137091 research outputs found
Sort by
The Gadgets in the Library
No full textInterview portion of Lost in the Stacks, episode 662. Features interview with Cierra Cooper, Public Services Associate at the Georgia Tech Library, discussing the equipment lending (or 'gadget') service that she leads. She discusses what the gadget service is, what it has, and how it is used on campus by the students.Interview portion of Lost in the Stacks, episode 662. Features interview with Cierra Cooper, Public Services Associate at the Georgia Tech Library, discussing the equipment lending (or 'gadget') service that she leads. She discusses what the gadget service is, what it has, and how it is used on campus by the students
Feasibility study of a ferrofluid droplet radiator for High-Power CubeSat Applications
No full textHigh-power CubeSats are attracting substantial attention due to their ability to offer augmented capabilities comparable to larger satellites, but with significantly lower cost and mass. As their applications expand, the demand for high-power components also increases, making thermal management essential to the success of the mission. Current power dissipation solutions, such as body-mounted radiators, are limited by the available surface area, rendering them less effective for high-power missions. Recent comparative analysis indicates that state-of-the-art deployable radiators can reject up to 200 W of heat. However, new solutions may soon be needed to overcome this limitation and support high-power missions. This work presents the SmallSat ferrofluid droplet radiator (FDR) as a solution for high-power missions, that offers increased surface area with reduced mass. The FDR operates by ejecting a layer of high-temperature droplets from a micro-meter injector to radiate heat into space. Droplets are then collected by a neodymium magnet positioned at the tip of a deployable boom. A redundant set of pumps is incorporated to maintain the continuous operation of the closed-loop thermodynamic cycle. The FDR combines the heat transport and rejection processes into one system, eliminating the need for the traditional thermal path. While earlier studies have demonstrated the feasibility of this technology in handling significant heat levels for larger satellites, the applicability of this technology to SmallSats heat rejection remains unexplored.
This thesis focuses on studying the feasibility of the FDR in the context of high-power CubeSat communication. Communication systems are an essential component of every space mission. However, as power requirements become more stringent, the operation of high-bandwidth telecommunication systems will be constrained by the design of the thermal control system and the environmental challenges. Preliminary results from parametric analysis and design optimization indicate the potential of the FDR to dissipate heat in the range of 100 to 500 W. Additionally, it addresses key challenges of fluid behavior in space and previously encountered issues with the liquid droplet radiators. Further experimental and simulation studies are necessary to investigate the radiative behavior of the radiator and assess its performance under extreme conditions in low Earth orbit. Following this analysis, an optimization of the collector will be conducted. The ultimate goal is to enable small platforms like CubeSats to undertake high-power missions and meet the growing demand for high-quality, faster data transmission rates.M.S.Aerospace Engineerin
Real-Time Stochastic Terrain Mapping and Processing for Autonomous Safe Landing
No full textOnboard terrain sensing and mapping for safe planetary landings often suffer from missed hazardous features, e.g., small rocks, due to the large observational range and the limited resolution of the obtained terrain data. To this end, this paper develops a novel real-time stochastic terrain mapping algorithm that accounts for topographic uncertainty between the sampled points, or the uncertainty due to the sparse 3D terrain measurements. We introduce a Gaussian digital elevation map that is efficiently constructed using the combination of Delauney triangulation and local Gaussian process regression. The geometric investigation of the lander-terrain interaction is exploited to efficiently evaluate the marginally conservative local slope and roughness while avoiding the costly computation of the local plane. The conservativeness is proved in the paper. The developed real-time uncertainty quantification pipeline enables stochastic landing safety evaluation under challenging operational conditions, such as a large observational range or limited sensor capability, which is a critical stepping stone for the development of predictive guidance algorithms for safe autonomous planetary landing. Detailed reviews on background and related works are also presented
Modeling the Performance Characteristics of Aluminum Fin-Tube Heat Exchangers for Residential Space Cooling
No full textEnergy consumption for space cooling is projected to more than double to ~6200 TWh by the year 2050 as the adoption of air conditioning technologies increases drastically globally. Condenser-type heat exchangers (HXs), particularly air-coupled condensers, are vital components in such thermodynamic systems where heat is rejected to the outdoor environment. A major drawback of air-coupled HXs is the large surface area and volume required due to the insulative properties of air as a heat transfer fluid, which necessitates the use of finned tubes. Aluminum alloys are commonly used as fin stock owing to their high thermal conductivity and corrosion resistance, while serving as sacrificial anodes to extend the lifespan of HVAC systems. Another benefit of aluminum is its recyclability, which offsets the greenhouse gas emissions and costs associated with bauxite refining. Additionally, the composition, temper, coating, gauge, and joining method can significantly impact properties. This research evaluates the impact of introducing novel aluminum alloys (with higher recycled content) on the thermohydraulic performance of condenser heat exchangers.
