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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

A decade of aeroacoustic research at NASA Ames Research Center

The rotorcraft aeroacoustic research accomplishments of the past decade at Ames Research Center are reviewed. These include an extensive sequence of flight, ground, and wind tunnel tests that have utilized the facilities to guide and pioneer theoretical research. Many of these experiments were of benchmark quality. The experiments were used to isolate the inadequacies of linear theory in high-speed impulsive noise research, have led to the development of theoretical approaches, and have guided the emerging discipline of computational fluid dynamics to rotorcraft aeroacoustic problems.

Schmitz, Frederic H.↗
NASA NTRS1988

NASA Ames Summer High School Apprenticeship Research Program: 1986 research papers

Engineering enrollments are rising in universities; however the graduate engineering shortage continues. Particularly, women and minorities will be underrepresented for many years. As one means of solving this shortage, Federal agencies facing future scientific and technological challenges were asked to participate in the Summer High School Apprenticeship Research Program (SHARP). This program was created to provide an engineering experience for gifted female and minority high school students at an age when they could still make career and education decisions. The SHARP program is designed for high school juniors who are U.S. citizens, are 16 years old, and who have very high promise in math and science through outstanding academic performance in high school. Students who are accepted into this summer program will earn as they learn by working 8 hr days in a 5-day work week. Reports from SHARP students are presented.

Powell, Patricia↗
NASA NTRS1990

Photonic processing at NASA Ames Research Center

The Photonic Processing group is engaged in applied research on optical processors in support of the Ames vision to lead the development of autonomous intelligent systems. Optical processors, in conjunction with numeric and symbolic processors, are needed to provide the powerful processing capability that is required for many future agency missions. The research program emphasizes application of analog optical processing, where free-space propagation between components allows natural implementations of algorithms requiring a large degree of parallel computation. Special consideration is given in the Ames program to the integration of optical processors into larger, heterogeneous computational systems. Demonstration of the effective integration of optical processors within a broader knowledge-based system is essential to evaluate their potential for dependable operation in an autonomous environment such as space. The Ames Photonics program is currently addressing several areas of interest. One of the efforts is to develop an optical correlator system with two programmable spatial light modulators (SLMs) to perform distortion invariant pattern recognition. Another area of research is optical neural networks, also for use in distortion-invariant pattern recognition.

Ochoa, Ellen↗
NASA NTRS1989

The Life Sciences program at the NASA Ames Research Center - An overview

The research projects planned for the Life Sciences program have a goal of answering basic questions concerning the nature of life itself and its evolution in the universe from basic elements, as well as the search for extraterrestrial intelligence. The program also includes studies of the evolution and development of life on the planet earth, and the global changes occurring today that affect life on the earth. The paper describes the simulation models developed to study the effects of space, the flight projects of the program, and the biomedical program, which currently focuses on the physiological changes in the human body that are associated with space flights and the interactions among these changes.

Vernikos-Danellis, Joan↗
NASA NTRS1989

Computational fluid dynamics at NASA Ames Research Center

Computational fluid dynamics (CFD) has made great strides in the detailed simulation of complex fluid flows, including the fluid physics of flows heretofore not understood. It is now being routinely applied to some rather complicated problems, and starting to impact the design cycle of aerospace flight vehicles and their components. In addition, it is being used to complement, and is being complemented by, experimental studies. In the present paper, some major elements of contemporary CFD research, such as code validation, turbulence physics, and hypersonic flows are discussed, along with a review of the principal pacing items that currently govern CFD. Several examples of pioneering CFD research are presented to illustrate the current state of the art. Finally, prospects for the future development and application of CFD are suggested.

Kutler, Paul↗
NASA NTRS1990

Development of non-intrusive instrumentation for NASA-Ames Ballistic Range and Shock Tunnel

The use of nonintrusive instrumentation in high-enthalpy facilities offers the opportunity to collect data that has previously been difficult or impossible to obtain. Three such instruments, now under development, are described: an OH absorption system which can measure OH species concentration and temperature, a holographic interferometer for flow visualization and density measurement at low density, and a telemetry system which allows the measurement of surface quantities on model in free-flight at hypervelocity. The challenges and opportunities encountered when employing these advanced diagnostics to high-enthalpy facilities are discussed.

