Akihide Kurosu

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.

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.

An End-to-End High Fidelity Numerical Simulation of the LE-X Engine - Engine Performance Evaluation and Risk Mitigation Study -

Risk evaluation is important for the development of new engines. Rocket engine components are assembled very close to one another, and the distance for flow passage between them is also small; therefore, fragmentation of the component parts may have a marked influence on the other components. This influence cannot be fully investigated by the one-dimensional (1-D) engine system study usually performed for engine design, since the turning angle of the feeding pipe between the components is large and the flow between the components may become very complex because of the strong secondary flow. Therefore, detailed risk analysis cannot be performed by 1-D analysis, and detailed individual component studies cannot clarify the interactions between components. One possible approach to a reliable risk mitigation analysis is to perform high-fidelity three-dimensional (3-D) computational fluid dynamics (CFD) analyses of the entire engine system and provide a comprehensive understanding of the flow losses and interactions between the components. However, because of the complexity in the flow physics and the prohibitive computational cost, this has never been attempted in the past. In the present report, a numerical analysis of the full LE-X engine system is discussed, including an evaluation of the influence of turbine blade breaks on other components. To the best of our understanding, this is the first report of a high-fidelity end-to-end engine simulation, accomplished using the Japan Aerospace Exploration Agency (JAXA) supercomputer system (JSS), which employs massively parallel computer nodes to make such a large scale simulation feasible. As the first step, various kinds of feasibility studies were conducted, and the engine operating point was compared with the design operating point. As a risk mitigation study, turbine fragment impacts on the feed-line wall were investigated, and a possible alternate shape was proposed.

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.

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.

Regenerative Cooling Performance Analysis of the LE-X Engine Combustion Chamber

In Japan, a feasibility study of the new booster engine called “LE-X” was conducted from 2005 to 2014. One of the key technologies involved in the development of the LE-X engine is a regenerative cooling design to produce enough power to drive the turbopumps. The LE-X engine employs an elongated chamber design to pick up enough heat energy in the regenerative cooling channels. In the current study, a fully conjugated combustion and heat transfer simulation was performed to validate the current numerical approach against a hot firing test of the regeneratively cooled combustion chamber of the LE-X engine. A threedimensional Reynolds-averaged Navier–Stokes simulation was used to consider the injection and combustion processes of propellants on the hot-gas side, heat conduction in the chamber wall, and cooling channel flows. The surface roughness effect was considered to account for the friction force and heat transfer due to the surface roughness. First, the implemented surface roughness model was validated against transcritical parahydrogen flows in electrically heated tubes. The computed wall temperature and pressure loss agreed well with the experimental results. Second, the conjugated combustion and heat transfer simulation was validated against the hot firing test of the LE-X combustion chamber. The computed result accurately predicted the chamber pressure, wall temperatures, pressure loss, and temperature gain in the regenerative cooling channels in the design phase. These results confirmed that the current numerical approach is promising for predicting the regenerative cooling performance in full-scale combustion chambers.

Application of High Fidelity Simulation to LE-X Engine Development

Prediction of physical phenomena is one of the most important technologies in the liquid rocket engine development. Now in Japan, LE-X is being developed as the first stage engine of the Next Flagship Launch System(H-X) with front-loading design approach which enables cost reduction and reliability enhancement by reduction of risks in the early stage of development. Simulation technologies are essential to the design and the CFD analysis tool with high fidelity simulation, the CRUNCH CFD, was applied. As a first step, the accuracies of oxygen dome and hydrogen mixer analyses were verified. The stable with sufficient accuracy analysis models were evaluated and the analysis time was realistic to apply these models to engine design activity. However, the present report revealed that improvement of accuracy and numerical model update are required to apply the present high fidelity simulation to actual engine development.

Robust and Optimized Design for Liquid Rocket Engine

It is important for liquid rocket engine designers to keep enough margins in order to determine the optimum engine configuration in the early phase of the development. In the LE-X engine, which is under study in JAXA for the next booster engine, statistical design process is applied to visualize quantitatively the margin and the correlation of engine system / components performance, reliability, and cost, and to determine the optimum engine configuration. First, we extract the evaluation functions which affect the engine system performance, reliability and cost, and the design parameters which have a large impact on the evaluation functions. Each design parameter allocated to the orthogonal array. Using the orthogonal array, response surface of each evaluation function is caluculated including the production variation. The margins of the evaluation functions and the factor effect between the evaluation functions and the design parameters are calculated and visualized by engine system analysis. Considering the analysis error and development risks, this analysis leads to the optimization of the design parameters of the LE-X engine along with the designers requirement.

Highly Reliable Design Approaches for Next Booster Engine LE-X

The LE-X is a new cryogenic booster engine with high reliability and low cost, designed for the next-generation Japanese launch vehicle called H-X (post H-2A). The purpose of LEX development is to certify the feasibility of 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. In parallel with design studies and component tests, two kinds of new design approaches necessary to attain highly reliable engine have been investigated and tried since 2005. One is the optimized design approach for initial system design, which aims to balance the design margins of each component with launch capability and production cost. The other is the reliability evaluation approach, which aims to extract and evaluate the risks of system and components. As a result of some trials, availability of these approaches were confirmed.