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Articles 1 - 15 of 15
Full-Text Articles in Engineering
Spacex: Breaking The Barrier To The Space Launch Vehicle Industry, Matthew M. Liskowcyz
Spacex: Breaking The Barrier To The Space Launch Vehicle Industry, Matthew M. Liskowcyz
Theses and Dissertations
The Space Launch Vehicle (SLV) industry has been around for a long time, but few companies have managed to enter this industry. SpaceX was founded only 10 years ago, but it has managed to become a leader in the U.S. industry and a dominant player worldwide. The purpose of this thesis research is to discover what it took for SpaceX to break into this tightly controlled industry. A qualitative analysis was performed to compare SpaceX to companies that overcame the barriers of entry for their respective industries. SpaceX, like FedEx, could implement a unique technique to the industry and find …
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 …
Orbit Determination Using Vinti's Solution, Steven P. Wright
Orbit Determination Using Vinti's Solution, Steven P. Wright
Theses and Dissertations
Orbital altitudes congested with spacecraft and debris combined with recent collisions have all but negated the Big Sky Theory. As the sheer number of orbital objects to track grows unbounded so does interest in prediction methods that are rapid and minimally computational. Claimed as the \other solvable solution, the recently completed solution too orbital motion about the earth, based on Vinti's method and including the major effects of the equatorial bulge, opens up the prospect of much more accurate analytical models for space situational awareness. A preliminary examination of this solution is presented. A numerical state transition matrix is found …
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 …
Space Object Self-Tracker On-Board Orbit Determination Analysis, Stacie M. Flamos
Space Object Self-Tracker On-Board Orbit Determination Analysis, Stacie M. Flamos
Theses and Dissertations
Due to the United States' growing dependence on space based assets and the in- creasing number of resident space objects (RSO), improvement of Space Situational Awareness (SSA) capabilities is more necessary than ever. As a way to aid in this need, the Air Force Institute of Technology (AFIT) is developing the Space Object Self-Tracker (SOS) as a proof-of-concept experimental satellite for RSO precision tracking and collision avoidance system in Low Earth Orbit (LEO). Specifically, SOS will use Global Positioning System (GPS) position estimates for on-board orbit de- termination. Currently, SOS will use the Simplified General Perturbations-4 (SGP4) algorithm as its …
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 …
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 …
Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt
Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt
Theses and Dissertations
When considering the neutral constituents in the upper thermosphere and exosphere, helium needs to be accounted for as a major species. As detailed by Emmert [2015], most first-principle models do not consider helium a major species when solving for diffusion and collisions within the atmosphere. First-principle, physics-based models hold a distinct advantage of seasonal variations and spatial resolution over empirical models which leads to a more realistic depiction of the atmosphere. The National Center for Atmospheric Research’s (NCAR) self-consistent, physics-based Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) has been updated to take into account this neutral constituent in its calculations. The major …