Tag Archives: FTL

Void Jumping, Acceleration, and Other FTL Nuggets

This post is going to get a little bit math heavy toward the middle. Just warning you now.

The idea for this post stemmed from a recent discussion on the Star Frontiers: Alive and Well Facebook group talking about the accelerations involved in faster than light (FTL) travel in that game. I’ve written about this many times over the years on forum posts but since I can’t seem to find those posts (I think some of them at least are on the now defunct forums at starfrontiers.org), I’m going to do it one more time here on this blog as a permanent reference. But before I dig into the details of the math and physics, I’m going to share some links to other posts I’ve made that I do still have.

Other Posts

First up we have a post from 2010 on Void Jumping on my Star Frontiers Network site. I don’t think this article is linked from anywhere anymore so this will help to bring it back to life. This essay talks about some of the issues associated with making a Star Frontiers style void jump for FTL travel. This essay was the basis for the sci-fi novel, Discovery, that I published back in 2011 (has it really been that long!).

Next, in 2015, when I was still writing on the Arcane Game Lore blog, I did a series of posts on Void travel that expanded and refined those ideas a little more in the direction of a personal sci-fi game I work on off and on. The first two of these posts were actually part of the November 2015 RPG Blog carnival.

  • The first is an article on Void Travel Sickness. Not really relevant to this discussion but fun none-the-less and falls under the “nuggets” heading.
  • The second, Your Final Destination – Exiting a Void Jump, talks about variations in your arrival at your destination. The blog carnival topic that month was “Surprises” and both of these articles were things that could add surprises or randomness to your FTL travel. I actually recommend you read this one after the next one as it talks about things at the end of the journey but it can be read first.
  • The third (and final) article in that set was part of my “Designing out Loud” series of articles where I talked about game design decisions and ideas. This one was entitled “Designing Out Loud – Void Jumping” and expanded on the ideas in my 2010 article.

While you don’t necessarily need to read those article to follow along with the following, it definitely wouldn’t hurt.

Void Jumping

The concept of the Void Jump was introduced with the Knight Hawks supplement in Star Frontiers. In the original rules (renamed to Alpha Dawn when the Knight Hawks rules came out), there were no spaceship rules and it just said to treat interstellar travel at the rate of 1 light year per day.

So how does it work? According to the rules, you make a jump by leaving your starting point and accelerating until you reach 1% the speed of light. At that point you “jump” into the Void. To get out of the Void, you just have to slow down slightly. While you’re in the Void, you travel amazingly fast, on the order of 1 light year per second (The rules don’t actually so but imply something close to that so that’s the value I use). Once you jump into your destination system, you swing the ship around and start decelerating. Remember, there is no artificial gravity in Star Frontiers so this acceleration and deceleration is what provides gravity in the ships. Most ships make these trips accelerating at 1g.

So how long does this take? For these calculations, we’ll take 1 g to be equal to 10 meters per second squared (m/s/s) of acceleration. On Earth we define 1 g to be 9.82 m/s/s but rounding up to 10 just makes everything easier and its less than a 2% difference.

Okay, here comes the math.

If you start at rest, your velocity at any given time is just:

v(t) = at

where v is velocity (in m/s), a is acceleration (in m/s/s), and t is time (in seconds). Technically v and a are vectors but we’ll just worry about speed, not direction.

Now, the void jump occurs at 1% the speed of light. We’ll take the speed of light to be 300,000,000 m/s. It’s really 299,792,458 m/s but we’ll again round up to make the math easier. The difference is less than 0.07%. Good enough for this discussion. 1% of that is just 3,000,000 m/s. That’s our target velocity.

Since our acceleration is 10 m/s/s, dividing 3,000,000 m/s by 10 m/s/s gives us 300,000 s of acceleration needed to reach jump speed. That works out to 83 hours and 20 minutes of acceleration. Given that a standard day in Star Frontiers is 20 hours long, that is 4.17 days.

That’s the time to get up to jump speed. It takes that much time to slow down on the other side as well. Which means at a minimum, an interstellar jump takes 8 and 1/3 days, assuming everything lines up perfectly (see the Exiting the Void Jump article for things that might lengthen that).

That’s the time required. What about distances covered? The equation for position is just the integral of the velocity equation above. Again, for starting at rest, and assuming that you measure the distance from your starting point, your position at any given time is given by:

x(t) = \frac{1}{2}at^2

where x is your position in meters. We know what t is from the velocity equation above is 300,000 s. a is just 10 m/s/s. Plugging these in gives us a distance traveled of 450 billion meters or 450 million kilometers. (A lot of people forget that factor of a half and end up with the wrong number.) Now the distance from the Earth to the Sun, called an Astronomical Unit (AU), is 150 million kilometers (again I’m rounding, the actual value is 149,597,871 km so the rounding is less than 0.3%).

So in those 4.17 days of acceleration, you traveled 3 AU. If you started at Earth and headed straight out from the sun, you’d be 4 AU from the Sun. That’s most of the way from Earth’s orbit to Jupiter’s orbit (at a distance of 5.2 AU from the Sun). That distance puts you well beyond the main asteroid belt which ends at 3.3 AU.

Now, these numbers all change if you use a different acceleration. Doing those calculations is left as an exercise for the reader.

ADF and the Board Game Rules

The above all works just fine. The problem comes when you start looking at the rules for the spaceship combat board game and try to rationalize those rules with the math above.

From the board game, we have that one hex is 10,000 km and one turn in the game is 10 minutes of time. Added to that is the ship’s statistic, the Acceleration/Deceleration Factor (ADF) which is described as the number of hexes that a ship can speed up or slow down in a given turn. The fastest ships (fighters and assault scouts) have and ADF of 5.

Let’s look at some numbers. First, what is Void jump speed on the game map. Well, jump speed is 3,000,000 m/s or 3,000 km/s. Since a turn is 10 minutes or 600 seconds, that works out to 1,800,000 km/turn. Given that a hex is 10,000 km across, that works out to a speed of 180 hexes per turn. Since the game map is only 54 hexes wide, you’ll never get to that speed in the game.

The problem comes when people start looking at ADF as acceleration in gees, i.e. that 1 ADF = 1g of acceleration. If you make that assumption, then accelerating at 1 ADF per turn, it would take you 180 turns to get to jump speed from rest. 180 turns at 10 minutes per turn means that it would take just 1,800 minutes, or 30 hours, significantly faster than the 83.33 hours calculated above. Obviously 1 ADF cannot equal 1 g.

