Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “thermal switches”

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 199 records · Page 11

Materials Selection Principles for Designing Electro‐Thermal Neurons

Artificial neurons exhibiting volatile threshold switching and action potential‐like oscillations are crucial for brain‐inspired computing. While Complimentary Metal‐Oxide‐Semiconductor (CMOS)‐based strategies require hundreds of transistors to simulate each neuron, neuronal oscillations arise spontaneously in individual electro‐thermal devices due to nonlinearities like the Mott transition in VO 2 . Despite improved understanding of the physics, quantitative connections between neuronal performance and material properties remain under‐explored, preventing predictive neuron design and rational materials selection. In this work, a physics‐aware forward design methodology is developed for interrogating a wide palette of materials with properties varying by orders of magnitude, and their performance (high frequency, high dynamical reconfigurability and low power) under external circuit and device geometry constraints is assessed. The space of viable materials is identified to be much larger than previously recognized, with candidates from a range of materials classes, including Ge, GaP and MoS 2 . CMOS‐compatible performance (such as 100 GHz oscillating frequencies) can be achieved with CMOS‐compatible node sizes (≈10 nm). Finally, combinations of material properties yielding desired neuronal performance under uncertain design constraints are considered. This work solidifies forward design principles for electro‐thermal neuron devices, a necessary pre‐condition for inverse design from desired neuronal performance to required materials properties.

compact model↗

RF Reference Switch for Spaceflight Radiometer Calibration

The goal of this technology is to provide improved calibration and measurement sensitivity to the Soil Moisture Active Passive Mission (SMAP) radiometer. While RF switches have been used in the past to calibrate microwave radiometers, the switch used on SMAP employs several techniques uniquely tailored to the instrument requirements and passive remote-sensing in general to improve radiometer performance. Measurement error and sensitivity are improved by employing techniques to reduce thermal gradients within the device, reduce insertion loss during antenna observations, increase insertion loss temporal stability, and increase rejection of radar and RFI (radio-frequency interference) signals during calibration. The two legs of the single-pole double-throw reference switch employ three PIN diodes per leg in a parallel-shunt configuration to minimize insertion loss and increase stability while exceeding rejection requirements at 1,413 MHz. The high-speed packaged diodes are selected to minimize junction capacitance and resistance while ensuring the parallel devices have very similar I-V curves. Switch rejection is improved by adding high-impedance quarter-wave tapers before and after the diodes, along with replacing the ground via of one diode per leg with an open circuit stub. Errors due to thermal gradients in the switch are reduced by embedding the 50-ohm reference load within the switch, along with using a 0.25-in. (approximately equal to 0.6-cm) aluminum prebacked substrate. Previous spaceflight microwave radiometers did not embed the reference load and thermocouple directly within the calibration switch. In doing so, the SMAP switch reduces error caused by thermal gradients between the load and switch. Thermal issues are further reduced by moving the custom, highspeed regulated driver circuit to a physically separate PWB (printed wiring board). Regarding RF performance, previous spaceflight reference switches have not employed high-impedance tapers to improve rejection. The use of open-circuit stubs instead of a via to provide an improved RF short is unique to this design. The stubs are easily tunable to provide high rejection at specific frequencies while maintaining very low insertion loss in-band.

Knuble, Joseph↗

Towards Accelerated Aging Methodologies and Health Management of Power MOSFETs (Technical Brief)

Understanding aging mechanisms of electronic components is of extreme importance in the aerospace domain where they are part of numerous critical subsystems including avionics. In particular, power MOSFETs are of special interest as they are involved in high voltage switching circuits such as drivers for electrical motors. With increased use of electronics in aircraft control, it becomes more important to understand the degradation of these components in aircraft specific environments. In this paper, we present an accelerated aging methodology for power MOSFETs that subject the devices to indirect thermal overstress during high voltage switching. During this accelerated aging process, two major modes of failure were observed - latch-up and die attach degradation. In this paper we present the details of our aging methodology along with details of experiments and analysis of the results.

