National / Science & Health

Japanese sword-making techniques tapped for asteroid exploration


Researchers are looking to adopt the technology used to make Japanese swords in an effort to collect geological samples from an asteroid.

Hayabusa2, an asteroid explorer developed by the Japan Aerospace Exploration Agency (JAXA), is expected to make the first landing on its target, Ryugu, in late October. It is slated to land on the asteroid three times to collect samples, mainly using explosives.

The first Hayabusa explorer, which landed on asteroid Itokawa in 2005, brought back only limited particles, but Hayabusa2 is planned to launch an explosives-laden impactor to create a crater on Ryugu’s surface before particles are collected.

Separately, a group of researchers including Takeo Watanabe, an associate professor at Kanagawa Institute of Technology, is working on a project to enable a future space probe to collect samples from an asteroid in an even more distinctive way.

The group aims to collect samples using a corer with a blade made from the same material that is used to manufacture Japanese swords — and using the same methods as is used to make the finely crafted weapons — so that the device can penetrate as deep as possible and collect as many samples as possible efficiently, Watanabe said.

The team asked Genrokuro Matsunaga, a 70-year-old swordsmith in the city of Arao, Kumamoto Prefecture, to make the blade.

He collected iron sand from a beach on the Ariake Sea facing Kumamoto and made a lump of iron using the traditional tatara process, in which it is heated in a furnace. The lump of iron was then tempered repeatedly and made into tamahagane, the steel material that is used to make Japanese swords.

The tamahagane was processed into a cylindrical form at the National Institute of Technology at Ariake College in the city of Omuta, in neighboring Fukuoka Prefecture. Its polished cutting edge, which is 25 millimeters in diameter and 20-30 millimeters in length, was tempered by Matsunaga to increase its strength with the yakiire process, in which it was heated to high temperatures and then cooled quickly.

Watanabe’s group began their research in around 2006. As they tried to make a sharp cutting edge that could penetrate as deep as possible, the team came across the techniques used for Japanese swords.

“I feel the cultural significance of aiming for space exploration by employing traditional Japanese technology,” he said.

The group has so far made about 20 cutting edges each shaped differently and manufactured at different temperatures using the yakiire process, and has carried out tests on simulated asteroids.

Matsunaga agreed to take part in the project without hesitation. “It’s intriguing that the expertise for traditional Japanese swords that cut well and do not bend or break could go to space, combined with state-of-the-art technologies.”

The project is a venture “to an unknown world and is interesting for me as a swordsmith,” he added.