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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

NASA direct detection laser diode driver

TRW has developed a prototype driver circuit for GaAs laser diodes as part of the NASA/Goddard Space Flight Center's Direct Detection Laser Transceiver (DDLT) program. The circuit is designed to drive the laser diode over a range of user-selectable data rates from 1.7 to 220 Mbps, Manchester-encoded, while ensuring compatibility with 8-bit and quaternary pulse position modulation (QPPM) formats for simulating deep space communications. The resulting hybrid circuit has demonstrated 10 to 90 percent rise and fall times of less than 300 ps at peak currents exceeding 100 mA.

Seery, B. D.↗
NASA NTRS1990

A comparison of transportation node costs and their primary drivers

This paper describes the process for defining and evaluating the costs of alternative transportation node concepts for Space Station Freedom. A cost estimating methodology including costs of development, production, delivery, assembly, steady state operations, and mission-specific operations is described in detail. The primary drivers of transportation node costs are identified and discussed.

Comstock, Douglas A.↗
NASA NTRS1991

Pulse-Width-Modulating Driver for Brushless dc Motor

High-current pulse-width-modulating driver for brushless dc motor features optical coupling of timing signals from low-current control circuitry to high-current motor-driving circuitry. Provides high electrical isolation of motor-power supply, helping to prevent fast, high-current motor-driving pulses from being coupled through power supplies into control circuitry, where they interfere with low-current control signals.

Salomon, Phil M.↗
NASA NTRS1991

Driver Circuit For High-Power MOSFET's

Driver circuit generates rapid-voltage-transition pulses needed to switch high-power metal oxide/semiconductor field-effect transistor (MOSFET) modules rapidly between full "on" and full "off". Rapid switching reduces time of overlap between appreciable current through and appreciable voltage across such modules, thereby increasing power efficiency.

Letzer, Kevin A.↗
NASA NTRS1991

Modeling preparation costs for space missions by using major cost drivers

A model is suggested for making long range planning cost estimates for Deep Space Network (DSN) support of future space missions. The model is a function of major mission cost drivers, such as maintenance and operations, downlink frequency upgrade, uplink frequency upgrade, telemetry upgrade, antenna gain/noise temperature, radiometric accuracy upgrade, radio science upgrade, and very long baseline interferometry. The model is derived from actual cost data from three space missions: Voyager (Uranus), Voyager (Neptune), and Magellan. The model allows one to estimate the total cost and the cost over time of a similar future space mission. The model was back tested against the three projects and gave cost estimates that range from 17 pct. below to 19 pct. above actual mission preparation costs. The model was also compared with two other independent projects: Mariner Jupiter/Saturn (MJS later became Voyager) and Viking. The model gave total preparation cost estimates that range from 15 pct. above to 4 pct. below actual total preparation costs for MJS and Viking, respectively.

Sherif, J. S.↗
NASA NTRS1992

Statistical characterization of life drivers for a probabilistic design analysis

This paper discusses the issue of statistical characterization of life drivers for a probabilistic design analysis (PDA) approach to support the conventional deterministic structural design methods that are currently used. The probabilistic approach takes into consideration the modeling inadequacies and uncertainties in many design variables such as loads, environments, and material properties. The importance of the distributional assumption is motivated by illustrating an example where the results differ substantially due to the distribution selected. Different types of distributions are discussed and techniques for estimating the parameters are given. Given this information, procedures are outlined for selecting the appropriate distribution based on the particular type of variable (i.e., dimensional, performance) as well as the information that is available (i.e., test data, engineering analysis). Finally, techniques are given for generating random numbers from these selected distributions within the PDA process.

Fox, Eric P.↗
NASA NTRS1992

Modeling the Deep Space Network costs for future space missions by using major cost drivers

This paper develops a cost model to do long range planning cost estimates for Deep Space Network (DSN) support of future space missions. The model is a function of eight major mission cost drivers such as uplink frequency upgrade, telemetry upgrade, and antenna gain/noise temperature upgrade. This paper focuses on the costs required to modify and/or enhance the DSN to prepare for supporting future space missions. Two models are derived from actual cost data from three space missions: Voyager (Uranus), Voyager (Neptune), and Magellan. Model A makes it possible to estimate the total cost, and Model B makes it possible to estimate the time profile cost and total cost for DSN support of a similar future space mission. The models were back tested against the total cost and the time profile cost for DSN support of the three projects, and gave cost estimates which range from 17 percent below to 19 percent above actual costs for Model A, and 22.5 percent below to 17.5 percent above for Model B. The total cost Model A was also applied to estimate the total costs for DSN support of two other independent projects: Mariner Jupiter/Saturn (MJS later became Voyager), and Viking. This model gave total cost estimates for DSN support which range from 15 percent to 4 percent above actual total costs for MJS and Viking, respectively.

