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Articles 91 - 120 of 165
Full-Text Articles in Space Vehicles
Finite Element Model Optimization Of The Falconsat-5 Structural Engineering Model, Cole C. Doupe
Finite Element Model Optimization Of The Falconsat-5 Structural Engineering Model, Cole C. Doupe
Theses and Dissertations
Space launch vehicles produce tremendously harsh environments for their payloads. One of the worst contributors to this harsh environment is vibration. Launch vehicle contractors require accurate dynamic models in order to perform coupled loads analyses with each payload to mitigate risks. Accurate predictions of the dynamic response of the payload are not achieved easily. The Finite Element (FE) method has proven to be the best approach in creating accurate dynamic models of complex structures. To improve the agreement between an FE model and the structure it represents, a common practice is to `tune' or adjust parameters of the FE model …
Characterizing The Exhaust Plume Of The Three-Electrode Micro Pulsed Plasma Thrusters, Myeongkyo Seo
Characterizing The Exhaust Plume Of The Three-Electrode Micro Pulsed Plasma Thrusters, Myeongkyo Seo
Theses and Dissertations
Three-electrode micro-PPTs are a new version of two electrode micro-PPTs devices. Performance predictions and contamination expectations are essential characteristics needed by satellite designers. In order to focus on thruster specific impulse, thrust and efficiency, measuring the exhaust velocity or impulse bit and propellant consumption rate is essential. While this is not always possible to measure directly, focusing on the ejected mass from the PPT provides significant information allowing determination of these performance statistics. Specifically, focusing on exhaust angle distribution and velocity of the exhaust particles is the emphasis of this work. The results show that the three-electrode micro-PPT is more …
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
Theses and Dissertations
The Operational Responsive Space (ORS) program requires flexible and responsive satellites to meet user’s needs. Traditional satellite design methods are typically iterative processes that optimize individual components, subsystems, and ultimately the entire satellite. This study focuses on developing a new approach for creating Responsive Satellites (RS) from Plug-and-Play (PnP) components. The aim is to create an approach that quickly evaluates a wide variety of possible satellite configurations and identify the best configurations that meet the user’s needs and constraints. Satellite configurations are created by matching locations on the satellite structure with PnP components. Various constraints are derived from the user’s …
Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Benjamin T. Harder
Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Benjamin T. Harder
Theses and Dissertations
The United States military is exploring the use of nanocomposite materials for satellite structural applications. Current composite spacecraft structures are nonconductive and must have expensive shielding materials applied in order to protect the spacecraft from catastrophic damage that can be caused by electromagnetic interference (EMI) and/or electrostatic discharge (ESD) which are characteristics of the space environment. Conductive nanocomposites are being developed for spacecraft structures that will provide ESD and EMI shielding protection without the need for expensive secondary shielding materials. This thesis studied one such material consisting of M55J/RS-3 composite combined with nickel nanostrands™. Four different configurations were tested for …
Space Based Satellite Tracking And Characterization Utilizing Non-Imaging Passive Sensors, Bradley R. Townsend
Space Based Satellite Tracking And Characterization Utilizing Non-Imaging Passive Sensors, Bradley R. Townsend
Theses and Dissertations
A technique is developed to determine the orbit of a sunlight illuminated satellite passing through the field-of-view of a sensor platform in a Highly Elliptical Orbit (HEO) and Geosynchronous orbit (GEO). The technique develops two different methods of initial orbit determination. The first relies on the Gauss initial orbit determination method to develop an estimate of the state from angular data. The second method relies on positional data of the target relative to the Earth’s background to determine an estimate of the state. These estimates are then refined in a non-linear least squares routine. This estimate of the state is …
Final Development, Testing, And Flight Preparation Of The Rigidizable Get-Away-Special Experiment (Rigex), Zachary R. Miller
Final Development, Testing, And Flight Preparation Of The Rigidizable Get-Away-Special Experiment (Rigex), Zachary R. Miller
