Search NASA⌕ Search

SEARCH · Search NASA

Results for “device stability”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

NASA Tech Briefs, June 2011

Topics covered include: Wind and Temperature Spectrometry of the Upper Atmosphere in Low-Earth Orbit; Health Monitor for Multitasking, Safety-Critical, Real-Time Software; Stereo Imaging Miniature Endoscope; Early Oscillation Detection Technique for Hybrid DC/DC Converters; Parallel Wavefront Analysis for a 4D Interferometer; Schottky Heterodyne Receivers With Full Waveguide Bandwidth; Carbon Nanofiber-Based, High-Frequency, High-Q, Miniaturized Mechanical Resonators; Ultracapacitor-Based Uninterrupted Power Supply System; Coaxial Cables for Martian Extreme Temperature Environments; Using Spare Logic Resources To Create Dynamic Test Points; Autonomous Coordination of Science Observations Using Multiple Spacecraft; Autonomous Phase Retrieval Calibration; EOS MLS Level 1B Data Processing Software, Version 3; Cassini Tour Atlas Automated Generation; Software Development Standard Processes (SDSP); Graphite Composite Panel Polishing Fixture; Material Gradients in Oxygen System Components Improve Safety; Ridge Waveguide Structures in Magnesium-Doped Lithium Niobate; Modifying Matrix Materials to Increase Wetting and Adhesion; Lightweight Magnetic Cooler With a Reversible Circulator; The Invasive Species Forecasting System; Method for Cleanly and Precisely Breaking Off a Rock Core Using a Radial Compressive Force; Praying Mantis Bending Core Breakoff and Retention Mechanism; Scoring Dawg Core Breakoff and Retention Mechanism; Rolling-Tooth Core Breakoff and Retention Mechanism; Vibration Isolation and Stabilization System for Spacecraft Exercise Treadmill Devices; Microgravity-Enhanced Stem Cell Selection; Diagnosis and Treatment of Neurological Disorders by Millimeter-Wave Stimulation; Passive Vaporizing Heat Sink; Remote Sensing and Quantization of Analog Sensors; Phase Retrieval for Radio Telescope and Antenna Control; Helium-Cooled Black Shroud for Subscale Cryogenic Testing; Receive Mode Analysis and Design of Microstrip Reflectarrays; and Chance-Constrained Guidance With Non-Convex Constraints.

Source record↗
NASA NTRS2012

Performance and Characterization of Magnetic Penetration Thermometer Devices for X-Ray Spectroscopy

We are developing magnetic penetration thermometers (MPTs) for applications in X-ray astronomy. These non-dissipative devices consist of an X-ray absorber in good thermal contact to a superconducting thin film with a transition temperature around T=100mK. A microfabricated superconducting planar inductor underneath is used to store a persistent current and couple the superconductor's diamagnetic response to a readout SQUID. The strong temperature dependence of the diamagnetic response make these devices suitable for highly sensitive macroscopic thermometers that are capable of achieving very high energy resolution. We present results achieved with MPTs consisting of MoAu bilayer sensors attached to overhanging square 250 micron by 250 micron gold absorbers that have demonstrated an energy resolution of delta E_FWHM=2.3eV at an X-ray energy of 5.9keV. A similar device has shown delta E_FWHM=2.0eV at 1.5 keV. Under certain conditions and for specific device geometries, the temperature responsivity of the MPTs can vary on long timescales degrading the spectral performance. We present the characterization of different inductor geometries to optimize the design for the highest possible temperature sensitivity and compare different device designs with respect to responsivity stability.

Porst, J. -P.↗
NASA NTRS2017

Practical Applications of Cables and Ropes in the ISS Countermeasures System

National Aeronautics and Space Administration (NASA) uses exercise countermeasures on the International Space Station (ISS) to maintain crew health and combat the negative effects of long-duration spaceflight on the human body. Most ISS exercise countermeasures system (CMS) equipment rely heavily on the use of textile and wire ropes to transmit resistive loads and provide stability in a microgravity environment. For a variety of reasons, including challenges in simulating microgravity environments for testing and limits on time available for life cycle testing, the textiles and wire ropes have contributed significantly to on-orbit planned and unplanned maintenance time. As a result, continued ground testing and on-orbit experience since the first expedition on the ISS in 2000 provide valuable data and lessons learned in materials selection, applications, and design techniques to increase service life of these ropes. This paper will present a review of the development and failure history of textile and wire ropes for four exercise countermeasure systems-the Treadmill with Vibration Isolation and Stabilization (TVIS) System, Cycle Ergometer with Vibration Isolation and Stabilization (CEVIS) System, Interim Resistive Exercise Device (IRED), and the Advanced Resistive Exercise Device (ARED)-to identify lessons learned in order to improve future systems. These lessons learned, paired with thorough testing on the ground, offer a forward path towards reduced maintenance time and up-mass for future space missions.

