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Full-Text Articles in Space Vehicles
Developing A Lean Spacecraft Test And Evaluation Architecture For A Contested Space Domain, Stephen K. Tullino
Developing A Lean Spacecraft Test And Evaluation Architecture For A Contested Space Domain, Stephen K. Tullino
Theses and Dissertations
The US Space Force (USSF) is currently investigating possible opportunities to improve the testing paradigm of spacecraft in order to get assets on-orbit faster, while maintaining suitable quality to meet mission needs in a contested space environment. To support this goal, USSF’s approach to test and evaluation (T&E) is centered around the concept of integrated test. In this research, the space text lexicon is defined, addressing the ambiguities on exactly what integrated test is with respect to spacecraft systems development and on-orbit mission assurance. This research considered any statistical trends in categorical discrepancies (i.e., anomalies) during prelaunch integration and test …
Preliminary Architecture Assessment Of Lunar Surface Sensors For Cislunar Ssa, Clint J. Spesard
Preliminary Architecture Assessment Of Lunar Surface Sensors For Cislunar Ssa, Clint J. Spesard
Theses and Dissertations
The exploration of the lunar and cislunar realm is becoming increasingly active as several entities, private and public, foreign and domestic, set their sights beyond traditional Earth-centered space operations. Along with this renewed activity is a growing need for comprehensive Space Situational Awareness (SSA) and Space Traffic Management (STM) in the inherently chaotic cislunar system. This thesis seeks to embolden the study of cislunar SSA by considering the lunar-surface as a platform from which to conduct optical SSA. In this thesis, a lunar-based SSA system is heuristically optimized via a genetic algorithm through three separate implementations. All surface locations considered …
Statistical Reliability Estimation Of Space Launch Vehicles, Brooke N. Wagenblast
Statistical Reliability Estimation Of Space Launch Vehicles, Brooke N. Wagenblast
Theses and Dissertations
Space launch vehicle reliability is imperative to understand since launch vehicles are crucial in getting payloads into space for a hopefully successful mission. This thesis examines the reliability of commercial, civil, and military space launch vehicles through trend analysis and a variety of statistical methods. Data sets obtained from the Seradata database are analyzed for trends by looking at data subsets including launch date, launch country, final mission orbit, section (commercial, civil or military), launch vehicle family and failed subsystem. First-level Bayesian analysis and mean success rates are performed, primarily split up by launch vehicle family and total launches, and …
Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook
Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook
Theses and Dissertations
The imaging and inspection of Resident Space Objects (RSOs) is an increasingly important mission as space-faring nations and commercial enterprises alike seek to develop means to repair and refuel spacecraft, as well as de-orbit RSOs to reduce orbital debris. Lighting conditions are not always advantageous for an imaging/inspection or repair/refuel spacecraft; therefore, the use of mirror spacecraft to reflect solar energy is proposed to illuminate dimly lit RSOs. The present research investigates the efficacy of space-based reflectors at examining spacecraft in the cislunar environment. Specific assessments include target spacecraft in geosynchronous Earth orbit and periodic orbits around selected Lagrange points, …
Investigation Of Ultem 9085 For Use In Printed Orbital Structures, William R. Gallagher
Investigation Of Ultem 9085 For Use In Printed Orbital Structures, William R. Gallagher
Theses and Dissertations
Additive manufacturing is revolutionizing industries ranging from medicine to space. However, the structural characteristics of plastic parts created by these methods are not as well understood as their more established counterparts. This research explored two relevant areas: how the structural characteristics of ULTEM 9085 plastic behaved after exposure to orbital conditions and the design of the cross-sectional area of a beam to be 3-D printed in microgravity based on the expected loads from the printer. To study orbital effects, ULTEM 9085 was printed into 1/4th scale ASTM D638- 14 dogbones using a Stratasys 450mc printer. These dogbones were placed in …
Optimal And Robust Neural Network Controllers For Proximal Spacecraft Maneuvers, Brandon Cole George
Optimal And Robust Neural Network Controllers For Proximal Spacecraft Maneuvers, Brandon Cole George
Theses and Dissertations
Recent successes in machine learning research, buoyed by advances in computational power, have revitalized interest in neural networks and demonstrated their potential in solving complex controls problems. In this research, the reinforcement learning framework is combined with traditional direct shooting methods to generate optimal proximal spacecraft maneuvers. Open-loop and closed-loop feedback controllers, parameterized by multi-layer feed-forward artificial neural networks, are developed with evolutionary and gradient-based optimization algorithms. Utilizing Clohessy- Wiltshire relative motion dynamics, terminally constrained fixed-time, fuel-optimal trajectories are solved for intercept, rendezvous, and natural motion circumnavigation transfer maneuvers using three different thrust models: impulsive, finite, and continuous. In addition …
Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco
Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco
Theses and Dissertations
Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. …
Comprehensive Study Of Study Of Optimal Synergetic Skip Entries With Dynamic Thrust Vectoring Control, Jeremiah M. Webb
Comprehensive Study Of Study Of Optimal Synergetic Skip Entries With Dynamic Thrust Vectoring Control, Jeremiah M. Webb
Theses and Dissertations
The atmospheric skip entry has been studied since London's presentation in 1962 describing a more fuel efficient means of altering the orbital inclination of satellites. Since London, research over the decades since has traversed many aspects of this field with varying degrees of success. The present research employs the use of modern optimal control software, complex dynamics with minor simplifications, and thrust vectoring to re-approach the aerocruise atmospheric skip entry. Using the aerodynamics of the X-34, the aerocruise problem is first compared to the un-powered aeroglide where it is shown that the aerocruise is capable of increasing the inclination change …
Limited-Duty-Cycle Satellite Formation Control Via Differential Drag, Talon A. Townley
Limited-Duty-Cycle Satellite Formation Control Via Differential Drag, Talon A. Townley
Theses and Dissertations
As CubeSat formation flying missions relying on differential drag control become increasingly common, additional missions based on this control must be studied. A mission planning tool is investigated to control the relative spacing of a CubeSat formation where differential drag is the sole control mechanism. System performance is investigated under varying perturbations and a range of system parameters, including limiting the control duty cycle. Optimal solutions based on using a pseudo spectral numerical solver, GPOPS-II, to minimize maneuver time. This study includes the development of a mission planning tool to work with the modeled CubeSat mission to calculate optimal maneuvers …
Design And Testing Of An Additively Manufactured Cubesat Structural Bus, Karson A. Roberts
Design And Testing Of An Additively Manufactured Cubesat Structural Bus, Karson A. Roberts
Theses and Dissertations
Recent innovations in additive manufacturing and design capabilities have opened the door for more opportunities to integrate multiple functions into a structural de- sign. Specifically, 3D printing through advanced laser powder bed fusion of metal powder allows for the development and integration of advanced structures that were previously unachievable. The demonstration of these techniques on a small satellite results in a structural bus consisting of various external and internal features, increasing its functionality and capabilities beyond simply providing structural support. 3D printing a multi-functional CubeSat bus with these integrated features such as internal lattices and wiring tabs demonstrates a new …
Parameter Study Of An Orbital Debris Defender Using Two Team, Three Player Differential Game Theory, David F. Spendel
Parameter Study Of An Orbital Debris Defender Using Two Team, Three Player Differential Game Theory, David F. Spendel
Theses and Dissertations
The United States Air Force and other national agencies rely on numerous space assets to project their doctrine. However, space is becoming an increasingly congested, contested, and competitive environment. A common risk mitigation strategy for the orbit debris problem is either performing evasive maneuvers, or placing additional shielding on the satellite before launch. Current risk mitigation strategies have significant consequences to satellite operators and may not produce sufficient risk mitigation. This research poses that an orbital debris defender, which would defend the primary satellite from orbital debris, may be a more effective risk mitigation strategy. By assuming the worst case …
Characterization And Analysis Of Plasma Instabilities In A 600 W Permanent Magnet Hall Thruster, Samuel D. Wright
Characterization And Analysis Of Plasma Instabilities In A 600 W Permanent Magnet Hall Thruster, Samuel D. Wright
Theses and Dissertations
Electric propulsion is an important technology for the future of space operations and exploration. Within the range of electric propulsion devices, Hall Effect Thrusters provide a balance of thrust and specific impulse well-suited for many Earth-centric missions. Hall Effect Thrusters have been studied since their development in the 1960s and have been flown on hundreds of spacecraft, but the intimate details of the plasma behavior within the thruster exhaust plume are still not well understood. Furthering this knowledge may be key to improving thruster design to yield better performance and longer lifetimes. To this end, experiments were conducted to measure …
The Study And Application Of Carbon Nanotube Film Heaters For Space Applications, Christopher C. Rocker
The Study And Application Of Carbon Nanotube Film Heaters For Space Applications, Christopher C. Rocker
Theses and Dissertations
