Organizational Unit:

Daniel Guggenheim School of Aerospace Engineering

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https://hdl.handle.net/1853/70742

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College of Engineering

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Aerospace Design Group

Organizational Unit

Aerospace Systems Design Laboratory (ASDL)

Organizational Unit

Air Transportation Laboratory

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Cognitive Engineering Center

Organizational Unit

Space Systems Design Laboratory (SSDL)

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https://finding-aids.library.gatech.edu/agents/corporate_entities/106

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Publication Search Results

Now showing 1 - 10 of 1616

Optimization-based methods for deterministic and stochastic control: Algorithmic development, analysis and applications on mechanical systems & fields

(Georgia Institute of Technology, 2019-12-17) Boutselis, Georgios

Developing efficient control algorithms for practical scenarios remains a key challenge for the scientific community. Towards this goal, optimal control theory has been widely employed over the past decades, with applications both in simulated and real environments. Unfortunately, standard model-based approaches become highly ineffective when modeling accuracy degrades. This may stem from erroneous estimates of physical parameters (e.g., friction coefficients, moments of inertia), or dynamics components which are inherently hard to model. System uncertainty should therefore be properly handled within control methodologies for both theoretical and practical purposes. Of equal importance are state and control constraints, which must be effectively handled for safety critical systems. To proceed, the majority of works in controls and reinforcement learning literature deals with systems lying in finite-dimensional Euclidean spaces. For many interesting applications in aerospace engineering, robotics and physics, however, we must often consider dynamics with more challenging configuration spaces. These include systems evolving on differentiable manifolds, as well as systems described by stochastic partial differential equations. Some problem examples of the former case are spacecraft attitude control, modeling of elastic beams and control of quantum spin systems. Regarding the latter, we have control of thermal/fluid flows, chemical reactors and advanced batteries. This work attempts to address the challenges mentioned above. We will develop numerical optimal control methods that explicitly incorporate modeling uncertainty, as well as deterministic and probabilistic constraints into prediction and decision making. Our iterative schemes provide scalability by relying on dynamic programming principles as well as sampling-based techniques. Depending upon different problem setups, we will handle uncertainty by employing suitable concepts from machine learning and uncertainty quantification theory. Moreover, we will show that well-known numerical control methods can be extended for mechanical systems evolving on manifolds, and dynamics described by stochastic partial differential equations. Our algorithmic derivations utilize key concepts from optimal control and optimization theory, and in some cases, theoretical results will be provided on the convergence properties of the proposed methods. The effectiveness and applicability of our approach are highlighted by substantial numerical results on simulated test cases.
The Design, Assembly, and Testing of Magnetorquers for a 1U CubeSat Mission

(Georgia Institute of Technology, 2019-12-12) Amin, John

Over the next few years Georgia Tech’s Space System Design Lab (SSDL) will design and develop several 1U CubeSat missions starting with GT-1. These missions will include an Attitude Determination and Control Systems (ADCS) utilizing torque rods to control detumble and orbital attitude. This paper describes the design and construction and testing of GT-1’s torque rods and will serve as a resource to help guide future torque rod iterations. The first section details the equations and mathematics behind torque rods. Next, the design section considers factors influencing the magnetic dipole moment including core material, part length, and radius. It then describes the manufacturing and assembly process of torque rods involving core shaping and layer winding. It then describes the test setup to test the torque rod’s magnetic dipole moment and later indicates topics of future work.
Design of a Green Monopropellant Propulsion System for the Lunar Flashlight Mission

(Georgia Institute of Technology, 2019-12-12) Andrews, Dawn ; Lightsey, E. Glenn

The Lunar Flashlight Mission is a lunar-bound small satellite that will investigate the Moon’s poles for water ice. Aboard the spacecraft is a green monopropellant propulsion system that has been designed by the Georgia Institute of Technology under sponsorship and guidance by the NASA Marshall Space Flight Center. Green monopropellant propul sion is a forthcoming technology that promises improvements in performance and safety over existing monopropellant systems such as Hydrazine, making it a very desirable new technology, and Lunar Flashlight will be the first mission to utilize this propulsion on a CubeSat platform. The design solution for the Lunar Flashlight Propulsion System will be shared, as well as the story behind its evolution through the design process. Additionally, several key aspects of its design that are fundamental to green monopropellant propul sion will be collected in contribution to a design methodology for future iterations. This project is intended to continue on to launch with the Artemis-1 Mission, at which point the propulsion system would complete its objectives of contributing flight heritage to this technology while acting as a critical component for the Lunar Flashlight Mission.
Multi-mission sizing and selection methodology for space habitat subsystems

