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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Absolute intensity measurements of the CO2 bands 401-III /backward arrow/ 000 and 411-III /backward arrow/ 010

The absolute intensities of the studied transitions of CO2 have been measured from spectra obtained under high resolution. Vibration-rotation line intensities and integrated band intensities are reported. The studied bands are characterized by origins at 7593.5 and 7584 cm to the minus 1. Spectra were obtained by an Ames' 25-m base path White-type absorption cell equipped with silver-coated mirrors together with a 5-m focal length Czerny-Turner scanning spectrometer. The procedures for calculating the widths and intensities are explained, and uncertainty limits of the reported values are considered.

Valero, F. P. J.↗
NASA NTRS1978

Development of flightweight static face seals for 75.84 MPa /11 000 psi/ pressure and cryogenic temperatures

The development of a static seal configuration to meet the lightweight low-leakage requirements of the Space Shuttle Main Engine (pressure carrying capability of up to 75.84 MPa) is discussed. The design features, fabrication methods, lab testing, and performance of seal are examined. Flange and bolt details of the joint assembly are considered with attention to an ultrasonic technique for measuring preload in the bolts. Methods used for leak testing in the laboratory and in the field are described; the practicality of the procedures is considered. Attention is directed to hydrogen-environment embrittlement and its influence on seal and joint design.

Daniels, C. M.↗
NASA NTRS1978

The application of hydraulics in the 2,000 kW wind turbine generator

A 2000 kW turbine generator using hydraulic power in two of its control systems is being built under the management of NASA Lewis Research Center. The hydraulic systems providing the control torques and forces for the yaw and blade pitch control systems are discussed. The yaw-drive-system hydraulic supply provides the power for positioning the nacelle so that the rotary axis is kept in line with the direction of the prevailing wind, as well as pressure to the yaw and high speed shaft brakes. The pitch-change-mechanism hydraulic system provides the actuation to the pitch change mechanism and permits feathering of the blades during an emergency situation. It operates in conjunction with the overall windmill computer system, with the feather control permitting slewing control flow to pass from the servo valve to the actuators without restriction.

Onufreiczuk, S.↗
NASA NTRS1979

Analysis of population mortality kinetics with application to the longevity followup of the Navy's '1,000 aviators'

A simple physiological model of mortality kinetics is used to assess the intuitive concept that the aging rates of populations are proportional to their mortality rates. It is assumed that the vitality of an individual can be expressed as a simple summation of the weighted functional capacities of its organs and homeostatic systems that are indispensable for survival. It is shown that the mortality kinetics of a population can be derived by a linear transformation of the frequency distribution of vitality, assuming a uniform constant rate of decline of the physiological functions. A simple comparison of two populations is not possible when they have different vitality frequency distributions. Analysis of the data using the model suggests that the differences in decline of survivorship with age between the military pilot population, a medically insured population, and the control population can be accounted for by the effect of physical selection on the vitality frequency distribution of the screened populations.

Economos, A. C.↗
NASA NTRS1984

Dyads and triads at 35,000 feet - Factors affecting group process and aircrew performance

The task of flying a multipilot transport aircraft is a classic small-group performance situation where a number of social, organizational, and personality factors are relevant to important outcome variables such as safety. The aviation community is becoming increasingly aware of the importance of these factors but is hampered in its efforts to improve the system because of research psychology's problems in defining the nature of the group process. This article identifies some of the problem areas as well as methods used to address these issues. It is argued that high fidelity flight simulators provide an environment that offers unique opportunities for work meeting both basic and applied research criteria.

Foushee, H. C.↗
NASA NTRS1985

Full load shop testing of 18,000-hp gas turbine driven centrifugal compressor for offshore platform service: Evaluation of rotor dynamics performance

The results for in-plant full load testing of a 13.4 MW (18000 HP) gas turbine driven centrifugal compressor are presented and compared to analytical predictions of compressor rotor stability. Unique problems from both oil seals and labyrinth gas seals were encountered during the testing. The successful resolution of these problems are summarized.

Kirk, R. G.↗
NASA NTRS1987

Dyads and triads at 35,000 feet: Factors affecting group process and aircrew performance

The task of flying a multipilot transport aircraft is a classic small-group performance situation where a number of social, organizational, and personality factors are relevant to important outcome variables such as safety. The aviation community is becoming increasingly aware of the importance of these factors but is hampered in its efforts to improve the system because of research psychology's problems in defining the nature of the group process. This article identifies some of the problem areas as well as methods used to address these issues. It is argued that high fidelity flight simulators provide an environment that offers unique opportunities for work meeting both basic and applied research criteria.

