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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Multiple Views on Safety-Critical Automation: Aircraft, Autonomous Vehicles, Air Traffic Management and Satellite Ground Segments Perspectives

This SIG focuses on the engineering of automation in interactive critical systems. Automation has already been studied in a number of (sub-) disciplines and application fields: design, human factors, psychology, (software) engineering, aviation, health care, games. One distinguishing feature of the area we are focusing on is that in the field of interactive critical systems properties such as reliability, dependability, fault-tolerance are as important as usability, user experience or overall acceptance issues. The SIG targets at two problem areas: first the engineering of the user interaction with (partly-) autonomous systems: how to design, build and assess autonomous behavior, especially in cases where there is a need to represent on the user interface both autonomous and interactive objects. An example of such integration is the representation of an unmanned aerial vehicle (UAV) (where no direct interaction is possible), together with aircrafts (that have to be instructed by an air traffic controller to avoid the UAV). Second the design and engineering of user interaction in general for autonomous objects systems (for example a cruise control in a car or an autopilot in an aircraft). The goal of the SIG is to raise interest in the CHI community on the general aspects of automation and to identify a community of researchers and practitioners interested in those increasingly prominent issues of interfaces towards (semi)-autonomous systems. The expected audience should be interested in addressing the issues of integration of mainly unconnected research domains to formulate a new joint research agenda.

safety-critical automation↗
NASA NTRS1980

Method of determination of the mass composition of ring current ions

A method for individual registration of protons, and helium and oxygen ions, with energies E for a charge on the order of 100 kev/q in the ring currents of the Earth's magnetosphere was examined. The method is based on the various specific losses in energy by these ions in matter. The ion current, selected according to E/q, is passed through a solid target, after which identification of the masses is carried out, based on the energy losses in the possibly to reliably divide the flows of protons, and helium and oxygen ions.

Temnyy, V. V.↗
NASA NTRS1989

Evaluation of fault-tolerant parallel-processor architectures over long space missions

The impact of a five year space mission environment on fault-tolerant parallel processor architectures is examined. The target application is a Strategic Defense Initiative (SDI) satellite requiring 256 parallel processors to provide the computation throughput. The reliability requirements are that the system still be operational after five years with .99 probability and that the probability of system failure during one-half hour of full operation be less than 10(-7). The fault tolerance features an architecture must possess to meet these reliability requirements are presented, many potential architectures are briefly evaluated, and one candidate architecture, the Charles Stark Draper Laboratory's Fault-Tolerant Parallel Processor (FTPP) is evaluated in detail. A methodology for designing a preliminary system configuration to meet the reliability and performance requirements of the mission is then presented and demonstrated by designing an FTPP configuration.

Johnson, Sally C.↗
NASA NTRS2005

High Spatial Resolution Commercial Satellite Imaging Product Characterization

NASA Stennis Space Center's Remote Sensing group has been characterizing privately owned high spatial resolution multispectral imaging systems, such as IKONOS, QuickBird, and OrbView-3. Natural and man made targets were used for spatial resolution, radiometric, and geopositional characterizations. Higher spatial resolution also presents significant adjacency effects for accurate reliable radiometry.

Ryan, Robert E.↗
NASA NTRS2009

Targeting Ballistic Lunar Capture Trajectories Using Periodic Orbits in the Sun-Earth CRTBP

A particular periodic orbit in the Earth-Sun circular restricted three body problem is shown to have the characteristics needed for a ballistic lunar capture transfer. An injection from a circular parking orbit into the periodic orbit serves as an initial guess for a targeting algorithm. By targeting appropriate parameters incrementally in increasingly complicated force models and using precise derivatives calculated from the state transition matrix, a reliable algorithm is produced. Ballistic lunar capture trajectories in restricted four body systems are shown to be able to be produced in a systematic way.

