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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

SEXTANT X-Ray Pulsar Navigation Demonstration: Flight System and Test Results

The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology demonstration enhancement to the Neutron-star Interior Composition Explorer (NICER) mission. NICER is a NASA Explorer Mission of Opportunity that will be hosted on the International Space Station (ISS). SEXTANT will, for the first time, demonstrate real-time, on-board X-ray Pulsar Navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. This paper gives an overview of the SEXTANT system architecture and describes progress prior to environmental testing of the NICER flight instrument. It provides descriptions and development status of the SEXTANT flight software and ground system, as well as detailed description and results from the flight software functional and performance testing within the high-fidelity Goddard Space Flight Center (GSFC) X-ray Navigation Laboratory Testbed (GXLT) software and hardware simulation environment. Hardware-in-the-loop simulation results are presented, using the engineering model of the NICER timing electronics and the GXLT pulsar simulator-the GXLT precisely controls NASA GSFC's unique Modulated X-ray Source to produce X-rays that make the NICER detector electronics appear as if they were aboard the ISS viewing a sequence of millisecond pulsars

Pulsar↗
NASA NTRSDate not supplied

The Adaptable, Deployable, Entry and Placement Technology (ADEPT) Enabling Advanced Entry, Descent, and Landing Capabilities for SmallSat Missions

The Adaptable, Deployable Entry and Placement Technology (ADEPT) is a mechanically deployable low-ballistic coefficient aeroshell entry system which performs entry, descent, and landing (EDL) functions for a broad range of planetary destinations including Mars, Venus, Titan and Earth. The deployable system allows mission planners to develop an aeroshell design that is stowed like a folded umbrella, and yet prior to the EDL mission segment, transforms into a deployed, near-rigid low ballistic coefficient configuration. The ADEPT architecture is scalable from a sub-1m class to 6m diameter entry vehicles for Venus and and it has been studied at up to 15m – 20m scale for human exploration class missions. There has been growing interest in performing interplanetary missions with small spacecraft as secondary payloads and ADEPT offers small satellite mission designers the ability to consider Aeroassist technologies to expand mission applications. The ADEPT architecture introduces a new approach for entry vehicle design. It deploys a flexible 3D woven carbon fabric as the primary drag surface. It is capable of surviving high aerothermal heating during entry, while maintaining a robust impermeable membrane that provides high drag for vehicle deceleration. The ADEPT project team has advanced this decelerator technology via systems-level testing at the one meter diameter (nano-ADEPT) scale. A subsonic aeroloads test (May 2015) and a pathfinder arc-jet aeroheating test (Sept 2015) and a successful sounding rocket flight (SR-1) launch of a 0.7 meter deployed diameter ADEPT (September 2018). The SR-1 flight experiment demonstrated most of the primary end-to-end mission stages including: launch in a stowed configuration, separation and deployment in zero-g, exo-atmospheric conditions, and passive ballistic re-entry of a 70 degree half-angle cone geometry. The ADEPT SR-1 sounding rocket flight experiment had to address challenges such as stowing within the constrained payload envelope, fabric folding, and packaging concerns.

Paul Wercinski↗
NASA NTRS2001

Relationship between early diastolic intraventricular pressure gradients, an index of elastic recoil, and improvements in systolic and diastolic function

BACKGROUND: Early diastolic intraventricular pressure gradients (IVPGs) have been proposed to relate to left ventricular (LV) elastic recoil and early ventricular "suction." Animal studies have demonstrated relationships between IVPGs and systolic and diastolic indices during acute ischemia. However, data on the effects of improvements in LV function in humans and the relationship to IVPGs are lacking. METHODS AND RESULTS: Eight patients undergoing CABG and/or infarct exclusion surgery had a triple-sensor high-fidelity catheter placed across the mitral valve intraoperatively for simultaneous recording of left atrial (LA), basal LV, and apical LV pressures. Hemodynamic data obtained before bypass were compared with those with similar LA pressures and heart rates obtained after bypass. From each LV waveform, the time constant of LV relaxation (tau), +dP/dt(max), and -dP/dt(max) were determined. Transesophageal echocardiography was used to determined end-diastolic (EDV) and end-systolic (ESV) volumes and ejection fractions (EF). At similar LA pressures and heart rates, IVPG increased after bypass (before bypass 1.64+/-0.79 mm Hg; after bypass 2.67+/-1.25 mm Hg; P<0.01). Significant improvements were observed in ESV, as well as in apical and basal +dP/dt(max), -dP/dt(max), and tau (each P<0.05). Overall, IVPGs correlated inversely with both ESV (IVPG=-0.027[ESV]+3.46, r=-0.64) and EDV (IVPG=-0.027[EDV]+4.30, r=-0.70). Improvements in IVPGs correlated with improvements in apical tau (Deltatau =5.93[DeltaIVPG]+4.76, r=0.91) and basal tau (Deltatau =2.41[DeltaIVPG]+5.13, r=-0.67). Relative changes in IVPGs correlated with changes in ESV (DeltaESV=-0.97[%DeltaIVPG]+23.34, r=-0.79), EDV (DeltaEDV=-1.16[%DeltaIVPG]+34.92, r=-0.84), and EF (DeltaEF=0.38[%DeltaIVPG]-8.39, r=0.85). CONCLUSIONS: Improvements in LV function also increase IVPGs. These changes in IVPGs, suggestive of increases in LV suction and elastic recoil, correlate directly with improvements in LV relaxation and ESV.