A steady-state model is developed using empirical correlations to represent air-coupled condenser HXs. The heat duty and pressure drop are evaluated for a finned tube bank in superheated vapor, film condensing, and subcooled liquid flow regimes for different refrigerants (e.g., R32, R1234yf, R410a), all in crossflow with air. Parametric analyses are conducted on the fin thickness, pitch, thermal conductivity, and geometry for a range of typical operating conditions and a selection of condenser designs. Thermophysical properties of the aluminum alloys are characterized using laser flash analysis (LFA) and differential scanning calorimetry (DSC) to highlight differences between conventional and novel materials, and the resulting effects on HX performance. Overall, this study outlines key considerations for the adoption of more sustainable aluminum alloys in space cooling technologies.M.S.Mechanical Engineerin
(De)central planning approaches for asset sharing between multiple connected fleets for airside baggage transport
No full textThe logistics sector faces big challenges in terms of ambitious sustainability targets, strong emphasis on security of supply and dealing with scarcity (in terms of physical infrastructure, energy and labor force). This requires a system change in logistics by "doing more with less” through sharing assets in the freight and transport industry in open connected logistics networks. Essential elements for this are trusted multilateral horizontal and vertical collaboration, decentral coordination and decentral data sharing. TNO developed a roadmap to develop solutions with increasing complexity in terms of requirements. This paper describes approach and results of decentral planning algorithms for a multi-fleet single party situation (full asset sharing, limited collaboration within a single company). The impact of central and decentral approaches and single fleet and multi-fleet planning are shown for a use case of airside baggage transport at Schiphol Amsterdam Airport
Parametric Carrier Sizing for Pressurized Rover Resupply Operations
No full textAIAA ASCEND 2025, Las Vegas, NVThe Artemis program aims to establish a lunar base near the south pole of the Moon, with plans that potentially include a surface habitat and other surface elements, such as a pressurized rover. To ensure continuous operation, these elements require regular cargo resupply that includes consumables necessary for mission success that are not installed as part of the vehicle. Resupply cargo will be delivered via specialized logistic carrier modules, whose design can benefit greatly from understanding the impact of high-level design alternatives. This study introduces a parametric framework for sizing logistic carrier modules, with emphasis on the impact of these high-level design choices. The framework outlines structural sizing requirements to accommodate resupply consumables, along with the thermal and power subsystems needed to maintain temperature stability and supply power during independent carrier operation. Trade-offs between larger, integrated carriers, capable of resupplying both the habitat and a
pressurized rover, and smaller specialized carriers for pressurized rover resupply are evaluated. The framework’s capabilities are then demonstrated through sensitivity analysis and design space exploration for a use case mission
Effects of Defects, Flexibility, and Ozone on Stability of Metal Organic Frameworks
No full textMetal−organic framework (MOF) materials are nanoporous materials whose crystalline character has made them attractive targets for synthesis of new materials and potential use in a diverse set of applications. To be commercially viable, MOFs should possess water stability because many industrial processes like gas separation and storage involve some amount of water. In this dissertation, to identify the high performing MOFs for Oxygen-Helium separations, we begin with high throughput computational screening of several thousand MOFs followed by water stability assessment of top performing MOFs for practical application. Most computational studies of MOFs consider these materials as defect free. Defects are ubiquitous in the real crystal structures of MOFs and can play strong roles in MOF water stability and subsequent degradation. Unfortunately, direct experimental detection and characterization of defects in MOFs are very challenging. We introduce a molecular simulation based approach that utilizes differences between experimentally observed and computationally predicted water