Publications – MIT SSL

411 entries « ‹ 5 of 9 › »

2007

Stewart, Andrzej M

Design and Optimization of Lightweight Space Telescope Structures PhD Thesis

2007.

BibTeX | Tags:

Taylor, Christine

Integrated Transportation System Design Optimization PhD Thesis

2007.

Abstract | BibTeX | Tags:

@phdthesis{taylorIntegratedTransportationSystem2007,
title = {Integrated Transportation System Design Optimization},
author = {Christine Taylor},
year = {2007},
date = {2007-01-01},
number = {May},
abstract = {Traditionally, the design of a transportation system has focused on either the vehicle design or the network flow, assuming the other as given. However, to define a system level architecture for a transportation system, it is advantageous to expand the system boundary during the design process to include the network definition, the vehicle specifications, and the operations, which couple the vehicle(s) and the network. The integrated transportation system formulation developed in this thesis examines these fundamental components by classifying the decisions required to define them and concurrently optimizing the entire design problem, resulting in a more efficient transportation architecture. The integrated transportation system design models are developed for an air and a space transportation system and an example problem is implemented for each. The integrated air transportation system example of an overnight package delivery network quantifies at least a ten percent improvement in cost over traditional opti- mization approaches. The formulation for a space transportation system first requires the definition of a space network which is constructed by extending time expanded networks to account for astrodynamic relationships. An Earth-Moon logistics supply example quantifies a 19 percent improvement in total mass in Low Earth Orbit as compared to traditional optimization methods. The improvements in system objective values obtained can be attributed to the reduction in operational inefficiencies for the transportation system. The concurrent optimization of the integrated transportation system design problem employs a new methodology, embedded optimization, to obtain solutions. Embedded optimization allows Simulated Annealing to effectively find good solutions to highly constrained problems by embedding deterministic solvers, such as linear or mixed integer programs, into the perturbation step. Comparing the solutions and computational performance of SA with and without embedded optimization reveals that embedded optimization performs significantly better, with 95 percent confidence.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

Traditionally, the design of a transportation system has focused on either the vehicle design or the network flow, assuming the other as given. However, to define a system level architecture for a transportation system, it is advantageous to expand the system boundary during the design process to include the network definition, the vehicle specifications, and the operations, which couple the vehicle(s) and the network. The integrated transportation system formulation developed in this thesis examines these fundamental components by classifying the decisions required to define them and concurrently optimizing the entire design problem, resulting in a more efficient transportation architecture. The integrated transportation system design models are developed for an air and a space transportation system and an example problem is implemented for each. The integrated air transportation system example of an overnight package delivery network quantifies at least a ten percent improvement in cost over traditional opti- mization approaches. The formulation for a space transportation system first requires the definition of a space network which is constructed by extending time expanded networks to account for astrodynamic relationships. An Earth-Moon logistics supply example quantifies a 19 percent improvement in total mass in Low Earth Orbit as compared to traditional optimization methods. The improvements in system objective values obtained can be attributed to the reduction in operational inefficiencies for the transportation system. The concurrent optimization of the integrated transportation system design problem employs a new methodology, embedded optimization, to obtain solutions. Embedded optimization allows Simulated Annealing to effectively find good solutions to highly constrained problems by embedding deterministic solvers, such as linear or mixed integer programs, into the perturbation step. Comparing the solutions and computational performance of SA with and without embedded optimization reveals that embedded optimization performs significantly better, with 95 percent confidence.

Warner, Noah Zachary

Theoretical and Experimental Investigation of Hall Thruster Miniaturization By PhD Thesis

2007.

Abstract | BibTeX | Tags:

@phdthesis{warnerTheoreticalExperimentalInvestigation2007,
title = {Theoretical and Experimental Investigation of Hall Thruster Miniaturization By},
author = {Noah Zachary Warner},
year = {2007},
date = {2007-01-01},
number = {May},
abstract = {Interest in small-scale space propulsion continues to grow with the increasing number of small satellite missions, particularly in the area of formation flight. Miniaturized Hall thrusters have been identified as a candidate for lightweight, high specific impulse propulsion systems that can extend mission lifetime and payload capability. A set of scaling laws was developed that allows the dimensions and operating parameters of a miniaturized Hall thruster to be determined from an existing, technologically mature baseline design. The scaling analysis preserves the dominant plasma processes that determine thruster performance including ionization, electron confinement and recombination losses. These scaling laws were applied to the design of a 9mm diameter, nominally 200W thruster based on the Russian D-55 anode layer Hall thruster. The Miniature Hall Thruster (MHT-9) design was further refined using magnetostatic and steady-state thermal finite element modeling techniques. Performance testing was conducted over a wide range of input powers from 20-500W with voltages between 100-300V and propellant flow rates of 0.3-1.0mg/s. Measured thrust was 1-18mN with a maximum thrust efficiency of 34% and specific impulse of 2000s. Significant erosion of thruster surfaces was observed due to the high plasma density required to maintain collisional mean free paths. Although the thrust efficiency was significantly lower than predicted by scaling laws, the MHT-9 is the best performing subcentimeter diameter Hall thruster built to date. A dimensionless performance analysis has shown that while the magnetic confinement ratio was successfully scaled, the thruster did not maintain the desired Knudsen number because of plasma heating. These trends were confirmed using a computational simulation. An analytical model of electron temperature predicts that, due to a larger relative exposed wall area, the peak temperature inside the MHT-9 is higher than that of the D-55, resulting in greater ion losses and beam divergence. The inability to maintain geometric similarity was a result of the inherent challenges of maintaining magnetic field shape and strength at small scale, and this difficulty is identified as the fundamental limitation of Hall thruster miniaturization.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