Theses and Dissertations
The purpose of this research is to support the final development of the Rigidizable Inflatable Get-Away-Special Experiment (RIGEX). The RIGEX program is an experimental initial step in developing large-scale rigidizable inflatable structures, which can be utilized in space applications. The primary intent of RIGEX is to verify and validate ground testing of inflation and rigidization methods for inflatable space structures against a zero-gravity space environment. This is performed by designing a Canister for All Payload Ejections (CAPE) experiment to collect data on space rigidized structures for validation of ground testing methods. The results presented in this thesis provide documentation needed …
Controller Design For Accurate Antenna Pointing Onboard A Spacecraft, Victor M. Barba
Controller Design For Accurate Antenna Pointing Onboard A Spacecraft, Victor M. Barba
Theses and Dissertations
Controller design for a spacecraft mounted flexible antenna is considered. The antenna plant model has a certain degree of uncertainty. Additionally, disturbances from the host spacecraft are transmitted to the antenna and need to be attenuated. The design concept explored herein entails feedforward control to slew the antenna. Feedback control is then used to compensate for plant uncertainty and to reject the disturbance signals. A tight control loop is designed to meet performance specifications while minimizing the control gains. Simulations are conducted to show that the integration of feedforward control action and feedback compensation produces better responses than the implementation …
Optimal Spacecraft Attitude Control Using Aerodynamic Torques, Michael L. Gargasz
Optimal Spacecraft Attitude Control Using Aerodynamic Torques, Michael L. Gargasz
Theses and Dissertations
This thesis introduces a method of three-axis spacecraft attitude control using only aerodynamic torques. Attitude actuation is achieved using four control panels mounted on the rear of a cubical spacecraft bus. The controller consists of an outer loop using linear state feedback to determine desired control torque and an inner loop to choose appropriate control panel angles. The inner loop uses a Jacobian-based approach to invert the nonlinear relationship between panel angles and generated torque. Controller performance is evaluated via simulations, which show that three-axis control is possible over a range of initial angles and angular rates. The analysis used …
Reconstructing Spectral Scenes Using Statistical Estimation To Enhance Space Situational Awareness, Travis F. Blake
Reconstructing Spectral Scenes Using Statistical Estimation To Enhance Space Situational Awareness, Travis F. Blake
Theses and Dissertations
A new sensor, the Advanced Electro-Optical System (AEOS) Spectral Imaging Sensor (ASIS) has been developed at the Maui Space Surveillance Complex (MSSC). ASIS is capable of collecting resolved imagery of space objects in 10's-100's of spectral bands while using an adaptive optics system. However, the stringent requirements of collecting ground-based images requires a sensor that induces spectral blurring. Post-processing algorithms to remove this blurring are required to fully exploit these spectral images. This research focuses on developing the reconstruction algorithms, based on proven estimation theories, required to spectrally deblur the images collected from ASIS. Additionally, the research will expand the …
Lightweight In-Plane Actuated Deformable Mirrors For Space Telescopes, Michael J. Shepherd
Lightweight In-Plane Actuated Deformable Mirrors For Space Telescopes, Michael J. Shepherd
Theses and Dissertations
This research focused on lightweight, in-plane actuated, deformable mirrors, with the ultimate goal of developing a 20- meter light gathering aperture for space telescopes. The 0.127 meter diameter deformable mirror small scale testbed was modelled infinite elements using MSC.Nastran software and then used as a basis for a quasi-static controller. Experimental tracking of Zernike tip, tilt, and defocus modes was accomplished. The analytical solutions to plate-membrane and beam-string ordinary differential equations were developed. A simplified approach to modelling the axisymmetric cases was also presented. A novel static control strategy, the Modal Transformation Method, was developed to form Zernike surfaces within …
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Theses and Dissertations