(Georgia Institute of Technology, 2019-12-11) Boutaud, Agathe Kathia

Future space missions aim to set up exploration missions in further space and establish settlements on other celestial bodies like the Moon or Mars. In this context, subsystem sizing and selection is crucial, not only because resource management is critical for the astronauts’ survival, but also because subsystems can account for more than 20% of the total mass of the habitat, so reducing their size can greatly impact the cost of the mission. A few tools already exist to size space habitat subsystems and assess their performance. However, these tools are either very high-fidelity and very slow or instantaneous but steady-state. Steady-state tools do not allow to take risks or mission variations into account and the dynamic, slower tools are less performing at helping stakeholders evaluate the impact of technology trade-offs because of their long running time. Faster sizing tools would also allow to implement additional capabilities, such as multi-mission sizing, which could be used to develop lunar or martian settlements. These tools are also used in the context of point-based design, which focuses on the development of one design throughout the process. Such approach can lead to a sub-optimal design because the selection of an alternative is made early in the design process, based on low-fidelity analyses. In addition, because the costs and design choices are committed early in the design process, requirements or design changes can have very significant cost consequences. This research proposes a new sizing capability, developed using HabNet [1], a dynamic space habitat simulation tool. It is faster than existing dynamic sizing tools and it allowed to develop a multi-mission sizing methodology using Design Space Exploration. Finally, leveraging the faster sizing tool developed to create surrogate models for the size of the elements in the habitat, it was shown that trade-off analyses can be used to support set-based design during the conceptual design phase. Consequently, the methodology proposed is faster than what is currently used to size and select space habitat subsystem technologies. It gives more insight to the user because it can perform instantaneous trade-offs. However, the quality of the surrogate models generated is not sufficient to validate the multi-mission sizing method and environment developed during this thesis. This methodology could be used as a basis for the development of a set-based design method for space habitats. Numerous capabilities, including the evaluation of the impact of disruptions or the level of uncertainty associated with the various alternatives considered, could be easily implemented and added to the existing tool.
X-ray Pulsar Navigation Instrument Performance and Scale Analysis

(Georgia Institute of Technology, 2019-12-06) Payne, Jacob Hurrell

This thesis investigates instruments for autonomous satellite navigation using measurements of X-ray emissions from millisecond pulsars. A manifestation of an instrument for this purpose, called the Neutron star Interior Composition Explorer (NICER), was launched to the International Space Station in 2017. The NICER instrument was designed to observe X-ray emissions from neutron stars for astrophysics research, and is out of scale in terms of volume, power consumption, mass and mechanical complexity to be useful for small satellite missions. This work surveys the range of existing X-ray observation missions to tabulate collecting areas, focal lengths, and optical configurations from milestone missions which describe the evolution of the state of the art in X-ray observatories. A navigation demonstration experiment, called the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), was conducted using the NICER instrument. The experimental performance observed from NICER through the SEXTANT navigation demonstration is compared to theoretical predictions established by existing formulations. It is concluded that SEXTANT benefits from soft band (0.3-4 keV) exposure to achieve better accuracy than predicted by theoretical lower bounds. Additionally, investigation is presented on the readiness of a navigation instrument for small satellites using compound refractive lensing (CRL) and derived designs. X-ray refraction achieves a much shorter focal length than grazing incidence optics at the expense of signal attenuation in the lens material. Performance estimates and previous experimental results are presented as a baseline for physical prototypes and hardware testing to support future development of a physical instrument. The technological hurdle that will enable this tool is manufacturing precise lenses on a 3-micron scale from materials like beryllium with low atomic mass. Recent X-ray concentrator concepts demonstrate progress towards an implementation that can support a CubeSat scale navigation instrument optimized for soft band (0.3-4 keV) X-rays.
Development of a Multidisciplinary Design Analysis Framework for Unmanned Electric Flying Wings

(Georgia Institute of Technology, 2019-12-03) Whitmore, William Valentin

Small-scale subsonic unmanned aerial vehicles have become common tools in both military and civil applications. A vehicle configuration of special interest is the flying wing (aka all-wing or tailless aircraft). This configuration can potentially reduce drag, increase structural efficiency, and decrease detectability. When combined with an electric propulsion system, it produces no observable emissions and possesses fewer maintenance issues. Unfortunately, strong couplings between disciplinary analyses hinder the design of unmanned electric flying wings. In particular, achieving adequate stability characteristics degrades the aerodynamic efficiency of the vehicle, and constrains the available volume in which subsystem components may be placed. Exploiting the potential advantages of electric flying wings therefore necessitates a multidisciplinary perspective. In order to overcome the identified challenges of unmanned electric flying wing design, a multidisciplinary design analysis framework was conceptualized, implemented, and evaluated. The Python-based framework synthesizes automated analysis modules that model geometry, weight distribution, electric propulsion, aerodynamics, stability, and performance. Virtual experiments demonstrated the framework’s utility in quickly exploring a wide design space and assessing design robustness. Two important stand-alone contributions developed for the framework are (1) an algorithm for densely packing battery cells within a wing shape and (2) a parametric electric propulsion analysis code. In short, the framework supports the design of small-scale (i.e. 0-55lb weight range) subsonic unmanned electric flying wings with a host of valuable capabilities that were previously unavailable within traditional design methods.
A Technical Evaluation of Integrating Optical Inter-Satellite Links into Proliferated Polar LEO Constellations

