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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Stratospheric Circulation Changes Associated with the Hunga Tonga-Hunga Ha'apai Eruption

The 15 January 2022 eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano injected an unprecedented amount of water directly into the stratosphere. This study attempts to quantify this impact on the temperature, as well as the subsequent changes to the stratospheric circulation, during the months following the eruption based on reanalysis fields. The extreme nature of the temperature, wind, and circulation changes are tracked through comparisons of the months of 2022 with the past 42 years. Examination of the data assimilation process shows that at 20 hPa the data is forcing temperature cooling at record rates resulting in record cold temperatures. Details of the stratospheric perturbations in latitude and pressure are presented for June 2022 where record strong cooling is found at 20 hPa from 60oS to 30oS. In response to the cooling the atmosphere adjusts by creating record strong winds above the temperature anomaly and large changes to the downward and poleward mean meridional circulation.

Lawrence Coy↗
NASA NTRSDate not supplied

Using Thermal Desktop to Model the Effects of Plume Heating on MLI

Gateway draws on experience from International Space Station (ISS) and geostationary satellites for many aspects of design, including Multilayer Insulation (MLI) material selection. MLI is used on many external surfaces, some of which can be exposed to high plume heating from visiting vehicle during docking and undocking. Due to Gateway’s smaller size and closer proximity of sensitive hardware to plumes from visiting vehicles, the expected and contingency plume heating loads are higher than those experienced by the ISS. Because of MLI’s low mass and thermal conductivity between layers, high plume heating loads can potentially heat MLI past its thermal limits. MLI is typically modeled as a single node of insulation with a given effective emissivity. This method is not adequate for modeling plume heating impacts because the temperature of each individual layer cannot be determined. Modeling MLI is complicated because there are several layers and the conduction between each layer is undefined. It is further complicated by the variety of material options for MLI and their respective mass, optics, transmissivity, and temperature limits. This paper shows modeling of a MLI blanket exposed to solar and plume heating loads using Thermal Desktop. Several sensitivity studies were run including examining distance between layers, varying effective emissivity, effects of different MLI materials, and plume heating loads and durations.

MLI↗
NASA NTRSDate not supplied

Using Thermal Desktop to Model the Effects of Plume Heating on MLI

Gateway draws on experience from International Space Station (ISS) and geostationary satellites for many aspects of design, including Multilayer Insulation (MLI) material selection. MLI is used on many external surfaces, some of which can be exposed to high plume heating from visiting vehicle during docking and undocking. Due to Gateway’s smaller size and closer proximity of sensitive hardware to plumes from visiting vehicles, the expected and contingency plume heating loads are higher than those experienced by the ISS. Because of MLI’s low mass and thermal conductivity between layers, high plume heating loads can potentially heat MLI past its thermal limits. MLI is typically modeled as a single node of insulation with a given effective emissivity. This method is not adequate for modeling plume heating impacts because the temperature of each individual layer cannot be determined. Modeling MLI is complicated because there are several layers and the conduction between each layer is undefined. It is further complicated by the variety of material options for MLI and their respective mass, optics, transmissivity, and temperature limits. This paper shows modeling of a MLI blanket exposed to solar and plume heating loads using Thermal Desktop. Several sensitivity studies were run including examining distance between layers, varying effective emissivity, effects of different MLI materials, and plume heating loads and durations.

MLI↗
NASA NTRSDate not supplied

How Auroral Electron Precipitations Contribute to the Formation of Electron Heat Fluxes to the Ionosphere?

Electron heat fluxes (also called electron thermal fluxes) in the ionosphere are carried by thermal electrons whose energy is below a few eV. Electron heat fluxes greatly impact on electron temperature, which is a fundamental parameter in the ionospheric dynamics. At the high latitude in the auroral regions electron heat flux is originated dominantly from the magnetosphere through high-energy electron energy fluxes. High-energy electron fluxes in the diffuse auroral region can undergo multiple backscatters between the magnetically conjugated regions of both hemispheres, and different kind of wave-particle interactions along the magnetic field line. High-energy electron fluxes in discrete auroral region can be trapped below the auroral acceleration region and can also undergo backscatter and multiple reflection. These processes, in turn, amplify super-thermal electrons (<~500-600 eV) that dominantly form electron heat fluxes through Coulomb collision between thermal electrons. Such electron heat fluxes play an important role to determine electron temperature profile in the ionosphere, which is one of the key parameters that controls the ionospheric dynamics. Thus, it is necessary to include electron heat flux as a topside energy input in all global ionospheric models. We demonstrate all above results based on Superthermal Electron Transport (STET), Superthermal Proton, Electron and Atomic Hydrogen tRansport in the Ionosphere and Thermosphere (SPEAH-RIT), and Comprehensive Inner Magnetosphere and Ionospheres (CIMI) codes developed at NASA Goddard Space Flight Center.

