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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

NASA's Research in Aircraft Vulnerability Mitigation

Since its inception in 1958, the National Aeronautics and Space Administration s (NASA) role in civil aeronautics has been to develop high-risk, high-payoff technologies to meet critical national aviation challenges. Following the events of Sept. 11, 2001, NASA recognized that it now shared the responsibility for improving homeland security. The NASA Strategic Plan was modified to include requirements to enable a more secure air transportation system by investing in technologies and collaborating with other agencies, industry, and academia. NASA is conducting research to develop and advance innovative and commercially viable technologies that will reduce the vulnerability of aircraft to threats or hostile actions, and identify and inform users of potential vulnerabilities in a timely manner. Presented in this paper are research plans and preliminary status for mitigating the effects of damage due to direct attacks on civil transport aircraft. The NASA approach to mitigation includes: preventing loss of an aircraft due to a hit from man-portable air defense systems; developing fuel system technologies that prevent or minimize in-flight vulnerability to small arms or other projectiles; providing protection from electromagnetic energy attacks by detecting directed energy threats to aircraft and on/off-board systems; and minimizing the damage due to high-energy attacks (explosions and fire) by developing advanced lightweight, damage-resistant composites and structural concepts. An approach to preventing aircraft from being used as weapons of mass destruction will also be discussed.

Allen, Cheryl L.↗
NASA NTRS2008

Gamma Ray Burst Discoveries with the Swift Mission

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z greater than 5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gehrels, Neil↗
NASA NTRS2008

Gamma Ray Burst Discoveries with the Swift Mission

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from - 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type I1 and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gehrels, Neil↗
NASA NTRS2009

Gamma Ray Burst Discoveries with the Swift Mission

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 4 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.7 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gehrels, Neil↗
NASA NTRS2009

Gamma Ray Bursts and the Birth of Black Holes

Black holes have been predicted since the 1940's from solutions of Einstein's general relativity field equation. There is strong evidence of their existence from astronomical observations, but their origin has remained an open question of great interest. Gamma-ray bursts may the clue. They are powerful explosions, visible to high redshift, and appear to be the birth cries of black holes. The Swift and Fermi missions are two powerful NASA observatories currently in orbit that are discovering how gamma-ray bursts work. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are tremendously luminous and are providing a new tool to study the high redshift universe. One Swift burst at z=8.3 is the most distant object known in the universe. The talk will present the latest gamma-ray burst results from Swift and Fermi and will highlight what they are teaching us about black holes and jet outflows.

Gehrels, Neil↗
NASA NTRS2012

Recent Progress on GRBs with Swift

Gamma-ray bursts (GRBs) are powerful explosions, visible to high red shift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from ~ 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type. II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>S and one at z=9.4 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy .

Gehrels, Neil↗
NASA NTRS2013

Hydrocarbon-Seeded Ignition System for Small Spacecraft Thrusters Using Ionic Liquid Propellants

"Green" propellants based on Ionic-liquids (ILs) like Ammonium DiNitramide and Hydroxyl Ammonium Nitrate have recently been developed as reduced-hazard replacements for hydrazine. Compared to hydrazine, ILs offer up to a 50% improvement in available density-specific impulse. These materials present minimal vapor hazard at room temperature, and this property makes IL's potentially advantageous for "ride-share" launch opportunities where hazards introduced by hydrazine servicing are cost-prohibitive. Even though ILs present a reduced hazard compared to hydrazine, in crystalline form they are potentially explosive and are mixed in aqueous solutions to buffer against explosion. Unfortunately, the high water content makes IL-propellants difficult to ignite and currently a reliable "coldstart" capability does not exist. For reliable ignition, IL-propellants catalyst beds must be pre-heated to greater than 350 C before firing. The required preheat power source is substantial and presents a significant disadvantage for SmallSats where power budgets are extremely limited. Design and development of a "micro-hybrid" igniter designed to act as a "drop-in" replacement for existing IL catalyst beds is presented. The design requires significantly lower input energy and offers a smaller overall form factor. Unlike single-use "squib" pyrotechnic igniters, the system allows the gas generation cycle to be terminated and reinitiated on demand.

