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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Granular Media-Based Tunable Passive Vibration Suppressor

and vibration suppression device is composed of statically compressed chains of spherical particles. The device superimposes a combination of dissipative damping and dispersive effects. The dissipative damping resulting from the elastic wave attenuation properties of the bulk material selected for the granular media is independent of particle geometry and periodicity, and can be accordingly designed based on the dissipative (or viscoelastic) properties of the material. For instance, a viscoelastic polymer might be selected where broadband damping is desired. In contrast, the dispersive effects result from the periodic arrangement and geometry of particles composing a linear granular chain. A uniform (monatomic) chain of statically compressed spherical particles will have a low-pass filter effect, with a cutoff frequency tunable as a function of particle mass, elastic modulus, Poisson fs ratio, radius, and static compression. Elastic waves with frequency content above this cutoff frequency will exhibit an exponential decay in amplitude as a function of propagation distance. System design targeting a specific application is conducted using a combination of theoretical, computational, and experimental techniques to appropriately select the particle radii, material (and thus elastic modulus and Poisson fs ratio), and static compression to satisfy estimated requirements derived for shock and/or vibration protection needs under particular operational conditions. The selection of a chain of polymer spheres with an elastic modulus .3 provided the appropriate dispersive filtering effect for that exercise; however, different operational scenarios may require the use of other polymers, metals, ceramics, or a combination thereof, configured as an array of spherical particles. The device is a linear array of spherical particles compressed in a container with a mechanism for attachment to the shock and/or vibration source, and a mechanism for attachment to the article requiring isolation (Figure 1). This configuration is referred to as a single-axis vibration suppressor. This invention also includes further designs for the integration of the single-axis vibration suppressor into a six-degree-of-freedom hexapod "Stewart"mounting configuration (Figure 2). By integrating each singleaxis vibration suppressor into a hexapod formation, a payload will be protected in all six degrees of freedom from shock and/or vibration. Additionally, to further enable the application of this device to multiple operational scenarios, particularly in the case of high loads, the vibration suppressor devices can be used in parallel in any array configuration.

Dillon, Robert P.↗
NASA NTRS1977

Optical integrated-circuit tester

Computer controlled device can check typical medium scale unit in less than one minute. System scans integrated circuit chip with narrow beam of light while simultaneously scanning reference chip.

Micka, E. A.↗
NASA NTRS2013

Radiation Tests of Single Photon Avalanche Diode for Space Applications

Single photon avalanche diodes (SPADs) have been recently studied as photodetectors for applications in space missions. In this presentation we report the results of radiation hardness test on large area SPAD (actual results refer to SPADs having 500 micron diameter). Dark counts rate as low as few kHz at −10 degC has been obtained for the 500 micron devices, before irradiation. We performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim SPAD devices have been irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons. The test performed show that large area SPADs are very sensitive to proton doses as low as 2×10(exp 8) (1 MeV eq) n/cm2 with a significant increase in dark counts rate (DCR) as well as in the manifestation of the "random telegraph signal" effect. Annealing studies at room temperature (RT) and at 80 degC have been carried out, showing a high decrease of DCR after 24-48 h at RT. Lower protons doses in the range 1-10×10(exp 7) (1 MeV eq) n/cm(exp 2) result in a lower increase of DCR suggesting that the large-area SPADs tested in this study are well suitable for application in low-inclination LEO, particularly useful for gamma-ray astrophysics.

radiation hardness↗
NASA NTRS2014

HgCdTe e-APD Detector Arrays with Single Photon Sensitivity for Space Lidar Applications

A multi-element HgCdTe electron initiated avalanche photodiode (e-APD) array has been developed for space lidar applications. The detector array was fabricated with 4.3-μm cutoff HgCdTe which covered a spectral response from 0.4 to 4.3 μm. We have characterized a 4x4 detector array with 80 μm square elements and an integrated custom cryogenic silicon read-out integrated circuit (ROIC). The device operated at 77K inside a small closed-cycle Dewar. Measurements showed a unity gain quantum efficiency of about 90% at 1.55 μm. The bulk dark current of the HgCdTe e-APD at 77K was less than 50,000 input referred electrons/s at 12 V APD bias where the APD gain was 620 and the measured noise equivalent power (NEP) was 0.4 fW/Hz1/2. The electrical bandwidth of the ROIC was about 6 MHz, which was chosen to match the laser pulse width of our CO2 lidar. Even with the relatively low bandwidth, the high APD gain and low dark current enabled the device to detect single photon events. Because the APD was biased below the break-down voltage, the detector output was linear with the input optical signal and there was no dead-time and afterpulsing. A new series of HgCdTe e-APDs are being developed with a much wider bandwidth ROIC and higher gain HgCdTe e-APD array, which is expected to give a much better performance in linear mode photon counting applications.

