That's the problem with this spelljamming dreck and going to different worlds, or spheres whatever. Even if you get to where you're going ninety percent of the time, and that's optimistic let me tell you, that means one out of every 10 trips you take you wind up somewhere completely off course. A little off course is fine, space is big and planets are big. But sometimes you end up somewhere you've never even heard of before. A lot of people don't make it back from that.
Dungeons & Dragons 3.5
Heroes united by fate in a previously unknown sphere