Interest in small-scale space propulsion continues to grow with the increasing number of small satellite missions, particularly in the area of formation flight. Miniaturized Hall thrusters have been identified as a candidate for lightweight, high specific impulse propulsion systems that can extend mission lifetime and payload capability. A set of scaling laws was developed that allows the dimensions and operating parameters of a miniaturized Hall thruster to be determined from an existing, technologically mature baseline design. The scaling analysis preserves the dominant plasma processes that determine thruster performance including ionization, electron confinement and recombination losses. These scaling laws were applied to the design of a 9mm diameter, nominally 200W thruster based on the Russian D-55 anode layer Hall thruster. The Miniature Hall Thruster (MHT-9) design was further refined using magnetostatic and steady-state thermal finite element modeling techniques. Performance testing was conducted over a wide range of input powers from 20-500W with voltages between 100-300V and propellant flow rates of 0.3-1.0mg/s. Measured thrust was 1-18mN with a maximum thrust efficiency of 34% and specific impulse of 2000s. Significant erosion of thruster surfaces was observed due to the high plasma density required to maintain collisional mean free paths. Although the thrust efficiency was significantly lower than predicted by scaling laws, the MHT-9 is the best performing subcentimeter diameter Hall thruster built to date. A dimensionless performance analysis has shown that while the magnetic confinement ratio was successfully scaled, the thruster did not maintain the desired Knudsen number because of plasma heating. These trends were confirmed using a computational simulation. An analytical model of electron temperature predicts that, due to a larger relative exposed wall area, the peak temperature inside the MHT-9 is higher than that of the D-55, resulting in greater ion losses and beam divergence. The inability to maintain geometric similarity was a result of the inherent challenges of maintaining magnetic field shape and strength at small scale, and this difficulty is identified as the fundamental limitation of Hall thruster miniaturization.

Aoudé, Georges Salim

Two-Stage Path Planning Approach for Designing Multiple Spacecraft Reconfiguration Maneuvers and Application to SPHERES Onboard ISS PhD Thesis

2007.

BibTeX | Tags: ★

Azziz, Yassir

Experimental and Theoretical Characterization of a Hall Thruster Plume PhD Thesis

2007.

Abstract | BibTeX | Tags: Aeronautics and Astronautics.

Baldesarra, Mark

A Decision-Making Framework to Determine the Value of On-Orbit Servicing Compared to Replacement of Space Telescopes PhD Thesis

2007.

BibTeX | Tags: ★

Berkovitz, Dustin

System Characterization and Online Mass Property Identification of the SPHERES Formation Flight Testbed PhD Thesis

2007.

BibTeX | Tags: ★

Celik, Murat

Experimental and Computational Studies of Electric Thruster Plasma Radiation Emission Experimental and Computational Studies of Electric Thruster Plasma Radiation Emission PhD Thesis

2007.

BibTeX | Tags:

Mandy, Christophe P; Sakamoto, Hiraku; Saenz-Otero, Alvar; Miller, David W

Implementation of satellite formation flight algorithms using SPHERES aboard the international space station Journal Article

2007.

BibTeX | Tags:

Mandy, Christophe P; Saenz-Otero, Alvar; Miller, David W

Satellite formation flight and realignment maneuver demonstration aboard the International Space Station Inproceedings

UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III, pp. 66871F, International Society for Optics and Photonics 2007.

BibTeX | Tags:

Mohan, Swati; Sakamoto, Hiraku; Miller, David W

Formation control and reconfiguration through synthetic imaging formation flying testbed (SIFFT) Inproceedings

UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III, pp. 66871E, International Society for Optics and Photonics 2007.

BibTeX | Tags:

Nolet, Simon

The SPHERES navigation system: from early development to on-orbit testing Inproceedings

AIAA Guidance, Navigation and Control Conference and Exhibit, pp. 6354, 2007.

BibTeX | Tags:

Chung, Soon-Jo

Nonlinear Control and Synchronization of Multiple Lagrangian Systems with Application to Tethered Formation Flight Spacecraft PhD Thesis

2007.

BibTeX | Tags: ★

Chung, Soon-Jo; Ahsun, Umair; Slotine, Jean-Jacques; Miller, David

Application of synchronization to cooperative control and formation flight of spacecraft Inproceedings

AIAA Guidance, Navigation and Control Conference and Exhibit, pp. 6861, 2007.

BibTeX | Tags:

Chung, Soon-Jo; Slotine, Jean-Jacques; Miller, David

New Control Strategies for Underactuated Tethered Formation Flight Spacecraft Inproceedings

AIAA Guidance, Navigation and Control Conference and Exhibit, pp. 6858, 2007.

BibTeX | Tags:

Chung, Soon-Jo; Slotine, Jean-Jacques E; Miller, David W

Nonlinear model reduction and decentralized control of tethered formation flight Journal Article

Journal of Guidance, Control, and Dynamics, 30 (2), pp. 390–400, 2007.

BibTeX | Tags:

Nolet, Simon; Saenz-Otero, Alvar; Miller, David W; Fejzic, Amer

SPHERES operations aboard the ISS: Maturation of GN&C algorithms in microgravity Inproceedings

30th Annual AAS Guidance and Control Conference, pp. 07–042, 2007.

BibTeX | Tags:

Cohan, Lucy

Integrated Modeling to Facilitate Control Architecture Design for Lightweight Space Telescopes PhD Thesis

2007.