HgCdTe↗
NASA NTRS1980

Modified Reference SPS with Solid State Transmitting Antenna

The development of solid state microwave power amplifiers for a solar power satellite transmitting antenna is discussed. State-of-the-art power-added efficiency, gain, and single device power of various microwave solid state devices are compared. The GaAs field effect transistors and the Si-bipolar transistors appear potentially feasible for solar power satellite use. The integration of solid state devices into antenna array elements is examined and issues concerning antenna integration and consequent satellite configurations are examined.

Woodcock, G. R.↗
NASA NTRS2009

Alternative Packaging for Back-Illuminated Imagers

An alternative scheme has been conceived for packaging of silicon-based back-illuminated, back-side-thinned complementary metal oxide/semiconductor (CMOS) and charge-coupled-device image-detector integrated circuits, including an associated fabrication process. This scheme and process are complementary to those described in "Making a Back-Illuminated Imager With Back-Side Connections" (NPO-42839), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 38. To avoid misunderstanding, it should be noted that in the terminology of imaging integrated circuits, "front side" or "back side" does not necessarily refer to the side that, during operation, faces toward or away from a source of light or other object to be imaged. Instead, "front side" signifies that side of a semiconductor substrate upon which the pixel pattern and the associated semiconductor devices and metal conductor lines are initially formed during fabrication, and "back side" signifies the opposite side. If the imager is of the type called "back-illuminated," then the back side is the one that faces an object to be imaged. Initially, a back-illuminated, back-side-thinned image-detector is fabricated with its back side bonded to a silicon handle wafer. At a subsequent stage of fabrication, the front side is bonded to a glass wafer (for mechanical support) and the silicon handle wafer is etched away to expose the back side. The frontside integrated circuitry includes metal input/output contact pads, which are rendered inaccessible by the bonding of the front side to the glass wafer. Hence, one of the main problems is to make the input/output contact pads accessible from the back side, which is ultimately to be the side accessible to the external world. The present combination of an alternative packaging scheme and associated fabrication process constitute a solution of the problem.

Pain, Bedabrata↗
NASA NTRS1972

In-flight comparisons of boundary-layer and wake measurement probes for incompressible flow

The results are presented of in-flight comparisons of a number of boundary-layer and wake measurement probes suitable for low-speed flight-test investigations. The tested boundary-layer probes included a traversing total-pressure probe and a hot-film probe mounted on an internally-mounted drive mechanism, a curved and a straight boundary-layer rake, and a traversing hot-film probe with an externally-mounted drive mechanism. The wake measuring devices included a traversing, self-aligning probe, a wake rake, and an integrating wake rate. The boundary-layer data are compared with a common reference velocity profile and comments given regarding the accuracy of the static-pressure and total-pressure measurements. Discussions on the various calibration presentations used with hot-wire and hot-film sensors and various aspects of improving the accuracy of hot-film sensor results are given in the appendix of this report.

Mertaugh, L. J., Jr.↗
NASA NTRS1977

Low-power anemometer

Device allows wind speeds to be measured with less power by alternating hot-wire or hot-film heating periods with measurement periods. System includes reference auxiliary circuits to generate V sub ref and ramp voltage (E sub 3) and reference half of bridge circuit. Circuit permits use of several sensing films with common temperature compensation sensor.

Gilje, R. I.↗
NASA NTRS1980

An investigation for the development of an integrated optical data preprocessor

A laboratory model of a 16 channel integrated optical data preprocessor was fabricated and tested in response to a need for a device to evaluate the outputs of a set of remote sensors. It does this by accepting the outputs of these sensors, in parallel, as the components of a multidimensional vector descriptive of the data and comparing this vector to one or more reference vectors which are used to classify the data set. The comparison is performed by taking the difference between the signal and reference vectors. The preprocessor is wholly integrated upon the surface of a LiNbO3 single crystal with the exceptions of the source and the detector. He-Ne laser light is coupled in and out of the waveguide by prism couplers. The integrated optical circuit consists of a titanium infused waveguide pattern, electrode structures and grating beam splitters. The waveguide and electrode patterns, by virtue of their complexity, make the vector subtraction device the most complex integrated optical structure fabricated to date.

