1,720,980 research outputs found
Optimal design of hybrid rockets with self-pressurising oxidizer
No full textA nested direct/indirect method is used to find the optimal design of a microgravity platform which consists of a hybrid sounding rocket that uses a self-pressurizing oxidizer, namely, nitrous oxide. The direct optimization of the parameters that affect the engine design is coupled with the trajectory indirect optimization to maximize a given mission performance index. Different models can be used to describe the self-pressurizing behavior of the oxidizer in the tank. The simplest model assumes liquid/vapor equilibrium. A two-phase model is also proposed: saturated vapor and superheated liquid are considered and the liquid/vapor mass transfer is evaluated making reference to the liquid spinodal line. Results show that the different models have a limited impact in the optimal engine characteristics. The performance are slightly modified due to the different mass of the residual oxidizer. A performance comparison with different propellant combinations is also shown
Robust Design Approaches for Hybrid Rocket Upper Stage
Full text linkComputational 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
Full text linkOptimization 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
Composite Propellant Manufacturing Process Based on Deposition and Light-Activated Polymerization for Solid Rocket Motors
No full textPhoto-polymerization for additive manufacturing of composite solid propellants
Full text linkThe established state-of-the-art for composite solid propellant grain manufacture consists in mix-cast-cure process using hazardous chemicals and specific molds for propellant forming. In most of the cases, polyaddition of oligomers involves isocyanate functional groups. Construction constraints limit the feasibility of propellant geometries, confining the pressure-time history of rocket motors to some established configurations. Composition pot-life becomes one of the most important parameters in the definition of correlated industrial processes. An additive manufacturing process for propellant grain production based on UV curing has been recently proposed for patenting. This technique enables more complex grain geometries, paving the way for new propulsive missions, thanks to customized thrust-time profiles or local composition fine tuning. The new curative method makes innovative use of pre-polymers, replacing isocyanates with UV-sensitive components characterized by lower chemical hazard for operators. The paper illustrates the experimental results obtained during the preliminary test campaign on propellant inert simulators, produced as lab-scale proof of concept. The activity targeted mono-layer samples, focusing on binder properties. Dynamic-mechanical thermal analysis, thermal-gravimetric analysis, and stress–strain tests have been carried out to measure mechanical and physical characteristics of different formulations. Both hydroxyl-terminated polybutadiene (HTPB) and polybutadiene diacrylate (PBDDA) binders have been considered, using ammonium sulfate as substitute of ammonium perchlorate. Aluminized and non-aluminized samples have been manufactured to evaluate the impact of opaque-reflective materials during the UV curing process. The reported analyses show comparable results for both the new UV-cured materials and demonstrate the feasibility of propellants based on isocyanate-free process
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