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NASA NTRSDate not supplied

Icing Physics Studies Using the 3D SIDRM Test Article: Ice Crystal Icing Analysis

In-flight icing is an important safety issue and is a factor that affects aircraft design and performance. Newer regulations are driving a need for improvements in airframe and engine icing simulation capability. Experimental data is required for the development of icing physics models and simulation validation. This paper presents the analysis of the ice crystal icing data subset from tests conducted in 2022 at the NASA Icing Research Tunnel that studied both supercooled liquid and ice-crystal icing. The test article that was utilized replicated 3D geometrical features of an inter-compressor duct and strut region of a turbofan engine. The surfaces of the Simulated Inter-compressor Duct Research Model (SIDRM) can be heated to simulate the warm surfaces of the turbofan inter-compressor duct. The test article is instrumented with pressure taps, heaters, heat flux gauges, and thermocouples, while a 3D laser scanner, cameras, and a weighing scale to measure ice mass were utilized to characterize the icing behavior. The aim of these tests was to generate ice accretions on the SIDRM test article under well-characterized icing conditions. To that end, ice crystal cloud characterization tests were conducted that provided cloud property values at the test section. The ice crystal accretion tests investigated how different test condition parameters impacted ice accretion size, location, and characteristics (such as physical attributes). A key finding was that a sufficiently high surface heat flux at the leading edge can provide a continuous supply of liquid melt to critical accretion zones downstream, resulting in elevated ice mass accretions. Another key finding was that warmer heater settings in critical accretion zones can suppress ice accretion. These findings are consistent with icing behavior observed in full-scale engine icing tests conducted previously at the NASA Glenn Research Center. Test runs investigating the contribution of liquid melt generated at the leading edge found that the melt can be transported downstream to critical accretion regions in two forms, via runback and splash. The form of melt supplied downstream affected accretion behavior and features. Sharkteeth-shaped ice accretions were generated at certain test conditions, a physical attribute that has been observed in full-scale engine icing tests. The ice accretion data will be used to develop and validate 3D computational engine icing tools, such as GlennICE, that predictively assesses the onset and growth of ice. One of the goals of the sponsoring NASA project is to develop simulation models and tools that can assist in the design and certification of engines for flight in icing conditions in a cost‑effective way.

ice crystal icing↗

NASA NTRSDate not supplied

Icing Physics Studies Using the 3D SIDRM Test Article: Ice Crystal Icing Analysis

ice crystal icing↗

NASA NTRS1950

Icing-Protection Requirements for Reciprocating-Engine Induction System

Despite the development of relatively ice-free fuel-metering systems, the widespread use of alternate and heated-air intakes, and the use of alcohol for emergency de-icing, icing of aircraft-engine induction systems is a serious problem. Investigations have been made to study and to combat all phases of this icing problem. From these investigations, criterions for safe operation and for design of new induction systems have been established. The results were obtained from laboratory investigations of carburetor-supercharger combinations, wind-tunnel investigations of air scoops, multicylinder-engine studies, and flight investigations. Characteristics of three forms of ice, impact, throttling, and fuel evaporation were studied. The effects of several factors on the icing characteristics were also studied and included: (1) atmospheric conditions, (2) engine and air-scoop configurations, including light-airplane system, (3) type fuel used, and (4) operating variables, such as power condition, use of a manifold pressure regulator, mixture setting, carburetor heat, and water-alcohol injection. In addition, ice-detection methods were investigated and methods of preventing and removing induction-system ice were studied. Recommendations are given for design and operation with regard to induction-system design.

Coles, Willard D↗

NASA NTRS2005

Space Shuttle Main Engine Debris Testing Methodology and Impact Tolerances

In the wake of the Space Shuttle Columbia disaster every effort is being made to determine the susceptibility of Space Shuttle elements to debris impacts. Ice and frost debris is formed around the aft heat shield closure of the orbiter and liquid hydrogen feedlines. This debris has been observed to liberate upon lift-off of the shuttle and presents potentially dangerous conditions to the Space Shuttle Main Engine. This paper describes the testing done to determine the impact tolerance of the Space Shuttle Main Engine nozzle coolant tubes to ice strikes originating from the launch pad or other parts of the shuttle.

Gradl, Paul R.↗

NASA NTRS1987

Experimental studies on the impact properties of water ice

Experimental studies on the impact of ice particles at very low velocity were continued. These measurements have applications in the dynamics of Saturn's rings. Initially data were obtained on the coefficient of restitution for ice spheres of one radius of curvature. The type of measurements were expanded to include restitution data for balls with a variety of surfaces as well as sticking forces between ice particles. Significant improvements were made to this experiment, the most important being the construction of a new apparatus. The new apparatus consists of a smaller version of the disk pendulum and a stainless steel, double-walled cryostat. The apparatus has proved to be a significant improvement over the old one. Measurements can now be made at temperatures near 90 K, comparable to the temperature of the environment of Saturn's rings, and with much greater temperature stability. It was found that a roughened contact surface or the presence of frost can cause a much larger change in the restitution measure than the geometrical effect of the radius of curvature.

