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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Current limiting remote power control module

The power source for the Space Station Freedom will be fully utilized nearly all of the time. As such, any loads on the system will need to operate within expected limits. Should any load draw an inordinate amount of power, the bus voltage for the system may sag and disrupt the operation of other loads. To protect the bus and loads some type of power interface between the bus and each load must be provided. This interface is most crucial when load faults occur. A possible system configuration is presented. The proposed interface is the Current Limiting Remote Power Controller (CL-RPC). Such an interface should provide the following power functions: limit overloading and resulting undervoltage; prevent catastrophic failure and still provide for redundancy management within the load; minimize cable heating; and provide accurate current measurement. A functional block diagram of the power processing stage of a CL-RPC is included. There are four functions that drive the circuit design: rate control of current; current sensing; the variable conductance switch (VCS) technology; and the algorithm used for current limiting. Each function is discussed separately.

Hopkins, Douglas C.↗
NASA NTRS1991

Advanced magnetic suspensions for vibration isolation and fast-attitude control of space-based generic pointing mounts

Advanced magnetic suspension for vibration isolation and fast-attitude control of space-based generic pointing mounts (GPM) is presented in the form of viewgraphs. The following subject areas are covered: design criteria for GPM; GPM system features; GPM performance characteristics; GPM functional block diagram; and other applications for generic magnetic suspension technologies.

Bosley, Robert W.↗
NASA NTRS1991

NASA/Ames Research Center DC-8 data system

In-flight facility data acquisition, distribution, and recording on the NASA Ames Research Center (ARC) DC-8 are performed by the Data Acquisition and Distribution System (DADS). Navigational and environmental data collected by the DADS are converted to engineering units and distributed real-time to investigator stations once per second. Selected engineering units data are printed and displayed on closed circuit television monitors throughout flights. An in-flight graphical display of the DC-8 flight track (with barbs indicating wind direction and magnitude) has recently been added to the DADS capabilities. Logging of data run starts/stops and commentary from the mission director are also provided. All data are recorded to hard disk in-flight and archived to tape medium post-flight. Post-flight, hard copies of the track map and mission director's log are created by the DADS. The DADS is a distributed system consisting of a data subsystem, an Avionic Serial Data-to-VMEbus (ASD2VME) subsystem, and a host subsystem. Each subsystem has a dedicated central processing unit (CPU) and is capable of stand-alone operation. All three subsystems are housed in a single 20-slot VME chassis and communicate with each other over the VMEbus. The data and host subsystems are briefly discussed, and the DC-8 DADS internal configuration and system block diagram are presented.

Cherniss, S. C.↗
NASA NTRS1990

Photovoltaic array space power plus diagnostics experiment

The objective is to summarize the five years of hardware development and fabrication represented by the Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) Instrument. The original PASP Experiment requirements and background is presented along with the modifications which were requested to transform the PASP Experiment into the PASP Plus Instrument. The PASP Plus hardware and software is described. Test results for components and subsystems are given as well as final system tests. Also included are appendices which describe the major subsystems and present supporting documentation such as block diagrams, schematics, circuit board artwork, drawings, test procedures and test reports.

Burger, D. R.↗
NASA NTRS1989

Remote, PCM-controlled, multi-channel radio frequency FM telemetry system for cryogenic wind tunnel application

A telemetry system used in the NASA-Langley cryogenic transonic wind tunnel to obtain rotational strain and temperature data is described. The system consists of four FM transmitters allowing for a remotely controlled PCM combination. A rotating four-contact mercury slip-ring is used as an interface between the fixed and rotating mechnical structures. Over 60 channels of data on the main fan disk and blade structures have been obtained. These data are studied to verify computer predictions and mechanical life. A series of block diagrams are included.

Diamond, John K.↗
NASA NTRS1989

Reliable magnetic tape recording for real-time data acquisition systems

The design of a real-time magnetic tape I/O system using automatic error recovery and data spooling is discussed. Real time requirements (data acquired at one rate and recorded at another by queing) must be met and data integrity must be provided regardless of tape failures or I/O errors. Automatic blocking services should be used for multiple local records storage. Avoidance of operational delays and loss of data is essential, noting the problems of the tape drives of the NASA Langley cryogenic wind tunnel. A series of block diagrames and flow charts are included.

