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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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NASA NTRS1994

The dynamical and radiative evolution of clumpy supernova ejecta

Numerical simulations describing the dynamical and radiative evolution of clumpy supernova ejecta are compared with observations of optical and radio emission knots in supernova remnant (SNR) Cassiopeia A. Three major phases are identified in the evolution of clumpy ejecta: a bow-shock phase, an instability phase, and a dispersal phase. The phenomenological and radiative signatures of each phase are discussed and compared with multi-epoch measurements of small-scale features in Cas A. Good correspondence is found between theory and observations. Both support the premise that compact radio emission features are controlled more by magnetic field amplification triggered in the instability phase than by in situ acceleration of new relativistic particles.

Anderson, M. C.↗
NASA NTRS1994

Extinction, ejecta masses, and radial velocities of novae

Interstellar reddening is determined for a number of recent novae based upon emission-line ratios which are generally observable using CCDs. Large values of extinction are found for most systems, possibly indicative of an intrinsic component of reddening in postoutburst novae. The unusual characteristics of the (O I) lines in novae, which are strong and optically thick, require a large population of very dense globules which are the likely sites of dust formation. These pyroclasts must be ejected from the white dwarf. The total mass of the neutral gas in the globules in some of the objects is substantially larger than the masses normally derived for the ionized ejecta of novae. The distribution of radial velocities of Galactic novae in the Tololo sample, although uncertain, shows an asymmetry in having predominantly negative values. Either high internal absorption in the expanding ejecta skews the emission lines to bluer wavelengths, or most of the novae are moving out from the center of the Galaxy.

Williams, Robert E.↗
NASA NTRS1994

The dust in the hydrogen-poor ejecta of Abell 30

We present new optical and near-infrared images of the hydrogen-poor planetary nebula Abell 30 and produce detailed models that account for the major observed morphological and IR properties. By imaging the nebula in the K band, we confirm the presence of hot dust in an expanding equatorial ring of H-poor gas. No emission was detected from the H-poor polar knots, suggesting a dust deficiency htere relative to the equatorial ring. The near-IR emission is attributed to small carbonaceous dust grains which are stochastically heated by stellar ultraviolet photons. Using an adaptive version of a matrix method devised by Guhathakurta & Draine (1989) to model stochastic heating, we find that the near-IR spectrum observed by Dinerstein & Lester (1984) requires the presence of dust grains down to approximately 0.0007 microns in radius. This minimum grain radius is in excellent agreement with our calculations of the grain destruction by energetic stellar UV photons: we find that carbon clusters with less than approximately 140 atoms (0.0007 microns in radius) are destroyed by stellar UV photons in approximately 1000 yr, the kinematic age of H-poor ejecta. Modeling of the far-IR dust emission implies that the bulk of the dust mass in A30 must reside at distances several times greater than the distance of the equatorial ring from the central star. This spatial dust distribution is attributed to the interaction of the stellar wind with the inhomogeneous H-poor ejecta. Most of the H-poor gas and dust has been apparently carried outward by the stellar wind, leaving behing dense, H-poor knots with prominent wind-blown tails in the equatorial ring and in the polar knots. This picture is supported by the presence of a stellar wind-blown bubble within the H-rich envelope in our optical images.

Borkowski, Kazimierz J.↗
NASA NTRS1998

Integrated Studies of Impact-Basin Ejecta as Probes of the Lunar Crust: Imbrium and Serenitatis

The large, late, basin impacts on the Earth side of the Moon fundamentally reshaped the structure of the crust, its surface morphology, and the composition of the megaregolith and surface soils. The latest (except for Orientale on the western limb) and largest was the Imbrium impact, which produced massive ejecta deposits over much of the Procellarum region and beyond, and ejected material that mixed with surface regolith nearly Moonwide. The basins serve as natural probes into the lunar crust; therefore, understanding the nature and composition of ejecta produced by them provides information about the crust at depth. Gravity data allow modeling of the structure of the crust beneath the basins, and from such models one can infer depths of excavation and the nature of crustal response following impact.

