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Daniel Guggenheim School of Aerospace Engineering

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search.filters.applied.f.advisor: Wilhite, Alan W. × End date: 2009 × Start date: 2003 ×

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Now showing 1 - 6 of 6
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A value proposition for lunar architectures utilizing on-orbit propellant refueling

2009-01-20 , Young, James Jamy

In 2004, President Bush addressed the nation and presented NASA's new vision for space exploration. This vision included the completion of the International Space Station, the retirement of the Space Shuttle, the development of a new crew exploration vehicle, and the return of humans to the moon by 2020. NASA's Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely. This architecture requires the development of two new Shuttle-derived launch vehicles, an in-space transportation vehicle, a lunar descent and landing vehicle, and a crew exploration vehicle for human transportation. The development of an in-space propellant transfer capability could greatly improve the performance, cost, mission success, and mission extensibility of the overall lunar architecture, providing a more optimal solution for future exploration missions. The work done in this thesis will analyze how this new capability could affect the current NASA lunar architecture, and will outline the value proposition of propellant refueling to NASA. A value proposition for propellant refueling will be provided to establish why an architecture that utilizes propellant refueling is better equipped to meet the goals of the Vision for Space Exploration than the current baseline design. The primary goal addressed in this research is the development of a sustainable and affordable exploration program. The value proposition will outline various refueling strategies that can be used to improve each of the architecture Figures of Merit. These include a decrease in the Life Cycle Cost of both the lunar and Mars exploration campaigns, the ability to more than double the mission payload that can be delivered to the lunar surface during cargo missions, improving the probability of successfully completing each lunar mission, decreasing the uncertainty, and therefore risk, experienced during the development process, and improving the extensibility of the exploration architecture by utilizing a greater portion of the lunar program for future crewed mission. The ability to improve these Figures of Merit provides NASA with a more valuable architecture because NASA is able to achieve a greater return on its large initial investment.

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An Innovative Methodology for Allocating Reliability and Cost in a Lunar Exploration Architecture

2007-04-05 , Young, David Anthony

In January 2005, President Bush announced the Vision for Space Exploration. This vision involved a progressive expansion of human capabilities beyond Low Earth Orbit beginning with a return to the moon no later than 2020. Current design processes utilized to meet this vision employ performance based trade studies to determine the lowest cost, highest reliability solution. The methodology implemented in this dissertation focuses on a concurrent evaluation of the performance, cost, and reliabilities of lunar architectures. This process directly addresses the top level requirements early in the design process and allows the decision maker to evaluate the highest reliability, lowest cost lunar architectures without being distracted by the performance details of the architecture. To achieve this methodology of bringing optimal cost and reliability solutions to the decision maker, parametric performance, cost, and reliability models are created to model each vehicle element. These models were combined using multidisciplinary optimization techniques and response surface equations to create parametric vehicle models which quickly evaluate the performance, reliability, and cost of the vehicles. These parametric models, known as ROSETTA models, combined with a life cycle cost calculator provide the tools necessary to create a lunar architecture simulation. The integration of the tools into an integrated framework that can quickly and accurately evaluate the lunar architectures is presented. This lunar architecture selection tool is verified and validated against the Apollo and ESAS lunar architectures. The results of this lunar architecture selection tool are then combined into a Pareto frontier to guide the decision maker to producing the highest reliability architecture for a given life cycle cost. With this presented methodology, the decision maker can transparently choose a lunar architecture solution based upon the high level design discriminators. This method can achieve significant reductions in life cycle costs (over 40%) keeping the same architecture reliability as a traditional design process. This methodology also allows the decision maker to choose a solution which achieves a significant reduction in failure rate (over 50%) while maintaining the same life cycle costs as the point solution of a traditional design process.