This dissertation assesses the utility of tethered satellite formations for the space-based remote sensing mission. Energy dissipation is found to have an adverse effect on foundational rigid body (Likins-Pringle) equilibria. It is shown that a continuously earth-facing equilibrium condition for a fixed-length tethered system does not exist since the spin rate required for the proper precession would not be high enough to maintain tether tension. The range of required spin rates for steady-spin motion is numerically defined here, but none of these conditions can meet the continuously earth-facing criteria. Of particular note is the discovery that applying certain rigid body …
Dual Fine Tracking Control Of A Satellite Laser Communication Uplink, Louis A. Noble
Dual Fine Tracking Control Of A Satellite Laser Communication Uplink, Louis A. Noble
Theses and Dissertations
A dual fine tracking control system (FTCS) is developed for a single aperture optical communication receiver to compensate for high frequency disturbances affecting tracking of two incident laser communication beams. The optical communication receiver resides within a payload module aboard a geosynchronous satellite, while each laser communication transmitter is housed within a module aboard a high altitude unmanned aerial vehicle (UAV). In addition to platform specific disturbances, the impact of atmospheric optical disturbances affecting tracking error are investigated. The system dynamics and FTCS are modeled and evaluated in MATLAB and SIMULINK. An optimal controller is developed to mitigate these disturbances …
Structural Analysis Of The Rigidizable Inflatable Get-Away-Special Experiment, Anna E. Gunn-Golkin
Structural Analysis Of The Rigidizable Inflatable Get-Away-Special Experiment, Anna E. Gunn-Golkin
Theses and Dissertations
The purpose of this research was to validate the structural integrity of the Rigidizable Inflatable Get-Away-Special Experiment (RIGEX) and make appropriate improvements to the design, motivated by static and dynamic analysis results. RIGEX is designed to advance the use of rigidizable inflatable structures in the space environment by providing three sets of on-orbit test data on the structural characteristics of three thermoplastic composite tubes. This thesis discusses the RIGEX structural analysis. The term structural analysis refers to the development of a detailed finite element model and the tests for which the model was used. The finite element model provided an …
Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr.
Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr.
Theses and Dissertations
This research effort develops a program using MATLAB to solve the equations of motion for atmospheric reentry and analyzes the validity of the program for use as a tool to expeditiously predict reentry profiles. The reentry vehicle is modeled as a point mass with constant aerodynamic properties as defined by the user. The equations of motion for reentry are based on the two-body problem. The atmosphere is modeled as a single layer exponentially decreasing in density. The MATLAB program has the ability to derive the initial trajectory conditions from the position and velocity relative to the rotating surface of the …
The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey
The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey
Theses and Dissertations
This research is designed to demonstrate that a change in satellite propellant can be determined using measured moments of inertia (MOI) from a satellite. Because satellites are currently incapable of being refueled in orbit it is important to have multiple methods to determine the remaining fuel onboard. This research can also support satellite operator selection of control-system gains to improve performance or recover the spacecraft. To meet the research objectives, new mathematical models of the Air Force Institute of Technology's Simulated Satellite (SimSat) were developed. These models were created using dynamic response analysis techniques on the reaction wheel and SimSat …
Cost Comparison Of Expendable, Hybrid And Reusable Launch Vehicles, Greg J. Gstattenbauer
Cost Comparison Of Expendable, Hybrid And Reusable Launch Vehicles, Greg J. Gstattenbauer
Theses and Dissertations
This study compares the developmental, production, and maintenance costs (DPM) of twostage- to-orbit (TSTO) expendable (ELV), hybrid (HLV), and reusable (RLV) launch systems. This comparison was accomplished using top level mass and cost estimating relations (MERs, CERs). Mass estimating relationships were correlated to existing launch system data and ongoing launch system studies. Cost estimating relations were derived from Dr. Dietrich Koelle's 'Handbook of Cost Engineering for Space Transportation Systems'. Hybrid launch vehicles appear to be preferable if current or modest increases in launch rates are projected while reusable launch vehicles appear preferable for large projected increases in launch rates.