Svetlik, Randall G.↗
NASA NTRS2020

Motion Sickness and Concerns for Urban Air Mobility Vehicles: A Literature Review

Motion sickness is a general term for a constellation of signs and symptoms, generally due to exposure to abrupt, periodic, or unnatural accelerations, especially when traveling in a vehicle. Motion sickness results from a mismatch of the visual and nonvisual (vestibular and kinesthetic) information, the observed scene and the motion felt or lack of it. Motion sickness onset is associated with a pattern of physiological changes in heart rate, peripheral blood flow, respiration, and skin conductance and the pattern is repeatable for a particular subject but variable between subjects. Demographic factors such as gender and age that affect motion sickness are well known with children, women, and older adults more likely to be susceptible. Often motion sickness is assessed and quantified using variations of the motion sickness susceptibility questionnaires including the Pensacola Diagnostic Rating Scale and the Simulator Sickness Questionnaire. Even though symptoms are easily identified by such questionnaires, they commonly are subjective. Tools such as these questionnaires for screening individuals susceptible to motion sickness are useful, however, they are only mildly predictive. Moreover, models for predicting motion sickness, which have largely been developed for sea sickness, do not consider task characteristics. Predictions of motion sickness rates and prevalence for Urban Air Mobility (UAM) vehicles are not possible at present because data from actual flight or full-fidelity simulation are simply not yet available. Extrapolation from other modes of transportation (i.e., automobiles, buses, trains, boats, other types of aircraft) is difficult because of differences in the motion stimulus experienced, trip duration, and other factors. How UAM vehicles will change the social dynamics of passenger interaction and vehicle interior design changes (e.g., seat orientations) is unknown. Should motion sickness prove to be an issue, vehicle design modifications such as having passengers face forward, providing additional seat recline, giving each person their own climate control for airflow, perhaps ensuring the horizon is visible to all passengers (reducing visual occlusion by the headrest) and visually stabilizing displays on carry-on devices (smart phones, tablets, etc.) may benefit passengers. Several commercial companies provide wearable devices for physiological monitoring that have been validated and are suitable for use with passengers in UAM vehicles or high-fidelity simulators. Potential countermeasures for motion sickness include user-worn devices, anti-motion sickness medications, and non-pharmacological approaches such as biofeedback and Autogenic Feedback Training Exercise. Both simulator and in-vehicle UAM research is needed to evaluate the effectiveness of any potential countermeasure.

motion sickness↗
DOE OSTI2018

Fabrication of CeO2/PANI composites for high energy density supercapacitors

Highlights: • Fabrication of CeO{sub 2}/PANI composite was successfully prepared using easy solution mixing method. • Combinational approaches of rare earth oxides with conducting polymer composites posses’ excellent pseudocapacitive nature. • Superior specific capacitance, rate capacitance and cyclic stability. • Outstanding performance of asymmetric and symmetric devices. - Abstract: Combinational approaches of rare earth oxides with conducting polymer composites have gained vast attention in supercapacitor field due to the outstanding pseudocapacitive property. Here we detail the redox reaction based on CeO{sub 2}/polyaniline nanostructure to grasp the superior electrochemical nature of the composite. The CeO{sub 2}/polymer nanostructure showed the improved specific capacitance of 1452 F g{sup −1} at 2 A g{sup −1} when compared to pristine CeO{sub 2} (927 F g{sup −1} at 2 A g{sup −1}). The composite also maintains excellent rate capacitance (875 F g{sup −1} at 10 A g{sup −1}) and good cyclic stability upto 1500 cycles at high current density of 20 A g{sup −1}. Symmetric and asymmetric supercapacitor devices were fabricated using CeO{sub 2}/ PANI as an electrode. Moreover, the asymmetric supercapacitor possesses excellent specific capacity (256 F g{sup −1} at 2 mV s{sup −1}) with high energy density (75 Whkg{sup −1}) and high power density (566 Wkg{sup −1}). These results suggest a potential usefulness of CeO{sub 2}/ PANI composite exploit as an efficient electrode for supercapacitor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Perovskite on Silicon Tandem Solar Cells

