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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Stellar Mass Black Hole Formation and Multimessenger Signals from Three-dimensional Rotating Core-collapse Supernova Simulations

We present self-consistent 3D core-collapse supernova simulations of a 40 ${M}_{\odot }$ progenitor model using the isotropic diffusion source approximation for neutrino transport and an effective general relativistic potential up to `0.9 s postbounce. We consider three different rotational speeds with initial angular velocities of ${{\rm{\Omega }}}_{0}=0$, 0.5, and 1 rad s -1 and investigate the impact of rotation on shock dynamics, black hole (BH) formation, and gravitational wave (GW) signals. The rapidly rotating model undergoes an early explosion at ~250 ms postbounce and shows signs of the low $T/| W| $ instability. We do not find BH formation in this model within ~460 ms postbounce. In contrast, we find BH formation at 776 ms postbounce and 936 ms postbounce for the nonrotating and slowly rotating models, respectively. The slowly rotating model explodes at ~650 ms postbounce, and the subsequent fallback accretion onto the proto–neutron star (PNS) results in BH formation. In addition, the standing accretion shock instability induces rotation of the PNS in the model that started with a nonrotating progenitor. Assuming conservation of specific angular momentum during BH formation, this corresponds to a BH spin parameter of a = J/M = 0.046. However, if no explosion sets in, all the angular momentum will eventually be accreted by the BH, resulting in a nonspinning BH. The successful explosion of the slowly rotating model drastically slows down the accretion onto the PNS, allowing continued cooling and contraction that results in an extremely high GW frequency (f ~ 3000 Hz) at BH formation, while the nonrotating model generates GW signals similar to our corresponding 2D simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Global Kinetic Modeling of the Intrabinary Shock in Spider Pulsars

Abstract Spider pulsars are compact binary systems composed of a millisecond pulsar and a low-mass companion. The relativistic magnetically dominated pulsar wind impacts onto the companion, ablating it and slowly consuming its atmosphere. The interaction forms an intrabinary shock, a proposed site of particle acceleration. We perform global fully kinetic particle-in-cell simulations of the intrabinary shock, assuming that the pulsar wind consists of plane-parallel stripes of alternating polarity and that the shock wraps around the companion. We find that particles are efficiently accelerated via shock-driven reconnection. We extract first-principles synchrotron spectra and light curves, which are in good agreement with X-ray observations: (1) the synchrotron spectrum is nearly flat, F ν ∝ const; (2) when the pulsar spin axis is nearly aligned with the orbital angular momentum, the light curve displays two peaks, just before and after the pulsar eclipse (pulsar superior conjunction), separated in phase by ∼0.8 rad; (3) the peak flux exceeds the one at the inferior conjunction by a factor of 10.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The Synchrotron Low-energy Spectrum Arising from the Cooling of Electrons in Gamma-Ray Bursts

This work is a continuation of a previous effort (Panaitescu) to study the cooling of relativistic electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses, with application to the spectra and light curves of the synchrotron gamma-ray burst (GRB) produced by such cooling electrons. Here, we derive the low-energy slope β LE of a GRB pulse-integrated spectrum and quantify the implications of the measured distribution of β LE . Radiative processes that produce soft integrated spectra can accommodate the harder slopes measured by CGRO/BATSE and Fermi/GBM only if the magnetic field lifetime t B is shorter than the time during which the typical GRB electrons cool to radiate below 1–10 keV, which is less than (at most) 10 radiative cooling timescales t rad of the typical GRB electron. In this case, there is a one-to-one correspondence between t B and β LE . To account for low-energy slopes β LE > -3/4, the adiabatic electron-cooling requires a similar restriction on t B . In this case, the diversity of slopes arises mostly from how the electron-injection rate varies with time (temporal power-law injection rates yield power-law low-energy GRB spectra) and not from the magnetic field timescale.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Effect of Rotation on Wave Mixing in Intermediate-mass Stars

