Can a Spelljammer ship fly to one of the Outer Planes?

Question

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.

Answer 1

Yes, Spelljammer ships can fly to Outer Planes

DMG p.47 indicates that you can use color pools in the Astral Plane to travel to an Outer Plane (a term which was used interchangeably with "Astral Dominion" in D&D4e, but not in 5e Spelljammer*). In the case of Hades, a Rust color pool would be used.

Arguably, you would need a color pool large enough to sail through, but (for historical context, if desired) this was common in 4e, where the designers actually wanted 'Spelljammer' ships to sail around the 'Astral Sea' and into color pools.

Also DMG p.58 says:

Most portals from elsewhere reach the first layer of a multilayered plane. This layer is variously depicted as the top or bottom layer, depending on the plane. As the arrival point for most visitors, the first layer functions like a city gate for that plane.

Presumably you could go back out through the same portal (similar to Gate) but that's possibly up to the ruler of the plane or your DM.

*5e Spelljammer now describes Astral Dominions as "Floating" Islands" that "are part of the Astral Sea". For my own 5e Spelljammer campaigns, I'm placing large color pools inside these Astral Dominions.