Since installing solar panels costs more than the panels themselves, it is critically important to improve the efficiency of the panels so that fewer panels need to be installed. More than 90% of all panels being manufactured are made with silicon solar cells. The most promising approach to reach 27% is to upgrade the panels by adding a second set of cells with a larger band gap that can harvest the higher energy photons in the visible spectrum and generate a higher voltage than silicon is capable of generating. Perovskite semiconductors are very promising for low-cost tandems because they have high band gaps, can be rapidly printed from solutions and have been used to make 25% efficient cells by themselves. If we show that it is possible to make stable tandems with 30% efficiency using materials that could be deposited at low cost and that the energy yield will not be compromised, then private companies would be able to raise the capital needed to manufacture this technology. The main metrics for this project are the power conversion efficiency of a lab-scale perovskite/silicon tandem and the ability to maintain a high power conversion efficiency in perovskite solar cells after accelerated operational stability testing under maximum power point at elevated temperature and 1 sun illumination. In short, this project demonstrates improvements to the perovskite absorber layer, contacts for the perovskite solar cell, and transparent oxide layers for window electrodes to achieve tandem efficiencies of 25% after one year and 27% after two years. By the end of the project, we identify strategies to further improve light management in the tandem devices and outline a pathway to reach 30%.In parallel, stability testing is conducted to evaluate said absorber and contact layers in the perovskite top cell, demonstrating 1000 hours of operation with less than 10% degradation at 1 sun. Our work on this project has made a leading impact on the development of perovskite/silicon tandems. The triple halide perovskite that we developed using iodide, bromide, and chloride and published in Science in March 2020 has received significant interest from other experts in the field at conferences. We took a silicon bottom cell with 21% efficiency, a technology that is responsible for a $30 billion market, and improved it by 30% relative. In addition, we have demonstrated impressive stability of our perovskite semitransparent top cells used in the tandems, showing for the first time packaged devices that pass a variety of IEC stability tests including damp heat, temperature cycling, and UV exposure tests.

14 SOLAR ENERGY↗
NASA NTRSDate not supplied

Design of A Transition-Edge-Sensor-Based Thermal Stabilization Stage

Electrothermal feedback in a transition edge sensor suppresses thermal fluctuations in the TES and regions in close thermal contact. We designed a heavily-metallized, leg-isolated membrane with a TES which serves as a thermal stabilization stage that can be lithographically integrated with other devices. Through modeling, fabrication and test of prototype devices, we examine whether the noise reduction in this stage can reduce thermal fluctuations (e.g. 1/f noise) in the other components by providing a more stable base temperature. In one implementation, a leg-isolated TES bolometer of higher superconducting transition temperature (Tc) is encircled by a second membrane region which is metallized and thermally stabilized by a second, lower-Tc TES. We present fabrication results on the dual-Tc design and testing of the simultaneous biasing of a two-stage, two-TES device. We explore varied heat capacity of the thermally stabilized stage in the single pixel design. We also present other designs to evaluate the use of an outer thermal stabilization stage for multiple pixel arrangements.

Rachel Borrelli↗
DOE OSTI2022

Development of a Modular Tissue Phantom for Evaluating Vascular Access Devices

Central vascular access (CVA) may be critical for trauma care and stabilizing the casualty. However, it requires skilled personnel, often unavailable during remote medical situations and combat casualty care scenarios. Automated CVA medical devices have the potential to make life-saving therapeutics available in these resource-limited scenarios, but they must be properly designed. Unfortunately, currently available tissue phantoms are inadequate for this use, resulting in delayed product development. Here, we present a tissue phantom that is modular in design, allowing for adjustable flow rate, circulating fluid pressure, vessel diameter, and vessel positions. The phantom consists of a gelatin cast using a 3D-printed mold with inserts representing vessels and bone locations. These removable inserts allow for tubing insertion which can mimic normal and hypovolemic flow, as well as pressure and vessel diameters. Trauma to the vessel wall is assessed using quantification of leak rates from the tubing after removal from the model. Lastly, the phantom can be adjusted to swine or human anatomy, including modeling the entire neurovascular bundle. Overall, this model can better recreate severe hypovolemic trauma cases and subject variability than commercial CVA trainers and may potentially accelerate automated CVA device development.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2003

Carbon Nanotube Electrode Arrays For Enhanced Chemical and Biological Sensing

Applications of carbon nanotubes for ultra-sensitive electrical sensing of chemical and biological species have been a major focus in NASA Ames Center for Nanotechnology. Great progress has been made toward controlled growth and chemical functionalization of vertically aligned carbon nanotube arrays and integration into micro-fabricated chip devices. Carbon nanotube electrode arrays devices have been used for sub-attomole detection of DNA molecules. Interdigitated carbon nanotubes arrays devices have been applied to sub ppb (part per billion) level chemical sensing for many molecules at room temperature. Stability and reliability have also been addressed in our device development. These results show order of magnitude improvement in device performance, size and power consumption as compared to micro devices, promising applications of carbon nanotube electrode arrays for clinical molecular diagnostics, personal medical testing and monitoring, and environmental monitoring.