Non-NASA Center↗
NASA NTRS2015

Verification and Validation Testing of the Parachute Decelerator System Prior to the First Supersonic Flight Dynamics Test for the Low Density Supersonic Decelerator Program

The Parachute Decelerator System (PDS) is comprised of all components associated with the supersonic parachute and its associated deployment. During the Supersonic Flight Dynamics Test (SFDT), for the Low Density Supersonic Decelerators Program, the PDS was required to deploy the supersonic parachute in a defined fashion. The PDS hardware includes three major subsystems that must function together. The first subsystem is the Parachute Deployment Device (PDD), which acts as a modified pilot deployment system. It is comprised of a pyrotechnic mortar, a Kevlar ballute, a lanyard actuated pyrotechnic inflation aid, and rigging with its associated thermal protection material (TPS). The second subsystem is the supersonic parachute deployment hardware. This includes all of the parachute specific rigging that includes the parachute stowage can and the rigging including TPS and bridle stiffeners for bridle management during deployment. The third subsystem is the Supersonic Parachute itself, which includes the main parachute and deployment bags. This paper summarizes the verification and validation of the deployment process, from the initialization of the PDS system through parachute bag strip that was done prior to the first SFDT.

Gallon, John C.↗
DOE OSTI2025

Physics-Informed Neural Networks for PDE-Constrained Optimization and Control

The goal of optimal control is to determine a sequence of inputs for maximizing or minimizing a given performance criterion subject to the dynamics and constraints of the system under observation. This work introduces Control Physics-Informed Neural Networks (PINNs), which simultaneously learn both the system states and the optimal control signal in a single-stage framework that leverages the system’s underlying physical laws. While prior approaches often follow a two-stage process-modeling, the system first and then devising its control—the presented novel framework embeds the necessary optimality conditions directly into the network architecture and loss function. We demonstrate the effectiveness of the novel methodology by solving various open-loop optimal control problems governed by analytical, one-dimensional, and two-dimensional partial differential equations (PDEs).

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Emergent facilitation and glassy dynamics in supercooled liquids

In supercooled liquids, dynamical facilitation refers to a phenomenon where microscopic motion begets further motion nearby, resulting in spatially heterogeneous dynamics. This is central to the glassy relaxation dynamics of such liquids, which show super-Arrhenius growth of relaxation timescales with decreasing temperature. Despite the importance of dynamical facilitation, there is no theoretical understanding of how facilitation emerges and impacts relaxation dynamics. Here, we present a theory that explains the microscopic origins of dynamical facilitation. We show that dynamics proceeds by localized bond-exchange events, also known as excitations, resulting in the accumulation of elastic stresses with which new excitations can interact. At low temperatures, these elastic interactions dominate and facilitate the creation of new excitations near prior excitations. Using the theory of linear elasticity and Markov processes, we simulate a model, which reproduces multiple aspects of glassy dynamics observed in experiments and molecular simulations, including the stretched exponential decay of relaxation functions, the super-Arrhenius behavior of relaxation timescales as well as their two-dimensional finite-size effects. The model also predicts the subdiffusive behavior of the mean squared displacement (MSD) on short, intermediate timescales. Furthermore, we derive the phonon contributions to diffusion and relaxation, which when combined with the excitation contributions produce the two-step relaxation processes, and the ballistic–subdiffusive–diffusive crossover MSD behaviors commonly found in supercooled liquids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Creb5 controls its own expression and directly induces the joint interzone regulatory program