BibTeX | Tags:

Dietrich, Carl C

Improving Particle Confinement in Inertial Electrostatic Fusion for Spacecraft Power and Propulsion By PhD Thesis

2007, ISBN: http://hdl.handle.net/1721.1/39702.

Abstract | BibTeX | Tags:

Fox, Justin M

Advances in Fully-Kinetic PIC Simulations of a Near-Vacuum Hall Thruster and Other Plasma Systems PhD Thesis

2007.

Abstract | BibTeX | Tags:

@phdthesis{foxAdvancesFullyKineticPIC2007,
title = {Advances in Fully-Kinetic PIC Simulations of a Near-Vacuum Hall Thruster and Other Plasma Systems},
author = {Justin M Fox},
year = {2007},
date = {2007-01-01},
number = {2003},
abstract = {In recent years, many groups have numerically modeled the near-anode region of a Hall thruster in attempts to better understand the associated physics of thruster operation. Originally, simulations assumed a continuum approximation for electrons and used magnetohydrodynamic fluid equations to model the significant processes. While these codes were computationally efficient, their applicability to non-equilibrated regions of the thruster, such as wall sheaths, was limited, and their accuracy was predicated upon the notion that the energy distributions of the various species remained Maxwellian at all times. The next generation of simulations used the fully-kinetic particle-in-cell (PIC) model. Although much more computationally expensive than the fluid codes, the full-PIC codes allowed for non-equilibrated thruster regions and did not rely on Maxwellian distributions. However, these simulations suffered for two main reasons. First, due to the high computational cost, fine meshing near boundaries which would have been required to properly resolve wall sheaths was often not attempted. Second, PIC is inherently a statistically noisy method and often the extreme tails of energy distributions would not be adequately sampled due to high energy particle dissipation. The current work initiates a third generation of Hall thruster simulation. A PIC-Vlasov hybrid model was implemented utilizing adaptive meshing techniques to enable automatically scalable resolution of fine structures during the simulation. The code retained the accuracy and versatility of a PIC simulation while intermittently recalculating and smoothing particle distribution functions within individual cells to ensure full velocity space coverage. In addition, this simulation extended the state of the art in Hall thruster anomalous diffusion modeling by adopting a "quench rule" which is able to predict the spatial and temporal structure of the cross-field transport without the aid of prior empirical data. Truly predictive computations are thus enabled. After being thoroughly tested and benchmarked, the simulation was then applied to the near vacuum Hall thruster recently constructed at MIT. Recommendations to improve that thruster's performance were made based on the simulation's results, and those optimizations are being experimentally implemented by other researchers. This work was conducted with the aid of Delta Search Labs' supercomputing facility and technical expertise. The simulation was fully-parallelized using MPI and tested on a 128 processor SGI Origin machine. We gratefully acknowledge that funding for portions of this work has been provided by the United States Air Force and the National Science Foundation. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

In recent years, many groups have numerically modeled the near-anode region of a Hall thruster in attempts to better understand the associated physics of thruster operation. Originally, simulations assumed a continuum approximation for electrons and used magnetohydrodynamic fluid equations to model the significant processes. While these codes were computationally efficient, their applicability to non-equilibrated regions of the thruster, such as wall sheaths, was limited, and their accuracy was predicated upon the notion that the energy distributions of the various species remained Maxwellian at all times. The next generation of simulations used the fully-kinetic particle-in-cell (PIC) model. Although much more computationally expensive than the fluid codes, the full-PIC codes allowed for non-equilibrated thruster regions and did not rely on Maxwellian distributions. However, these simulations suffered for two main reasons. First, due to the high computational cost, fine meshing near boundaries which would have been required to properly resolve wall sheaths was often not attempted. Second, PIC is inherently a statistically noisy method and often the extreme tails of energy distributions would not be adequately sampled due to high energy particle dissipation. The current work initiates a third generation of Hall thruster simulation. A PIC-Vlasov hybrid model was implemented utilizing adaptive meshing techniques to enable automatically scalable resolution of fine structures during the simulation. The code retained the accuracy and versatility of a PIC simulation while intermittently recalculating and smoothing particle distribution functions within individual cells to ensure full velocity space coverage. In addition, this simulation extended the state of the art in Hall thruster anomalous diffusion modeling by adopting a "quench rule" which is able to predict the spatial and temporal structure of the cross-field transport without the aid of prior empirical data. Truly predictive computations are thus enabled. After being thoroughly tested and benchmarked, the simulation was then applied to the near vacuum Hall thruster recently constructed at MIT. Recommendations to improve that thruster's performance were made based on the simulation's results, and those optimizations are being experimentally implemented by other researchers. This work was conducted with the aid of Delta Search Labs' supercomputing facility and technical expertise. The simulation was fully-parallelized using MPI and tested on a 128 processor SGI Origin machine. We gratefully acknowledge that funding for portions of this work has been provided by the United States Air Force and the National Science Foundation. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Gassend, Blaise Laurent Patrick

A Fully Microfabricated Two-Dimensional Electrospray Array with Applications to Space Propulsion by Blaise Laurent Patrick Gassend PhD Thesis

2007.