(Georgia Institute of Technology, 2019-12-01) Ingersoll, Joshua

This study evaluates the technical requirements, benefits, and limitations of integrating optical inter-satellite links into a proliferated polar LEO constellation. When compared to traditional radio frequency (RF) links, optical links can transmit orders of magnitude more data at much lower powers in a far more secure method. However, these benefits come with stiff coarse and fine pointing requirements, complex thermal and vibrational satellite bus interfaces, as well as sensitivities to atmospheric conditions for LEO-ground connections. This study breaks optical inter-satellite links (OISL’s) into three distinct categories; in-plane, out-of-plane (crosslink), and LEO-ground. General commercial off the shelf (COTS) state of the art OISL terminal parameters are established. Based on these parameters, varying constellation level implementation strategies are assessed based on latency, bandwidth and technical feasibility using Model Based Systems Engineering principles. These assessments were then re-run at different OISL bandwidths, latencies and costs to evaluate whether the optimal integration technique will change in the future as OISL terminal capability increases. The study finds that the methodology outlined gives crucial insight into future OISL integration and implementation strategies for both current and future mega-constellation architects. Using both current OISL performance parameters as well as future improvements, this study finds that an RF-reliant in-plane architecture is the optimal integration architecture given the constellation configuration constraints. This assessment can help drive the trade space for both OISL vendors producing COTS terminals as well as commercial and military customers looking to integrate OISL terminals into their future constellations.
X-Ray Pulsar Navigation Instrument Performance and Scale Analysis

(Georgia Institute of Technology, 2019-12-01) Payne, Jacob Hurrell

This thesis investigates instruments for autonomous satellite navigation using measurements of X-ray emissions from millisecond pulsars. A manifestation of an instrument for this purpose, called the Neutron star Interior Composition Explorer (NICER), was launched to the International Space Station in 2017. The NICER instrument was designed to observe X-ray emissions from neutron stars for astrophysics research, and is out of scale in terms of volume, power consumption, mass and mechanical complexity to be useful for small satellite missions. This work surveys the range of existing X-ray observation missions to tabulate collecting areas, focal lengths, and optical configurations from milestone missions which describe the evolution of the state of the art in X-ray observatories. A navigation demonstration experiment, called the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), was conducted using the NICER instrument. The experimental performance observed from NICER through the SEXTANT navigation demonstration is compared to theoretical predictions established by existing formulations. It is concluded that SEXTANT benefits from soft band (0.3-4 keV) exposure to achieve better accuracy than predicted by theoretical lower bounds. Additionally, investigation is presented on the readiness of a navigation instrument for small satellites using compound refractive lensing (CRL) and derived designs. X-ray refraction achieves a much shorter focal length than grazing incidence optics at the expense of signal attenuation in the lens material. Performance estimates and previous experimental results are presented as a baseline for physical prototypes and ix hardware testing to support future development of a physical instrument. The technological hurdle that will enable this tool is manufacturing precise lenses on a 3- micron scale from materials like beryllium with low atomic mass. Recent X-ray concentrator concepts demonstrate progress towards an implementation that can support a CubeSat scale navigation instrument optimized for soft band (0.3-4 keV) X-rays
A full scale atmospheric flight experimental research environment for Titan exploration devices

(Georgia Institute of Technology, 2019-12) Afman, J. Pablo ; Feron, Eric

We propose to develop a full-accuracy flight test environment for Titan, the largest moon of Saturn. The experiment would use reduced-g atmospheric flights with a standard aircraft, with appropriate equipment, including a cooled, possibly pressurized environmental chamber.
Mahalanobis Shell Sampling (MSS) method for collision probability computation

(Georgia Institute of Technology, 2019-12-01) Núñez Garzón, Ulises E.

Motivated by desire for collision avoidance in spacecraft formations, and by the need for accurately computing low kinematic probabilities of collision (KPC) in spacecraft collision risk analysis, this work introduces an algorithm for sampling from non-degenerate, multidi mensional normal random variables. In this algorithm, the analytical relationship between certain probability density integrals of such random variables and the chi-square distribution is leveraged in order to provide weights to sample points. In so doing, this algorithm allows direct sampling from probability density “tails” without unduly penalizing sample size, as would occur with Monte Carlo-based methods. The primary motivation for the development of this algorithm is to help in the efficient computation of collision probability measures for relative dynamic systems. Performance of this method in approximating KPC waveforms is examined for a low-dimensionality dynamic example. However, this method could be applied to other dynamic systems and for probability density integrals other than collision probability measures, allowing for efficient computation of such integrals for problems where analytical results do not exist. Therefore, this method is suggested as an alternative to random sampling algorithms such as Monte Carlo methods or the Unscented Transform.