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Aerodynamic Modeling of Post-Stall and Spin Dynamics of Large Transport Airplanes

2007-08 , Murch, Austin Matthew

This work addressed aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport aircraft. This was accomplished by applying historically successful modeling methods used on high-performance military aircraft to a transport configuration. The overall research approach involved integrating forced oscillation and rotary balance wind tunnel data into an aerodynamic model using several methods of blending these data. The complete aerodynamic model was integrated into a six degree-of-freedom simulation. Experimental data from free-spin wind tunnel testing was used to validate the aerodynamic modeling methods by comparing aerodynamic force and moment coefficients and also to validate the simulation performance by comparing spin mode characteristics and time histories. The aerodynamic model prediction of spin dynamics was generally very good using all of the blending methods studied. In addition, key spin mode characteristics were predicted with a high degree of accuracy. Overall, using the Hybrid Kalviste method of blending forced oscillation and rotary balance data produced the closest match to the free-spin data when comparing aerodynamic coefficients and spin mode characteristics. Several issues were encountered with the blending methods that were exacerbated by nonlinearities and asymmetries in the dynamic aerodynamic data. A new method of looking up dynamic aerodynamic data was proposed to address shortcomings in the blending methods and recommendations were provided on addressing issues with the dynamic aerodynamic data.

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Performance Evaluation of a Side Mounted Shuttle Derived Heavy Lift Launch Vehicle for Lunar Exploration

2006-05-01 , Thompson, Robert W.

The NASA Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely. ESAS determined that the best lunar exploration strategy was to separate the launch of crew from the launch of cargo, thereby requiring two launches per lunar mission. An alternate concept for the cargo launch vehicle is a side mounted Shuttle-derived heavy lift launch. This configuration is similar to previously studied concepts, except engines and structure have been added to the External Tank (ET), making it a complete first stage. The upper stage is mounted on the side of the first stage, much like the Shuttle orbiter is mounted on the side of the ET. Like the Shuttle, solid rocket boosters (SRBs) are also used. This configuration has several performance and operational benefits over an in-line heavy lift launch vehicle. According to the ESAS report, side mount configurations were not considered to be among the most promising configurations, and were not carried forward for further consideration within architectural options. The performance of this launch vehicle is independently analyzed, using multidisciplinary analysis techniques. Methods and tools used include launch trajectory optimization with POST, vehicle aerodynamic analysis using APAS, and weights and sizing using historically based estimating relationships. Principal trade studies performed include first and second stage propulsion (number of engines and engine type), solid rocket booster size (four versus five segment), and staging ∆V. The vehicle design that best meets the requirements for space exploration (lunar and future missions) is presented.

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A Methodology to Link Cost and Reliability for Launch Vehicle Design

2007-06-28 , Krevor, Zachary Clemetson

This dissertation is focused on the quantitative metrics of performance, cost, and reliability for future launch vehicles. Methods are developed that hold performance constant for a required mission and payload so that cost and reliability can be traded. Reliability strategies such as reducing the number of engines, increasing the thrust-to-weight ratio, and adding redundant subsystems all increase launch vehicle reliability. However, there are few references that illustrate the cost of increasing launch vehicle reliability in a disciplined, integrated approach. For launch vehicle design, integrated performance, cost, and reliability disciplines are required to show the sensitivity of cost to different reliability strategies. A methodology is presented that demonstrates how to create the necessary launch vehicle reliability models and integrate them with the performance and cost disciplines. An integrated environment is developed for conceptual design that can rapidly assess thousands of launch vehicle configurations. The design process begins with a feasible launch vehicle configuration and its mission objectives. The performance disciplines, such as trajectory analysis, propulsion, and mass estimation are modeled to include the effects of using different reliability strategies. Reliability models are created based upon the launch vehicle configuration. Engine reliability receives additional attention because engines are historically one of the leading causes of launch vehicle failure. Additionally, the reliability of the propulsion subsystem changes dynamically when a launch vehicle design includes engine out capability. Cost estimating techniques which use parametric models are employed to capture the dependencies on system cost of increasing launch vehicle reliability. Uncertainty analysis is included within the cost and reliability disciplines because of the limited historical database for launch vehicles. Optimization is applied within the integrated design environment to find the best launch vehicle configuration based upon a particular weighting of cost and reliability. The results show that both the Saturn V and future launch vehicles could be optimized to be significantly cheaper, be more reliable, or have a compromise solution by illustrating how cost and reliability are coupled with vehicle configuration changes.

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A Scalable Orbital Propellant Depot Design

2006-05-01 , Street, David

This paper describes the design and features of a Scalable Orbital Propellant Depot Design tool. The purpose of the tool is to enable others to easily test the effectiveness of adding a propellant depot to an exploration architecture. Several options are available including zero boil-off technology, usable propellant and depot geometry. It is assumed that the depot is refillable with a total service life of 10 years and resides in low earth orbit. Examples of depots created with the tool are shown. Application to existing exploration architectures is also discussed.

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