Travel times for system ships

<div>For the life of me I can't remember if there are any distinct rules for the time needed for a system ship to travel X amount of distance. I'd like to think that this type of ship is faster in SF than in it is in our current time, but I don't know if that's possible. KH states that these ships have chemical drives, but I was wondering if they could have an ion drive instead - possibly if it made them faster.</div><div><br /></div><div>I ask as I have an adventure in development where I want the players to travel in a CDC system ship to an asteroid belt at the edge of a system. I wasn't sure how long this would take, but was imagining an HS:4 ship that either has chemical or an ion drives.<br /></div>