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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Sequential control chart methodology

A modification of the V mask sequential control chart is proposed. In this modified scheme, a parabolic section is included in the mask to provide better performance when the process undergoes a large change in the mean from goal conditions. It is shown that the modified V mask can be implemented either in conventional graphic form, or in an algorithmic form suitable for a digital computer. Average run lengths are given for a typical range of circumstances. It also is shown that the conventional Shewhart chart is better than a sequential chart for the specific purpose of promptly detecting very large shifts of the mean from goal conditions.

Source record↗
NASA NTRS1972

Preliminary design of an auxiliary power unit for the space shuttle. Volume 1: Summary

Numerous candidate APU concepts are considered, each meeting the space shuttle APU problem statement. Evaluation of these concepts indicates that the optimum concept is a hydrogen-oxygen APU incorporating a recuperator to utilize the exhaust energy and using the cycle hydrogen flow as a means of cooling the component heat loads. A preliminary design of the selected APU concept is presented, placing primary emphasis on the cycle thermal management and the controls. Results for both steady state and transient APU performance are also included, based on digital computer programs developed during the study. The selected APU provides up to 400 hp out of the gearbox, has a fixed weight of about 277 lb, and requires about 2 lb/shp-hr of propellants.

Hamilton, M. L.↗
NASA NTRS1969

Tracking system study

A digital computer program was generated which mathematically describes an optimal estimator-controller technique as applied to the control of antenna tracking systems used by NASA. Simulation studies utilizing this program were conducted using the IBM 360/91 computer. The basic ideas of applying optimal estimator-controller techniques to antenna tracking systems are discussed. A survey of existing tracking methods is given along with shortcomings and inherent errors. It is explained how these errors can be considerably reduced if optimal estimation and control are used. The modified programs generated in this project are described and the simulation results are summarized. The new algorithms for direct synthesis and stabilization of the systems including nonlinearities, are presented.

Dennis, A. R.↗
NASA NTRS1971

Design, development, fabrication and delivery of register and multiplexer units

Two complementary MOS monolithic chip types were developed, which contain a register and multiplexer unit to be used in the central processing unit of a digital computer. The partition of the logic into a chip size consistent with the characteristics of the packages is discussed. The logic was implemented by specially configured circuitry designed to layout, as well as to optimize, performance by taking advantage of the properties of CMOS logic. Of several approaches considered for generating LSI CMOS arrays, the CMOS standard cell array design technique was selected. These design automation techniques were used to generate the chip layout, art work and working master plates, followed by the fabrication and testing of the two chip types. Sixty functional LSI arrays were delivered.

Feller, A.↗
NASA NTRS1972

Design of inducers for two-phase operation

A mathematical model and a digital computer program were developed for the design and evaluation of inducers for pumping two-phase oxygen. The mathematical model indicated that any design would have to be run at relatively low speeds to pump two-phase oxygen and that the J-2S oxygen inducer was close to optimum and should perform the task. A J-2S pump was built up and tested in two-phase oxygen at speeds indicated by the mathematical model. The pump was able to handle two-phase oxygen over a wide range of inducer incidence angles and up to a vapor content of 37 percent by volume with very little loss in head. The pump was still able to produce some head at vapor fractions approaching 60 percent.

King, J. A.↗
NASA NTRS1972

Development of a digital control system for a spacecraft propulsion test facility

A digital computer control and abort system which is used at NASA-Lewis research center is described. The system was designed to control test operations such as rocket engine testing, structure testing, and wind tunnel tests. Because of the nature of spacecraft system testing, particularly rocket engine testing, the unique features of the system are, control function updating at a 20 millisecond rate, continuous abort monitoring and a software system designed for short duration tests rather than continuous on-line control. To accomplish these system requirements, special hardware was designed. The presentation includes a description of the computer system and special interface hardware as well as a general description of the software used.

Smalley, R. R.↗
NASA NTRS1972

Performance and control study of a low-pressure-ratio turbojet engine for a drone aircraft

The results of analog and digital computer studies of a low-pressure-ratio turbojet engine system for use in a drone vehicle are presented. The turbojet engine consists of a four-stage axial compressor, single-stage turbine, and a fixed area exhaust nozzle. Three simplified fuel schedules and a generalized parameter fuel control for the engine system are presented and evaluated. The evaluation is based on the performance of each schedule or control during engine acceleration from a windmill start at Mach 0.8 and 6100 meters to 100 percent corrected speed. It was found that, because of the higher acceleration margin permitted by the control, the generalized parameter control exhibited the best dynamic performance.

Seldner, K.↗
NASA NTRS1972

A method for analyzing dynamic stall of helicopter rotor blades

A model for each of the basic flow elements involved in the unsteady stall of a two-dimensional airfoil in incompressible flow is presented. The interaction of these elements is analyzed using a digital computer. Computations of the loading during transient and sinusoidal pitching motions are in good qualitative agreement with measured loads. The method was used to confirm that large torsional response of helicopter blades detected in flight tests can be attributed to dynamic stall.