Remer, Donald S.↗
NASA NTRS1994

Latching-Relay Driver And Continuity Checker

Driving circuit and associated continuity-checking circuit enable use of latching relay switch instead of non-latching relay switch in 120-Vdc power-distribution system. Average power consumed reduced by about 15 W. Latching-relay driver and continuity checker provides automatic turnoff relay when power fails, or alarm indicating discontinuity in turn-off circuit, respectively.

Kachelski, Thomas A.↗
NASA NTRS1993

Design and cost drivers in 2-D braiding

Fundamentally, the braiding process is a highly efficient, low cost method for combining single yarns into circumferential shapes, as evidenced by the number of applications for continuous sleeving. However, this braiding approach cannot fully demonstrate that it can drastically reduce the cost of complex shape structural preforms. Factors such as part geometry, machine design and configuration, materials used, and operating parameters are described as key cost drivers and what is needed to minimize their effect on elevating the cost of structural braided preforms.

Morales, Alberto↗
NASA NTRS1993

Estimating the Deep Space Network modification costs to prepare for future space missions by using major cost drivers

This paper develops a cost model to do long range planning cost estimates for Deep Space Network (DSN) support of future space missions. The paper focuses on the costs required to modify and/or enhance the DSN to prepare for future space missions. The model is a function of eight major mission cost drivers and estimates both the total cost and the annual costs of a similar future space mission. The model is derived from actual cost data from three space missions: Voyager (Uranus), Voyager (Neptune), and Magellan. Estimates derived from the model are tested against actual cost data for two independent missions, Viking and Mariner Jupiter/Saturn (MJS).

Remer, Donald S.↗
NASA NTRS1993

Technology drivers for flight telerobotic system software

Viewgraphs on technology drivers for flight telerobotic system software are included. Topics covered include: flight software lines of code; flight computer architecture; system safety; safety critical parameters; system safety - software functions.

Labaugh, Robert↗
NASA NTRS1995

Description of a MIL-STD-1553B Data Bus Ada Driver for the LeRC EPS Testbed

This document describes the software designed to provide communication between control computers in the NASA Lewis Research Center Electrical Power System Testbed using MIL-STD-1553B. The software drivers are coded in the Ada programming language and were developed on a MSDOS-based computer workstation. The Electrical Power System (EPS) Testbed is a reduced-scale prototype space station electrical power system. The power system manages and distributes electrical power from the sources (batteries or photovoltaic arrays) to the end-user loads. The electrical system primary operates at 120 volts DC, and the secondary system operates at 28 volts DC. The devices which direct the flow of electrical power are controlled by a network of six control computers. Data and control messages are passed between the computers using the MIL-STD-1553B network. One of the computers, the Power Management Controller (PMC), controls the primary power distribution and another, the Load Management Controller (LMC), controls the secondary power distribution. Each of these computers communicates with two other computers which act as subsidiary controllers. These subsidiary controllers are, in turn, connected to the devices which directly control the flow of electrical power.

Mackin, Michael A.↗
NASA NTRS1994

Pressurized fluid torque driver control and method

Methods and apparatus are provided for a torque driver including a displaceable gear to limit torque transfer to a fastener at a precisely controlled torque limit. A biasing assembly biases a first gear into engagement with a second gear for torque transfer between the first and second gear. The biasing assembly includes a pressurized cylinder controlled at a constant pressure that corresponds to a torque limit. A calibrated gage and valve is used to set the desired torque limit. One or more coiled output linkages connect the first gear with the fastener adaptor which may be a socket for a nut. A gear tooth profile provides a separation force that overcomes the bias to limit torque at the desired torque limit. Multiple fasteners may be rotated simultaneously to a desired torque limit if additional output spur gears are provided. The torque limit is adjustable and may be different for fasteners within the same fastener configuration.

