Modeling of an Atmospheric-Boundary-Layer Profile in Support of Experiments in the NASA Langley Transonic Dynamics Tunnel

This paper presents the results of the Computational Fluid Dynamics (CFD) analyses to model two atmospheric-boundary-layer (ABL) profiles inside the NASA Langley Research Center Transonic Dynamics Tunnel (TDT). The CFD models include tunnel walls and all additional hardware needed to simulate the ABL profiles. This hardware includes Irwin spires and floor-mounted roughness elements. The numerical simulations show that the application of higher-fidelity numerical methods is necessary to compute boundary-layer and turbulenceintensity profiles that match experimental data. The ABL profiles are computed both inside the numerical model of the TDT and in a classical free-air model. Both Unsteady Reynolds Averaged Navier-Stokes (URANS) with Spalart-Allmaras (SA) turbulence model and Modified Delayed Detached Eddy (MDDES) simulation methods are used. The results show that the MDDES-simulation results match the experimental data very well while URANS-SA does not. The results also show that the wind-tunnel walls have a significant effect on ABL prediction

Advanced Generalized Predictive Control and Its Application to Tiltrotor Aircraft for Stability Augmentation and Vibration Reduction

The goals of this research were to restore generalized predictive control (GPC) capability at NASA and within the community, to better understand GPC and its performance relative to other options, and to improve upon the capability of GPC. Unique to this research is the comparison of GPC with other control options including PID controllers, optimal control theory, and other versions of the similar AutoRegressive moving average model with eXogenous inputs (ARX) models. Similar to GPC, ARX models use an experimentally acquired system identification to characterize the input/output relationship between controls and response measurements. Because this relationship is determined from acquired data, minimal knowledge of the system behavior is required to employ ARX or GPC controllers. As a result of these comparisons, it was observed that GPC is typically the best performing control option and typically has better gain and phase margins when properly employed. Also unique to this dissertation is the use of orthogonal multisine excitation as the command inputs for GPC application rather than the typical distinguishable random noise. Finally, the concept of Advanced GPC (AGPC) is introduced as a part of this dissertation work. AGPC is a self-adapting algorithm that improves traditional GPC when conditions change from those used to derive the system identification. AGPC is also better performing than traditional GPC in some cases even when the conditions do not change from those used to acquire the system identification. Application of AGPC requires the monitoring of performance figures of merit, and the application of control dither when the metrics indicate that the controls are not distinguishable enough or the response of the system is inadequate to properly characterize the input/output relationship. Finally, for experimental application of GPC and AGPC, techniques were introduced to increase model safety and include features such as a magnitude ramp rate when closing the control loop, master gain values to reduce control or dither authority, continual computation of figures of merit, the ability to gradually change from one control algorithm to another, and visualization of control commands prior to closing the control loop and/or switching from one control algorithm to another

Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles

Launch vehicles are exposed to ground winds during rollout and on the launch pad that can induce static and dynamic loads. Of particular concern are the dynamic loads caused by vortex shedding from nearly-cylindrical structures. When the frequency of vortex shedding nears that of a lowly-damped structural mode, the dynamic loads can be more than an order of magnitude greater than mean drag loads. Accurately predicting vehicle response to vortex shedding during the design and analysis cycles is difficult and typically exceeds the practical capabilities of modern computational fluid dynamics codes. Therefore, mitigating the ground wind loads risk typically requires wind-tunnel tests of dynamically-scaled models that are time consuming and expensive to conduct. In recent years, NASA has developed a ground wind loads analysis tool for launch vehicles to fill this analytical capability gap in order to provide predictions for prelaunch static and dynamic loads. This paper includes a background of the ground wind loads problem and the current state-of-the-art. It then discusses the history and significance of the analysis tool and the methodology used to develop it. Finally, results of the analysis tool are compared to wind-tunnel and full-scale data of various geometries and Reynolds numbers