Richard W Ross↗
NASA NTRS1991

Detection of target distance in the presence of an interfering reflection using a frequency-stepped double side-band suppressed carrier microwave radar system

A technique for detecting the distance to a highly reflective target in the presence of an interesting reflection using a frequency-stepped double-sideband suppressed carrier (DSBSC) microwave-millimeter-wave radar system is analytically derived. The main result of the analysis shows that the measured group delays produced by the DSBSC system possess a periodicity inversely proportional to the difference between the time delays to the target and interferer, independent of the signal-to-interference ratio (SIR). Simulation results are presented in the context of electron plasma density range estimation using a block diagram communications CAD tool. A unique and accurate plasma model is introduced. A high-resolution spectral estimation technique based on an autoregressive time series analysis is applied to the measured group delays, and it is shown that accurate target distance estimates may be obtained, independent of SIR.

Ybarra, Gary A.↗
NASA NTRS1990

Generation and analysis of large reliability models

An effort has been underway for several years at NASA's Langley Research Center to extend the capability of Markov modeling techniques for reliability analysis to the designers of highly reliable avionic systems. This effort has been focused in the areas of increased model abstraction and increased computational capability. The reliability model generator (RMG), a software tool which uses as input a graphical, object-oriented block diagram of the system, is discussed. RMG uses an automated failure modes-effects analysis algorithm to produce the reliability model from the graphical description. Also considered is the ASSURE software tool, a parallel processing program which uses the ASSIST modeling language and SURE semi-Markov solution technique. An executable failure modes-effects analysis is used by ASSURE. The successful combination of the power of graphical representation, automated model generation, and parallel computation leads to the conclusion that large system architectures can now be analyzed.

Aerospace electronics↗
NASA NTRS1990

A 200 MHz surface acoustic wave mass microbalance

The principle of operation of the surface acoustic wave (SAW) piezoelectric crystals used as microgravimetric sensors in mass microbalances is discussed. Special attention is given to a SAW 200-MHz crystal developed for measuring molecular deposition on spacecrafts, whose operating frequency does not depend on the thickness of the crystal. The frequency stability of the 200 MHz SAW device is better than 5 x 10 exp -9, which corresponds to a lower limit-of-detection of 3 x 10 exp -12 g for a signal-to-noise ratio of 3. A block diagram of the 200 MHz SAW mass microbalance and a schematic diagram of SAW resonator are presented together with performance data of this device.

Bowers, William D.↗
NASA NTRS1991

Telerobotic ground-remote operations

The Telerobotic Ground-Remote Operations task consists of development of a demonstration local-site operator control station that includes a graphical user interface (GUI) for control of a remote robot, and development of operator-assisted perception algorithms and software that will provide flexible and accurate world modeling capabilities. The topics covered are presented in view graph form and include: (1) local site development configuration; (2) system design; (3) operator control station (local site) software block diagram; (4) operator-assisted perception; and (5) program status.

Bon, Bruce↗
NASA NTRS1991

Nickel-hydrogen LEO cycling at 20 percent - 50 percent DOD

The test setup consists of four major elements: the programmable power supplies and load banks, the data acquisition and control system control computer, and the NiH2 specimen test cells. A simplified block diagram of the test setup is shown. The test setup provides complete battery isolation should a fault occur, and fusing as necessary to protect the battery cells and other equipment. Front panel switches provide for power supply configuration and battery isolation. Front panel meters provide continuous real-time visual monitoring of the voltage and current for each pack of cells. A strip chart recorder provides a hard copy of the voltage and current profiles for each of the packs. The test operates continuously with minimal human interface, except during special tests. The two power supplies are controlled by resistance programming. A bank of resistors and relays was built which can be switched by the control computer to provide control over the charge current to the batteries. The load banks are controlled by the 3497A. The 3497A is equipped with a 0.5 volt programmable power supply which is used to voltage program the load banks. A Hewlett-Packard Vectra 9000 running an HP Basic program is used as the control computer to remotely instruct the 3497A (data acquisition and control) to scan the data channels and retrieve test data. The program then reads, calculates, and stores the data. If an anomaly occurs, the program will disconnect the cells and shut down the test to avoid damage to the cells or equipment.