Whitmore, Stephen A.↗
NASA NTRS2013

Gamma Ray Bursts in the Swift-Fermi Era

Gamma-ray bursts (GRBs) are among the most violent occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole birth. They are highly luminous events and provide excellent probes of the distant universe. GRB research has greatly advanced over the past 10 years with the results from Swift, Fermi and an active follow-up community. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

fermi↗
NASA NTRS2014

The Rise and Fall of the Type Ib Supernova iPTF13bvn Not a Massive Wolf-Rayet Star

Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progenitor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly classify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario. Methods. We present a large set of observational data, consisting of multi-band light curves (UBVRI, g′r′i′z′) and optical spectra. We perform standard spectral line analysis to track the evolution of the SN ejecta. We also construct a bolometric light curve and perform hydrodynamical calculations to model this light curve to constrain the synthesized radioactive nickel mass and the total ejecta mass of the SN. Late-time photometry is analyzed to constrain the amount of oxygen. Furthermore, image registration of pre- and post-explosion HST images is performed. Results. Our HST astrometry confirms the location of the progenitor candidate of iPTF13bvn, and follow-up spectra securely classify this as a SN Ib. We use our hydrodynamical model to fit the observed bolometric light curve, estimating the total ejecta mass to be 1.9 solar mass and the radioactive nickel mass to be 0.05 solar mass. The model fit requires the nickel synthesized in the explosion to be highly mixed out in the ejecta. We also find that the late-time nebular r′-band luminosity is not consistent with predictions based on the expected oxygen nucleosynthesis in very massive stars. Conclusions. We find that our bolometric light curve of iPTF13bvn is not consistent with the previously proposed single massive WR-star progenitor scenario. The total ejecta mass and, in particular, the late-time oxygen emission are both significantly lower than what would be expected from a single WR progenitor with a main-sequence mass of at least 30 solar mass.

massive↗
NASA NTRS1992

Transient/structural analysis of a combustor under explosive loads

The 8-Foot High Temperature Tunnel (HTT) at NASA Langley Research Center is a combustion-driven blow-down wind tunnel. A major potential failure mode that was considered during the combustor redesign was the possibility of a deflagration and/or detonation in the combustor. If a main burner flame-out were to occur, then unburned fuel gases could accumulate and, if reignited, an explosion could occur. An analysis has been performed to determine the safe operating limits of the combustor under transient explosive loads. The failure criteria was defined and the failure mechanisms were determined for both peak pressures and differential pressure loadings. An overview of the gas dynamics analysis was given. A finite element model was constructed to evaluate 13 transient load cases. The sensitivity of the structure to the frequency content of the transient loading was assessed. In addition, two closed form dynamic analyses were conducted to verify the finite element analysis. It was determined that the differential pressure load or thrust load was the critical load mechanism and that the nozzle is the weak link in the combustor system.

Gregory, Peyton B.↗
NASA NTRS2014

Asymmetries in Core-Collapse Supernovae from Maps of Radioactiver 44Ti in Cassiopeia A

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive 44Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surroundingmedium1, directly probes the explosion asymmetries. Cassiopeia A is a young2, nearby3, core-collapse4 remnant from which 44Ti emission has previously been detected5-8 but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed 44Ti emission to estimated 56Ni emission9, from optical light echoes10, and from jet-like features seen in the X-ray11 and optical12 ejecta. Here we report spatial maps and spectral properties of the 44Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the 44Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae.

stellarcore-collapse explosions↗
NASA NTRS2014

The Rise of SN 2014J in the Nearby Galaxy M 82

We report on the discovery of SN 2014J in the nearby galaxy M 82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova over a wide range of the electromagnetic spectrum. Optical, near-IR and mid-IR observations on the rising lightcurve, orchestrated by the intermediate Palomar Transient Factory (iPTF), show that SN 2014J is a spectroscopically normal Type Ia supernova, albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the lightcurve rise. Similarly to other highly reddened Type Ia supernovae, a low value of total-to-selective extinction, R (sub V) less than or approximately equal to 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from HST with special emphasis on the sources nearest to the SN location.