Strawa, A. W.↗
NASA NTRS1989

Exobiology in Earth orbit: The results of science workshops held at NASA, Ames Research Center

The Workshops on Exobiology in Earth Orbit were held to explore concepts for orbital experiments of exobiological interest and make recommendations on which classes of experiments should be carried out. Various observational and experimental opportunities in Earth orbit are described including those associated with the Space Shuttle laboratories, spacecraft deployed from the Space Shuttle and expendable launch vehicles, the Space Station, and lunar bases. Specific science issues and technology needs are summarized. Finally, a list of recommended experiments in the areas of observational exobiology, cosmic dust collection, and in situ experiments is presented.

Defrees, D.↗
NASA NTRS1991

Holographic interferometry at the NASA-Ames Hypervelocity Free-Flight Aerodynamic Facility

A laser holographic interferometer has been designed and developed to improve flow visualization for models in free-flight at high velocities and low freestream static pressures. Of special interest is the flow structure due to high-temperature effects in the post-shock region of models traveling at hypervelocity. A dual-plate technique with a double-pass, Michelson-type configuration has been incorporated in an existing hypervelocity ballistic range. Holograms of 5-deg blunt conical models traveling at 5 km/sec in air at a freestream static pressure of 0.08 atm have been made. Finite- and infinite-fringe interferograms were reconstructed from the holograms and provided qualitative flowfield results. In addition, a digital scanning technique was also used to produce a 'synthetic' infinite-fringe interferogram from the analysis of an experimental finite-fringe interferogram. A 'synthetic' infinite-fringe interferogram shows detail in the wake region not found in the experimental interferograms.

Tam, Tim C.↗
NASA NTRS1991

Two-dimensional adaptive-wall tests in the NASA Ames two- by two-foot transonic wind tunnel

The first tests conducted in the adaptive-wall test section of the Ames Research Center's 2- by 2-Foot Transonic Wind Tunnel are described. A procedure was demonstrated for reducing wall interference in transonic flow past a two-dimensional airfoil by actively controlling flow through the slotted walls of the test section. Flow through the walls was controlled by adjusting pressures in compartments of plenums above and below the test section. Wall interference was assessed by measuring (with a laser velocimeter) velocity distributions along a contour surrounding the model, and then checking those measurements for their compatibility with free-air far-field boundary conditions. Plenum pressures for minimum wall interference were determined from empirical influence coefficients. An NACA 0012 airfoil was tested at angles of attack of 0 and 2, and at Mach numbers between 0.70 and 0.85. In all cases the wall-setting procedure greatly reduced wall interference. Wall interference, however, was never completely eliminated, primarily because the effect of plenum pressure changes on the velocities along the contour could not be accurately predicted.

Schairer, Edward T.↗
NASA NTRS1993

Thermal protection materials at NASA Ames Research Center

The topics addressed are: (1) Space Exploration Initiative (SEI); (2) Aeroassist Flight Experiment (AFE); (3) Mars Environmental Survey (MESUR); (4) National Aero-space Plan (NASP); (5) Pegasus and Pegasus/SWERVE Hypersonic Testing; and (6) Personnel Launch System TPS evaluation.

Rasky, Daniel J.↗
NASA NTRS1993

Mars atmospheric dynamics as simulated by the NASA Ames General Circulation Model. I - The zonal-mean circulation

The characteristics of the zonal-mean circulation and how it responds to seasonal variations and dust loading are described. This circulation is the main momentum-containing component of the general circulation, and it plays a dominant role in the budgets of heat and momentum. It is shown that in many ways the zonal-mean circulation on Mars, at least as simulated by the model, is similar to that on earth, having Hadley and Ferrel cells and high-altitude jet streams. However, the Martian systems tend to be deeper, more intense, and much more variable with season. Furthermore, the radiative effects of suspended dust particles, even in small amounts, have a major influence on the general circulation.