Cooley, D.S.↗
NASA NTRS2020

Thermodynamic Measurements Using the Knudsen Cell Technique

The Knudsen cell technique has been used for over a century and is a valuable tool for measurement of vapor pressures and thermodynamic properties. It is based on a small enclosure (~1 cm long x 1 cm diameter) in which a condensed phase/vapor equilibria can be established. A small (<1 mm) orifice on the cell allows sampling of the vapor via a variety of techniques including weight loss, torsion effusion, target collection, and mass spectrometry. Many excellent measurements based on these methods have been reported. However in order to obtain reliable measurements, a variety of factors must be considered. They include proper cell material selection, accurate and uniform temperature control and measurement, and proper sampling of the vapor. Each of these factors are discussed in detail in this chapter. Typically these studies are conducted at high temperatures and it is a challenge to select an inert container material. Recommended materials are discussed and in some cases the container may be used as part of the system under study. Temperature control and measurement is perhaps the most important issue. In most systems, the furnace must be compact yet there can be no temperature gradient in the cell. Temperatures are measured with either a thermocouple or pyrometer and the relative advantages of each are discussed. Sampling method considerations depend on the particular technique. It is essential that all of the vapor or a representative portion of the vapor be sampled. The distribution of the effusate from a Knudsen cell is discussed and sampling positions discussed. Mass spectrometry is often used to study the effusing vapor and the relations between ion current and vapor pressure are discussed.

mass spectrometry↗
NASA NTRS2013

Improved Targeting Through Collaborative Decision-Making and Brain Computer Interfaces

This paper reports a first step toward a brain-computer interface (BCI) for collaborative targeting. Specifically, we explore, from a broad perspective, how the collaboration of a group of people can increase the performance on a simple target identification task. To this end, we requested a group of people to identify the location and color of a sequence of targets appearing on the screen and measured the time and accuracy of the response. The individual results are compared to a collective identification result determined by simple majority voting, with random choice in case of drawn. The results are promising, as the identification becomes significantly more reliable even with this simple voting and a small number of people (either odd or even number) involved in the decision. In addition, the paper briefly analyzes the role of brain-computer interfaces in collaborative targeting, extending the targeting task by using a BCI instead of a mechanical response.

Brain computer interfaces (BCI)↗
NASA NTRS2011

FPGA Sequencer for Radar Altimeter Applications

A sequencer for a radar altimeter provides accurate attitude information for a reliable soft landing of the Mars Science Laboratory (MSL). This is a field-programmable- gate-array (FPGA)-only implementation. A table loaded externally into the FPGA controls timing, processing, and decision structures. Radar is memory-less and does not use previous acquisitions to assist in the current acquisition. All cycles complete in exactly 50 milliseconds, regardless of range or whether a target was found. A RAM (random access memory) within the FPGA holds instructions for up to 15 sets. For each set, timing is run, echoes are processed, and a comparison is made. If a target is seen, more detailed processing is run on that set. If no target is seen, the next set is tried. When all sets have been run, the FPGA terminates and waits for the next 50-millisecond event. This setup simplifies testing and improves reliability. A single vertex chip does the work of an entire assembly. Output products require minor processing to become range and velocity. This technology is the heart of the Terminal Descent Sensor, which is an integral part of the Entry Decent and Landing system for MSL. In addition, it is a strong candidate for manned landings on Mars or the Moon.

Berkun, Andrew C.↗
NASA NTRS1986

Computer vision for robots; Proceedings of the Meeting, Cannes, France, December 2-6, 1985

The conference presents papers on segmentation techniques, three-dimensional recognition and representation, processing image sequences, and navigation and mobility. Particular attention is given to determining the pose of an object, adaptive least squares correlation with geometrical constraints, and the reliable formation of feature vectors for two-dimensional shape representation. Other topics include the real-time tracking of a target moving on a natural textured background, computer vision for the guidance of roving robots, and integrating sensory data for object recognition tasks.

Faugeras, O. D.↗
NASA NTRS1991

Image based tracking approaches to AR/C at the Johnson Space Center

Automated Rendezvous and Capture (AR&C) requires the determination of the six degrees of freedom relating two free bodies. Sensor systems that can provide such information have varying sizes, weights, power requirements, complexities and accuracies. One type of sensor system which can provide several key advantages is an image based tracking system, or better known as a machine vision system. By image based tracking we mean that the sensor is some imaging device such as one or more video cameras, from which the tracking parameters necessary to support the rendezvous and capture operations (range, attitude, etc.) can be derived. Image based tracking offers many advantages such as relative hardware simplicity and reprogrammability. These advantages must be weighed against the disadvantages of these systems, such as limited operational range, poorer accuracy at greater distances and sensitivity to lighting conditions. However, with properly designed algorithms and targets these disadvantages can be minimized for many important applications. Rigorous testing in realistic environments can further increase the robustness and reliability of these systems. This presentation describes the facilities used at JSC to support AR&C image based tracking development and the details of our binocular stereo approach to image based tracking.