Abstract | BibTeX | Tags:

@phdthesis{Gassend2007,
title = {A Fully Microfabricated Two-Dimensional Electrospray Array with Applications to Space Propulsion by Blaise Laurent Patrick Gassend},
author = {Blaise Laurent Patrick Gassend},
year = {2007},
date = {2007-01-01},
abstract = {This thesis presents the design, fabrication and testing of a fully-integrated planar electrospray thruster array, which could lead to more efficient and precise thrusters for space propulsion applications. The same techniques could be used for making arrays to increase throughput in many other electrospray applications. Electrospray thrusters work by electrostatically extracting and accelerating ions or charged droplets from a liquid surface to produce thrust. Emission occurs from sharp emitter tips, which enhance the electric field and constrain the emission location. The electrospray process limits the thrust from a single tip, so that achieving millinewton thrust levels requires an array with tens of thousands of emitters. Silicon batch microfabrication has been used, as it is well suited for making large arrays of emitters. The thruster is made using Deep Reactive Ion Etching (DRIE) and wafer bonding techniques, in a six mask process, and comprises two components. The emitter die with up to 502 emitters in a 113 mm2 area, is formed using DRIE and SF6 etching, and is plasma treated to transport liquid to the tips in a porous black-silicon sur- face layer. The extractor die incorporates the extractor electrode, a Pyrex layer for insulation, and springs which are used to reversibly assemble the emitter die. This versatile assembly method, with 10 textmu m RMS alignment accuracy and 1.3 textmu m RMSD repeatability, allows the extractor die to be reused with multiple emitter dies, and potentially with different emitter concepts than the one presented. The thruster, weighing 5 g, was tested with the ionic liquids EMI-BF4 and EMI- Im. Time of flight measurements show that the thruster operates in the ion emission regime most efficient for propulsion, with a specific impulse around 3000 s at a 1 kV extractor voltage. Emission starts as low as 500 V. Currents of 370 nA per emitter have been recorded at 1500 V, for an estimated thrust of 26 nN per emitter or 13 textmu N total, and a 275 mW power consumption. The thrust efficiency is estimated around 85%. In good operating conditions, the current intercepted on the extractor electrode is well below 1 %, increasing to a few percent at the highest current levels. The beam divergence half width half maximum is between 10 and 15  .},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

This thesis presents the design, fabrication and testing of a fully-integrated planar electrospray thruster array, which could lead to more efficient and precise thrusters for space propulsion applications. The same techniques could be used for making arrays to increase throughput in many other electrospray applications. Electrospray thrusters work by electrostatically extracting and accelerating ions or charged droplets from a liquid surface to produce thrust. Emission occurs from sharp emitter tips, which enhance the electric field and constrain the emission location. The electrospray process limits the thrust from a single tip, so that achieving millinewton thrust levels requires an array with tens of thousands of emitters. Silicon batch microfabrication has been used, as it is well suited for making large arrays of emitters. The thruster is made using Deep Reactive Ion Etching (DRIE) and wafer bonding techniques, in a six mask process, and comprises two components. The emitter die with up to 502 emitters in a 113 mm2 area, is formed using DRIE and SF6 etching, and is plasma treated to transport liquid to the tips in a porous black-silicon sur- face layer. The extractor die incorporates the extractor electrode, a Pyrex layer for insulation, and springs which are used to reversibly assemble the emitter die. This versatile assembly method, with 10 textmu m RMS alignment accuracy and 1.3 textmu m RMSD repeatability, allows the extractor die to be reused with multiple emitter dies, and potentially with different emitter concepts than the one presented. The thruster, weighing 5 g, was tested with the ionic liquids EMI-BF4 and EMI- Im. Time of flight measurements show that the thruster operates in the ion emission regime most efficient for propulsion, with a specific impulse around 3000 s at a 1 kV extractor voltage. Emission starts as low as 500 V. Currents of 370 nA per emitter have been recorded at 1500 V, for an estimated thrust of 26 nN per emitter or 13 textmu N total, and a 275 mW power consumption. The thrust efficiency is estimated around 85%. In good operating conditions, the current intercepted on the extractor electrode is well below 1 %, increasing to a few percent at the highest current levels. The beam divergence half width half maximum is between 10 and 15  .

Hoff, Nicholas

Design and Implementation of a Relative State Estimator for Docking and Formation Control of Modular Autonomous Spacecraft PhD Thesis

2007.

BibTeX | Tags:

Huntington, G T

Advancement and Analysis of a Gauss Pseudospectral Transcription for Optimal Control Problems PhD Thesis

2007.

Abstract | BibTeX | Tags: ★

@phdthesis{Huntington2007,
title = {Advancement and Analysis of a Gauss Pseudospectral Transcription for Optimal Control Problems},
author = {G T Huntington},
year = {2007},
date = {2007-01-01},
abstract = {As optimal control problems become increasingly complex, innovative numerical methods are needed to solve them. Direct transcription methods, and in particular, methods involving orthogonal collocation have become quite popular in several field areas due to their high accuracy in approximating non-analytic solutions with relatively few discretization points. Several of these methods, known as pseudospectral methods in the aerospace engineering community, have also established costate estimation procedures which can be used to verify the optimality of the resulting solution. This work examines three of these pseudospectral methods in detail, specifically the Legendre, Gauss, and Radau pseudospectral methods, in order to assess their accuracy, efficiency, and applicability to optimal control problems of varying complexity. Emphasis is placed on improving the Gauss pseudospectral method, where advancements to the method include a revised pseudospectral transcription for problems with path constraints and differential dynamic constraints, a new algorithm for the computation of the control at the boundaries, and an analysis of a local versus global implementation of the method. The Gauss pseudospectral method is then applied to solve current problems in the area of tetrahedral spacecraft formation flying. These optimal control problems involve multiple finite-burn maneuvers, nonlinear dynamics, and nonlinear inequality path constraints that depend on both the relative and inertial positions of all four spacecraft. Contributions of this thesis include an improved numerical method for solving optimal control problems, an analysis and numerical comparison of several other competitive direct methods, and a greater understanding of the relative motion of tetrahedral formation flight.},
keywords = {★},
pubstate = {published},
tppubtype = {phdthesis}
}

Jordan, Elizabeth

Design and Shape Control of Lightweight Mirrors for Dynamic Performance and Athermalization PhD Thesis

2007.

