Improved Electrostatic Shield for Lunar Dust Entering into Mechanical Seals of Equipment Used for Long-Term Lunar Exploration

It has been known that the dust on the Moon can cause serious problems for exploration activities. One of the major problems is that airborne dust enters into gaps of bearings and mechanical seals; such a situation could lead to catastrophic damage. To overcome this problem, we have developed dust shield systems utilizing electrostatic force for long-term lunar surface exploration. In our earlier system, a single-phase rectangular high voltage was applied to insulated parallel plate electrodes printed on a substrate at the clearance of the mechanical sealing part. It was demonstrated that more than 70% of the dust was repelled from the gap; however, because the performance of this system was not satisfactory, we have developed two improved systems. One of the improved systems uses a double-electrode con- figuration. We added support electrodes outside of the main electrodes so that the improved system generates a wider electrostatic field. As a result, more than 80% of the dust was re- pelled from the clearance. Another improved system uses a screen electrode configuration. In addition to the parallel plate electrodes, parallel screen electrodes were added near the gap. It was demonstrated that more than 90% of the dust was repelled from the clearance. The motion of dust particles near the electrodes was observed directly with a high-speed mi- croscope camera, and it was clarified that dust particles entering into the clearance were ejected through openings in the screen electrodes. A numerical calculation using the hard- sphere model of 3D distinct element method confirmed the observed result, and it was pre- dicted that the cleaning performance would be further improved in the low-gravity and vac- uum environment of the Moon. It was also demonstrated that the performance of this system is not reduced by the rotation of a shaft and that the power consumption is extremely low, approximately 1 mW/m. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.