The purpose of this research was to examine the feasibility of using Carbon Nanotube (CNT) sheets as thin film heaters for space applications. The ability to maintain the temperature of space components has a direct impact on a space vehicle's operation and longevity. Currently etched foil heaters are used to heat satellite batteries. Battery heaters are the focus of this research. However, as this study will show, they have limitations and are susceptible to failure. CNT sheets have many beneficial properties and show potential in replacing the etched foil design. In this study test specimens were created by forming laminate …
Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation, Justin D. Katzovitz
Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation, Justin D. Katzovitz
Theses and Dissertations
An increasingly congested space environment requires real-time and dynamic space situational awareness (SSA) on both domestic and foreign space objects in Earth orbits. Current statistical orbit determination (SOD) techniques are able to estimate and track trajectories for cooperative spacecraft. However, a non-cooperative spacecraft performing unknown maneuvers at unknown times can lead to unexpected changes in the underlying dynamics of classical filtering techniques. Adaptive estimation techniques can be utilized to build a bank of recursive estimators with different hypotheses on a system's dynamics. The current study assesses the use of a multiple model adaptive estimation (MMAE) technique for detecting and characterizing …
Satellite Propulsion Spectral Signature Detection And Analysis For Space Situational Awareness Using Small Telescopes, Pamela L. Wheeler
Satellite Propulsion Spectral Signature Detection And Analysis For Space Situational Awareness Using Small Telescopes, Pamela L. Wheeler
Theses and Dissertations
Safe satellite operations are of utmost importance. Maintaining precise orbital maintenance places stringent performance requirements on current propulsion systems, which are often electric propulsion systems. Electron temperature is a commonly used diagnostic to determine the performance of a Hall thruster, and recent work has correlated near infrared (NIR) spectral measurements of ionization lines of xenon and krypton to electron temperature measurements. In the research herein, appropriate line spectra ratios are identified for each propellant type when used with remote space-to-ground observations. NIR plume emissions were used to characterize a 600 Watt Hall thruster for a variety of observation angles and …
Analysis Of An Experimental Space Debris Removal Mission, Krista L. L. Roth
Analysis Of An Experimental Space Debris Removal Mission, Krista L. L. Roth
Theses and Dissertations
Encountering space debris is an ever-increasing problem in space exploration and exploitation, especially in Low Earth Orbit. While many space-faring governing bodies have attempted to control the orbital lifetime post mission completion of satellites and rocker bodies, objects already in orbit pose a danger to future mission planning. Currently, governments and academic institutions are working to develop missions to remove space debris; however, the proposed missions are typically costly primary missions. This research proposes an alternative to use an upper stage rocket, to be called a chaser, already launching a primary mission near the desired debris as a host for …
Military Space Mission Design And Analysis In A Multi-Body Environment: An Investigation Of High-Altitude Orbits As Alternative Transfer Paths, Parking Orbits For Reconstitution, And Unconventional Mission Orbits, John N. Brick
Theses and Dissertations
High-altitude satellite trajectories are analyzed in the Earth-Moon circular restricted three-body problem. The equations of motion for this dynamical model possess no known closed-form analytical solution; therefore, numerical methods are employed. To gain insight into the dynamics of high-altitude trajectories in this multi-body dynamical environment, periapsis Poincare' maps are generated at particular values of the Jacobi Constant. These maps are employed as visual aids to generate initial guesses for orbital transfers and to determine the predictability of the long term behavior of a spacecraft's trajectory. Results of the current investigation demonstrate that high-altitude transfers may be performed for comparable, and …
The Impact Of Atmospheric Fluctuations On Optimal Boost Glide Hypersonic Vehicle Dynamics, Melissa A. Dunkel
The Impact Of Atmospheric Fluctuations On Optimal Boost Glide Hypersonic Vehicle Dynamics, Melissa A. Dunkel
Theses and Dissertations
A project under the management of Air Force Research Laboratory has begun development of a six degree of freedom model for use in hypersonic vehicle development and application. One area of interest is the perturbation of vehicle behavior based on atmospheric fluctuations – how the performance of the vehicle changes with respect to “hot”, “cold” and standard day conditions. The method developed to fill this need uses real-world data from the Global Forecast System to create a “hot” and “cold” day dataset to compare with the standard day model. The key parameter is atmospheric density, a value calculated over a …
Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza
Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza
Theses and Dissertations