Fisher, Timothy E.↗
NASA NTRSDate not supplied

Feasibility Testing of Silver Electrolysis for Disinfection of Spacecraft Potable Water Systems

Anodic dissolution of silver electrodes, or “silver electrolysis,” is being investigated as a means of introducing biocidal silver into potable water on exploration spacecraft. A proof-of-concept prototype of a silver electrolysis reactor was developed, and feasibility was demonstrated for imparting a target silver concentration into a spacecraft water system. Prototype testing showed that the primary initial concerns related to the technology - inefficiencies of electrolysis in low conductivity water, the potential formation of resistive oxides on the electrode surfaces, and the potential for release of electrolytically-generated silver particles to the effluent water - were not problematic over the duration of the feasibility testing. The testing also demonstrated advantages of the technology, including the ability to consistently deliver silver at targeted concentrations and the ability to directly correlate the silver concentration to measurements of water conductivity. On the other hand, the reliability of the system has not yet been demonstrated. During prototype testing, intermittent periods of poor reactor performance manifested as a decrease in voltage accompanied by a decrease in silver output. It was determined that the cause of this behavior was silver-based deposits on inter-electrode wetted surfaces forming a conductive “bridge” between electrodes. Ongoing testing and refinement of the prototype reactor design seek to elucidate the root cause the bridging phenomenon and identify associated mitigation strategies. Once resolved, long-term performance testing is planned as part of continued development of the electrolytic silver dosing system.

Silver↗
NASA NTRS1998

Issues and Methods for Assessing COTS Reliability, Maintainability, and Availability

Many vendors produce products that are not domain specific (e.g., network server) and have limited functionality (e.g., mobile phone). In contrast, many customers of COTS develop systems that am domain specific (e.g., target tracking system) and have great variability in functionality (e.g., corporate information system). This discussion takes the viewpoint of how the customer can ensure the quality of COTS components. In evaluating the benefits and costs of using COTS, we must consider the environment in which COTS will operate. Thus we must distinguish between using a non-mission critical application like a spreadsheet program to produce a budget and a mission critical application like military strategic and tactical operations. Whereas customers will tolerate an occasional bug in the former, zero tolerance is the rule in the latter. We emphasize the latter because this is the arena where there are major unresolved problems in the application of COTS. Furthermore, COTS components may be embedded in the larger customer system. We refer to these as embedded systems. These components must be reliable, maintainable, and available, and must be with the larger system in order for the customer to benefit from the advertised advantages of lower development and maintenance costs. Interestingly, when the claims of COTS advantages are closely examined, one finds that to a great extent these COTS components consist of hardware and office products, not mission critical software [1]. Obviously, COTS components are different from custom components with respect to one or more of the following attributes: source, development paradigm, safety, reliability, maintainability, availability, security, and other attributes. However, the important question is whether they should be treated differently when deciding to deploy them for operational use; we suggest the answer is no. We use reliability as an example to justify our answer. In order to demonstrate its reliability, a COTS component must pass the same reliability evaluations as the custom components, otherwise the COTS components will be the weakest link in the chain of components and will be the determinant of software system reliability. The challenge is that there will be less information available for evaluating COTS components than for custom components but this does not mean we should despair and do nothing. Actually, there is a lot we can do even in the absence of documentation on COTS components because the customer will have information about how COTS components are to be used in the larger system. To illustrate our approach, we will consider the reliability, maintainability, and availability (RMA) of COTS components as used in larger systems. Finally, COTS suppliers might consider increasing visibility into their products to assist customers in determining the components' fitness for use in a particular application. We offer ideas of information that would be useful to customers, and what vendors might do to provide it.

Schneidewind, Norman F.↗
NASA NTRS1996

The fragmentation of 510 MeV/nucleon iron-56 in polyethylene. II. Comparisons between data and a model

The results of a Monte Carlo model for calculating fragment fluences and LET spectra are compared to data taken with 600 MeV/nucleon iron ions incident on an accelerator beamline configured for irradiation of biological samples, with no target and with 2, 5 and 8 cm of polyethylene. The model uses a multi-generation nuclear fragmentation code, coupled with a formulation of ionization energy loss based on the Bethe-Bloch equation. In the region where the data are reliable and the experimental acceptance is well understood, many of the features of the experimental spectra are well replicated by the model. To obtain good agreement with the experimental data, the model must allow for at least two generations of fragment production in the target.

