2,236 research outputs found
Wave propagation in solids with vectorial microstructures
No full textAbstract. In nonclassical mechanics it is natural to deal with the problem of the propagation of nonlinear waves in solids with different internal structural scales (Engelbrecht, J., Pastrone, F., Braun, M., and Berezovski, A. Hierarchy of waves in nonclassical materials. In Universality of Nonclassical Nonlinearity (Delsanto, P. P., ed.). Springer, 2007, 29-48) Acad. Sci. Paris, 2004, Ser. I 337, 513-518) in three different cases: one-dimensional solids with two different microscales, two-dimensional solids with microstructures, and plane granular media. In all cases the hierarchical structure of equations due to the scales in materials is evident
Robust Design Approaches for Hybrid Rocket Upper Stage
No full textComputational costs of robust-based design optimization methods may be very high. Evaluation of new procedures for the management of uncertainty with applications to hybrid rocket engines is here carried out. Two newly developed procedures are presented (hybrid algorithm and iterated local search), and their performances are compared with those of two previously developed procedures (genetic algorithm and particle swarm optimization). A liquid oxygen/paraffin-based fuel hybrid rocket engine that powers the third stage of a Vega-like launcher is considered. The conditions at third-stage ignition are assigned, and a proper set of parameters are used to define the engine design and compute the payload mass. Uncertainties in the regression rate are taken into account. An indirect trajectory optimization approach is used to determine a mission-specific objective function, which takes into account both the payload mass and ability of the rocket to reach the required final orbit despite uncertainties. Results show that for this kind of problem, particle swarm optimization and iterated local search
outperform the genetic algorithm, but the use of a local search operator may slightly improve its performance
Hybrid rocket engine design optimization at politecnico di torino: A review
No full textOptimization of Hybrid Rocket Engines at Politecnico di Torino began in the 1990s. A comprehensive review of the related research activities carried out in the last three decades is here presented. After a brief introduction that retraces driving motivations and the most significant steps of the research path, the more relevant aspects of analysis, modeling and achieved results are illustrated. First, criteria for the propulsion system preliminary design choices (namely the propellant combination, the feed system and the grain design) are summarized and the engine modeling is presented. Then, the authors describe the in-house tools that have been developed and used for coupled trajectory and propulsion system design optimization. Both deterministic and robust-based approaches are presented. The applications that the authors analyzed over the years, starting from simpler hybrid powered sounding rocket to more complex multi-stage launchers, are then presented. Finally, authors’ conclusive remarks on the work done and their future perspective in the context of the optimization of hybrid rocket propulsion systems are reported
Optimal Design Comparison of Hybrid Rocket for Small Satellite Launchers
No full textIn the present paper, a three stage hybrid rocket is considered as a small satellite launcher. The same engine is used in different numbers in each stage: 6,3 and 1 in the first, second and third stage, respectively. This design choice aims at an overall reduction of the launcher cost. Liquid oxygen and a paraffin-based fuel are employed as propellants. The feasibility of a ground launch from 45° North latitude is evaluated and compared to a similar three-stage launcher with airborne launch. In the present work, an electric turbo pump feed system is used. The optimization procedure exploits of a direct method for engine design parameters, whereas an indirect method optimizes the ascent trajectory once the engine design is given. Constant power operation is assumed for the electrical feed system. The initial mass of the launcher is given (5000 kg) and the payload mass is maximized for a given insertion orbit. The initial thrust is fixed in order to have an initial acceleration equal to 1.4 g. The results show that the proposed small satellite launcher concept is able to deliver payload mass in the range 50-100 kg into the desired orbit
Thermoelastic stress analysis for the linear thermoelastic bodies
No full textQuaderni Scientifici del Dipartimento di Matematica dell'Università di Torin
Optimal Design of Hybrid Rocket Small Satellite Launchers: Ground Versus Airborne Launch
No full textA three-stage hybrid rocket is considered as a small satellite launcher. The same engine is used in different numbers in each stage: six, three, and one in the first, second, and third stages, respectively. This design choice aims at an overall reduction of the launcher cost. The propellants are liquid oxygen and a paraffin-based fuel. The performance of different feed systems and launch options are evaluated: the feasibility of a ground launch is analyzed and compared to similar three-stage launchers with airborne launch using both a gas pressurized feed system and an electric turbopump feed system. The optimization procedure exploits a direct method to evaluate the best values of engine design parameters, whereas an indirect method optimizes the ascent trajectory once the engine design is given. Constant power and blowdown operation are, respectively, assumed for the electrical feed system and the gas pressurized feed system. The initial mass of the launcher is given (5000 kg), and the payload mass is maximized for a given insertion orbit. The initial thrust is fixed in order to have an initial acceleration equal to 1.4g. The nozzle expansion ratio in the first-stage engines is reduced to avoid separation at liftoff in the ground case, and the third-stage engines are used at a lower vacuum thrust level to satisfy maximum acceleration constraints. The results show that the proposed small satellite launcher concepts are able to deliver payload masses in the range of 40-100 kg into the desired orbit
Composite Propellant Manufacturing Process Based on Deposition and Light-Activated Polymerization for Solid Rocket Motors
No full text- …
