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Klaus, David M.

Overview
Works: 9 works in 9 publications in 1 language and 398 library holdings
Publication Timeline
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Publications about David M Klaus
Publications by David M Klaus
Most widely held works by David M Klaus
Assessing feasibility of electrochromic space suit radiators for reducing extravehicular activity water consumption by Jonathan Glen Metts( file )
1 edition published in 2010 in English and held by 2 libraries worldwide
Water consumption for space suit thermal control is a limiting factor on long-term space exploration missions. A concept is proposed for an integrated, flexible suit radiator using infrared electrochromic materials for modulated heat rejection from the suit. Properties of electrochromic materials, the structure of electrochromic devices, and relevant heat transfer processes are presented as background information. Analytical methods are employed to bound theoretical performance and determine required emissivity ranges for lunar surface operations. Case studies are presented incorporating Apollo program and Advanced Walkback Test metabolic and environmental data to estimate sublimator water consumption and hypothetical water savings with the electrochromic radiator. Concepts are presented and analyzed for integrating an electrochromic radiator with existing and future space suit designs. A preliminary systems-level trade analysis is performed with the Equivalent System Mass metric used to compare this technology with the legacy sublimator and other extravehicular activity cooling technologies in development. Experimental objectives, procedures, and results are presented for both bench-top and thermal vacuum testing of electrochromic radiator materials
Characterization and measurement standardization of lunar dust abrasion for spacecraft design and operations by Ryan Lauren Kobrick( file )
1 edition published in 2010 in English and held by 2 libraries worldwide
A non-dimensional Abrasion Index is introduced to help quantify overall system wear. The suggested index is a function of dust interaction modes and variable dust concentration zones on the Moon. This includes level of risk for the material, part or system; the hardness of the mineralogy; severity of abrasion; and the frequency of dust particle interactions. Recommendations for mission planning and spacecraft design are provided in terms of material selection assessment for minimizing detrimental abrasive wear and strategic dust mitigation methods
Characterization of dynamic thermal control schemes and heat transfer pathways for incorporating variable emissivity electrochromic materials into a space suit heat rejection system by Christopher James Massina( file )
1 edition published in 2016 in English and held by 1 library worldwide
The feasibility of conducting long duration human spaceflight missions is largely dependent on the provision of consumables such as oxygen, water, and food. In addition to meeting crew metabolic needs, water sublimation has long served as the primary heat rejection mechanism in space suits during extravehicular activity (EVA). During a single eight hour EVA, approximately 3.6 kg (8 lbm) of water is lost from the current suit. Reducing the amount of expended water during EVA is a long standing goal of space suit life support systems designers; but to date, no alternate thermal control mechanism has demonstrated the ability to completely eliminate the loss. One proposed concept is to convert the majority of a space suit's surface area into a radiator such that the local environment can be used as a radiative thermal sink for rejecting heat without mass loss. Due to natural variations in both internal (metabolic) loads and external (environmental) sink temperatures, radiative transport must be actively modulated in order to maintain an acceptable thermal balance. Here, variable emissivity electrochromic devices are examined as the primary mechanism for enabling variable heat rejection. This dissertation focuses on theoretical and empirical evaluations performed to determine the feasibility of using a full suit, variable emissivity radiator architecture for space suit thermal control. Operational envelopes are described that show where a given environment and/or metabolic load combination may or may not be supported by the evaluated thermal architecture. Key integration considerations and guidelines include determining allowable thermal environments, defining skin-to-radiator heat transfer properties, and evaluating required electrochromic performance properties. Analysis also considered the impacts of dynamic environmental changes and the architecture's extensibility to EVA on the Martian surface. At the conclusion of this work, the full suit, variable emissivity radiator architecture is considered to be at a technology readiness level of 3/4, indicating that analytical proof-of-concept and component level validation in a laboratory environment have been completed. While this is not a numeric increase from previous investigations, these contributions are a significant iteration within those levels. These results improve the understanding of the capabilities provided by the full suit, variable emissivity architecture
Phenotypic and gene expression responses of E. coli to antibiotics during spaceflight by Luis Zea( file )
1 edition published in 2015 in English and held by 1 library worldwide
Bacterial susceptibility to antibiotics has been shown in vitro to be reduced during spaceflight; however, the underlying mechanisms responsible for this outcome are not fully understood. In particular, it is not yet clear whether this observed response is due to increased drug resistance (a microbial defense response) or decreased drug efficacy (a microgravity biophysical mass transport effect). To gain insight into the differentiation between these two potential causes, an investigation was undertaken onboard the International Space Station (ISS) in 2014 termed Antibiotic Effectiveness in Space-1 (AES-1). For this purpose, E. coli was challenged with two antibiotics, Gentamicin Sulfate and Colistin Sulfate, at concentrations higher than those needed to inhibit growth on Earth. Phenotypic parameters (cell size, cell envelope thickness, population density and lag phase duration) and gene expression were compared between the spaceflight samples and ground controls cultured in varying levels of drug concentration. It was observed that flight samples proliferated in antibiotic concentrations that were