tips, notes, refs, charts
the astral sea has gravity and breathable air.
wildspace does not.
ship-roles
In any location where gravity isn't present, the following rules apply:
Impeded Melee. When making a melee attack with a weapon, a creature that doesn't have a flying or swimming speed (either naturally or provided by magic) has disadvantage on the attack roll unless the weapon deals piercing damage.
Movement. A creature can use an action to push off something heavier than itself and move up to its walking, flying, or swimming speed in a straight line. The creature continues along this course, moving in a straight line at its speed on each of its turns until something stops it or changes its trajectory.
When a spelljamming ship moves in space, creatures and objects in its air envelope move with it, pulled along with the ship because of the strength of its gravity plane.
However, an unanchored creature or object floating in a ship's air envelope is weightless and drifts toward the edge of the air envelope at a speed of 10 feet per minute. For example, an unconscious sailor or a crate that falls off the deck of a spelljamming ship would begin drifting away from the ship along its gravity plane toward the edge of the ship's air envelope. When it exits the air envelope, the sailor or the crate would be left behind as the ship moves away from it.
The air envelope around a body or ship can be fresh, foul, or deadly. Air can change from one quality to another over time.
Fresh air is completely breathable. Under normal circumstances, the air envelope of a ship remains fresh for 120 days. If a ship carries more creatures than its normal crew complement, they exhaust the supply of fresh air more quickly.
Foul air is stale and partially depleted. It is humid and smells bad. Any creature that breathes foul air becomes poisoned until it breathes fresh air again. The air aboard a ship with a normal crew complement degrades from fresh to foul on day 121, and the foul air turns deadly 120 days later.
Deadly air is unbreathable. Any creature that tries to breathe deadly air begins to suffocate (see the rules on suffocation in the Player’s Handbook).