stabilities of MOFs to deduce information on the presence of point defects in real materials. Further we investigate the degradation of amine functionalized adsorbents that play an important role in direct air capture (DAC) of CO2. Trace amount of atmospheric aggressive oxidants such as ozone can potentially degrade the adsorbent structure by reacting with amine sites and C-C double bonds. We use quantum chemistry calculations to examine the potential degradation of a prototypical amine-based adsorbent by ozone at a mechanistic level. Lastly, this dissertation illustrates the potential implications of diurnal variations of ambient conditions for the operation and optimization of a DAC process with process-level calculations for a specific adsorption-based process using amine-rich adsorbents. This approach highlights the necessity of understanding and adapting to real-world conditions for the successful deployment of DAC technology.Ph.D.Chemical and Biomolecular Engineerin
Development of Model Cells for Characterizing Electro-Catalysts in Solid Oxide Cells
No full textSolid oxide fuel cells (SOFCs) are a type of fuel cell technology that has offers several outstanding characteristics including high efficiency, reversible operation, and mechanical robustness. However, their development is hindered in large part by the relatively slow kinetics on the air electrode surface. To address these challenges, considerable research is being directed towards uncovering high-performance catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) pathways.
Conventional cells for operational testing have porous electrodes that maximize the available surface area for these reactions to take place. Catalyst candidate materials applied to these electrodes ideally are dispersed in a thin and uniform coating over the porous electrode backbone. This microstructure yields the best cell performance, but it can be difficult to characterize the surface chemistry due to the thinness of the catalyst layer and how a majority of the catalyst material is blocked from direct exposure of techniques such as Raman spectroscopy and XPS. Model cells are a cell design where one of the porous electrodes is replaced with a thin and fully dense electrode that can then be coated with a catalyst layer. While the electrochemical performance of such a cell may be lower, the advantage of this design is that the reaction space is confined to well-defined plane at the surface of the cell which is easily probed.
In this work, I outline the important criteria for a model cell design that would be suitable for use in screening promising catalyst material compositions for both performance enhancement as well as chemical stability in typical SOFC operating conditions. Furthermore, I discuss the detailed fabrication procedure used to produce said cells in a repeatable manner and in sufficient quantity to carry out catalyst screening. I then present some specific findings that demonstrate the capability of these model cells in enabling catalyst investigation that can guide future rational design of promising catalyst materials.M.S.Materials Science and Engineerin
Using Changes in Revealed Impedance to Assess the Potential Benefits of New Cycling Infrastructure Using BikewaySim
No full textThis research proposes a framework for assessing the impacts of new and existing cycling facilities using minimum cycling impedance routing. Cycling impedance represents the relative difficulty of cycling and considers travel time, exposure to automobiles, hills, and the provision of cycling infrastructure. With map-matched cycling GPS traces from CycleAtlanta, this research calibrates cycling impedance functions using particle swarm optimization. The calibrated impedance functions are applied to a 250-square-mile Metro Atlanta study area network to assess the impact of 117 planned bicycle facilities on 3.6 million trips from the Atlanta Regional Commission Activity-Based Model. Five metrics, trip impedance reduction, percent detour, change in link betweenness centrality, impedance reduction contribution, and bikesheds highlight the impedance reduction impacts of new cycling infrastructure. Planners, engineers, and advocacy groups can utilize the framework to evaluate proposed cycling infrastructure and prioritize projects that stand to reduce the most cycling impedance. As new cycling trace data and network data become available, researchers can update the impedance functions to reflect the behavior of current cyclists and develop new impedance factors.Ph.D.Civil Engineerin