Koki Kitagawa

Effects of Swirling Liquid Oxygen Flow on Combustion of a Hybrid Rocket Engine

In order to investigate combustion processes of directly exposed PMMA to LOX, tests of a small hybrid combustor with a single port filled with LOX or GOX without swirling were carried out. It was found that combustion processes of LOX/PMMA are determined by evaporation of LOX. Experiments of combustion in a hybrid rocket engine with a swirling LOX flow were conducted. Axial profile of local fuel regression rates showed that evaporation of LOX made the effects of swirl of the injected LOX small. Fuel regression rates, C* efficiency and specific impulse of the hybrid rocket engine with the swirling LOX flow were smaller than those with the swirling GOX flow. The performance of the engine was lower than that with GOX. The existence of LOX in the combustion chamber decreased the combustion characteristics due to the loss of the angular momentum, the decrease of the net Go and the longer combustion time. Combustion oscillation also occurred at a certain condition and this combustion oscillation was confirmed to be a “Chugging” mode due to combustion time lag of LOX.

Multidisciplinary Design Exploration for Sounding Launch Vehicle using Hybrid Rocket Engine in View of Ballistic Performance

Abstract Conceptual design of a launch vehicle with a hybrid rocket engine (HRE) has been implemented using design informatics approach in order to investigate the feasibility of a single-stage hybrid rocket. Two test design problems were formulated by using two objective functions: maximization of downrange and minimization of initial gross weight, seven design variables which describe geometry and initial conditions, and one constraint relative to target altitude. The optimization result reveals the economical performance of hybrid rocket is limited with HRE in terms of the maximum downrange achievable. Moreover, the data-mining result indicates the mechanism of design-variable behavior.

Burning rate anomaly of composite propellant grains

In this study, characteristics of the burning rate anomaly in composite propellant grains are investigated. The burning rate anomaly has been known as the “midweb anomaly” or the “hump effect.” This paper describes some results of an experimental study on effects of propellant formulations, casting processes, and viscosity of the propellant slurry on the phenomena. According to some past studies, it has been suggested that the geometry of the “isochrone surface” of the propellant slurry affects the local burning rate. To investigate the effect of the isochrone surface, visualization of the isochrone surface in composite propellant grains is carried out. A relation between the geometry and the local burning rate measured in motor firing tests and strand tests is proposed. As a result, besides the common static characteristics of the burning rate anomaly, i.e., the pressure hump effect and the nonisotropic characteristic of the local burning rate, a peculiar burning rate distribution in connection with the isochrone surface is obtained.

Correlation of Midweb Anomaly with Microstructure of Composite Propellant

Three dimensional information of sub-millimeter AP particles and local burning rates of composite propellant have been obtained. In this study, to investigate correlation between the orientation of sub-millimeter AP particles and the local burning rate, the data of the local burning rate and the orientation data were arranged and evaluated. As a result, it is suggested that there is the correlation at the propellant that the midweb anomaly occurs. This result provides experimental evidence for the supposition that the orientation of AP particle affects the local burning rate.

Hybrid Propulsion Technology Development in Japan for Economic Space Launch

The demand for the economic and dedicated space launchers for vast amount of lightweight, so-called nano-/microsatellites, is now growing rapidly. There is a strong rationale for the usage of the hybrid propulsion for economic space launch as suggested by the assessment conducted here. A typical concept of development of such an economic three-stage launcher, in which clustering unit hybrid rocket engines are employed, is described with a development scenario. Thanks to the benefits of hybrid rocket propulsion, assuring and safe, economic launcher dedicated to lightweight satellites can be developed with a reasonable amount of quality assurance and quality control actions being taken in all aspects of development such as raw material, production, transportation, storage, and operation. By applying a multi-objective optimization technique for such a launch system, examples of possible launch systems are obtained for a typical mission scenario for the launch of lightweight satellites. Furthermore, some important technologies that contribute strongly to economic space launch by hybrid propulsion are described. They are the behavior of fuel regression rate, the swirling-oxidizer-flow-type hybrid rocket, the liquid oxygen vaporization, the multi-section swirl injection, the low-temperature melting point thermoplastic fuel, the thrust and O/F simultaneous control by altering-intensity swirl-oxidizer-flow-type (A-SOFT) hybrid, the numerical simulations of the internal ballistics, and so on.

