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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 1,225 records · Page 68

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NASA NTRS1984

Simplified dc to dc converter

A dc to dc converter which can start with a shorted output and which regulates output voltage and current is described. Voltage controlled switches directed current through the primary of a transformer the secondary of which includes virtual reactance. The switching frequency of the switches is appropriately varied to increase the voltage drop across the virtual reactance in the secondary winding to which there is connected a low impedance load. A starting circuit suitable for voltage switching devices is provided.

Gruber, R. P.↗

NASA NTRS1984

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

Weizer, V. G.↗

NASA NTRS1984

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

Weizer, V. G.↗

DOE OSTI2025

Capacitor Design for Self-Resonant Coils for Long-Distance Wireless Power Transfer System

In this paper, an integrated capacitor design is proposed for higher-order resonant tank topologies for self-resonant coils, such as series, parallel, LCC, LLC, etc. The capacitor is one of the large, lossy, and thermally vulnerable components of a high-frequency resonant tank, and designing a high-voltage, thermally stable resonant capacitor can be highly challenging. Designing the extremely high-voltage capacitor as an integral part of the coil reduces the size and complexity of the coil assembly. This paper proposes a low-loss PCB-based high-voltage capacitor design to achieve that target, which can be implemented as an integral part of the coil. The proposed capacitor designs are simulated using Multiphysics FEA and tested experimentally. A 23 kV, 133 pF capacitor prototype was built and tested as part of a 1 kW long-distance wireless charging system. The test results verify the capacitor’s voltage, current, and thermal resiliency performance.

Mohammad, Mostak [ORNL] (ORCID:0000000256388783)↗

DOE OSTI2024

Pure edge-dislocation half-loops in low-temperature Ga⁢N for V-defect formation

Lateral injection of carriers through semipolar crystallographic planes into c-plane QWs is one of the new frontiers in III-N light-emitting diodes (LEDs), especially for long wavelengths. Strategic use of V-defects has proven to be the most promising method for lateral injection, and creating optimal V-defect structure and density is an important research area for reducing forward voltage and increasing wall plug efficiency. Here, in this article, we present a novel method for forming V-defects in nominally unstressed low-temperature Ga⁢N through the generation of pure edge-dislocation half-loops. We present a detailed material science analysis of the loops via scattering-contrast electron microscopy. The loops have pure-edge character with Burgers vector 1/3 ⁢⟨$11\bar{2}0$⟩, and form in a sessile orientation on {$11\bar{2}0$} a-planes. The two arms of the loops are inclined such that the extra half-planes face down toward the growth substrate. The dislocation loops can be used to intentionally form V-defects through conditions of kinetically limited growth: these conditions also favor nucleation of V-defects at ∼100% of other threading dislocations in the Ga⁢N templates. Patterned sapphire substrates (PSS) are one of the most important substrates for III-N LED growth because of their superior light extraction. However, due to its low threading dislocation density, PSS have not been used extensively for V-defect LEDs. This work provides a pathway for improved control of V-defect formation and density on LEDs grown on sapphire with the goal of enabling uniform lateral injection in these V-defect engineered LEDs with low forward voltage, including PSS for high light extraction.

LEDs↗

NASA NTRS1980

Tailored emitter, low-resistivity, ion-implanted silicon solar cells

Open-circuit voltages as high as 0.645 V (AM0, 25 C) have been obtained by a new process developed for low-resistivity silicon. The process utilizes high-dose phosphorus implantation followed by furnace annealing and simultaneous oxide growth. The effect of the thermally grown oxide is a reduction of surface recombination velocity; the oxide also acts as a moderately efficient antireflection (AR) coating. Boron-doped, float-zone silicon with resistivities from 0.1 to 1.0 (omega)(cm) has been processed according to this sequence; results show that the highest open-circuit voltage is obtained with 0.1(omega)(cm) starting material. The effects of Auger recombination and bandgap narrowing caused by high doping concentrations in the n(+)junction region have been investigated by implanting phosphorus over a wide range of dose levels. The effects of emitter-phosphorus concentrations tailored to optimize electric fields in the emitter have also been investigated.

Minnucci, J. A.↗

NASA NTRS2002

Charging of the International Space Station Due to Its High Voltage Solar Arrays

The International Space Station (ISS) has the highest voltage solar arrays ever flown in Low Earth Orbit (LEO). The ISS power system (and structure) ground is at the negative end of the 160 V solar arrays. Due to plasma current collection balance that must be maintained in LEO, it is possible for a spacecraft to charge negative of the ambient plasma by up to its entire solar array voltage (-160 V for ISS).