Increasingly capable CubeSat missions require antenna with improved Radio Frequency performance over the traditional CubeSat antennas. Deployable quadrifilar helical antennas (QHA) enable an acceptable stowing volume and deploy to provide increased gain and bandwidth over traditional patch and dipole antennas. Extensive ground testing is required to ensure the antenna is space qualified and to characterize the antenna deployment in the space environment. AFIT requires a QHA to perform a future CubeSat geolocation mission and contracted Helical Communication Technologies (HCT) to design and manufacture a Shape Memory Alloy (SMA) L-band deployable QHA. Vibration, thermal vacuum, laser vibrometer, and Voltage Standing Wave …
Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess
Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess
Theses and Dissertations
For spacecraft conducting on-orbit operations, changes to the structure of the spacecraft are not uncommon. These planned or unanticipated changes in inertia properties couple with the spacecraft's attitude dynamics and typically require estimation. For systems with time-varying inertia parameters, multiple model adaptive estimation (MMAE) routines can be utilized for parameter and state estimates. MMAE algorithms involve constructing a bank of recursive estimators, each assuming a different hypothesis for the systems dynamics. This research has three distinct, but related, contributions to satellite attitude dynamics and estimation. In the first part of this research, MMAE routines employing parallel banks of unscented attitude …
Meeting The Dod’S Tactical Weather Needs Using Cubesats, Shayna K. Mckenney
Meeting The Dod’S Tactical Weather Needs Using Cubesats, Shayna K. Mckenney
Theses and Dissertations
This thesis investigates a CubeSat design that uses Commercial-Off-The-Shelf (COTS) components to capture, store, process, and downlink collected terrestrial weather data at resolutions near stat-of-the-art. The weather phenomena to be detected and transmitted in a timely manner are cloud formations, wind profiles, ocean currents, sea state, lightning, temperature profiles, and precipitation. It is hypothesized and shown that the proposed design will provide an improvement on the current U.S. tactical weather collection satellites because of the anticipated increased reliability and lowered cost to build and maintain the proposed CubeSat constellation. The methodology employed a multi-phase approach through the collective research of …
Pointing Analysis And Design Drivers For Low Earth Orbit Satellite Quantum Key Distribution, Jeremiah A. Specht
Pointing Analysis And Design Drivers For Low Earth Orbit Satellite Quantum Key Distribution, Jeremiah A. Specht
Theses and Dissertations
The world relies on encryption to perform critical and sensitive tasks every day. If quantum computing matures, the capability to decode keys and decrypt messages becomes possible. Quantum key distribution (QKD) is a method of distributing secure cryptographic keys which relies on the laws of quantum mechanics. Current implementations of QKD use fiber-based channels which limit the number of users and the distance between users. Satellite-based QKD using free-space channels is proposed as a feasible secure global communication solution. Since a free-space link does not use a waveguide, pointing a transmitter to receiver is required to ensure signal arrival. In …
Minimum-Fuel Trajectory Design In Multiple Dynamical Environments Utilizing Direct Transcription Methods And Particle Swarm Optimization, Alfredo G. Zurita Jr.
Minimum-Fuel Trajectory Design In Multiple Dynamical Environments Utilizing Direct Transcription Methods And Particle Swarm Optimization, Alfredo G. Zurita Jr.
Theses and Dissertations
Particle swarm optimization is used to generate an initial guess for designing fuel-optimal trajectories in multiple dynamical environments. Trajectories designed in the vicinity of Earth use continuous or finite low-thrust burning and transfer from an inclined or equatorial circular low-Earth-orbit to a geostationary orbit. In addition, a trajectory from near-Earth to a periodic orbit about the cislunar Lagrange point with minimized impulsive burn costs is designed within a multi-body dynamical environment. Direct transcription is used in conjunction with a nonlinear optimizer to find locally-optimal trajectories given the initial guess. The near-Earth transfers are propagated at low-level thrust where neither the …
Military Applications Of High-Altitude Satellite Orbits In A Multi-Body Dynamical Environment Using Numerical Methods And Dynamical Systems Theory, Meredith M. Wilmer
Military Applications Of High-Altitude Satellite Orbits In A Multi-Body Dynamical Environment Using Numerical Methods And Dynamical Systems Theory, Meredith M. Wilmer
Theses and Dissertations
The circular restricted three-body problem (CR3BP) is a simplified dynamical model for a satellite under the gravitational influence of both the Earth and the Moon, maintaining closer fidelity to the gravitational environment experienced by a high-altitude Earth-orbiting spacecraft than modeling in the Earth-satellite two-body problem. Resonant orbit arcs are used to determine an initial guess to input into an algorithm that computes a trajectory solution with specific design requirements and constraints. A test case uses this method to compute a lunar fly-by transfer solution requiring less than two-body transfer methods and offers an unusual pathway that adds an unpredictability element …
Multi-Cubesat Deployment Strategies: How Different Satellite Deployment Schemes Affect Satellite Separation And Detection For Various Types Of Constellations And Missions, Scott A. Biehl Jr.