Internal gravity waves are likely to cause mixing in stellar interiors. Studies show that the mixing by these waves changes drastically across age and mass. Here, we study the effect of rotation on this wave mixing by considering a 7 M ⊙ model at zero-age main sequence and mid-main sequence. We compare the mixing profiles at a range of rotation rates (1 × 10 -5 , 2 × 10 -5 , 3 × 10 -5 , 4 × 10 -5 , and 1 × 10 -4 rad s -1 ) and observe that the mixing decreases with decreasing Rossby number. This can be attributed to the effect of rotation on convection, which influences the amplitude with which the waves are excited near the convective–radiative interface.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

The Effect of Inverse Compton Losses on Particle Acceleration in Three-dimensional Relativistic Reconnection

Relativistic magnetic reconnection is a key mechanism for dissipating magnetic energy and accelerating particles in astrophysics. In the absence of radiative cooling, recent particle-in-cell (PIC) simulations have shown that high-energy particles gain most of their energy in the upstream region, during a short-lived “free phase” where they meander between the two sides of the layer; when they get captured/trapped by the downstream flux ropes, they undergo a “trapped phase,” where no significant energization occurs. Here, we perform a suite of 3D PIC simulations of relativistic reconnection, including inverse Compton (IC) losses in the weakly cooled regime in which the radiation-reaction-limited Lorentz factor γrad exceeds the magnetization σ. We show that electron cooling losses do not appreciably alter the reconnection rate, the structure of the layer, and the physics of particle acceleration in the free phase, so the spectrum of free electrons is dN free /dγ ∝ γ −1 , as in the uncooled case. The spectrum of trapped electrons above the cooling break γcool (in the range γ cool < γ < γ rad ) is dN/dγ ∝ γ −3 , steeper than the scaling dN/dγ ∝ γ −2 of uncooled simulations. This confirms that no significant particle energization occurs during the trapped phase. Our results validate the model by Zhang et al. for particle acceleration in 3D relativistic reconnection, and imply that radiative emission models of reconnection-powered astrophysical sources should employ a two-zone structure that differentiates between free, rapidly accelerating particles and trapped, passively cooling particles.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

ON THE AFTERGLOW AND PROGENITOR OF FRB 150418

Keane et al. recently detected a fading radio source following FRB 150418, leading to the identification of a putative host galaxy at z = 0.492 ± 0.008. Assuming that the fading source is the afterglow of FRB 150418, I model the afterglow and constrain the isotropic energy of the explosion to be a few 10{sup 50} erg, comparable to that of a short-duration gamma-ray burst (GRB). The outflow may have a jet opening angle of ∼0.22 rad, so that the beaming-corrected energy is below 10{sup 49} erg. The results rule out most fast radio burst (FRB) progenitor models for this FRB, but may be consistent with either of the following two scenarios. The first scenario invokes a merger of an NS–NS binary, which produced an undetected short GRB and a supra-massive neutron star, which subsequently collapsed into a black hole, probably hundreds of seconds after the short GRB. The second scenario invokes a merger of a compact star binary (BH–BH, NS–NS, or BH–NS) system whose pre-merger dynamical magnetospheric activities made the FRB, which is followed by an undetected short GRB-like transient. The gravitational-wave (GW) event GW 150914 would be a sister of FRB 150418 in this second scenario. In both cases, one expects an exciting prospect of GW/FRB/GRB associations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Energy Release in the Solar Atmosphere from a Stream of Infalling Prominence Debris