Compact Vibration Damper

A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement

Aerodynamically-Actuated Radical Shape-Change Concept

Aerodynamically-actuated radical shape change (AARSC) is a novel concept that enables flight vehicles to conduct a mission profile containing radically different flight regimes while possibly mitigating the typical penalties incurred by radical geometric change. Weight penalties are mitigated by utilizing a primary flight control to generate aerodynamic loads that then drive a shape-change actuation. The flight mission profile used to analyze the AARSC concept is that of a transport aircraft that cruises at a lower altitude than typical transports. Based upon a preliminary analysis, substantial fuel savings are realized for mission ranges below 2000 NM by comparison to a state-of-the-art baseline, with an increasing impact as mission range is reduced. The predicted savings are so significant at short-haul ranges that the shape-change concept rivals the fuel-burn performance of turboprop aircraft while completing missions in less time than typical jet aircraft. Lower-altitude cruise has also been sought after in recent years for environmental benefits, however, the performance penalty to conventional aircraft was prohibitive. AARSC may enable the opportunity to realize the environmental benefits of lower-altitude emissions coupled with mission fuel savings. The findings of this study also reveal that the AARSC concept appears to be controllable, turbulence susceptibility is likely not an issue, and the shape change concept appears to be mechanically and aerodynamically feasible

Wind Tunnel Investigation of Ground Wind Loads for Ares Launch Vehicle

A three year program was conducted at the NASA Langley Research Center (LaRC) Aeroelasticity Branch (AB) and Transonic Dynamics Tunnel (TDT) with the primary objective to acquire scaled steady and dynamic ground-wind loads (GWL) wind-tunnel data for rollout, on-pad stay, and on-pad launch configurations for the Ares I-X Flight Test Vehicle (FTV). The experimental effort was conducted to obtain an understanding of the coupling of aerodynamic and structural characteristics that can result in large sustained wind-induced oscillations (WIO) on such a tall and slender launch vehicle and to generate a unique database for development and evaluation of analytical methods for predicting steady and dynamic GWL, especially those caused by vortex shedding, and resulting in significant WIO. This paper summarizes the wind-tunnel test program that employed two dynamically-aeroelastically scaled GWL models based on the Ares I-X Flight Test Vehicle. The first model tested, the GWL Checkout Model (CM), was a relatively simple model with a secondary objective of restoration and development of processes and methods for design, fabrication, testing, and data analysis of a representative ground wind loads model. In addition, parametric variations in surface roughness, Reynolds number, and protuberances (on/off) were investigated to determine effects on GWL characteristics. The second windtunnel model, the Ares I-X GWL Model, was significantly more complex and representative of the Ares I-X FTV and included the addition of simplified rigid geometrically-scaled models of the Kennedy Space Center (KSC) Mobile Launch Platform (MLP) and Launch Complex 39B primary structures. Steady and dynamic base bending moment as well as model response and steady and unsteady pressure data was acquired during the testing of both models. During wind-tunnel testing of each model, flow conditions (speed and azimuth) where significant WIO occurred, were identified and thoroughly investigated. Scaled data from the Ares I-X GWL model test was used in the determination of worst-case loads for the analysis of Ares I-X FTV design wind conditions. Finally, this paper includes a brief discussion of the limited full-scale GWL data acquired during the rollout and on-pad stay of the Ares I-X FTV that was launched from KSC on October 28, 2009

Sensitivity Analysis Method to Address User Disparities in the Analytic Hierarchy Process

Decision makers often face complex problems, which can seldom be addressed well without the use of structured analytical models. Mathematical models have been developed to streamline and facilitate decision making activities, and among these, the Analytic Hierarchy Process (AHP) constitutes one of the most utilized multi-criteria decision analysis methods. While AHP has been thoroughly researched and applied, the method still shows limitations in terms of addressing user profile disparities. A novel sensitivity analysis method based on local partial derivatives is presented here to address these limitations. This new methodology informs AHP users of which pairwise comparisons most impact the derived weights and the ranking of alternatives. The method can also be applied to decision processes that require the aggregation of results obtained by several users, as it highlights which individuals most critically impact the aggregated group results while also enabling to focus on inputs that drive the final ordering of alternatives. An aerospace design and engineering example that requires group decision making is presented to demonstrate and validate the proposed methodology

Impact of Conversion to Compact Fluorescent Lighting, and other Energy Efficient Devices, on Greenhouse Gas Emissions

