With the progress of human activities in space, the occasion to handle liquids in non-uniform acceleration or low-gravity is now growing. On the launch vehicles with liquid propulsion system, the dynamic acceleration during its powered ascent or ballistic flight makes it very difficult to control the position of propellants in the tanks. For the establishment of the technology for the management of liquid propellant in space vehicles, a numerical method, called ‘CIP-LSM’ (CIP based Level Set & MARS), was developed to simulate three-dimensional free-surface flows under various gravity conditions, which has been applied to clarify the dynamic behavior of liquid propellant in the tanks of launch vehicles.

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A liquid oxygen supply system for a small-scale sounding rockets was developed. The sounding rokets are hybrid type employing a combination of plastics (PMMA or high density polyethylene) and liquid oxygen as propellants. Key points for the miniaturization were using no valve in the liquid oxygen feeding line and omitting precooling treatment of the line. Without precooling treatment, the liquid oxygen in the feeding line becomes multiphase flow until the temperature of the feeding line falls below the boiling temperature of the liquid oxygen. A characteristic time of multiphase flow duration was proposed to evaluate the duration a multiphase flow holds in the feeding line. Static firing tests showed that the multiphase flow ends within the half the characteristic time, showing that the liquid oxygen flow rate history without a precooling treatment is acceptable for an actual operation of the rocket motor. Finally, an impinging type injector was developed to remove a combustion instability, caused by a coupling of the combustion chamber pressure and the propellant (liquid oxygen) feed system.

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In the current Air Traffic Management (ATM), pilots must fly following the instructions of air traffic controllers, who check the air traffic information via radar displays on the ground. However in the future, pilots would have the means to see what is around them based on Aircraft Surveillance Applications System (ASAS), which will help pilots to better understand the surroundings of the aircraft. By applying ASAS, the way to control air traffic makes a shift to a distributed control based on each pilot' s decision, instead of a centralized control which is currently done by air traffic controllers. This paper introduces our ASAS studies and the state-of-the-art of evaluating the mixture of the distributed and centralized control in the future ATM system.

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Development of closed-loop air revitalization producing oxygen (O₂) from carbon dioxide (CO₂) exhaled by astronauts is required for future manned space missions. This paper shows recent research on two of three subsystems of a closed-loop air revitalization system: water generation form CO₂ reduction and water electrolysis to provide O₂. Practical large-scale tests of CO₂ reduction and water electrolysis showed that various gas-liquid two-phase conditions in a reactor would be important to establish systems operated under microgravity.

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Butterflies fly by combining wing flapping and gliding efficiently and have beautiful flight patterns. Moreover, the butterfly excels in rapid acceleration and turning. A number of studies on the mechanism of butterfly flight have been carried out in recent years. Moreover, a number of recent studies have examined the flow field around an insect wing. However, the dynamic behavior of the vortex formed on the insect wing and its growth process have not yet been clarified. The present authors conducted a flight observation experiment and clarified the behaviors of its wings in flight. Based on these results, we developed a flapping-wing robot without tail wings, which is similar to a real butterfly. The elastic deformation of the wings was found to be an important parameter for stable flight, and we focused on the flow field around the wings created by the flapping motion and its elastic deformation. The authors conducted a particle image velocimetry (PIV) measurement around the flapping butterfly wing of Idea leuconoe and investigated the vortex structure of the wing and its dynamic behavior. A vortex ring is formed over the butterfly wings when the wings flap downward to the bottom dead position. The vortex ring then passes over the butterfly completely and grows until reaching the wake at the bottom dead position. The vortex ring is formed over the wings regardless of the type of butterfly, although the scale of the vortex ring varies with the butterfly type.

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MON3 is used as a propellant for the bipropellant thruster in the spacecraft propulsion. MON3 is Nitrogen Tetroxide (N₂H₄) with 3wt% solution of NO. Heat transfer characteristics with boiling of the MON3 have been measured. The critical heat transfer was identified when the superheat temperature was around 50 ℃ (degree C) under different flow parameters. Pressure vibration from 8 to 22Hz frequency was observed in the specific flow parameters during the boiling of MON3. These frequencies are in good agreement with that of combustion perturbations observed in the test injector which simulated the actual bipropellant thrusters.

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It is expected to manufacture new materials with container-less processing by levitation techniques. However, it is indicated that the levitated droplet with levitation technique has nonlinear behavior. In this study, nonlinear dynamics of the levitated droplet is experimentally and analytically investigated. The levitation experiments with the ultrasonic levitator and electrostatic levitator are conducted under the reduced and normal gravity condition. Based on the experimental results, theoretical analyses are compared to clarify the nonlinear dynamics of the levitated droplet. Furthermore, new technique to manipulate the thermofluid process of levitated droplet and measure the viscosity in high viscosity region are proposed by levitation techniques.

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Ecotype water turbines can be utilized small and distributed water resources with little civil engineering works and without environmental burdens. In Japan, network of agricultural waterway extends 400 thousands kilometers, this abundance of waterpower has a high expectations for electric power generation. The turbines will promote local production for local consumption of electricity. Waterfall type turbine and undershot turbine are investigated and demonstrated in some field tests. These are opened type which has no casing and any water pipes. We summarize our results of the investigation of eco-friendly water turbines.

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A technique is proposed to improve the collection efficiency of a small amount of volatile organic compounds, especially explosive materials, in the gas by impinger, which is generally used as gas collection device for analysis. Eugenol was used as a simulated substance of explosives. The sample gas containing specific amount of eugenol was collected in pure water by the impinger. The concentration of eugenol in water was measured by gas chromatography. The experimental results show that the collection efficiency of eugenol by the impinger increased as the water level (volume) increased. The bubble motion in the impinger observed by high-speed photography indicates that the averaged values of equivalent diameter and rising velocity of bubbles were reduced as the water level increased. This reduction yields the increase of the resident time of bubble per unit volume of water, which enhances the dissolution of eugenol. On the basis of these characteristics, small glass beads were stuffed into the impimger to increase the resident time per unit volume. The collection efficiency per unit volume of water was greatly improved by stuffing the glass beads. Finally, the cleaning-in-place process of the impinger was also achieved by intermittent gas supply under the continuous water supply.

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