In 5e, are the Outer Planes accessible via the Astral Sea - particularly by use of a Spelljamming Ship?
Navigating the Astral Sea, a Spelljamming vessel - according to Spelljammer: Adventures in Space - can travel to one of the Astral Dominions, which I've seen described as being similar to the Outer Planes (I haven't been able to re-find the source of this, but since I can't I'm not fixing my opinions on this).
To give a particular example, if a group of adventurers aboard a Spelljamming Ship wanted to fly to Hades via the Astral Sea, would it be possible to navigate there? Once there, would they be able to leave in a similar manner - flying into the sky until they reached the Astral Sea again?
Finally, in the event that they could in fact fly to an Outer Plane, such as Hades, would there be any limitations as to which Level of the Plane they arrvived at?
Since these Outer Planes are portrayed as infinite within their own plane, I'm leaning towards this not being possible. However, I'd greatly appreciate the thoughts of those more knowledgeable on this topic.