Research for Secure Development and Success of Missions Advancement of basic technologies on mechanisms and materials for expanding space activities Dust-resistant environment technology for activities on lunar and planetary surfaces

Exploration of the Moon, planets, and their satellites involves the usual space environment concerns, such as vacuum and microgravity, and the unique environment of each environment. Mechanical components used in exploring are required to operate normally for the entire mission under such extreme environments. For example, dust on the surface of the Moon can be a problem. In particular, the lunar environment has a large amount of dust, known as regolith, that can be a severe problem if it gets into equipment.

We are researching three key issues in this study.
The first is research on dust seals to protect drive equipment in dusty environments such as the lunar surface. We are researching to extend the service life of rotating shaft seals to protect motors, reduction gears, and electronic equipment on the main shaft of rovers traveling on the lunar surface and seals to protect bearings.
Second, we are also researching the prevention and removal of dust adhesion.
The third issue is understanding the behavior of dust on rovers' wheels. By understanding and predicting the dispersal behavior of the dust raised during landing and rover movement, we can evaluate the effects of such dust. With these studies, we are working to improve the reliability and extend the service life of spacecraft in activities on the lunar surface and elsewhere.

Advancement of basic technologies on mechanisms and materials for expanding space activities

An example of research results

Research and Development of Dust Seals for Main Spindles

We are researching and developing several types of seals for use where reliable sealing is required, such as the drive shaft of a rover. One of these seals is a mechanical seal.

We select and develop materials and coatings that are hard and have low coefficients of friction so that regolith does not wear rover parts or cause seal performance to be lost when it enters the sealing surface between the rotating shaft and a fixed part. In addition, the pressing force and materials are optimized so that the force required for rotation is as low as possible while maintaining sealing performance. Figure 2 shows the torque transition in a vacuum dust environment while changing the temperature to the low-temperature side. Compared to the resin seals normally used, the torque remains low and unaffected by temperature. No dust ingress was observed after the test.

Figure 2: Torque evolution of mechanical seals (compared to other sealing methods)

Research and development of dust seals for bearings

We are researching two types of simple bearing seals that come into direct contact with regolith: one using a ring-shaped collar and the other made of a felt material. For the collar seal, we have designed a shape that allows the collar to hold and seal the bearing firmly at the end face and optimize the pressing force. The felt seal is a new attempt to use felt material for space applications. It rotates with less resistance while ensuring high sealing performance.

Advancement of basic technologies on mechanisms and materials for expanding space activities