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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Study of solid rocket motor for space shuttle booster, volume 2, book 5, appendices E thru H

Preliminary parametric studies were performed to establish size, weight and packaging arrangements for aerodynamic decelerator devices that could be used for recovery of the expended solid propellant rocket motors used in the launch phase of the Space Shuttle System. Computations were made using standard engineering analysis techniques. Terminal stage parachutes were sized to provide equilibrium descent velocities for water entry that are presently thought to be acceptable without developing loads that could exceed the boosters structural integrity. The performance characteristics of the aerodynamic parachute decelerator devices considered are based on analysis and prior test results for similar configurations and are assumed to be maintained at the scale requirements of the present problem.

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NASA NTRS1973

Solar proton fluences as observed during 1966-1972 and as predicted for 1977-1983 space missions

The probability with which any given proton fluence level will be exceeded during a space mission is computed for missions to be flown during the active phase of the next solar cycle (1977-1983). This probability is a function of fluence level, proton energy threshold, and mission duration. Data on the major solar proton events of 1966-1972 are given; it is argued that only this data set (and not that of the previous solar cycle) is appropriate for estimating next-cycle fluences. Probable numbers of each of the two types of events are estimated from Burrell's extension of Poisson statistics. Fluences of all future anomalously large events are assumed to have a common spectrum, that given by the August 1972 event. Fluences of the ordinary events are assumed to obey a log normal distribution. It is shown that for much of the confidence-level mission-duration regime of interest, at least one anomalously large event will occur; and given such an occurrence, the ordinary-event contribution to mission fluence is negligible.

King, J. H.↗
NASA NTRS1974

Basic memory module

Construction and electrical characterization of the 4096 x 2-bit Basic Memory Module (BMM) are reported for the Space Ultrareliable Modular Computer (SUMC) program. The module uses four 2K x 1-bit N-channel FET, random access memory chips, called array chips, and two sense amplifier chips, mounted and interconnected on a ceramic substrate. Four 5% tolerance power supplies are required. At the Module, the address, chip select, and array select lines require a 0-8.5 V MOS signal level. The data output, read-strobe, and write-enable lines operate at TTl levels. Although the module is organized as 4096 x 2 bits, it can be used in a 8196 x 1-bit application with appropriate external connections. A 4096 x 1-bit organization can be obtained by depopulating chips.

Tietze, F. C.↗
NASA NTRS1974

Solar proton fluences for 1977-1983 space missions

The probability with which any given solar proton fluence level will be exceeded during a space mission is computed for mission to be flown during the active phase of the next solar cycle (1977-1983). This probability is a function of fluence level, proton energy threshold, and mission duration. Calculations are based on 1966-1972 data only. In estimating mission fluences, a distinction is made between ordinary and anomalously large events. Probable numbers of each type of event are estimated from Burrell's extension of Poisson statistics. Fluences of all anomalously large events are assumed to have a spectrum given by the August 1972 event, while fluences of the ordinary events are assumed to obey a log normal distribution.

King, J. H.↗
NASA NTRS1974

Stability regions for quasiperiodic motion in the restricted problem of three bodies

Surfaces of section, plotted in configuration space, have been computed for the motion of the massless particle in the restricted problem of three bodies. Nine mass ratios and a wide variety of Jacobi constants were investigated; over four thousand orbits were computed, about half of which were finally used. The plots of surface of section have been reduced to plots of stability regions, following a method due to Henon (1965a, 1965b, 1966b, 1969). Sample surfaces of section are also given. The complete set of 276 surfaces of section has been published as a report (Jefferys, 1971) and is available upon request from the author.

Jefferys, W. H.↗
NASA NTRS1974

Optimum propellant usage for reaction jet systems of space vehicles

The on-off type control for reaction jet systems is proven to be the optimal fuel scheme. However, due to the nonlinear characteristics of this type control, no direct method of solution is known for this optimal process being applied to the attitude control of space vehicles. This paper will discuss the optimization of fuel usage for an attitude control of space vehicles. A computation technique is developed for the calculation of optimal control law. The method of calculus of variations is applied to the estimation of the changes of performance index as well as terminal constraints. Thus an algorithm is obtained by the steepest descent method. A numerical example is given in the paper.

Liu, T. C.↗
NASA NTRS1974

NCUBE - A clustering algorithm based on a discretized data space

Cluster analysis involves the unsupervised grouping of data. The process provides an automatic procedure for generating known training samples for pattern classification. NCUBE, the clustering algorithm presented, is based upon the concept of imposing a gridwork on the data space. The NCUBE computer implementation of this concept provides an easily derived form of piecewise linear discrimination. This piecewise linear discrimination permits the separation of some types of data groups that are not linearly separable.

Eigen, D. J.↗
NASA NTRS1974

State space representations of distributed fluid line dynamics

The purpose of this paper is to demonstrate the convenience of using a systematic straight forward procedure to obtain meaningful dynamic information for a class of complex distributed parameter fluid line networks. System transients in the time domain are determined by means of state space techniques. Digital computer implementation yields a simple but consistent way of obtaining overall system time solutions. A step-by-step analysis procedure flow chart is shown in Appendix I which illustrates the basic approach for modeling, approximating and selecting digital techniques for simulating the dynamic response of fluid line systems.