BibTeX | Tags:

Kim, Susan C

Mission Design and Trajectory Analysis for Inspection of a Host Spacecraft by a Microsatellite PhD Thesis

2007, ISSN: 1095323X.

Abstract | Links | BibTeX | Tags: ★

Legge, R; Lozano, Paulo; Martinez-Sanchez, Manuel

Fabrication and characterization of porous metal emitters for electrospray thrusters Inproceedings

30th International Electric Propulsion Conference, Florence, Italy, September 2007, IEPC-2007, 2007.

BibTeX | Tags:

2006

Siddiqi, Afreen

Reconfigurability in Space Systems: Architecting Framework and Case Studies PhD Thesis

2006.

Abstract | BibTeX | Tags:

@phdthesis{Siddiqi2006a,
title = {Reconfigurability in Space Systems: Architecting Framework and Case Studies},
author = {Afreen Siddiqi},
year = {2006},
date = {2006-01-01},
number = {May},
abstract = {Reconfigurability in engineered systems is of increasing interest particularly in Aerospace Systems since it allows for resource efficiency, evolvability, and enhanced survivability. Although it is often regarded as a desirable quality for a system, it has traditionally been difficult to quantitatively analyze its effects on various system properties in the early design stage. In order to allow for gaining an in-depth understanding of the various aspects of reconfigurability and its relationship with a system's architecture, a framework encompassing a set of definitions, metrics, and methods has been proposed. Two different modeling schemes, based on Markov models and controls theory, are first developed to show how the states and time aspects of reconfigurable systems can be naturally modeled and studied. An analytical model for quantifying the effect of reconfigurability on mission logistics, specifically spare parts demands, is formulated and it is shown through one specific example that reconfigurable parts can allow for 33-50% mass reduction. The system availability, however, becomes very sensitive to the reliability of the parts. Two case studies are then used for detailed illustration of the application of the developed framework.(cont.) In the first case study, the effect of reconfigurability on a fleet of planetary surface vehicles for a surface exploration mission are analyzed. It is found that a fleet of reconfigurable vehicles can allow for a mass savings of up to 27% and their expected transport capability degradation is almost three times lower as compared to a fleet of non-reconfigurable vehicles. In the second case-study, the reconfiguration of low earth-orbit communication satellite constellations is considered for evolving to higher capacity levels. It is found that reconfiguring a previously deployed constellation can be a viable option only for certain capacity levels and multi-payload launch capability scenarios. In addition to the high level 'ility' perspectives, a lower level design assessment is also carried out through a survey of 33 representative reconfigurable systems. It is found that on average, for commercial items the cost of reconfigurability is 35%, and the average useful state occupancy time is always at least 10 times the reconfiguration time of the system. Based on the illustrative results of the case studies, and generalization of empirical data, a few principles and guidelines for design for reconfigurability are proposed.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

Reconfigurability in engineered systems is of increasing interest particularly in Aerospace Systems since it allows for resource efficiency, evolvability, and enhanced survivability. Although it is often regarded as a desirable quality for a system, it has traditionally been difficult to quantitatively analyze its effects on various system properties in the early design stage. In order to allow for gaining an in-depth understanding of the various aspects of reconfigurability and its relationship with a system's architecture, a framework encompassing a set of definitions, metrics, and methods has been proposed. Two different modeling schemes, based on Markov models and controls theory, are first developed to show how the states and time aspects of reconfigurable systems can be naturally modeled and studied. An analytical model for quantifying the effect of reconfigurability on mission logistics, specifically spare parts demands, is formulated and it is shown through one specific example that reconfigurable parts can allow for 33-50% mass reduction. The system availability, however, becomes very sensitive to the reliability of the parts. Two case studies are then used for detailed illustration of the application of the developed framework.(cont.) In the first case study, the effect of reconfigurability on a fleet of planetary surface vehicles for a surface exploration mission are analyzed. It is found that a fleet of reconfigurable vehicles can allow for a mass savings of up to 27% and their expected transport capability degradation is almost three times lower as compared to a fleet of non-reconfigurable vehicles. In the second case-study, the reconfiguration of low earth-orbit communication satellite constellations is considered for evolving to higher capacity levels. It is found that reconfiguring a previously deployed constellation can be a viable option only for certain capacity levels and multi-payload launch capability scenarios. In addition to the high level 'ility' perspectives, a lower level design assessment is also carried out through a survey of 33 representative reconfigurable systems. It is found that on average, for commercial items the cost of reconfigurability is 35%, and the average useful state occupancy time is always at least 10 times the reconfiguration time of the system. Based on the illustrative results of the case studies, and generalization of empirical data, a few principles and guidelines for design for reconfigurability are proposed.

a. Uebelhart, Scott

Non-Deterministic Design and Analysis of Parameterized Optical Structures during Conceptual Design PhD Thesis

2006.

