Pulse arc discharge is successfully generated in a Mach 5 supersonic free-jet between a pair of electrodes perpendicular to the flow with the voltage at 300V and the current at 200A. Two different gap lengths, 2mm and 6mm, between the electrodes are tested. From the high-speed images of the discharge, it is found that the arc discharge runs across the jet with the short gap, 2mm, while the arc discharge runs around the shear layer of jet with the longer gap, 6mm.

Research and development of electric vertical takeoff and landing (eVTOL) aircraft has advanced significantly over the past decade. As electrification accelerates worldwide, propulsion systems are required to have higher performance, such as higher power density, higher efficiency, and lower noise. Since energy loss of component is influenced by temperature and physical properties of materials used in motors, a coupled analysis of the magnetic field and heat is necessary to avoid high temperature. In this study, a Halbach array motor was adopted to achieve high power density and high efficiency, the commercial software JMAG was used to estimate performance, and modeFRONTIER was employed to establish the design system. The multi-objective optimization design was carried out with bi-directionally-coupled analysis of magnetic field and heat transfer, and then structure, vibration and acoustic analyses were conducted for preferred solutions at the Parato front of design space. As a result, the optimization design was found as the tradeoff solution with suppression of temperature rising, and strength and vibration and noise were also confirmed.

Photoablation propulsion is effective for adjusting or re-entering space debris. Short-wavelength light offers advantages for generating thrust efficiently. We measured thrust from ablating an aluminum pendulum with intense pulsed extreme ultraviolet (XUV) radiation for the first time. The momentum coupling coefficient was 1.48 × 10^-5 N/W at a scaling parameter I λ ̛√τ of 10, lower than cutoff values reported with 248nm laser ablation in previous works. Our findings suggest the potential for efficient propulsion through XUV photoablation.

Transonic buffet is an oscillating shock wave phenomenon generated on the upper surface of a wing. A Gurney Flap (GF) has recently been studied as a device that can suppress the transonic buffet. In this study, we numerically analyzed the influences of the GF arrangements on the transonic buffet characteristics, in which the GF is attached at the trailing edge of the wing in the upward or downward vertical directions. When the GF with height of 2%c (where c is the chord length) was attached vertically downwards, the lift coefficient increased by 26% relative to the clean wing case (with no devices attached). In this case while the lift-to-drag ratio decreased by 14%, we succeeded in reducing the buffet amplitude by 35%. On the other hand, attaching the same flap in the upward direction improved the lift-to-drag ratio by 7% compared to the clean case, and succeeded in suppressing transonic buffet.

This paper presents a reference profile used for a guidance and control system of a space transportation system during the terminal area energy management (TAEM) phase. In the TAEM phase of the return flight, it is difficult to determine a reference profile in advance because of the large variations in terms of the initial position and velocity. Therefore, a reference profile must be generated sequentially according to the initial state. This paper describes a simple reference profile generation method with the multiple virtual cylinders. By use of the Monte Carlo simulations, we confirmed that the proposed method could be able to cope with the assumed variations of the initial state.

The temperature distribution of the discharge field was measured based on the local shock velocity by using the high-speed camera, non-intrusively. Even though this method has some rooms for the improvement of the measurement accuracy, the results suggest that this method is promising for the non-intrusive temperature measurement method around the discharge field. From the present study, it is shown that the incident shock propagation Mach number M₁ should be selected carefully for the improvement of the measurement accuracy, because the parameter M₁ becomes trade-off between the temperature measurement accuracy and the measurement spatial resolution.