Jolliff, Brad L.↗
NASA NTRS2000

Chicxulub High-Altitude Ballistic Ejecta from Central Belize

Chicxulub ejecta are found in central Belize, 475 km southeast of the impact crater center. These deposits are ballistic ejecta launched along high-altitude trajectories above the atmosphere and deposited as a discontinuous sheet on the terminal Cretaceous land surface.

Pope, K. O.↗
NASA NTRS2002

The Fate of Ejecta from Hyperion

Ejecta from Saturn's moon Hyperion is subject to powerful perturbations from nearby Titan, which control its ultimate fate. We have performed numerical integrations to simulate a simplified system consisting of Saturn (including oblateness), Tethys, Dione, Titan, Hyperion, Iapetus, and the Sun (treated simply as a massive satellite). In addition, 1050 massless particles were ejected from Hyperion at five different points in its orbit. These particles started more or less evenly distributed over latitude and longitude, 1 km above Hyperion's mean radius, and were ejected radially outward at speeds 10\% faster than its escape speed. Only about 4\% of the particles survived for the 100,000-year course of the integration, while $\sim$8/% escaped from the Saturnian system. Titan accreted $\sim$77\% of all the particles, while Hyperion reaccreted only $\sim$5\%. This may help to account for Hyperion's rugged shape. Three particles hit Rhea and 2 hit Dione, but $\sim$5\% of the particles were removed when they penetrated within 150,000 km of Saturn. Most removals occurred within the first few thousand years. In general, ejecta from Hyperion are much more widely scattered than previously thought, and cross the orbits of all of the other classical satellites.

Lissauer, Jack J.↗
NASA NTRS2000

Mapping the X-Ray-Emitting Ejecta in Cassiopeia A with Chandra

We present X-ray emission-line equivalent width images of the bright Galactic supernova remnant Cassiopeia A for the elements Si, S, Ar, Ca, and Fe using a 50,000 s observation with the Advanced CCD Imaging Spectrometer on the Chandra X-Ray Observatory. The images essentially map the bulk of detectable ejecta of these elements over a wide range of surface brightnesses and show morphologies distinctly different from that of the broadband X-ray emission and the 4-6 keV continuum emission. The Si, S, Ar, and Ca maps, while different in turn from those of Fe, are similar to the distribution of fast optical ejecta knots in that they clearly delineate the X-ray counterpart of the northeast optical jet. Low surface brightness regions just outside the bright shell in the north and west are also shown to have strong line emission. The strong Fe emission is exterior to that of other elements in the east, as previously noted, but is generally coincident elsewhere. The projected interior has relatively little emission traced by high line equivalent widths.

Hwang, Una↗
NASA NTRS2003

Ejecta from Ocean Impacts

Numerical simulations of deep-ocean impact provide some limits on the size of a projectile that will not mix with the ocean floor during a deep-ocean impact. For a vertical impact at asteroidal velocities (approx. 20 km/s), mixing is only likely when the projectile diameter is greater than 112 of the water depth. For oblique impacts, even larger projectiles will not mix with ocean floor silicates. Given the typical water depths of 4 to 5 km in deep-ocean basins, asteroidal projectiles with diameters as large as 2 or 3 km may commonly produce silicate ejecta that is composed only of meteoritic materials and seawater salts. However, the compressed water column beneath the projectile can still disrupt and shock metamorphose the ocean floor. Therefore, production of a separate, terrestrial ejecta component is not ruled out in the most extreme case. With increasing projectile size (or energy) relative to water depths, there must be a gradation between oceanic impacts and more conventional continental impacts. Given that 60% of the Earth's surface is covered by oceanic lithosphere and 500 m projectiles impact the Earth on 10(exp 5) y timescales, there must be hundreds of oceanic impact deposits in the sediment record awaiting discovery.

