Meteor Entry Characterization in the Electric Arc Shock Tube

This poster summarizes potential test opportunities in Ames' EAST facility that would benefit studies of meteor and asteroid entry into Earth's atmosphere. The Electric Arc Shock Tube (EAST) facility produces high speed (up to Mach 50) shockwaves at prescribed velocities, densities and atmospheric compositions

Shock Tube Radiation Measurements in Nitrogen

Spectrally and spatially resolved radiance has been measured in the Electric Arc Shock Tube (EAST) facility, with the aim of improving fundamental understanding of high enthalpy flows in pure nitrogen. These tests provide data to inform models used for simulations of high speed flight in nitrogen rich atmospheres, such as Earth or Titan. The experiments presented in this paper cover conditions from approximately 6 km/s to 11 km/s at an initial pressure of 0.2 Torr. A wide range of physics, with different degrees of non-equilibrium and nitrogen dissociation, are covered. The EAST data are presented in different formats for analysis and comparisons. These formats include the spectral radiance at equilibrium (where appropriate), the spatial dependence of radiance over defined wavelength ranges and the mean non-equilibrium spectral radiance (the so-called "spectral non-equilibrium metric"). All the information needed to simulate each experimental trace, including free-stream conditions, shock time of arrival (i.e. x-t) relation, and the spectral and spatial resolution functions, are provided. Equilibrium radiation calculations are shown as a reference. It is the intention of this paper to motivate code comparisons benchmarked against this data set

Radiative Heating on the After-Body of Martian Entry Vehicles

This paper presents simulations of the radiative heat flux imparted on the after-body of vehicles entering the Martian atmosphere. The radiation is dominated by CO2 bands emitting in the mid-wave infrared spectral region. This mechanism has traditionally not been considered in the design of past Mars entry vehicles. However, with recent analysis showing that the CO2 radiation can be greater than convective heating in the wake, and with several upcoming and proposed missions to Mars potentially affected, an investigation of the impact of this radiation is warranted. The focus of this paper is to provide a better understanding of the impact to aerothermal heating predictions and to provide comparisons between NASA's two main radiation codes, NEQAIR and HARA. The tangent slab approximation is shown to be overly conservative, by as much as 58 percent, for most back- shell body point locations compared to using a full angular integration method. However, due to the complexity of the wake flow, it is also shown that tangent slab does not always represent an upper limit for radiative heating. Furthermore, analysis in this paper shows that it is not possible to provide a general knock-down factor from the tangent slab results to those obtained using the more rigorous full integration method. When the radiative heating is accounted for on the after-body, the unmargined total heat flux can be as high as 14 watts per square centimeter

DSMC Shock Simulation of Saturn Entry Probe Conditions

This work describes the direct simulation Monte Carlo (DSMC) investigation of Saturn entry probe scenarios and the influence of non-equilibrium phenomena on Saturn entry conditions. The DSMC simulations coincide with rarefied hypersonic shock tube experiments of a hydrogen-helium mixture performed in the Electric Arc Shock Tube (EAST) at NASA Ames Research Center. To directly compare to the experimental results, the DSMC simulations are post-processed through the NEQAIR line-by-line radiation code. Improved collision cross-sections, inelastic collision parameters, and reaction rates are determined for a high temperature DSMC simulation of a 7-species H2-He mixture and an electronic excitation model is implemented in the DSMC code. Simulation results for 27.8 and 27.4 kms shock waves are obtained at 0.2 and 0.1 Torr respectively and compared to measured spectra in the VUV, UV, visible, and IR ranges. These results confirm the persistence of non-equilibrium for several centimeters behind the shock and the diffusion of atomic hydrogen upstream of the shock wave. Although the magnitude of the radiance did not match experiments and an ionization inductance period was not observed in the simulations, the discrepancies indicated where improvements are needed in the DSMC and NEQAIR models

Rating a Stationary Energy Storage System within a Fast Electric Vehicle Charging Station Considering User Waiting Times

The use of stationary energy storage at fast electric vehicle charging stations can buffer the energy between the electricity grid and electric vehicles, thereby reducing the maximum required grid connection power and potentially mitigating the need for grid infrastructure upgrade. In this paper, a method is presented that sizes the stationary energy storage based on an acceptable average waiting time of drivers arriving at a fast charging station. The novelty of the paper is the focus on the relationship between size of stationary energy store and user waiting time. This relationship is often ignored, however is critical to obtaining the optimum capacity of stationary energy store. An example charging station location is chosen where there are currently eight chargers capable of 120kW charging and a 500kW grid connection. It is demonstrated that the method can be used at this location to design a charging station with stationary energy storage to support future 400kW charging without upgrading the current grid connection infrastructure. With future charging, using a stationary energy storage with a capacity of 1,000kWh reduces the maximum grid power from 1,800kW to 500kW

