Air and Gravity

Breathing in Space

As a character ascends a mountain, the air becomes thinner and thinner, until finally it becomes the unbreathable vacuum of wildspace.

Fortunately, all bodies take an envelope of air with them, and this provides some breathable atmosphere. Unfortunately, this envelope is rarely large enough to support life for very long.

A single, human-sized body drags along with it enough air to last 2-20 rounds. If that human-sized body is standing on a rock 100 cubic yards in size (roughly 40 feet in diameter). It may have enough air to survive for several months.

Larger-than-man-sze creatures (ogres and giants, for example) drag along enough air to last twice as long, 4-40 rounds.

Larger objects, such as ships, are rated for their tonnage. Each ton represents 100 cubic yards of space, which brings along enough air to support one human-size crew member for four to eight months. A 30 ton frigate, therefore could support 30 crew members for four to eight months under normal circumstances, and double that under reduced circumstances. The minimum size for a usable ship in space is 1 ton (100 cubic yards). The limitations on moving a ship through space determines the upper limit of ship size.

Air Quality

The air envelope around a body or ship can be one of three classes or qualities-fresh, fouled, or deadly. Air can change from one quality to another over time.

Fresh Air is completely breathable. The air around an individual body remains fresh for 2-20 rounds. Air around a larger body (one ton or more) remains fresh for four months if the vessel carries a normal crew.

Fouled Air is stale and partially depleted. It is humid and smells bad. Air becomes fouled after the first 2-20 rounds around a single body and remains fouled until the 30th turn. The air around a ship is fouled from the beginning of the fifth month until the end of the eighth month. All attack rolls and ability checks made by characters or creatures that must breathe air have a -2 penalty if the air is fouled.

Deadly Air is completely depleted and filled with carbon dioxide. It cannot support life. The air around an individual becomes deadly at the beginning of the 31rst turn, that around a ship becomes deadly at the beginning of the ninth month in space. Anyone trapped inside a deadly atmosphere must make a endurance check each round. Failure means the character passes out. A second failure brings death. Only fresh (or fouled) air can revive the character after he passes out.

Most trips aboard ship take less than four months to complete, or at least present the opportunity to replenish and refresh the air supply within four months. Air usually is not a problem except in extreme cases and emergencies.

Changes aboard ship can affect how long the remaining air will last, adding and losing people onto the ship will decrease the amount of time it takes to degrade or increase it, respectively.

When two bodies meet in space, their atmosphere is exchanged. The class of the air in the smaller body becomes that of the larger body. If the smaller body is at least two thirds the size of the larger, both get one half as much air as the larger had remaining. If the smaller is less than two thirds the size of the larger, both get the larger’s full supply of air, minus one week.

The same thing applies to two individuals exchanging atmosphere. An individual has no effect on a ship’s atmosphere, however, unless the individual is at least huge.

A number of creatures can survive in space without air (undead or magical creatures such as golems, for example). They are unaffected by the status of the air envelopes around them. Certain spells and magical items provide additional protection to the star traveler who may find himself in deep space without a ship.

Classes of atmosphere operate in the same manner in the phlogiston as they do in wildspace. However, when the atmosphere goes deadly, a special property to the phlogiston takes over. Instead of dying the individual lapses into suspended animation until the atmosphere around him is recharged. Living flesh turns gray and stonelike and remains that way until the individual is rescued. By following along the flow, a ship or individual will eventually drift near a sphere, where recovery is at least possible. Note that rescue is not necessarily by someone with good intentions.

Crystal shells usually have no atmosphere of their own, either inside or outside. There are many asteroids and planets that lack atmosphere as well, in contradiction of normal physical laws.


The reason everything drags its own atmosphere around through space is gravity. This is also the reason why people can stand on a space sailing ship without falling off its deck and can stand on a spherical planet without falling off the bottom side.

Every body in space has its own gravity. Gravity is an accommodating force in that its direction seems to be “that which is most convenient.” In an object the size of a planet, gravity is directed toward a point at the center of the planet so that people can stand anywhere on the surface and dropped objects fall perpendicular to the surface. In smaller objects, like space craft, gravity is not a central point but rather a plane which cuts horizontally through the object

Significantly, this gravity plane is two-directional; it attracts from both top and bottom. A sailor can actually stand on the bottom of the ship’s hull and move around as easily as if he was walking on deck. In this case, “down” is actually “up,” back toward the plane of gravity that cuts through the ship.

One of the stranger side effects of all this is that an object falling off the side of a spelljammer can oscillate back and forth across the plane of gravity, falling first in one direction until it crosses the plane, then reversing direction and falling back across the plane again, and so on until something causes it to stop. To a person standing on the deck, the object appears to fall down, then up, then down, then up. This trick is commonly used to amuse passengers new to space travel More than one groundling has gotten in trouble for standing at the ship’s rail and tossing an endless stream of apples overboard just to watch them bob.

An example of this is on a viking longboat cruising through the fjords, suddenly thrown from its home into wildspace. Its crew can still stand normally on its deck. Down for them is toward the bottom of the boat. Similarly, an individual could stand on the bottom of the longship, and find that “down” for him was back toward the top of the boat. Someone who jumps off the deck of the boat would fall downward and pass through the boat’s plane of gravity, whereupon the direction of gravity would reverse for him and pull him back toward the underside of the hull.

A carefully-thrown object can actually go into orbit around the ship. Such orbits do not last long; the object quickly collides with the ship’s rigging or oars, or slows down in the air envelope and crashes into the ship. One of the favorite pranks of experienced spellsailors is to toss an apple or similar light object off one side of a ship in such a way that it curves aroun dand strikes someone standing at the other rail.

Air and Gravity

The Rock of Bral, Part Duex Arrixxia