So let’s work that out. 1 ADF represents a change of velocity of 10,000 km per 10 minutes in 10 minutes (or 100 km/min/min). That’s an acceleration, just not in the normal units of m/s/s. So lets convert them:

\frac{10,000 km}{10 min * 10 min} = \frac{100 km}{min^2} = \frac{100,000 m}{60 s * 60 s} = 27.778 \frac{m}{s^2} = 2.78 g

So we see that 1 ADF is really 2.78 g of acceleration. You’re not going to sustain that for 30 hours and have anyone in any sort of condition to function unless severe precautions are taken. Heck, even sustaining that for 1 turn (10 minutes) is going to be rough. It’s doable, that amount of acceleration and duration is roughly equivalent of a launch to low Earth orbit with modern rockets, but you wouldn’t want to keep it up for a long time.

That also raises another issue. 5 ADF is actually 13.89 g of acceleration. And Star Frontiers doesn’t have any sort of artificial gravity tech. Pulling those kind of maneuvers is a little unrealistic. (There are discussions about using interia screen tech to help with this but that’s a different article.)

There are a couple of solutions to this. One, which is the one I use and which is probably the simplest, is a willing suspension of disbelief. The board game rules are just that, rules for a board game that simulates (sort of) spaceship combat. There are other issues with the board game physics besides this one, so I don’t expect it to represent “reality”. It’s a fun way to approximately simulate spaceship combat.

Another option, which immediately removes the 1 ADF not equaling 1 g issues, is to change the size of the hexes in the board game. Simply saying that they are 3,600 km in size instead of 10,000 km, makes 1 ADF = 1 g. If you keep the range of weapons the same (measured in hexes as they are described in the game rules, the only thing that really changes is that any planet counters you put on the map have to take up 7 hexes instead of just 1. And it might tweak the gravity rules a bit, but not significantly. This doesn’t solve some of the other problems, however. That’s a whole different post as well.

How I Apply This In Game

So how do I use this?

Basic Application

For most ships, I assume that they have two astrogators that can work in alternating shifts around the clock to do jump calculations. Since the rules say it takes 10 hours of calculation per light year traveled. And since it takes over 80 hours of travel time to get to jump speed. This means that any jump of 8 light years or less takes the same amount of time, namely 8.5 days, which I typically round up to 9 for maneuvering around the station and slight variations in arrival location (see my linked posts). And actually, since I round this up to 9 days, it play it that jumps of 9 light years or less all take 9 days, regardless of distance. Each light year beyond 9 adds a half of day of travel time to allow for the calculations. This is how I calculate the travel times for ships in my Detailed Frontier Timeline.

Again that assumes that they have two astrogators. If not, jumps take significantly longer, namely one day per light year traveled, plus 4.5 days to slow down at the destination, with a minimum of 9 days total travel. So in this case, jumps of five light years or less take 9 days, and each additionally light year adds a day on to the jump time.

Now I do allow the jump calculations to be started before the ship leaves it’s berth, assuming the crew knows when they plan to leave (to within a day or so). But because the planets and stars are always in motion, and the jump calculations have to be done for each specific jump, no more than half the calculations can be done in advance. The rest must be done “in flight.” For me this represents the tweaking and refining of the ship’s course in preparing for the jump that I discuss in the other articles I linked. But that means that even for a ship with a single astrogator, they can reduce the flight time if the astrogator gets started before they leave on the longer jumps.

Traversing multiple systems in a single trip

Another aspect of this is what I like to call the “high speed transit.” This occurs when the ship wants to traverse several star systems but doesn’t need to stop in each one. In this case, the first jump starts as usual, but once they traverse the Void the first time things change.

In each system after the first, until they reach the final system that they want to stop in, they don’t decelerate, at least not appreciably. But rather remain near jump speed, either drifting or, if they want gravity, decelerating for a few hours, flipping around and accelerating, and repeating until they are ready to jump. During this time the astrogators work on the jump and the engineers do any needed engine overhauls. The amount of time spent in system is just the longest of those two activities. Once that’s done, they nudge into the next system and repeat until they arrive at the destination system where it then takes 4.5 days to slow down.

Let’s look at an example: The UPFS Stiletto, an assault scout, is on patrol in Truane’s Star and has orders to get to Dramune as quickly as possible. This route has 4 jumps:

  • Truane’s Star to Dixon’s Star – 5 light years
  • Dixon’s Star to Prenglar – 5 light years
  • Prenglar to Cassidine – 7 light years
  • Cassidine to Dramune – 4 light years

Using normal jumps, these are all less than 9 light years so each jump would take 9 days for a total of 36 days.

Rather than do this, let’s look at what this takes using the high speed transit option. According to the rules, engine overhauls take 60 hours minus 1d10 hours for each engineer level. The rules also say that Spacefleet ships typically have level 4 engineers. That means that on average, it will take 38 hours to overhaul each engine. We’ll assume that there are 2 astrogators and 2 engineers onboard the Stiletto. This is what a high speed transit looks like in this scenario:

  • Accelerate out from Truane’s Star – 4.5 days – plenty of time to do the 50 hours astrogation calculations
  • Transit Dixon’s Star – astrogation calculations take 50 hours (2.5 days of round-the-clock work), engine overhauls only take 38 hours of work, but since there is only one engineer per engine, they have to sleep. So these are the slow part, taking 4 days – so after 4 days, they jump to Prenglar
  • Transit Prenglar – astrogation will take 70 hours (3.5 days of round-the-clock work). This one is closer but the 4 days of engine overhauls is still the limiting factor. After 4 days they jump to Cassidine.
  • Transit Cassidine – Here the astrogation calculations only take 40 hours (2 days of round-the-clock work) and the astrogators get a bit of a break while the engineers finish up. After 4 days, they make the jump to Dramune
  • Decelerate in Dramune – it takes 4.5 days to slow down and arrive at Inner Reach.

All told, this trip takes only 21 days instead of the baseline 36, saving 15 days of travel. The crew might be a little tired, but they made it without taking any risks.

If you only had 1 astrogator and two engineers, one level 3 and one level 2 (more likely on a merchant ship or PC ship), the transit looks like this:

  • Accelerate from Truane’s Star – 4.5 days, same as before. We assume the astrogator got started before they left.
  • Transit Dixon’s Star – Astrogation takes 5 days, engine overhauls take 43.5 for the level 3 engineer and 49 for the level 2 engineer. The level 3 engineer can help the other engineer once they are done so the total time to do the overhauls is five days – Time in system 5 days.
  • Transit Prenglar – In this case the limit is the astrogation which takes 7 days. Time in system, 7 days.
  • Transit Cassidine – This time the astrogators win and the jump is waiting on the engineers – Time in system, 5 days.
  • Decelerate in Dramune – 4.5 days.