Selecting appropriate boundaries for energy systems can be as challenging as it is important. In the case of household lighting systems, where does one draw these boundaries? Spatial boundaries for lighting should not be limited to the system that consumes the energy, but also consider the environment into which the energy flows and is used. Temporal boundaries must assess the energy system throughout its life cycle. These boundary choices can dramatically influence the analysis upon which energy strategies and policies are founded.This study applies these considerations to the “hot” topic of whether to ban incandescent light bulbs. Unlike existing light bulb studies, the system boundaries are expanded to include the effects incandescent light bulbs have on supplementing household space heating. Moreover, a life cycle energy analysis is performed to compare impacts of energy consumption and greenhouse gas emissions for both incandescent light bulbs and compact fluorescent light bulbs. This study focuses on Canada, which not only has ve large seasonal variations in temperature but which has announced a ban on incandescent light bulbs. After presenting a short history and description of incandescent light bulbs (ILBs) and compact fluorescent light bulbs (CFLBs), the notion that a ban on ILBs could alter (or even increase) greenhouse gas (GHG) emissions in certain regions of Canada are introduced. The study then applies a life cycle framework to the comparison of GHG emissions for the ILB and CFLB alternatives. Total GHG emissions for both alternatives are calculated and compared for the provinces of Canada and again a physical rebound effect sometimes occurs. Finally, the policy and decision making implications of the results are considered for each of these locations

Assessing Alternatives in the Systems Engineering Process: Case Study of an Earth Observing Satellite Concept

Defining design alternatives constitutes one of the critical initial steps of the systems engineering process. Once these design alternatives have been identified, assessing which alternatives best satisfy the projects objectives can prove to be challenging when dealing with complex decision frameworks. Complex systems often involve the participation of different interest groups, who have different value systems and are focused on distinct aspects of the project. For example, design alternatives might be assessed predominantly for their technical merit by one group of stakeholders, while a different group might be more inclined to assess the design alternatives primarily based on programmatic values. MESCAL (Monitoring the Evolving State of Clouds and Aerosol Layers) is an ongoing NASA / CNES (Centre National dEtudes Spatiales) joint study for an active remote sensing Earth observing satellite. Several design alternatives have been identified and the assessment of these alternatives requires consideration of a variety of factors. This paper presents the approach that was used to support a global assessment of the MESCAL design alternatives. A mapping of the interactions between mission, instrument, and science requirements was modeled to support the assessment of the trade space. In addition, a set of metrics was developed to structure the assessment that was conducted. Finally, this paper also discusses the general applicability of these metrics to other science mission concepts in the formulation phase

Arcadian't. Concept art, diseño y creación de territorios en conflicto para un juego de cartas.

[EN] Arcadian´t is a personal project whose main purpose is the concept art realization for a strategy card game. In its theoretical framework, cultural, political and philosophical aspects related to territory concept will be addressed to develop, from worldbuilding methodology; a world plunged into chaos by the culture clash between the different civilizations that inhabit it. The three-sided dispute over the territory conquest is carried out by turn-based attack and defense system to achieve victory, based on card game references such as Hearthstone, Legends of Runaterra or Magic. Artistic production deals with the creation of different characters and props, as well as the environments where card illustrations take place. In addition, card graphic design and packaging is included. The aesthetic keys are based on the pictorial synthesis and on illustration and concept art references, such as David Harrington¿s plasticity or the powerful drawings of Liana Anatolevich[ES] Arcadian´t constituye un proyecto personal cuyo objetivo principal es la realización del concept art para un juego de cartas de estrategia. En su marco teórico, se abordan aspectos culturales, políticos y filosóficos asociados al concepto de territorio para desarrollar, desde la metodología del worldbuilding, un mundo sumido en el caos provocado por el choque cultural entre las diferentes civilizaciones que lo habitan. La disputa de tres bandos por la conquista del territorio se realiza mediante un sistema de ataque y defensa por turnos, hasta alcanzar la victoria, basado en referentes como Hearthstone, Legends of Runaterra o Magic. La producción artística aborda la creación de diferentes personajes y props, así como los ambientes donde se desarrollan las ilustraciones de los naipes. También se incluye el diseño gráfico de las cartas y el packaging del juego. Las claves estéticas se basan en la síntesis pictórica y en referencias procedentes del campo de la ilustración y el concept art, como la plasticidad de David Harrington o la fuerza en el dibujo de Liana Anatolevich.Casanova Ivanco, M. (2021). Arcadian't. Concept art, diseño y creación de territorios en conflicto para un juego de cartas. Universitat Politècnica de València. http://hdl.handle.net/10251/173404TFG