Prior studies have indicated that the transcription factor Creb5 is expressed in the joint interzone, which contains the progenitors for all synovial joint tissues in both mouse and human embryos. In the absence of Creb5 function, most synovial joint interzones fail to form and the cartilage templates in the long bones remain fused. This earlier work did not clarify whether Creb5 initiates a cascade of signaling molecules, such as growth and differentiation factor 5 (Gdf5) and Wnt-family members, that in turn induce the formation of the joint interzone, or instead directly activates the expression of joint interzone markers. In the present study, an integrative analysis of the transcriptome, chromatin accessibility, and Creb5-occupancy in joint progenitors revealed that Creb5 directly binds to both its own two promoters and to the regulatory regions of Gdf5 and Sfrp2, each of whose expression in the joint interzone is Creb5-dependent. Functional enhancer analysis indicated that Creb5 binding sites in either the two Creb5 promoters, or in Gdf5 and Sfrp2 regulatory elements are necessary for these sequences to drive transgene expression in the developing synovial joints. While Creb5 directly drives Gdf5 and Sfrp2 expression in the inner joint interzone, Creb5 activates Barx1 expression specifically in the outer joint interzone. Our findings indicate that Creb5 initiates a regulatory network that both promotes the formation of synovial joints, and subsequently activates distinct transcriptional targets in the inner versus the outer regions of the joint interzone, thus regionalizing gene expression in the developing joint.

Zhang, Cheng-Hai↗
DOE OSTI2020

Soft-Switching Solid-State Transformer With Reduced Conduction Loss

Solid-state transformers (SSTs) are a promising solution photovoltaic (PV), wind, traction, data center, battery energy storage system (BESS), and fast charging electric vehicle (EV) applications. The traditional SSTs are typically three-stage, i.e., hard-switching cascaded multilevel rectifiers and inverters with dual active bridge (DAB) converters, which leads to bulky passives, low efficiency, and high electromagnetic interference (EMI). This article proposes a new soft-switching solid-state transformer (S4T). The S4T has full-range zero-voltage switching (ZVS), electrolytic capacitor-less dc link, and controlled dv/dt, which reduces EMI. The S4T comprises two reverse-blocking current-source inverter (CSI) bridges, auxiliary branches for ZVS, and transformer magnetizing inductor as a reduced dc link with 60% ripple. Compared with the prior S4T, an effective change on the leakage inductance diode is made to reduce the number of the devices on the main power path by 20% for significant conduction loss saving and retain the same functionality of damping the resonance between the leakage and resonant capacitors and recycling trapped leakage energy. The conduction loss saving is crucial, being the dominating loss mechanism in SSTs. Importantly, the proposed single-stage SST not only holds the potential for high power density and high efficiency but also has full functionality, e.g., multiport dc loads integration, voltage regulation, and reactive power compensation, unlike the traditional single-stage matrix SST. The S4T can achieve single-stage isolated bidirectional dc–dc, ac–dc, dc–ac, or ac–ac conversion. It can also be configured input-series output-parallel (ISOP) in a modular way for medium-voltage (MV) grids. Hence, the S4T is a promising candidate for the SST. The full functionality, e.g., voltage buck–boost, multiport, etc., and the universality of the S4T for the dc–dc, dc–ac, and ac–ac conversion are verified through the simulations and experiments of two-port and three-port MV prototypes based on 3.3 kV SiC MOSFETs in dc–dc, dc–ac, and ac–ac modes at 2 kV.

14 SOLAR ENERGY↗
DOE OSTI2021

Global maximum carboxylation rate trait scaling in the Sheffield Dynamic Global Vegetation Model 1901-2012

This data package contains model output data and climate input data associated with the New Phytologist publication: Walker, A.P., Quaife, T., van Bodegom, P.M., De Kauwe, M.G., Keenan, T.F., Joiner, J., Lomas, M.R., MacBean, N., Xu, C., Yang, X., Woodward, F.I., 2017. The impact of alternative trait-scaling hypotheses for the maximum photosynthetic carboxylation rate (Vcmax) on global gross primary production. New Phytologist 215, 1370–1386. https://doi.org/10.1111/nph.14623. This dataset contains maximum carboxylation rate at 25 ºC (Vcmax,25), Gross Primary Production (GPP), Net Biome Production (NBP), vegetation carbon, and soil carbon data from Sheffield Dynamic Global Vegetation Model (SDGVM) for multiple trait-scaling methods for scaling Vcmax,25 across Earth, and alternative instantaneous temperature scaling functions. Vcmax,25 values are mean top-leaf values taken during the growing seasons, which were defined as periods during which leaf area index (LAI) was greater than one. Vcmax,25 values were reported prior to scaling of Vcmax by water-stress or leaf-age. The attached metadata file (SDGVM_vcmax_dataset.docx) describes the methods used and explains the organization of data within the included .zip file. This metadata file is also included in PDF format.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