George V. Khazanov↗
NASA NTRSDate not supplied

STABLE Study for the Habitable Worlds Observatory

We report on progress on the STABLE study, which was awarded on the NASA 2023 ROSES D.19 opportunity. In the study, we are developing technologies for the Habitable Worlds Observatory (HWO) in four areas: Micrometeoroid Impact Mitigation, Telescope Temperature Control, Ultra-Stable Telescope Structure Materials and Modeling, and Improvement of Thermal Expansion Test Capability. This study is a collaboration between Northrop Grumman, Kratos, NeXolve, JPL, STScI, NASA’s White Sands Test Facility, and NASA Goddard’s Ultra-Stable Test Facility. We will also discuss our plans for our follow-on study as part of NASA’s 2024 ROSES D.19. In this study, we will address additional technologies as well as perform analysis of HWO architecture options.

Habitable Worlds Observatory↗
NASA NTRS2019

Earth's Early Reduced Atmospheres

Earth’s early atmosphere evolved in response to cosmic impacts, photochemistry generated by the copious extreme ultraviolet radiation emitted by the young Sun, hydrogen escape, mineral redox buffering, the evolution of iron in the mantle, and the character of crustal weathering and subduction. No single chemical composition, surface pressure, or temperature was typical. After the biggest impacts the temperature likely rose above 3000 K and the atmosphere held rock vapor. As the atmosphere cooled its constituents rained out: first the silicates, then the geochemical volatiles (such as salt), and last the water. Depending on the size of the impact, cooling took thousands to millions of years. Between impacts the atmosphere was thick with gases like CO2, H2, and CH4 that do not condense at Earth but provide greenhouse warming that could easily have maintained surface temperatures in excess of 500 K. At some point the early atmosphere must have been conducive to the evolution of organic chemistry and the origin of life. It was therefore --- at times --- dominated by reduced gases like hydrogen and methane. Hydrogen-methane atmospheres are easily formed thermochemically after major impacts if H2O and CO2 were present on Earth in quantities consistent with their inventories on Earth today – the key is high pressure. Hydrogen-methane atmospheres slowly break down over millions of years by hydrogen escape and photochemistry. At first methane decomposes into tars and nitriles that precipitate, but later as the atmosphere grows more oxidized from hydrogen escape the methane oxidizes to CO and CO2, with a small fraction going to HCN. Impacts can also produce NH3 directly from N2 and H2O, which is expected to rain out with the H2O. As impacts grew infrequent the climate cooled in response to the fixing of CO2 as carbonate and carbonate subduction. Eventually the CO2 was mostly removed to the mantle and the surface mostly frozen.

Zahnle, Kevin↗
NASA NTRS2009

Recent Advances in Thermoplastic Puncture-Healing Polymers

Self-healing materials provide a route for enhanced damage tolerance in materials for aerospace applications. In particular, puncture-healing upon impact has the potential to mitigate significant damage caused by high velocity micrometeoroid impacts. This type of material also has the potential to improve damage tolerance in load bearing structures to enhance vehicle health and aircraft durability. The materials being studied are those capable of instantaneous puncture healing, providing a mechanism for mechanical property retention in lightweight structures. These systems have demonstrated healing capability following penetration of fast moving projectiles -- velocities that range from 9 mm bullets shot from a gun (approx.330 m/sec) to close to micrometeoroid debris velocities of 4800 m/sec. In this presentation, we report on a suite of polymeric materials possessing this characteristic. Figure 1 illustrates the puncture healing concept. Puncture healing in these materials is dependent upon how the combination of a polymer's viscoelastic properties responds to the energy input resulting from the puncture event. Projectile penetration increases the temperature in the vicinity of the impact. Self-healing behavior occurs following puncture, whereby energy must be transferred to the material during impact both elastically and inelastically, thus establishing two requirements for puncture healing to occur: a.) The need for the puncture event to produce a local melt state in the polymer material and b.) The molten material has to have sufficient melt elasticity to snap back and close the hole. 1,2 Previous ballistic testing studies revealed that Surlyn materials warmed up to a temperature approx.98 C during projectile puncture (3 C higher than it s melting temperature). 1,2 The temperature increase produces a localized flow state and the melt elasticity to snap back thus sealing the hole. Table 1 lists the commercially polymers studied here, together with their physical properties. The polymers were selected based on chemical structure, tensile strengths, tensile moduli, glass transition temperature, melting temperatures, and impact strength. The thermal properties of the polymers were characterized by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Mechanical properties were assessed by a Sintech 2W instron according to ASTM D1708 or D638 at crosshead speeds of 5.08 cm/min. 7.6 cm x 7.6 cm panels of the different materials were prepared and ballistic testing was performed at various temperatures. The panels were shot with a .223 caliber semiautomatic rifle from a distance of 23 meters at various temperatures. Chronographs were used to measure initial and final bullet velocity. Temperatures at the site of impact were measured using a FLIR ThermaCAM S60 thermal camera. A Vision Research model Phantom 9 high speed video camera was used to capture high speed video footage of ballistics testing.