Kyte, Frank T.↗
NASA NTRS1995

Chicxulub Ejecta Blanket Deposits From Belize

The Chicxulub impact into a thick sequence of carbonates and sulfates released over a trillion tons of volatiles. The importance of the explosive release of such a large mass of volatiles has been greatly underestimated in studies of ejecta depositional processes. Proximal Chicxulub ejecta blanket deposits recent discovered on Albion Island in Belize provide a key to understanding the role of volatile-rich target material during large impact events.

Chicxulub Belize↗
NASA NTRS2009

An Impact Sensor System for the Characterization of the Micrometeoroid and Lunar Secondary Ejecta Environment

The Impact Sensor for Micrometeoroid and Lunar Secondary Ejecta (IMMUSE) project aims to apply and integrate previously demonstrated impact sensing subsystems to characterize the micrometeoroid and lunar secondary (MMSE) environment on the surface of the Moon. Once deployed, data returned from IMMUSE will benefit: (1) Fundamental Lunar Science: providing data to improve the understanding of lunar cratering processes and dynamics of the lunar regolith. (2) Lunar Exploration Applied Science: providing an accurate MMSE environment definition for reliable impact risk assessments, cost-effective shielding designs, and mitigation measures for long-term lunar exploration activities. (3) Planetary Science: providing micrometeoroid data to aid the understanding of asteroidal collisions and the evolution of comets. A well-established link between micrometeoroid impacts and lunar regolith is also key to understanding other regolith-covered bodies from remote-sensing data. The IMMUSE system includes two components: (1) a large area (greater than or equal to 1 m2) micrometeoroid detector based on acoustic impact and fiber optic displacement sensors and (2) a 100 cm2 lunar secondary ejecta detector consisting of dual-layer laser curtain and acoustic impact sensors. The combinations of different detection mechanisms will allow for a better characterization of the MMSE environment, including flux, particle size/mass, and impact velocity. IMMUSE is funded by the NASA LASER Program through 2012. The project fs goal is to reach a Technical Readiness Level of 4 in preparation for a more advanced development beyond 2012. Several prototype subsystems have been constructed and subjected to low impact and hypervelocity impact tests. The presentation will include a status review and preliminary test results.

Liou, J.-C.↗
NASA NTRS2012

A Suzaku Study of Ejecta Structure and Origin of Hard X-ray Emission in the Supernova Remnant G156.2+5.7

We report an X-ray study of the evolved Galactic supernova remnant (SNR) G1S6.2+S.7 based on six pointing observations with Suzaku. The remnant's large extent (100' in diameter) allows us to investigate its radial structure in the northwestern and eastern directions from the apparent center. The X-ray spectra. were well fit with a two-component non-equilibrium ionization model representing the swept-up interstellar medium (ISM) and the metal-rich ejecta. We found prominent central concentrations of Si, S and Fe from the ejecta component; the lighter elements of O, Ne and Mg were distributed more uniformly. The temperature of the ISM component suggests a slow shock (610-960 km/s), hence the remnant's age is estimated to be 7,000-15,000 yr, assuming its distance to be approx. 1.1 kpc. G1S6.2+5.7 has also been thought to emit hard, non-thermal X-rays, despite being considerably older than any other such remnant. In response to a recent discovery of a background cluster of galaxies (2XMM J045637.2+522411), we carefully excluded its contribution, and reexamined the origin of the hard X-ray emission. We found that the residual hard X-ray emission is consistent with the expected level of the cosmic X-ray background. Thus, no robust evidence for the non-thermal emission was obtained from G156.2+5.7. These results are consistent with the picture of an evolved SNR.

