Jump accuracy in Mongoose Traveller?

[Hal]

Hello Folks,
Page 3 of the Main rule book has this intriguing snippet...

"Referee: Anyway, you’ve just jumped to the Cogri system. You’re
about two million kilometres out –
Chris (Morn): ‘Accurate’ as usual, Kathya! Only twice as far away as we should be.
Claire (Kathya): The longer it takes us to get to the starport, the
longer it is before you get us into trouble.
Referee: Ahem. As I was saying, you’re about two million k out, and
you’re picking up a distress call."

Yet, when I look at the book for rules regarding jumping and being somewhat inaccurate, I don't find the specific rules. I must not be looking at the right place. Anyone know where the rules are regarding the plotting of a jump and the results being that the navigator was off and the distance was twice what was expected?

I have both the main rule book and the High Guard book.

The ONLY reference I can seem to find relating to the issue of accurate jumps is this on page 141:

"When the ship exits Jump space after an accurate Jump, it tends to arrive close to the target world, but outside or on the verge of the hundred-diameter limit. Inaccurate Jumps just dump the ship somewhere in the inner system, requiring a long space flight."

This seems to be strictly a judgment call on the GM as to how far off/away from target the astrogator was. I'm also guessing that inaccurate jumps occur only on a miss by 1? Because earlier on, it states that the astrogator must have a successful task roll or they must try again.

Color me confused.

 

[Xerxeskingofking]

Hello Folks,
Page 3 of the Main rule book has this intriguing snippet...

"Referee: Anyway, you’ve just jumped to the Cogri system. You’re
about two million kilometres out –
Chris (Morn): ‘Accurate’ as usual, Kathya! Only twice as far away as we should be.
Claire (Kathya): The longer it takes us to get to the starport, the
longer it is before you get us into trouble.
Referee: Ahem. As I was saying, you’re about two million k out, and
you’re picking up a distress call."

Yet, when I look at the book for rules regarding jumping and being somewhat inaccurate, I don't find the specific rules. I must not be looking at the right place. Anyone know where the rules are regarding the plotting of a jump and the results being that the navigator was off and the distance was twice what was expected?

I have both the main rule book and the High Guard book.

The ONLY reference I can seem to find relating to the issue of accurate jumps is this on page 141:

"When the ship exits Jump space after an accurate Jump, it tends to arrive close to the target world, but outside or on the verge of the hundred-diameter limit. Inaccurate Jumps just dump the ship somewhere in the inner system, requiring a long space flight."

This seems to be strictly a judgment call on the GM as to how far off/away from target the astrogator was. I'm also guessing that inaccurate jumps occur only on a miss by 1? Because earlier on, it states that the astrogator must have a successful task roll or they must try again.

Color me confused.

short answer, the 1st ed rules leave that to DM fiat.

2nd ed rules say, shortly after the paragraph you quoted, that this sort of minor misjump puts you 100-600 diamiters off the target world (for a earth sized planet, about 1.2-7.2 Million Km).

this is explicitly caused by a failure of the engineer (j drive) check by 2 or more (a miss by 1 gives timey-wimey effects. roll 1d6 twice, one for how many days extra the jump takes by outside reckoning, and once for how many days the players experience). a miss of 3 or more means your Going To Have A Bad Time.

bear in mind, assuming eng (j drive) 1 and +1 form Edu (or a assist of at least +1 form the nav check), the only way to fail a jump-1 check is by rolling snake eyes, and J2 is 1 harder (so, given the same +2 form skills and assist, pass on a 3, fail -1 on a 2).

for a j-6 jump, you better have a damm good engineer, as its a 2d6-2 roll before skills come into play, or a 16% chance of success.

 

[MThompson016]

There's the Jump Prep Task chain on page 141:
Astrogation: DM of 4-J number. Must be made pass or fail to jump
Divert Power: Average EDU Engineer (J-Drive) check
Jump: 2d6+Effect of Divert Power-2 per Jump drive hit-2 for unrefined fuel, -8 if within 100d limit

If the final check is below 8, it's an inaccurate jump, dropping the ship somewhere in the targeted system.

It does look like a judgement call in this case as to how inaccurate the jump is.

Has there been any errata on the topic?

 

[Spinward Scout]

this is explicitly caused by a failure of the engineer (j drive) check by 2 or more (a miss by 1 gives timey-wimey effects.

Timey-What?!

 

[robject]

If there is errata, it will hopefully sync with Traveller5's rules on jump breakout, which have what I think are reasonable guidelines.

