Inaccurate Jumps

[DaveT]

Hi,

Anyone have any guidelines on inaccurate jumps?

There seems to be 2 parts to this:

1) The time part. If say you are in jump space 6 hours longer than planned that means the destination world will have moved on I suppose. I think I read the orbital velocity of the Earth is roughly 1/10,000th the speed of light which is pretty Taylor Swift. So 6 hours for the Earth (in a straight line for simplicity) is...err...hang on... 648,000km (does that sound about right?). So that would add to the journey quite significantly and of course you could be out by as much as 15 hours if incredibly unlucky.

2) The consequence of not rolling high enough on the astrogation check. RAW is pretty vague here mentioning being dumped somewhere in the inner system so I guess that could be several Astronomical Units on a bad day which would make the journey a heck of a lot longer. For part of an adventure I'd choose a distance that worked for the narrative but for a trading campaign this seems to be quite an important area. Is there an article on this somewhere that I may have missed or do you guys just wing it (in the best tradition of Traveller referees through the decades )?

 

[phavoc]

A lot of this comes down to referee decisions. According to the rules, all planets and major objects have 100D jump shadows that will pull you out of jump space if your path crosses them. Which means, in some cases, you couldn't even make a jump to your destination without first coming out of jump space, re-aligning your path, and then jumping again. Plus it gives a lot of weight to ship arrivals/departures being above or below the plane of the elliptic in a system.

But that makes gameplay a big pain in the ass. It's much easier to come up with simple rules to somewhat account for these things, hence the jump mishap tables.

Also there is the concept that ships retain their heading and speed upon arrival in the new system that they had when they entered jump space in the old system. If you looked at the rules that would mean you'd plot your jump so you'd be arriving heading in the same direction as the planet is traveling. Or you'd arrive while the planet is coming towards you (to combine velocities). If you were late and were too close to the planet you'd still hit the 100D limit and be forced out of jump space. While we know that is something you don't want to do, I can't recall ever seeing a rule that says if it DOES happen, here's the bad things that happen, so you don't want to do it. Otherwise it seems like a smart idea to do so because it's simple and works and guarantees you some positive benefits.

As far as popping out in the inner system, well, that's one way of doing it. But you shouldn't limit yourself to only that. I think that line in the CRB was written to give some ideas to a ref, but it shouldn't be taken literally. The misjump could have you arriving a few hours, a day, a few days, even a week away from your destination. It's whatever you as the ref want to impose that will help you plan your adventure with your PC's.

 

[ShawnDriscoll]

Keep an eye out for the character's effect from their astrogation skillcheck. Helps with narration for what happens next, and how well it happens.

 

[Condottiere]

The chances of a misjump on a well-maintained ship, during a routine flight, along a regular route, should be incredibly small.

 

[CosmicGamer]

Or you'd arrive while the planet is coming towards you (to combine velocities). If you were late and were too close to the planet you'd still hit the 100D limit and be forced out of jump space. While we know that is something you don't want to do, I can't recall ever seeing a rule that says if it DOES happen, here's the bad things that happen, so you don't want to do it. Otherwise it seems like a smart idea to do so because it's simple and works and guarantees you some positive benefits.

For me, the standard conventions, space lanes, flight paths are

Departures are via the trailing side of the location you are leaving (the path just traveled by the location as it orbits).
Arrivals are via the leading side (direction the location is traveling as it orbits)

One of the reasons why is so that travel time is reduced. Planet moving in orbit to decrease distance and time for arrivals to reach the planet and helps increase distance and reduce the time for departures.

If as said, no rules stating the negative side effects of being forced out of jump due to being within the 100d limit. Also not much mention of going for a "safe" point at the 110d limit "just in case". Seams to mostly mention arrivals and departures right at the 100d as the norm.

 

[Tom Kalbfus]

A lot of this comes down to referee decisions. According to the rules, all planets and major objects have 100D jump shadows that will pull you out of jump space if your path crosses them. Which means, in some cases, you couldn't even make a jump to your destination without first coming out of jump space, re-aligning your path, and then jumping again. Plus it gives a lot of weight to ship arrivals/departures being above or below the plane of the elliptic in a system.

But that makes gameplay a big pain in the ass. It's much easier to come up with simple rules to somewhat account for these things, hence the jump mishap tables.

