MUSES-C Monthly Report No. 5
ISAS
May 2, 2003

One month has already passed since the MUSES-C explorer was delivered to KSC in Uchinoura. In that time, we loaded the Xenon gas to be used as the ion-engine propellant, and the Hydrazine (propellant) and Nitrogen Tetroxide (oxidizer) for the explorer's chemical propulsion system. Since the fuels for the chemical propulsion system are liquid, the filling operation was completed in a short time. The Xenon gas, however, had to be cooled repeatedly and therefore took a few days to load. Both operations went very smoothly, and we were able to finish one day ahead of schedule. Carrying three chemicals on board is one of the unique features of MUSES-C. The chemical fuels weigh 130 kg, one-fourth of the explorer's total mass. MUSES-C was then connected to the KM-V2, the rocket's 4th stage kick motor, via a joint, and the nose of rocket was connected to the 3rd stage in the clean booth. The final operation will be the assembly of all stages in the rocket assembly building.

MUSES-C uses a 3-axis stabilization system because the explorer must be accelerated to the specified direction by the ion engine. This is the first time this system has been introduced to an explorer in Japan. For 3-axis stabilization explorers such as MUSES-C, a special technique is employed in order to extract only liquid from the tank. Centrifugal force is used to isolate liquid and gas with spin-stabilized satellites, but MUSES-C uses a flexible partition wall called a "bladder." Moreover, in order to prevent changes in the center of gravity, explorers usually have plural tanks located around its center of gravity. MUSES-C, however, adopts one tank for one chemical (i.e., a total of three tanks), thus reducing the number of tanks and piping. The tanks may appear to be placed at random, but are in fact positioned according to our latest idea, one of the unique features of MUSES-C. Unfortunately, the tanks are now invisible since they were already installed inside the panels.

By the time this article appears on the web, MUSES-C will be launched and ready for ion-engine acceleration.