective, to measure acoustic waveform distortion for spherically diverging high intensity noise, was reached by using an electropneumatic acoustic source capable of generating sound pressure levels in the range of 140 to 160 decibels (re 20 micro Pa). The noise spectrum was shaped to represent the spectra generated by jet engines. Two microphones were used to capture the acoustic pressure waveform at different points along the propagation path in order to provide a direct measure of the waveform distortion as well as spectral distortion. A secondary objective was to determine that the observed distortion is an acoustic effect. To do this an existing computer prediction code that deals with nonlinear acoustic propagation was used on data representative of the measured data. The results clearly demonstrate that high intensity jet noise does shift the energy in the spectrum to the higher frequencies along the propagation path. In addition, the data from the computer model are in good agreement with the measurements, thus demonstrating that the waveform distortion can be accounted for with nonlinear acoustic theory

Development and Implementation of Mathematical Modeling, Vibration and Acoustic Emission Technique to Correlate \u3cem\u3eIn Vivo\u3c/em\u3e Kinematics, Kinetics and Sound in Total Hip Arthroplasty with Different Bearing Surfaces

The evaluation of Total Hip Arthroplasty (THA) outcome is difficult and invasive methods are often applied. Fluoroscopy has been used as an in vivo diagnostic technique to determine separation which may lead to vibration propagation and audible interactions. The objective of this study was to develop a new, non-invasive technique of digitally capturing vibration and sound emissions at the hip joint interface and to correlate those with the hip kinematics derived from fluoroscopy. Additionally, an examination of the role of hip mechanics on walking performance in THA subjects of various bearings surfaces was performed. In vivo kinematics, kinetics, corresponding vibration and sound measurements of THA were analyzed post-operatively using video-fluoroscopy, mathematical modeling, sound sensors and accelerometers during gait on a treadmill. Twenty-seven subjects (31 hips) with a metal-on-metal, metal-on-polyethylene, ceramic-on-ceramic, ceramicon- polyethylene or metal-on-metal polyethylene-sandwich THA were analyzed. A data acquisition system was used to amplify the signal and filter out associated frequencies attributed to noise. The sound measurements were correlated to in vivo kinematics. A mathematical model of the human extremity was derived to determine in vivo bearing and soft-tissue forces. For all bearings a distinct correlation of a high frequency sound occurring at the time when the femoral head slides back into the acetabular component was observed. Subjects having a hard-on-hard bearing seemed to attenuate a squeaking and/or impacting sound, while those having polyethylene liner only revealed a knocking sound attributed to impact loading conditions. For the first time, audible effects can be derived in vivo and the examined correlation brings valuable insight into the hip joint performance in an inexpensive and non-invasive manner. This research may allow for a further correlation to be derived between sound and different types of failure mechanisms. Results from this study will give surgeons and engineers a better understanding of in vivo mechanics of the hip joint and this way improve the quality of life of THA patients. In addition, the developed technique builds the first milestone in the design and implementation of a cost effective, non-invasive diagnostic technique which has the potential to become a routine diagnosis of joint conditions

Wind-induced drift of objects at sea: the leeway field method

A method for conducting leeway field experiments to establish the drift properties of small objects (0.1-25 m) is described. The objective is to define a standardized and unambiguous procedure for condensing the drift properties down to a set of coefficients that may be incorporated into existing stochastic trajectory forecast models for drifting objects of concern to search and rescue operations and other activities involving vessels lost at sea such as containers with hazardous material. An operational definition of the slip or wind and wave-induced motion of a drifting object relative to the ambient current is proposed. This definition taken together with a strict adherence to 10 m wind speed allows us to refer unambiguously to the leeway of a drifting object. We recommend that all objects if possible be studied using what we term the direct method, where the object's leeway is studied directly using an attached current meter. We divide drifting objects into four categories, depending on their size. For the smaller objects (less than 0.5 m), an indirect method of measuring the object's motion relative to the ambient current must be used. For larger objects, direct measurement of the motion through the near-surface water masses is strongly recommended. Larger objects are categorized according to the ability to attach current meters and wind monitoring systems to them. The leeway field method proposed here is illustrated with results from field work where three objects were studied in their distress configuration; a 1:3.3 sized model of a 40-ft Shipping container, a World War II mine and a 220 l (55-gallon) oil drum.Comment: 33 pages, 12 figures, 3 table