Celaya, Jose R.↗

Spatiotemporal Thermal Coupling in VO 2 Device Arrays

Correlated oxides such as VO 2 exhibit an electrically driven insulator–metal transition (IMT) that underlies their promise for neuromorphic and memory devices. Yet the IMT is not a uniform bulk process but a spatiotemporal phenomenon in which local heating nucleates filaments, contracts or dissolves them with the electric field, and couples to the environment. In this work, we directly image the VO 2 IMT dynamics by mid-wave infrared, thermography synchronized with electrical transport, resolving device temperature with micrometer spatial and microsecond temporal resolution. At the single-device level, we capture the full cycle of filament nucleation, contraction, and relaxation during current/voltage-driven resistive switching. At the array level, we show that heat propagates across etched gaps with an effective length scale of ∼131 µm, enabling cooperative behaviors among electrically isolated devices. Short-range distanced devices exhibit mutual filament attraction and sequential dissolution, while long-range distanced devices differentiate into distinct roles: drivers that initiate switching, cooperative responders that undergo assisted self-oscillations, and passive reporters that record the thermal field. Furthermore, these results reframe thermal crosstalk, long regarded as parasitic, as an intrinsic coupling channel and design principle for organizing collective switching behaviors, with direct implications for emergent circuit functionality in neuromorphic and unconventional computing architectures.

coupling↗

Thermal Management of Wide-Bandgap Semiconductor Amplifiers Used for Plasma Heating and Control

Princeton Fusion Systems (PFS) has designed, built, and tested a Load Switch printed circuit board (PCB) to demonstrate the capabilities of 2 kV silicon carbide (SiC) cascodes in development by Qorvo towards plasma heating and control applications. Initial tests have been conducted at low power (~100 W) for validation with thermal finite element analysis (FEA) modeling performed by the National Renewable Energy Laboratory (NREL). Comparisons of experimental data with the thermal modeling results, along with considerations for operating in plasma systems, will be discussed.

CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SU↗

Device-Level Multidimensional Thermal Dynamics With Implications for Current and Future Wide Bandgap Electronics

Researchers have been extensively studying wide-bandgap (WBG) semiconductor materials such as gallium nitride (GaN) with an aim to accomplish an improvement in size, weight, and power of power electronics beyond current devices based on silicon (Si). However, the increased operating power densities and reduced areal footprints of WBG device technologies result in significant levels of self-heating that can ultimately restrict device operation through performance degradation, reliability issues, and failure. Typically, self-heating in WBG devices is studied using a single measurement technique while operating the device under steady-state direct current measurement conditions. However, for switching applications, this steady-state thermal characterization may lose significance since the high power dissipation occurs during fast transient switching events. Therefore, it can be useful to probe the WBG devices under transient measurement conditions in order to better understand the thermal dynamics of these systems in practical applications. In this work, the transient thermal dynamics of an AlGaN/GaN high electron mobility transistor (HEMT) were studied using thermoreflectance thermal imaging and Raman thermometry. Also, the proper use of iterative pulsed measurement schemes such as thermoreflectance thermal imaging to determine the steady-state operating temperature of devices is discussed. These studies are followed with subsequent transient thermal characterization to accurately probe the self-heating from steady-state down to submicrosecond pulse conditions using both thermoreflectance thermal imaging and Raman thermometry with temporal resolutions down to 15 ns.

42 ENGINEERING↗

Dynamic operation of metal-supported solid oxide electrolysis cells

Symmetric-structure metal-supported solid oxide fuel cells and electrolysis cells (MS-SOFCs, MS-SOECs) offer several advantages over conventional solid oxide cells, including the use of inexpensive materials, high mechanical strength, and rapid ramp-up ability. Aggressive operation of MS-SOCs in fuel cell mode is well-established, including extremely fast start-up, redox tolerance, and imbalanced pressure. Here, we extend dynamic operation to MS-SOCs in SOEC mode with high steam content for both small button cells and a large rectangular cell, including: steam cycling, thermal cycling, redox cycling and power cycling. Steam cycling entailed switching between 3:97 and 50:50 steam:hydrogen ratio. For thermal cycling, the temperature was rapidly varied between 150°C and 700°C for 50 cycles. Redox cycling involved switching the steam side gas between 50 % humidified H 2 and 50 % humidified N 2 for 5 cycles. Power cycling was performed by operating the cell under variable current density, resulting in cell voltage between 1.3V and 2.8V. Degradation rates for each testing strategy were compared to a baseline cell, and found to be similar. In conclusion, the excellent tolerance to dynamic operation increases confidence that MS-SOECs will be compatible with dynamic or intermittent renewable resources.