Cook, Joseph S., Jr.↗
NASA NTRS1997

Displaceable Gear Torque Controlled Driver

Methods and apparatus are provided for a torque driver including a displaceable gear to limit torque transfer to a fastener at a precisely controlled torque limit. A biasing assembly biases a first gear into engagement with a second gear for torque transfer between the first and second gear. The biasing assembly includes a pressurized cylinder controlled at a constant pressure that corresponds to a torque limit. A calibrated gage and valve is used to set the desired torque limit. One or more coiled output linkages connect the first gear with the fastener adaptor which may be a socket for a nut. A gear tooth profile provides a separation force that overcomes the bias to limit torque at the desired torque limit. Multiple fasteners may be rotated simultaneously to a desired torque limit if additional output spur gears are provided. The torque limit is adjustable and may be different for fasteners within the same fastener configuration.

Cook, Joseph S., Jr.↗
NASA NTRS1996

Displaceable Spur Gear Torque Controlled Driver and Method

Methods and apparatus are provided for a torque driver including a laterally displaceable gear support member to carry an output spur gear. A biasing assembly biases the output spur gear into engagement with a pinion to which is applied an input torque greater than a desired output torque limit for a threaded fastener such as a nut or screw. A coiled output linkage connects the output spur gear with a fastener adaptor which may be a socket for a nut. A gear tooth profile provides a separation force that overcomes the bias to limit torque at the desired torque limit. Multiple fasteners may be rotated simultaneously to a desired torque limit if additional output spur gears are provided. A gauged selector mechanism is provided to laterally displace multiple driven members for fasteners arranged in differing configurations. The torque limit is selectably adjustable and may be different for fasteners within the same fastener configuration.

Cook, Joseph S., Jr.↗
NASA NTRS1997

Bevel Gear Driver and Method Having Torque Limit Selection

Methods and apparatus are provided for a torque driver including an axially displaceable gear with a biasing assembly to bias the displaceable gear into an engagement position. A rotatable cap is provided with a micrometer dial to select a desired output torque. An intermediate bevel gear assembly is disposed between an input gear and an output gear. A gear tooth profile provides a separation force that overcomes the bias to limit torque at a desired torque limit. The torque limit is adjustable and may be adjusted manually or automatically depending on the type of biasing assembly provided. A clutch assembly automatically limits axial force applied to a fastener by the operator to avoid alteration of the desired torque limit.

Cook, Joseph S., Jr.↗
NASA NTRS1998

Thin-Layer Composite Unimorph Ferroelectric Driver Sensor Properties

Tests were conducted on 13 different configurations of a new class of piezoelectric devices called THUNDER (thin layer composite unimorph ferroelectric driver and sensor). These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25.4 micron thick aluminium as a backing material, with and without a top layer of 25.4 micrometer aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.08 x 3.81 x 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after repoling. The parameters measured included frequency, driving voltage. displacement, capacitance, and radius of curvature. An optic sensor recorded the displacement at a fixed voltage(100 - 400 V peak to peak) over a predetermined frequency range (1 - 1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter alpha was defined which can be used to predict the which configuration will produce the most displacement for a free standing device.

Mossi, Karla M.↗
NASA NTRS2001

An Active Substrate Driver for Enabling Mixed-Voltage SOI Systems-On-A-Chip

The current trend for space application systems is towards fully integrated systems-on-a-chip. To facilitate this drive, high-voltage transistors must reside on the same substrate as low-voltage transistors. These systems must also be radiation tolerant, particularly for space missions such as the Europa Lander and Titan Explorer. SOI CMOS technology offers high levels of radiation hardness. As a result, a high-voltage lateral MOSFET has been developed in a partially-depleted (PD) SOI technology. Utilizing high voltages causes a parasitic transistor to have non-negligible effects on a circuit. Several circuit architectures have been used to compensate for the radiation induced threshold voltage shift of the parasitic back-channel transistor. However, a new architecture for high-voltage systems must be employed to bias the substrate to voltage levels insuring all parasitic transistors remain off. An active substrate driver has been developed to accomplish task. Additional information is contained in the original extended abstract.

Jackson, S. A.↗