Issue with physics?

A(n) 65.0 kg astronaut is working on the engines of a spaceship that is drifting through space with a constant velocity. The astronaut turns away to look at Earth and seconds later is 30.0 m behind the ship, at rest relative to the spaceship. The only way to return to the ship without a thruster is to throw a 0.430 kg wrench directly away from the ship. If the astronaut throws the wrench with a speed of 15.0 m/s, how long does it take the astronaut to reach the ship?