Han, Jie↗
DOE OSTI2024

Correlation of Band Bending and Ionic Losses in 1.68 eV Wide Band Gap Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) are promising for high‐efficiency tandem applications, but their long‐term stability, particularly due to ion migration, remains a challenge. Despite progress in stabilizing PSCs, they still fall short compared to mature technologies like silicon. This study explores how different piperazinium salt treatments using iodide, chloride, tosylate, and bistriflimide anions affect the energetics, carrier dynamics, and stability of 1.68 eV bandgap PSCs. Chloride‐based treatments achieved the highest power conversion efficiency (21.5%) and open‐circuit voltage (1.28 V), correlating with stronger band bending and n‐type character at the surface. At the same time, they showed reduced long‐term stability due to increased ionic losses. Tosylate‐treated devices offered the best balance, retaining 96.4% efficiency after 1000 h (ISOS‐LC‐1I). These findings suggest that targeted surface treatments can enhance both efficiency and stability in PSCs.

14 SOLAR ENERGY↗
DOE OSTI2017

Improved stability and efficiency of perovskite solar cells with submicron flexible barrier films deposited in air

Here in this paper, we report on submicron organosilicate barrier films produced rapidly in air by a scalable spray plasma process that improves both the stability and efficiency of perovskite solar cells. The plasma is at sufficiently low temperature to prevent damage to the underlying layers. Oxidizing species and heat from the plasma improve device performance by enhancing both interfacial contact and the conductivity of the hole transporting layer. The thickness of the barrier films is tunable and transparent over the entire visible spectrum. The morphology and density of the barrier are shown to improve with the addition of a fluorine-based precursor. Devices with submicron coatings exhibited significant improvements in stability, maintaining 92% of their initial power conversion efficiencies after more than 3000 h in dry heat (85 °C, 25% RH) while also being resistant to degradation under simulated operational conditions of continuous exposure to light, heat, and moisture. X-ray diffraction measurements performed while heating showed the barrier film dramatically slows the formation of PbI 2 . The barrier films also are compatible with flexible devices, exhibiting no signs of cracking or delamination after 10000 bending cycles on a 127 μm substrate with a bending radius of 1 cm.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Assessment of vertical stability for negative triangularity pilot plants

Abstract Negative triangularity (NT) tokamak configurations may be more susceptible to magneto-hydrodynamic instability, posing challenges for recent reactor designs centered around their favorable properties, such as improved confinement and operation free of edge-localized modes. In this work, we assess the vertical stability of plasmas with NT shaping and develop potential reactor solutions. When coupled with a conformal wall, NT equilibria are confirmed to be less vertically stable than equivalent positive triangularity (PT) configurations. Unlike PT, their vertical stability is degraded at higher poloidal beta. Furthermore, improvements in vertical stability at low aspect ratio do not translate to the NT geometry. NT equilibria are stabilized in PT vacuum vessels due to the increased proximity of the plasma and the wall on the outboard side, but this scenario is found to be undesirable due to reduced vertical gaps which give less spatial margin for control recovery. Instead, we demonstrate that informed positioning of passively conducting plates can lead to improved vertical stability in NT configurations on par with stability metrics expected in PT scenarios. An optimal setup for passive plates in highly elongated NT devices is presented, where plates on the outboard side of the device reduce vertical instability growth rates to 16% of their baseline value. For lower target elongations, integration of passive stabilizers with divertor concepts can lead to significant improvements in vertical stability. Plates on the inboard side of the device are also uniquely enabled in NT geometries, providing opportunity for spatial separation of vertical stability coils and passive stabilizers.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

High average power, highly brilliant laser-produced plasma source for soft X-ray spectroscopy

In this work, a novel laser-produced plasma source is presented which delivers pulsed broadband soft X-radiation in the range between 100 and 1200 eV. The source was designed in view of long operating hours, high stability, and cost effectiveness. It relies on a rotating and translating metal target and achieves high stability through an on-line monitoring device using a four quadrant extreme ultraviolet diode in a pinhole camera arrangement. The source can be operated with three different laser pulse durations and various target materials and is equipped with two beamlines for simultaneous experiments. Characterization measurements are presented with special emphasis on the source position and emission stability of the source. As a first application, a near edge X-ray absorption fine structure measurement on a thin polyimide foil shows the potential of the source for soft X-ray spectroscopy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1971

Improved relay chatter detector

Detector provides go/no-go sensing of momentary relay or contact opening during vibration testing. Device compares duration of unwanted openings to calibrated standard and lights indicator if standard is exceeded. Stability and reliability are higher than in any other comparable device.