Abstract | BibTeX | Tags:

@phdthesis{uebelhartNonDeterministicDesignAnalysis2006,
title = {Non-Deterministic Design and Analysis of Parameterized Optical Structures during Conceptual Design},
author = {Scott a. Uebelhart},
year = {2006},
date = {2006-01-01},
number = {June},
abstract = {The next generation of space observatories will use larger mirrors while meeting tighter optical performance requirements than current space telescopes. The spacecraft designs must satisfy the drive for low-mass, low-cost systems, and be robust to uncertainty since design validation will be based on analysis instead of pre-launch tests. Analytical tech- niques will be required to identify which technologies or structural architectures are most appropriate to meet conflicting system requirements, but traditionally, model-based dynamic analysis would only take place after a single point design is chosen. The challenges facing future space telescopes require a new approach to conceptual design, and motivate the creation of design tools to identify superior, robust designs earlier in the design lifecycle using model-based analysis methods. A conceptual design methodology is proposed, in which both nominal performance as well as robustness to uncertainty are evaluated across multiple design realizations. A model- ing environment is created so that for any set of design variables, such as mirror architecture or dimensions of the spacecraft, a finite element model is automatically generate and ana- lyzed. A frequency-based dynamic analysis is performed for each design realization using integrated disturbance-to-performance models that include control systems and vibration isolators. Next, the uncertainty in early stages of design is considered and Design of Experiments tools such as the analysis of variance are used to identify critical uncertainty parameters. Lastly, parametric uncertainties are propagated through the model to bound the outputs. Aspects of this methodology are applied to several telescopes in order to demonstrate the practicality of this approach in real-life design studies. Critical uncertainty parameter identification and uncertainty analysis tools are applied to the Terrestrial Planet Finder interferometer. A parameterized model is prepared and a trade-space analysis performed for the ground-based Thirty Meter Telescope. Finally, the methodology as a whole is applied to a new space telescope design employing lightweight mirrors and a segmented aperture. An exploration of the design space is followed by uncertainty evaluation of the optimal designs. Over 1200 unique design realizations are evaluated, and the architecture families that provide the best performance and robustness to uncertainty are identified.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

The next generation of space observatories will use larger mirrors while meeting tighter optical performance requirements than current space telescopes. The spacecraft designs must satisfy the drive for low-mass, low-cost systems, and be robust to uncertainty since design validation will be based on analysis instead of pre-launch tests. Analytical tech- niques will be required to identify which technologies or structural architectures are most appropriate to meet conflicting system requirements, but traditionally, model-based dynamic analysis would only take place after a single point design is chosen. The challenges facing future space telescopes require a new approach to conceptual design, and motivate the creation of design tools to identify superior, robust designs earlier in the design lifecycle using model-based analysis methods. A conceptual design methodology is proposed, in which both nominal performance as well as robustness to uncertainty are evaluated across multiple design realizations. A model- ing environment is created so that for any set of design variables, such as mirror architecture or dimensions of the spacecraft, a finite element model is automatically generate and ana- lyzed. A frequency-based dynamic analysis is performed for each design realization using integrated disturbance-to-performance models that include control systems and vibration isolators. Next, the uncertainty in early stages of design is considered and Design of Experiments tools such as the analysis of variance are used to identify critical uncertainty parameters. Lastly, parametric uncertainties are propagated through the model to bound the outputs. Aspects of this methodology are applied to several telescopes in order to demonstrate the practicality of this approach in real-life design studies. Critical uncertainty parameter identification and uncertainty analysis tools are applied to the Terrestrial Planet Finder interferometer. A parameterized model is prepared and a trade-space analysis performed for the ground-based Thirty Meter Telescope. Finally, the methodology as a whole is applied to a new space telescope design employing lightweight mirrors and a segmented aperture. An exploration of the design space is followed by uncertainty evaluation of the optimal designs. Over 1200 unique design realizations are evaluated, and the architecture families that provide the best performance and robustness to uncertainty are identified.

Wertz, Julie A

Expected Productivity-Based Risk Analysis in Conceptual Design : With Application to the Terrestrial Planet Finder Interferometer Mission PhD Thesis

2006.

BibTeX | Tags:

Ahsun, Umair

Dynamics and Control of Electromagnetic Satellite Formations PhD Thesis

2006, ISSN: 07431619.

Abstract | Links | BibTeX | Tags:

Bairstow, Brian

Effectiveness of Integration of System-Level Optimization in Concurrent Engineering for Rocket Design PhD Thesis

2006.

BibTeX | Tags:

Chung, Soon-Jo; Adams, Danielle; Saenz-Otero, Alvar; Kong, Edmund; Miller, David W; Leisawitz, David; Lorenzini, Enrico; Sell, Steve

SPHERES tethered formation flight testbed: advancements in enabling NASA's SPECS mission Inproceedings

Advances in Stellar Interferometry, pp. 62680B, International Society for Optics and Photonics 2006.

BibTeX | Tags:

Deems, Elizabeth

Risk Management of Student-Run Small Satellite Programs PhD Thesis

2006, ISBN: 9781605600390.

Abstract | BibTeX | Tags:

York, Stephen P

Engine Placement for Manned Descent at Mars Jaime Peraire PhD Thesis

2006.

BibTeX | Tags:

Huffman, Kara M

Designing Star Trackers to Meet Micro-Satellite Requirements PhD Thesis

2006, ISBN: 9781624100512.