inhibitory on Earth, growing on average to a 13-fold greater concentration than matched 1g controls. Furthermore, at the highest drug concentrations in space, E. coli cells were observed to aggregate into visible clusters. In spaceflight, cell size was significantly reduced, translating to a decrease in cell surface area to about one half of the ground controls. Smaller cell surface area can in turn proportionally reduce the rate of antibiotic molecules reaching the cell. Additionally, it was observed that genes -- in some cases more than 2000 -- were overexpressed in space with respect to ground controls. Up-regulated genes include poxB, which helps catabolize glucose into organic acids that alter acidity around and inside the cell, and the gadABC family genes, which confer resistance to extreme acid conditions. The next step is to characterize the mechanisms behind the observed gene expression, its implications, and most importantly, how this knowledge can help prevent the acquisition and spread of antibiotic resistance in pathogens on Earth
A systematic process for assessing human spacecraft conceptual designs in terms of relative safety and operational characteristics by Kevin Paul Higdon( file )
1 edition published in 2012 in English and held by 1 library worldwide
This work establishes a definition for a minimum functional design and is the first to group the fundamental mass parameters of a human spacecraft in the categories of Physics, Physiology, Safety, and Operability. The minimum functional baseline configuration described in this work is different from previous approaches because it eliminates the bias toward a minimum set of requirements. The amount of Safety in the spacecraft is the mass dedicated to safety through similar or dissimilar redundancy, safety components, margins, and dispersions. The amount of Operability in the spacecraft is the mass used to perform mission objectives and make functions easier or efficient. Because human spacecraft are highly coupled systems, the introduction of mass in one subsystem has downstream effects on other subsystems that are not easily recognized by designers and the use of rapidly reconfigurable prototypes allows designers and multidisciplinary teams to utilize Boundary Objects as a means of communication for maturing designs. The mass addition process coupled with the minimum functionality approach creates a tradespace of spacecraft configurations and provides designers with an overall view of how various levels of Safety or Operability will affect the overall spacecraft mass. The decisions made in the conceptual design phase are critical to the success of the program and uncertainty can lead to unnecessary redesign in later phases. The previous methods can be combined into a conceptual design process that couples easily with typical industry approaches to human spacecraft development. The use of minimum functionality as a precursor to more conventional approaches allows the spacecraft configuration to take shape before detailed CAD and higher fidelity analyses
Development and application of spaceflight performance shaping factors for human reliability analysis by Jennifer Mindock( file )
1 edition published in 2012 in English and held by 1 library worldwide
The Bayesian Network is discussed as a quantification approach allowing relationships between factors, in addition to the factor relationships to performance outcomes, to be modeled. A method for determining a network structure was developed for domains such as human spaceflight, in which a global set of data for analysis is not available. This method applied the Analytic Hierarchy Process, and causal latency concepts from the Human Factors Analysis and Classification System in a novel way to guide choices for modeling the dominant set of factors and relationships in a simplified Bayesian Network structure. In addition, an approach for modeling the factors as statistical variables in a Bayesian Network making use of existing design requirements and human performance data is discussed. Applications of this modeling approach in terms of requirement completeness assessment and identification of future research needs are also described. Finally, an illustrative quantified Bayesian Network for the spaceflight domain is given, built on the factor identification and structure development work throughout the thesis. Its use in a Human Reliability Analysis is demonstrated
Validation of proposed metrics for two-body abrasion scratch test analysis standards by Ryan L Kobrick( file )
1 edition published in 2011 in English and held by 0 libraries worldwide
Buoyancy-Driven Fluid Flow Generated by Bacterial Metabolism and its Proposed Relationship to Increased Bacterial Growth in Space ( file )
1 edition published in 2005 in English and held by 0 libraries worldwide
Previous investigations have reported that bacterial growth increases in space flight; however, the underlying physical mechanisms responsible for these changes have not been fully determined. As bacteria consume nutrients, they excrete by-products whose presence can influence the onset of exponential growth and affect final cell population density. It is assumed that these metabolic processes create a reduced-density fluid zone and/or a solute gradient around each cell. On Earth, this density difference may result in local buoyancy-driven convection of the excreted by-products. The absence of convection and sedimentation in the low-gravity space flight environment, however, can be expected to alter the fluid dynamics surrounding the cells by limiting transport to diffusion only. Based on this biophysical model, it was hypothesized that acceleration affects the lag phase duration and final cell concentration of suspended bacterial cultures in a predictable, non-linear manner, due to the resultant changes incurred in the extracellular fluid composition. Eight experiments at various levels of acceleration consistently supported this hypothesis, resulting in predictable growth kinetics. In additional experiments, macroscopic plumes of fluid were observed and analyzed rising from metabolizing bacterial cultures. If similar fluid dynamics were found to occur on a microscopic level, it would help explain how acceleration affects bacterial growth kinetics
Defining an abrasion index for lunar surface systems as a function of dust interaction modes and variable concentration zones by Ryan L Kobrick( file )
1 edition published in 2010 in English and held by 0 libraries worldwide
 
Languages
English (9)
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