 

[Hal]

If there is errata, it will hopefully sync with Traveller5's rules on jump breakout, which have what I think are reasonable guidelines.

By chance, are we talking about the scatter rules where the ship exits at a range of 12 plus a flux roll?

If yes, then the distances for scatter include a range of .0033 AU's at Flux = -5 to a distance of 1002 AU's at flux = +5.

I hope I'm reading THOSE rules correctly, because if I am, that's one helluva scatter! Imagine having to make up 1,002 AU's distance to reach your destination!

"Captain? Um, as best as I can figure, we're about 1,000 AU's from our planet destination, and we don't have any ice asteroids showing up on our sensors out here. Should we attempt a radio distress call and hope someone comes out with extra fuel, or do you want me to plot a course for the destination and enter emergency low berths?"

 

[robject]

By chance, are we talking about the scatter rules where the ship exits at a range of 12 plus a flux roll?

If yes, then the distances for scatter include a range of .0033 AU's at Flux = -5 to a distance of 1002 AU's at flux = +5.

I hope I'm reading THOSE rules correctly, because if I am, that's one helluva scatter! Imagine having to make up 1,002 AU's distance to reach your destination!

"Captain? Um, as best as I can figure, we're about 1,000 AU's from our planet destination, and we don't have any ice asteroids showing up on our sensors out here. Should we attempt a radio distress call and hope someone comes out with extra fuel, or do you want me to plot a course for the destination and enter emergency low berths?"

In Mongoose's case, there would probably not be a flux roll. It'd be represented in some other way, like just a 2D table.

But something like that, yes. The call for adventure.

...If I were the referee, I would certainly put an iceteroid close by, probably with an artifact at its core. What referee strands his players with no recourse but to die?

...ah, there's always the Out Of Gas scenario from Firefly.

...and there's the Alien Visitation scenario.

...or OMG We Stumbled Upon The Zhodani scenario.

...or Hey Who Put That Planet There scenario.

Wow, there's lots of options here.

 

[Hal]

In Mongoose's case, there would probably not be a flux roll. It'd be represented in some other way, like just a 2D table.

But something like that, yes. The call for adventure.

...If I were the referee, I would certainly put an iceteroid close by, probably with an artifact at its core. What referee strands his players with no recourse but to die?

...ah, there's always the Out Of Gas scenario from Firefly.

...and there's the Alien Visitation scenario.

...or OMG We Stumbled Upon The Zhodani scenario.

...or Hey Who Put That Planet There scenario.

Wow, there's lots of options here.

We're at different ends of the spectrum where it comes to rules I think...

How many times does a GM have to exercise the power to save the player characters before he starts to wonder whether the rules should have had more restraint built into them? Then, how many times will the players be aware of the rules, and know that they've gotten a lucky break every single time the dice went against them?

Then there is the other aspect of rules that need to be dealt with...

The rules have implications for the rest of the game universe. Ships that can end up 1002 AU's from their target point, or are dumped out of Jump Space because there was a dead rogue world in deep space absent any stars - that means more ships lost in space, which in turn has deeper implications for trade etc.

So, for me, IMTU, the scatter rules would have to be tamed a bit more before I'd use anything like them. As GM, I know it is my right, but at the same time, discussing the OTU and the implications of the rules on the OTU is what some of us GM's take the time to think about (when we're bored right?!!!!).

On that note - I rather like some of what is in MgT, and the Astrogation effects on a jump are worth pursuing for ANY other version of Traveller, not just MgT.

 

[ShawnDriscoll]

Depending on the current situation, and where the crew jumped to, I either allow the ship to arrive at a system normally or with some issues.

I always have at least two ways out of any situation the players find themselves in, even when the players think they have painted themselves into a corner. Some ways may be less pleasant for them at least in the short run though.

 

[Fovean]

Ive been using this little Astrogation Effect table since MgT 1e:

+1 or greater: arrive 100diam limit, save 2D hrs on jump
+0: arrive 100diam limit, normal time variation
-1: arrive 100+ (10-60) diam, normal jump time variation
-2: 100 - 300 diam, normal jump time variation
-3: 200 - 700 diam, plus 10% jump time
-4: 200 - 1200 diam, plus 20% jump time
-5: 1D AU
-6: 10 - 60 AU
-7 or less: 1D x 1D parsecs

Coarse, but avoids TPK because they are still within the Oort Cloud on a pretty bad roll.

 

[robject]

We're at different ends of the spectrum where it comes to rules I think...

