Spelljammer
Spelljammer
Traveling between planets and shipboard adventures is a critical part of the campaign. As such, I'm going to be very careful in designing the spelljamming science of this universe. There will be a mix of the article, the original spelljammer rules, and some home made stuff.
Planetary Distances
Rather than making travel times between planets a random number, I'm going to try using geometry. For starters, I will call the distance that a spelljamming vessel with a minor helm can travel in one day a SJU (Spell Jamming Unit). That should be about 10 million miles. I will also say that planets all travel in their orbits at roughly the same speed. The distances of each planet from the Pyre (and thus the radius of it's orbit) are as follows:
•Ashen: 4 SJU
•Verdura: 8 SJU
•Quelya: 12 SJU
•Perianth: 16 SJU
•Chain of Tears: 32 SJU
•Moradin's Forge: 48 SJU
Also, the distance between Perianth and the Spider Moon is about 250,000 miles, so at spelljamming speed it takes about 36 minutes to traverse the distance.
The length of a year on Quelya is 375 days. The circumference of its orbit is approximately 75 SJU. So the speed at which planets travel is approximately 1/5 of an SJU per day. Using that as a base, the lengths of a year on the other planets are as follows:
•Ashen: 125 days
•Verdura: 250 days
•Quelya: 375 days
•Perianth: 500 days
•Chain of Tears: 1000 days
•Moradin's Forge: 1500 days
I have created a spreadsheet to determine distances between planets on any day, given a day somewhere in the past when they were all in line with each other. Because of the convenient numbers I have used, there is a planetary alignment every 3000 days, which is every 8 Quelya years.
Helms & Movement
While most races possess magic that can make a ship fly, it requires a helm to make it fly at spelljamming speeds. Only the elves have the knowledge of how to create a helm, and among the elves, only a few of the great houses have the secret. They have a near monopoly on the market.
Helms come in 2 types, minor and major. I am making a small change to the way that helm type relates to speed. As noted in the article, ships move at tactical speed when they are within the gravitational influence of another mass, and at cruising speed when they are not. The article has ship size influencing tactical speed, but not cruising speed. I'm going to have it effect both. For ships of size colossal and larger, a major helm is required and the ship cruises at 1 SJU per day. For smaller ships, a minor helm may be used to attain the same speed, but a major helm will allow it to travel twice as fast.
Tactical speeds will be done similar to the way they are in the article. The values below are the speeds from the article, showing the number of feet a ship travels with a single move action, and a ship being able to make 2 move actions in a round. I am working up my own system for ship combat, so these numbers are likely to change.
•Large or smaller
•Minor Helm: 120 feet
•Major Helm: 180 feet
•Huge
•Minor Helm: 60 feet
•Major Helm: 120 feet
•Gargantuan
•Minor Helm: 30 feet
•Major Helm: 90 feet
•Colossal
•Major Helm: 60 feet
•Awesome
•Major Helm: 30 feet
A spelljammer helm is operated by someone able to cast arcane spells. This character must also have the pilot skill in order to steer the ship. The character must expend 1 spell point for each 8 hours of operation. For a major helm, the cost is triple in order to use it at its greater capabilities.
Gravity
Most of what is written in the article about gravity is fine, but the rules on when a ship can move at cruising speed and when it must drop to tactical due to gravitational influences are not to my liking. According to them, if a colossal ship was sitting right next to a huge ship, the huge ship would have to remain at tactical speed, but the colossal ship could just zip away at cruising speed. I don't like that.
In the original game, any object of 10 SJ tons or more within 12,500 feet was enough to drop any ship out of cruising speed. Anything smaller within that would be picked up my the ship's gravity plane until it drifted back out of the area.
Here's how it works in my game: Every object has a natural gravity value and range of influence based on its size. This is shown in the following list:
•Large or smaller
•Natural Gravity: 0
•Range of Influence: 500 feet
•Huge
•Natural Gravity: 1
•Range of Influence: 1,000 feet
•Gargantuan
•Natural Gravity: 2
•Range of Influence: 2,000 feet
•Colossal
•Natural Gravity: 4
•Range of Influence: 4,000 feet
•Awesome
•Natural Gravity: 8
•Range of Influence: 8,000 feet
•Planetary body
•Natural Gravity: 32
•Range of Influence: 32,000 feet (~6 miles)
When two cruising ships meet (or one cruising ship and a non-cruising ship or object), they both drop to tactical speed at a distance equal to the larger ship's range of influence. Objects with no natural gravity rating do not cause ships to drop to tactical speed when encountered. Instead, the smaller object is carried along until it passes out of the range.
Air
This works the same way that it does in the article, except that entering a planetary atmosphere will refresh the air supply of a ship in a number of rounds equal to its gravity rating. There are also some missing details.
The air envelope carried by a ship extends out to the distance of its range of gravitational influence. A creature too small to have a gravity rating carries a very small air envelope with them. The air becomes stale after 20 minutes and foul after 1 hour.
Spelljamming