Hatsuo Mori

Robust parameter design using a supersaturated design for a response surface model

Recently, the application of response surface methodology (RSM) to robust parameter design has attracted a great deal of attention. In some cases, experiments are very expensive and may require a great deal of time to perform. Central composite designs (CCDs) and Box and Behnken designs (BBDs), which are commonly used for RSM, may lead to an unacceptably large number of experimental runs. In this paper, a supersaturated design for RSM is constructed and its application to robust parameter design is proposed. A response surface model is fitted using data from the designed experiment and a stepwise variable selection. An illustrative example is presented to show that the proposed method considerably reduces the number of experimental runs, as compared with CCDs and BBDs. Numerical experiments are also conducted in which type I and II error rates are evaluated. The results imply that the proposed method may be effective for finding the effects (i.e. main effects, two-factor interactions, and pure quadratic effects) of active factors under the ‘effect sparsity’ assumption. Copyright

The Status of the Research and Development of LNG Rocket Engines in Japan

This chapter reports the status of research and development which have been carried out to realize a liquefied natural gas (LNG) rocket engine with higher performance in Japan. As a fuel of rocket engine, LNG has better characteristics, i.e., longer storage, lower cost, and nontoxic; hence, LNG rocket engines have been investigated among many countries. However, LNG rocket engines have never been used for actual flight application in Japan, even in the world. The reason is that the performance and characteristics of the current LNG rocket engines do not have enough advantages compared with other liquid rocket engines. For example, if it would apply to a future reusable liquid rocket booster, the specific impulse (Is) of LNG rocket engine should be higher than 360 s in order to get more advantages than other liquid rocket engines. The Is of the current LNG rocket engines in Japan is between 310 and 350 s, falling short of the target level of 360 s. Therefore, continuous research and development have been conducted for the purpose of extending the advantages and promoting the practical use of LNG rocket engines in Japan.

A High-Speed Response LOX/LH 2 Full Expander Cycle Engine with Deep Throttling Capability

For a flight test campaign of reusable vehicle, 10 kN class small LOX/LH 2 propulsion systems have been developed. They are regenerative cooling engines with a continuous throttling capability for making vertical landing possible. Current phase of the campaign is to demonstrate an entire sequence of full-scale operation with a vehicle equipped with turbopump-fed engine, following the three-generation vehicles with pressure-fed engine had successfully performed in repeated flight operation tests between 1999 and 2003. From a result of primary system analysis, we decided to build an expander cycle engine by refurbishing a pair of turbopumps, which had been build for another research program, and putting them into a new engine developed in the present study. A combustion chamber with long cylindrical portion adapted to the engine cycle was also newly made. Three captive firing tests were conducted to verify functional suitability for the vertical landing flight. In the last two tests, a deep throttling capability down to 28 % and a high-speed response over 5 Hz of the propulsion system were successfully demonstrated with newly developed thrust control system. The fourth-generation vehicle powered by the full expander cycle engine is now under development.