This paper is concerned with the numerical analysis of the hypervelocity impacts (HVIs) of a projectile on laminated metallic plate targets. Laminated metallic plates have some potential advantages to increase ballistic resistance if the plates are optimally laid up. To analyze the HVI phenomena, a Smoothed Particle Hydrodynamics (SPH) method improved by using new particle generation and particle reducing techniques is applied, and a numerical lamination model for the SPH method is presented to introduce the discontinuity of stresses between the each layer of the laminated metallic plates. As examples, the numerical simulations are carried out for a steel or aluminum projectile striking to laminated aluminum plate targets with several different layup configurations. Through the numerical simulations, it is seen that the present method can describe the characteristics of the HVI phenomena of the projectile on the laminated metallic plate targets.
The subsonic flow for a 45 deg-swept delta wing was numerically simulated to see the effects of rotational leading edges on aerodynamic forces. In the present study, part of the cylindrical leading edge can be rotated which extends from x=0.25C to 0.90 C. The computation has been performed at an angle of attack of 20 deg and a Reynolds number of 2.0×104 based on the maximum wing root chord. Under these conditions, the flow is fully separated from the wing surface in the case without leading edge rotation, so that no suction peaks due to leading edge vortices appear over the upper surface of the wing. Consequently, the delta wing will not have an effective vortical lift. In the case of steady rotation, leading edge vortices were produced on the wing in the early stage. However, a gradual drop in lift coefficient occurred as a result of the diffusion of these vortices. By contrast, in the case of unsteady rotation, a pair of leading edge vortices was maintained, so that a higher lift was produced. Consequently, the lift coefficient became more than 40% higher than that of the plain delta wing.
In this paper we propose a new method known as “the stacking method” for detecting small pieces of unknown GEO debris, in which several images taken using a CCD camera are used to detect this debris. With this method, the streaks of stars are eliminated completely and there is a significant decrease in sky background fluctuation. This makes very dark debris not visible on a single image detectable. We tested this method using the 45 cm telescope at the Yatsugatake Observatory and a small CCD camera. One possible piece of GEO debris of about 1m in size was detected as a result of analysis using the stacking method. With this method, observation using the facilities at the Bisei Space Guard Center, a 1m telescope and a SITe CCD camera, may be expected to detect GEO debris of around 10cm in size.
A modified sidewall-compression-type scramjet engine was tested under M8 flight condition. A strut with a long tail led to a 60% higher maximum thrust increment than a strut with a truncated tail, while allowable fuel flow rate (i.e., the flow rate at engine unstart limit) was almost identical. To increase the allowable fuel flow rate and the maximum thrust increment due to combustion without engine unstart, distributed injection in vertical direction and installation of ramps in the isolator between the inlet and the combustor were applied. Distributed fuel injection led to a 30% higher maximum thrust increment than the uniform fuel injection, and the installation of the ramps also gave a 30% higher one than that in the engine without ramp. Gas-sampling at the exit of the engine with distributed fuel injection showed 88% of bulk combustion efficiency. Specific impulses of the maximum thrust increments, δIsp , of the modified engine were 60–80% higher than that of the original engine.
Operations under single pilot instrument flight rules for general aviation aircraft is known to be one of the most demanding pilot tasks. Scanning numerous instruments plays a key role for perception and decision-making during flight. Flight experiments have been done by a single engine light airplane to investigate the pilot eye scanning technique for IFR flights. Comparisons between the results by an actual flight and those by a PC-based flight simulator are made. The experimental difficulties of pilot eye scanning measurements during the actual IFR flight are discussed.
A system to identify the position where arc discharges occurred on a solar array in vacuum has been developed. The system is composed of a video camera, an A/D converter, a personal computer (PC) and a computer program. Analog video image of the solar array from the video camera is converted to digital one by the AD converter. The digital video image is recorded directly on a hard disk drive connected to the PC during an experiment without dropping any video frames. After the experiment, a picture image is extracted in memory bank from the stored video image by the computer program and is compared with a first frame of the video image. The position of arcs is identified by means of repeating this comparison over all frames. The system is built at a low cost with commercial hardware and reduces the time required for analysis remarkably.
A Pulsed Plasma Thruster (PPT) is one of the most attractive propulsion devices for stationkeeping, attitude control and main thrusters of small satellites, because it is compact and light. On the other hand, thrust efficiency is generally low among electric propulsion systems, mainly owing to poor propellant utilization. In this study, a Liquid Propellant PPT (LP-PPT) is designed to develop a microthruster that controls mass flow rate to enhance thrust efficiency. Liquid is suitable for propellant, since a LP-PPT would be more compact and lighter than a PPT with gas propellant, which requires a high-pressure reservoir. A LP-PPT has an intermittent injector to supply liquid propellant to an interelectrode region. A PPT with pulsed feeding of liquid propellant has never been studied. With a designed thruster, it was checked that discharge is initiated with methanol propellant of 3.9μg at a capacitor stored energy of 13.5 J. Thrust-stand measurements yield an impulse bit of 57μNs, corresponding to a specific impulse of 1500 seconds and a thrust efficiency of 3.1%.