Total time: 26 days. Takes a little longer but still faster than the base 36 hours. If there was only one engineer, it would actually take longer than 9 days per system as one engineer just can’t do engine overhauls on two engines in each system that fast (unless they are level 5 or 6). You might as well stop over in the station each time unless you have a reason not to go into a system.

Final Thoughts

That’s it for this post. There are other aspects of the travel that I could talk about such as vector movement, the process of lining up for a jump, what happens to your calculations and alignment when you have to maneuver for a combat or something else, and a discussion on how long those alignment efforts take anyway. Some of those ideas I touched on in the posts I linked. I might look at these again in a future post or two as well.

What are your thoughts? What questions do you have? Share them in the comment section below.

Void Sickness

Traveling through hyperspace ain’t like dusting crops, boy!

  • Han Solo, Star Wars

While a little out of context (Han was actually referring to astrogation calculations), the quote still applies – faster than light (FTL) travel is not just a walk in the park.

In this post, I want to look at a mechanic for FTL induced illness, which I’ll be calling Void Sickness.  The name comes because I created this mechanic for my Star Frontiers games where FTL travel is accomplished by traveling through “The Void” or “Void Jumping”.  In that game, you accelerate up to speed (1% the speed of light) and then make a nearly instantaneous transition into and out of the Void to cross many light years.  The rules are a little vague on the actual duration but I’ve always used 1 second per light year.  When you re-emerge you are in a new star system (hopefully your destination if you got the astrogation correct).

But what happens physiologically when you make the transition?  You are entering, even if it is briefly, a dimension your body wasn’t designed for.  It’s natural that your body may have an adverse reaction to the transition.

During the Jump

First there is the physical manifestations during the brief time in the Void.  I always describe this as a confusion of the senses.  You can feel colors, hear tastes, see sound, etc.  And it could be different for different species or even individuals within a species.  I often use this picture to describe the visual sensations.

Negative image of a ship cockpit with colors and gradients shifted to produce an unnatural color palette.But what I want to talk about today is what happens after you exit the Void.

Aftereffects

Many games don’t worry about this.  They just assume that the PCs and others can experience FTL travel with no worries or side effects.  And that is absolutely fine.  If having potentially negative consequences of FTL travel is not something you want in your game, then you don’t have to have it.  But if you do, this is a possible mechanic you can use.

In my case, I wanted to add a potential downside to FTL travel that starts out fairly benign and uncommon but becomes worse the more and more you travel.  Until it possibly reaches a point that you simply don’t want to make any more interstellar trips unless you absolutely have to.  Here’s what I came up with.

Void Sickness

Void Sickness is not an uncommon effect of FTL travel and some people are more susceptible to it than others.  But even if you are susceptible to it, it doesn’t affect you on every trip.  It is also a condition that worsens, with both increased susceptibility and symptoms, the more times you engage in FTL travel.

I’ll present this as a percentage based system (since that is what Star Frontiers, which I originally developed it for, uses) but you can easily convert this to a d20 or other system if you want.

Original Version

This is the original version of Void Sickness I developed.  It’s actually pretty harsh, I’ll present a much milder version below.

To see if you are susceptible to Void Sickness you need to make a check against your Stamina (or CON or the equivalent from your system).  Since STA in Star Frontiers typically ranges from 30-70, you make a STA+20 check the first time you make a Void Jump.  If you make the roll, you do not suffer from Void Sickness on this trip and your base chance to avoid Void Sickness on all other jumps starts at 95% (i.e. if you roll a 95 or lower on d100 you are not sick).

If you fail this roll, you are susceptible to Void Sickness.  You suffer from the sickness on this trip and your base chance to avoid it on future trips is equal to your STA score.  Thus you are much more likely to succumb to it in the future.

On all future FTL trips, you make a roll against your resistance score.  If you succeed, you do not suffer from Void Sickness for that trip.  If you fail, you do suffer and your resistance score is reduced by one.

The impact of the Void Sickness is determined by the amount you failed your roll.  The difference between your roll and your resistance score determines both the strength of the effect and its duration.  This value becomes the penalty you suffer on all skill and ability checks and it lasts for that many hours.

For example: Drod, a dralasite, has a STA of 50 and is making his first interstellar trip.  He checks for his susceptibility to Void sickness by rolling a d100 and rolls an 76 which is 6 points higher than this initial check (50+20 = 70).  He is susceptible to Void Sickness and going forward his resistance score is only 50.  For this trip he suffers a relatively mild case and only has a -6 modifier to his skills and abilities for the next 6 hours.  If on a future trip,if  he were to fail the resistance roll again, his resistance would drop to 49.

A Milder Form

In its original form, the Void Sickness is something that everyone will succumb to eventually if they take enough interstellar trips and if you have a string of bad luck, you could succumb to it fairly quickly.  If you want the effect to be fairly rare, and slower acting when someone does have it, you can use the following variation.  With this form, it is probably something the PCs will never have to deal with but you could have Void Sickness in your campaign as setting material to use on NPCs.

In this form, the base chance the first time you make a jump is a flat 95% on a d100.  If you roll less than that you don’t have the sickness and never will.  You never have to roll again.  If you do fail the roll, you have a mild case this time (you are not going to fail by more than 5 points) and your resistance roll going forward is equal to whatever you rolled this time. (i.e. if you rolled a 98, your resistance chance for all future trips starts at 98). The effects and increase in susceptibility are as before.

Mitigations

If the occurrence of this illness is common, there will probably be a number of ways to deal with it from drugs that boost your immunity to other drugs that mitigate the effects.  If the occurrence is more rare, there may only be drugs to mitigate symptoms and there may not be anything specifically for Void Sickness but only the use of regular drugs to treat the symptoms.  Here are some that I use in my game.  All these are required to be administered by someone with the Medic skill.

VoidBoost

Cost: 25 credits

VoidBoost is designed to improve a being’s immunity and resistance to Void Sickness.  If administered prior to the Void Jump, VoidBoost raises the recipient’s resistance to Void Sickness by 20 to a maximum of 95%.  Only a single dose of VoidBoost can be administered for any given trip.  Additional doses have no effect.

Most starliners stock this medication for their passengers.  It is either provided for free as part of the passage fare or at a discounted cost.

