In spacecraft systems, it is important to quickly detect and deal with anomalies. However, the increasing complexity of spacecraft systems makes it difficult to avoid failures using previous anomaly detection methods. In recent years, anomaly detection methods based on machine learning have been studied. But it is difficult for a spacecraft to detect anomalies autonomously in orbit. In this study, we propose an anomaly detection method that defines and monitors a single variable representing the health status of a spacecraft system, instead of monitoring a huge amount of telemetry data. We have confirmed that the single variable can represent the health status of a spacecraft system and can be applied to the anomaly detection method.

In the development of jet noise reduction devices, high efficiency and low cost can be achieved by using 1% scale nozzles and low-density gas as an alternative to full scale devices and hot gas. However, very high frequency noise is generated from the nozzle, and the upper limit frequency of a normal condenser microphone is insufficient. Therefore, a high frequency optical microphone based on the Schlieren method was developed, which measures the density gradient caused by the sound wave. The frequency response of the optical microphone was numerically calculated and corrected, and the frequency response was investigated using the characteristics of jet noise. Additionally, the noise reduction performance of the ejector nozzle was investigated using the optical microphone.

In order to reduce launch cost, ISAS/JAXA has been developing a reusable vertical-takeoff and vertical-landing (VTVL) rocket. Currently, the prototype model ``RV-X'' is being developed. This rocket adopts nose-entry returning flight system and needs the turnover maneuver before landing. It is known that the side-force is generated by asymmetrical vortices when the rocket flies at high angles of attack, and also known that the apex angle of the nose cone affects the magnitude of side force. In this study, we conducted wind tunnel testing and CFD on the aerodynamics of the RV-X with a double-cone nose. The surface flow field were used for CFD validation. Consequently, we obtained following findings: 1) the slight asymmetry of the experimental model due to machining accuracy and surface roughness significantly affected the magnitude of side force, 2) the flow field by CFD at 60º angle-of-attack was qualitatively consistent with the surface flow field visualized by an oil-flow technique, 3) the vortices generated from the nose collapsed at the rear part of the body and formed an asymmetrical flow field, 4) the generation of asymmetrical vortices with respect to the angle of attack was influenced primarily by the first cone, but the created side force was determined by interactions of the first and the second cones.

Small satellite formation flying is an innovative approach to acquire high spatial resolution data. Formation flying mission needs to keep required relative position. However, orbit disturbances, specifically J2 and atmospheric drag, have a large effect on small satellites in Low Earth Orbit (LEO), resulting in the relative position to drift apart. Previous studies considered periodic conditions for the Kepler problem, Hill's equation, and J2 to maintain the relative distance under orbit disturbances. However, in the case of atmospheric drag, previous conditions don't have enough effective range for available orbital elements in LEO. This paper proposes a periodic condition under atmospheric drag which is effective in a wide range and evaluates the proposed condition using numerical simulation. Since atmospheric drag is a nonpotential force, the conventional method does not have effectiveness. This paper derives that condition, considering energy reduction by nonpotential force. Comparing the proposed condition to the previous conditions, numerical simulations showed that the proposed condition can work under a wide range of orbital elements to reduce the drift of relative distance due to disturbance. Furthermore, the proposed condition can effectively work even if there are orbit determination errors.