The centripetal acceleration of an object is given by the relation,

where Ac = centripetal acceleration =
R = radius of rotation = 15 m
V = speed of astronaut
Hence, 
solving this we get, V = 38.34 m/s

According to above question ~
Let's find the charge (q) by using formula ~
Hence, 12 coulombs of charge flow past any point in the wire in 3 seconds