The long-bladed katana swords, famously used by Japan’s samurai, are still produced today by licensed craftsmen using traditional techniques. The methods are centuries old, but as BBC Future Now recently discovered, scientists are now exploring whether this steelwork could also aid the design of future space probes aiming to remove material from asteroids. View our gallery below to see the incredible work that goes into the manufacture of these weapons.
The blades are forged from tamahagane steel, smelted from ‘iron sands’ over several days to remove impurities and even out its carbon content (Credit: Getty Images)
The blades are forged from tamahagane steel, which is produced by smelting ‘iron sands’ over several days to remove impurities. During smelting, the smith will also add charcoal, aiming for a carbon content of around 1% to achieve maximum strength (Credit: Getty Images)
Before it enters the furnace, the swordsmith covers the blade with clay. This ensures the edge hardens more than the spine, which creates the sword's curve (Credit: Getty Images)
The swordsmith covers the blade with a clay slurry, using a thinner layer at the edge and a thicker layer towards the spine to control the temperature distribution across the steel as it is goes in and out of the furnace (Credit: Getty Images)
The tamahagane is heated and quenched many times as the swordsmith forges the blade (Credit: Getty Images)
The tamahagane is heated and quenched many times - a process that alters the molecular form of the steel. Thanks to the clay slurry applied before heating, the different parts of the blade set into different crystal structures, with a particularly hard form of steel, known as martensite, at the edge of the blade, and a softer structure along the spine. The resulting difference in densities also causes the blade to curve, creating its iconic shape (Credit: Getty Images)
Each blade may take a month to produce through many iterations of this process (Credit: Getty Images)
Each blade may take a month to produce through many iterations of this process (Credit: Getty Images)
The swordsmith Munehiro Myochin polishes a blade at his workshop in Himeji, Japan (Credit: Getty Images)
The swordsmith Munehiro Myochin polishes a blade at his workshop in Himeji, Japan (Credit: Getty Images)
The dark line down the middle of the blade represents the point at which the harder steel on the edge meets the softer steel on the spine (Credit: Getty Images)
The dark line - known as the 'hamon' - down the middle of the blade represents the point at which the harder (but more brittle) steel on the edge meets the softer (but more flexibile) steel on the spine. Besides leading to the curved shape, it is this combination that lends the sword its strength and resilience (Credit: Getty Images)
Besides helping to keep alive an ancient tradition, this knowledge steelwork might just help Japan’s space programme (Credit: Alamy)
Besides helping to keep alive an ancient tradition, this knowledge of steelwork might just help Japan’s space programme. To read more, follow the link in the introductory text (Credit: Alamy)