How many times does a GM have to exercise the power to save the player characters before he starts to wonder whether the rules should have had more restraint built into them? Then, how many times will the players be aware of the rules, and know that they've gotten a lucky break every single time the dice went against them?

Certainly more frequently than one in thirty (in a given game night, we'll typically either jump once, or jump lots but handwave them). But, I suspect we're not really on different ends. As referee, I tend to not use all of the rules, all of the time (and even that may be overstating). I am just assuming, but maybe you are the same way.

 

[Hal]

Certainly more frequently than one in thirty (in a given game night, we'll typically either jump once, or jump lots but handwave them). But, I suspect we're not really on different ends. As referee, I tend to not use all of the rules, all of the time (and even that may be overstating). I am just assuming, but maybe you are the same way.

I might forget a rule or two from time to time.

Point is - such intervention can be seen as "favoritism", and if it ends up being true in the sense that some get the favoritism, while others, the criteria for how one favors one player over the other becomes an issue. Having the lesser "Kill party results" on the tables results in far fewer fatalities not only for the player characters, but for the NPC's as well.

Not that I know the answer, but how many ships sail into port and safely arrive in other ports as contrasted against ships disappearing without knowledge of how or where they disappeared? Or in perhaps a different way of looking at things, when was the last "Titanic" event in recent memory? That isn't to say that lesser ships don't disappear with some frequency - but using the sailing analogy a little further here, if such events occurred with the same frequency for larger ships as for smaller ships or boats, might not the public have some major fears with trusting any kind of ship based travel on the seas?

Navigation for the lesser craft in Traveller poses the same threats as it does for larger craft in Traveller. Imagine a Traveller Universe where instead of getting penalties for Jump distance to the astrogation roll, the penalties were all Ship's mass based? Maybe the jump calculations favor the smaller jump bubble as being easier than a larger jump bubble?

IMTU - precipitating OUT of Jump space unexpectedly causes turbulence that increases the potential for Jump Space Sickness, stresses the hull unexpectedly, and is generally a "bad thing". As I don't use normal space obstructions hindering a jump, but only masses at the entry and exit points of Jump Space where it borders the Normal space - it gives players a reason to avoid cutting it TOO fine and on their own, trying to insure that where ever they exit from due to variable time in jump space - they still have some travelling to do within normal space. Being 1 AU distant from your intended jump exit point means that destroyers or Patrol cruisers can't simply hover in geosynchronous orbits and rush into action like a cop spotting a speeder. After all, it seems that only in near planetary orbits will ships enter or exit from jump space.

When you get right down to it? The rules for Jump Shadows and Jump Masking end up doing what precisely as compared/contrasted against Classic Traveller's original rules? Yup...

*Add transit time in normal space to justify potentials of adventure in space*


Jump accuracy and jump shadows and jump masking are (in my eyes) all means to the same end.

Maybe someday, I'll run a GURPS TRAVELLER campaign via Fantasy Grounds 2 that uses SECTOR FLEET material and have a run at a military based campaign where the player characters command a Naval Destroyer. One would think that such a campaign would be overkill when it comes to handling day to day events in a subsector right? After all, the Third Imperium is in a period of peace and nothing can seriously challenge a Destroyer where it comes to civilian craft right?

What I find a shame in all of this? Fantasy Grounds 2 is a Virtual Table Top software package. It currently supports commercial sales of both BRP role playing rules (Call of Cthulhu mostly) and D&D. Some snazzy people have written a support package for use with GURPS. If Mongoose or Marc Miller were smart, they'd tap into the market of frustrated Traveller players who can't find local games, and offer a commercially available MgT package for use with FG2. The fun would be the ability to run a campaign with people all over the world (assuming they can agree on a specific time frame to get together!).

Someday.

 

[Hal]

Ok, after doing more research into old material across the spectrum (Classic Traveller's JTAS 24, Megatraveller, etc)

I've come to this conclusion about jump emergence scatter

Initial statement in JTAS24 was that a jump was only as accurate as 1 part in 10 billion. A one parsec jump could be no more accurate than within 3,000 km. Paraphrasing the other part of the article, it states that this accuracy could degrade by as much as a 10 fold due to other factors. To wit:

"Error in arrival location is also affected by the quality of the drive tuning, and by the accuracy of the computer controlling the jump. These factors can increase the jump error by a factor of 10."

Now the question that comes to my mind is this:

Drive Tuning is one factor
Accuracy of the computer is another factor

Is the 10 fold increase PER factor, or do the combined issues result in a final 10 fold increase?