08 HYDROGEN↗

Staying Competitive in Clean Manufacturing: Insights on Barriers from Industry Interviews

While industrial emissions research has historically focused on energy-intensive sectors like steel, cement, and chemicals, this study addresses a critical gap by examining barriers across all the manufacturing industry in the U.S. Sectors like food processing, retail, plastics, and transportation face unique challenges distinct from heavy industry, operating on thin margins with limited bargaining power while experiencing heightened consumer and stakeholder pressure for improved environmental responsibility. Through structured interview data collection process and using quantitative ratings and qualitative analysis, this research identifies and categorizes emission reduction barriers across four key themes: financial, technical, organizational, and regulatory. Unlike energy-intensive industries that may pursue hydrogen or carbon capture technologies, discrete manufacturing industry like automotive, electrical and electronics, and machine manufacturers typically focus on energy efficiency, electrification of thermal processes, and alternate fuel switching, solutions better aligned with their lower-temperature processes and distributed facility profiles. The study’s primary contribution lies in documenting specific barrier manifestations within organizations and identifying proven mitigation strategies that companies have successfully implemented or observed among peers.

business competitiveness↗

A proposed magnetic digital temperature transducer, volume 1

A study has been made of the feasibility of using the discontinuous permeability versus temperature characteristics of some magnetic materials for a digital temperature transducer and a thermally controlled ON-OFF switch. Simple logic converts the number of output pulse to a digital word recognizable by the system. Efforts have been concentrated on materials with Curie temperatures between 0 and 100 C. One compound has the composition Mn(5-x)Fe(x)Ge3 where the amount of iron determines the transition temperature. The other compound is Ni-Zn ferrite and has the compositon Ni(1-x)Zn(x)Fe(1.95)O4 where the nickel: zinc ratio determines the transition temperature. A detailed report of materials prepared is presented. Toroidal inductors of the material have been constructed and the change in inductance with temperature measured. In view of these initial measurements, it is felt that a transducer utilizing the permeability versus temperature characteristics of these materials has promise as a reliable and sensitive solid state digital temperature transducer.

Collier, T. E.↗

Electrical power system WP-04

Viewgraphs on Space Station Freedom Electrical Power System (EPS) WP-40 are presented. Topics covered include: key EPS technical requirements; photovoltaic power module systems; solar array assembly; blanket containment box and box positioning subassemblies; solar cell; bypass diode assembly; Kapton with atomic oxygen resistant coating; sequential shunt unit; gimbal assembly; energy storage subsystem; thermal control subsystem; direct current switching unit; integrated equipment assembly; PV cargo element; PMAD system; and PMC and AC architecture.

Nored, Donald L.↗

Environmental testing of a Q-switched Nd:YLF laser and a Nd:YAG ring laser

A Q-switched Nd:YLF laser (model 110-02) and a Nd:YAG ring laser (model 120-04) from Lightwave Electronics were subjected to thermal and vibration tests similar to what can be expected during launch and flight on a spacecraft. Even though these lasers were not designed for space flight, environmental tests were performed to identify major design weaknesses. Laser performance (output power, energy, pulsewidth, lasing threshold etc.) were measured prior to and after thermal vibration tests. Average output power of the Q-switched laser degraded 15-20 percent after thermal tests and an additional 20-25 percent after vibration tests. Post diagnostic tests revealed that degradation of the Q-switched laser was due to misalignment of pump focusing optics and the laser cavity.

Robinson, D. L.↗

Electronic assembly having sectional thermal management

The first board section comprises a switching module with heat-generating semiconductor switches associated with a first operational temperature range. The first board section has a first conductive layer of a first thickness. The second board section comprises a plurality of capacitors mounted on a second circuit board. The second board section has conductive traces for interconnecting the capacitors as a network. The capacitors are associated with a second operational temperature range that is lower than the first operational temperature range. A thermal isolation intermediary forms a barrier between, or adjoining, the first board section and the second board section, where the first board section and the second board section are spaced part from each other by the thermal isolation intermediary.

