Skytrains

Skytrains are a form of steam-powered locomotive capable of flight and space travel. They are one of the most common forms of interplanetary and intercontinental transport, for both passengers and cargo, across the Geminosan moons and the more general Avalgandir system. Skytrains are generally favored for their conservative usage of fuel, impressive maximum speeds and nearly endless capacity for cargo. Moreover, almost all skytrains are compatible with conventional metal rails, so may be used on the ground as well. However, their lack of maneuverability in comparison to astrawhales or other such transport means they are less well suited to space combat or other more dexterous situations. Moreover, their dependence on prebuilt magical systems makes many models ill-suited to deep space exploration.

## Mechanics

Skytrains require three primary resources to function: air, water and starthread. A small supply of coal is sometimes necessary as well for ignition purposes. This is usually only the case for older or cheaper models of skytrain - more sophisticated designs employ lightning or fire magic for this purpose, which in turn demands a magically attuned crew member.

The train's fuel takes the form of starthread, a thread spun from newborn stars that have been coagulated by solspindels or other void beasts. Spools of starthread are stored in the fuel cart, directly behind the main engine. Starthread is pulled into the engine underneath the boiler, where it is bombarded with heat from previous starthread or ignition, causing the stellar life cycle to occur at a massively accelerated pace. The starthread reaches the phase of red supergiant while still beneath the boiler, heating the water within to steam.

Steam is siphoned into the pistons, powering the wheels of the train. The two front wheels pull the starthread under the train as tracks of light. While under the engine and fuel cart, the starthread enters a supernova phase, expelling light and plasma under the train and behind it. This force on its own is a permissible propulsion of the train, though is inefficient, slow and difficult to control. It is usually only reserved when the skytrain must fly somewhere without rails, such as a new asteroid.

Often, skytrains will ride upon the Dust Rails, a vast network of stardust trails between different celestial bodies created by mages centuries ago. In this situation, the stardust is scooped up by a plow at the train's front and funneled to the stardust rails on either side. The starthread, by its immense heat, reacts and fuses with the stardust. This process results in solid rails suspended on the Dust Rails, allowing for easy exit of atmosphere and long-distance space travel.

The caboose of the train is often equipped with a threadblade or guillotine behind the wheels, to destroy trailing tracks in case they collide with the skytrain on a sharp turn.

### Space Travel

While in space, the skytrain must supply a suitable source of air for its passengers. Skytrains are often equipped with air resevoirs, which are expelled once atmosphere levels become too low. Holding runes on the train's sides keep the air in place, forming a small cloud around the train. For less expensive skytrains, the need for continuous renewal of the runes by a mage means travel far beyond the Geminosan moons without magical aid is impossible.

Gravity is another concern. Cheaper skytrains will not include any source of gravity, while more advanced ones will include gravity spells within the craft. Engineers leaving the train for the more general air cloud outside are able to float with zero gravity, often with the aid of a tether to the train.

Passenger carts are sometimes too far behind the main engine to benefit from the air cloud without severe dissipation. Hence, passenger carts are often airtight. This is uncommon on the main engine or fuel, due to the starthread moving between the two carts and the joint between them. Many skytrain conductors also find maintenance of the skytrain on long journeys demands an ambient atmosphere, though it is a matter of personal preference.

### Landing and Takeoff

Skytrains land in three possible ways: tracked, trackless or static. In tracked landings, the skytrain will slowly descend upon a metal railway on the ground, dissipating its starthread gradually until it is entirely based on earth. Starthread is rerouted into the chimney - by this time, it has been cooled enough so not to enter a supernova phase. Tracked landings are safer in the certainty of the landing surface and quicker, but more difficult to ensure the starthread is removed in time to not heat the tracks. Landing tracks are thus often damaged from faulty landing attempts and must be repaired constantly. Hence, designated landing tracks are few in number.

Untracked landings involve flying close to the surface of a planet while still using starthread tracks. The stardust combines with the earth, forming ad hoc tracks that the train may use to travel on the ground for a few minutes. The intent is to then navigate onto prebuilt tracks in this manner. Prebuilt tracks are rarely damaged by this method - the generated tracks will overlap old tracks, but are cooled by the earth, meaning the existing rails are not heated by enough to warp the material. Moreover, the ad hoc tracks are weak and soon crumble away. Hence, untracked landings are possible almost anywhere.

Static landings involve expelling excess starthread in front of the train to slow it down to a midair standstill. The train then lowers its power output gradually, sinking straight down towards the earth. This method is most suitable for landing where tracks are nowhere nearby. The temporary tracks generated beneath the train on landing will not be suitably strong to keep traveling on the earth, so a static lift is then necessary afterwards.

Takeoff is accomplished either statically or dynamically. Static takeoffs are the reverse of static landings. These are unsuitable for metal tracks, as they may warp the metal with immense heat; they are commonly used only after a static landing or an untracked landing that has not resulted in reaching metal rails. When on metal rails, a dynamic landing is preferred, where starthread is gradually introduced under the train during travel until liftoff is achieved.

### Magical Concerns

A great deal of the technology powering skytrains is based on magic: beyond fuel, gravity and air control, skytrains also magically extend the interiors of their fuel carts and boilers to be many times larger on the inside. This means repeated check-ups by suitably skilled mages are a necessity for many skytrains to function, should a powerful mage not be a member of their crew. Magical fluctuations are also a great danger for skytrains; the starthread, atmosphere runes and many other technologies are often put at risk, so the demand for less magically dependent models is great among parties interested in deep space exploration.

Magic also poses a serious risk of bringing the attention of gods. Skytrains have become a common target for god attacks in the last 200 years. It is imperative that the magic employed is as non-divine as possible, towards which a great deal of research has been dedicated. Skytrains will also often employ concealment magics while entering the atmosphere of a planet, such as expelling clouds of scatterlight. To conserve on these rare substances, skytrains will often only engage their cloaking near the stratosphere, creating many of the shooting stars one sees in the night skies of Lorvathia and other moons.