Haberle, Robert M.↗
NASA NTRS1993

Performance results from a test of an S-76 rotor in the NASA Ames 80- by 120-foot wind tunnel

A full-scale helicopter rotor wind tunnel test has been conducted which covers a wide range of rotor-shaft angles-of-attack and 0-100 kt thrust conditions. The hover performance data thus obtained were compared with the results of momentum theory calculations; forward flight rotor-performance data were compared with calculations from a comprehensive rotorcraft analysis. These comparisons suggest that hover testing at an outdoor facility in the absence of ground effect is required to make a final determination of the absolute accuracy of the wind tunnel hover data.

Shinoda, Patrick M.↗
NASA NTRS1977

Automatic speech recognition research at NASA-Ames Research Center

A trainable acoustic pattern recognizer manufactured by Scope Electronics is presented. The voice command system VCS encodes speech by sampling 16 bandpass filters with center frequencies in the range from 200 to 5000 Hz. Variations in speaking rate are compensated for by a compression algorithm that subdivides each utterance into eight subintervals in such a way that the amount of spectral change within each subinterval is the same. The recorded filter values within each subinterval are then reduced to a 15-bit representation, giving a 120-bit encoding for each utterance. The VCS incorporates a simple recognition algorithm that utilizes five training samples of each word in a vocabulary of up to 24 words. The recognition rate of approximately 85 percent correct for untrained speakers and 94 percent correct for trained speakers was not considered adequate for flight systems use. Therefore, the built-in recognition algorithm was disabled, and the VCS was modified to transmit 120-bit encodings to an external computer for recognition.

Coler, Clayton R.↗
NASA NTRS1994

NASA Ames Fluid Mechanics Laboratory research briefs

The Ames Fluid Mechanics Laboratory research program is presented in a series of research briefs. Nineteen projects covering aeronautical fluid mechanics and related areas are discussed and augmented with the publication and presentation output of the Branch for the period 1990-1993.

Davis, Sanford↗
NASA NTRS1995

Application of CFD in aeronautics at NASA Ames Research Center

The role of Computational Fluid Dynamics (CFD) at Ames Research Center has expanded to address a broad range of aeronautical problems, including wind tunnel support, flight test support, design, and analysis. Balancing the requirements of each new problem against the available resources - software, hardware, time, and expertise - is critical to the effective use of CFD. Several case studies of recent applications highlight the depth of CFD capability at Ames, the tradeoffs involved in various approaches, and lessons learned in the use of CFD as an engineering tool.

Maksymiuk, Catherine M.↗
NASA NTRS1997

Characteristics of the NASA-Ames Laminar Flow Supersonic Wind Tunnel for Unique Mach 1.6 Transition Studies

Flow quality measurements have been performed in the unique Laminar Flow Supersonic Wind Tunnel (LFSWT) to examine both mean and dynamic characteristics. The intent was to provide the necessary flow information about this ground test facility, to support meaningful transition research at Mach 1.6 and flight unit Reynolds numbers. This paper is intended to assist other experimentalists with similar goals of characterizing low-supersonic test environments. An array of instrumentation has been used to highlight the importance of proper selection of pressure instruments and data acquisition procedures. We conclude that the test section is low-disturbance (based on classical standards of pressure disturbances less than 0.1% with no specified data bandwidth), and has uniform flow. This is confirmation that the quiet design features of the LFSWT are effective. However, characterization of the test section flow over a 0.25k-5Ok bandwidth shows that the disturbance levels can be greater than classical standards particularly for stagnation pressures less than 9.5 psia (0.65 bar) with low stagnation temperatures. Variability of the flow disturbances in the settling chamber and test section is contained in a narrow frequency bandwidth below 5k Hz, which is associated with resonant frequencies from the pressure reduction system. So far, these disturbances have not impacted transition along the tunnel walls or a 10 degrees cone. However, continual vigilance is required to maintain a known low-disturbance environment for transition research in the LFSWT. Furthermore, the formation of standards for flow quality measurements is strongly recommended, so that transition research can be better isolated from tunnel disturbances.

Wolf, Stephen W. D.↗