Astrodynamics Commons^™

Mean Performance Optimization Of An Orbiting Distributed Aperture By Warped Aperture Image Plane Comparisons, Timothy W. Parker

Theses and Dissertations

This work models the aggregate performance of satellite receiver formations functioning as orbiting interferometers as compared to filled apertures of similar geometries. These models facilitate selecting initial conditions for formations such that their control-free dynamics yield interferometry performance with minimal errors as compared to the filled apertures. The solution method draws on the dynamic models of an orbiting planar satellite formation to define the size and shape of a reference aperture and to define the degrees of freedom for the formation members. The paths of formation elements yield geometries for which the aggregate performance of the array of discrete receivers …

Estimation Of Relative Satellite Formation Elements In Near Circular Orbits, Ralph E. Bordner Iii

Theses and Dissertations

Precise relative position determination of satellite formation elements in near circular orbits is the focus of this thesis. A Bayes filter is used for the estimator with the dynamics solution obtained by solving the time periodic, linearized system via Floquet theory. This approach is similar to that of the traditional Clohessy-Wiltshire treatment, however much more of the system's behavior is retained by using a linear, time periodic system. The dynamics model includes all zonal harmonics of the Earth as well as sectoral, tesseral, and air drag perturbations. The filter algorithm was fed three types of simulated measurements: relative Carrier-Phases Differential …

Solar Radiation Pressure Modeling Issues For High Altitude Satellites, Dayne G. Cook

Theses and Dissertations

Current satellite orbit propagation techniques employ a solar radiation pressure model that makes simplifying assumptions concerning the satellite and its orbital geometry. Solar radiation pressure, a non-gravitational perturbation, significantly affects satellite motion at high altitudes. The model currently in use by the Air Force for orbit determination includes the following assumptions: a constant cross-sectional area projected to the Sun, cylindrical Earth shadow for eclipse, and specular reflection. In reality, the satellite's cross-sectional area with respect to the Sun constantly changes, the Earth's shadow is conical, and reflection is both specular and diffuse. Additionally, the solar flux received at the Earth …

Navigation Of Satellite Clusters, Jeffrey S. Davis

Theses and Dissertations

The relative position determination of a cluster of satellites in near circular orbit was investigated in previous thesis work. The purpose of this thesis is to extend the concept to cover absolute position determination. A Bayes filter is used for the estimator with dynamics based on the two-body problem extended to account for J2 perturbations. Measurements consist of combining Global Positioning System (GPS) data for each satellite and range data between the satellites. Simulations were conducted investigating the accuracy obtainable when combining the measurements for input into the filter. Performance results consist of comparing the magnitude of the time error …

Optimal Non-Coplanar Launch To Quick Rendezvous, Gregory B. Sears

Theses and Dissertations

The purpose of this study was to determine the feasibility of launching a Delta Clipper-like vehicle on an optimal, non-coplanar trajectory to rendezvous with an earth orbiting object in one orbit or less. The focus of the research was to determine what such a trajectory would look like, and to determine the cost, in payload mass, of flying such a trajectory. A model for the ascent trajectory was developed using the dynamics equations of motion, an atmosphere model, and an aerodynamic model for the DC-Y concept vehicle. A boundary value problem was posed and solved for a coplanar rendezvous. The …

Orbit Estimation Using Track Compression And Least Squares Differential Correction, Vincent J. Chioma

Theses and Dissertations

This thesis develops two methods of compressing a track of radar observations of a satellite into a single state vector and associated covariance matrix, and a method of estimating orbits using results from multiple tracks. The track compression uses least squares differential correction to determine a state vector at the central observation time. The resulting state vectors and covariance matrices are then used to estimate the satellite's orbit, also using least squares differential correction. Numerical integration using two-body, J₂ and an atmospheric drag model is used to represent the dynamics. This orbit estimation produces a state vector which includes …

Relative Equilibria Of A Rigid Satellite In A Central Gravitational Field, Jeffrey A. Beck

Theses and Dissertations

We apply noncanonical Hamiltonian methods to examine relative equilibria of a rigid body in a central gravitational field. These equilibria correspond to fixed points of a reduced set of equations expressed in a rotating frame and are representative of an orbiting satellite with fixed attitude relative to an observer rotating at the orbital rate. Our objective is to clarify the relationship between the classical approximation and a recent noncanonical Hamiltonian treatment. In contrast to the classical approximation, the orbital and attitude equations of motion for the noncanonical system remain coupled and the general solution is a circular orbit for which …

Optimal Continuous-Thrust Orbit Transfers, James D. Thorne

Theses and Dissertations

The minimum time orbital transfer problem for spacecraft with steerable, continuous thrust of constant magnitude may be solved using Euler-Lagrange theory, which leads to the optimal control law in terms of Lagrange multipliers. However, the initial values of the Lagrange multipliers are not known from the orbital boundary conditions. Using analytical and empirical results, the optimal initial costates are modeled as functions of the problem parameters which are the initial thrust acceleration, A, and the final orbit radius, H, in canonical units. For circle to circle, coplanar orbit transfers, these approximate initial costate models lead to convergence in the shooting …

Full Lyapunov Exponent Placement In Reentry Trajectories, Michael H. Platt

Theses and Dissertations

This study investigated the ability to control the chaotic reentry of a Delta-Clipper like vehicle by setting the values of initial arid final principal dynamical directions as well as the Lyapunov exponents. A model of the original controlled reentry vehicle was created through the use of the equations of motion in conjunction with an atmospheric model. A modified linear quadratic regulator allowed the set up of a boundary value problem which specified the Lyapunov exponents and determined the gain matrix as a function of time. The gain matrix can eventually be used in the control system of the vehicle.