Yao, H.↗
NASA NTRS1975

Main memory unit

The development of a main memory unit (MMU) for the space ultrareliable module computer (SUMC) model HTC is discussed. The design, fabrication, and test of basic memory modules (BMM) which were to be used in the design and construction of the MMU are described. The BMM was designed from state-of-the-art technologies which included large scale integration devices mounted and interconnected on a substrate to form a functional module to be utilized in the MMU development. A SUMC memory system design study is discussed which addressed itself to the BMM design and analysis to be conducted to determine the most efficient organization of the BMM in order to establish such modularity features as: word length expandability without redesign, high reliability, and fault tolerance. One MMU was designed, fabricated, tested, and delivered which will be electrical and mechanically compatible with the hybrid technology computer (HTC) model of the SUMC family of computers. The MMU will contain a storage capacity of 8196 36 bit words which includes a parity bit for each 8 bit byte of data.

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NASA NTRS1975

Computation of nonequilibrium three-dimensional inviscid flow over blunt-nosed bodies flying at supersonic speeds

A computer code based on the method of characteristics is described and applied to the study of two- and three-dimensional chemical nonequilibrium flow over sharp and blunt-nosed bodies. Nonequilibrium flow over a wedge is used to show the approach to equilibrium flow, and to demonstrate the nature of the reaction zone behind the bow shock wave. The structure and development of a blunt-body entropy layer in nonequilibrium flow is examined for a blunt cone at zero incidence. Three-dimensional computations for the space shuttle body at 30 deg angle of attack are presented. A nondimensional scaling parameter, the Damkoehler number, which is the ratio of flow time to chemical reaction time, is calculated and its significance discussed.

Rakich, J. V.↗
NASA NTRS1976

Space shuttle orbital maneuvering system failure detection and identification software requirements (uncontrolled)

Candidate designs and their software implementation are presented for the Orbital Maneuvering System (OMS) Failure Detection and Identification (FDI) algorithms in the Redundance Management (RM) module of the Space Shuttle Guidance, Navigation, and Control (GN&C) software. The OMS engine FDI algorithm monitors OMS engine thrust performance, and the OMS actuator FDI algorithm monitors OMS gimbal actuator performance. The software functional requirements of the algorithms are described along with the objective of each algorithm. A list of the assumptions which have governed its design, input/output requirements, a functional description of the algorithm (including a functional block diagram), and input interface requirements are given. The HAL (the language of the space shuttle flight computer) software formulation of the algorithms is considered including structured flowcharts of the procedures, estimates of flight computer core storage and CPU time, and processing requirements. A glossary of the symbols used to define the software requirements and formulations is included.

Damario, L. A.↗
NASA NTRS1976

Applications of feature selection

The use of satellite-acquired (LANDSAT) multispectral scanner (MSS) data to conduct an inventory of some crop of economic interest such as wheat over a large geographical area is considered in relation to the development of accurate and efficient algorithms for data classification. The dimension of the measurement space and the computational load for a classification algorithm is increased by the use of multitemporal measurements. Feature selection/combination techniques used to reduce the dimensionality of the problem are described.

Guseman, L. F., Jr.↗
NASA NTRS1976

Redundant Strapdown Laser Gyro Navigation System

For the last several years, NASA has pursued the development of low-cost high-reliability inertial navigation systems that would satisfy a broad spectrum of future space and avionics missions. Two specific programs have culminated in the construction of a Redundant Strapdown Laser Gyro Navigation System. These two programs were for development of a space ultrareliable modular computer (SUMC) and a redundant laser gyro inertial measurement unit (IMU). The SUMC is a digital computer that employs state-of-the-art large-scale integrated circuits configured in a functional modular breakdown. The redundant laser gyro IMU is a six-pack strapdown sensor package in a dodecahedron configuration which uses six laser gyros to provide incremental angular positions and six accelerometers for linear velocity outputs. The sensor arrangement allows automatic accommodation of two failures; a third failure can be tolerated provided it can be determined. The navigation system also includes redundant power supplies, built-in test-equipment (BITE) circuits for failure detection, and software which provides for navigation, redundancy management, and automatic calibration and alignment.

Mcpherson, B. W.↗
NASA NTRS1977

Formulation of consumables management models. Guidelines for the development of consumables subsystem redlines for advanced spacecraft

Techniques developed for determining the safe operating range or condition of past space programs are inadequate to support requirements of highly repetitive and routine earth orbit operations of advanced spacecraft systems. General concepts are presented for establishing maximum and minimum limits (redlines) for the consumables subsystems of the space shuttle orbiter. Implementation of a redline status subprocessor is recommended as a substitute for methods employed in past programs. The algorithms developed are amenable for use in the Mission Control Center, the launch processing system, and the space shuttle onboard computer.

Zamora, M. A.↗
NASA NTRS1980

No-reheat air-conditioning

Air conditioning system, for environmentally controlled areas containing sensitive equipment, regulates temperature and humidity without wasteful and costly reheating. System blends outside air with return air as dictated by various sensors to ensure required humidity in cooled spaces (such as computer room).

Obler, H. D.↗
NASA NTRS1980

Compiler validates units and dimensions

Software added to compiler for automated test system for Space Shuttle decreases computer run errors by providing offline validation of engineering units used system command programs. Validation procedures are general, though originally written for GOAL, a free-form language that accepts "English-like" statements, and may be adapted to other programming languages.

Levine, F. E.↗
NASA NTRS1980

Discrete Tchebycheff orthonormal polynomials and applications

Discrete Tchebycheff orthonormal polynomials offer a convenient way to make least squares polynomial fits of uniformly spaced discrete data. Computer programs to do so are simple and fast, and appear to be less affected by computer roundoff error, for the higher order fits, than conventional least squares programs. They are useful for any application of polynomial least squares fits: approximation of mathematical functions, noise analysis of radar data, and real time smoothing of noisy data, to name a few.

Lear, W. M.↗