Comparative Analysis Of Two-Stage-To-Orbit Rocket And Airbreathing Reusable Launch Vehicles For Military Applications, Joseph M. Hank
Comparative Analysis Of Two-Stage-To-Orbit Rocket And Airbreathing Reusable Launch Vehicles For Military Applications, Joseph M. Hank
Theses and Dissertations
The Department of Defense (DoD) has identified operationally responsive, low-cost access to space as vital to maintaining U.S. military supremacy. Reusable Launch Vehicles (RLVs) will allow the U.S. to keep a technological advantage over our adversaries, and advances in airbreathing propulsion technology have made it feasible for use in space launch vehicles. This study considers two-stage-to-orbit (TSTO) RLV configurations, each using combinations of propulsion including pure rocket, pure turbine, rocket-based-combined-cycle (RBCC), and turbine-based-combined-cycle (TBCC) for the both stages. This study explores the advantages of airbreathing propulsion in those key areas when compared to a baseline configuration, using vehicle empty mass …
A Discrete Event Simulation Model For Evaluating Air Force Reusable Military Launch Vehicle Prelaunch Operations, Adam T. Stiegelmeier
A Discrete Event Simulation Model For Evaluating Air Force Reusable Military Launch Vehicle Prelaunch Operations, Adam T. Stiegelmeier
Theses and Dissertations
As the control and exploitation of space becomes more important to the United States military, a responsive spacelift capability will become essential. Responsive spacelift could be defined as the ability to launch a vehicle within hours or days from the time a launch order is given, instead of the weeks or months it takes currently. As the Air Force contemplates moving toward a reusable military launch vehicle (RMLV) capability, it faces key design and ground processing decisions that will affect the vehicle regeneration timeline. This thesis develops a computer simulation model that mimics RMLV prelaunch operations-those activities that take place …
Discrete Event Simulation Model Of The Ground Maintenance Operations Cycle Of A Reusable Launch Vehicle, John T. Pope Iii
Discrete Event Simulation Model Of The Ground Maintenance Operations Cycle Of A Reusable Launch Vehicle, John T. Pope Iii
Theses and Dissertations
The Air Force uses a family of expendable launch vehicles to meet its spacelift needs. Unfortunately, this method is not responsive: months of preparation are typically required and launch costs are high. Consequently, the Air Force seeks a reusable military launch vehicle that can be launched inexpensively and quickly regenerated between flights. Air Force Research Laboratory personnel desire a tool to help evaluate candidate designs and perform tradeoff studies necessary to acquire a launch vehicle that will achieve Air Force goals. The objective of this research was first to develop a conceptual model of maintenance operations needed to regenerate a …
Detailed Design Of The Rigidizable Inflatable Get-Away-Special Experiment, Jeremy S. Goodwin
Detailed Design Of The Rigidizable Inflatable Get-Away-Special Experiment, Jeremy S. Goodwin
Theses and Dissertations
The Rigidizable Inflatable Get-Away-Special Experiment is a Space Shuttle experiment that will study the effects of the zero-gravity space environment on the deployment and modal analysis of three inflatable and rigidizable tubes using a sub-Tg rigidization technique. In 2004, RIGEX was transitioned from the Space Shuttle's Get-Away-Special (GAS) canister to its Canister for All Payload Ejections (CAPE), requiring several modifications to the design. The results of these modifications, along with further refinements made to previous efforts, combine to form the detailed design of the experiment. In addition to the design modifications, analyses were conducted to determine the containment capabilities of …
Development And Testing Of An Inflatable, Rigidizable Space Structure Experiment, Sarah K. Helms
Development And Testing Of An Inflatable, Rigidizable Space Structure Experiment, Sarah K. Helms
Theses and Dissertations
