unity – Why the transform is not rotating at all?

private FixedUpdate()
{
 Vector3 direction = new Vector3(0, spaceShip.rotation.y, 0);
 Quaternion targetRotation = Quaternion.Euler(direction);
 transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, Time.deltaTime * rotationSpeed);
}

I want that the transform to rotate smooth slowly only on the Y towards the spaceship.
but the transform is not rotating at all.