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Full-Text Articles in Engineering
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 …
Detonation Branching In A Pde With Liquid Hydrocarbon Fuel, Kristin L. Panzenhagen
Detonation Branching In A Pde With Liquid Hydrocarbon Fuel, Kristin L. Panzenhagen
Theses and Dissertations
A pulse detonation engine (PDE) capitalizes on the large mass flux and pressure rise associated with detonations to create thrust, which is proportional to PDE cycle frequency. This research showed that using a branched detonation as an ignition source, as opposed to standard spark ignition, deposits more energy into the thrust tube head. The increase in energy decreases ignition delay and detonation to deflagration transition (DDT) time. This allows a theoretical 85% cycle frequency increase that is accompanied by an 85% increase in thrust. The increase in energy also reduces the need for a DDT enhancement device, thereby increasing thrust …
Ion Based Pressure Sensor For Pulse Detonation Engines, Jeffrey S. Zdenek
Ion Based Pressure Sensor For Pulse Detonation Engines, Jeffrey S. Zdenek
Theses and Dissertations
A high speed, durable, ion probe based pressure sensor is being investigated for use in pulse detonation engines. Traditional pressure sensors are ill suited for the high temperature and vibratory environment encountered in such engines. An alternative transient pressure sensing method is investigated for pressures behind a hydrocarbon flame. These flames generate ions that are quenched by collisions as a function of pressure. An experiment was devised to correlate the ion decay rate with the pressure using an ion probe well suited for the flow. A correlation has been established showing the ion decay rate is a function of pressure. …
Performance Study Of Two-Stage-To-Orbit Reusable Launch Vehicle Propulsion Alternatives, Marc A. Brock
Performance Study Of Two-Stage-To-Orbit Reusable Launch Vehicle Propulsion Alternatives, Marc A. Brock
Theses and Dissertations
This study investigated the performance of five Two-Stage-To-Orbit reusable launch vehicles (RLV), with stages propelled by rocket engines, turbojet engines and Rocket Based Combined Cycle (RBCC) engines. Horizontal versus vertical takeoff launch and direct versus lifting ascent trajectories were also studied. A method was conceived using a 3 degree of freedom optimization program, stage inert mass fractions, and a fixed gross takeoff weight (GTOW) of 1,000,000 lbf to determine each RLVs performance based on payload weight delivered to orbit and total vehicle inert weight. RLV trajectory constraints, mass fractions, engine performance, and aerodynamics were assumed from literature of similar RLVs …
Isomer Energy Source For Space Propulsion Systems, Benjamin L. Johnson
Isomer Energy Source For Space Propulsion Systems, Benjamin L. Johnson
Theses and Dissertations
Presented in this work are the results of an investigation of alternative means for powering spacecraft and launch vehicles with energy sources other than chemical combustion. Nuclear thermal propulsion and the energy release of a nuclear spin isomer present potential for increased rocket performance with compact, high-energy fuel sources replacing the combustion engines of the Delta IV-H 1st and 2nd stage vehicles. Analysis of historical fission designs along with the isomer hafnium-178-m2 in a particle bed configuration was conducted. Energy storage levels of 1.3 GJ/g are possible with this material, though the successful triggering and maintenance of a chain reaction …
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Theses and Dissertations
Considerably short electrodynamic tethers can be used as a low-thrust propulsion system with minimum or no mass expenditure. The propulsive force is generated by inducing a current flow through the tether which interacts with the magnetosphere of the planet (i.e. Earth, Jupiter and other planetary bodies with magnetosphere). The basics of electrodynamic tether systems have been studied and successful experiments such as boost and de-boost of spacecraft have been conducted in the past. This study presents a simple guidance scheme for the current in the tether in order to perform orbital maneuvers. The general perturbation equations are used to develop …
Orbital Applications Of Electrodynamic Propulsion, Troy Irwin
Orbital Applications Of Electrodynamic Propulsion, Troy Irwin
Theses and Dissertations
Electrodynamic propulsion (EDP) uses forces resulting from electric currents in conductors as a spacecraft travels through a magnetic field. A vehicle-independent expression for the specific power required for any maneuver is derived and used to assess EDP feasibility. Analytical expressions for the accelerations and combined current-conductor vector required to change the orbital plane or the argument of perigee are developed based on Lagranges planetary equations. Solutions to the forced Clohessy-Wiltshire equations are developed to study iii-plane rendezvous. Results show EDP can change inclination or right ascension of the ascending mode at approximately 0.4 degrees/day with current spacecraft specific power technology. …
Shielded Coil Electrodynamic Propulsion (Scep). A Feasibility Study, Richard J. R. Ladouceur
Shielded Coil Electrodynamic Propulsion (Scep). A Feasibility Study, Richard J. R. Ladouceur
Theses and Dissertations
This study investigated Shielded Coil Electrodynamic Propulsion SCEP. The use of the earths magnetic field as a propulsion source has been previously investigated. It was found that a significant amount of power and long conductors were required. A more compact propulsion concept which requires significantly less power is proposed. This concept relies on the feasibility of significantly reducing the magnetic force induced by the earths magnetic field on selected segments of a coil. An experiment design to support the theoretical findings was conducted. The experiment results support the theoretical model.