Many recent space technology concepts require large space structures such as solar arrays and large aperture antennas; however, tight constraints on payload mass and volume often preclude their launch. Employing inflatable, rigidizable structures can reduce mass and volume while providing sufficient packing flexibility and structural stiffness. AFIT has developed RIGEX to flight-test this type of structure. RIGEX will test the deployment and structural characteristics of three thermoplastic composite Sub-Tg tubes. Once launched on the Space Shuttle in 2007, the spaceflight results will be compared to lab data to validate on-orbit reliability and ground test methods. This paper documents three main …
Control Demonstration Of A Thin Deformable In-Plane Actuated Mirror, Gina A. Peterson
Control Demonstration Of A Thin Deformable In-Plane Actuated Mirror, Gina A. Peterson
Theses and Dissertations
Current imaging satellites are limited in resolution and coverage area by the aperture size of their primary optical mirror. To get a large optical mirror into space, current launch weight and size restrictions must be overcome. Membrane-like optical mirrors can overcome these restrictions with their very lightweight and flexible properties. However, thin, deformable membrane mirrors are very susceptible to the space environment and require active control for surface stabilization and shaping. The primary goal of this research is to demonstrate that an in-plane actuated membrane-like deformable optical mirror can be controlled to optical wavelength tolerances in a closed-loop system. Fabrication …
Performance Study Of Staging Variable On Two-Stage-To-Orbit Reusable Launch Vehicles, James K. Nilsen
Performance Study Of Staging Variable On Two-Stage-To-Orbit Reusable Launch Vehicles, James K. Nilsen
Theses and Dissertations
The purpose of this research is to investigate the effects of staging variables on Two-Stage-To-Orbit reusable launch vehicles, specifically, the question of what measurable factors play important roles in staging performance. Three different configurations (Rocket-Rocket, Turbojet-Rocket and Turbine Based Combined Cycle-Rocket) were considered. The software, Program to Optimize Simulated Trajectories (POST), was used to analyze these configurations. Vehicle coasting time, staging dynamic pressure and staging Mach number were all varied to determine their influence on the final payload.
A Numerical Analysis For Passive Attitude Stabilization Using A Tethered Balloon On A Gravity Gradient Satellite, Ernest Matias Maramba
A Numerical Analysis For Passive Attitude Stabilization Using A Tethered Balloon On A Gravity Gradient Satellite, Ernest Matias Maramba
Theses and Dissertations
This research effort analyzes the fundamental dynamics governing a satellite with a gravity gradient boom and a tethered balloon. Satellites that use gravity gradient booms for passive attitude control are characterized by undamped pitch oscillations and no roll control. The tethered balloon acts as a high drag device that accounts for the most drag on the satellite system. By attaching a drag device, the system resists rolling movements while also damping oscillations. This could potentially be a cost effective method for increasing satellite stabilization. The goal of this research is to model the dynamics and determine the feasibility of a …
Timing Of Increasing Electron Counts From Geosynchronous Orbit To Low Earth Orbit, Kirk M. Olson
Timing Of Increasing Electron Counts From Geosynchronous Orbit To Low Earth Orbit, Kirk M. Olson
Theses and Dissertations
Under certain conditions, high energy electron fluxes can increase over short periods of time in the outer radiation belt and diffuse to low altitudes. Sudden increases of high energy electron densities at low altitudes can drastically damage unsuspecting low-earth-orbit satellites. The progression of electron flux increases from a geosynchronous orbit to low-earth orbit during an electron event is somewhat unknown. If the beginning of electron flux increases at low-earth-orbits could be anticipated, warnings could be issued to space system operators allowing time to take proper measures to protect and minimize satellite damage extending satellite lifetimes and space mission operations. The …
Attitude Model Of A Reaction Wheel/Fixed Thruster Based Satellite Using Telemetry Data, Jason E. Smith
Attitude Model Of A Reaction Wheel/Fixed Thruster Based Satellite Using Telemetry Data, Jason E. Smith
Theses and Dissertations
