SEARCH · Engineering Papers

Results for “Performance evaluation”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60

All sources NASA NTRS DOE OSTI

NASA NTRS1981

Sequential decision rules for failure detection

The formulation of the decision making of a failure detection process as a Bayes sequential decision problem (BSDP) provides a simple conceptualization of the decision rule design problem. As the optimal Bayes rule is not computable, a methodology that is based on the Baysian approach and aimed at a reduced computational requirement is developed for designing suboptimal rules. A numerical algorithm is constructed to facilitate the design and performance evaluation of these suboptimal rules. The result of applying this design methodology to an example shows that this approach is a useful one.

Chow, E. Y.↗

NASA NTRS1981

Pointing system modeling for performance prediction

The paper considers the modeling and analysis of the JPL Precision Pointing and Tracking System, a gyro stabilized platform pointing system using optical target tracking. Sensor and actuator models are described which realistically represent actual hardware, and a practical controller and state estimator is developed through modern control techniques. The effect of the actuator nonlinearities on the system performance evaluation is discussed along with the modeling of the noise sources in the gyro. Finally, the limitations of implementing the control algorithms on the spacecraft computer, and the resulting tradeoffs are presented.

Boussalis, D.↗

NASA NTRS1980

An analysis of the Seasat Satellite Data Distribution System

A computerized data distribution network for remote accessing of Seasat generated data is described. The service is intended as an experiment to determine user needs and operational abilities for utilizing on-line satellite generated oceanographic data. Synoptic weather observations are input to the U.S. Fleet Numerical Oceanographic Central for preparation and transfer to a PDP 11/60 central computer, from which all access trunks originate. The data available includes meteorological and sea-state information in the form of analyses and forecasts, and users are being monitored for reactions to the system design, data products, system operation, and performance evaluation. The system provides data on sea level and upper atmospheric pressure, sea surface temperature, wind magnitude and direction, significant wave heights, direction, and periods, and spectral wave data. Transmissions have a maximum rate of 1.1 kbit/sec over the telephone line.

Ferrari, A. J.↗

NASA NTRS1982

The use of differential pressure feedback in an automatic flight control system

A feasibility study has been performed to evaluate the performance of a system whereby a control surface is positioned with differential pressure as the feedback variable. Analogous to a position command system, the control surface is commanded to move until a certain differential pressure is achieved at a given point on the surface. Frequency response tests and theoretical considerations indicate that the pressure feedback transfer function is first order, with a break frequency up to 50 rad/sec. There exist applications to the outer loops of flight control systems as well. Stability augmentation, gust alleviation, and stall prevention appear to be possible by feeding back differential pressure across lifting and control surfaces.

Levy, D. W.↗

NASA NTRS1982

Seasat synthetic-aperture radar data reduction using parallel programmable array processors

This paper presents a digital processing system that produces the Seasat synthetic-aperture radar (SAR) imagery. The system consists of a SEL 32/77 host minicomputer and three AP-120B array processors. The partitioning of the SAR processing functions and the design of software modules is described. The rationale for selecting the parallel array processor architecture and the methodology for developing the parallel processing scheme on this system is described. This system attains a Seasat SAR data reduction speed of 2.5 h per 25-m resolution 4-look and 100 km x 100 km image frame. A preliminary performance evaluation of this parallel processing system and potential future applications for remote sensing data reduction are described.

Wu, C.↗

NASA NTRS1981

Performance of quadrature overlapped raised-cosine modulation over nonlinear satellite channels

This paper considers the performance evaluation of Staggered Quadrature Overlapped Raised Cosine (SQORC) signal transmission through wideband nonlinear satellite channels in the presence of uplink and downlink additive Gaussian noise. Expressions for the bit error rate are derived for a general transponder model with AM-AM and AM-PM conversion. It is shown that the bit error rate of SQORC is one-half of the sum of the bit error rate of MSK at 2/3 of the uplink signal-to-noise ratio and the bit error rate of Quadriphase Phase-Shift Keying QPSK at 4/3 of the uplink signal-to-noise ratio, whereas the spectrum of SQROC is the product of MSK and QPSK spectra. Numerical results are presented for a transponder which is modelled as a hard limiter.

Divsalar, D.↗

NASA NTRS1982

Evaluation of Space Transportation System (STS) OV-102 orbiter payload bay acoustic environment

This report presents the results of a statistical analysis and evaluation performed by the Mechanical Engineering Branch (Code 731) on the payload bay internal acoustic data measured on the STS-1 through STS-4 flights. The results are used as a basis for developing the required baseline acoustic environment specification to be used in establishing design and test criteria for STS payloads and components.

On, F. J.↗

NASA NTRS1982

LANDSAT-D Mission Operations Review (MOR)

Portions of the LANDSAT-D systems operation plan are presented. An overview of the data processing operations, logistics and other operations support, prelaunch and post-launch activities, thematic mapper operations during the scrounge period, and LANDSAT-D performance evaluation is given.

Source record↗

NASA NTRS1982

Deep Space Telecommunications Systems Engineering

Descriptive and analytical information useful for the optimal design, specification, and performance evaluation of deep space telecommunications systems is presented. Telemetry, tracking, and command systems, receiver design, spacecraft antennas, frequency selection, interference, and modulation techniques are addressed.