Gordon, K. L.↗
NASA NTRS1992

Impact-induced thermal effects in the lunar and Mercurian regoliths

Thermal effects of micrometeoroid impact into the regoliths of the moon and Mercury, and some comparisons between the regoliths of the two bodies are presented. The impact calculations used to estimate the volumes of melt and vapor produced in the regoliths of the two bodies are described. An overview of the process of impact metamorphism in a modeled regolith target is presented, in which the roles played by impact velocity and target temperature in determining the quantities of melt and vapor are evaluated. The model impact process and fluxes are combined to estimate the production rates for impact melt and vapor on the two bodies, and the results are compared with those of previous studies. It is concluded that the rates of impact melting and vaporization on Mercury are much greater than on the moon. In a given period of time, a factor of 14 times more melt and 20 times more vapor are produced on Mercury than on the moon. A 'typical' Mercurian microcratering event produces 2.6 times more melt than its lunar counterpart; the flux calculated for Mercury is 5.5 times higher than it is at the moon.

Cintala, Mark J.↗
NASA NTRS2018

Toughness Testing for Liquid Hydrogen And Helium Temperatures - Validation of Austenitic Stainless Steels for 4K (-452F) Use

This presentation is an Existing Code Requirement: Charpy impact test at a temperature no higher than the design minimum temperature. The Current Practice: is not clear, the indications are that testing is sometimes performed at -320F (liquid nitrogen or "LN2") for that and all lower temperatures. In some cases testing is probably not performed and CGA indicated successful operation of systems at -453F without required test. The Ballot activity: C&S Connect Record 13-341, Ballot 13-1746, initially proposed Charpy testing (lateral expansion criteria) at -320F to validate use at -425 (liquid helium or "LHe"). and PTCS Proposal..

Greulich, Owen R.↗
NASA NTRS1982

Effect of matrix resin on the impact fracture characteristics of graphite-epoxy laminates

The effect of resin chemistry on basic impact energy absorbent mechanisms exibited by graphite-epoxy composites was investigated. Impact fracture modes and microscopic resin deformation characteristics were examined for 26 NASA-impacted graphite epoxy laminates with different resin chemistries. Discrete specimen fracture modes were identified through cross sectional examination after impact, and subsequently compared with measured glass transition temperatures, cure cycles, and residual impact capabilities. Microscopic resin deformation mechanisms and their overall relationship to impact loading conditions, voids, and resin content were also characterized through scanning electron microscopic examination of separated fracture surfaces.

Hertzberg, P. E.↗
NASA NTRS2003

Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

The main objective of this NASA Faculty Awards for Research (FAR) project is to conduct ultrasonic assessment of impact-induced damage and microcracking in fiber-metal laminated (FML) composites at various temperatures. It is believed that the proposed study of impact damage assessment on FML composites will benefit several NASA's missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass- (for GLARE) and aramid- (for ARALL) fiber reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 2024-T3 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating cracks emanating from the impact site, ring cracks surrounding the impact site, partial and full delamination, and combinations of these damages.

Gyekanyesi, John↗
NASA NTRSDate not supplied

Convolution-Based Numerical Solutions of Transient Temperature Fields during Powder Bed Fusion Additive Manufacturing: Theory, Accuracy, and Computational Cost

Powder bed fusion (PBF) additive manufacturing has found numerous applications in the aerospace domain. However, components fabricated via PBF have a complex time-temperature history that significantly impacts subsequent mechanical performance. This study examines convolution-based numerical solutions of transient temperature fields that support simulations involving arbitrary beam shapes and paths during PBF. The convolutional approach is verified through comparisons with analytical solutions of the temperature field. The computational speed and accuracy of the method are assessed through comparisons with other explicit and implicit numerical techniques. In addition, the straightforward translation of the approach from a CPU to a GPU implementation and the resultant performance improvement are presented. The role of the technique in predicting microstructure evolution during PBF (for a greater process-structure-property-performance framework) is also demonstrated. This work supports the development of computational materials methods for understanding and controlling the time-temperature history during PBF.