Example:

Base accuracy is at best 3,000 kilometers for a 1 parsec jump.

If the Drive is perfectly tuned, and the computer is perfectly accurate (what ever that means!), then the jump scatter will be at worst - 3,000 km.

If it takes the worst of both tuning AND accuracy of computer to get a 10 fold increase in scatter, then the worst is 30,000 km

IF tuning is 100% the best it can be, but the computer accuracy is not, then worst case is again, 30,000 km.

However, if Tuning is at its worst and still allows the jump drive to engage, accuracy is also minimal - then the worst case scenario would be 300,000 km.

Looking at the task rules for Navigation - nothing bad happens if the navigator misses his skill roll by 1 or less. In fact? If he flubs it critically (worst roll possible) nothing bad seems to happen other than he doesn't get a course generated. Looking at the Jump Mishap rules for MegaTraveller, only if the ENGINEER flubs his engage jump drive roll, will there be the potential of scatter upon exit from jump space.

But what if...

Task roll for Navigator counts as the "computer accuracy" portion of the original Jtas 24 article?

Success by a large margin means complete computer accuracy. Barely succeeding means worst margin of success for a x10 increase in scatter.

Barely failing means what then? No course generated? Someone who thinks they're right, but will exit at a worse distance than normal success might generate? Possibly.

Drive Tuning: if maintenance is not done, that likely affects drive tuning. If engaging the drive improperly - that might result in improper drive tuning. If using impure fuel, that might affect drive tuning.

So, same thing with the engineer right? Barely succeeding means up to a 10 fold increase in accuracy issues, Succeeding with a finely tuned, perfectly engaged jump drive should drive down the accuracy issues.

Trying to envision all of this?

Pilot has to make the ship physically adhere to the planned course set by the navigator. A perfect flight plan is only perfect if the pilot executes it perfectly.

Once the ship arrives at the correct location to engage the drive, at the correct time, the engineer has to do his job, or cause problems.

My suggested set of rules would require the following:

Course accuracy is a x10 multiplier and engineering accuracy is a x10 factor.

Course accuracy is at best, the accuracy of the navigator, and is further degraded by the pilot. If the Navigator is 100% accurate, the pilot is 70% accurate, then the course accuracy is 70% accurate. If the Navigator was 70% accurate and the Pilot was 100% accurate in executing his course instructions then Course Accuracy is 70%. If however, the pilot was only 70% accurate in executing a 70% accurate navigation solution, the overall accuracy for navigation becomes 49% accurate.

Engineering accuracy is based on only the engineer being accurate. However, poorly maintained drives might provide an upper limit to how accurate the drive can be much like the Navigator determines the upper limit of how accurate the course accuracy can be.

All this is based on a SUCCESSFUL process where a successful jump is accurate between 3,000 km and 300,000 km.

(10x for the course accuracy times 10x for drive accuracy x 3,000 km best case accuracy)

Does this make sense? If so, then perhaps we can come up with specific "house rules" for ANY game system.

1) Roll against Navigator Skill, degree of success determines the multiplier rate of between x1 and x10 range of scatter

2) roll against Pilot skill to get the best use of the Navigation skill, further modifying the x1 to x10 range possible.

3) determine best accuracy the drive is capable of producing as a result of its maintenance value. Fully maintained, recently undergone its shipyard maintenance activity - Best possible is 100% for a x1 modifier. As the drive degrades, it drops to a x2, x3, x4 level until it reaches a x10 rating.

4) Engineer skill roll determines just how much accuracy he can coax out of the engine when the button to engage is pressed. This in turn determines the FINAL accuracy possible for the engine.

This gives ALL player characters or Non-player characters a role to play and have an impact on the ship's activities.

For those who don't care or want to bother, a simple single roll against the average skill level of all involved can handle the final details.

Thoughts?

 

[Hal]

To all of you here, I'd like to take a moment to thank your participation in this thread and responding as you have. I really appreciated it.

Due to issues with a Moderator, I have decided to remove myself from this fellowship after 15 years of participation. I've let that particular moderator know WHY I'm leaving.

You however, deserve a special thanks for your behavior and your inclusion of myself in this fellowship. I shall miss it. It was educational to say the least.

Be in good health and good luck.

Hal

 

[ShawnDriscoll]

when I look at the book for rules regarding jumping and being somewhat inaccurate, I don't find the specific rules. I must not be looking at the right place.

If I remember, Mongoose uses the 1D X 1D parsecs in a random direction rule. I tend to use the 1D parsecs in a 1D direction rule that I read years ago from something.