Foushee, H. Clayton↗
NASA NTRS1987

U-238-U-234-Th-230-Th-232 systematics and the precise measurement of time over the past 500,000 years

A method is presented for the high-precision measurement of the Th-230 abundance in corals by isotope-dilution mass spectrometry using techniques developed by Chen and Wasserburg (1980, 1981) and Chen et al. (1986). It is shown that 6 x 10 to the 8th atoms of Th-230 can be measured to + or - 30 percent (2 sigma) and 2 x 10 to the 10th atoms of Th-230 to + or - 2 percent. The time over which useful age data on corals can be obtained ranges from a few years to about 500 ky, with the uncertainty in age ranging from 5 y for a 180-y-old coral, to 44 y for a 8294-y-old coral, to 1.1 ky for a 123.1-ky-old coral. Ages were determined with high analytical precision for several corals that grew during high sea-level stands about 120 ky ago, supporting the view that the dominant cause of Pleistocene climate change was Milankovitch forcing.

Edwards, R. Lawrence↗
NASA NTRS1988

The computation of pi to 29,360,000 decimal digits using Borweins' quartically convergent algorithm

The quartically convergent numerical algorithm developed by Borwein and Borwein (1987) for 1/pi is implemented via a prime-modulus-transform multiprecision technique on the NASA Ames Cray-2 supercomputer to compute the first 2.936 x 10 to the 7th digits of the decimal expansion of pi. The history of pi computations is briefly recalled; the most recent algorithms are characterized; the implementation procedures are described; and samples of the output listing are presented. Statistical analyses show that the present decimal expansion is completely random, with only acceptable numbers of long repeating strings and single-digit runs.

Bailey, David H.↗
NASA NTRS1989

Jet-resolved vibronic structure in the higher excited states of N2O - Ultraviolet three-photon absorption spectroscopy from 80,000 to 90,000/cm

Ionization-detected UV multiphoton absorption spectroscopy of the excited states of N2O is presented, showing Rydberg structure within 20,000/cm of the first ionization threshold. Despite evidence for strong Rydberg-continuum coupling in the form of broadened bands and Fano line-shapes, the Rydberg structure persists, with atomic-like quantum defects and vibration structure well-matched with that of the ion. In the most clearly resolved spectrum, corresponding to the 3p(delta)1Pi state, Renner-Teller and Herzberg-Teller coupling of electronic and vibrational angular momentum are revealed. It is suggested that these mixings are properties of the N2O(+)Pi ion core.

Patsilinakou, E.↗
NASA NTRS1991

System and component design and test of a 10 hp, 18,000 rpm AC dynamometer utilizing a high frequency AC voltage link, part 1

Hard and soft switching test results conducted with one of the samples of first generation MOS-controlled thyristor (MCTs) and similar test results with several different samples of second generation MCT's are reported. A simple chopper circuit is used to investigate the basic switching characteristics of MCT under hard switching and various types of resonant circuits are used to determine soft switching characteristics of MCT under both zero voltage and zero current switching. Next, operation principles of a pulse density modulated converter (PDMC) for three phase (3F) to 3F two-step power conversion via parallel resonant high frequency (HF) AC link are reviewed. The details for the selection of power switches and other power components required for the construction of the power circuit for the second generation 3F to 3F converter system are discussed. The problems encountered in the first generation system are considered. Design and performance of the first generation 3F to 3F power converter system and field oriented induction moter drive based upon a 3 kVA, 20 kHz parallel resonant HF AC link are described. Low harmonic current at the input and output, unity power factor operation of input, and bidirectional flow capability of the system are shown via both computer and experimental results. The work completed on the construction and testing of the second generation converter and field oriented induction motor drive based upon specifications for a 10 hp squirrel cage dynamometer and a 20 kHz parallel resonant HF AC link is discussed. The induction machine is designed to deliver 10 hp or 7.46 kW when operated as an AC-dynamo with power fed back to the source through the converter. Results presented reveal that the proposed power level requires additional energy storage elements to overcome difficulties with a peak link voltage variation problem that limits reaching to the desired power level. The power level test of the second generation converter after the addition of extra energy storage elements to the HF link are described. The importance of the source voltage level to achieve a better current regulation for the source side PDMC is also briefly discussed. The power levels achieved in the motoring mode of operation show that the proposed power levels achieved in the generating mode of operation can also be easily achieved provided that no mechanical speed limitation were present to drive the induction machine at the proposed power level.

Lipo, Thomas A.↗
NASA NTRS1991

Modeling, simulation, and flight characteristics of an aircraft designed to fly at 100,000 feet

A manned real time simulation of a conceptual vehicle, the stratoplane, was developed to study the problems associated with the flight characteristics of a large, lightweight vehicle. Mathematical models of the aerodynamics, mass properties, and propulsion system were developed in support of the simulation and are presented. The simulation was at first conducted without control augmentation to determine the needs for a control system. The unaugmented flying qualities were dominated by lightly damped dutch roll oscillations. Constant pilot workloads were needed at high altitudes. Control augmentation was studied using basic feedbacks. For the longitudinal axis, flight path angle, and pitch rate feedback were sufficient to damp the phugoid mode and to provide good flying qualities. In the lateral directional axis, bank angle, roll rate, and yaw rate feedbacks were sufficient to provide a safe vehicle with acceptable handling qualities. Intentionally stalling the stratoplane to very high angles of attack (deep stall) was studied as a means of enable safe and rapid descent. It was concluded that the deep stall maneuver is viable for this class of vehicle.

Sim, Alex G.↗