Arc initiation phenomena by space GHTA welding process using touch start technique in a vacuum

The space GHTA (Gas Hollow Tungsten Arc) welding with a high-voltage high-frequency device for arc initiation may cause electro-magnetic noise problems for the computer equipment placed on the ISS (International Space Station). It was also clear from the experiments using a high-voltage DC device for arc start at the ISS orbital pressure, that there is a shifting phenomenon in which a spark discharge shifts to either a glow discharge or an arc discharge when starting the arc. Welding projects around the ISS in space need an arc discharge and a device which does not produce electro-magnetic noise for arc start. Therefore, in this report, arc starting experiments of the space GHTA welding using a touch start technique for arc start were carried at the ISS orbital pressure, 105 Pa. As a result, the space GHTA welding using a touch start technique can be used for arc initiation when welding at the ISS orbital pressure. It was also clarified that the application of the touch start technique is optimum in order to use the space GHTA welding process in space.