Luke Skywalker fires a torpedo into an exhaust port, which not much bigger than a womp rat (1.33 m). How long does it take for the torpedo to reach...

 Luke Skywalker fires a torpedo into an exhaust port, which not much bigger than a womp rat (1.33 m). How long does it take for the torpedo to reach the main reactor of the Death Star...according to physics? Assume that the torpedo is released from rest on the surface of the Death Star, which is a sphere with radius of 170 km and mass of 3.87×1016 kg with a uniform density. It then falls through a straight, radial shaft into the centre of the the Death Star, where the main reactor is located. Express your answer in seconds