Analysis Of Gravity-Gradient Satellite Attitude Inversion, Jules-Francois D. Desamours

Theses and Dissertations

The purpose of this research is to understand and describe the process by which the 1986 Polar BEAR gravity- gradient research satellite of John Hopkins University/Applied Physics Laboratory achieved an orbital attitude correction (re-inversion) from an inverted orientation through the utilization of its momentum wheel. Understanding this process provides an analytical foundation from which a universal attitude inversion process for other gravity-gradient satellites with similar anomalous motions may be sought and developed. The equations of motion for a gravity-gradient satellite with a momentum wheel are derived and implemented in FORTRAN for simulation of the dynamics of the spacecraft. Several re-inversion …

Optimization Of A Nutation Damper Attached To A Spin-Stabilized Satellite, Brady P. Hauboldt

Theses and Dissertations

This study uses linearized equations of motion for a rigid body with an attached spring-mass-damper to maximize the decay rate of a satellite's coning motion. An analysis of the numerical eigenvalues is presented which leads to an optimal relationship between relevant parameters: damper placement, spring constant, damping coefficient, system moments of inertia, and damper mass fraction. The coupled system's eigenvalues do not provide truly critical damping, thus the real eigenvalue parts are minimized in order to achieve damping which requires the minimum amount of time. A comparison between this optimal design method and a classical method concludes a noticeable improvement …

Compression Of A Radar Track Of A Near Earth Satellite Into An Earth Centered Inertial State Vector Using Least Squares Differential Correction, Garry L. Hall

Theses and Dissertations

This study investigated the use of a least squares differential corrector to compress the information contained in a single radar track of a Near Earth satellite into a six element, Earth Centered Inertial state vector and associated covariance matrix. Observations were generated using a truth model program based on two body, J2 geopotential, and atmospheric drag dynamics and consisted of simulated range, azimuth and elevation. Random Gaussian noise was added to the data to simulate real world random errors. The orbital dynamics used in the estimator consisted of two body and J2 geopotential effects which were approximated using a Taylor …

The Modal Solution To The Moon's Orbit Using Canonical Floquet Perturbation Theory, Kurt A. Vogel

Theses and Dissertations

Using the restricted three body problem, the equations of motion EOM and Hamiltonian are computed for the moons orbit in physical variables. A periodic orbit is found in the vicinity of the moons orbit, and classical Floquet theory is applied to the periodic orbit to give stability information and the complete solution to the equations of variation. Floquet theory also supplies a transformation from physical variables to modal variables. This transformation to modal variables is made canonical by constraining the initial transformation matrix to be symplectic. Actual lunar data is used to calculate the modes for the real moons orbit. …

An Approximate Solution For The Spinup Dynamics Of Near Axisymmetric Axial Gyrostats Using The Method Of Multiple Scales, Stewart J. Kowall

Theses and Dissertations

Approximate solutions for the spinup of a near axisymmetric gyrostat are derived using the straightforward expansion method and the method of multiple scales. Two method of multiple scale solutions are presented. The first is derived using cartesian coordinates while the second is derived using cylindrical coordinates. The multiple scales solutions are compared to numerically integrated results for oblate and prolate configurations. A comparison for flat spin recovery is also accomplished. Excellent results are obtained for oblate configurations. Trajectory separatrix crossings hindered the results for prolate configurations and flat spin recoveries.

Weatherford Air Show And General Thomas P. Stafford Museum Dedication, City Of Weatherford

Programs

This is a program from the 1987 Weatherford Air Show and General Thomas P. Stafford Museum Dedication in Weatherford, Oklahoma.

Unless stated otherwise within this repository collection, all materials are shared under the following Creative Commons license: [Creative Commons Attribution-NonCommercial 4.0 International License].

Second Annual Great Oklahoma Balloon Race & Airshow Gala Reception, Clarence E. Page Oklahoma Air And Space Museum

Programs

This is the program from the second annual Great Oklahoma Balloon Race & Airshow Gala Reception in honor of Astronaut, Lt. General Thomas P. Stafford. The event was held at the Clarence E. Page Oklahoma Aviation and Space Hall of Fame and Museum in the Kirkpatrick Center in OKC, OK, on Thursday, August 16th, 1984.

Unless stated otherwise within this repository collection, all materials are shared under the following Creative Commons license: [Creative Commons Attribution-NonCommercial 4.0 International License].

Modal Control Of An Unstable Periodic Orbit, William Wiesel, William Shelton

Faculty Publications

We apply Floquet theory to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time periodic linear system, which is augmented by a time periodic control term. We show that this can be done such that a) the application of control produces only inertial accelerations, b) positive real Poincare exponents are shifted into the left half-plane, and c) the shift of the exponent is linear with control gain. We apply these developments to an unstable orbit near the Earth-Moon L₃ point perturbed by the Sun. Finally, …

Apollo/Soyuz Tv Guide: "Soyuz, Soyuz, This Is Apollo...", Bob Button

Articles

This is a TV Guide from 1975 that features a story about the televised Apollo/Soyuz mission.

Unless stated otherwise within this repository collection, all materials are shared under the following Creative Commons license: [Creative Commons Attribution-NonCommercial 4.0 International License].

Https://Www.Newhealthera.Com/Holistic-Bliss-Keto/, Holistic Bliss Keto

Holistic Bliss Keto