Carbon Nanotube-Enhanced Carbon-Phenenolic Ablator Material

This viewgraph presentation reviews the use of PICA (phenolic impregnated carbon ablator) as the selected material for heat shielding for future earth return vehicles. It briefly reviews the manufacturing of PICA and the advantages for the use of heat shielding, and then explains the reason for using Carbon Nanotubes to improve strength of phenolic resin that binds carbon fibers together. It reviews the work being done to create a carbon nanotube enhanced PICA. Also shown are various micrographic images of the various PICA materials

An Overview of Research and Evaluation Designs for Dissemination and Implementation

The wide variety of dissemination and implementation designs now being used to evaluate and improve health systems and outcomes warrants review of the scope, features, and limitations of these designs

A scoping review of the use of ethnographic approaches in implementation research and recommendations for reporting

Background: Researchers have argued for the value of ethnographic approaches to implementation science (IS). The contested meanings of ethnography pose challenges and possibilities to its use in IS. The goal of this study was to identify sources of commonality and variation, and to distill a set of recommendations for reporting ethnographic approaches in IS. Methods: We included in our scoping review English-language academic journal articles meeting two criteria: (1) IS articles in the healthcare field and (2) articles that described their approach as ethnographic. In March 2019, we implemented our search criteria in four academic databases and one academic journal. Abstracts were screened for inclusion by at least two authors. We iteratively develop a codebook for full-text analysis and double-coded included articles. We summarized the findings and developed reporting recommendations through discussion. Results: Of the 210 articles whose abstracts were screened, 73 were included in full-text analysis. The number of articles increased in recent years. Ethnographic approaches were used within a wide variety of theoretical approaches and research designs. Articles primarily described using interviews and observational methods as part of their ethnographic approaches, though numerous other methods were also employed. The most cited rationales for using ethnographic approaches were to capture context-specific phenomena, understand insiders? perspective, and study complex interactions. In reporting on ethnographic approaches, we recommend that researchers provide information on researcher training and position, reflect on researchers? positionality, describe observational methods in detail, and report results from all the methods used. Conclusion: The number of IS studies using ethnography has increased in recent years. Ethnography holds great potential for contributing further to IS, particularly to studying implementation strategy mechanisms and understanding complex adaptive systems. Plain language summary: Researchers have proposed that ethnographic methods may be valuable to implementation research and practice. Ethnographic approaches have their roots in the field of anthropology, but they are now used in many fields. These approaches often involve a researcher spending time in 'real-world' settings, conducting interviews and observation to understand a group of people. That said, researchers disagree on the meaning of ethnography, which presents a challenge to its use in implementation science (IS). We searched for articles in the field of IS that described their methods as ethnographic. We then reviewed the articles, looking for similarities and differences in how and why ethnographic approaches were used. Many of these articles said they used ethnographic methods because they were interested in issues like context, research participants? views, and complex interactions. We found a large amount of variation in how ethnographic methods were used. We developed recommendations for describing ethnographic methods in a way that readers can clearly understand. We also made several observations of the value ethnographic approaches can bring to IS. Ethnographic methods may be especially useful to studying unplanned and unexpected changes that take place during implementation. These recommendations and observations could be helpful to implementation researchers wishing to use ethnographic methods

Dynamic liquefaction of shear zones in intact loess during simulated earthquake loading

The 2010-2011 Canterbury earthquake sequence in New Zealand exposed loess-mantled slopes in the area to very high levels of seismic excitation (locally measured as >2 g). Few loess slopes showed permanent local downslope deformation, and most of these showed only limited accumulated displacement. A series of innovative dynamic back pressured shear-box tests were undertaken on intact and remoulded loess samples collected from one of the recently active slopes replicating field conditions under different simplified horizontal seismic excitations. During each test, the strength reduction and excess pore water pressures generated were measured as the sample failed. Test results suggest that although dynamic liquefaction could have occurred, a key factor was likely to have been that the loess was largely unsaturated at the times of the large earthquake events. The failure of intact loess samples in the tests was complex and variable due to the highly variable geotechnical characteristics of the material. Some loess samples failed rapidly as a result of dynamic liquefaction as seismic excitation generated an increase in pore-water pressure, triggering rapid loss of strength and thus of shear resistance. Following initial failure, pore pressure dissipated with continued seismic excitation and the sample consolidated, resulting in partial shear-strength recovery. Once excess pore-water pressures had dissipated, deformation continued in a critical effective stress state with no further change in volume. Remoulded and weaker samples, however, did not liquefy, and instead immediately reduced in volume with an accompanying slower and more sustained increase in pore pressure as the sample consolidated. Thereafter excess pressures dissipated and deformation continued at a critical state. The complex behaviour explained why, despite exceptionally strong ground shaking, there was only limited displacement and lack of run-out: dynamic liquefaction was unlikely to occur in the freely draining slopes. Dynamic liquefaction however remained a plausible mechanism to explain loess failure in some of the low-angle toe slopes, where a permanent water table was present in the loess