Abstract | Links | BibTeX | Tags:

@phdthesis{huffmanDesigningStarTrackers2006,
title = {Designing Star Trackers to Meet Micro-Satellite Requirements},
author = {Kara M Huffman},
doi = {10.2514/6.2006-5654},
isbn = {9781624100512},
year = {2006},
date = {2006-01-01},
number = {May 2004},
abstract = {Star trackers provide numerous advantages over other attitude sensors because of their flexibility to operate independently from other navigation tools and their ability to provide full three-axis orientation information with high accuracy. However, current star trackers are optimized to maximize accuracy, at the exclusion of all else. Although this produces extremely capable systems, the lofty mass, power consumption, and cost that result are often contradictory to the requirements of smaller space vehicles. Thus, it is of interest to design smaller, lower cost, albeit reduced capability star trackers that can provide adequate attitude and rate determination to small, highly maneuverable, low-cost spacecraft. To meet physical requirements, appropriate constraints on memory, computational speed, and optics must been defined and included in the hardware selection and software design. The primary software algorithms must include functions to extract and centroid stars from image noise and to match star patterns between subsequent images or to a small on-board catalog. Multiple pattern matching algorithms can be implemented in a dynamic manner based on the number of stars present in the image and whether or not current rate information is available. This provides several modes of operation and graceful degradation of performance at higher angular rates. The algorithms used incorporate various aspects from open literature, but include appropriate modifications and improvements where applicable. Thresholding at low signal-to-noise ratios is accomplished via a statistical pre-filter to address high noise content. Centroiding examines the stellar shape to optimally set the aperture shutter time for different rotation rates. Pattern matching between frames implements a 'smart' star selection technique to avoid wasted time on stars that might not appear in both images. An n-vertex pattern match is performed against a star catalog that has been reduced either based on the probability that the stars would be used or by existing attitude information. Finally, quaternion solutions are generated using a recursive estimation technique. This paper discusses the analysis used to select hardware and predict system performance, as well as the algorithms that have been employed to determine attitude information and rotation rates of the spacecraft. The performance of these algorithms using computer simulated images, nighttime photographs, and images captured directly by star tracker prototypes are presented. textcopyright 2006 by Kara M. Huffman.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

Star trackers provide numerous advantages over other attitude sensors because of their flexibility to operate independently from other navigation tools and their ability to provide full three-axis orientation information with high accuracy. However, current star trackers are optimized to maximize accuracy, at the exclusion of all else. Although this produces extremely capable systems, the lofty mass, power consumption, and cost that result are often contradictory to the requirements of smaller space vehicles. Thus, it is of interest to design smaller, lower cost, albeit reduced capability star trackers that can provide adequate attitude and rate determination to small, highly maneuverable, low-cost spacecraft. To meet physical requirements, appropriate constraints on memory, computational speed, and optics must been defined and included in the hardware selection and software design. The primary software algorithms must include functions to extract and centroid stars from image noise and to match star patterns between subsequent images or to a small on-board catalog. Multiple pattern matching algorithms can be implemented in a dynamic manner based on the number of stars present in the image and whether or not current rate information is available. This provides several modes of operation and graceful degradation of performance at higher angular rates. The algorithms used incorporate various aspects from open literature, but include appropriate modifications and improvements where applicable. Thresholding at low signal-to-noise ratios is accomplished via a statistical pre-filter to address high noise content. Centroiding examines the stellar shape to optimally set the aperture shutter time for different rotation rates. Pattern matching between frames implements a 'smart' star selection technique to avoid wasted time on stars that might not appear in both images. An n-vertex pattern match is performed against a star catalog that has been reduced either based on the probability that the stars would be used or by existing attitude information. Finally, quaternion solutions are generated using a recursive estimation technique. This paper discusses the analysis used to select hardware and predict system performance, as well as the algorithms that have been employed to determine attitude information and rotation rates of the spacecraft. The performance of these algorithms using computer simulated images, nighttime photographs, and images captured directly by star tracker prototypes are presented. textcopyright 2006 by Kara M. Huffman.

Jeffrey, Matthew M

Closed-Loop Control of Spacecraft Formations with Applications on SPHERES PhD Thesis

2006.

BibTeX | Tags:

Lim, Ryan

Staged Attitude-Metrology Pointing Control and Parametric Integrated Modeling for Space-based Optical Systems PhD Thesis

2006.

BibTeX | Tags:

2005

Pigeon, Timothy

Studies of Plume Condensation Contamination upon Surfaces of the Terrestrial Planet Finder Spacecraft Accepted by łdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdotsłdots. Acknowledgments PhD Thesis

2005.

BibTeX | Tags:

Masterson, Rebecca A

Dynamic Tailoring and Tuning for Precision Optical Space Structures PhD Thesis

2005, ISSN: 02734508.

Abstract | Links | BibTeX | Tags:

McGuire, TJ; Sedwick, RJ

Improved confinement in inertial electrostatic confinement for fusion space power reactors Journal Article

Journal of propulsion and power, 21 (4), pp. 697–706, 2005.

BibTeX | Tags:

Schweighart, Samuel; Sedwick, Raymond J

Cross-Track Motion of Satellite Formations in the Presence of J2 Disturbances Journal Article

Journal of Guidance Control and Dynamics - J GUID CONTROL DYNAM, 28 , pp. 824-826, 2005.

Links | BibTeX | Tags:

Nadir, William David

Multidisciplinary Structural Design and Optimization for Performance, Cost, and Flexibility PhD Thesis

2005.

Abstract | BibTeX | Tags:

Neave, Matthew

Dynamic and Thermal Control of an Electromagnetic Formation Flight Testbed PhD Thesis

2005.

BibTeX | Tags:

Rodgers, Lennon

Concepts and Technology Development for the Autonomous Assembly and Reconfiguration of Modular Space Systems Professor of Mechanical Engineering Chairman, Committee on Graduate Students PhD Thesis

2005.

Abstract | BibTeX | Tags: Mechanical Engineering., Thesis

Saenz-Otero, Alvar

Design Principles for the Development of Space Technology Maturation Laboratories Aboard the International Space Station PhD Thesis

MIT, 2005.

BibTeX | Tags: ★

Samuels, Ayanna

Assessing the Technical, Economic and Policy-centered Feasibility of a Proposed Satellite Communication System for the Developing World PhD Thesis

2005.