Reynolds, R. K.↗
DOE OSTI2015

Kinetics of Ion Transport in Perovskite Active Layers and Its Implications for Active Layer Stability

Solar cells fabricated using alkyl ammonium metal halides as light absorbers have the right combination of high power conversion efficiency and ease of fabrication to realize inexpensive but efficient thin film solar cells. However, they degrade under prolonged exposure to sunlight. In this work, we show that this degradation is quasi-reversible, and that it can be greatly lessened by simple modifications of the solar cell operating conditions. We studied perovskite devices using electrochemical impedance spectroscopy (EIS) with methylammonium (MA)-, formamidinium (FA)-, and MAxFA$_{1–x}$ lead triiodide as active layers. From variable temperature EIS studies, we found that the diffusion coefficient using MA ions was greater than when using FA ions. Structural studies using powder X-ray diffraction (PXRD) show that for MAPbI 3 a structural change and lattice expansion occurs at device operating temperatures. On the basis of EIS and PXRD studies, we postulate that in MAPbI 3 the predominant mechanism of accelerated device degradation under sunlight involves thermally activated fast ion transport coupled with a lattice-expanding phase transition, both of which are facilitated by absorption of the infrared component of the solar spectrum. Using these findings, we show that the devices show greatly improved operation lifetimes and stability under white-light emitting diodes, or under a solar simulator with an infrared cutoff filter or with cooling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Stability of Solutions of Initial Boundary-Balue Problems of Aerohydroelasticity

In designing structures and devices interacting with the flow of gas or liquid, it is necessary to solve the problems associated with the investigation of the stability required for their functioning and operational reliability. The definition of stability of an elastic body taken in the article corresponds to Lyapunov’s concept of stability of a dynamical system. On the base of the proposed nonlinear mathematical model the dynamic stability of the elastic aileron of the wing taking into account the incident subsonic flow of gas or liquid (in an ideal model of an incompressible environment) is investigated. Also a nonlinear mathematical model of the device relating to the vibration technique, which is intended for intensification of technological processes, for example, the process of mixing, is considered. The action of these devices is based on the oscillations of elastic elements during the gas or liquid flow. The dynamic stability of the elastic element located on one wall of the flow channel with the subsonic flow of gas or liquid (in an ideal model of a compressible environment) is investigated. Both models are described by a coupled nonlinear system of differential equations for the unknown functions — the potential of the gas velocity and deformation of the elastic element. On the basis of the construction of functionals, we obtain the sufficient conditions of the stability, the imposed restrictions on the free-stream velocity of the gas, the flexural stiffness of the elastic element, and other parameters of the mechanical system. The examples of construction of the stability regions for particular parameters of the mechanical system are presented.

42 ENGINEERING↗
DOE OSTI2024

Isotope effects and Alfvén eigenmode stability in JET H, D, T, DT, and He plasmas

While much about Alfvén eigenmode (AE) stability has been explored in previous and current tokamaks, open questions remain for future burning plasma experiments, especially regarding exact stability threshold conditions and related isotope effects; the latter, of course, requiring good knowledge of the plasma ion composition. In the JET tokamak, eight in-vessel antennas actively excite stable AEs, from which their frequencies, toroidal mode numbers, and net damping rates are assessed. The effective ion mass can also be inferred using measurements of the plasma density and magnetic geometry. Thousands of AE stability measurements have been collected by the Alfvén Eigenmode Active Diagnostic in hundreds of JET plasmas during the recent Hydrogen, Deuterium, Tritium, DT, and Helium-4 campaigns. In this novel AE stability database, spanning all four main ion species, damping is observed to decrease with increasing Hydrogenic mass, but increase for Helium, a trend consistent with radiative damping as the dominant damping mechanism. These data are important for confident predictions of AE stability in both non-nuclear (H/He) and nuclear (D/T) operations in future devices. In particular, if radiative damping plays a significant role in overall stability, some AEs could be more easily destabilized in D/T plasmas than their H/He reference pulses, even before considering fast ion and alpha particle drive. Active MHD spectroscopy is also employed on select HD, HT, and DT plasmas to infer the effective ion mass, thereby closing the loop on isotope analysis and demonstrating a complementary method to typical diagnosis of the isotope ratio.

Alfvén eigenmodes↗