Shinya Maruyama
(Tokai University, Japan)

Recently, the research on a hybrid rocket is actively done because of their. For example their high safety record, low-cost, and reduced impact for environment. However, hybrid rockets have not been put to practical use because of their faults. The most significant problem of hybrid rockets is their very low regression rate. Some study such as the Oxidizer-Swirling-Flow, Cascaded Multistage Impinging-jet and the paraffin-based fuels are done in order to improve the burning performance. From previous research, the paraffin-based fuel burned 3 to 4 times faster than the conventional fuels such as HTPB. However, the paraffin-based fuel has the problem in manufacturing because of their low tensile strength, bonding method inside the fuel cartridge and shrinkage. Moreover, it is difficult for paraffin-based fuel to mix with metal powder because of its low viscosity. In this study, the solution of the above issues are attempted by mixing thermoplastic resins such as the Ethylene Vinyl Acetate Copolymer (EVA), Polyethylene Glycol (PEG), and Polyethylene (PE) with the paraffin-based fuel.

Kai Iijima
(Tokai University, Japan)

Today, hybrid rockets are expected to be used for ultra-small launch vehicle, manned sub-orbital flight and so on. However, their performance is not enough for practical use because of their low regression rate and low combustion efficiency. From previous research, it is known that using wax fuel is effective method to increase the regression rate. On the other hand, its combustion efficiency is decreased remarkably by using wax fuel. This is because much of the liquefied fuel is entrained into the flame zone without vaporization, or goes through the nozzle without reacting with the oxidizer. Therefore, it can be considered that fuel and oxidizer stirring using flameholder improve the combustion efficiency. We designed the multiport flameholder and carried out some experiments to confirm the effect of flameholder for c^* efficiency. Also, vaporization techniques of oxidizer are needed to increase the regression rate when we use the oxidizer-swirling-flow. So, we designed water-cooled flameholder and researched the heat supply from combustion chamber into flameholder.

Yuki Funami
(The University of Tokyo, Japan)

Hybrid rocket propulsion is considered to be promising technology for the next generation space transportation. In a typical hybrid rocket, the fuel is solid and the oxidizer is liquid or gas. In this study, numerical analysis tool is developed for prediction of hybrid rocket performance, such as regression rate characteristics, specific impulse, characteristic exhaust velocity, and so on. Internal phenomena in a hybrid rocket chamber are very complicated. Fluid phenomenon of main stream and thermal conduction phenomenon in a solid fuel are considered, because characteristic times of these phenomena are longer than those of other phenomena. Thus, these phenomena are coupled and solved in the tool. On the other hand, characteristic times of chemical reactions are short adequately, and quasi-steady flame is assumed. Chemical composition is estimated by chemical equilibrium calculation. Steady state flowfields are obtained by numerical simulations with the tool, and hybrid rocket performance is predicted. In 28th ISTS, the detail of this method and calculation results of performance prediction will be shown.

Keisuke Sotozono
(Tokai University, Japan)

Today, the combined cycle engine for the horizontal-takeoff-spaceplane is researched all over the world. This type spaceplane is hoped to be realized for the space travel, Re-use type space transportation system and so on. The combined cycle engine consists of air-breathing engine and rocket engine which are operated under the ejector jet mode, ram jet mode, scram jet mode, and rocket mode. Therefore we can achieve the takeoff, space flight, and landing by switching these flight modes using one combined cycle engine. Above all, the ejector jet mode is operated under the condition of takeoff through Mach 2 and it takes advantage of the ejector effect. Ejector effect uses the exhaust gas of core rocket which is installed inside the air intake. However, internal flow and optimum shape of air-intake is not studied well. So, in this study, we carried out the numerical simulation about internal flow of air-intake. This result will be used for the experimental study of ejector jet engine.

Yosuke Kitagawa
(Tokyo Metropolitan University, Japan)

Multi-disciplinary design exploration for three-stage hybrid rocket is presented. To solve the multi-objective design problems, the modified Multi-Objective Genetic Algorithm (MOGA) is employed. MOGA used here is one of the optimization methods for multi-objective problems, and utilized real-number cording and the Pareto ranking method. Pareto ranking method (PCP) which is one of the data mining methods is also employed for design knowledge discovery. Basic concept considered here is a three-stage rocket for delivering micro-satellites to the Sun-synchronous orbit which consists of an oxidizer tank containing the LOX, the combustion chamber containing the solid fuel, pressurant tank containing the helium, and nozzle. Objective functions considered in this study are to minimize the gross weight of the rocket, and to maximize the payload weight. The regression rate is estimated based on empirical model in consideration of WAX propellant. As shown in Fig.1, everal non-dominated solutions could be obtained by MOGA and design knowledge could be discovered for present hybrid rocket design problem using PCP analysis.