DNA Methylation Patterns of Chronic Explosive Breaching in U.S. Military Warfighters

Background: Injuries from exposure to explosions rose dramatically during the Iraq and Afghanistan wars, which motivated investigation of blast-related neurotrauma. We have undertaken human studies involving military “breachers” —exposed to controlled, low-level blast during a 3-days explosive breaching course. Methods: We screened epigenetic profiles in peripheral blood samples from 59 subjects (in two separate U.S. Military training sessions) using Infinium MethylationEPIC BeadChips. Participants had varying numbers of exposures to blast over their military careers (empirically defined as high ≥ 40, and conversely, low < 39 breaching exposures). Daily self-reported physiological symptoms were recorded. Tinnitus, memory problems, headaches, and sleep disturbances are most frequently reported. Results: We identified 14 significantly differentially methylated regions (DMRs) within genes associated with cumulative blast exposure in participants with high relative to low cumulative blast exposure. Notably, NTSR1 and SPON1 were significantly differentially methylated in high relative to low blast exposed groups, suggesting that sleep dysregulation may be altered in response to chronic cumulative blast exposure. In comparing lifetime blast exposure at baseline (prior to exposure in current training), and top associated symptoms, we identified significant DMRs associated with tinnitus, sleep difficulties, and headache. Notably, we identified KCNN3, SOD3, MUC4, GALR1, and WDR45B, which are implicated in auditory function, as differentially methylated associated with self-reported tinnitus. These findings suggest neurobiological mechanisms behind auditory injuries in our military warfighters and are particularly relevant given tinnitus is not only a primary disability among veterans, but has also been demonstrated in active duty medical records for populations exposed to blast in training. Additionally, we found that differentially methylated regions associated with the genes CCDC68 and COMT track with sleep difficulties, and those within FMOD and TNXB track with pain and headache. Conclusion: Sleep disturbances, as well as tinnitus and chronic pain, are widely reported in U.S. military service members and veterans. As we have previously demonstrated, DNA methylation encapsulates lifetime exposure to blast. The current data support previous findings and recapitulate transcriptional regulatory alterations in genes involved in sleep, auditory function, and pain. These data uncovered novel epigenetic and transcriptional regulatory mechanism underlying the etiological basis of these symptoms.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1972

The measurement of driver describing functions in simulated steering control tasks

Measurements of driver describing functions in steering control tasks have been made using a driving simulator. The task was to regulate against a random crosswind gust input on a straight roadway, in order to stay in the center of the lane. Although driving is a multiloop task in general, the forcing function and situation were configured so that an inner-loop visual cue feedback of heading angle of heading rate would dominate, and the driver's response was interpreted to be primarily single-loop. The driver describing functions were measured using an STI describing function analyzer. Three replications for each subject showed good repeatability within a subject. There were some intersubject differences as expected, but the crossover frequencies, effective time delays, and stability margins were generally consistent with the prior data and models for similar manual control tasks. The results further confirm the feasibility of measuring human operator response properties in nominal control tasks with full (real-world) visual field displays.

Weir, D. H.↗
NASA NTRS1974

Mars - Clearing of the 1971 dust storm

A semiquantitative analysis of clearing in the 1971 great dust storm on Mars is presented as a function of time and altitude, using Mariner 9 orange- and visual-light photos. Steady settling of dust approximately accounts for the decline of the storm after Dec. 22, 1971. Continuous settling cannot be invoked prior to that date; injection of dust into the atmosphere, i.e., a storm resurgence, occurred in mid-December 1971. Theoretical models of optical depth vs time are developed for various distributions of particles in the atmosphere. By interpreting settling in terms of Stokes' law, estimates of the maximum radii of dust particles throughout the atmosphere have been obtained. Models which best account for the dust-storm decline indicate particles less than 5 microns in diameter high in the atmosphere, with a concentration of larger particles near the ground in the lowest parts of Mars.