powder bed fusion↗
NASA NTRS2015

Development of a Near Real-Time Hail Damage Swath Identification Algorithm for Vegetation

Every year in the Midwest and Great Plains, widespread greenness forms in conjunction with the latter part of the spring-summer growing season. This prevalent greenness forms as a result of the high concentration of agricultural areas having their crops reach their maturity before the fall harvest. This time of year also coincides with an enhanced hail frequency for the Great Plains (Cintineo et al. 2012). These severe thunderstorms can bring damaging winds and large hail that can result in damage to the surface vegetation. The spatial extent of the damage can relatively small concentrated area or be a vast swath of damage that is visible from space. These large areas of damage have been well documented over the years. In the late 1960s aerial photography was used to evaluate crop damage caused by hail. As satellite remote sensing technology has evolved, the identification of these hail damage streaks has increased. Satellites have made it possible to view these streaks in additional spectrums. Parker et al. (2005) documented two streaks using the Moderate Resolution Imaging Spectroradiometer (MODIS) that occurred in South Dakota. He noted the potential impact that these streaks had on the surface temperature and associated surface fluxes that are impacted by a change in temperature. Gallo et al. (2012) examined at the correlation between radar signatures and ground observations from storms that produced a hail damage swath in Central Iowa also using MODIS. Finally, Molthan et al. (2013) identified hail damage streaks through MODIS, Landsat-7, and SPOT observations of different resolutions for the development of a potential near-real time applications. The manual analysis of hail damage streaks in satellite imagery is both tedious and time consuming, and may be inconsistent from event to event. This study focuses on development of an objective and automatic algorithm to detect these areas of damage in a more efficient and timely manner. This study utilizes the MODIS sensor aboard the NASA Aqua satellite. Aqua was chosen due to an afternoon orbit over the United States when land surface temperatures are relatively warm and improve the contrast between damaged and undamaged areas. This orbit is also similar to the orbit of the Suomi-National Polar-orbiting Partnership (NPP) satellite. The Suomi NPP satellite hosts the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument, which is the next generation of a MODIS-like sensor in polar orbit.

MODIS VIIRS↗
NASA NTRSDate not supplied

Trade-Offs of Simplified Versus Comprehensive Representation of Mineralogy When Studying Dust Impacts on Earth’s Climate Systems

The intensity and direction of dust impacts on Earth’s climate systems depend on mineral composition. For example, the presence or absence of a few percent of iron oxides in dust will determine if dust is warming or cooling the atmosphere. Similarly, feldspar will enhance ice cloud formation, while acid gases in the atmosphere will react on the surface of dust calcite limiting acid rain. Still, most climate models use a simplified representation of dust mineralogy. They assume a fixed composition at emission which stays invariant during transport and removal. Such simplification assumes spatially and temporally constant physical and chemical properties of dust, and appears to provide satisfactory results when comparing some properties with observations. The trade-off is their lack of spatial gradients, which will fail to induce circulation, cloud and precipitation changes. The two reasons to omit mineral variations are the uncertainty of current atlases of soil mineral composition in arid regions, and, more practically, an improved runtime efficiency. The former reason is losing ground with the recent launch (July 2022) of a dedicated mission (NASA/JPL EMIT) to retrieve global soil mineralogy of dust sources at high spatial resolution. While the EMIT science team is finalizing a satisfactory global map of mineral composition of dust sources, we analyzed the interaction of dust mineralogy on radiation and its impact on the fast temperature response using different representations of mineral composition from detailed and spatially varying to simplified and globally uniform, assuming different hematite contents and methods to calculate optical properties. Our results show that resolving dust mineralogy reduces dust absorption, and results in improved agreement with observation-based single scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth’s Radiant Energy System), and land surface temperature from CRU (Climatic Research Unit), compared to the baseline bulk dust model version. It also results in distinct radiative impacts on Earth’s climate over North Africa. From our 19-year simulation, we will show that it leads to a reduction of over 50% in net downward radiation at top of atmosphere (TOA) across the Sahara and an approximately 20% reduction over the Sahel. We will explain how the surface temperature response affects the monsoon flow from the Gulf of Guinea. Interestingly, we find similar results by simply fixing the hematite content of dust to a globally uniform value of 0.9% by volume. We will discuss the underlying reasons for such results and show that they may be unrelated to the distribution of soil mineralogy. Still, an accurate representation of soil mineralogy is necessary to better understand dust impacts on the Earth’s climate systems.