Recent high-resolution and high-cadence extreme-ultraviolet (EUV) imaging has revealed a new phenomenon, impacting prominence debris, where prominence material from failed or partial eruptions can impact the lower atmosphere, releasing energy. We report a clear example of energy release and EUV brightening due to infalling prominence debris that occurred on 2011 September 7–8. The initial eruption of material was associated with an X1.8-class flare from AR 11283, occurring at 22:30 UT on 2011 September 7. Subsequently, a semicontinuous stream of this material returned to the solar surface with a velocity v > 150 km s{sup −1}, impacting a region remote from the original active region between 00:20 and 00:40 UT on 2011 September 8. Using the Solar Dynamics Observatory/Atmospheric Imaging Assembly, the differential emission measure of the plasma was estimated throughout this brightening event. We found that the radiated energy of the impacted plasma was L{sub rad}∼10{sup 27} erg, while the thermal energy peaked at ∼10{sup 28} erg. From this we were able to determine the mass content of the debris to be in the range 2×10{sup 14}<m<2×10{sup 15} g. Given typical prominence masses, the likely debris mass is toward the lower end of this range. This clear example of a prominence debris event shows that significant energy release takes place during these events and that such impacts may be used as a novel diagnostic tool for investigating prominence material properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

A Dense Plasma Globule in the Solar Neighborhood

The radio source J1819+3845 underwent a period of extreme interstellar scintillation between circa 1999 and 2007. The plasma structure responsible for this scintillation was determined to be just 1–3 pc from the solar system and to posses a density of n{sub e}∼10{sup 2} cm{sup −3}, which is three orders of magnitude higher than the ambient interstellar density. Here we present radio-polarimetric images of the field toward J1819+3845 at wavelengths of 0.2, 0.92, and 2 m. We detect an elliptical plasma globule of approximate size 1{sup ∘}×≳2{sup ∘} (major-axis position angle of ≈−40{sup ∘}), via its Faraday-rotation imprint (≈15 rad m{sup −2}) on the diffuse Galactic synchrotron emission. The extreme scintillation of J1819+3845 was most likely caused at the turbulent boundary of the globule (J1819+3845 is currently occulted by the globule). The origin and precise nature of the globule remain unknown. Our observations represent the first time that plasma structures which likely cause extreme scintillation have been directly imaged.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Third generation residual gas ionization profile monitors at Fermilab

The latest generation of IPMs installed in the Fermilab Main Injector and Recycler incorporate a 1 kG permanent magnet, a newly designed high-gain, rad-tolerant preamp, and a control grid to moderate the charge that is allowed to arrive on the anode pick-up strips. The control grid is intended to select a single Booster batch measurement per turn. Initially it is being used to allow for a faster turn-on of a single, high-intensity cycle in either machine. The expectation is that this will extend the Micro Channel Plate lifetime, which is the high-cost consumable in the measurement system. We discuss the new design and data acquired with this system.

Zagel, J. R.↗
DOE OSTI2026

BNF C-band Scanning ARM Precipitation Radar 2nd Generation (CSAPR-2) Extracted Radar Columns and In-Situ Sensors (RadCLss)

Corrected Moments in Antenna Coordinates (CMAC) calculates quantitative precipitation estimates (QPE) from empirical relationships based on equivalent radar reflectivity factor, specific differ- ential phase, and specific attenuation. To evaluate these empirical relationships, the Extracted Radar Columns and In-Situ Sensors (RADclss) product was developed. Utilizing Py-ART, RAD- clss extracts CMAC radar columns above various ARM and partner locations. These columns are then spatiotemporally synced with in-situ observations at the surface utilizing the Atmospheric data Community Toolkit (ACT; Theisen et al. 2025), allowing direct comparison of radar parameters with rain gauges and laser disdrometers for further investigation.

bankhead↗
DOE OSTI2026

Wind and Temperature Consensus at Horn Point, HU-Beltsville, Piney Run (Maryland) in support of CoURAGE

