Requiring power far from the earth, spacecrafts have progressed over time by skillful use of a variety of cells. At the moment, ways to make full use of the lithium-ion secondary cell are an important research theme in space power-supply technology. We also have to raise the level of fuel-cell technology. To cope with larger-scale spacecraft, we believe that a regenerative-type fuel cell in combination with water electrolyzer will be introduced sometime in the future.
Is there not another electricity-storage system apart from cells? This is also an important issue for us. One example of the system is the electric double-layer capacitor. It stores electricity in a double-layer region of the electrode surface, enabling rapid charge and discharge compared to cells. It is also believed that the system has the durability to withstand a charge/discharge frequency about 10 to 100 times greater than secondary battery cells. We are now researching whether it can be developed into a mature technology to support future spacecraft.
Like other technologies, there is no almighty electricity-storage system that can be installed on spacecraft. Some technologies may decline over time. Some technologies may have problems in practical use, despite the hopes placed on them. Since electronics cannot operate without electricity, battery technology is one field where progress is expected.
In memory of Saburo Kuwashima
Saburo Kuwashima, the leader of the Electronics Engineering Group, Institute of Space Technology and Aeronautics, JAXA, passed away on September 15, 2004. He had devoted his life to research and development of batteries for space and contributed to the advancement of power-supply system technology, one of the pillars of spacecraft. As one of his followers, I would like to express my deepest sympathies and offer my prayers for his soul.
Mr. Kuwashima, I imagine that you are concerned about things left undone, but please leave it to us. Rest in peace and watch over us from space.