VoidBlock

Cost: 40 credits

VoidBlock is a broad spectrum medicine designed to reduce the effects of the symptoms of Void Sickness.  It has no effect on the duration.  It works by reducing the penalty to ability and skill checks due to Void Sickness.  VoidBlock reduces the negative modifier associated with Void Sickness by 1d10+10 for 20 hours.  No more than one dose can be taken in a 20 hour period.  Any doses taken beyond the first in that time automatically have no effect.  VoidBlock cannot be taken in conjunction with VoidReduce.  If it is, neither drug has any effect.

Most starliners stock this medication for their passengers.  It is either provided for free as part of the passage fare or at a discounted cost.

VoidReduce

Cost: 35 Credits

Void Reduce is designed to reduce the duration of the effects of Void Sickness.  It has no effect on they actual impact of the symptoms.  A dose of VoidReduce decreases the duration of Void Sickness by 1d10+10 hours.  Only one dose of VoidReduce can be taken for any given occurrence of Void Sickness.  Any additional doses automatically have no effect.  VoidReduce cannot be take in conjunction with VoidBlock.  If it is, neither drug has any effect.

Most starliners stock this medication for their passengers.  It is either provided for free as part of the passage fare or at a discounted cost.

Other Medications

Depending on your game system there may be other medications already in the game that can mitigate some of the effects of Void Sickness.  You can make a judgement based on the effects of the drugs in your game.  For Star Frontiers, I allow the following:

  • Biocort – one dose of Biocort reduces the duration of Void Sickness by 1d5+5 hours. Only one dose of Biocort can be applied for a given occurrence of Void Sickness.  If administered with VoidBlock or VoidReduce, Biocort has no effect.
  • Stimdose – one dose of Stimdose reduces the effects of Void sickness by 1d5+5 for 10 hours.  Only one dose of Stimdose can be administered in a 20 hour period as per the standard rules.  If administered with VoidBlock or VoidReduce, Stimdose has no effect.
  • Neutrad (from Zeb’s Guide) – one dose of Neutrad reduces the effects of Void Sickness by 1d5 points and its duration by 1d5 hours.  Only one dose of Neutrad can be administered for any given case of Void Sickness.  However, if administered with any other medication, none of the other medications have any effect.

Side note:  Due to the way Neutrad affects Void Sickness, scientists believe that Void Sickness is some form of temporary radiation poisoning but the exact form of radiation is unknown and not reproducible outside of a Void jump.  Many companies contract with ships to carry small micro experiments that run during the Void jump in an attempt to understand the cause of this illness.

Converting to Other Systems

Adapting this to another system is fairly straightforward.

If you want to use this in a d20 or 3d6 based system, You could simply multiply the relevant ability score by 3, 4, or 5 to get the initial base percentage for Void Sickness resistance if you wanted to keep with the d100 percentage system outlined.  The multiplier would depend on how likely you want the occurrence to be but by default I’d use 4 as that maps the closest to the ability score range that I designed against.  In any other system just use a suitable modifier.

If you don’t want to use the percentage based system but use the core mechanic from your system, simply reduce the percentage by the appropriate multiplier.  e.g. for a d20 based system simply divide the resistance chance by five (and subtract that from 20 for a roll-over success system like D&D to get the target number.)  Penalties can still be just the difference between the roll and the target and the duration becomes the difference times the modifier used.  If you are using a 3d6 system the percentages don’t map as closely but it still works.  The net effect would be for a slower initial deterioration followed by a very rapid final decline.  If you are using a game with a dice pool system, a little more work would be required to convert the mechanic.

The hardest part to adapt would be the slow deterioration of the resistance chance.  Instead of a reduction on every failure, you could implement a reduction after every N failures, where N is probably the multiplier used elsewhere.  Or you could require a CON (or equivalent) check each time they suffer from Void Sickness.  If they fail, their resistance weakens.  If they succeed, their resistance doesn’t change.

Final Thoughts

I created this illness primarily as background flavor for my setting.  It’s not something I ever expect the PCs to suffer from.  Unless they want to.  If the PC’s background is such that they would have taken interstellar trips before the game starts, I give them the option to automatically select susceptibility if they want or to just roll.  It was more designed as something that NPCs could suffer from and that the PCs would have to deal with in that manner.  I also intended to use in some of the stories I was writing at the time (and that I may someday get back to).

Have you ever done anything similar in your games?  Does this sound like something you might use in the future?  Share your ideas, suggestions, and thoughts in the comments below.

Designing Out Loud – Void Jumping

This post originally appeared on the now-defunct Arcane Game Lore blog.

This post is running a little behind as I’ve been swamped with end of semester projects. One down, two to go.  Next week’s post might get impacted as well.

My last two articles (one, two), part of the November RPG blog carnival, talked about the unexpected in Void Jump travel. In this article I want to discuss some more details about Void travel in my game and the mechanics that will be used.  Or at least what I am considering for a first pass.

Some Constraints

Gravity Wells

In my universe, Void travel cannot start or stop anywhere.  If you are too close to a large mass, the gravitational field of that object prevents void jumping.  This was somewhat inspired by Larry Niven’s hyperspace.  I liked the idea of having to worry about the large masses that you are traveling by.  Unlike Niven’s hyperspace, getting too close doesn’t cause anything bad to happen, it just bounces you back into real space or prevents you from initiating a Void jump at all. Of course if the object is close, directly ahead, and you’re moving fast, things could get scary.

This has a couple of implications for FTL travel.  First, you have to get away from everything.  I have an exact forumulation for it but for a solar sized star, you need to get about 4 AU away from the star before you can jump.  Starting at a planet about 1 AU away, it takes abut 84 hours of acceleration at 1g to get out that far.  This means that at a minimum, if everything is aligned properly and everything works, a single insterstellar jump will take about seven days (assuming a 24 hour day).

Next, it means you only have to be accurate in your direction vector enough to hit that sphere around your target star where Void travel doesn’t work.  As long as you’re lined up well enough, you’ll drop out of the Void when you hit that gravity well.  This places an upper limit on how accurate you need to be.  Now, the question is, can you get out of the Void on your own or do you have to hit one of these gravity wells to come out of the Void?  I’m leaning toward the following combination.  You can get out on your own, but it’s much harder than being pulled out naturally by hitting a gravity well.  In this scenario, you want to try to hit the target gravity well when you can.

This also means that locations close to the mass source (star or large planet) are “shielded” by the “no jump zone”.  Any arriving ship or fleet has to arrive outside that zone so there will be advanced warning before they get to their destination (at least if anyone is looking).

Everything is Moving

Another constraint is that nothing is ever in the same place twice.  Planets orbit their stars which are orbiting the galactic center and moving relative to each other.  This means that no two jumps are ever exactly the same.  A jump from one planet to another, repeated just a few weeks later, means that both the start point and the destination as moved.  It won’t be by much, but if you remember from my last article, even a little bit of error can result in a huge wrong location.

