Different models for fantasy space travel

After some thought, I decided to put together some ideas for space fantasy campaigns. To that end, I would present several different models for space travel physics as distinct campaign setting cosmologies.

Aristotelia, the setting of celestial spheres

This setting is based on Blood & Treasure, Dark Dungeons, and Voidspanners.

In Aristotelia, the physics of space travel are very different from reality. The night sky is actually the surface of a massive "celestial sphere" that encompasses the solar system. Outside of the sphere is the "luminiferous aether" and access to other celestial spheres in the universe.

Celestial spheres are not all made the same, but may have different local physics. One sphere might be heliocentric while another is geocentric. One sphere might be filled with an airless "void" (astronauts carry their own air supply without needing suits), while another is full of a breathable "ether." One sphere might have its inner and outer planes as inner and outer planets inside the sphere, while another has its inner planes inside the sphere and its outer planes outside the sphere.

Propulsion systems include:

• Sails of Skysailing are a magical effect that allow ships to fly through the air, void, and luminiferous aether. These are made from the silk of phase spiders and may be attached to conventional sailing ships.
• Void engines are magical items that propel vessels through the void. These need to be activated by a power source, such as a wand, a wizard, or a sacrificial victim.
• Ether sails are magical sails that ride the ether winds. These do not need a power source, but they are only effective in ether currents.
• Tree ships are rare vessels created by elfin druids.

Alhazenia, the setting of outer space

This setting is based on all those settings in which astronomy and outer space operates as it does in real life.

In Alhazenia, star systems and outer space functions as it does in reality. This makes it easy for a player familiar with modern astronomy to enter the setting. There are multiple competing methods for space travel, not one universal method used across the universe. These include fantasy magic, science fiction technology, and more based on a variety of different power sources.

Power sources harnessed for applications as propulsion systems include:

• Magic. Wizards can cast spells or create magic items that allow space travel.
• FTL drive. Seen in Dragonstar, Starfinder, and many other settings. These are taken straight out of scifi, so read scifi for details. I dislike this approach as I find it lazy and bland.
• Flux culler. Seen in Aether & Flux: Sailing the Traverse. These non-magical devices generate the electrical force known as "flux," which provides propulsion by interacting repulsively with the "aether" suffusing the universe.
• Aetherdrive. Seen in Aethera Campaign Setting. These are "magic-technology hybrids" powered by "highly toxic crystals" with "naturally telekinetic properties."

Fitting the planes of existence into Alhazenia requires more work. I should save that for a future post.

Celestial spheres cosmology, part 2

I previously mentioned the Aristotelian/Dantean cosmology of celestial spheres. The OD&D game took inspiration from the concept when it developed its Mystaraspace cosmology, which would go on to inform the cosmology of Spelljammer. This cosmology was also adopted (or adapted) by retroclones including Blood & Treasure, Dark Dungeons, and Voidspanners. The specifics and jargon vary between settings, so I'll be using Dark Dungeons as my primary reference here.

The basics

In contrast to the Aristotelian/Dantean cosmology, the celestial spheres are much simplified in this model and take further inspiration from the obsolete scientific theory of ether and modern astronomy; it is unique as far as cosmography models go. The solar system generally behaves much as its does in reality, with the planets orbiting the sun (although some systems may be geocentric or weirder). However, Aristotle's firmament of the fixed stars remains as the sole celestial sphere ("crystal sphere" in D&D jargon). The interplanetary space inside the sphere is an empty "void"; unlike real physics, living creatures have sufficient personal gravity to carry a small supply of air and aren't in any danger of a zero pressure environment. The space and planets within the celestial sphere is mirrored in each of the adjacent inner planes (air, earth, fire, water, ether), which are called "inner planes" because they all exist within the sphere. Outside of the sphere is the luminiferous aether, which is the equivalent of interstellar space. Other celestial spheres containing their own planetary systems exist throughout the luminiferous aether.

Space travel is generally accomplished using spacecraft that are powered by magitech or exploit quirks of the fantasy physics, such as through engines, sails, or other means of propulsion. These vessels are generally modeled after sailing ships, and may even be capable of doubling as sea ships and/or airships.

The OD&D and AD&D games differ greatly when it comes to depicting the outer planes. In the original celestial spheres cosmology, outer planes aka demiplanes were artificial spheres created by the immortals (mortals ascended to divinity) that were anchored to a celestial sphere. In AD&D's Manual of the Planes, the outer planes became independent of the celestial spheres cosmology entirely; when it was retrofitted later as Spelljammer, redundancies were introduced such as the distinction between the "phlogiston" (luminiferous aether) and the deep ethereal plane.

One wonders whether Disney's Treasure Planet was influenced by the game.

Simple variations

Blood & Treasure and Voidspanners put their own spins on this basic model. Both settings are closer to the original Aristotelian Universe in that their universe does not extend beyond the firmament, as opposed to having multiple such spheres emulating real star systems. Both settings diverge when it comes to the nature of the planets, however.

In Voidspanners, the system is heliocentric and the planets may be visited and traded with as per the Dark Dungeons model. Furthermore, the void is full of breathable ether; although prolonged exposure may still be harmful. Overall, the differences from the standard model are minor. As a supplement for Basic Fantasy, no rules for the other planes' geography are included.

