Koichi Okita

LE-X -Japanese Next Liquid Booster Engine-

The LE-X engine is under study for Japan’s next flagship expendable launcher (post H2A) to be operated in the next decade with enhanced reliability and reduced cost. The goal of LE-X development is to meet the requirements from the vehicle for higher reliability, lower production cost and appropriate performance. Technology development itself is also a purpose of this investigation and will be applied to other forthcoming engines to be developed in Japan. The early-stage feasibility study of the LE-X engine was completed in 2005 through primary studies on system design, engine component design, cost reduction, reliability prediction, subscale testing, and computational simulation. In 2006, engine system analysis and fundamental studies on LE-X components by means of element tests were successfully conducted. In 2007, we have optimized the engine baseline configuration from aspect of cost reduction activities. Significant cost reduction will be achieved by drastic simplification of the engine system, and the innovation of the manufacturing process. Technology development will be ongoingly conducted to mitigate development risks, such as precise life prediction analysis of combustion chamber, prediction of combustion instability, and high-fidelity simulation.

Next Booster Engine LE-X in Japan

The LE-X is a new cryogenic booster engine with high performance, high reliability and low cost, being designed for the next-generation Japanese launch vehicle. Following an early- stage feasibility study, detailed studies focusing on front-loading design approaches were conducted in 2006 and 2007. An optimum engine system was determined and potential risks were mitigated by various element tests. These activities will lead to the realization of the first booster engine in the world with expander cycle.

Transient Analysis of the LE-7A Rocket Engine Using the Rocket Engine Dynamic Simulator (REDS)

The LE-7A rocket engine has served as the main propulsion system for the H-IIA rocket. This cryogenic hydrogen/oxygen staged combustion cycle engine is an upgraded version of the LE-7 rocket engine used in the booster stage of the H-II rocket. The Kakuda Space Propulsion Center of the Japan Aerospace Exploration Agency has built a simulation model of the LE-7A engine, based on the volume-junction method. Using the simulation model, called the Rocket Engine Dynamic Simulator (REDS), we have carried out transient analyses of the start and shutdown sequences of the LE-7A engine. Results from the model and ground-test data agree well, demonstrating that the model can accurately predict the transient behavior of the rocket engine. This simulation model is expected to be used to predict the effects of changes in engine design and is being modified for application to other rocket engines.

Automatic Thrust and Mixture Ratio Control of the LE-X

The LE-X is a new cryogenic booster engine with high reliability and low cost, designed for the next-flagship Japanese launch vehicle, called H-X. It will be the first booster engine in the world with an expander cycle. One of the characteristics of the LE-X is automatic control of thrust and mixture ratio (LOX/LH2) using electric actuator valves. The valves will reduce the engine dispersion of thrust and mixture ratio and enable throttling smoothly. The LE-X valve configuration is determined and the control method of the LE-X is verified by the subscale valve test and the transient simulation of the LE-X.

Feasibility Study of Multi Objective Shape Optimization for Rocket Engine Turbopump Blade Design

JAXA is now planning to develop a next generation booster engine named LE-X, which is a successor of LE-7A. From an engine cycle study, the LE-X requires a relatively high efficiency turbopump. To achieve this requirement, a feasibility study of design optimization with generic algorithm was applied to the impeller and turbine blade shape. As the first step, single objective optimization was carried out on the impeller blade design, and the second one was a multi objective optimization on the turbine blade shape. It was concerned that optimization may not be effective in such a highly loaded component, however, each of the optimized result have shown improvement on performance. Especially, multi objective optimization can show tradeoff information for several important parameters, therefore, it can be said that such method is quite useful for the improvement or the developing of high efficiency turbopumps.

Study of Next Booster Engine LE-X in JAXA

The Japan Space Exploration Agency (JAXA) has initiated a feasibility study on the next booster engine called LE-X. The goal of LE-X development is to meet the requirements for higher reliability, lower production cost and equivalent performance compared to the LE7A, the current cryogenic booster engine for the H-2A launch vehicle. This paper reports the LE-X development approach to realize high performance, high reliability and low cost, as well as the results of the feasibility study on LE-X.

Large Eddy Simulation of Unsteady Flow in the LE-7A Liquid Hydrogen Pump

The prediction of vibration generated from the turbopump is becoming increasingly important in rocket engine development. In some cases, the vibration of the turbopump originates from the interaction between the rotating impeller and the stationary parts such as diffuser vanes and casing tongues. The present paper describes the application of the numerical code developed by one of the authors (Kato) to predict the flow-induced vibration in the liquid hydrogen pump of the LE-7A rocket engine. The source fluctuations of the flow field are computed by a large-eddy simulation (LES) with the Dynamic Smagorinsky Model (DSM) and the results are fed to the structural vibration analysis, which will be presented elsewhere. Computations of the unsteady flow in the entire liquid hydrogen pump were carried out. Water tunnel experiments were also carried out to obtain validation data and were compared with the numerical results. The computed static pressure distribution and pressure fluctuation agree fairly well with the measured data, which demonstrates that the proposed method can serve as a practical tool for predicting unsteady flows in a rocket engine pump.

Preliminary Design and Analysis for the LE-X Engine Components

JAXA is planning to develop the next booster engine called LE-X with higher reliability and at significantly reduced cost. The LE-X is under study for the future expendable launcher (post H-2A) with enhanced reliability and at reduced cost. We aimed to achieve significant cost reduction by drastic simplification of the components and innovation of the manufacturing process. In 2007, we had optimized the engine baseline configuration. We examined components designs which have potentially achieved cost-cutting targets. This paper reports the progress of the component design. The key design of each component described. At the present, it appears that preliminary design of the LE-X components is successfully conducted. Feasibility of the components designs and the manufacturing process was confirmed.

Preliminary Study of High Power Hydrogen Electric Propulsion for the Space Exploration

High power electric propulsion system is strongly required for future orbital space transportation. MPD (Magneto-Plasma-Dynamic) thrusters and DC (Direct Current) arcjets with hydrogen as a propellant are promising candidates for the missions because of their high performance and adaptability to high power operation. However, to use hydrogen for long term orbital missions, its storage in orbit is crucial issue to be considered. Firstly, we proposed a hydrogen storage and feed system for electric thrusters by applying our technologies derived from the liquid hydrogen launch vehicles. Secondly, we present R&D activities of hydrogen MPD thruster and DC arcjet, especially focusing on the improvement of their performance and durability. Then, development strategy of hydrogen electric thrusters is also discussed. Finally, advantages of hydrogen electric thruster were shown compared with conventional xenon thrusters through mission analyses of lunar orbit insertion and GTO-GEO transportation.

Research works of ethanol propulsion system for the future rocket-plane experimental vehicle

Experimental research works for the ethanol propulsion system has been performed in JAXA/Space Transportation Mission Directorate (STMD) as a part of study for future reusable launch vehicle.. Under this program, 1000 kgf-class (2200 lbf) rocket engine testing, material-matching and critical heat flux (CHF) studies and other related works were conducted in 2009 to 2010. This paper provides an overview of this engine experimental program and the results.