Hartmann, W. K.↗
NASA NTRS1974

Spaceflight tracking and data network operational reliability assessment for Skylab

Data on the spaceflight communications equipment status during the Skylab mission were subjected to an operational reliability assessment. Reliability models were revised to reflect pertinent equipment changes accomplished prior to the beginning of the Skylab missions. Appropriate adjustments were made to fit the data to the models. The availabilities are based on the failure events resulting in the stations inability to support a function of functions and the MTBF's are based on all events including 'can support' and 'cannot support'. Data were received from eleven land-based stations and one ship.

Seneca, V. I.↗
NASA NTRS1975

Studies on possible propagation of microbial contamination in planetary atmospheres

Maintained aerosols were studied to demonstrate the metabolism and propagation of microbes in clouds which could occur in the course of a probe of a planetary atmosphere. Bacteriophage was used as a tool to test whether the mechanisms for DNA production remain intact and functional within the airborne bacterial cell. In one test method, bacteria were mixed with coliphage in an atomizer to allow attachment before aerosolization; in another, two suspensions were atomized saperately into a common air stream prior to aerosolization. Results show that biochemical and physiological mechanisms to allow aerobic microbes to propagate in the airborne state do exist.

Dimmick, R. L.↗
NASA NTRS1986

Application of physical parameter identification to finite element models

A time domain technique for matching response predictions of a structural dynamic model to test measurements is developed. Significance is attached to prior estimates of physical model parameters and to experimental data. The Bayesian estimation procedure allows confidence levels in predicted physical and modal parameters to be obtained. Structural optimization procedures are employed to minimize an error functional with physical model parameters describing the finite element model as design variables. The number of complete FEM analyses are reduced using approximation concepts, including the recently developed convoluted Taylor series approach. The error function is represented in closed form by converting free decay test data to a time series model using Prony' method. The technique is demonstrated on simulated response of a simple truss structure.

Bronowicki, Allen J.↗
NASA NTRS2002

Renal effects of fresh water-induced hypo-osmolality in a marine adapted seal

With few exceptions, marine mammals are not exposed to fresh water; however quantifying the endocrine and renal responses of a marine-adapted mammal to the infusion of fresh water could provide insight on the evolutionary adaptation of kidney function and on the renal capabilities of these mammals. Therefore, renal function and hormonal changes associated with fresh water-induced diuresis were examined in four, fasting northern elephant seal ( Mirounga angustirostris) (NES) pups. A series of plasma samples and 24-h urine voids were collected prior to (control) and after the infusion of water. Water infusion resulted in an osmotic diuresis associated with an increase in glomerular filtration rate (GFR), but not an increase in free water clearance. The increase in excreted urea accounted for 96% of the increase in osmotic excretion. Following infusion of fresh water, plasma osmolality and renin activity decreased, while plasma aldosterone increased. Although primary regulators of aldosterone release (Na(+), K(+) and angiotensin II) were not significantly altered in the appropriate directions to individually stimulate aldosterone secretion, increased aldosterone may have resulted from multiple, non-significant changes acting in concert. Aldosterone release may also be hypersensitive to slight reductions in plasma Na(+), which may be an adaptive mechanism in a species not known to drink seawater. Excreted aldosterone and urea were correlated suggesting aldosterone may regulate urea excretion during hypo-osmotic conditions in NES pups. Urea excretion appears to be a significant mechanism by which NES pups sustain electrolyte resorption during conditions that can negatively affect ionic homeostasis such as prolonged fasting.

