Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 23 for “"circular orbits"”.
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Optimum transfers from circular orbits.
Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.
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Feasibility of Circular Orbits for Proximity Operations in Strongly Perturbed Environments around Uniformly Rotating Asteroids
… This research studies different types of orbits that have been performed to date around asteroids and how they can be reworked to require less control effort. Different types of missions that have been sent to asteroids are discussed, as well as the equipment needed for those missions. The …
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Orbital stability in a classical pilot-wave system
… this quantisation in terms of the stability of circular orbits arising in the presence of a rotating frame and a central force. We find that orbital quantisation is most pronounced when the waves generated by each bounce decay slowly. The wave decay rate, in turn, is related to the concept of …
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Gauge/Gravity Duality: Recovering the Bulk from the Boundary using AdS/CFT
… data. We find that if the spacetime admits null circular orbits, the bulk geometry can only be recovered from the boundary, down to the radius of null circular orbits. We illustrate this for various analytic and numerical boundary functions of endpoint separation of null and spacelike geodesics. …
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The Orbital Structure of Galaxies and Dark Matter Halos in N-Body Simulations
… in a spherical dark matter halo move on circular orbits we can predict the amount of contraction of the dark matter halo during the slow formation of the disk with an adiabatic approximation. We find in N-body simulations that the adiabatic approximation is valid for all realistic mass …
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LOW-THRUST CONTROLLER FOR SLOT-BASED SATELLITE CONSTELLATIONS
… controllers for LEO satellites operating in near-circular orbits with low-thrust engines. This is done using a linearized model of the dynamics under the Earth gravitational potential and the atmospheric drag.
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Optimization of satellite constellation deployment strategy considering uncertain areas of interest
… assumed to be Flower constellation with circular orbits, provides a regional coverage of the current area of interest as well as additional coverage for the potential future areas of interest. The proposed multi-stage satellite constellation enables the constellation designer to react …
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Eccentricity of Merging Neutron Star Binaries: Searches, Parameter Estimation, and Future Prospects
… for neutron star binaries that have an eccentric orbits when their gravitational waves enter the sensitive band of Advanced LIGO and Virgo. For the detected binary neutron star mergers GW170817 and GW190425, Bayesian parameters estomation is used to constrain the binary's orbital eccentricity. …
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Modeling Satellite Formations In The Presence Of Perturbations
… done in this area confine their research to circular orbits, with and without perturbation effects. This study will investigate apply orbital dynamic equations to the problem of maintaining satellite formations in both circular and elliptical orbits, with and without the presence of J2 …
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CLOSeSat : Perigee-lowering techniques and preliminary design for a small optical imaging satellite operating in very low earth orbit
… reduce the useful perigee boundary of satellite orbits. The feasibility and utility of such designs are evaluated through the use of the Satellite System Design Tool (SSDT), an integrated approach using models and simulations in MATLAB and Satellite Tool Kit (STK). Finally a potential system …
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The galactic population of binaries containing neutron stars
… from other HMXBs by their wide, nearly circular orbits. I show that the discovery of a significant number of such systems is at odds with the conventional wisdom that most neutron stars receive very large "kick" speeds at birth. This problem may be rectified in a self-consistent way if …
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Walking droplets confined by applied or topographically-induced potentials : dynamics and stability
… topography in drop dynamics by considering a circular well that induces a circularly-symmetric Faraday wave pattern. In this regime, we show that droplets become trapped into stable circular orbits around the extrema of the well-induced wavefield. Finally, with a view to extending the …
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Satellite multiple access protocols for land mobile terminals. A study of the multiple access environment for land mobile satellite terminals, including the design analysis and simulation of a suitable protocol and the evaluation of its performance in a U.K. system.
… geostationary, elliptical (Molniya) and inclined circular orbits. These are investigated for various mobile applications and the choice of the Molniya orbit is justified for a U. K. system. Frequency, Time and Code Division Multiple Access (FDMA, TDMA and CDMA) are studied and their relative …
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Initial Orbit Determination Error Analysis of Low-Earth Orbit Rocket Body Debris and Feasibility Study for Debris Cataloguing from One Optical Facility
… method, an iterative method, and an assumed-circular orbit method. Application of the iterative approach results in increased accuracy for the resultant initial orbit determination as compared to the three-point IOD method, and an assumed-circular orbit assumption allows for a further …
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Coordination and control of a multiple spacecraft using convex optimization techniques
… in this analysis, including Hill's equations for circular orbits, modified linear dynamics that partially account for the J2 effects, and Lawden's equations for eccentric orbits. The complete formation flying control approach is successfully demonstrated using a nonlinear simulation environment …
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On the Dynamics of Noncircular Accretion Discs
… axisymmetric, fluid flow undergoing supersonic circular motion and slowly accreting due to angular momentum transport by the disc turbulence. There are, however, strong theoretical and observational grounds for considering non-circular motion in accretion discs. In this thesis I study the …
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Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar
… on two key assumptions; that the gas moves on circular orbits and that this motion traces the underlying gravitational potential. In the case of barred spiral galaxies the first assumption is false as the bar induces non-circular streaming motions in the gas. Therefore, the rotation curves of …
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Debris collision avoidance maneuver optimization (CAMO) for satellite constellations
… scale for closed-loop collision avoidance in circular orbits. For GPS satellites with T = 43,080 s, this yields k ≈ 10,800 s (3 hours). This convergence occurs because the three-burn return-to-station constraint can only be exactly satisfied when 2k = nT /2 (where n is a positive integer), …
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Analytic Modelling of Gravitational-Wave Source in General Relativity and Alternative Theories of Gravity
… corrections to EOB potentials for generic orbits. We also compute the corrections in the EOB Hamiltonian due to tidal effects at 3PN order for circular orbits. Following this, we describe the derivation of the angular momentum flux in the scalar-tensor theory for both the scalar part and …
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Orbital Constellation Design and Analysis Using Spherical Trigonometry and Genetic Algorithms: A Mission Level Design Tool for Single Point Coverage on Any Planet
… adjacent planes with satellite offsets. Assuming circular orbits, these five parameters outline any possible constellation design. The optimization algorithm will use these parameters as evolutionary traits to iterate through the solutions space. This process will pass down the best traits from …
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