Bridges, F. G.↗

DOE OSTI2024

Measurement of Photovoltaic Module Deformation Dynamics During Hail Impact Using Digital Image Correlation

Stereo high-speed video of photovoltaic modules undergoing laboratory hail tests was processed using digital image correlation to determine module surface deformation during and immediately following impact. The purpose of this work was to demonstrate a methodology for characterizing module impact response differences as a function of construction and incident hail parameters. Video capture and digital image analysis were able to capture out-of-plane module deformation to a resolution of ±0.1 mm at 11 kHz on an in-plane grid of 10 × 10 mm over the area of a 1 × 2 m commercial photovoltaic module. With lighting and optical adjustments, the technique was adaptable to arbitrary module designs, including size, backsheet color, and cell interconnection. Furthermore, impacts were observed to produce an initially localized dimple in the glass surface, with peak deflection proportional to the square root of incident energy. Subsequent deformation propagation and dissipation were also captured, along with behavior for instances when the module glass fractured. Natural frequencies of the module were identifiable by analyzing module oscillations postimpact. Limitations of the measurement technique were that the impacting ice ball obscured the data field immediately surrounding the point of contact, and both ice and glass fracture events occurred within 100 μs, which was not resolvable at the chosen frame rate. Increasing the frame rate and visualizing the back surface of the impact could be applied to avoid these issues. Applications for these data include validating computational models for hail impacts, identifying the natural frequencies of a module, and identifying damage initiation mechanisms.

14 SOLAR ENERGY↗

NASA NTRS1992

Water on Mars: Inventory, distribution, and possible sources of polar ice

Theoretical considerations and various lines of morphologic evidence suggest that, in addition to the normal seasonal and climatic exchange of H2O that occurs between the Martian polar caps, atmosphere, and mid to high latitude regolith, large volumes of water have been introduced into the planet's long term hydrologic cycle by the sublimation of equatorial ground ice, impacts, catastrophic flooding, and volcanism. Under the climatic conditions that are thought to have prevailed on Mars throughout the past 3 to 4 b.y., much of this water is expected to have been cold trapped at the poles. The amount of polar ice contributed by each of the planet's potential crustal sources is discussed and estimated. The final analysis suggests that only 5 to 15 pct. of this potential inventory is now in residence at the poles.

Clifford, S. M.↗

NASA NTRS1997

Climate Variability in the Amundsen and Bellingshausen Seas

Satellite data reveal a 20% decline in sea ice extent in the Amundsen and Bellingshausen Seas in the two decades following 1973. This change is negatively correlated with surface air temperatures on the west side of the Antarctic Peninsula, which have increased -0.5 C / decade- since the mid-1940s, The recession was strongest during summer, when monthly average minima in 1991-92 removed much of the incipient multiyear ice over the continental shelf. This would have lowered the regional-mean ice thickness, impacting snow ice formation, brine production, and vertical heat flux. The northern ice edge contracted by 1 deg of latitude in all seasons from 1973-79 to 1987-93, returning toward mean conditions in 1993-95. The decline included multiyear cycles of several years in length, superimposed on high interannual variability. A review of atmospheric forcing shows winds consistent with mean and extreme ice extents, and suggests links to larger-scale circulation changes in the South Pacific. Historical ocean measurements are sparse in this sector, but mixed-layer depths and upper pycnoclines beneath the sea ice resemble those in the Weddell Sea. Weaker surface currents or changes in the upwelling of Circumpolar Deep Water on the continental shelf could have contributed to the anomaly persistence.

Jacobs, Stanley S.↗

NASA NTRS2011

Cavity Heating Experiments Supporting Shuttle Columbia Accident Investigation

The two-color thermographic phosphor method has been used to map the local heating augmentation of scaled idealized cavities at conditions simulating the windward surface of the Shuttle Orbiter Columbia during flight STS-107. Two experiments initiated in support of the Columbia Accident Investigation were conducted in the Langley 20-Inch Mach 6 Tunnel. Generally, the first test series evaluated open (length-to-depth less than 10) rectangular cavity geometries proposed as possible damage scenarios resulting from foam and ice impact during launch at several discrete locations on the vehicle windward surface, though some closed (length-to-depth greater than 13) geometries were briefly examined. The second test series was designed to parametrically evaluate heating augmentation in closed rectangular cavities. The tests were conducted under laminar cavity entry conditions over a range of local boundary layer edge-flow parameters typical of re-entry. Cavity design parameters were developed using laminar computational predictions, while the experimental boundary layer state conditions were inferred from the heating measurements. An analysis of the aeroheating caused by cavities allowed exclusion of non-breeching damage from the possible loss scenarios being considered during the investigation.