Also there is the concept that ships retain their heading and speed upon arrival in the new system that they had when they entered jump space in the old system. If you looked at the rules that would mean you'd plot your jump so you'd be arriving heading in the same direction as the planet is traveling. Or you'd arrive while the planet is coming towards you (to combine velocities). If you were late and were too close to the planet you'd still hit the 100D limit and be forced out of jump space. While we know that is something you don't want to do, I can't recall ever seeing a rule that says if it DOES happen, here's the bad things that happen, so you don't want to do it. Otherwise it seems like a smart idea to do so because it's simple and works and guarantees you some positive benefits.

As far as popping out in the inner system, well, that's one way of doing it. But you shouldn't limit yourself to only that. I think that line in the CRB was written to give some ideas to a ref, but it shouldn't be taken literally. The misjump could have you arriving a few hours, a day, a few days, even a week away from your destination. It's whatever you as the ref want to impose that will help you plan your adventure with your PC's.

But the planet is not in jump space!
How about this Your ship goes from planet A to planet B which is located 4 parsecs away, however 2 parsecs away is a nebula which is 1 parsec wide and 2 parsecs away on the line in normal space between planet A and planet B. The nebula blocks line of sight between planet A and planet B, it appears as a black cloud of dust obscuring stars behind it, but your star chart indicates the system you want to go to is directly behind it. So can you make the 4 parsec jump even though the nebula is blocking your line of sight? If Jump space is a higher dimension, there should be no trouble in making the jump, as the nebula is not in Jump Space. However if the Jump Drive is like a warp drive, then the nebula is in the direction of travel.

 

[Reynard]

"1) The time part. If say you are in jump space 6 hours longer than planned that means the destination world will have moved on I suppose.... So that would add to the journey quite significantly and of course you could be out by as much as 15 hours if incredibly unlucky.

2) The consequence of not rolling high enough on the astrogation check. RAW is pretty vague here mentioning being dumped somewhere in the inner system so I guess that could be several Astronomical Units on a bad day which would make the journey a heck of a lot longer. For part of an adventure I'd choose a distance that worked for the narrative but for a trading campaign this seems to be quite an important area...."

The time factor merely states you are in Jump Space that much longer and that's the weird time distortion of JS. The third paragraph under Jump Travel is the important one. An Accurate Jump, no matter how long in Jump Space, gets you close to your mark while an Inaccurate Jump messes you up slightly and can be, at worst, a minor adventure especially as an encounter. Even merchants have to deal with this like a truck stuck in traffic on a highway. Fate doesn't care about your time schedules.

In any RPG, setbacks should be opportunities for both Ref and players and something to remember later.

 

[Reynard]

"If Jump space is a higher dimension, there should be no trouble in making the jump, as the nebula is not in Jump Space. However if the Jump Drive is like a warp drive, then the nebula is in the direction of travel."

Two things to remember with Traveller Jump. Space is really, really BIG! Even the gravity well of a star takes up only >< this much space in a one parsec sphere so bumping into gravity wells is much less an issue. Nebulas can take up a lot of 'space' but they are massive 'gas' clouds. The one you described would be an absorptive nebula concerning the light passing into it but is incredibly thin and therefore, by volume, has little concentrated mass to cause gravity issues. Jump ships and Warp ships pass through with relative ease.

For Jump ships, you do not need to visibly see your destination. That's why those ship computers are loaded with the most up to date charts while having the ability to constantly compute known star system movements. Your astrogator is reaffirming known coordinates and attempting to nail down the possible location down to the 100d at time of Jump not looking out the window. That's why an Inaccurate is mere hours or days off the target. A full blown Misjump is just catastrophic bad luck or incompetence.

 

[F33D]

Hi,

Anyone have any guidelines on inaccurate jumps?

There seems to be 2 parts to this:


2) The consequence of not rolling high enough on the astrogation check. RAW is pretty vague here ...

The only consequence of not rolling high enough on the Astro check is having to reroll it: "If the check is failed, then the astrogator must plot the Jump again. A Jump cannot be made until the astrogation calculations are complete." pg.141 Core Rule book.

If your engineering roll is a 2 (worst possible) and you are past 100D from a world using refined fuel & maintained/repaired drives, you cannot misjump

 

[CosmicGamer]

2) The consequence of not rolling high enough on the astrogation check.

The only consequence of not rolling high enough on the Astro check is having to reroll it: "If the check is failed, then the astrogator must plot the Jump again. A Jump cannot be made until the astrogation calculations are complete." pg.141 Core Rule book.