The Maryland Department of the Environment (MDE) operates a ground-based atmospheric profiling network consisting of collocated radar wind profilers (RWP) and radio acoustic sounding systems (RASS) as part of its Ambient Air Monitoring Program. This network provides continuous observations of wind and temperature structure in the lower troposphere to support air quality forecasting, regulatory analysis, and atmospheric research. The network currently includes three fixed sites across Maryland: Horn Point (HP, lower eastern shore) [38.587525°,-76.141006°], Howard University-Beltsville (HUB, central Maryland) [39.055277°, -76.878632°], and Piney Run (PR, western Maryland) [39.705950°, -79.012000°] The network is designed to capture regional variability in atmospheric transport and boundary-layer processes. These systems measure vertical profiles of horizontal wind speed and direction using Doppler radar techniques, with observations typically spanning from ~100 m above ground level up to approximately 2.5–4 km. Measurements are derived from the Doppler shift of backscattered electromagnetic signals, enabling retrieval of wind vectors at multiple altitudes with high temporal resolution (e.g., 30-minute averages reported every 6 minutes). Each radar wind profiler is paired with a Radio Acoustic Sounding System (RASS) to provide profiles of virtual temperature in the lower atmosphere (~100–200 m AGL) by measuring the propagation speed of acoustic waves. Together, the RWP/RASS system yields a coupled data set of thermodynamic and kinematic atmospheric structure, including additional parameters such as vertical velocity, radial velocity, signal-to-noise ratio, and spectral width for advanced analysis. There are two types of files for each station: wind data (files with a "w" prefix) and virtual temperature RASS data (files with a "t" prefix). The wind data files are in the format wYYDDD.cns, where YY is the 2-digit year and DDD is the day of the year. The RASS virtual temperature data files are in the format tYYDDD.cns. Each record has the following header structure: Line 1 : Station Name RASS files Line 2 : RASS rev DeTect_2.0, WINDS files Line 2 : WINDS rev ATI 5.1 Line 3 : N latitude, W longitude, and site elevation (m) Line 4 : Date and begin time of consensus: yy mm dd hh mn ss plus # minutes to add to get UTC Line 5 : Consensus averaging time (minutes); number of beams; number of range gates Line 6 : Number of records required to make consensus (num) total number of records (tot) and the consensus window size (m/s) in the format: num:tot (window) RASS files Line 7 : no. of coded cells, no. of spec, pulse width (ns), and inter-pulse period (µs), WINDS files Line 7 : No. of coded cells, no. of spectra, pulse width (ns), and inter-pulse period (µs), each with a pair of values: first value is for oblique beams, second for vertical RASS files Line 8 : Full scale Doppler value (m/s) Delay to first gate (ns) Number of gates Spacing of gates (ns), WINDS files Line 8 : Full scale Doppler velocity (m/s), oblique and vertical Vertical correction applied to oblique beams? (0 = no, 1 = yes) Delay to first gate (ns), oblique and vertical Number of gates, oblique and vertical Spacing of gates (ns), oblique and vertical Line 9 : Azimuth and elevation (9s indicate vertical beam not used) RASS files Line 10, values : HT = Height above ground (km), T = Uncorrected virtual temperature consensus (deg C), Tc = Corrected virtual temperature consensus (deg C), W = Vertical wind consensus (9s indicate vertical beam not used, w-component, positive upward, m/s), CNT = Number of records that made consensus (for the 3 values in same order), SNR = Average signal to noise ratio (dB) of records in consensus (same order) WINDS files Line 10, values : HT = Height above ground (km), SPD = Wind speed (m/s), DIR = Wind direction (deg E of N from N), RAD = Radial velocities for each beam (m/s) in order given in azimuth and elevation line (positive toward radar; 9s indicate vertical beam not used, CNT = Number of records that made consensus, SNR = Average signal to noise ratio (dB) of records in consensus

{"wind speed and direction",temperature}↗
NASA NTRS1962

LUBRICATING PROPERTIES OF CERAMIC-BONDED CALCIUM FLUORIDE COATINGS ON NICKEL-BASE ALLOYS FROM 75 DEG TO 1900 DEG F

The endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75° to 1900° F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500° F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500° F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500° F, but at 1600° F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for René 41 sliding against coated René 41 at temperatures up to 1900° F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals . Friction coefficients were 0.12 at 1500° F, 0.15 at 1700° F, and 0.17 at 1800° and 1900° F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500° F. René 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (<0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted i n a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.

