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Multifilament Tether for Electric Solar Wind Sail
Keywords: Multifilament Tether, Electric Solar Wind Sail, wire-to-wire bond
An ultrasonic wire-to-wire bonding technique was developed to produce multifilament tether from 25-50 µm diameter Al wires. One hundred 20 km long tethers are needed in a full-scale Electric Solar Wind Sail. Our automated tether factory employs an industrial 60 kHz ultrasonic wire bonder featuring a customized 3 wire wedge to produce a 4-wire tether. So far 10 m 2-wire tether has been produced by bonding a 25 µm diameter loop wire to a 50 µm diameter base wire. Currently we work on the 4-wire tether fabrication technique as well as on quality assurrance based on non-destructive online laser-acoustic and contact-resistance probing of the wire-to wire bonds. Destructive pull testing serves as gold standard to assess the quality of the produced wire-to-wire bonds. We achieve 11.6 ± 0.8 g maximum sustainable pull force by using a customized bonding wedge. It features with grooves along the wire direction, large 51 µm front and back radii in the foot. We also employ a specially designed wedge to hold the 50 µm wire firmly in place during the bonding. Our current bonding speed is 6 bonds per minute in the automated 2-wire tether production.
Henri Seppänen, Recearcher
University of Helsinki
University of Helsinki, Helsinki FIN-00014

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