Flight Performance Simulations of Vertical Launched Sounding Rockets Using Altering-Intensity Swirling-Oxidizer-Flow-Type Hybrid Motors

In practical usage of conventional hybrid rocket engines, the oxidizer-to-fuel ratio (O/F) shift occurs by either the fuel port diameter increase or throttling because the fuel regression rate is not proportional to the oxidizer mass flux. As a promising technique to eliminate the O/F shift in a wide throttling range, Altering-intensity-Swirling-Oxidizer-Flow-Type (ASOFT) hybrid rocket engines are proposed. A-SOFTs control O/F, independently of thrust, with the swirl intensity of oxidizer from the injector, as well as the mass flow rate of the oxidizer. In this paper, the increase rates of engine performance caused by O/F shift eliminating technique are evaluated with a vertical launch simulation for single stage sounding rockets. This simulation includes the throat erosion and c* efficiency models which can be affected by O/F shifts. The statistical uncertainty of fuel regression model is also included to evaluate the robustness of A-SOFTs and SOFTs. The increase rates of total impulse and maximum altitude of A-SOFTs compared to SOFTs depends on maximum oxidizer mass flow rate and are about 2% and 4% respectively. The most effective indicators in this evaluation to the flight performance are residuals of propellants and c* efficiency. Owing to the sensitivity of the flight performances to residuals, the fuel regression errors can cause risks of large losses of the highest altitude in SOFTs, and it is found that the feedback control of A-SOFTs have robustness to the fuel regression errors to some extent. c* efficiency dependent on L* is also sensitive to O/F shifts because O/F shifts affect combustion chamber volume and increase of throat area.

Correlation of Midweb Anomaly with Microstructure of Composite Propellant Containing High Amount of Aluminum

To investigate correlation between the orientation of sub-millimeter AP particles and the local burning rate in a propellant containing high amount of Al particles, the orientation angle data of sub-millimeter AP particles were obtain by using X-ray CT. The orientation data were compared with the local burning rate obtained in previous study. As a result, it is confirmed that if the orientation angle of the coarse AP particles against the burning direction is small, the burning rate become high. This result provides experimental evidence for the supposition that the orientation of AP particle affects the local burning rate.

Elucidation of Influence of Fuels on Hybrid Rocket Using Visualization of Design-Space Structure

The stratum-type association analysis as a new data mining technique has been applied to the conceptual design of a single-stage launch vehicle with hybrid rocket engine. The conceptual design was performed by using design informatics, which has three points of view, i.e., problem definition, optimization, and data mining. The primary objective of the present design is that the down range and the duration time in the lower thermosphere are sufficiently secured for the aurora scientific observation, whereas the initial gross weight is held down to the extent possible. The multidisciplinary design optimization was performed by using a hybrid evolutionary computation. Data mining was also implemented by using the stratum-type association analysis. Consequently, the design information regarding the tradeoffs has been revealed. The hierarchical dendrogram generated by using the stratum-type association analysis indicates the structure of the design space in order to improve the objective functions. Furthermore, the assignments of the stratum-type association analysis have been obtained.

Genetic Algorithm Applied to Design Knowledge Discovery of Launch Vehicle Using Clustered Hybrid Rocket

The conceptual design of a multi-stage launch vehicle (LV) using a clustered hybrid rocket engine (HRE) is carried out through multi-disciplinary design optimization. This LV designed in this study can deliver micro-satellites to sunsynchronous orbits (SSO). The optimum size of each component, such as an oxidizer tank containing liquid oxidizer, a combustion chamber containing solid fuel, a pressurizing tank, and a nozzle, should be strictly optimized because of the combustion mechanism is different from existent liquid/solid rocket engines. In this study, the semi-empirical based evaluation is applied to the design optimization of the multi-stage LV. For clustered HRE, paraffin (FT-0070) is used as a propellant for the HRE, and three cases are compared to examine the commonization effect of the engine for each stage: In the first case, HREs are optimized for each stage. In the second case, HREs are optimized together for the first and second stages but separately for the third stage. In the third case, HREs are optimized together for each stage. The optimization results show that the performance of the design case that uses the same HREs in all stages is 40% reduced compared with the design case that uses optimized HREs for each stage.

Design Methodology of a Hybrid Rocket-Powered Launch Vehicle for Suborbital Flight

AbstractA multidisciplinary design methodology for a launch vehicle (LV) with a hybrid rocket was proposed in order to obtain qualitative design knowledge. In this study, a propulsion system perfor...