NASA Discipline Number 99-99↗
NASA NTRS1999

A Simple Method for Nucleon-Nucleon Cross Sections in a Nucleus

A simple reliable formalism is presented for obtaining nucleon-nucleon cross sections within a nucleus in nuclear collisions for a given projectile and target nucleus combination at a given energy for use in transport, Monte Carlo, and other calculations. The method relies on extraction of these values from experiments and has been tested and found to give excellent results.

Tripathi, R. K.↗
NASA NTRS1999

Medium Modified Nucleon-Nucleon Cross Sections in a Nucleus

A simple reliable formalism is presented for obtaining nucleon-nucleon cross sections within a nucleus in nuclear collisions for a given projectile and target nucleus combination at a given energy for use in transport, Monte Carlo and other calculations. The method relies on extraction of these values from experiments and has been tested for absorption experiments to give excellent results.

Tripathi, R. K.↗
NASA NTRS2017

NASA's Solar System Treks: Online Portals for Planetary Mapping and Modeling

NASA's Solar System Treks are a suite of web-based of lunar and planetary mapping and modeling portals providing interactive visualization and analysis tools enabling mission planners, planetary scientists, students, and the general public to access mapped lunar data products from past and current missions for the Moon, Mars, Vesta, and more. New portals for additional planetary bodies are being planned. This presentation will recap significant enhancements to these toolsets during the past year and look ahead to future features and releases. Moon Trek is a new portal replacing its predecessor, the Lunar Mapping and Modeling Portal (LMMP), that significantly upgrades and builds upon the capabilities of LMMP. It features greatly improved navigation, 3D visualization, fly-overs, performance, and reliability. Additional data products and tools continue to be added. These include both generalized products as well as polar data products specifically targeting potential sites for NASA's Resource Prospector mission as well as for missions being planned by NASA's international partners. The latest release of Mars Trek includes new tools and data products requested by NASA's Planetary Science Division to support site selection and analysis for Mars Human Landing Exploration Zone Sites. Also being given very high priority by NASA Headquarters is Mars Trek's use as a means to directly involve the public in upcoming missions, letting them explore the areas the agency is focusing upon, understand what makes these sites so fascinating, follow the selection process, and get caught up in the excitement of exploring Mars. Phobos Trek, the latest effort in the Solar System Treks suite, is being developed in coordination with the International Phobos/Deimos Landing Site Working Group, with landing site selection and analysis for JAXA's MMX (Martian Moons eXploration) mission as a primary driver.

Day, Brian↗
NASA NTRS2008

Range Imaging without Moving Parts

Range-imaging instruments of a type now under development are intended to generate the equivalent of three-dimensional images from measurements of the round-trip times of flight of laser pulses along known directions. These instruments could also provide information on characteristics of targets, including roughnesses and reflectivities of surfaces and optical densities of such semi-solid objects as trees and clouds. Unlike in prior range-imaging instruments based on times of flight along known directions, there would be no moving parts; aiming of the laser beams along the known directions would not be accomplished by mechanical scanning of mirrors, prisms, or other optical components. Instead, aiming would be accomplished by using solid-state devices to switch input and output beams along different fiber-optic paths. Because of the lack of moving parts, these instruments could be extraordinarily reliable, rugged, and long-lasting. An instrument of this type would include an optical transmitter that would send out a laser pulse along a chosen direction to a target. An optical receiver coaligned with the transmitter would measure the temporally varying intensity of laser light reflected from the target to determine the distance and surface characteristics of the target. The transmitter would be a combination of devices for generating precise directional laser illumination. It would include a pulsed laser, the output of which would be coupled into a fiber-optic cable with a fan-out and solid-state optical switches that would enable switching of the laser beam onto one or more optical fibers terminated at known locations in an array on a face at the focal plane of a telescope. The array would be imaged by the telescope onto the target space. The receiver optical system could share the aforementioned telescope with the transmitter or could include a separate telescope aimed in the same direction as that of the transmitting telescope. In either case, light reflected from the target would be focused by the receiver optical system onto an array of optical fibers matching the array in the transmitter. These optical fibers would couple the received light to one or more photodetector( s). Optionally, the receiver could include solid-state optical switches for choosing which optical fiber(s) would couple light to the photodetector(s). This instrument architecture is flexible and can be optimized for a wide variety of applications and levels of performance. For example, it is scalable to any number of pixels and pixel resolutions and is compatible with a variety of ranging and photodetection methodologies, including, for example, ranging by use of modulated (including pulsed and encoded) light signals. The use of fixed arrays of optical fibers to generate controlled illumination patterns would eliminate the mechanical complexity and much of the bulk of optomechanical scanning assemblies. Furthermore, digital control of the selection of the fiber-optic pathways for the transmitted beams could afford capabilities not seen in previous three-dimensional range-imaging systems. Instruments of this type could be specialized for use as, for example, proximity detectors, three-dimensional robotic vision systems, airborne terrain-mapping systems, and inspection systems.