Schmit, Christopher J.↗

Ion beam etching dependence of spin-orbit torque memory devices with switching current densities reduced by Hf interlayers

We report on the fabrication of nanoscale, three-terminal in-plane spin–orbit torque switching devices with low switching current densities. Critical parameters in the fabrication process, including the ion beam etching angle and time, were optimized to avoid fabrication defects and improve device yield. Measurements of the magnetic field and current-induced switching behavior of the tunnel junctions demonstrate a sensitivity to the nanopillar aspect ratio, which dictates the nanopillars’ anisotropy and thermal stability. Additionally, we show that the current density required for switching can be reduced and the device thermal stability increased by inserting Hf interlayers into the heterostructure. Micromagnetic simulations are generally consistent with the experimentally observed switching behavior, suggesting an increase in the interfacial perpendicular anisotropy at the CoFeB/MgO interface and the reduction in the Dzyaloshinskii–Moriya interaction at the W/CoFeB interface by the Hf interlayers.

36 MATERIALS SCIENCE↗

NASA Tech Briefs, April 2010

Topics covered include: Active and Passive Hybrid Sensor; Quick-Response Thermal Actuator for Use as a Heat Switch; System for Hydrogen Sensing; Method for Detecting Perlite Compaction in Large Cryogenic Tanks; Using Thin-Film Thermometers as Heaters in Thermal Control Applications; Directional Spherical Cherenkov Detector; AlGaN Ultraviolet Detectors for Dual-Band UV Detection; K-Band Traveling-Wave Tube Amplifier; Simplified Load-Following Control for a Fuel Cell System; Modified Phase-meter for a Heterodyne Laser Interferometer; Loosely Coupled GPS-Aided Inertial Navigation System for Range Safety; Sideband-Separating, Millimeter-Wave Heterodyne Receiver; Coaxial Propellant Injectors With Faceplate Annulus Control; Adaptable Diffraction Gratings With Wavefront Transformation; Optimizing a Laser Process for Making Carbon Nanotubes; Thermogravimetric Analysis of Single-Wall Carbon Nanotubes; Robotic Arm Comprising Two Bending Segments; Magnetostrictive Brake; Low-Friction, Low-Profile, High-Moment Two-Axis Joint; Foil Gas Thrust Bearings for High-Speed Turbomachinery; Miniature Multi-Axis Mechanism for Hand Controllers; Digitally Enhanced Heterodyne Interferometry; Focusing Light Beams To Improve Atomic-Vapor Optical Buffers; Landmark Detection in Orbital Images Using Salience Histograms; Efficient Bit-to-Symbol Likelihood Mappings; Capacity Maximizing Constellations; Natural-Language Parser for PBEM; Policy Process Editor for P(sup 3)BM Software; A Quality System Database; Trajectory Optimization: OTIS 4; and Computer Software Configuration Item-Specific Flight Software Image Transfer Script Generator.

Source record↗

Operation of an ADR Using Helium Exchange Gas as a Substitute for a Failed Heat Switch

The Soft X-ray Spectrometer (SXS) is one of four instruments on the Japanese Astro-H mission, which is currently planned for launch in late 2015. The SXS will perform imaging spectroscopy in the soft X-ray band (0.3-12 keV) using a 6 6 pixel array of microcalorimeters cooled to 50 mK. The detectors are cooled by a 3-stage adiabatic demagnetization refrigerator (ADR) that rejects heat to either a superfluid helium tank (at 1.2 K) or to a 4.5 K Joule-Thomson (JT) cryocooler. Four gas-gap heat switches are used in the assembly to manage heat flow between the ADR stages and the heat sinks. The engineering model (EM) ADR was assembled and performance tested at NASA/GSFC in November 2011, and subsequently installed in the EM dewar at Sumitomo Heavy Industries, Japan. During the first cooldown in July 2012, a failure of the heat switch that linked the two colder stages of the ADR to the helium tank was observed. Operation of the ADR requires some mechanism for thermally linking the salt pills to the heat sink, and then thermally isolating them. With the failed heat switch unable to perform this function, an alternate plan was devised which used carefully controlled amounts of exchange gas in the dewar's guard vacuum to facilitate heat exchange. The process was successfully demonstrated in November 2012, allowing the ADR to cool the detectors to 50 mK for hold times in excess of 10 h. This paper describes the exchange-gas-assisted recycling process, and the strategies used to avoid helium contamination of the detectors at low temperature.