Everhart, Joel L.↗

NASA NTRS1979

Low-velocity impact craters in ice and ice-saturated sand with implications for Martian crater count ages

The paper reports on a series of low-velocity impact experiments performed in ice and ice-saturated sand. It is found that crater diameters in ice-saturated sand were about 2 times larger than in the same energy and velocity range in competent blocks of granite, basalt and cement, while craters in ice were 3 times larger. It is shown that if this dependence of crater size on strength persists to large hypervelocity impact craters, then surface of geologic units composed of ice or ice-saturated soil would have greater crater count ages than rocky surfaces with identical influx histories. Among the conclusions are that Martian impact crater energy versus diameter scaling may also be a function of latitude.

Croft, S. K.↗

NASA NTRS2011

Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production

Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

Kurtz, N. T.↗

NASA NTRS2000

The Impact of Sea Ice Concentration Accuracies on Climate Model Simulations with the GISS GCM

The Goddard Institute for Space Studies global climate model (GISS GCM) is used to examine the sensitivity of the simulated climate to sea ice concentration specifications in the type of simulation done in the Atmospheric Modeling Intercomparison Project (AMIP), with specified oceanic boundary conditions. Results show that sea ice concentration uncertainties of +/- 7% can affect simulated regional temperatures by more than 6 C, and biases in sea ice concentrations of +7% and -7% alter simulated annually averaged global surface air temperatures by -0.10 C and +0.17 C, respectively, over those in the control simulation. The resulting 0.27 C difference in simulated annual global surface air temperatures is reduced by a third, to 0.18 C, when considering instead biases of +4% and -4%. More broadly, least-squares fits through the temperature results of 17 simulations with ice concentration input changes ranging from increases of 50% versus the control simulation to decreases of 50% yield a yearly average global impact of 0.0107 C warming for every 1% ice concentration decrease, i.e., 1.07 C warming for the full +50% to -50% range. Regionally and on a monthly average basis, the differences can be far greater, especially in the polar regions, where wintertime contrasts between the +50% and -50% cases can exceed 30 C. However, few statistically significant effects are found outside the polar latitudes, and temperature effects over the non-polar oceans tend to be under 1 C, due in part to the specification of an unvarying annual cycle of sea surface temperatures. The +/- 7% and 14% results provide bounds on the impact (on GISS GCM simulations making use of satellite data) of satellite-derived ice concentration inaccuracies, +/- 7% being the current estimated average accuracy of satellite retrievals and +/- 4% being the anticipated improved average accuracy for upcoming satellite instruments. Results show that the impact on simulated temperatures of imposed ice concentration changes is least in summer, encouragingly the same season in which the satellite accuracies are thought to be worst. Hence the impact of satellite inaccuracies is probably less than the use of an annually averaged satellite inaccuracy would suggest.

Parkinson, Claire L.↗

NASA NTRS2004

Hopane Biomarkers Traced from Bedrock to Recent Sediments and Ice at the Haughton Impact Structure, Devon Island: Implications for the Search for Biomarkers on Mars

Hopanoid biomarkers have been successsfully traced from Palaeozoic target bedrock to Miocene impact-processed rocks, post-impact sediments, and Qu aternary ice at the Haughton impact Structure, Devon Island, High Arctic, suggesting that similar biomarkers and techniques to detect them might provide a promising strategy in the search for biomarkers in rocks, sediments and ice on Mars.

Parnell, J.↗

NASA NTRS2014

A Range Correction for Icesat and Its Potential Impact on Ice-sheet Mass Balance Studies

We report on a previously undocumented range error in NASA's Ice, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or 'G-C'offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods less than1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of −0.92 to −1.90 cm yr(exp −1), depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne ice shelves we show that (1) the G-C offset introduces significant biases in ice-shelf mass balance estimates, and (2) the mass balance bias can vary between regions because of different temporal samplings of ICESat.We can reproduce the effect of the G-C offset over these two ice shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on ice-sheet mass balance estimates.

mass balance↗

NASA NTRS2020

Clouds Damp the Impacts of Polar Sea Ice Loss

The amount of solar energy absorbed by the Earth is believed to strongly depend on clouds, due to their ability to scatter and reflect part of solar energy back to space. Here, we investigate this relationship using satellite data and 32 climate models, showing that this relationship holds everywhere except over polar seas, where an increased reflection by clouds corresponds to an increase in absorbed solar radiation at the surface. We resolve this paradox by quantifying a strong correlation between clouds and sea-ice extent. An increase in absorbed solar radiation, when sea ice retreats, leads to an increase in cloud cover/thickness and associated reflection to space. This interplay between clouds and sea ice reduces by half the increase of net radiation at the surface that follows the sea-ice retreat, therefore damping the impact of polar sea ice loss. We further highlight how this process is mis-represented in some climate models.