Uchida, Hiroyuki↗
NASA NTRS2014

The Host Galaxies of Fast-Ejecta Core-Collapse Supernovae

Spectra of broad-lined Type Ic supernovae (SN Ic-BL), the only kind of SN observed at the locations of long-duration gamma-ray bursts (LGRBs), exhibit wide features indicative of high ejecta velocities ((is) approximately 0.1c). We study the host galaxies of a sample of 245 low-redshift (z (is) less than 0.2) core-collapse SN, including 17 SN Ic-BL, discovered by galaxy-untargeted searches, and 15 optically luminous and dust-obscured z (is) less than 1.2 LGRBs. We show that, in comparison with SDSS galaxies having similar stellar masses, the hosts of low-redshift SN Ic- BL and z (is) is less than 1.2 LGRBs have high stellar-mass and star-formation-rate densities. Core-collapse SN having typical ejecta velocities, in contrast, show no preference for such galaxies. Moreover, we find that the hosts of SN Ic-BL, unlike those of SN Ib/Ic and SN II, exhibit high gas velocity dispersions for their stellar masses. The patterns likely reflect variations among star-forming environments, and suggest that LGRBs can be used as probes of conditions in high-redshift galaxies. They may be caused by efficient formation of massive binary progenitors systems in densely star-forming regions, or, less probably, a higher fraction of stars created with the initial masses required for a SN Ic-BL or LGRB. Finally, we show that the preference of SN Ic-BL and LGRBs for galaxies with high stellar-mass and star-formation-rate densities cannot be attributed to a preference for low metal abundances but must reflect the influence of a separate environmental factor.

collapse↗
NASA NTRS2016

Distal Ejecta from Lunar Impacts: Extensive Regions of Rocky Deposits

Lunar Reconnaissance Orbiter (LRO) Diviner Radiometer, Mini-RF, and LRO Camera data were used to identify and characterize rocky lunar deposits that appear well separated from any potential source crater. Two regions are described: 1) A approximate 18,000 sq km area with elevated rock abundance and extensive melt ponds and veneers near the antipode of Tycho crater (167.5 deg E, 42.5 deg N). This region has been identified previously, using radar and aging data. 2) A much larger and more diffuse region, covering approximately 730,000 sq km, centered near 310 deg E, 35 deg S, containing elevated rock abundance and numerous granular flow deposits on crater walls. The rock distributions in both regions favor certain slope azimuths over others, indicating a directional component to the formation of these deposits. The spatial distribution of rocks is consistent with the arrival of ejecta from the west and northwest at low angles (approximately 10-30 deg) above the horizon in both regions. The derived age and slope orientations of the deposits indicate that the deposits likely originated as ejecta from the Tycho impact event. Despite their similar origin, the deposits in the two regions show significant differences in the datasets. The Tycho crater antipode deposit covers a smaller area, but the deposits are pervasive and appear to be dominated by impact melts. By contrast, the nearside deposits cover a much larger area and numerous granular flows were triggered. However, the features in this region are less prominent with no evidence for the presence of impact melts. The two regions appear to be surface expressions of a distant impact event that can modify surfaces across wide regions, resulting in a variety of surface morphologies. The Tycho impact event may only be the most recent manifestation of these processes, which likely have played a role in the development of the regolith throughout lunar history

Bandfield, Joshua L.↗
NASA NTRS2019

Spaceflight Hazards of Escape-Velocity-Domain Impact Ejecta in the CR3BP

As a consequence of planned/proposed human lunar activity, the long-term effects of lunar debris and ejecta resulting from large-body (> 1000 kg) impacts on the lunar surface is investigated. The Escape-Velocity-Domain (EVD) ejecta behavior is characterized in terms of destination, duration in lunar orbit, and total displaced mass. Likewise, the amount of mass sent into geosynchronous orbit is also characterized and assessed as a function of impact location in terms of Sun-Earth-Moon angle, lunar latitude and longitude, and impact angle. Finally, a threat analysis is performed on critical assets in Earth and Lunar orbit such as the I.S.S., geosynchronous satellites, prospective lunar base, and the Deep Space Gateway now under construction.