Adiabatic demagnetization↗

TARDIS: Acelerating TVAC Transitions

"Large spacecraft components, including instruments, require long durations to transition between temperature plateaus during TVAC (Thermal Vacuum) testing. This is especially true for cryogenic instruments whose operating temperatures are extremely low. Due to the T4 relation, using radiative heat transfer alone for temperature transitions to cryogenic temperatures is extremely time consuming. The Wide Field Instrument (WFI) on the upcoming Roman Space Telescope (RST) is one such cryogenic instrument. The TARDIS (Thermal Acceleration Rate Device for Integrated Systems) is a heat switch device which will be used during the WFI TVAC test campaign in order to decrease WFI transition times. Over the course of the planned ___ week WFI instrument-level TVAC testing, TARDIS is being estimated to save ___ days of test time. By reducing the total TVAC duration, TARDIS is providing significant cost and schedule savings to the RST WFI project. Based on the successful design of the LUCY L’Ralph AZQ Heat Switch, TARDIS can provide both high conductivity for temperature transitions and low conductivity Zero-Q for thermal balances. This is achieved by use of a mechanical clamp heat switch and actively controlled cold plate. Using this method, TARDIS is estimated to be able to change its conductance from approximately 0.20 W/K to ¬¬0.002 W/K, for a turndown ratio of 100. This paper details the design, analysis, and testing of TARDIS. It also previews the operation of TARDIS in the upcoming WFI TVAC test campaign. "

TVAC, Heat Switch↗

A Bioinspired Artificial Injury Response System Based on a Robust Polymer Memristor to Mimic a Sense of Pain, Sign of Injury, and Healing

Abstract Flexible electronic skin with features that include sensing, processing, and responding to stimuli have transformed human–robot interactions. However, more advanced capabilities, such as human‐like self‐protection modalities with a sense of pain, sign of injury, and healing, are more challenging. Herein, a novel, flexible, and robust diffusive memristor based on a copolymer of chlorotrifluoroethylene and vinylidene fluoride (FK‐800) as an artificial nociceptor (pain sensor) is reported. Devices composed of Ag/FK‐800/Pt have outstanding switching endurance >10 6 cycles, orders of magnitude higher than any other two‐terminal polymer/organic memristors in literature (typically 10 2 –10 3 cycles). In situ conductive atomic force microscopy is employed to dynamically switch individual filaments, which demonstrates that conductive filaments correlate with polymer grain boundaries and FK‐800 has superior morphological stability under repeated switching cycles. It is hypothesized that the high thermal stability and high elasticity of FK‐800 contribute to the stability under local Joule heating associated with electrical switching. To mimic biological nociceptors, four signature nociceptive characteristics are demonstrated: threshold triggering, no adaptation, relaxation, and sensitization. Lastly, by integrating a triboelectric generator (artificial mechanoreceptor), memristor (artificial nociceptor), and light emitting diode (artificial bruise), the first bioinspired injury response system capable of sensing pain, showing signs of injury, and healing, is demonstrated.

36 MATERIALS SCIENCE↗

The output beam quality of a Q-switched Nd:glass slab laser

The authors have constructed and tested a flashlamp pumped, Q-switched, Nd:glass zigzag slab laser. The thermally induced optical distortion through the slab is minimized by uniform pumping and cooling and the use of corrective pump shields at the slab ends. The laser spatial output for Q-switched resonators has been measured and modeled. It is shown that a larger aperture planar oscillator has an output divergence many times above the diffraction limit. Operation as a one-dimensional unstable resonator in the wide direction of the slab allows the efficient extraction of energy in a high-quality beam. Near-diffraction-limited laser output of 5 J at 4 Hz is achieved with a resonator that includes an intracavity telescope to correct for residual defocusing in the thin direction of the slab.

Reed, Murray K.↗