Nickel alloy↗
NASA NTRS1961

Effects of Ionizing Radiation on Solid Rocket Motor Components

Problems which the solid propellant rocket engineer will encounter in designing for long-term storage in a radiation environment are discussed. A summary of present knowledge of the radiation environment is given. Mechanisms of radiation degradation and its effects on tensile properties of propellant binders are discussed qualitatively. Data from a program of irradiation of several propellants is presented. Properties of two of the propellants were changed significantly by doses of the order of 4 x 10(exp 6) rads.

RADIATION↗
NASA NTRS1962

ELASTIC INSTABILITY OF CONICAL SHELLS UNDER COMBINED LOADING

1. Criteria are presented for the elastic instability of thin single and multilayer conical and cylindrical shells under combined axial load and external pressure. These criteria, used in design analysis, are based on theoretical results and the correlation of these results with readily available experimental data. 2. A summary is included of the studies at Avco RAD of shells under static or dynamic loads.

ELASTIC SHELL↗
NASA NTRS1965

The Importance of Space Radiation Shielding Weight

The shielding weights required to protect astronauts against space radiation should be considered in relation to the weights of the meteoroid shielding and the life support systems. Comparisons have been carried out for a variety of crew sizes and mission durations. The radiation shield weights were based upon a 1percent probability and were obtained from Webber's data on solar proton events. A mission dose of 100 rad was used as the allowed limit. The doses allowed from solar events were reduced by 45 mrad/day due to galactic radiation and by the amount of radiation expected for two high thrust trips through the earth's trapped radiation belts. In the calculation of the shield weights, the "storm cellar" concept was employed, allotting 50 ft a per man. The meteoroid shield weights were based upon the work of Bjork and the NASA-Ames Research Center criterion. The single shield thicknesses calculated were modified to take into account the reduced penetration where two facing sheets with space between them are used as the meteoroid shield. A percent probability of penetration was assumed in the calculations. The weights of the life support system are dependent upon the assumptions made regarding the particular subsystems to use for a specific mission. Two systems were used for this comparison. The system selected for the 30-day mission provides for body waste storage rather than reprocessing. Each system assumes a cabin leakage rate of 10 Ibs/day and a power penalty weight of 320 lbs/kWe.

SPACE RADIATION↗
NASA NTRS1972

Hardening electronic devices against very high total dose radiation environments

The possibilities and limitations of hardening silicon semiconductor devices to the high neutron and gamma radiation levels and greater than 10 to the eighth power rads required for the NERVA nuclear engine development are discussed. A comparison is made of the high dose neutron and gamma hardening potential of bipolar, metal insulator semiconductors and junction field effect transistors. Experimental data is presented on device degradation for the high neutron and gamma doses. Previous data and comparisons indicate that the JFET is much more immune to the combined neutron displacement and gamma ionizing effects than other transistor types. Experimental evidence is also presented which indicates that p channel MOS devices may be able to meet the requirements.

Buchanan, B.↗
NASA NTRS1972

Proton irradiation of stem cells: Radiation damage and chemical radioprotection

Effects of high energy protons on erythropoietic stem cells and radioprotection by chemicals were investigated in NASA Space Radiation Effects Laboratory. The effects of a parallel beam of 600 MeV protons. The fluence, when converted to dose, were referenced to the synchrocyclotron beam monitors which were then used to administer radiation exposures. Mice were given graded doses to 300 rads to determine dose-response curve. Other mice received saline, AET, or 5-hydroxytryptamine 10 to 15 minutes before exposure.

Riley, R. C.↗
NASA NTRS1972

Dose and linear energy transfer spectral measurements for the supersonic transport program

The purpose of the package, called the high altitude radiation instrumentation system (HARIS), is to measure the radiation hazard to supersonic transport passengers from solar and galactic cosmic rays. The HARIS includes gaseous linear energy transfer spectrometer, a tissue equivalent ionization chamber, and a geiger meuller tube. The HARIS is flown on RB-57F aircraft at 60,000 feet. Data from the HARIS are reduced to give rad and rem dose rates measured by the package during the flights. Results presented include ambient data obtained on background flights, altitude comparison data, and solar flare data.

Philbrick, R. B.↗