野中 聡

<p>It is known that aerodynamic characteristics of a slender body vary substantially at high angles-of-attack (AoAs), and then, will have strong impacts on its flight. For, example, the yaw force makes flight unstable. In this study, we investigated the relation between the yaw force and the configuration, and details of flowfield around the slender-bodied-vehicle numerically. The configuration consisting of “nose cone” and “square aftbody” parts was employed as the baseline, and then, compared with other three configurations having different fineness ratios. According to our computed results, in the case of 50 degrees of AoA, the longer the model became, the more asymmetry appeared: yaw force and asymmetry were found to be attributed not only to the length of the body, but also to the nose bluntness. On the contrary, in the case of 140 degrees, the shorter the model became, the more asymmetry appeared. Furthermore, the large nose bluntness increased C_Y. Interestingly, this trend is totally opposite to that observed at 50 degrees. It had been considered that the large nose bluntness and the small fineness ratio can reduce asymmetry and C_Y, however, this study showed that it is not true in the case over 90 degrees, due to complex wake flow structure discovered in the present numerical simulations.</p>

<p>The development of a fully reusable vertical-takeoff-and-vertical-landing (VTVL) rocket is indispensable for reducing space transportation costs. However, there are many technical issues associated with such vehicles, such as turnover maneuvers during return flight where the pitching moment plays a key role. It is known that aerodynamic characteristics can be controlled by installing aerodynamic devices, but the relationship between the aerodynamic characteristics and the flowfields has not been explored. To clarify this relationship using computational fluid dynamics (CFD), we investigated these flowfields and aerodynamic characteristics, in the case where we install such devices (fins) in the nose part of a reusable rocket. We found that vortices form downstream of the aerodynamic devices. For angles of attack between 0 and 90 degrees (in which the fins are located in the upstream portion), these vortices significantly affect the surface pressure on the rocket and increase the pitching moment. On the other hand, for AOAs between 90 to 180 degrees (in which the fins are in the downstream portion), the effect of these vortices on the on-surface pressure is negligible, and only vortices formed near the surface of the fins increase the pitching moment.</p>

<p>Most of flight vehicles have various protuberant devices on their surfaces, but asymmetry in their positioning with respect to the body axis can affect aerodynamic characteristics of vehicles, particularly roll moment. Thus, it is important in rocket development to clarify the effects of the protuberances on the vehicle aerodynamic characteristics. In this study, as a basic research, we systematically investigated such effects using CFD, by changing the positions of a protuberance. As a result, the roll moment increased nearly linearly with angle of attack (=α), but its trend was different in protuberance locations, particularly when arranged near the center-of-gravity. In positioning there at α = 20 °, the wake vortex center moved farther away from protuberance compared with α = 15 °, then the pressure decline at its wake side was suppressed, and thus, the pressure difference between its upstream and downstream sides became smaller. As a consequence, the roll moment did not arise linearly, but decreased at α = 20 °.</p>

<p>In this paper, anomaly detection that is configured as a combination of state observer and Mahalanobis-Taguchi (MT) method is proposed for real time fault detection of rapid and dynamic phenomena such as rocket engine operation. Real time anomaly detecting is recognized as one of the most important elements to realize advanced reusable space transportation system. Conventionally, bottom-up type anomaly detecting logic based on failure mode and effect analysis (FMEA) is usually used for this purpose, however, it requires large amount of time and labor. The proposed method can improve this process. In the present method, error values between calculated ones through rocket engine simulator constructed on autoregressive moving average model and extended Kalman filter (EKF) and measured ones are standardized with existing normal operation data of the rocket engine so as to compute Mahalanobis' distance, which expresses degree of anomaly. We performed engine hot firing tests in simulated anomaly conditions. The obtained data was processed with the present method, and the simulated anomaly in the tests was detected as expected.</p>