Ferguson, Dale C.↗

DOE OSTI2026

Analog-to-digital converter based on voltage-controlled superconducting devices

The increasing demand for cryogenic electronics in superconducting and quantum computing systems calls for ultra-energy-efficient data conversion architectures that remain functional at deep cryogenic temperatures. Here, in this work, we present the first design of a voltage-controlled superconducting flash analog-to-digital converter (ADC) based on a voltage-controlled quantum-enhanced Josephson junction field-effect transistor (JJFET). Exploiting its strong gate tunability and transistor-like behavior, the JJFET offers a scalable alternative to conventional current-controlled superconducting devices while aligning naturally with CMOS-style design methodologies. Building on our previously developed Verilog-A compact model calibrated to experimental data, we design and simulate a three-bit JJFET-based flash ADC targeted for integration within cryogenic control and readout circuitry in quantum computing. The core comparator block is realized through careful bias current selection and augmented with a three-terminal nanocryotron to precisely define reference voltages. Cascaded JJFET comparators ensure robust voltage gain, cascadability, and logic-level restoration across stages. Simulation results demonstrate accurate quantization behavior with ultra-low power dissipation, underscoring the feasibility of voltage-driven superconducting mixed-signal circuits. This work establishes a critical step toward unifying superconducting logic and data conversion, paving the way for scalable cryogenic architectures in quantum–classical co-processors, low-power artificial intelligence accelerators, and next-generation energy-constrained computing platforms.

Analog-to-digital converter↗

NASA NTRS1990

High-voltage plasma interactions calculations using NASCAP/LEO

This paper reviews four previous simulations (two laboratory and two space-flight) of interactions of a high-voltage spacecraft with a plasma under low-earth orbit conditions, performed using a three-dimensional computer code NASCAP/LEO. Results show that NASCAP/LEO can perform meaningful simulations of high-voltage plasma interactions taking into account three-dimensional effects of geometry, spacecraft motion, and magnetic field. Two new calculations are presented: (1) for current collection by 1-mm pinholes in wires (showing that a pinhole in a wire can collect far more current than a similar pinhole in a flat plate); and (2) current collection by Charge-2 mother vehicle launched in December 1985. It is shown that the Charge-2 calculations predicted successfully ion collection at negative bias, the floating potential of a probe outside or inside the sheath under negative bias conditions, and magnetically limited electron collection under electron beam operation at high altitude.

Mandell, M. J.↗

NASA NTRS1996

Planet-B: Technical notes and drawings

The design of the transformer designated as T101 (061-0351) in the Filament/Bias module (061-0119) in the Planet-B NMS instrument was verified because of the differences from the GCMS and INMS instrument designs. A breadboard of a representation of the Hybrid 2301065, Bias Drive A driving a 2N3700 NPN transistor, with dual 75V secondaries, with loads, was used to test the circuit. The initial transformer design that was wound with bifilar secondaries was too unstable to test. The second 1408 transformer with a split bobbin and the feedback winding below the primary was also found to be unstable. (It was nearly impossible to keep the circuit from squeeging). The third transformer tested has the feedback on the outside of the resonant winding. The primary goal of the design was to have as tight a magnetic coupling as possible to the resonant winding, and as loose a coupling as possible to the primary. Further, the circuit AC ground is connected to the winding at the feedback end of the secondary winding. This transformer proved to be very stable - it is virtually impossible to make this design squeg. An emitter resistor (Rl29A) was added to this circuit, as referenced to the GCMS design, to protect Q102 from thermal runaway in the event of a turn on with a non- resonate circuit or load short. This was verified to protect Q102 for at least 30 seconds in the event of a short. Approximately 1% of the 4lmW input power is lost in this protection resistor under normal operation. The circuit was verified to operate normally when a radiated Q102 (2N3700), (low Beta) transistor was substituted for the normal 2N3700. It should be noted that the monitored drive voltage went to approximately 2.7V with this low gain transistor.

Carignan, George R.↗

NASA NTRS2011

Coaxial charged particle energy analyzer

A non-dispersive electrostatic energy analyzer for electrons and other charged particles having a generally coaxial structure of a sequentially arranged sections of an electrostatic lens to focus the beam through an iris and preferably including an ellipsoidally shaped input grid for collimating a wide acceptance beam from a charged-particle source, an electrostatic high-pass filter including a planar exit grid, and an electrostatic low-pass filter. The low-pass filter is configured to reflect low-energy particles back towards a charged particle detector located within the low-pass filter. Each section comprises multiple tubular or conical electrodes arranged about the central axis. The voltages on the lens are scanned to place a selected energy band of the accepted beam at a selected energy at the iris. Voltages on the high-pass and low-pass filters remain substantially fixed during the scan.