Blair, J. Bryan↗
NASA NTRS2003

Reliable Transport over SpaceWire for James Webb Space Telescope (JWST) Focal Plane Electronics (FPE) Network

NASA's James Webb Space Telescope (JWST) faces difficult technical and budgetary challenges to overcome before it is scheduled launch in 2010. The Integrated Science Instrument Module (ISIM), shares these challenges. The major challenge addressed in this paper is the data network used to collect, process, compresses and store Infrared data. A total of 114 Mbps of raw information must be collected from 19 sources and delivered to the two redundant data processing units across a twenty meter deployed thermally restricted interface. Further data must be transferred to the solid-state recorder and the spacecraft. The JWST detectors are kept at cryogenic temperatures to obtain the sensitivity necessary to measure faint energy sources. The Focal Plane Electronics (FPE) that sample the detector, generate packets from the samples, and transmit these packets to the processing electronics must dissipate little power in order to help keep the detectors at these cold temperatures. Separating the low powered front-end electronics from the higher-powered processing electronics, and using a simple high-speed protocol to transmit the detector data minimize the power dissipation near the detectors. Low Voltage Differential Signaling (LVDS) drivers were considered an obvious choice for physical layer because of their high speed and low power. The mechanical restriction on the number cables across the thermal interface force the Image packets to be concentrated upon two high-speed links. These links connect the many image packet sources, Focal Plane Electronics (FPE), located near the cryogenic detectors to the processing electronics on the spacecraft structure. From 12 to 10,000 seconds of raw data are processed to make up an image, various algorithms integrate the pixel data Loss of commands to configure the detectors as well as the loss of science data itself may cause inefficiency in the use of the telescope that are unacceptable given the high cost of the observatory. This combination of requirements necessitates a redundant, fault tolerant, high- speed, low mass, low power network with a low Bit error Rate(1E-9- 1E-12). The ISIM systems team performed many studies of the various network architectures that meeting these requirements. The architecture selected uses the Spacewire protocol, with the addition of a new transport and network layer added to implement end-to-end reliable transport. The network and reliable transport mechanism must be implemented in hardware because of the high average information rate and the restriction on the ability of the detectors to buffer data due to power and size restrictions. This network and transport mechanism was designed to be compatible with existing Spacewire links and routers so that existing equipment and designs may be leveraged upon. The transport layer specification is being coordinated with European Space Agency (ESA), Spacewire Working Group and the Consultative Committee for Space Data System (CCSDS) PlK Standard Onboard Interface (SOIF) panel, with the intent of developing a standard for reliable transport for Spacewire. Changes to the protocol presented are likely since negotiations are ongoing with these groups. A block of RTL VHDL that implements a multi-port Spacewire router with an external user interface will be developed and integrated with an existing Spacewire Link design. The external user interface will be the local interface that sources and sinks packets onto and off of the network (Figure 3). The external user interface implements the network and transport layer and handles acknowledgements and re-tries of packets for reliable transport over the network. Because the design is written in RTL, it may be ported to any technology but will initially be targeted to the new Actel Accelerator series (AX) part. Each link will run at 160 Mbps and the power will be about 0.165 Watt per link worst case in the Actel AX.

Rakow, Glenn↗