So every jump needs its direction vector recalculated before you can start.  The good news is that this actually isn’t a very hard calculation.  Or rather it is a hard calculation but a good computer can do it relatively quickly.  There is a lot of data that goes into it but for game purposes, I’ve decided that the calculation can be done in under an hour.  All you need is your start time, your start location, and a good astronomical database that has the information about your departure and destination system.  However …

Getting Lined Up is Hard

Figuring out where you need to go is easy,  determining if you are actually going there is another story.  The problem is the same as the one above, everything is moving.  There is not really an absolute reference frame.  The problem is that you don’t just need to know your position relative to the star your leaving but relative to all the stars in the sector.  And it’s not really the position that matters but rather your velocity vector.  How are you moving relative to all of these objects? And how do you determine this direction down to arcsecond (or sub arcsecond) accuracy?

This can be overcome by the fact that you are moving quite a bit to get out of the gravity well.  As you move along your path, nearby stars will appear to move relative to more distant ones.  This is called parallax.  By measuring how much each of the stars move, and which direction they move, you can determine your vector in space relative to your departure and destination star.

There are some things to remember when trying to measure parallax.  First, you have to move quite a ways to measure any shift at all in stars; they are really far away.  Second, when you first start out, you’re not moving very fast so you don’t move very much between measurements.  This means that the more accurate of a measurement you need, the longer it is going to take as you need to have larger and larger baselines to measure small parallax angles.  You get these longer baselines by waiting longer and by accelerating so you’re moving faster and covering these distances faster.

What is the Jump Process?

Given all of this, what does a typical Void jump look like in game.

First, the astrogator computes the jump vector.  For this he needs to know the time of departure.  Plus or minus a few hours doesn’t make much difference.  This takes about an hour of time on the ship’s computer or could be requested from a central astrogation computer on the system’s data network if it exists.

Next the ship points in the general direction of the target system and begins accelerating.  Images are taken of the stars being measured for parallax.  As the ship continues to accelerate and covers more distance, new pictures are taken and the parallax measurements are made.  From this the course can be adjusted to make it more accurate.  This is repeated until the course is accurate enough.

Once the ship is lined up and the minimum jump distance is reached, the ship can engage whatever technology enables the jump and shifts to the Void, makes the trip, and emerges in the destination system.

At this point more standard navigation techniques can be used to decelerate and travel to the destination system.

How to Trigger a Jump

You may have noticed that I kind of glossed over actually making the jump.  That is going to depend on the setting.  Star Frontiers does it by hitting 1% the speed of light (of course that begs the question, 1% of c relative to what?).

For my world/game, the ability to enter the Void is controlled by a “Jump Field Generator”.  When you want to enter the Void, you turn this device on and it envelops the ship in a field that allows the ship to shift into the Void and make the jump.  Turning it off takes you out of the Void.

How Long Does it Take?

This really depends on the setting.  How fast can the ships accelerate?  What is the minimum jump distance? How long does it take to line up the ship?

If you want to use this idea, you’ll have to answer that for your own setting.  I’ll give you my answers.

How fast can ships accelerate?

For my setting, there is no artificial gravity.  Thus to get simulated gravity on a ship it has to accelerate.  But you also can’t accelerate too quickly or everyone gets squished.  By default, ships tend to travel by accelerating and decelerating at one standard gravity which in my setting is defined as 10 m/s/s for simplicity.  This means that accelerations are relatively low and it takes time to get from place to place.

What is the minimum jump distance?

For my setting, I’ve decided that the local gravitational acceleration (from everything smaller than the galaxy itself) has to be less than some specific value which I don’t remember off the top of my head as I’m writing this.  For a star like the sun, this distance works out to something like 4.05 AU.  At one standard gravity of acceleration, it takes about 84 hours to go from a planet at 1 AU out to the jump distance.  This sets a minimum time for a jump.

How long does it take to line up the ship?

I’ve thought a bit about this but I’m going to invoke a bit of handwavium here toward the end for the fine details.  There are several factors that go into it.

The first question is how accurate of a parallax angle can you measure. Modern systems dedicated to this can measure parallaxes of 10 micro arcseconds with lots of data on a 2 AU baseline (diameter of the Earth’s orbit) over five years.  So it is reasonable that the ships should be able to achieve 10 mili-arcsecond accuracy (1000x worse) on the same baseline. After all, they should have at least equivalent sized telescopes and detectors.  They just lack the time frame.  So we should be able to measure o.o1 arcsecond parallaxes on a 2AU baseline or 0.1 arcsec parallaxes on a 0.2AU baseline.

The next question is how big of a target are we trying to hit.  Assuming you have to hit the “no jump zone” around a solar sized star, that target is a direct function of the distance.  For a star 5 light years away, that 4 AU radius target corresponds to a direction accuracy of 2.6 arc seconds.  So if we can measure 0.1 arcseconds in 0.2 AU of travel, let’s assume that we should be able to get our course vector accurate to 2.6 arcseconds in about 0.4 AU (0.2 AU to get the first vector, adjust, and 0.2 AU to verify).

So how long does it take to travel 0.4 AU assuming 1g acceleration and starting at rest? 30.43 hours

Now a 10 ly jump requires an accuracy of 1.3 arcseconds.  The question is, how long should this take to dial in the desired accuracy?  I’m fond of inverse square laws so I’d say that double the accuracy requires 4 times the distance.  That means you have to travel 1.6 AU to get enough measurements and course corrections to achieve the desired accuracy.  Traveling 1.6 AU from rest requires about 60 hours.

Here’s where I will apply the handwavium quite liberally.  I could easily pick some numbers and justify the accuracy needed to achieve a jump and compute the travel time exactly needed to achieve that accuracy for a given distance.  And I could even provide the forumulas.  But it would be kind of messy.  However, I want something quick and simple.  I could present the data in a table to look up.  And I might do that as a later optional rule for those that want more realistic values.

But what I really want is something quick and simple that is easy to remember. And I want a 10 light year jump to take longer to line up than it takes to get out to the minimum jump distance.  I also want it to become unpractical to make really, really long jumps.  So let’s set the time required to line up the ship to the distance to be traveled, in light years squared in hours or 10 hours whichever is longer.  Or for those that like formulas:

Time = (d in ly)^2 hours

So a jump of one to three light years would take 10 hours to line up.  A five light year jump would take 25 hours, and a 10 light year jump would take 100 hours.

Putting it all together

That was a very long winded explanation for what in the end is actually a simple result.

