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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 937 records · Page 52

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NASA NTRS1976

A technique for generating correlated X-band weather degradation statistics

It is, known that the X-band noise temperature of DSN receivers can go up from 20 K to over 100 K or more, if the air is heavily laden with water vapor, although that is an uncommon occurrence. It is proposed that the DSN furnish flight projects relying on X-band degradation models, one for each DSN Complex. Such models would be in the form of a random process generator, say in an MBASIC program, that would permit the project to generate X-band degradation data with the right autocorrelations for periods of interest to the Projects. The autocorrelation modeling is especially important because bursts of degradation lasting several days can affect data storage and mission sequence design strategy. One approach which works if the degradation statistics obey a half-gaussian law. That is, the random variables are formed by taking the absolute values of another set of random variables, themselves having a Gaussian distribution. The technique then permits the half-gaussian random variables to have given one and two-step correlation coefficients.

Posner, E. C.↗

NASA NTRS1976

Resource and environmental surveys from space with the thematic mapper in the 1980's

The selection of observation of vegetation is the primary optimization objective of the thematic mapper. The following are aspects of plans for the thematic mapper: (1) to include an appropriately modified first generation MSS in the thematic mapper mission; (2) to provide assured coverage for a minimum of six years to give agencies and other users an opportunity to justify the necessary commitment of resources for the transition into a completely valid operational phase; (3) to provide for global, direct data read-out, without the necessity for on-board data storage or dependence on foreign receiving stations; (4) to recognize the operational character of the thematic mapper after successful completion of its experimental evaluation; and (5) to combine future experimental packages with compatible orbits as part of the operational LANDSAT follow-on payloads.

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NASA NTRS1976

LANDSAT D data transmission and dissemination study

An assessment of the quantity of data processed by the system is discussed investigating the various methods for transmission within the system. Various methods of data storage are considered. It is concluded that the entire processing system should be located in White Sands, New Mexico.

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NASA NTRS1976

Selective data segment monitoring system

High speed data monitoring apparatus is described for displaying the bit pattern of a selected portion of a block of transmitted data comprising a shift register for receiving the transmitted data and for temporarily containing the consecutive data bits. A programmable sync detector for monitoring the contents of the shift register and for generating a sync signal when the shift register contains a predetermined sync code is included. A counter is described for counting the data bits input to the shift register after the sync signal is generated and for generating a count complete signal when a selected number of data bits have been input to the register. A data storage device is used for storing the contents of the shift register at the time the count complete signal is generated.

Wirth, M. N.↗

NASA NTRS1977

SAVLOC, computer program for automatic control and analysis of X-ray fluorescence experiments

A program for a PDP-15 computer is presented which provides for control and analysis of trace element determinations by using X-ray fluorescence. The program simultaneously handles data accumulation for one sample and analysis of data from previous samples. Data accumulation consists of sample changing, timing, and data storage. Analysis requires the locating of peaks in X-ray spectra, determination of intensities of peaks, identification of origins of peaks, and determination of a real density of the element responsible for each peak. The program may be run in either a manual (supervised) mode or an automatic (unsupervised) mode.

Leonard, R. F.↗

NASA NTRS1977

An implicit factored scheme for the compressible Navier-Stokes equations

An implicit finite difference scheme is developed for the numerical solution of the compressible Navier-Stokes equations in conservation-law form. The algorithm is second-order-time accurate, noniterative, and spatially factored. In order to obtain an efficient factored algorithm, the spatial cross-derivatives are evaluated explicitly. However, the algorithm is unconditionally stable and, although a three-time-level scheme, requires only two-time-levels of data storage. The algorithm is constructed in a 'delta' form (i.e., increments of the conserved variables and fluxes) that provides a direct derivation of the scheme and leads to an efficient computational algorithm. In addition, the delta form has the advantageous property of a steady-state (if one exists) independent of the size of the time step. Numerical results are presented for a two-dimensional shock boundary-layer interaction problem.