Unless there is some errata? I always thought it odd.

For a normal everyday jump,
There is no danger
It's an easy task
No time pressure as you can start working on this days before the jump if you wish.
Nothing interesting happens if you fail.

The opposite of

The Referee should only call for checks:
• When the characters are in danger.
• When the task is especially difficult or hazardous.
• When the characters are under the pressure of time.
• When success or failure is especially important or interesting.

If your engineering roll is a 2 (worst possible)

Worst on the dice. Not the worst possible with DMs.

If your engineering roll is a 2 and you are past 100D from a world using refined fuel & maintained/repaired drives, you cannot misjump

I acknowledge what you are trying to say but again, not 100% accurate. Just stick with

A full blown Misjump is just catastrophic bad luck or incompetence.

 

[DaveT]

2) The consequence of not rolling high enough on the astrogation check.

The only consequence of not rolling high enough on the Astro check is having to reroll it: "If the check is failed, then the astrogator must plot the Jump again. A Jump cannot be made until the astrogation calculations are complete." pg.141 Core Rule book.

Unless there is some errata? I always thought it odd.

For a normal everyday jump,
There is no danger
It's an easy task
No time pressure as you can start working on this days before the jump if you wish.
Nothing interesting happens if you fail.

The opposite of

The Referee should only call for checks:
• When the characters are in danger.
• When the task is especially difficult or hazardous.
• When the characters are under the pressure of time.
• When success or failure is especially important or interesting.

Hmm. Seems I read what I thought that section should say, not what it actually does say.
I agree this is a bit consequence-free for my liking.

I think in MTU I'll go with Shawn's approach and say an effect of 6 is needed for a super-duper accurate jump and anything less means some error has crept in. So an effect of 5 might be an extra couple of hours travel time while just barely passing the check might add a few days to the journey.

This would make good navigators more valuable crewmembers (provided the Astrogators' Union can clamp down on expert computer programs taking their jobs away). It would also add some justification for commercial vessels carrying more than one pilot as it's not like they have anything to do while the ship is in jump space.

 

[F33D]

Worst on the dice. Not the worst possible with DMs.

For the situation I outlined ( a standard jump) THAT is the worst number (INCLUDING ALL DM's) that can be rolled.

 

[F33D]

The opposite of

The Referee should only call for checks:
• When the characters are in danger.
• When the task is especially difficult or hazardous.
• When the characters are under the pressure of time.
• When success or failure is especially important or interesting.

Jump Astro checks are considered "especially difficult". Understanding jump mechanics being the ne plus ultra knowledge for a civilization. You are either a minor race or a MAJOR race...

 

[Reynard]

Yeah, misjump is improbable as long as those four possible modifiers aren't called into action such as taking jump damage just after topping off the tank at a gas giant and still in the GG's 100d and the antagonist isn't giving up. On the other hand, inaccurate jumps still can be an issue with a bad die roll on the Engineer task. You think it's impossible, as we found out, that a low roll with a spritz of a jump in need of repair would have us chasing a gas giant for a lot longer than planned.

No really, be glad misjumps are sooooo rare! 1d6 direction by 1d6 parsecs is a killer.

 

[F33D]

On the other hand, inaccurate jumps still can be an issue with a bad die roll on the Engineer task.

Yep. I like that in there. Makes the game more exciting.

 

[Condottiere]

Theoretically, you could get a preprogrammed USB stick for a nominal sum, that has a precalculated course based on the latest astrogation data available from both the embarked system and the destination, that will autopilot your ship to a specific transition point.

It simplifies traffic control as well.

 

[Reynard]

That sounds familiar. Wasn't it once possible to buy a one shot star chart to a particular destination from the starport?

 

[Condottiere]

 

[F33D]

That sounds familiar. Wasn't it once possible to buy a one shot star chart to a particular destination from the starport?

In MGT this is all it says on that topic, "Astrogation can be done in advance
(a Jump is normally plotted while the ship is travelling out to the hundred-diameter distance)."

Would be an interesting way to send a ship to a destination they didn't intend... :twisted:

 

[Jeraa]

That sounds familiar. Wasn't it once possible to buy a one shot star chart to a particular destination from the starport?

I know Classic Traveller had them.

In cases where a generate program is not available, starports have single-use flight plans (in self-erasing cassettes) available for all worlds within jump range for Cr10,000 per jump number.