Lowery, John E.↗
NASA NTRS1992

Bandwidth efficient CCSDS coding standard proposals

The basic concatenated coding system for the space telemetry channel consists of a Reed-Solomon (RS) outer code, a symbol interleaver/deinterleaver, and a bandwidth efficient trellis inner code. A block diagram of this configuration is shown. The system may operate with or without the outer code and interleaver. In this recommendation, the outer code remains the (255,223) RS code over GF(2 exp 8) with an error correcting capability of t = 16 eight bit symbols. This code's excellent performance and the existence of fast, cost effective, decoders justify its continued use. The purpose of the interleaver/deinterleaver is to distribute burst errors out of the inner decoder over multiple codewords of the outer code. This utilizes the error correcting capability of the outer code more efficiently and reduces the probability of an RS decoder failure. Since the space telemetry channel is not considered bursty, the required interleaving depth is primarily a function of the inner decoding method. A diagram of an interleaver with depth 4 that is compatible with the (255,223) RS code is shown. Specific interleaver requirements are discussed after the inner code recommendations.

Costello, Daniel J., Jr.↗
NASA NTRS1992

Advanced techniques in reliability model representation and solution

The current tendency of flight control system designs is towards increased integration of applications and increased distribution of computational elements. The reliability analysis of such systems is difficult because subsystem interactions are increasingly interdependent. Researchers at NASA Langley Research Center have been working for several years to extend the capability of Markov modeling techniques to address these problems. This effort has been focused in the areas of increased model abstraction and increased computational capability. The reliability model generator (RMG) is a software tool that uses as input a graphical object-oriented block diagram of the system. RMG uses a failure-effects algorithm to produce the reliability model from the graphical description. The ASSURE software tool is a parallel processing program that uses the semi-Markov unreliability range evaluator (SURE) solution technique and the abstract semi-Markov specification interface to the SURE tool (ASSIST) modeling language. A failure modes-effects simulation is used by ASSURE. These tools were used to analyze a significant portion of a complex flight control system. The successful combination of the power of graphical representation, automated model generation, and parallel computation leads to the conclusion that distributed fault-tolerant system architectures can now be analyzed.

Palumbo, Daniel L.↗
NASA NTRS1990

A design and critical technology issues for on-orbit resupply of superfluid helium

The issues of and the solutions to the critical design and technology areas of the Superfluid Helium On-Orbit Transfer (SHOOT) experiment, presently under development at the NASA Goddard Spaceflight Center, are discussed. Special attention is given to the SHOOT design requirements for the 10,000-liter superfluid He resupply tanker system, the concept details of the system, and the resupply operations and their analysis. A block diagram of the SHOOT system is included along with fluid management schematic and configuration diagrams of the system and its subsystems. A summary of the dewar performance is also presented.

Hopkins, Richard A.↗
NASA NTRS1991

Computer-aided system design

A technique has been developed for combining features of a systems architecture design and assessment tool and a software development tool. This technique reduces simulation development time and expands simulation detail. The Architecture Design and Assessment System (ADAS), developed at the Research Triangle Institute, is a set of computer-assisted engineering tools for the design and analysis of computer systems. The ADAS system is based on directed graph concepts and supports the synthesis and analysis of software algorithms mapped to candidate hardware implementations. Greater simulation detail is provided by the ADAS functional simulator. With the functional simulator, programs written in either Ada or C can be used to provide a detailed description of graph nodes. A Computer-Aided Software Engineering tool developed at the Charles Stark Draper Laboratory (CSDL CASE) automatically generates Ada or C code from engineering block diagram specifications designed with an interactive graphical interface. A technique to use the tools together has been developed, which further automates the design process.

Walker, Carrie K.↗
NASA NTRS1991

Applications of an automated programming system

A Computer-Aided Software Engineering (CASE) system has been developed at the Charles Stark Draper Laboratory (CSDL) under the direction of the NASA Langley Research Center. The Automated Programming Subsystem is the core of the CSDL CASE system. The Automated Programming Subsystem allows an engineer to describe software specifications as hierarchical engineering block diagrams, a natural design technique for the specification of real-time software. The objective of the Automated Programming Subsystem is to capture completely and consistently both logical and schematic information as diagrams are developed, and then to automatically transform this information into source code (Ada or C) and documentation. The Automated Programming Subsystem of CSDL CASE has been used on many applications, from small to moderate size. Six of these applications are described in this paper.

Walker, Carrie K.↗
NASA NTRS1992

ROMPS critical design review. Volume 1: Hardware

Topics concerning the Robot-Operated Material Processing in Space (ROMPS) Program are presented in viewgraph form and include the following: a systems overview; servocontrol and servomechanisms; testbed and simulation results; system V controller; robot module; furnace module; SCL experiment supervisor; SCL script sample processing control; SCL experiment supervisor fault handling; block diagrams; hitchhiker interfaces; battery systems; watchdog timers; mechanical/thermal systems; and fault conditions and recovery.

Dobbs, M. E.↗