Beam, R. M.↗

NASA NTRS1977

Conceptual definition of Automated Power Systems Management

Automated Power Systems Management (APSM) is defined as the capability of a spacecraft power system to automatically perform monitoring, computational, command, and control functions without ground intervention. Power systems for future planetary spacecraft must have this capability because they must perform up to 10 years, and accommodate real-time changes in mission execution autonomously. Specific APSM functions include fault detection, isolation, and correction; system performance and load profile prediction; power system optimization; system checkout; and data storage and transmission control. This paper describes the basic method of implementing these specific functions. The APSM hardware includes a central power system computer and a processor dedicated to each major power system subassembly along with digital interface circuitry. The major payoffs anticipated are in enhancement of spacecraft reliability and life and reduction of overall spacecraft program cost.

Imamura, M. S.↗

NASA NTRS1977

Automated multi-level substructuring for Sperry's version of NASTRAN

Automated multilevel substructuring was successfully implemented in the Sperry version of NASTRAN. The development was achieved with a minimum effort; only seven modules and fourteen new routines were added. Approximately forty subroutines were modified and four new user cards addeded to NASTRAN. Significant features of the new capability include: multilevel substructuring; up to 128 superelements; up to 456 boundary grid points per superelement; up to 9 user superelement files, each with multi-reel or disc option; and data storage for one or more superelements per user file.

Chan, G. C.↗

NASA NTRS1978

Microprocessor-to-system/370 interface

The design and operation of a microprocessor interface unit which allows use of a computer terminal for communication at 110 or 300 baud both with a central host computer and with the microprocessor monitor are documented. Additionally, the interface permits the host computer to load the microprocessor memory directly with object code, avoiding the use of intermediate data storage such as paper tape. The central computer, containing an assembler language processor for the target microcomputer, can be used from the terminal with all the flexibility offered by the virtual machine facility, producing object code for the micro plus program listings and supporting outputs. The object code can then be loaded directly to the micro and the same terminal device used to run the micro program, communicating with the micro's monitor routine.

Lilley, R. W.↗

NASA NTRS1978

Transverse flat plate heat pipe experiment

This paper describes a Shuttle-launched flight experiment to evaluate the performance of a transverse flat plate heat pipe that serves as an integral temperature control/mounting panel for electronic equipment. A transverse heat pipe is a gas-controlled variable conductance heat pipe that can handle relatively large thermal loads. An experiment designed to flight test the concept over a 6-9 month period is self-sufficient with respect to electrical power, timing sequences, and data storage.

Edelstein, F.↗

NASA NTRS1978

X-ray spectrometer experiment aboard the ISEE-C /Heliocentric/ spacecraft

This experiment is designed to provide continuous coverage of solar flare X-ray bursts and transient cosmic gamma-ray bursts. A proportional counter and a scintillation detector together cover the energy range from 5 to 228 keV with good sensitivity, large dynamic range, and high temporal resolution. This experiment provides data storage capability and good absolute timing so that in conjunction with similar experiments on other spacecraft, accurate source locations can be obtained for cosmic gamma-ray bursts.

Anderson, K. A.↗

NASA NTRS1979

Inflight lightning characteristics measurement system

A research data-gathering system being developed for inflight measurement of direct and nearby lightning strike characteristics is described. Wideband analog recorders used to record the lightning scenario are supplemented with high-sample-rate digital transient recorders with augmented memory capacity for increased time resolution of specific times of interest. The endless-loop data storage technique employed by the transient recorders circumvents problems associated with oscilloscopic techniques and allows unattended operation. System integrity and immunity from induced effects is accomplished by fiber-optics signal-transmission links, shielded system enclosures, and the use of a dynamotor for power system isolation.