Attitude determination of satellites is normally the job of inertial instruments, such as gyroscopes, or through sensing instruments, such as star trackers or Global Positioning Satellites (GPS). Satellite health monitoring systems watch and determine if the satellite deviates from its normal operating attitude orientation. Knowing the orientation of a satellite is essential in being able to control it in order to complete the satellite's designated mission. While there are a multitude of ways to determine a satellite's orientation, very little research has been done on determining if the attitude of a satellite can be determined directly from telemetry data of …
Weight Analysis Of Two-Stage-To-Orbit Reusable Launch Vehicles For Military Applications, Richard A. Caldwell
Weight Analysis Of Two-Stage-To-Orbit Reusable Launch Vehicles For Military Applications, Richard A. Caldwell
Theses and Dissertations
In response to Department of Defense (DoD) requirements for responsive and low-cost space access, this design study provides an objective empty weight analysis of potential reusable launch vehicle (RLV) configurations. Each two-stage-to-orbit (TSTO) RLV has a fixed payload requirement of 20,000 lbf to low Earth orbit. The propulsion systems considered in this study include pure rocket, pure turbine, rocket-based-combined-cycle (RBCC), and turbine-based-combined-cycle (TBCC). The hydrocarbon dual-mode scramjet (DMSJ) engines used in the RBCC and TBCC propulsion systems represent possible applications of the current research being performed in the U.S. Air Force HyTech program. Two sensitivity analyses were then performed on …
Technical Feasibility Of Loitering Lighter-Than-Air-Near-Space Maneuvering Vehicles, Eric R. Moomey
Technical Feasibility Of Loitering Lighter-Than-Air-Near-Space Maneuvering Vehicles, Eric R. Moomey
Theses and Dissertations
The near-space region of earth's atmosphere above 20 kilometers altitude is greatly underutilized. Lighter-than-air maneuvering vehicles, or airships, using the principle of buoyancy can take advantage of this region to become potential platforms for precision navigation, environmental monitoring, communication relays, missile warning, surveillance, and weapon delivery. These vehicles purportedly provide persistent coverage over large areas of the earth's surface at substantially lower costs than orbiting satellites. This study investigated the technical requirements to loiter an operational payload within this high altitude region using a lighter-than-air maneuvering platform. A parametric analysis was conducted to identify the critical technologies needed to achieve …
Investigation Of Aerobraking To Return The Space Maneuver Vehicle To Low Earth Orbit From Geotransfer Orbit, Benjamin M. Berlin
Investigation Of Aerobraking To Return The Space Maneuver Vehicle To Low Earth Orbit From Geotransfer Orbit, Benjamin M. Berlin
Theses and Dissertations
This study investigated the use of ballistic and Double-Dip'' aerobraking reentry to return the Space Maneuver Vehicle (SMV) from geotransfer orbit in no more than two atmosphere passes. Lift and drag accelerations were applied to the two-body problem when either of their magnitudes exceeded 1/1000 g. Lift and drag coefficients, along with the SMV model, were taken from Investigation of Atmospheric Reentry for the Space Maneuver Vehicle by Captain McNabb, AFIT/GA/ENY/04-M03. Target perigees were formulated using the two-body problem. The orbit from each target perigee was numerically integrated around a planar earth model using a fourth order Runge-Kutta method. Ballistic …
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Theses and Dissertations
Satellite formations or distributed satellite systems provide advantages not feasible with single satellites. Efficient operation of this platform requires the use of optimal control of the entire satellite formation. While the optimal control theory is well established, only a very simple dynamical system affords an analytical solution. Any practical optimal control problem solves the resulting two-point boundary value (TPBV) problem numerically. The relative satellite dynamics using Hill's coordinate system and approximations made by Clohessy and Wiltshire, combined with body-fixed thruster control, result in a linearized dynamic system. This dissertation provides the analysis for the minimum time satellite formation control by …