Kelly, Michael A.↗

DOE OSTI2022

Design Power Control Strategies of Grid-Forming Inverters for Microgrid Application

This paper develops and compares two control schemes in the application control layer of a non-phase-locked loop (non-PLL) grid-forming (GFM) inverter to gain insight and understanding into how the two schemes affect the dynamic responses of GFM inverters and the transition operation of microgrids. The first scheme adopts power tracking based on an outer current loop in grid-connected mode and droop control in islanded mode, and the second uses droop control in both grid-connected and islanded modes. Analytical study is developed to compare the performance of these two strategies from various aspects, including fundamental differences, transition operation, power tracking, and P-Q capability with low point-of-common-coupling (PCC) voltages. Extensive simulation testing is carried out to validate the control performance of these two control strategies, and the simulation testing confirms the findings of the analytic study. Finally, the second strategy is recommended because of its superior control performance and ease of implementation. The analysis and results are useful in developing reliable control schemes for non-PLL GFM inverters because increasing numbers of inverters will work as non-PLL grid-forming sources in future grids because of their improved stability and reliability.

grid-forming↗

NASA NTRS1987

Power supply conditioning circuit

A power supply conditioning circuit that can reduce Periodic and Random Deviations (PARD) on the output voltages of dc power supplies to -150 dBV from dc to several KHz with no measurable periodic deviations is described. The PARD for a typical commercial low noise power supply is -74 dBV for frequencies above 20 Hz and is often much worse at frequencies below 20 Hz. The power supply conditioning circuit described here relies on the large differences in the dynamic impedances of a constant current diode and a zener diode to establish a dc voltage with low PARD. Power supplies with low PARD are especially important in circuitry involving ultrastable frequencies for the Deep Space Network.

Primas, L. E.↗

NASA NTRS1978

A quick response four decade logarithmic high-voltage stepping supply

An improved high-voltage stepping supply, for space instrumentation is described where low power consumption and fast settling time between steps are required. The high-voltage stepping supply, utilizing an average power of 750 milliwatts, delivers a pair of mirror images with 64 level logarithmic outputs. It covers a four decade range of + or - 2500 to + or - 0.29 volts having an output stability of + or - 0.5 percent or + or - 20 millivolts for all line load and temperature variations. The supply provides a typical step setting time of 1 millisecond with 100 microseconds for the lower two decades. The versatile design features of the high-voltage stepping supply provides a quick response staircase generator as described or a fixed voltage with the option to change levels as required over large dynamic ranges without circuit modifications. The concept can be implemented up to + or - 5000 volts. With these design features, the high-voltage stepping supply should find numerous applications where charged particle detection, electro-optical systems, and high voltage scientific instruments are used.

Doong, H.↗

NASA NTRS2003

Solar Electric Propulsion Mission Architectures

This presentation reviews Solar Electric Propulsion (SEP) Mission Architectures with a slant towards power system technologies and challenges. The low-mass, high-performance attributes of SEP systems have attracted spacecraft designers and mission planners alike and have led to a myriad of proposed Earth orbiting and planetary exploration missions. These SEP missions are discussed from the earliest missions in the 1960's, to first demonstrate electric thrusters, to the multi-megawatt missions envisioned many decades hence. The technical challenges and benefits of applying high-voltage arrays, thin film and low-intensity, low-temperature (LILT) photovoltaics, gossamer structure solar arrays, thruster articulating systems and microsat systems to SEP spacecraft power system designs are addressed. The overarching conclusion from this review is that SEP systems enhance, and many times enable, a wide class of space missions.