Pitts, F. L.↗

NASA NTRS1978

Command and control of unmanned scientific spacecraft

Recent developments in command and control technology for use with the Voyager and the planned Galileo are discussed. These spacecraft each carry more than 10 scientific instruments, many of which are very complex, and these instruments must be able to function with a considerable degree of autonomy because the round-trip light time to the spacecraft in the vicinity of Jupiter and Saturn is too great to permit prompt ground-based management of onboard anomalies or control of some observation programs. Command and control procedures, including data storage procedures, for systems of the two spacecraft are examined.

Gates, C. R.↗

NASA NTRS1979

Report of the Electromechanical Subsystems Panel

Deficiencies in electromechanical flight technology are evaluated and development recommendations are made. Specific items discussed include magnetic bearings, lubrication for long life, signal and power transfer devices, servo sensing devices, deployment/retraction devices, cryogenic devices, data storage, and ordnance substitutes.

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NASA NTRS1980

The Pioneer Venus Orbiter Gamma Burst Detector

The Orbiter Gamma Burst Detector was designed to record the temporal and spectral characteristics of cosmic gamma-ray bursts. The primary mission of the experiment is the accurate determination of the directions to the sources of such bursts through a technique of triangulation as a member of a widely spaced array of similar instruments. The system consists of a pair of scintillation spectrometers sensitive in the range of energies between 100 and 2000 keV, together with logic and data storage to provide a capability for recording these events. Nineteen events which have been verified as cosmic gamma-ray bursts were recorded within the first year's operation.

Klebesadel, R. W.↗

NASA NTRS1981

Transient upsets in microprocessor controllers

The modeling and analysis of transient faults in microprocessor based controllers are discussed. Such controllers typically consist of a microprocessor, read only memory storing and application program, random access memory for data storage, and input/output devices for external communications. The effects of transient faults on the performance of the controller are reviewed. An instruction level perspective of performance is taken which is the basis of a useful high level program state description of the microprocessor controller. A transition matrix is defined which determines the controller's response to transient fault arrivals.

Glaser, R. E.↗

NASA NTRS1982

Evaluation of the SPAR thermal analyzer on the CYBER-203 computer

The use of the CYBER 203 vector computer for thermal analysis is investigated. Strengths of the CYBER 203 include the ability to perform, in vector mode using a 64 bit word, 50 million floating point operations per second (MFLOPS) for addition and subtraction, 25 MFLOPS for multiplication and 12.5 MFLOPS for division. The speed of scalar operation is comparable to that of a CDC 7600 and is some 2 to 3 times faster than Langley's CYBER 175s. The CYBER 203 has 1,048,576 64-bit words of real memory with an 80 nanosecond (nsec) access time. Memory is bit addressable and provides single error correction, double error detection (SECDED) capability. The virtual memory capability handles data in either 512 or 65,536 word pages. The machine has 256 registers with a 40 nsec access time. The weaknesses of the CYBER 203 include the amount of vector operation overhead and some data storage limitations. In vector operations there is a considerable amount of time before a single result is produced so that vector calculation speed is slower than scalar operation for short vectors.

Robinson, J. C.↗

NASA NTRS1982

Computer simulation of a space SAR using a range-sequential processor for soil moisture mapping

The ability of a spaceborne synthetic aperture radar (SAR) to detect soil moisture was evaluated by means of a computer simulation technique. The computer simulation package includes coherent processing of the SAR data using a range-sequential processor, which can be set up through hardware implementations, thereby reducing the amount of telemetry involved. With such a processing approach, it is possible to monitor the earth's surface on a continuous basis, since data storage requirements can be easily met through the use of currently available technology. The Development of the simulation package is described, followed by an examination of the application of the technique to actual environments. The results indicate that in estimating soil moisture content with a four-look processor, the difference between the assumed and estimated values of soil moisture is within + or - 20% of field capacity for 62% of the pixels for agricultural terrain and for 53% of the pixels for hilly terrain. The estimation accuracy for soil moisture may be improved by reducing the effect of fading through non-coherent averaging.

Fujita, M.↗