If you want to make a Void Jump for distance of 9 light years or less, it takes 80 hours (notice I rounded it down to 80 hours from the 84 I was quoting above) to get out to the minimum jump distance at which point you are lined up and can make the jump.

If your want to make a Void Jump for a distance of greater than 9 light years, it takes the number of light years squared in hours to get the ship lined up accurately enough.  At which point you can safely make the jump.

Variations

Obviously that “simple” solution is based on starting at rest at a planet 1AU from the star and needing to get out to 4 AU before you can jump.  There are lots of variations on this scenario that you can imagine that will vary the time.  Possibilities include:

  • You’re starting further out in the system, maybe already beyond the minimum jump distance.
  • Instead of heading straight outward from the star, your destination is actually on the opposite side of the star and so instead of having to travel 3 AU to get to the minimum jump distance you have to travel up to 5 AU (if starting at 1 AU) or maybe even 8 AU if you’re on the other edge and have to go all the way across
  • A combination of both of the above.  You’re outside the gravity well but the jump vector crosses it so you have to move to get a different line to your destination
  • You get attacked or encounter something and have to maneuver while getting lined up.  Now you’re all messed up and you have to start over.
  • What if you accelerate at a higher (or lower) rate?
  • What if you don’t spend enough time lining up?

Are there any other variations that come to mind?  Are there any concepts that I should have explained better?  Is there something I overlooked?  Let me know in the comments below?

Your Final Destination – Exiting a Void Jump – November Blog Carnival – part 2

This post originally appeared on the now-defunct Arcane Game Lore blog.

RPG Blog Carnival Logo

My last post on Void Sickness along with reading Mike Bourke’s second portal article (I’m still a week behind but I’m catching up!), got me thinking about another aspect of Void travel that I like to use but which I don’t see talked that much about: where you come out on the other end.  And since I’m approaching it as something you can’t completely control, the exact location is somewhat unpredictable and can have unexpected results.  So this will be another entry into the November RPG Blog Carnival.  Enjoy.

Never the Same Place Twice

Last time I played with the Disruption parameter.  This time I want to talk about Repeatability.  When I was defining void travel in the previous post, I stated that the repeatability was “vague” which was defined as “A new Portal from the same origin may be directable to some point near where the old one was” in the original portal article that sparked my first post.  In his second article, he added, “but the exact same destination is unreachable” to the end of that when he summarized the detailed definitions.  In that second post I liked the definition he gave for “unpredictable” which was “A new Portal from the same origin will connect with another point completely at random, uncontrollably, within the destination plane of existence, perhaps restricted to a significant region.”

My idea of void travel falls somewhere between those two.  It’s not that reaching the exact same location is impossible, it’s just very unlikely.  You’ll always end up close (on a cosmic scale) unless you make a major mistake but probably not in the same location.  And in truth the chances of actually starting in the same place are slim to none as well depending on your definitions of location and the scale of what constitutes the “same origin” (Are you measuring in meters, kilometers, or AU?).  Given the two summarized definitions I’m actually leaning a little more toward unpredictable but both work.  The point is, the place you come out is always going to be different.  Let’s look at that and what it may mean for your game.

Non-repeatability

So why is it not possible to come out in the same spot?  From my perspective this comes down to two factors that related to how I treat void travel.  In my interpretation of how void travel works, whatever vector you have in the real universe when you enter the void is the vector you maintain in the void.  You can’t change your direction and you move in a “straight” line.  Which means you need to be lined up exactly right or you’re going to go way off course.

Stay on Target

Just how exactly do you need to be lined up?  Let’s look at a couple of examples.  Take a piece of paper.  Draw a small dot on it no larger than half a millimeter.  Now hold that up at arm’s length.  See how big that dot is?  Depending on the size of your dot and the length of your arm, that dot covers an angle of about 2-3 arc minutes.  If your direction vector were off by that much, how far off would you be at your destination?

I’m going to be generous and assume you drew a small dot and have a long arm and go with the 2 arc minute number.  Assuming you make a small void jump, say 4.3 light years, the distance to the nearest solar type star, Alpha Centauri, you’d be off target by only 5.5 billion kilometers.  Space is big, that’s not too bad, right?  Well, that’s about 36.7 Astronomical Units (the distance between the Earth and the Sun).  Which means if you were shooting for Earth, you’d be out by Pluto.  Depending on how fast your ship is, that may take a while to compensate for.

But an error of 2 arc minutes is pretty big.  We can do better than that.  Let’s say we can get our error down to the size of an arc second (1 degree = 60 arc minutes = 3600 arc seconds).  That’s equivalent to putting your dot about 24 feet (7.2m) away.  If we do that and make the same jump to Alpha Centauri, we’d still be off by about 46 million kilometers or 0.3 AU, roughly the distance between the Earth and Venus at closest approach.  (By the way, an error of 1 arc second means your ship moved laterally 4.8 mm after traveling 1 kilometer).  And if you make a jump twice as far, the error will be twice as large as it is really just the direction error (in radians) multiplied by the distance traveled.  Double the distance, double the offset.

Just based on that, you can see that you’re probably not going to come out at the same place at your destination no matter how hard you try.  Getting your vector to that accuracy is going to take some effort.  But there is another effect, the time spent in the void.

How Good is Your Clock?

The other aspect of determining your position is how long you spend in the void and how far you travel in a given amount of time.  If there are errors in your time keeping, this will translate into errors in the distance traveled.

Let’s use the example I gave in my earlier post: void travel occurs at the rate of one light year per second.  Now, a light year is 9.4607×1012 km.  That means that an error of a millisecond equal a distance of 9.4607×109 km (63 AU, roughly twice the distance to Neptune).  A microsecond error reduced that by a factor of 1000 and an error of only a nanosecond reduces that by another factor of 1000 or down to an error of only 9460.7 km, less than the diameter of the Earth.

Modern computers can get to about a 10 nanosecond resolution which means an accuracy of about 95,000 km roughly 1/4 the distance to the moon.  Depending on the technology you allow in your setting (and what you allow to work in the void), the accuracy could be better or worse than this.  But even with a microsecond error, the distance you’ll be off is only 0.063 AU.

So while there is an effect, and you probably won’t end up in the same spot, it is much less than the effect you can expect from an error in the velocity vector.  Depending on the story you’re trying to tell, that may or may not be negligible.

Impact on Your Game

We’ve seen what the scale of the effect is, what impact does that have on your game?  While the details will depend on you exact setting, here are three ideas off the top of my head.