BibTeX | Tags:

Schweighart, Samuel

Electromagnetic Formation Flight Dipole Solution Planning PhD Thesis

2005, ISSN: 00653438.

Abstract | BibTeX | Tags:

Zeineh, Christopher F

Applications of an Electrostatic High-Voltage Tether to Radiation Belt Remediation By PhD Thesis

2005.

BibTeX | Tags:

Bounova, Gergana

Graph-Theoretical Consideration in the Design of Complex Engineering Systems for Robustness and Scalability PhD Thesis

2005.

BibTeX | Tags:

Carretero-benignos, Jorge Alejandro

Numerical Simulation of a Single Emitter Colloid Thruster in Pure Droplet Cone-Jet Mode Numerical Simulation of a Single Emitter Colloid Thruster in Pure Droplet Cone-Jet Mode By PhD Thesis

2005.

Abstract | BibTeX | Tags:

@phdthesis{carretero-benignosNumericalSimulationSingle2005,
title = {Numerical Simulation of a Single Emitter Colloid Thruster in Pure Droplet Cone-Jet Mode Numerical Simulation of a Single Emitter Colloid Thruster in Pure Droplet Cone-Jet Mode By},
author = {Jorge Alejandro {Carretero-benignos}},
year = {2005},
date = {2005-01-01},
number = {February},
abstract = {New Scientific missions call for emerging propulsion technologies capable of fine tuning a satellites relative position and cancelling small disturbances. One candidate technology that holds promise for these type of missions are colloidal thrusters. These thrusters are elec- trostatic accelerators which do not rely on gas ionization (plasma), are intrinsically small, and operate at low power levels, while having small plume divergence angles to avoid space- craft (S/C) contamination problems. Colloid thrusters deliver low thrust (0.1 textmu N/emitter) which can be multiplied many times over by integrating them in microfabricated arrays. An important advantage is that with proper choice of propellant and operating regime their specific impulse can be tailored from 500-7000 seconds making them viable candidates for a multitude of mission profiles. In the past many research groups have worked on developing colloid thrusters; however, their basic physics are still not completely understood. For this reason, we have undertaken the development of a numerical simulation of a colloid thruster to complement experimental and analytical research in the area. The goal of this project has been to create a flexible nu- merical tool to compute single-emitter current, droplet size, velocity, electric field strengths for a given geometry, fluid, flow rate, and voltage. We have approached this issue fromthe numerical perspective by developing a simulation of a colloid thruster operating in the single cone-jet pure droplet mode. Our numerical simulation models the cone-jet transition region of the colloid jet; starting from the needle up to the extractor grid, thus reproducing a typical electrospray experimental configuration. The liquid ismodelled as an incompressible viscous fluid with constant conductivity. Surface charge relaxation effects are included, and the potential and electric fields are solved for. The equations have been simplified by employing a slenderness approximation except for the free surface boundary conditions where the terms have been kept exact, in order to reproduce the Taylor cone shape correctly. Simulation results are shown to compare well to experimental data for a variety of liquids, and flow rates. In more detail, this thesis presents (a) results for a broader parametric range than previously published materials; (b) careful comparison to available experimental data and scalings proposed by several authors; (c) validation of several simple sub-models for the cone and jet sections; (d) analysis of length scales in the cone-jet transition region; (e) clarification of the role of relative permittivity for the range 7-110; (f) discussion of electrode geometry and counter-electrode effects; (g) preliminary results for the onset of ion evaporation. 2},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}

New Scientific missions call for emerging propulsion technologies capable of fine tuning a satellites relative position and cancelling small disturbances. One candidate technology that holds promise for these type of missions are colloidal thrusters. These thrusters are elec- trostatic accelerators which do not rely on gas ionization (plasma), are intrinsically small, and operate at low power levels, while having small plume divergence angles to avoid space- craft (S/C) contamination problems. Colloid thrusters deliver low thrust (0.1 textmu N/emitter) which can be multiplied many times over by integrating them in microfabricated arrays. An important advantage is that with proper choice of propellant and operating regime their specific impulse can be tailored from 500-7000 seconds making them viable candidates for a multitude of mission profiles. In the past many research groups have worked on developing colloid thrusters; however, their basic physics are still not completely understood. For this reason, we have undertaken the development of a numerical simulation of a colloid thruster to complement experimental and analytical research in the area. The goal of this project has been to create a flexible nu- merical tool to compute single-emitter current, droplet size, velocity, electric field strengths for a given geometry, fluid, flow rate, and voltage. We have approached this issue fromthe numerical perspective by developing a simulation of a colloid thruster operating in the single cone-jet pure droplet mode. Our numerical simulation models the cone-jet transition region of the colloid jet; starting from the needle up to the extractor grid, thus reproducing a typical electrospray experimental configuration. The liquid ismodelled as an incompressible viscous fluid with constant conductivity. Surface charge relaxation effects are included, and the potential and electric fields are solved for. The equations have been simplified by employing a slenderness approximation except for the free surface boundary conditions where the terms have been kept exact, in order to reproduce the Taylor cone shape correctly. Simulation results are shown to compare well to experimental data for a variety of liquids, and flow rates. In more detail, this thesis presents (a) results for a broader parametric range than previously published materials; (b) careful comparison to available experimental data and scalings proposed by several authors; (c) validation of several simple sub-models for the cone and jet sections; (d) analysis of length scales in the cone-jet transition region; (e) clarification of the role of relative permittivity for the range 7-110; (f) discussion of electrode geometry and counter-electrode effects; (g) preliminary results for the onset of ion evaporation. 2

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