One kilometer (1km) ESAIL tether produced automatically

The electric solar wind sail (E-Sail) is a space propulsion invention exploiting the dynamic pressure of the solar wind. It uses centrifugally stretched positively charged conductive tethers to create thrust from the momentum flux of the solar wind. In space the tethers must be micrometeoroid resistant. We use ultrasonic bonding to create an aluminum multiwire Heytether structure to address this issue. For this work we produced a 1 km continuous piece of multifilament E-Sail tether of µm-diameter aluminum wires using a custom made automatic tether factory. The tether comprising 90704 bonds between 25 and 50 µm diameter wires is reeled onto a metal reel. The total mass of 1 km tether is 10 g. We reached a production rate of 70 m/24 h and a quality level of 1 ‰ loose bonds and 2 ‰ rebonded ones. Thus, we demonstrated that production of long electric solar wind sail tethers is both possible and practical. Based on images captured of each bond, a post production analysis was done to determine failure rate and types of the failures that occured during the production