The satellite communication system without ground antennas is highly beneficial to ease construction and maintenance of the ground station. To realize it, the Iridium communication service which is consisted of 66 satellites on the LEO (Low-Earth Orbit) is focused. The telemeter and command data are transmitted and received through the Internet, Iridium ground station, and Iridium satellites. Then, only a PC connecting to the Internet is required for the present telecommunication system. To demonstrate this concept, the EGG (re-Entry satellite with Gossamer aeroshell and GPS/iridium) nanosatellite mission was conducted in 2017, which is the first satellite operated via only the Iridium SBD (Short Burst Data) communication. In this paper, the communication performance of the Iridium communication applied to LEO satellite is investigated and the EGG mission result is described. Trajectory-based simulation shows that the present system will function well even under the Doppler shift criteria, though the available time rate will be degraded. Actually, it worked successfully on the EGG mission regardless of the satellite location. Moreover, the telemeter data was acquired in semi-real time manner on the atmospheric-entry phase, which is very difficult for the ordinary ground antenna system. This should be the important feature of the present system.
The re-entry capsule tracking system is proposed as a shared/dual-use technology with commercial products. This system has portability, and is not affected by the condition of installed equipment in the capsule. In this paper, the detection performance is described about the tracking area assumed from Hayabusa's achievement. By the experiment using the prototype radar, this system was confirmed to be able to detect more than 90% of the area.
The electrodynamic heat shield is new type of heat protection system for atmospheric-entry vehicle, which utilizes the Lorentz force acting on the weakly ionized plasma flow inside the shock layer. A huge amount of calculation is necessary to estimate overall effect of the electrodynamic heat shield, because its effect interacts with the atmospheric-entry trajectory. In the present study, the Viscous Shock Layer (VSL) analysis method for electrodynamic heat shield is proposed for the quick analysis, which can calculate much faster than Navier-Stokes (NS) simulation. For this purpose, the VSL equations for the electrodynamic heat shield analysis are introduced under the ideal gas assumption, including circumferential momentum equation and Maxwell equations. The new method is also proposed to solve the new VSL equations. By the comparison to the NS simulation, the new VSL method gives good estimations of drag force and wall heat flux for wide ranges of interaction parameter and Hall parameter although the slight difference of wall heat flux at the stagnation point is observed. Therefore, the present VSL method could be applicable to the estimation tool of the electrodynamic heat shield effect.
RIPAL (Radio-frequency Inductive Plasma Accelerator with Low-aspect ratio plasma) has been proposed as a full-electrodeless plasma thruster. RIPAL has two radio-frequency coils of a generation coil and acceleration coil. The two coils could produce a steady state thrust. In this paper, we demonstrated the steady-state operation of 500W-class RIPAL and measured the thrust by using the target-type-thrust-stand. The experiment in the acceleration coil frequency of 697kHz and 869kHz was performed. We obtained the maximum acceleration thrust of 107μ N at the effective acceleration input power of the acceleration coil of 300W.