Wittal, M. M.↗
NASA NTRSDate not supplied

The Effects of Arcing Ejecta on Space Suit Materials from ISS RPCM Hot Mate/Demate During EVA

Onboard ISS, taking systems off-line when powering down to perform servicing on Remote Power Control Modules (RPCMs) introduces operational risk. An investigation lead by the NASA Engineering and Safety Center (NESC) was performed by a multi-center team to assess the safety of performing on-orbit replacement of RPCMs without powering down. This investigation revealed the potential for molten metal particulate generation in the event of an arcing occurrence. As RPCM replacement can be performed outside ISS during an Extra Vehicular Activity (EVA), it is necessary to assess the effects of this molten metal ejecta contact with the Extravehicular Mobility Unit (EMU) Space Suit Assembly (SSA) during an arcing event. A test was devised to mimic arcing ejecta contact with samples representing various SSA cross-sections. Four areas of the SSA were chosen for test to represent the majority of the SSA cross-sections. Testing was conducted by the University of California, Riverside that generated the molten metal particles, included varying composition, size and temperature, and dropped them onto the surface of the various SSA cross-sections. Exposed SSA materials were then evaluated for degree of damage, penetration, and thermal conductance through the cross-section by ILC Dover. Results showed that the SSA Glove is most susceptible to damage from arcing events. This data will be used to make risk management decisions for future RPCM servicing operations. This testing also demonstrated the durability of the SSA design and materials to exposure to extreme environments

Linda S Hewes↗
NASA NTRS2019

Meteoroids at the Moon: Orbital Properties, Surface Vaporization, and Impact Ejecta Production

We use a dynamical model to characterize the monthly and yearly variations of the lunar meteoroid environment for meteoroids originating from short and long‐period comets and the main‐belt asteroids. Our results show that if we assume the meteoroid mass flux of 43.3 tons per day at Earth, inferred from previous works, the mass flux of meteoroids impacting the Moon is 30 times smaller, approximately 1.4 tons per day, and shows variations of the order of 10% over a year. The mass flux difference is due to the combined effect of the smaller cross‐section of the Moon (factor of 13.46) and Earth's larger gravitational focusing (factor of 2–2.5). The lunar surface is vaporized by these impactors at an average impact vaporization flux of 11.6 × 10−16 g·cm−2·s−1, providing a significant source for the rarefied lunar exosphere. Our model predicts acceptable vaporization rates and reproduces the local time dependence of observations of the dust ejecta cloud, measured by the Lunar Dust Experiment on board NASA's Lunar Atmosphere and Dust Environment (LADEE) satellite. However, the predicted density of the lunar ejecta cloud is four orders of magnitude larger than reported values by LADEE. This discrepancy might be attributed to a much lower yield from meteoroid impacts on fluffy lunar regolith and/or a lower detection efficiency of the LADEE dust detector. We suggest an upper limit of 30 cm per million years for the soil gardening rate from small meteoroids.

Petr Pokorny↗
NASA NTRSDate not supplied

The Effects of Arcing Ejecta on Space Suit Materials from ISS RPCM Hot Mate/Demate During EVA

Onboard ISS, taking systems off-line when powering down to perform servicing on Remote Power Control Modules (RPCMs) introduces operational risk. An investigation lead by the NASA Engineering and Safety Center (NESC) was performed by a multi-center team to assess the safety of performing on-orbit replacement of RPCMs without powering down. This investigation revealed the potential for molten metal particulate generation in the event of an arcing occurrence. As RPCM replacement can be performed outside ISS during an Extra Vehicular Activity (EVA), it is necessary to assess the effects of this molten metal ejecta contact with the Extravehicular Mobility Unit (EMU) Space Suit Assembly (SSA) during an arcing event. A test was devised to mimic arcing ejecta contact with samples representing various SSA cross-sections. Four areas of the SSA were chosen for test to represent the majority of the SSA cross-sections. Testing was conducted by the University of California, Riverside that generated the molten metal particles, included varying composition, size and temperature, and dropped them onto the surface of the various SSA cross-sections. Exposed SSA materials were then evaluated for degree of damage, penetration, and thermal conductance through the cross-section by ILC Dover. Results showed that the SSA Glove is most susceptible to damage from arcing events. This data will be used to make risk management decisions for future RPCM servicing operations. This testing also demonstrated the durability of the SSA design and materials to exposure to extreme environments.

Linda S. Hewes↗