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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A flight simulator for advanced aircraft - Servo design to realization.

Discussion of computer-aided design results obtained for a moving-base, three-man flight simulator. From a control viewpoint, the structure is discussed in terms of disturbance torques, damping ratios, natural frequencies, load acceleration, and smoothness. The use of inertia to achieve well-behaved structural transfer functions and smooth or high fidelity load accelerations is demonstrated. Transfer functions in the complex frequency domain, as well as time-dependent solutions to the system, are derived. The relative merits of using position and/or velocity as primary feedback, for a limited travel acceleration device, are discussed. Root locus plots, which were utilized in the control-system design, Bode plots, and time-dependent plots are drawn. In addition, the theoretical ratio of velocity to commanded input Bode plot is compared to the experimental results, and the dramatic effect on the load smoothness plot caused by selecting velocity over position as primary feedback is shown.

King, R. F.↗
NASA NTRS1973

Industrial realization of a direct Fourier transform in automated experimental data processing systems

Fourier processing of automatic signals transforms direct current voltage into a numerical form through bandpass filtration in time-pulse multiplying devices. It is shown that the ratio of the interference energy to the useful signal energy is inversely proportional to the square of the product of the depth of the width modulation and the ratio of the time constant averaging to the cross-multiplied signals.

Lyubashevskiy, G. S.↗
NASA NTRS1973

On the dynamical realization of /M, R/-systems

A new manner of representing a class of abstract cell models previously developed by the author is presented. Some of the properties of this dynamical representation are explored, and their consequences discussed.

Rosen, R.↗
NASA NTRS1975

Reconciling the requirements of the science team and the spacecraft engineering team with a realizable optical system

Problems in the development of a suitable optical system for the imaging science payload of an interplanetary space probe are considered, taking into account the characteristics of the three categories of optical systems from which the engineer selects his system. These categories include the Catoptric or all mirror optical system, the Dioptric or all refracting optical system, and the Catadioptric system which combines elements of the other two categories. Examples of equipment selection and development in the preparation of a number of interplanetary space missions are discussed.

Larks, L.↗
NASA NTRS1976

A realization of the RAM digital filter

The digital filtering algorithm of W. D. Little, which employs a large RAM to obtain high speed, is implemented in a simple hardware configuration. The nonrecursive version of this filter is compared to the counting digital filter and found to be competitive for low-order filters up to order 7 (8 coefficients).

Zohar, S.↗
NASA NTRS1979

Microprocessor realizations of range rate filters

The performance of five digital range rate filters is evaluated. A range rate filter receives an input of range data from a radar unit and produces an output of smoothed range data and its estimated derivative range rate. The filters are compared through simulation on an IBM 370. Two of the filter designs are implemented on a 6800 microprocessor-based system. Comparisons are made on the bases of noise variance reduction ratios and convergence times of the filters in response to simulated range signals.

Source record↗
NASA NTRS1980

Weather and climate needs for Lidar observations from space and concepts for their realization

The spectrum of weather and climate needs for Lidar observations from space is discussed with emphasis on the requirements for wind, temperature, moisture, and pressure data. It is shown that winds are required to realistically depict all atmospheric scales in the tropics and the smaller scales at higher latitudes, where both temperature and wind profiles are necessary. The need for means to estimate air-sea exchanges of sensible and latent heat also is noted. A concept for achieving this through a combination of Lidar cloud top heights and IR cloud top temperatures of cloud streets formed during cold air outbreaks over the warmer ocean is outlined. Recent theoretical feasibility studies concerning the profiling of temperatures, pressure, and humidity by differential absorption Lidar (DIAL) from space and expected accuracies are reviewed. An alternative approach to Doppler Lidar wind measurements also is presented. The concept involves the measurement of the displacement of the aerosol backscatter pattern, at constant heights, between two successive scans of the same area, one ahead of the spacecraft and the other behind it a few minutes later. Finally, an integrated space Lidar system capable of measuring temperature, pressure, humidity, and winds which combines the DIAL methods with the aerosol pattern displacement concept is described.

Atlas, D.↗
NASA NTRS1980

Microprocessor realizations of range and range-rate filters in radar systems

This paper describes the implementation of digital radar range-rate filters on a microprocessor-based system. A range-rate filter processes a digitized noisy range signal to recover smoothed range data and its derivative, range rate. Two filter designs are implemented. Considerations aiding their efficient operation on an 8-bit microprocessor are discussed. The filters are subjected to a noisy range input signal of known variance, and the associated output signals are statistically analysed to determine noise-rejection characteristics. These results are compared to analytical predictions.

Fleischer, D.↗
NASA NTRS1981

Realizable feed-element patterns for multibeam reflector antenna analysis

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Rahmat-Samii, Y.↗
NASA NTRS1981

Weather and climate needs for lidar observations from space and concepts for their realization

The spectrum of weather and climate needs for lidar observations from space is discussed. This paper focuses mainly on the requirements for winds, temperature, moisture, and pressure. Special emphasis is given to the need for wind observations, and it is shown that winds are required to depict realistically all atmospheric scales in the tropics and the smaller scales at higher latitudes, where both temperature and wind profiles are necessary. The need for means to estimate air-sea exchanges of sensible and latent heat also is noted. Lidar can aid here by measurement of the slope of the boundary layer. Recent theoretical feasibility studies concerning the profiling of temperature, pressure, and humidity by differential absorption lidar (DIAL) from space and expected accuracies are reviewed. Initial ground-based trials provide support for these approaches and also indicate their direct applicability to path-average temperature measurements near the surface. An alternative approach to Doppler lidar wind measurements also is presented. The concept involves the measurement of the displacement of the aerosol backscatter pattern, at constant height, between two successive scans of the same area, one ahead of the spacecraft and the other behind it, a few minutes later. Finally, an integrated space lidar system capable of measuring temperature, pressure, humidity, and winds which combines the DIAL methods with the aerosol pattern displacement concept is described briefly.

Atlas, D.↗
NASA NTRS1986

Realizations of magnetic-monopole gauge fields - Diatoms and spin precession

It is found that the effective Hamiltonian for nuclear rotation in a diatom is equivalent to that of a charged particle in a background magnetic-monopole field. In certain cases, half-integer orbital angular momentum or non-Abelian fields occur. Furthermore, the effects of magnetic-monopole-like gauge fields can be experimentally observed in spin-resonance experiments with variable magnetic fields.

Moody, J.↗
NASA NTRS1988

Hardware realization of a baseband processor for a SS-FDMA/TDMA/DAMA system

Hardware implementation of the NASA ACTS baseband processor is described which achieves the system message data handling performance required to perform satellite switching of high-rate baseband data. The hardware meets payload specifications for size, weight, and power. Hardware redundancy applied to critical paths in several functional areas insures that the reliability and life expectancy requirements are fulfilled. The remote reprogrammability of the processor message data handling and routing functions provides system flexibility for dynamic reconfiguration during rapidly changing traffic loads.

Moat, Richard L.↗