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A 3D-printed resistojet, wherein the heater and flow path were united, was produced. The heater consists of multi-layer shells and is difficult to break down. In this paper, the thermal design and the results of the thrust measurement are reported. The measured electrical resistance matched with the predicted one. Both the heater and the thrust reached 70 percent efficiency when paired with a nitrogen propellant at a mass flow rate of 0.2 g/s., AIAA 2018-4907 Session: Micropropulsion II

The payload capacity of launch vehicles must be increased in order to allow the exploration and development of space to be extended from low-Earth orbit into the solar system. A propellant system using a cryogenic fluid such as liquid oxygen or liquid hydrogen must reduce the amount of unusable propellant due to evaporation and boiling. However, in the space exploration and development where safety and reliability of missions are critical, predictions of the boiling heat transfer of the present technology are not sufficiently reliable for thermal management design due to a lack of knowledge and relevant research. Therefore, the objective of this research is to understand and accurately predict boiling heat transfer by developing numerical simulation tool for two-phase flows that consider phase change. In this paper, some recent research activities toward the development of chill-down process simulation technology are presented.

Accepted: 2005-10-02, 資料番号: SA1000531000

High power electric propulsion system is strongly required for future orbital space transportation. MPD (Magneto-Plasma-Dynamic) thrusters and DC (Direct Current) arcjets with hydrogen as a propellant are promising candidates for the missions because of their high performance and adaptability to high power operation. However, to use hydrogen for long term orbital missions, its storage in orbit is crucial issue to be considered. Firstly, we proposed a hydrogen storage and feed system for electric thrusters by applying our technologies derived from the liquid hydrogen launch vehicles. Secondly, we present R&D activities of hydrogen MPD thruster and DC arcjet, especially focusing on the improvement of their performance and durability. Then, development strategy of hydrogen electric thrusters is also discussed. Finally, advantages of hydrogen electric thruster were shown compared with conventional xenon thrusters through mission analyses of lunar orbit insertion and GTO-GEO transportation.

Joint Propulsion Conferences, 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference（July 14-17, 2013.), San Jose, California, United States., During rocket flights, ionized exhaust plumes from solid rocket motors may interfere with radio frequency (RF) transmission under certain conditions. To clarify the physical process involved and to establish the estimation methodology, a plume-RF interference experiment during a sea-level static firing test of a full-scale solid rocket motor was conducted. The result of the ground experiment was adequately matched by a computational fluid dynamics (CFD) model of the plume flow field coupled to a finite-difference timedomain (FDTD) model of RF transmission. The CFD/FDTD coupling method was then refined for predicting interference and RF attenuation levels during an actual rocket flight.The calculated far-field received levels were compared with the in-flight attenuation data at different look angles (angles between the vehicle axis and the line-of-sight of the antennas).The calculated results showed good agreement with the flight data over a wide range of look angles. An adaptation of the model, based on the diffraction theory, proved appropriate both for rough estimation of attenuation and for conducting a preliminary analysis of signal/rocket plume interactions., 資料番号: AC1400047000, レポート番号: AIAA2013-3790

In rocket flights, ionized exhaust plumes from solid rocket motors may interfere with RF transmission under some conditions. In order to clarify the important physical process involved, microwave attenuation and phase delay due to rocket exhaust plumes were measured during sea-level static firing tests conducted on two types of full-scale solid propellant rocket motors. The measured data were analyzed by comparing them with numerical results such as flowfield simulations of exhaust plumes and by employing a detailed analysis of microwave transmission by using a frequency-dependent finitedifference time-domain (FD2TD) method. The results revealed that either the line-of-sight microwave transmission through ionized plumes or the diffracted path around the exhaust plume mainly affects the received RF level, which depends on the magnitude of the plasma RF interaction. For the actual launch vehicle flight, the transmission process is dominated by the diffraction effect so that we applied a two-dimensional diffraction theory to analyze the communication between a vehicle and a ground station. The attenuation levels estimated using diffraction theory agree with the data recorded in-flight.