Ramdane Alkama↗

NASA NTRS1988

Collisional properties of ice spheres at low impact velocities

The results of experimental studies on the impact properties of water ice are discussed. Stable temperatures of 85 K and pressures as low as 10 to the -5th Torr were achieved using a new apparatus consisting of a compound disk pendulum and a stainless steel, temperature-controlled cryostat. The coefficient of restitution as a function of velocity was obtained for ice spheres with four different radii of curvature and with a variety of surface conditions. These data can be well fitted by an exponetial law epsilon of given form for most measurements. Surface conditions can drastically alter the resulting value of epsilon, however. In particular, the presence of frost or a roughened contact surface can lower epsilon at a given velocity by 10-30 percent from that of a smooth sphere. It is shown how the presence of frost can change the velocity behavior of epsilon from an exponential to a power-law form. The applications of the results to the dynamics of Saturn's rings are discussed.

Hatzes, Artie P.↗

NASA NTRS2024

A Multi‐Probe Automated Classification of Ice Crystal Habits During the IMPACTS Campaign

Although all ice crystals are unique, many can be grouped together by shape or habit, with members of a habit class sharing similar representations of properties such as fall velocity and growth rate. A decision tree algorithm designed to be adaptable to any particle imaging probe, thus enabling the creation of habit size distributions over a size range larger than that of any probe on its own, is used to classify ice crystals imaged by three airborne cloud probes in mid-latitude winter cyclones during the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign. Crystals are sorted into seven habit classes based on their morphological properties: sphere, column/needle, plate, graupel, dendrite, aggregate, and irregular. Although adaptability was its primary goal, the algorithm was found to be moderately skillful for identifying idealized habit images. Quantitative tests of the algorithm’s adaptability displayed mixed results, as Two-Dimensional Stereo Probe (2DS) classifications showed moderate correlation with Particle Habit Imaging and Polar Scattering Probe (PHIPS) classifications, but only weak correlation with High Volume Precipitation Spectrometer (HVPS) classifications. The algorithm was applied to random sets of images from each probe in a case study of a mesoscale snow band sampled on 7 February 2020. In the case study, qualitative analysis of particle images revealed general agreement on classifications among the probes, supporting the algorithm’s applicability to multiple cloud probes. Most classifications appeared correct upon manual inspection, suggesting that in practical use, the algorithm is reasonably able to classify non-idealized images.

Julian Schima↗

NASA NTRS2017

Radiative Impacts of Further Arctic Sea Ice Melt: Using past Observations to Inform Future Climate Impacts

The Arctic region has seen dramatic changes over the past several decades, from polar amplification of global temperature rise to ecosystem changes to the decline of the sea ice. While there has been much speculation as to when the world will see an ice-free Arctic, the radiative impacts of an eventual disappearance of the Arctic sea ice are likely to be significant regardless of the timing. Using CERES radiation and microwave satellite sea ice data, Pistone et al (2014) estimated the radiative forcing due to albedo changes associated with the Arctic sea ice retreat over the 30 years of the satellite data record. In this study, we found that the Arctic Ocean saw a decrease in all-sky albedo of 4% (from 52% to 48%), for an estimated increase in solar heating of 6.4 W/m(exp 2) between 1979 and 2011, or 0.21 W/m(exp 2) when averaged over the globe. This value is substantial--approximately 25% as large as the forcing due to the change in CO2 during the same period. Here we update and expand upon this previous work and use the CERES broadband shortwave observations to explore the radiative impacts of a transition to completely ice-free Arctic Ocean. We estimate the annually-averaged Arctic Ocean planetary albedo under ice-free and cloud-free conditions to be 14% over the region, or approximately 25% lower in absolute terms than the Arctic Ocean cloud-free albedo in 1979. However, the question of all-sky conditions (i.e. including the effects of clouds) introduces a new level of complexity. We explore several cloud scenarios and the resultant impact on albedo. In each of these cases, the estimated forcing is not uniformly distributed throughout the year. We describe the relative contributions of ice loss by month as well as the spatial distributions of the resulting changes in absorbed solar energy. The seasonal timing and location—in addition to magnitude—of the altered solar absorption may have significant implications for atmospheric and ocean dynamics in the Arctic and at lower latitudes; this observationally-based estimate of the large-scale characteristics of an ice-free Arctic thus provides a valuable tool to complement and validate model-based assessments of future climate.

Pistone, K.↗