This post has been updated to correct another math error. That’s becoming a habit
Welcome back to my Spelljammer conversion for 5e. This post will cover a few more items related to ship movement that I missed in the first movement post. I may have underestimated just how much ship movement is a part of this campaign setting. However, traveling through space is what Spelljammer is all about so it all needs to be addressed.
There were actually two types of travel in the original Spelljammer rules; tactical and long-range travel. The SR rules that I converted in the first post apply to tactical movement and travel within the atmosphere of a celestial body. There is an entirely different matter of taking off or landing on a planet. There were ten different classes of planet in Spelljammer each distinguished by their diameter.
Ships taking off or landing on these different size planets were assumed to be moving away from or towards the surface in a straight line. The time taken to land or take off did not take into account the SR of the ship. Instead it was determined based off the size class of the planet. For example, it took a spelljammer ship 40 minutes to take off from a Size E planet which is roughly Earth-sized.
I think it is actually simpler to set an atmosphere limit above a planet that must be broken through in order to reach Wildspace. I’m going to just make up a multiplier of 10 times planet diameter here based on 62 miles (100 km) being the widely held beginning of space on Earth. This isn’t right. The distance to space is about 1/100th the diameter of Earth. I’m going to use 1/10th the diameter for this conversion. This change has been made in the rules below.
The DM can figure out from the table below how long it takes a ship to reach Wildspace based on their SR.
Ships that are traveling in Wildspace have broken free of the gravitational pull of these bodies and are able to obtain greater speed. A spelljammer ship traveling in a straight line and avoiding any gravity fields will reach a speed of 4 million miles per hour (6437376 km/h) regardless of SR rating.
This should mean that a spelljammer ship can travel 100 million miles (160934400 km) through Wildspace in a single day of travel, but of course it’s not that simple. The original rules allowed for an individual to operate a helm for 12 hours without tiring. After 12 hours the operator may continue to use the helm, but with an SR decrease of 1 per hour. After 24 hours of use the operator passes out and must be fully rested before using the helm again. I think this is a good area to bring in the exhaustion rule from 5e.
The travel speed of a spelljammer ship changes based on where the ship is being operated. The SR granted by the spelljammer helm and operator applies when a ship is being operated in the atmosphere of a celestial body or when the ship is engaged in combat. The boundary between planetary atmosphere and Wildspace varies between different planets, but generally rests at a distance of 1/10th of the diameter of the world.
Celestial Body Size Classification
|Size Class||Diameter in Miles||Diameter in Kilometers|
|Size A||Less than 10||Less than 16|
|Size J||10000001 and greater||16093441 and greater|
Distance To Reach Wildspace
Size Class Miles Above Surface Kilometers Above Surface
A 1 1.6
B 10 16.1
C 100 161
D 400 644
E 1000 1609
F 4000 6437
G 10000 16093
H 100000 160934
I 1000000 1609344
J 10000000 16093440
A spelljammer ship in Wildspace or the Phlogiston is not restricted by its SR. A ship traveling through Wildspace and avoiding any gravity fields will reach a speed of 4 million miles per hour (6437376 km/h) regardless of SR rating. The Phlogiston contains dense rivers of flammable ether that flow between Crystal Shells. Ships traveling in these currents can achieve speeds that are beyond measure. Generally a ship may travel between crystal spheres within 10d10 days.
However, travel is always limited by the endurance of the helm operator. A spellcaster may operate a spelljammer helm continuously for 12 hours without tiring. At the end of each hour thereafter the character must make a Constitution saving throw. The DC is 10 + 1 for each hour past 12 hours. On a failed saving throw, a character suffers one level of exhaustion (see appendix A in the PHB). Each exhaustion level gained from spelljamming reduce maximum SR by 1. This penalty persists until removed by an appropriate amount of rest. Regardless of exhaustion level after 24 hours of continuous operation of a spelljammer helm the operator will pass out and be unable to use any helm again until after a long rest.
We aren’t quite done with movement yet. For the next post I will begin to convert over rules for ship to ship combat with Maneuverability Class. I have a small admin note as well for those of you that read all the way to the end. I will adding all of the bold texted items in these posts to a separate Spelljammer page on the blog. This will be a living document while I do the conversion and most likely all the way my group’s Spelljammer campaign.