Multi-Cubesat Deployment Strategies: How Different Satellite Deployment Schemes Affect Satellite Separation And Detection For Various Types Of Constellations And Missions, Scott A. Biehl Jr.
Theses and Dissertations
As economics drive an increased demand for small satellites and, consequently, an increase in the number of satellites deployed per launch, different deployment schemes and their effects on satellite dynamics must be well understood. While there are advantages to deploying multiple satellites at once, users may have trouble with tracking, identifying, and communicating with their satellites. This investigation examines the deployment of eight 3U CubeSats, and the resulting relative motion within a constellation. Both the distance between any two satellites within a constellation and the volume of a polygon encompassing a constellation are used to analyze the satellite dynamics within …
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Theses and Dissertations
A satellite QKD model was developed and validated, that allows a user to determine the optimum wavelength for use in a satellite-based QKD link considering the location of ground sites, selected orbit and hardware performance. This thesis explains how the model was developed, validated and presents results from a simulated year-long study of satellite-based quantum key distribution. It was found that diffractive losses and atmospheric losses define a fundamental trade space that drives both orbit and wavelength selection. The optimal orbit is one which generates the highest detection rates while providing equal pass elevation angles and durations to multiple ground …
Development Of A Modularized Software Architecture To Enhance Ssa With Cots Telescopes, Julian P. Mccafferty
Development Of A Modularized Software Architecture To Enhance Ssa With Cots Telescopes, Julian P. Mccafferty
Theses and Dissertations
As the catalog of Earth orbiting objects continues to grow exponentially, so too does the necessity for Space Situational Awareness (SSA). Previous work at AFIT has explored augmenting the Space Surveillance Network (SSN) by demonstrating detection and tracking of orbiting objects using Commercial-Off-The-Shelf (COTS) telescopes and Air Force generated Two-Line Element Sets (TLE). This research explores the process of developing and reengineering code into a modularized, hierarchical component architecture designed for the end user while enabling developers to continue to modify the software for future applications. Three graphical user interfaces (GUI) are compiled into standalone executable programs using MATLAB for …
Vibrational Analysis Of A 12u Chassis, Daniel G. Miller
Vibrational Analysis Of A 12u Chassis, Daniel G. Miller
Theses and Dissertations
The objective of this research is to characterize how the natural frequencies of AFIT’s CubeSat design can be controlled to meet launch vehicle requirements while increasing the internal and external volume available for payload and bus components as the chassis increases in size. A reliable Finite Element (FE) model is created and validated using NASA’s General Environmental Verification Standards (GEVS) vibrational test on the 12U chassis. The validated FE model proves that current boundary conditions and geometric properties with minimized chassis wall thicknesses to maximize usable internal and external volume maintain a first frequency of the fully loaded 12U chassis …
Analysis Of A Near Real-Time Optimal Attitude Control For Satellite Simulators, Ryan M. Patrick
Analysis Of A Near Real-Time Optimal Attitude Control For Satellite Simulators, Ryan M. Patrick
Theses and Dissertations
Dynamic optimization of spacecraft attitude reorientation maneuvers can result in significant savings in attitude determination and control system size, mass, and power. Optimal control theory is generally applied using an open loop trajectory which is vulnerable to disturbances. A closed loop implementation of optimal control has been difficult to achieve due to the computational requirements needed to quickly compute solutions to the optimal control problem. This research focuses on evaluating a near real-time optimal control (RTOC) system for large angle slew maneuvers on the Air Force Institute of Technology's spacecraft simulator called SimSat. A near RTOC algorithm computes optimal control …
Optimal Attitude Control Of Agile Spacecraft Using Combined Reaction Wheel And Control Moment Gyroscope Arrays, Cole C. Doupe
Optimal Attitude Control Of Agile Spacecraft Using Combined Reaction Wheel And Control Moment Gyroscope Arrays, Cole C. Doupe
Theses and Dissertations
This dissertation explores the benefits of combined control moment gyroscope (CMG) and reaction wheel array (RWA) actuation for agile spacecraft. Agile spacecraft are capable of slewing to multiple targets in minimum time. CMGs provide the largest torque capability of current momentum exchange actuation devices but also introduce singularity events in operation. RWAs produce less torque capability than CMGs but can achieve greater pointing accuracy. In this research, a combined RWA and CMG (RWCMG) system is evaluated using analytical simulations and hardware experiments. A closed-loop control scheme is developed which takes advantage of the strengths of each actuator set.The CMGs perform …