NASA Center ARC↗
NASA NTRS2004

Improved Estimate of Phobos Secular Acceleration from MOLA Observations

We report on new observations of the orbital position of Phobos, and use them to obtain a new and improved estimate of the rate of secular acceleration in longitude due to tidal dissipation within Mars. Phobos is the inner-most natural satellite of Mars, and one of the few natural satellites in the solar system with orbital period shorter than the rotation period of its primary. As a result, any departure from a perfect elastic response by Mars in the tides raised on it by Phobos will cause a transfer of angular momentum from the orbit of Phobos to the spin of Mars. Since its discovery in 1877, Phobos has completed over 145,500 orbits, and has one of the best studied orbits in the solar system, with over 6000 earth-based astrometric observations, and over 300 spacecraft observations. As early as 1945, Sharpless noted that there is a secular acceleration in mean longitude, with rate (1.88 + 0.25) 10(exp -3) degrees per square year. In preparation for the 1989 Russian spacecraft mission to Phobos, considerable work was done compiling past observations, and refining the orbital model. All of the published estimates from that era are in good agreement. A typical solution (Jacobson et al., 1989) yields (1.249 + 0.018) 10(exp -3) degrees per square year. The MOLA instrument on MGS is a laser altimeter, and was designed to measure the topography of Mars. However, it has also been used to make observations of the position of Phobos. In 1998, a direct range measurement was made, which indicated that Phobos was slightly ahead of the predicted position. The MOLA detector views the surface of Mars in a narrow field of view, at 1064 nanometer wavelength, and can detect shadows cast by Phobos on the surface of Mars. We have found 15 such serendipitous shadow transit events over the interval from xx to xx, and all of them show Phobos to be ahead of schedule, and getting progressively farther ahead of the predicted position. In contrast, the cross-track positions are quite close to the predicted values. Assuming that the along-track discrepancy is small enough that we can linearize the corrections, we model the mean orbital longitude as a quadratic function of time, and solve for corrections to the constant, linear, and quadratic terms. The time span of the recent observations is insufficient to properly resolve this issue alone, but when the 127 years of prior observations are added, we find a solution which reduces misfit to the new observations considerably, and makes no significant change to the fit to earlier observations. Our estimate for the secular acceleration term is (1.367 + 0.006) degrees per square year. The corresponding rate of energy dissipation is 3.34 MW. From a geophysical perspective, a more interesting parameter than the secular acceleration itself is the tidal lag angle, or tidal quality factor Q, for Mars. Unfortunately, the limiting error source in that determination is remaining uncertainty in the tidal Love numbers at harmonic degrees 2,3, and even 4. Until those parameters are better constrained, improvement in the orbital model of Phobos will not provide corresponding benefits for understanding the interior of Mars.

Bills, Bruce↗
NASA NTRS2008

Update on Development of SiC Multi-Chip Power Modules

Progress has been made in a continuing effort to develop multi-chip power modules (SiC MCPMs). This effort at an earlier stage was reported in 'SiC Multi-Chip Power Modules as Power-System Building Blocks' (LEW-18008-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 28. The following recapitulation of information from the cited prior article is prerequisite to a meaningful summary of the progress made since then: 1) SiC MCPMs are, more specifically, electronic power-supply modules containing multiple silicon carbide power integrated-circuit chips and silicon-on-insulator (SOI) control integrated-circuit chips. SiC MCPMs are being developed as building blocks of advanced expandable, reconfigurable, fault-tolerant power-supply systems. Exploiting the ability of SiC semiconductor devices to operate at temperatures, breakdown voltages, and current densities significantly greater than those of conventional Si devices, the designs of SiC MCPMs and of systems comprising multiple SiC MCPMs are expected to afford a greater degree of miniaturization through stacking of modules with reduced requirements for heat sinking; 2) The stacked SiC MCPMs in a given system can be electrically connected in series, parallel, or a series/parallel combination to increase the overall power-handling capability of the system. In addition to power connections, the modules have communication connections. The SOI controllers in the modules communicate with each other as nodes of a decentralized control network, in which no single controller exerts overall command of the system. Control functions effected via the network include synchronization of switching of power devices and rapid reconfiguration of power connections to enable the power system to continue to supply power to a load in the event of failure of one of the modules; and, 3) In addition to serving as building blocks of reliable power-supply systems, SiC MCPMs could be augmented with external control circuitry to make them perform additional power-handling functions as needed for specific applications. Because identical SiC MCPM building blocks could be utilized in such a variety of ways, the cost and difficulty of designing new, highly reliable power systems would be reduced considerably. This concludes the information from the cited prior article. The main activity since the previously reported stage of development was the design, fabrication, and testing a 120- VDC-to-28-VDC modular power-converter system composed of eight SiC MCPMs in a 4 (parallel)-by-2 (series) matrix configuration, with normally-off controllable power switches. The SiC MCPM power modules include closed-loop control subsystems and are capable of operating at high power density or high temperature. The system was tested under various configurations, load conditions, load-transient conditions, and failure-recovery conditions. Planned future work includes refinement of the demonstrated modular system concept and development of a new converter hardware topology that would enable sharing of currents without the need for communication among modules. Toward these ends, it is also planned to develop a new converter control algorithm that would provide for improved sharing of current and power under all conditions, and to implement advanced packaging concepts that would enable operation at higher power density.

Lostetter, Alexander↗