Ballooning Instability as a Mechanism of the Near-Earth Onset of Substorms

After introducing a mathematical definition of the tail-like equilibrium and the dipole-like equilibrium in the magnetosphere, it is shown by using physical intuition based on the Energy Principle that the incompressible assumption for the ballooning instability is more valid for the tail-like configuration when the unstable ballooning mode is strongly localized near the equator. Therefore, before the substorm onset, the near-Earth plasma sheet becomes more tail-like and more likely to be subject to the ballooning instability without the stabilizing influence of the compressibility, when the critical plasma due to the stabilizing tension force is exceeded. The onset of the ballooning instability in the near-Earth plasma sheet seems promisingly relevant to the substorm onset phenomena. Also, the effect of the stochastic plasma dynamics on the ballooning and interchange instabilities is clearly shown.     

Mercury Dust Monitor (MDM) Onboard the Mio Orbiter of the BepiColombo Mission

Space Science Reviews - In this chapter, we review the contribution of space missions to the determination of the elemental and isotopic composition of Earth, Moon and the terrestrial planets, with...     

KIBO (Japanese Experiment Module in ISS) operations—2008/3–2009/10

Japan Aerospace Exploration Agency (JAXA) launched its own first manned experiment facility in space called the KIBO (Japanese Experiment Module, JEM) in 2008 and 2009 and started operations as part of International Space Station (ISS). To accomplish this Operation, JAXA made its own ground facility in Tsukuba, Japan, called Space Station Integration and Promotion Center (SSIPC). Ground personnel at SSIPC called the JEM Flight Control Team (JFCT) operate the KIBO and have learnt many lessons during its operation. In this presentation, some topics are chosen and explained such as (1) crew/ground personnel interaction and (2) planning lessons learned for manned space activities.     

Effect of liquid bridge form on oscillatory thermocapillary convection under 1 g and μg conditions

This study analyses the effect of temperature difference between hot and cool disk (ΔT), and non-dimensional liquid bridge volume (V/V_o) on the transition process from steady thermocapillary convection to periodic or chaotic thermocapillary convection in a liquid bridge modeled after the floating zone method under normal gravity and microgravity conditions. From normal gravity and drop shaft experiments, the difference of the regime of the steady state and the oscillatory state was clarified on the ΔT−V/V_o plane under 1 g and μg conditions. A gap or stability region was observed in the specific V/V_o range under 1 g conditions. In the gap or stable region, after the gravity changed from 1 g to μg conditions, the temperature signals showed oscillation. From these results, the critical temperature difference under the μg conditions appeared to be smaller than that under the 1 g conditions. Temperature signals were defined as 6 different types of states. The various temperature oscillatory state regimes were obtained on a ΔT−V/V_o plane under 1 g and μg conditions. Under μg conditions, in these experimental conditions, all temperature oscillatory states exhibited only the Periodic state.     

Considerations of design for life support systems.

During the design phase for construction of artificial ecosystems, the following considerations are important. (1) Influences on living things in the ecosystem, such as lifestyles and physiological functions caused by stresses due to environmental changes. The long stay in the artificial ecosystem has a possibility to lead to evolutional change in the living things. (2) The system operation method in trouble, which relates to maintainability. (3) The system metamorphosis according to new technologies. (4) Route minimization of material flow that leads to an optimum system layout.     

Small cryogenic propulsion unit for upper stage application

The feasibility study was conducted to use the cryogenic propulsion system for the third stage of the future H-1 vehicle. While the $\text{LO}{}_2\text{LH}{}_2$ third-stage mass fraction is less than the current solid propellant third stage, the 50% higher Isp results in a significantly higher payload. Two basic configurations of the new propulsion system were proposed: one pressure-fed system and two pump-fed systems. The first is a pressure-fed system providing a 700 kg thrust at an Isp of 441 sec with restart capability. The second is a pump-fed system, operating on an expander cycle principle. A midget turbopump with a 90 000 rpm shaft speed feeds the thrust chamber which delivers 1 ton of thrust at an Isp of 471 sec. The third proposed system is also a pump-fed design using a unique expander bleed cycle, and delivers a 1 ton thrust at an Isp of 470 sec with a turbopump speed of 80 000 rpm. The results of engine testing predict the performance feasibility of respective propulsion system designs.     

Progress in design optimization using evolutionary algorithms for aerodynamic problems

Evolutionary algorithms (EAs) are useful tools in design optimization. Due to their simplicity, ease of use, and suitability for multi-objective design optimization problems, EAs have been applied to design optimization problems from various areas. In this paper we review the recent progress in design optimization using evolutionary algorithms to solve real-world aerodynamic problems. Examples are given in the design of turbo pump, compressor, and micro-air vehicles. The paper covers the following topics that are deemed important to solve a large optimization problem from a practical viewpoint: (1) hybridized approaches to speed up the convergence rate of EAs; (2) the use of surrogate model to reduce the computational cost stemmed from EAs; (3) reliability based design optimization using EAs; and (4) data mining of Pareto-optimal solutions.     

Thrust measurement of dimethyl ether arcjet thruster

The present paper describes thrust measurement results for an arcjet thruster using Dimethyl ether (DME) as the propellant. DME is an ether compound and can be stored as a liquid due to its relatively low freezing point and preferable vapor pressure. The thruster successfully produced high-voltage mode at DME mass flow rates above 30 mg/s, whereas it yielded low-voltage mode below 30 mg/s. Thrust measurements yielded a thrust of 0.15 N and a specific impulse of 270 s at a mass flow rate of 60 mg/s with a discharge power of 1300 W. The DME arcjet thruster was comparable to a conventional one for thrust and discharge power.     

Assessment of space debris collisions against spacecraft with deorbit devices

Deorbit methods have been employed to remove space debris from orbit. One of these methods is to utilize atmospheric drag. In this method, a membrane loaded into the spacecraft is expanded to increase atmospheric drag. Although this method works without requiring fuel, it has the disadvantage of a high risk of collision with other debris owing to its larger area. Area-time product and energy-to-mass ratio have been used as indices to evaluate the risk of collisions between spacecraft and debris. However, the evaluation criteria were uncertain because these two indices are independent. In this paper, we propose a new evaluation index, single-sheet collision factor (SSCF), that comprehensively evaluates the collision risk based on experiments simulating debris collisions. As a result of the hypervelocity collision experiment, we found that the penetration-area mass of the spacecraft affects the severity of debris collisions. In this paper, the product of the exterior-wall thickness, the exterior-wall density, and the space debris cross-sectional area defines the penetration-area mass of the spacecraft. Furthermore, we compare and evaluate various deorbit methods using SSCF. The comparison showed that the penetration-area mass of the SSCF could be quantitatively determined for the debris-collision severity due to difference in structural materials of spacecraft. SSCF will be used to create rules for space-environment conservation with the expansion of the space-development market.