dust impacts↗
NASA NTRS1987

Elastomer Compatible With Oxygen

Artificial rubber resists ignition on impact and seals at low temperatures. Filled fluoroelastomer called "Katiflex" developed for use in seals of vessels holding cold liquid and gaseous oxygen. New material more compatible with liquid oxygen than polytetrafluoroethylene. Provides dynamic seal at -196 degrees C with only 4 times seal stress required at room temperature. In contrast, conventional rubber seals burn or explode on impact in high-pressure oxygen, and turn hard or even brittle at liquid-oxygen temperatures, do not seal reliably, also see (MFS-28124).

Martin, Jon W.↗
NASA NTRS1995

A Petrographic History of Martian Meteorite ALH84001: Two Shocks and an Ancient Age

ALH84001 is an igneous meteorite, an orthopyroxenite of martian origin. It contains petrographic evidence of two shock metamorphic events, separated by thermal and chemical events. The evidence for two shock events suggests that ALH84001 is ancient and perhaps a sample of the martian highlands. From petrography and mineral chemistry, the history of ALH84001 must include: crystallization from magma, a first shock (impact) metamorphism, thermal metamorphism, low-temperature chemical alteration, and a second shock (impact) metamorphism. Originally, ALH84001 was igneous, an orthopyroxene-chromite cumulate. In the first shock event, the igneous rock was cut by melt-breccia or cataclastic veinlets, now bands of equigranular fine-grained pyroxene and other minerals (crush zones). Intact fragments of the cumulate were fractured and strained (now converted to polygonized zones). The subsequent thermal metamorphism (possibly related to the first shock) annealed the melt-breccia or cataclastic veinlets to their present granoblastic texture and permitted chemical homogenization of all mineral species present. The temperature of metamorphism was at least 875 C, based on mineral thermometers. Next, Mg-Fe-Ca carbonates and pyrite replaced plagioclase in both clasts and granular bands, producing ellipsoidal carbonate globules with sub-micron scale compositional stratigraphy, repeated identically in all globules, The second shock event produced microfault offsets of carbonate stratigraphy and other mineral contacts, radial fractures around chromite and maskelynite, and strain birefringence in pyroxene. Maskelynite could not have been preserved from the first shock event, because it would have crystallized back to plagioclase. The martian source area for ALH84001 must permit this complex, multiple impact history. Very few craters on young igneous surfaces are on or near earlier impact features. It is more likely that ALH84001 was ejected from an old igneous unit (Hesperian or Noachian age), pocked by numerous impact craters over its long exposure at the martian surface.

Treiman, Allan H.↗
NASA NTRS2012

Multi-Factor Impact Analysis of Agricultural Production in Bangladesh with Climate Change

Diverse vulnerabilities of Bangladesh's agricultural sector in 16 sub-regions are assessed using experiments designed to investigate climate impact factors in isolation and in combination. Climate information from a suite of global climate models (GCMs) is used to drive models assessing the agricultural impact of changes in temperature, precipitation, carbon dioxide concentrations, river floods, and sea level rise for the 2040-2069 period in comparison to a historical baseline. Using the multi-factor impacts analysis framework developed in Yu et al. (2010), this study provides new sub-regional vulnerability analyses and quantifies key uncertainties in climate and production. Rice (aman, boro, and aus seasons) and wheat production are simulated in each sub-region using the biophysical Crop Environment REsource Synthesis (CERES) models. These simulations are then combined with the MIKE BASIN hydrologic model for river floods in the Ganges-Brahmaputra-Meghna (GBM) Basins, and the MIKE21Two-Dimensional Estuary Model to determine coastal inundation under conditions of higher mean sea level. The impacts of each factor depend on GCM configurations, emissions pathways, sub-regions, and particular seasons and crops. Temperature increases generally reduce production across all scenarios. Precipitation changes can have either a positive or a negative impact, with a high degree of uncertainty across GCMs. Carbon dioxide impacts on crop production are positive and depend on the emissions pathway. Increasing river flood areas reduce production in affected sub-regions. Precipitation uncertainties from different GCMs and emissions scenarios are reduced when integrated across the large GBM Basins' hydrology. Agriculture in Southern Bangladesh is severely affected by sea level rise even when cyclonic surges are not fully considered, with impacts increasing under the higher emissions scenario.

Ruane, Alex C.↗