Travel times

Given the natural variation in arrival locations, you are typically going to be off target which means the actual travel time to the destination is going to vary.  It will no longer be “three days” but “three to four days”.  You can’t really plan on exact time tables.

To put some numbers to that, assume you were off by the 0.3AU distance from earlier.  Assuming your ship is traveling at 1% the speed of light (3,000 km/s, just under 11 million km per hour), it will take you about 4.25 hours to cover that extra distance.  If you’re off by more or going slower, it will take even longer (and that’s ignoring a bunch of real world physics about changing direction and such which will only add to the time).

This means that you have to plan for and account for the extra time and it may add tension to a situation.  We only have 100 hours to reach the destination and stop the “big event”.  The jump and associated travel time takes 80+2d10 hours to just get to the location where the big event will happen.  Do the characters arrive with hours to spare or are they landing with only minutes until they have to spring into action?  What impacts will this have on their preparations? Will it limit what they can do or bring to bear in the situation?

Space Piracy

Again ignoring real world physics of matching velocities in space, the result of non-repeatability of void jumps means you’re probably not going to have space pirates lurking in the outer system for ships to appear and then pounce on them.  Even if you had hundreds of ships entering a system every day, the odds of one appearing near where a pirate vessel was lurking is really, really small.  The pirate ship could sit out there for years and never have an encounter.  This means that piracy, if it occurs, will happen near the population centers, at remote, fixed outposts, or on the outbound leg of a journey before the void jump when the routes are much more predictable.

Arriving in Formation

Remember this scene from Return of the Jedi? (0:43-1:04 is the relevant part if you don’t want to watch the whole thing).

That just isn’t going to happen with void jumping.  Even assuming that you can get the velocity vector the same for all the ships, which might be hard but could be possible (although not with everyone dodging in and out among each other like the fighters in the beginning of that clip) the timing variations between the ship computers will scatter everyone across tens of thousands of kilometers of space.  You will need time to regroup.  Which means you probably want to appear further out in the system to allow yourself that time which in turns means longer travel to your destination and a greater chance for discovery.

Or if you do allow for piracy to occur in the outer reaches of the system,  merchants and their escorts may be separated on arrival.  The convoy scattered across space.  Can the escorts get back to their charges before the pirates attack or do they only arrive in time to extract revenge for damage done?

Void Travel is Unpredictable

From the above thoughts, it’s fairly obvious that this method of FTL travel has the potential to add some randomness and unpredictability into your game.  Whether to add tension or just flavor, there is no real reason that void travel should be routine.  Are there other ideas for impacts that come to mind because of the unpredictability?  Let us know in the comments below.

Comments

Mike Bourke – November 24, 2015 at 11:28 am

There’s an obvious solution: the very short void jump. You arrive and find yourself 30 AU away from where you want to be? Jump for long enough to travel 29 AU. This distance is short enough that the final error will be relatively small.

Now, I happen to think that this tactic, while eminently sensible, is not as desirable as the additional flavor that the randomness gives. That leads me to suggesting that in order to make a jump, a ship has to utilize a minimum amount of power or more, which in turn means that there is a minimum jump distance.

This wouldn’t completely eliminate the viability of the tactic; it would mean that the most practical approach is to aim for a point half your anticipated error away from whatever the minimum jump distance is. For convenience, let’s say that your maximum error is 10AU per light year, and you are jumping 20 light-years, and that the minimum jump is 150 AU:

10 AU x 20 light years is 200 AU maximum error. Half that is 100 AU, so that’s the mean error that you will experience. But that leaves you too close to make the minimum jump, so you move that destination point out by the minimum, and aim to arrive 250 AU away. That means that your range of arrival points is 250±100 AU – so even if you get as close to your ultimate destination as possible, you are still a minimum jump away, and might be as much as 350AU.

The thing is that picking just any point that far away is not good enough; you would need some standard navigational reference points from which to get your precise distance for the second jump. Observations would take time, and without standard references, you might have to wait for weeks, months, or years for the objects you are measuring (presumably outer planets) to have moved enough to permit navigation.

And standard reference points for a jump means that your arrival point is a much smaller volume of space – making piracy possible after all. Not easy, but not entirely out of the question, either.

Mike Bourke – November 24, 2015 at 6:58 pm

Alternately, maybe a ship develops some sort of energy “charge” that simply delays making another jump for a period of time. That would prevent the “stop short and recalibrate” dodge – if there’s a deadline involved.

Tom – November 24, 2015 at 9:26 pm

Yes, both of those are possible implications as well. I like the minimum power required idea. I didn’t include it here but I also utilize limit on gravity wells. Kind of like Larry Niven’s hyperspace. You can’t get too close to a large mass and still have your void jump system work. This actually counter acts some of the implications depending on how you implement it. I think that will be another void jumping article at some point.

Void Travel Sickness – November RPG Blog Carnival

This post originally appeared on the now-defunct Arcane Game Lore blog.

Update: I hadn’t intended for this post to be part of the November RPG blog carnival, the topic of which is “The Unexpected“, even though the timing of it was inspired by a blog carnival post. However, in discussions with Mike Bourke, the host of this month’s blog carnival topic, he felt that it would be fine for inclusion. His argument was that since the degree to which (and even if) you are affected is unknown each time you travel, it fell within the realm of the topic. If the guy running the show agrees, who am I to argue? So this is now my entry into the November RPG blog carnival. Thanks for the encouragement, Mike.

In most sci-fi games, we typically take interstellar faster than light travel for granted with no individual consequences.  What if that wasn’t true?

This is actually something I’ve thought about off and on for the past few years.  It even makes a subtle appearance in my book, Discovery.  I was reading an article, The Unexpected Neighbor: Portals to Celestial Morphology 1/4, on Campaign Mastery and the discussion about disruption triggered me to think about my Void Travel Sickness mechanic once again.  I thought I’d write it up.

Defining Void Travel

First we need to start off with what Void travel actually is.  Basically it is a way of quickly traversing vast interstellar distances nearly instantaneously by traveling through another dimension (the Void). The ship plots/calculates a “Void jump” and then somehow engages the physics of the universe to move from real space to the Void, travel a bit in the Void where distance is greatly compressed relative to real space, and then shift back to real space at the destination.  Since distances in the Void are so compressed (or is it time?), a short trip in the Void corresponds to a long trip in the real universe.

The is the type of interstellar travel used in Star Frontiers (at least in the Knight Hawks ship expansion), basically stating that when traveling at 1% the speed of light (the mechanism to invoke the physics), one second travel in the Void, moves you 1 light year in the real universe.