In Blood & Treasure, the celestial sphere model is combined with the "orrery" or "solar system" model mentioned in the guides for designing your own planar cosmology. Here the planetary system ("Land of Nod") is geocentric and the transitive, inner and outer planes are presented as concentric spheres and associated planets: the ethereal plane corresponds to the lunar orbit, the astral plane corresponds to the space beyond, the inner planes correspond to the inner planets and the outer planes correspond to the outer planets. Taking a further page from Dante, Hell is located inside the earth and Heaven corresponds to the surface of the firmament.

Since these settings are limited to single systems, it is possible for them to be integrated into the basic model by presenting them simply as quirky spheres floating within the luminiferous aether. IIRC, the D&D canon cosmology uses similar logic to explain the cosmological differences between the different official campaign settings: each celestial sphere may have its own set of planes that aren't necessarily the same as those of other spheres.

On another note, the surface of the celestial sphere is comparable to the outer plane "The Vault of Stars" from 3pp Classic Play: The Book of the Planes. If you want to have adventures on the literal night sky, then I highly recommend using that book (not that I found any alternatives, mind you).

Celestial spheres cosmology

The “celestial spheres” are an outdated model of the solar system dating back to Aristotle.

The Aristotelian universe consisted of the world in the center (composed of the four elements air, earth, fire, and water), the celestial spheres above (composed of the fifth element ether), and the spherical firmament of the fixed stars surrounding all.

A modern interpretation of the Aristotelian Universe, with the earth in the center, the elements above, then the celestial spheres, and finally the firmament.

People actually believed this was how the universe worked. It supplanted earlier models in which the world was flat, the heavens or “firmament” was a literal dome which separated the world from the “waters” of primordial chaos, and the underworld was another dome under the flat Earth which complemented the heavens. (A model I mentioned in past posts. It roughly informs the omniverse and world axis cosmologies.)

This model influenced some retroclone writers. The Pathfinder cosmology (specifically the Golarion campaign setting) based the organization its elemental planes on Aristotle’s. The Blood & Treasure cosmology (specifically the Nod campaign setting) adopts Aristotle’s cosmology wholesale, and combines it with that of Dante’s Inferno too. As I mentioned in a previous post, Nod’s cosmology goes even further and makes each of the planets an outer plane. ADDEDUM 11/21/2019: The Voidspanners setting also uses a variation of the Aristotelian celestial spheres. Unlike Nod, these are mundane planets and not outer planes as planets.

Why is this remotely relevant? It occurred to me that I was going about campaign cosmology all wrong. This should be common sense! There is no reason why the multiverse cannot contain multiple universes with different cosmologies. A flat world, celestial spheres, solar systems, etc.

In future posts I should like to describe a multiverse consisting of multiple universes with different cosmologies.

Planes and planets

Although space travel seems fairly unpopular in OGL fantasy gaming, it has appeared in surprisingly diverse forms.

Portal travel only. By default, most fantasy campaign settings limit themselves to a single planet. If multiple planets are introduced, then they will generally be reachable only through portal or by traveling through one of the transitive planes. (WarCraft is a popular example.) Spacecraft either don't exist or are so rare that the PCs won't be expected to ride inside one. This model seems to be the most common for settings that involve multiple worlds, such as Golarion's Distant Worlds supplement, presumably because space travel occupies a lot more conceptual space.

Science fantasy. When space travel gets involved as a standard fixture of the setting, the most common manifestation is what some label the "science fantasy" subgenre. (Star Wars is a popular example.) What I don't like about this model is that tabletop settings, like Dragonstar, Starfinder, or Starjammer, typically sloppily throw scifi and fantasy conventions into a blender with only the clumsiest attempts to integrate them. Magic and technology exist side-by-side, operating on completely different rules.

Magitech space fantasy. However, some settings don't lazily throw scifi tech into a standard fantasy setting and pretend it works. Instead, they might devise magitech spacecraft to match the fantasy setting. Campaign settings like Shadow of the Spider Moon, Aether & Flux, Aethera, and Necropunk are examples. They rely on technology powered by magic or alternate physical laws, sometimes having multiple competing methods.

Retro space fantasy. The science fantasy and space fantasy subgenres still assume that space operates like it does in reality: explosive decompression, empty vacuum, etc. However, some settings go even further with the fantastical elements, jettisoning real physics entirely. Spelljammer introduces breathing in space, crystal spheres, phlogiston, geocentric systems, and so forth. This model is recycled by some OSR settings like Voidspanners and Dark Dungeons.

Planes as planets. The models I mentioned so far still assume that space travel is limited to the "material plane" (as D&D calls it) and that planar travel operates by an entirely separate subsystem. However, that doesn't have to be the case either. 3pp like Classic Play: The Book of the Planes and Blood & Treasure suggest that the planes could be arranged in the same way as planets and visited through fantastical means of space travel. At this point, there is no distinction between space travel and planar travel.


ADDENDUM 11/19/2019: Honorable mentions to Aetherial Adventures and Cabbages & Kings: The Steampunk Renaissance.