SWN:Interplanetary Travel Rules

Interplanetary travel in Elyrion takes place in the Aether, the mysterious dimension that lies like a blanket over the skin of realspace. Using special exotic materials gathered from deep space, it is possible to construct solar sails which harness the arcane radiation of stars and ley-lines to access the Aether, where travel at speeds far in excess of the realspace speed of light is possible.

Ships can enter the Aether when close to a star, or when near the center of a ley-line, by taking advantage of the intense arcane radiations present there. Ships can exit the Aether at any time by bleeding off their aethiric momentum, but may be unable to re-enter the Aether without the use of specially constructed "kick bombs" if they are too far from a star or ley-line.

Making Aether Crossings

Aether travel between star systems requires that they be connected by a ley-line. Many interstellar voyages require multiple jumps. Generally, ships cannot precisely target regions within a system for their arrival, but jump down to realspace in a handful of areas made possible to reliably target by the interaction of the ley-line with the local star. Such arrival areas are often fortified by local authorities, or are prime areas for piracy if unguarded. Intra-system crossings must then be made to reach the ship's region of choice. When changing between ley-lines, ships generally must drop down to realspace to reset their aethiric charge, but such drops are not a significant contributor to travel time. Avoiding common drop-down zones is possible for a skilled navigator.

Aether travel requires time. For interstellar crossings, this is dependent on the available ley-lines. Ley-lines are described by their rank, which is equal to the number of days required to traverse a single hex. The weakest ley-lines tend to be rank-6. while the Novabridge is a rank-1. Some ships optimized for speed of Aether flight can reduce this time by a fraction indicated in the ship's stats. It takes ten minutes for a ship within the habitable zone of a star to make the jump to the Aether, half an hour for ships between the habitable zone and the system's edge, and an hour for ships beyond the star's direct influence.

Aether travel cannot be done within atmospheres, or at an altitude of less than half a radius from the surface of a large astronomical body.

For crossings within star systems, the system is divided up into regions, which represent major points of interest and their moons and satellites. Travel within regions is done using conventional thrusters; see below. Travel between regions takes 1d6 * 12 hours.

Navigators can attempt to "trim the course," reducing travel time by taking advantage of momentary fluctuations in the aethiric currents. If successful, trimming the course allows the navigator to re-roll travel time dice and take the lower number, or increase the effective strength of the ley-line being used by 1.

Once a ship has completed a crossing, it takes time to bleed off its Aethiric charge. Ships generally require 1d4 * 30 minutes in realspace before they can safely initiate another jump. This delay is a significant contributor to intra-system travel times. Attempting to jump to the Aether before fully discharging is possible, but extremely dangerous.

Aether travel requires knowledge of the ley-lines for a crossing to be made safely. A course record, or "rutter" contains information about the structure and flows of the ley-line over its course. The more up-to-date and specific a rutter, the safer the jump. The great majority of inhabited space's ley-lines have been charted in some detail, and such "atlases" provide a degree of guidance on all but the most obscure routes. Generally, more commonly traveled routes have highly granular, recent rutters available freely. For less common routes where the regular plotting is not sponsored by local governments, high-quality rutters may come at a fee, charged either by the operators of measurement ships or the amalgamators who combine measurements from recent crossings into useful dossiers.

Travel between regions in a star system also requires a rutter. Any rutter terminating in the star system will suffice; colonized systems typically contain satellite networks which broadcast up-to-date information about local aethiric conditions.

Attempting a crossing without a rutter is incredibly dangerous, typically only undertaken by those of extraordinary physical knowledge and navigational skill, the suicidally foolish, or those convinced that they are divinely protected (the latter two categories often being difficult to tell apart).

Aether travel also requires a pilot, as no system not in possession of a soul has yet been devised which can effectively react to the unpredictable currents and fluctuations of the Aether. Generally, at least 3 crew members with some knowledge of Aether navigation are required in order to cover all watch periods, although only one real expert is needed. A single pilot can oversee some short crossings with a sufficient supply of stimulants, but doing so carries its own risk.

If everything is in place for a crossing, the navigator makes an Int/Pilot check and the process begins. A single check can be made for an entire journey (if a daring risk is to be taken on a particular leg, that leg can be rolled separately). If the difficulty is less than 6, there is no need to roll. If the roll fails, something has gone wrong during the crossing

Aether Crossings
Base difficulty of a crossing	7
The course is totally uncharted	+6
The rutter is more than 5 years old, or is from an atlas	+2
The rutter is more than a year old	+1
The rutter is less than a year old, but is assembled from individual ship readings	+0
The rutter is less than a year old and is the product of dedicated surveyors	-1
The jump was made before the ship had fully bled off charge	+3
Trimming the course	+2
Avoiding common drop-down zones	+2

3d6	Aether Crossing Mishap
3	Catastrophic energy spike. Ship drops to realspace around a random star of the 3 closest to its destination on the same ley-line (even if the crossing was intra-system). All systems are destroyed.
4-5	Shear surge overwhelms internal systems. Ship drops to realspace near a random star of the 3 closest to its origin. 50% chance for each system to be disabled. If making an intra-system crossing, ship drops to a random region.
6-8	Power spike. One system is disabled until repair can be completed, and an additional piloting check at the same difficulty is made at +2 difficulty. If this check is failed, the ship emerges into realspace a number of stars from its destination along the ley-line (in a random direction) equal to the magnitude of the failure. If making an intra-system crossing, drop to a random region.
9-12	Ship off course. Emerge around a random star between the origin and destination, or on a random star along a branching ley-line (or a random region for intra-system crossings) and try again.
13-16	Ship off course but detected early, make another Pilot check.
16-17	Crossing successful, but takes twice as long.
18	Crossing successful by blind luck

Realspace Crossings and Fuel

Travel within regions can generally be done with conventional thrusters, and takes 1d6 * 6 hours. Travel between points on the surface of a terrestrial planet can be done in 1d4 hours. No piloting check is needed for realspace travel. Ships can burn an additional unit of fuel to "trim the course", making a difficulty 8 piloting check which halves travel time on a success, but has no impact on a failure.

Ships can generally carry 10 units of fuel. Orbital ascent and descent from bodies with substantial gravity require 1 unit of fuel. Crossings within a region use 1 unit of fuel. Engaging in ship combat generally burns one unit of fuel. Fuel generally costs 50 credits per unit.

Hiding, Seeking, Pursuit, and Escape

Stealth is frequently important to adventurers - or at least, frequently more important than staying on good terms with their fellow spacefarers. Hiding and seeking works identically to the base rules. However, locking attempts may be made from anywhere in a star system. It is generally impossible to maintain a lock once a ship makes an Aether jump. Ships entering and leaving the Aether produce bright coronas and and trails of charged particles known as navigation plumes. Nav-plumes make it obvious that a ship has entered or exited a system at a certain location, but do not guarantee a useful lock (although they give a +2 bonus to the observer). Ships can attempt to break these locks by hiding in the shadow of moons or asterioids (generally requiring sublight travel within the region), or by running "cold" in place for 24 hours.

Since ships are functionally untraceable in the Aether, pursuits as described in the base rules operate within, rather than between regions. If a ship can enter the Aether before it is intercepted, the pursuit automatically ends.