In terms of the parameters Mike defines in his article, these Void jumps can be considered mono-directional, temporary, immense, stable (relative to the ship), safe, and vague (relative to the endpoint location) portals.  I want to play with that safe part.

What happens to the participants during that brief time spend in the void is up to the GM or the designer of the game system.  In my book, I described it thus:

Everything on-board the ship went crazy.  Colors seemed to invert.  Any displays that had previously showed empty space outside the ship just seemed to just vanish.  Sounds were distorted.  The sense of touch just disappeared.  It felt as if they were being pulled into their seats and weightless at the same time and everyone felt a strong case of dizziness, as if you had been spinning incredibly fast and then just stopped, and had to walk a straight line but couldn’t.

“What’s going on?” Allison asked, looking around a little wildly.  Her voice sounded muffled, as if speaking under water.

“I don’t know,” Alex replied his voice also distorted.  “You’re the expert on …”  And then the effect was gone.  “the jump process,” he finished.  The strange effect was gone but it was replaced by alarms and sirens going off throughout the ship.

“That was weird,” he added almost to himself.  While the strange effect was gone, Alex still felt a bit nauseous but it was passing quickly.  Looking at Allison, the slight greenish cast to her complexion indicated that she felt it as well.

but it really could be anything you want.

Void Travel Sickness

What if the effects of Void travel weren’t just brief and temporary disorientation and nausea but could be something more serious?  How do you decide if you’re susceptible?  Is it a binary option, i.e. you either get sick every time or not at all?  Does it get progressively worse? Can you prevent it?  This are all things to think about.  I’m not going to answer all of those questions in this particular article as some of them depend on the game system itself and I’m just going to cover general principles.  The ones I miss I’ll revisit at a later date when I implement a final version of the system in my Designing Out Loud series.

For my version of this, everyone is potentially susceptible and no one is completely immune.  However, even if you are susceptible, it doesn’t mean you experience the effects every time and just because you aren’t susceptible, it doesn’t mean you won’t occasionally be caught by it.  You might go for several jumps without any ill effects, and then be floored by the next one.  And I want it to be a progressive condition, meaning that as time goes on and you make more jumps, you become more susceptible, no matter where you start on the susceptibility spectrum.  So let’s start looking at details

Susceptibility

Not everyone succumbs to void sickness as easily as others.  Some people just seem to be immune to it while others get hit every time they make a jump.  Each character should have a susceptibility score that represents the probability that they will succumb to void sickness on any give jump.  Because I want this to be fairly fine grained and want the increase in susceptibility to be very gradual, this roll should be percentile (d100) based and the susceptibility score should range from 1-100.

The easiest way to initially determine susceptibility would be to make some sort of constitution or stamina check the very first time you make an interstellar jump.  For characters in a sci-fi campaign, where you can assume they have made jumps in the past before adventuring, you could make the check as part of character generation.  Passing or failing this first check indicates whether you tend to be immune or susceptible to getting void sickness and you can then determine your starting susceptibility score.

You start by determining your base score.  In a d100 system, like the one I’m designing or Star Frontiers, your base score is simply your constitution characteristic, in this case Stamina.  If you’re using this in a d20 or 3d6 characteristic system, you’d want to multiply that characteristic by five first. to put it on the same scale.  If your game of choice uses some other scale for ability scores, multiply by the appropriate factor to get the value on a scale of 1-100. (i.e. a 2d6 game would multiply by 8).

To this base chance you simply add your “first jump modifier”.  If you passed that first check, give the character a +20 to their susceptibility score.  They are fairly immune.  If you failed, give the character a -20.  They tend to suffer from void sickness more often. This becomes your character’s susceptibility score for the game.

Increased Susceptibility

I also want the chance to succumb to increase the more jumps you make but not very quickly.  (This is why starship captains are all young an dashing and admirals are all old, stay home, and only travel grudgingly :-) ).

The mechanic for this is straightforward.  If you fail a susceptibility check, your score drops by one.  If you pass, nothing happens.  This is why I wanted the check to be percentile based, so that the change is small on any single failure.  If it was d20 based (or something similar), a single point change is a big effect.

This mechanic has a couple of impacts.  First, those with high scores (i.e. immune) will often pass their checks and have little change in their score.  Those that are susceptible, however, will deteriorate much quicker as they fail more often.  Also, as time goes on, the rate of deterioration increases as they fail more often, regardless of where they started.  This was intentional as I wanted the overall effect to be that there will come a point that you decide that you’re done with interstellar travel or willing to accept that every jump will be a miserable experience.  However, I didn’t want that to come too quickly.

If fact, for player characters, instead of rolling, I’d probably declare that they are all void sickness “immune” and just start their susceptibility score at STA+20.  To goal is to have it be an occasional but real concern to add some suspense and drama but not really debilitating (at least to start).

On Any Given Jump

To see if you suffer the effects of void sickness, simply roll d100 against your susceptibility score with a 100 always being a failure regardless of the susceptibility score.  Success means a brief moment of disorientation/nausea/whatever the minor effects (if any) are.  Failure means more debilitating effects.  This is going to be system dependent.  However, there is the question of scale.

One option is to just make it a binary solution.  Success = no effect, failure = some fixed effect.  In this case the magnitude of the effect is independent of the degree of failure.  Everyone who fails suffers the same effects.

A second option is to have the effects be dependent on further die rolls.  Maybe the effect has a variable time frame (i.e. -10% on all skill checks for 1d10 hours) or varying severity (i.e. -1d6*5% to all skills for an hour) or both (-3d10% from all skill/ability checks for 1d6 hours).  Or it could be anything that the system designers/GMs want to implement.

The final option would be to have the effects dependent on the degree of failure with the difference between the roll and the susceptibility score determining the magnitude of the effect.  Thus you could fail by just a little on only suffer minor effects or fail spectacularly and be down for a while.

The first and second option are good if you want those with high susceptibilities to potentially suffer serious effects when they do happen to fail while the third one plays into the idea that those with strong resistances don’t suffer too badly while those that suffer chronically suffer extremely.  It just depends on the flavor you want.

Prevention and Treatment

I’m not going to cover this topic in this particular post as it really depends on the game setting and what the GM desires (if adding this to an existing system).  Maybe there are medicines or techniques that can boost your immunity.  There are most likely medicines that can be used to counteract the negative effects.  What they are will depend on the game.

A Work in Progress

This is obviously a first pass at the design.  As I test it out and look at it more closely there will probably be other refinements and details I’ll make.  What do you think?  Have you ever implemented a void (portal passage) sickness in your game?  What worked and what didn’t? What would you add or change to what I described?  Share your thoughts and ideas in the comments below.