Yuen, J. H.↗

NASA NTRS1983

Liquid fluorine/hydrazine rhenium thruster update

The status of a fluorine/hydrazine thruster development program is discussed. A solid rhenium metal sea-level thrust chamber was successfully fabricated and tested for a total run duration of 1075 s with 17 starts. Rhenium fabrication methods are discussed. A test program was conducted to evaluate performance and chamber cooling. Acceptable performance was reached and cooling was adequate. A flight-type injector was fabricated that achieved an average extrapolated performance value of 3608 N-s/kg (368 lbf-s/lbm). Altitude thrust chambers were fabricated. One chamber incorporates a rhenium combustor and nozzle with an area ratio of 15:1, and a columbium nozzle extension with area ratios from 15:1 to 60:1. The other chamber was fabricated completely with a carbon/carbon composite. Because of the attributes of rhenium for use in high-temperature applications, a program to provide the materials and processes technology needed to reliably fabricate and/or repair vapor-deposited rhenium parts of relatively large size and complex shape is recommended.

Appel, M. A.↗

NASA NTRS1983

Distributed control of large space antennas

A systematic way to choose control design parameters and to evaluate performance for large space antennas is presented. The structural dynamics and control properties for a Hoop and Column Antenna and a Wrap-Rib Antenna are characterized. Some results of the effects of model parameter uncertainties to the stability, surface accuracy, and pointing errors are presented. Critical dynamics and control problems for these antenna configurations are identified and potential solutions are discussed. It was concluded that structural uncertainties and model error can cause serious performance deterioration and can even destabilize the controllers. For the hoop and column antenna, large hoop and long meat and the lack of stiffness between the two substructures result in low structural frequencies. Performance can be improved if this design can be strengthened. The two-site control system is more robust than either single-site control systems for the hoop and column antenna.

Cameron, J. M.↗

NASA NTRS1985

Antenna Radiation-Pattern Program

Effects of reflector deformations and feed characteristics computed. JPL Antenna Radiation Pattern computer program ANRAD, evaluates performance of radio-frequency antenna with paraboloidal main reflector by solving scalar far-field radiation pattern integral.

Hughes, R. D.↗

NASA NTRS1984

Theoretical and experimental analysis of laser altimeters for barometric measurements over the ocean

The statistical characteristics and the waveforms of ocean-reflected laser pulses are studied. The received signal is found to be corrupted by shot noise and time-resolved speckle. The statistics of time-resolved speckle and its effects on the timing accuracy of the receiver are studied in the general context of laser altimetry. For estimating the differential propagation time, various receiver timing algorithms are proposed and their performances evaluated. The results indicate that, with the parameters of a realistic altimeter, a pressure measurement accuracy of a few millibars is feasible. The data obtained from the first airborne two-color laser altimeter experiment are processed and analyzed. The results are used to verify the pressure measurement concept.

Tsai, B. M.↗

NASA NTRS1984

Fuel system design concepts for broad property fuels

The results of a study assessing the impact of using jet fuel with relaxed specification properties on an aircraft fuel system are given. The study objectives were to identify credible values for specific fuel properties which might be relaxed, to evolve advanced fuel system designs for airframe and engines which would permit use of the specified relaxed properties fuels, and to evaluate performance of the candidate advanced fuel systems and the relaxed property fuels in a typical transport aircraft. The study used, as a baseline, the fuel system incorporated in the Lockheed Tristar. This aircraft is powered by three RB.211-524 Rolls-Royce engines and incorporates a Pratt and Whitney ST6C-421 auxiliary power unit for engine starting and inflight emergency electrical power. The fuel property limits examined are compared with commercial Jet A kerosene and the NASA RFP fuel properties. A screening of these properties established that a higher freezing point and a lower thermal stability would impact fuel system design more significantly than any of the other property changes. Three candidate fuel systems which combine the ability to operate with fuels having both a high freeze point and a low thermal stability are described. All candidates employ bleed air to melt fuel freeze-out prior to starting the APU or an inoperable engine. The effects of incorporating these systems on aircraft weight and engine specific fuel consumption are given.

Versaw, E. F.↗

NASA NTRS1982

Study of aerodynamic technology for single-cruise-engine V/STOL fighter/attack aircraft

A viable, single engine, supersonic V/STOL fighter/attack aircraft concept was defined. This vectored thrust, canard wing configuration utilizes an advanced technology separated flow engine with fan stream burning. The aerodynamic characteristics of this configuration were estimated and performance evaluated. Significant aerodynamic and aerodynamic propulsion interaction uncertainties requiring additional investigation were identified. A wind tunnel model concept and test program to resolve these uncertainties and validate the aerodynamic prediction methods were defined.

Hess, J. R.↗

NASA NTRS1984

Low earth orbit navigation in the TDAS era

It is pointed out that by the 1990s projected increases in scientific data volume and spacecraft engineering data will require an extension of the Tracking and Data Relay Satellite System (TDRSS). There will also be requirements with respect to improvements related to navigation. The Tracking Data Acquisition System (TDAS) is defined as the heir to TDRSS for the 1990s and beyond. A pre-Phase A TDAS concept definition study has recently been completed. The study covers a 15 year planning period extending from 1990 to 2005. The present investigation is concerned with TDAS-based alternatives, taking into account aspects of orbit and time determination. Attention is given an overview of TDRSS capabilities, pertiment TDAS architecture options, potential user navigation accuracy requirements, and some results of preliminary navigation performance evaluations.

Elrod, B. D.↗

NASA NTRS1983

Deep space telecommunication systems engineering

Yuen, J. H.↗

NASA NTRS1985

Hybrid and Electric Advanced Vehicle Systems Simulation

Predefined components connected to represent wide variety of propulsion systems. Hybrid and Electric Advanced Vehicle System (HEAVY) computer program is flexible tool for evaluating performance and cost of electric and hybrid vehicle propulsion systems. Allows designer to quickly, conveniently, and economically predict performance of proposed drive train.

Beach, R. F.↗