Kerslake, Thomas W.↗

NASA NTRS2004

Communications Transceivers for Venus Surface Missions

The high temperature of the surface of Venus poses many difficulties. Previous Venus landers have only operated for short durations before succumbing to the heat. NASA Glenn Research Center conducted a study on communications for long duration Venus surface missions. I report the findings in this presentation. Current technology allows production of communications transceivers that can operate on the surface of Venus, at temperatures above 450 C and pressures of over 90 atmospheres. While these transceivers would have to be relatively simple, without much of the advanced signal processing often used in modern transceivers, since current and near future integrated circuits cannot operate at such high temperatures, the transceivers will be able to meet the requirements of proposed Venus Surface mission. The communication bands of interest are High Frequency or Very High Frequency (HFNHF) for communication between Venus surface and airborne probes (including surface to surface and air to air), and Ultra High Frequency (UHF) to Microwave bands for communication to orbiters. For HFNHF, transceivers could use existing vacuum tube technology. The packaging of the vacuum tubes may need modification, but the internal operating structure already operates at high temperatures. Using metal vacuum structures instead of glass, allows operation at high pressure. Wide bandgap transistors and diodes may be able to replace some of the thermionic components. VHF communications would be useful for line-of- sight operations, while HF would be useful for short-wave type communications using the Venusian ionosphere. UHF and microwave communications use magnetically focused thermionic devices, such as traveling wave tubes (TWTs), magnetron (M-type) amplifiers, and klystrons for high power amplifiers, and backward wave oscillators (BWOs) and reflex klystrons for oscillators. Permanent magnets are already in use in industry that can operate at 500 C. These magnets could focus electron beam tubes on the surface of Venus. While microwave windows will need to be designed for the high pressure, diamond windows have already been demonstrated, so high-pressure microwave windows can be designed and built. Thus, all of these devices could be useful for Venus surface missions. Current electronic power conditioners to supply the high voltages used in these microwave devices cannot operate at high temperatures, but earlier electronic power conditioners that used vacuum tubes can be modified to work at high temperature. Evaluating the various devices in this study, the M-type traveling wave tube (where a traveling wave structure is used in a crossed-field device, similar to the Amplitron used on the Apollo missions) stood out for the high power amplifier since it requires a single high voltage, simplifying the power supply design. Since the receiver amplifier is a low power amplifier, the loss of efficiency in linear beam devices without a depressed collector (and thus needing a single high voltage) is not important; a low noise TWT is a possible solution. Before solid-state microwave amplifiers were available, such TWTs were built with a 1-2 dB noise figure. A microwave triode or transistor made from a wide bandgap material may be preferable, if available. Much of the development work needed for Venusian communication devices will need to focus on the packaging of the devices, and their connections, but the technology is available to build transceivers that can operate on the surface of Venus indefinitely.

Force, Dale A.↗

NASA NTRS2016

Silicon Emitter Needle and Array Design for Indium Electrospray Arrays for Spacecraft Propulsion

A design for silicon microfabricated emitter arrays was developed for electrospray thrusters for indium propellant in compact architectures with scalable thrust, low mass and volume, high specific impulse and high efficiency operation. The design elements include tip height, height uniformity across the array, tip radii, axial groove depth, tip angle, emitter shank sidewall angle and number of emitters. They were derived from commercial liquid metal ion source designs and modeling, fabrication and test results. The most critical results of the emitter array design analysis suggest that microfabricated silicon emitter array emitters should have a height greater than 280 microns with a height uniformity of +/-10 microns, a tip half angle of 49° for uniform turn-on voltages and current across the array, low beam divergence and high mass utilization efficiency. Elements of the design were fabricated and demonstrated in single emitter and in 400 element emitter arrays to validate the design, fabrication and performance capability. The design height and uniformity of arrays was demonstrated for 85% of the emitters in a prototype array. Required tip and sidewall angles and groove depths have been microfabricated. Single microfabricated silicon emitters demonstrated better performance in current and voltage characteristics than commercially available liquid metal ion sources. Microfabricated emitters and arrays demonstrated the required current and stability performance to enable the MEP thruster development for indium propellant.

Marrese-Reading, Colleen M.↗

NASA NTRS1961

Magnetic Ignition of Pulsed Gas Discharges in Air of Low Pressure in a Coaxial Plasma Gun

The effect of an axial magnetic field on the breakdown voltage of a coaxial system of electrodes has been investigated by earlier workers. For low values of gas pressure times electrode spacing, the breakdown voltage is decreased by the application of the magnetic field. The electron cyclotron radius now assumes the role held by the mean free path in nonmagnetic discharges and the breakdown voltage becomes a function of the magnetic flux density. In this paper the dependence of the formative time lag as a function of the magnetic flux density is established and the feasibility of using a magnetic field for igniting high-voltage, high-current discharges is shown through theory and experiment. With a 36 microfarad capacitor bank charged to 48,000 volts, a peak current of 1.3 x 10( exp 6) amperes in a coaxial type of plasma gun was achieved with a current rise time of only 2 microseconds.

Thom, Karlheinz↗