389 research outputs found
Trade-off Between Payload and Trip-Time for EP Interplanetary Missions
No full textPaper AIAA 2004-380
A Finite Difference Method Based on Bicharacteristics for Solving Multidimensional Hyperbolic Flows
No full textPubbl. N. PP217, Istututo di Macchine e Motori per Aeromobili, Torin
Campo di moto potenziale incompressibile attorno a un profilo alare in una galleria di forma arbitraria
No full textImproved Edelbaum's approach to optimize LEO-GEO low-thrust transfers
No full textEdelbaum's approach to the optimization of low-thrust transfers is revisited and some simplifications are removed. The variation of the spacecraft mass due to the propellant consumption is considered in the case of constant thrust, and the corresponding numerical result is compared to Edelbaum's solution. The approach is then extended to consider variable specific impulse and thrust magnitude with constant power level. The payload increment is first computed maintaining Edelbaum's suboptimal control strategy (i.e., constant thrust direction during each half revolution). An analytical solution of the quasi-circular one-revolution transfer is then found using the optimal control of both the thrust direction and magnitude. The very-low-thrust multirevolution problem is again solved by assembling many one-revolution basic trajectories; in particular, the transfer from a 28.5 deg inclined low Earth orbit (LEO) to the equatorial geostationary orbit (GEO) is considered. Exact numerical solutions for both constant and variable specific impulse have also been obtained using an indirect optimization method: the accuracy of the solution based on the quasi-circular approximation has been verifie
Trasformazione conforme per la generazione di griglie per il calcolo del flusso attraverso schiere palettate
No full text
One-Dimensional Analysis of Parabolic-Profile MPD Thrusters
No full textThe application of optimal control theory to the one-dimensional equations of MPD acceleration suggests a convergent-diver gent geometry with straight walls and a corner at the geometrical throat. A gradual variation of the channel slope is usually preferred, and a parabolic profile with the maximum allowable value of the slope derivative provides the best performance. Once the optimal control theory has suggested the channel shape, the actual geometry is univocally determined by assuming the channel height and slope at the inlet. An easy parametric analysis is carried out in the present paper, which discusses the performance of parabolic-profile thrusters, in terms of effective exhaust velocity and efficiency for a given mass flow rate. For the sake of comparison, straight-wall thrusters with either constant-area or convergent-divergent channels are analyzed. The performance of a given thruster is also shown for different applied voltages. © 2001 by the American Institute of Aeronautics and Astronautics, Inc. All rigths reserved
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