Verber, C. M.↗
NASA NTRS2017

Oxygen Candle Background for Subs and Space

"At any time and without warning, a submarine may have to remain submerged for several days on account of the presence of the enemy, or rough weather, or serious accident to the machinery. Fortunately such occurrences are rare; but every commanding officer must be prepared to meet such an emergency that will afford his men the greatest possible chance of survival." Reference (1) This quotation is taken from a review of submarine air purification technology published by the Bureau of Medicine and Surgery in 1919. At that time, the U.S. Navy had just begun to experiment with possible air purification devices and supplies of oxygen that might permit submarines to remain submerged longer that the untreated closed atmosphere would allow. Submariners were exposed to elevated levels of carbon dioxide and reduced levels of oxygen that would be considered completely unacceptable by current standards. It was a different world, but humans are still humans, and the requirements for safe and effective functioning in a self-contained environment are really unchanged. The maximum submergence time for submarines as published in that work was approximately 48 hours, reference (1) In early submarines, the preferred supply of oxygen was 1800 psig compressed gas bled into the boat as needed, references (1,2). The need for added oxygen was occasionally "measured" by the physiological impact on the crew rather than a reliable instrument, reference (1). The design of submarine oxygen supply was limited to approximately 25 day submerged operation, reference (2). It was not until 1958 that U.S. submarines were able to carry out dives beyond that period and necessitated new sources of oxygen, reference (2). A curious second source of oxygen at the time was compressed air vessels that were bled into the boat while "vitiated" air (air with reduced oxygen and elevated carbon dioxide) from the opposite end of the boat was compressed into waiting empty vessels, reference (1). The periodic use of pressurized air to control oxygen caused swings in ambient pressure that was uncomfortable to the crew, reference (1). As early as 1919, liquid oxygen was a commercially available product and its use on submarines was contemplated, reference (1). It is interesting that even at this date, 1919, the danger of oils or greases when exposed to compressed or liquid oxygen was recognized: "One precaution must be always taken. No oil or grease should be used in the gauge or fittings or a dangerous explosion may result."

Graf, John↗
NASA NTRS1963

Inertial rotation sensor

Mechanism for inertial rotation sensing device for measuring spectral lines of rotating atoms seen by rotating observer

ROTATING MACHINE↗
NASA NTRS1981

Development of a Shuttle Infrared Telescope Facility /SIRTF/ fine guidance sensor

Fine guidance technology development for the Shuttle Infrared Telescope Facility (SIRTF) centers upon the use of a single multiple-star-tracking sensor to provide the position information necessary to produce three-axis attitude control signals for precision payload pointing. The effort described in this paper is concerned with the development of a fine guidance sensor that employs a high-density charge-coupled imaging device for producing position information signals by using star fields. Multiple star position information produces three-axis position error signals that are used to update inertial reference gyros. The sensor employs advanced position interpolation algorithms to enhance field-of-view resolution and to correct for optical aberrations inherent in spatially chopped star images resulting from the telescope's movable secondary mirror. Operation of the sensor is under the control of a high-performance microcomputer that provides both autonomy and flexibility in a guidance application.

Salomon, P. M.↗
NASA NTRS2012

Virtual Ultrasound Guidance for Inexperienced Operators

Medical ultrasound or echocardiographic studies are highly operator-dependent and generally require lengthy training and internship to perfect. To obtain quality echocardiographic images in remote environments, such as on-orbit, remote guidance of studies has been employed. This technique involves minimal training for the user, coupled with remote guidance from an expert. When real-time communication or expert guidance is not available, a more autonomous system of guiding an inexperienced operator through an ultrasound study is needed. One example would be missions beyond low Earth orbit in which the time delay inherent with communication will make remote guidance impractical. The Virtual Ultrasound Guidance system is a combination of hardware and software. The hardware portion includes, but is not limited to, video glasses that allow hands-free, full-screen viewing. The glasses also allow the operator a substantial field of view below the glasses to view and operate the ultrasound system. The software is a comprehensive video program designed to guide an inexperienced operator through a detailed ultrasound or echocardiographic study without extensive training or guidance from the ground. The program contains a detailed description using video and audio to demonstrate equipment controls, ergonomics of scanning, study protocol, and scanning guidance, including recovery from sub-optimal images. The components used in the initial validation of the system include an Apple iPod Classic third-generation as the video source, and Myvue video glasses. Initially, the program prompts the operator to power-up the ultrasound and position the patient. The operator would put on the video glasses and attach them to the video source. After turning on both devices and the ultrasound system, the audio-video guidance would then instruct on patient positioning and scanning techniques. A detailed scanning protocol follows with descriptions and reference video of each view along with advice on technique. The program also instructs the operator regarding the types of images to store and how to overcome pitfalls in scanning. Images can be forwarded to the ground or other site when convenient. Following study completion, the video glasses, video source, and ultrasound system are powered down and stored. Virtually any equipment that can play back video can be used to play back the program. This includes a DVD player, personal computer, and some MP3 players.