Crimi, P.↗
NASA NTRS1971

Analysis of simulated multispectral data from earth resources satellites

The validity of the applicability assumption was determined through the simulation of ERTS and Skylab data using available aircraft scanner systems. The research techniques compared aircraft multispectral scanner data obtained under nominal conditions at low altitudes. Maximum likelihood decision criteria algorithms implemented on a digital computer were used to classify training set data. Comparisons between percentages of correct classifications were made, along with implications as to the techniques of satellite analysis.

White, D. A.↗
NASA NTRS1972

Digital simulation of continuous error models with application to an instrument landing system error

A digital simulation of the continuous error of the localized beam of a conventional instrument landing system is discussed. The digital simulation was developed during the analysis of space shuttle navigation capabilities. A discrete mathematical model for use on a digital computer is described. The model generates an output random sequence which is equivalent, for simulation purposes, to the desired random process. The model is a system of difference equations driven by a zero-mean Gaussian random sequence.

Merrick, R. B.↗
NASA NTRS1969

Optimal feedback control for nonlinear control moment gyro systems

A study was made, leading to development and analysis of a technique allowing the control moment gyro (CMG) momentum vectors to avoid adverse orientations and thus to provide optimal control for the Apollo Telescope Mount. The technique was formulated in terms of a feedback scheme using a check factor, K, formed as the product of the dot products of the three CMG momentum unit vectors. The parameter K approaches unity for all adverse orientations and was used to initiate a single correction maneuver to rotate the CMG momenta away from a pending adverse orientation and to reduce K to an acceptable value. A digital computer program for ATM simulations was modified to incorporate this correction maneuver and performance was evaluated in simulated cases. Antiparallelism was used as the primary example for the evaluation of the feedback optimization technique.

Kyle, R. G.↗
NASA NTRS1971

Stratification calculations in a heated cryogenic oxygen storage tank at zero gravity

A cylindrical one-dimensional model of the Apollo cyrogenic oxygen storage tank has been developed to study the effect of stratification in the tank. Zero gravity was assumed, and only the thermally induced motions were considered. The governing equations were derived from conservation laws and solved on a digital computer. Realistic thermodynamic and transport properties were used. Calculations were made for a wide range of conditions. The results show the fluid behavior to be dependent on the quantity in the tank or equivalently the bulk fluid temperature. For high quantities (low temperatures) the tank pressure rose rapidly with heat addition, the heater temperature remained low, and significant pressure drop potentials accrued. For low quantities the tank pressure rose more slowly with heat addition and the heater temperature became high. A high degree of stratification resulted for all conditions; however, the stratified region extended appreciably into the tank only for the lowest tank quantity.

Shuttles, J. T.↗
NASA NTRS1970

Preliminary software development for optical mirror figure control

The maintenance of accurate primary mirror figure in the face of environmental disturbances is the key to the achievement of diffraction-limited performance in a large space telescope. In order to develop the concepts of optical mirror figure control, an experimental program was initiated. A major component in this experiment will be an XDS Sigma 5.7 digital computer which will realize the control algorithm. A software package is described which realizes linear optimal, simplified linear, and iterative optimal control algorithms. The software, in addition, provides for interactive communication between the operator and the computer, and interaction between the computer and the experimental hardware elements. A brief description of a small hybrid computer system is also presented.

Mackinnon, D.↗
NASA NTRS1972

Improved guidance hardware study for the scout launch vehicle

A market survey and evaluation of inertial guidance systems (inertial measurement units and digital computers) were made. Comparisons were made to determine the candidate systems for use in the Scout launch vehicle. Error analyses were made using typical Scout trajectories. A reaction control system was sized for the fourth stage. The guidance hardware to Scout vehicle interface was listed.

Schappell, R. T.↗
NASA NTRS1972

Preliminary design of an auxiliary power unit for the space shuttle. Volume 4: Selected system supporting studies

Selected system supporting analyses in conjunction with the preliminary design of an auxiliary power unit (APU) for the space shuttle are presented. Both steady state and transient auxiliary power unit performance, based on digital computer programs, were examined. The selected APU provides up to 400 horsepower out of the gearbox, weighs 227 pounds, and requires 2 pounds per shaft horsepower hour of propellants.

Hamilton, M. L.↗
NASA NTRS1972

High Energy Astronomy Observatory star tracker search program

The development of a control system to accommodate the scientific payload of the High Energy Astronomy Observatory (HEAO) is discussed. One of the critical elements of the system is the star tracker subsystem, which defines an accurate three-axis attitude reference. A digital computer program has been developed to evaluate the ability of a particular star tracker configuration to meet the requirements for attitude reference at various vehicle orientations. Used in conjuction with an adequate star catalog, the computer program provides information on availability of stars for each tracker and on the ability of the system to maintain three-axis attitude reference throughout a representative sequence of vehicle orientations.

Weiler, W. J.↗