galaxy↗
DOE OSTI2025

Permeability scaling relationships of volcanic tuff from core to field scale measurements

A recent chemical explosive test in P-Tunnel at the Nevada National Security Site, Nevada, USA, was conducted to better understand how signals propagate from explosions in the subsurface. A primary signal of interest is the migration of gases that can be used to differentiate chemical from nuclear explosions. Gas migration is highly dependent on the rock permeability which is notoriously difficult to determine experimentally in the field due to a potentially large dependence on the scale over which measurements are made. Here, we present pre-explosion permeability estimates to characterize the geologic units surrounding the recent test. Permeability measurements were made at three scales of increasing size: core samples (≈2 cm), borehole packer system tests (≈1 m), and a pre-shot cavity pressurization test (> 10 m) across ten tuff units. Permeability estimates based on core measurements showed little difference from borehole packer tests. However, permeability in most rock units calibrated from cavity pressurization tests resulted in higher permeability estimates by up to two orders of magnitude. Here, we demonstrate that the scale of the measurement significantly impacts the characterization efforts of hydraulic properties in volcanic tuff, and that local-scale measurements (< 10 m scale) do not incorporate enough heterogeneity to accurately predict field-scale flow and mass transport.

Environmental sciences↗
NASA NTRS1977

Supernovae, grains and the formation of the solar system

An investigation is conducted concerning the possibility that observed Mg-26 anomalies in meteorites may be related to a nucleosynthetic event which preceded the formation of the solar system by at most a few million years. The Al-26, which decayed to form the observed excess Mg-26, could have been produced in either explosive carbon burning or in a high temperature carbon burning shell source immediately preceding the explosion. The results of supernova grain condensation calculations are presented and related to the hypothesis that a 'last event' supernova was indeed related to the formation of the solar system and thus might have created the observed isotopic anomalies in magnesium, oxygen, neon, and xenon.

Lattimer, J. M.↗
NASA NTRS1973

Photographic laboratory studies of explosions.

Description of a series of cinematographic studies of explosions made with a high-speed rotating-mirror streak camera which uses a high-frequency stroboscopic ruby laser as the light source. The results obtained mainly concern explosions initiated by focused laser irradiation from a pulsed neodymium laser in a detonating gas consisting essentially of an equimolar mixture of acetylene and oxygen at an initial pressure of 100 torr at room temperature. Among the most significant observations were observations of a spherical blast wave preceded by a Chapman-Jouguet detonation which is stabilized immediately after initiation, the merging of a spherical flame with a shock front of the blast wave in which the flame is propagating, the division of a spherical detonation front into a shock wave and flame, and the generation of shock waves by a network of spherical flames.

Kamel, M. M.↗
NASA NTRS1987

Analysis and interpretation of satellite fragmentation data

The velocity perturbations of the fragments of a satellite can shed valuable information regarding the nature and intensity of the fragmentation. A feasibility study on calculating the velocity perturbations from existing equations was carried out by analyzing 23 major documented fragmentation events. It was found that whereas the calculated values of the radial components of the velocity change were often unusually high, those in the two other orthogonal directions were mostly reasonable. Since the uncertainties in the radial component necessarily translate into uncertainties in the total velocity change, it is suggested that alternative expressions for the radial component of velocity be sought for the purpose of determining the cause of the fragmentation from the total velocity change. The calculated variances in the velocity perturbations in the two directions orthogonal to the radial vector indicate that they have the smallest values for collision induced breakups and the largest values for low-intensity explosion induced breakups. The corresponding variances for high-intensity explosion induced breakups generally have values intermediate between those of the two extreme categories. A three-dimensional plot of the variances in the two orthogonal velocity perturbations and the plane change angle shows a clear separation between the three major types of breakups. This information is used to reclassify a number of satellite fragmentation events of unknown category.

Tan, Arjun↗