Liquified natural gas (LNG) is one of the most promising propellant for the near future space transportation rocket engine because of its low cost and fewer handling concerns. However, for LNG propellant, erosion of engine material by sulfur (sulfur attack) is significant problems such as blockage at the regenerative cooling passage and the material strength deterioration in regenerative cooling passages. In this study, the effect of sulfur attack is experimentally evaluated for nozzle material candidate such as Inconel600 (AMS5540M) and combustion chamber material candidates such as SMC, OMC (copper-chrome-zirconium alloy) and OFHC (JIS C1020P 1/2H). And this study apply gold coating at the regenerative cooling passages of the LNG rocket engine chamber and performance of the protection method against sulfur attack is experimentally evaluated for gold coating. In the sulfur attack test, EPMA and Raman analyses indicate that metallic sulfide can be observed on the surface and cathodic reduction indicate that depth of the sulfide is between 1μm and 8μm for SMC, OMC and OFHC. Tensile test also indicates the tensile stress slight decrease with Inconel600 (AMS5540M) and SMC. On the other hand, in the coating test, formation of metallic sulfide and depth of the sulfide has been reduced by gold coating. The results of the this study shows that beneficial effect of gold coating against sulfur attack.

抄録全体を表示

To examine the possibility of sonic boom mitigation by the supersonic biplane with a fuselage, two kinds of wing-fuselage models for the ballistic range experiment were designed by using CFD simulations. One was the low-boom model with a blunt nose and the other was the high-boom model with a spike nose. From the CFD result, the near-field pressure strength from the low-boom model becomes 70% of that of the high-boom model. The far-field pressure peak of the low-boom model becomes 85% of that of the high-boom model. To verify the near-field pressure signature calculated by CFD, the experimental model using the supersonic biplane with a finite-thickness leading edge was designed and launched with the ballistic range. As a result, the reliability of the CFD result was confirmed.

抄録全体を表示

The magnetic sail is a spacecraft propulsion system using the interaction between the magnetic field and the solar wind. In this paper, to evaluate the propulsive force generated by a Pure Magnetic Sail spacecraft, a new numerical analysis model including the ion's finite Larmor-radius effect is proposed. In this analysis model, the trajectories of ion particles are solved based on the Flux-Tube model and electrons are treated as a plasma fluid under the assumption of quasi-neutrality and steady state. As for the electromagnetic field, the induction equation is employed to obtain a steady electromagnetic field. Using the Flux-Tube model, a 500-km-size magnetosphere was found to produce a thrust level of 1500N when a magnetic moment of the magnetic sail is set to 3.9×10¹⁶Wbm. This thrust level agrees well with the result obtained by magnetohydrodynamics model (1600N) and that by Hybrid particle-in-cell model including ion kinetic effects (1560N). Also, the computational cost of the Flux-Tube model is reduced to about 1/10 of that of Hybrid-PIC model.

抄録全体を表示

The present paper deals with a new analytical method to calculate electric current density between two probes in Carbon Fiber Reinforced Plastic (CFRP). Unidirectional CFRP has strongly orthotropic electric conductance. Even when electric current is applied to a CFRP plates using two probes on a single surface, the electric current density is not uniform in the cross section. The electric current concentrates near the surface where the electric current is applied. Although it is quite important to know the electric current density in the CFRP plate for the analysis of lighting effects, it is very difficult to calculate it using 3-D FEM analyses. In the present study, the orthotropic coordinate is transformed into uniform coordinate. Laplace's equation is solved using a potential theory of perfect fluid. The solved equations using an infinite-body approximation are checked comparing with FEM analyses. As a result, the new analysis method is proved to be efficient for unidirectional CFRP. The limitation of the method is also discussed here.

抄録全体を表示