As a tabletop RPG player, I have always had ideas on new settings for games. I shy away from established settings because I don’t feel I can give any game set within justice, as I would need to know too many details. As a side-realization, this is probbly why fandoms come and go for me, as once a universe becomes too big to keep up with, I tend to lose interest.
Back to the original point, in college I had developed a number of different D&D settings. The first followed the release of Monster Manual II (v.3.0) and was named Urd. As with most of my settings, I based it around an idea instead of a story – the idea being a diverse world with many different playable creature types, including monsters. As certain other books were released (going into v.3.5), I developed more setting ideas, typically based on climates/conditions. Agea was a mostly-ocean world with merfolk and fish-people, another concept took Agea even further with a world similar to the Saturnian moon Europa, and the last was a colder temperate world named Ereth.
Ereth used the Frostburn environmental supplement book. The world was cold, with a temperate equator, and it had a special three-moon system. From the view of an observer on the surface, the largest moon (Tur) travelled east to west, meeting the sun every 41 days. The medium moon (Gi) had a north-south apparent movement, meeting the sun every 10.25 days. The last and smallest moon (Hön) used to be overhead 6000 years ago, but had now moved to meet the rising sun at dawn. It was a silly concept, but a player in the game I was to run for this posed a simple question. As his character was a shifter (a lycanthropic species from Eberron), he wanted to know when, if ever, the three moons met.
As an engineer, I wanted to give as realistic an answer as possible, so I began to do simple math to figure it out. Using trigonometry, algebra, and more all based on the visual cues, I tried to determine orbital distances, sizes of the moons, and periods. Not knowing much about astronomical mathematics, it was beyond my capabilities at the time. I would later return to the conundrum when I decided to use the setting again for another group. This time it had some more significance, as I had decided the game was to loosely include the Dragonstar setting from Fantasy Flight Games. However, I never got so far as to make use of the information – not that I had yet determined it.
At one point, I had thought to use Universe Sandbox, as it is an interesting n-body physics simulator. However, even trying to set up legitimate systems, I couldn’t quite get it right. Upon reflection, it is likely that there are too many required variables that need to be known in order to properly set up a system.
Recently, I was playing around with KSP and had thought to perhaps start to make planets using the Kopernicus mod. After reading through a basic tutorial and contemplating how I wanted to employ it, I began to research the different aspects of the planetary bodies within the game. I specifically was interested in the determination of the Sphere of Influence statistic. Eventually, I remembered Ereth and started to work on creating Hön.
I had started by attempting to determine the synodic period of the moon, but found this difficult, even following refinement of the synodic calculation. I then realized the stationary orbit was closer to what I was looking for, as Hön was basically stationary overhead. After adjusting its semi-major axis to this value, it still wanted to drift westward. I tried reusing the synodic equations to further refine the values, subtracting 1/24000 of the planetary orbital period to recalculate the moon’s orbital radius, but to no avail. After a slew of trial and error, I had finally figured out the exact semi-major axis required to very slowly move Hön west to east across the sky.
It was a fun experiment and I look forward to refining it further to meet the requirements of the system, including Tur and Gi. At present, adjusting the radii and masses of the moons to bring the desired effect is required. If I get extra ambitious, I might look at developing this testing bed into a full-blown mod for KSP.
Vernendale Ventures 