Caine, Timothy↗
NASA NTRS2007

Evaluation of Hands-Free Devices for the Display of Maintenance Procedures

Over the past year, NASA's focus has turned to crewed long duration and exploration missions. On these journeys, crewmembers will be required to execute thousands of procedures to maintain life support systems, check out space suits, conduct science experiments, and perform medical exams. To support the many complex tasks crewmembers undertake in microgravity, NASA is interested in providing crewmembers a hands-free work environment to promote more efficient operations. The overarching objective is to allow crewmembers to use both of their hands for tasks related to their mission, versus holding a paper manual or interacting with a display. The use of advanced, hands-free tools will undoubtedly make the crewmembers task easier, but they can also add to overall task complexity if not properly designed. A leading candidate technology for supporting a hands-free environment is the Head-Mounted Display (HMD). A more recent technology (e-book reader) that could be easily temp-stowed near the work area is also a potential hands-free solution. Previous work at NASA involved the evaluation of several commercially available HMDs for visual quality, comfort, and fit, as well as suitability for use in microgravity. Based on results from this work, three HMDs were selected for further evaluation (along with an e-book reader), using International Space Station (ISS)-like maintenance procedures. Two evaluations were conducted in the Space Station Mockup and Trainer Facility (SSMTF) located at the NASA Johnson Space Center (building 9). The SSMTF is a full scale, medium fidelity replica of the pressurized portions of the ISS. It supports crew training such as ingress and egress, habitability, and emergency procedures. In each of the two evaluations, the participants performed two maintenance procedures. One maintenance procedure involved inspecting air filters in a life support system and replacing them with a clean filter if one were found to be contaminated. The second maintenance procedure focused on working in a confined space; specifically, pulling down a rack to inspect wiring configurations, and rewiring in a different pattern. The maintenance procedures were selected to assess mobility, tool use, and access to multiple document sources during task performance. That is, the participant had to move from rack to rack, use a wrench, a camera, etc., replace components, and refer to diagrams to complete tasks. A constraint was imposed that the ISS-like format of the procedures was to be retained, and not modified or optimized for the electronic device ("plug and play" approach). This was based on future plans to test with real procedures on ISS.

Ronald B Hoffman↗
NASA NTRS1976

Prediction methods for jet V/STOL propulsion aerodynamics

The current status of prediction methods for propulsive flows and propulsion-induced effects which occur on jet V/STOL aircraft is reviewed. Among the major topics studied are flows in propulsive ducts, propulsion-induced ground and thermal effects, aerodynamic loads induced during V/STOL and transition flight, flow vectoring devices, and thrust augmented ejector and lift-fan studies. The current predictive capability in jet V/STOL propulsion aerodynamics is assessed. Future research needs are identified, with particular reference to activities that can improve the usefulness of prediction methods for jet V/STOL aircraft.

Platzer, M. F.↗
NASA NTRS1980

Laser beam manifold and particle photography system for use in fluid velocity measurements

A laser beam manifold and particle photography system has been developed for use in fluid velocity measurements. The laser manifold is a device which transforms a single laser beam into several uniform parallel beams. By orienting two manifolds mutually perpendicular, an optical grid can be formed which acts as a reference for fluid velocity measurements. This optical grid is for all practical purposes totally nonperturbing to the flow. Tracer particles moving in the plane of the grid are then photographed to yield fluid velocities that can be measured relative to the optical grid. System construction and theory are presented.

Owen, R. B.↗
NASA NTRS1981

Use of vacuum tubes in test instrumentation for measuring characteristics of fast high-voltage semiconductor devices

Circuits are described that permit measurement of fast events occurring in power semiconductors. These circuits were developed for the dynamic characterization of transistors used in inductive-load switching applications. Fast voltage clamping using vacuum diodes is discussed, and reference is made to a unique circuit that was built for performing nondestructive, reverse-bias, second-breakdown tests on transistors.

Berning, D.↗
NASA NTRS1984

Pairwise Comparison of Voltage Sets

Optical preprocessor compares 16 incoming signals with reference voltages. Integrated optical substraction to take "vector difference" of two sets of analog voltages. Applications include satellite onboard processing of pictorial data so data not useful discardes; device recognizes presence of accessive cloud cover and signals hault to data transmission.

Verber, C. M.↗