MISJUMPS: all rules systems listed

[Hal]

Hello Folks,
It can be a touch difficult to discuss the causes of misjumps in the various rules sets from Traveller - starting with Classic Traveller on up to T5. I propose that people who have the various rules sets, look for how ships accidentally end up misjumping (after all, no one wants to deliberately misjump right? RRrrriiiiiight).

Ok, starting with the classic Traveller rules set. I suggest that if anyone contributes to this thread, that they identify which rules set they are discussing by stating CT, MT, TNE, T4, T5, T20, MgT, GT, etc...

The whole point of this thread, is to discuss what the odds are of any given game system having a ship misjump. At least this way, people can have all of the facts at their finger-tips when they look at the game rules for which they run their campaign(s).

Hal

 

[Hal]

So, starting off with Classic Traveller, using THE TRAVELLER BOOK, page 51, we have:

+1 using unrefined fuel on ships not equipped to do so.
+5 Jumping within 100 diameters of a world.
+15 jumping within 10 diameters of a world.

Rolls of 13+ result in misjump.
Rolls of 16+ result in destruction.

Page 55 adds to the list by indicating the following:

Unrefined fuel: +1
Scout Ship: -2
Naval Ship: -1

Consequently, in a classic Traveller universe, the odds of a misjump occurring using refined fuel, 101+ diameters away from any world (and if using SCOUTS, any stars as well), there is ZERO chance of a misjump per THE TRAVELLER BOOK. Otherwise, misjumps will occur 100% of the time for commercial ships within 10 diameters of any given world, or on an 8+ while between 10 and 100 diameters (roughly 42% of the time) or when using unrefined fuel within 100 diameters but greater than 10 diameters - something along the lines of 58%.

I will verify whether or not the LBB confirm this value or not...

(NOTE: I verified that the LBB also uses the same statistics/rules as THE TRAVELLER BOOK)

 

[Hal]

GURPS TRAVELLER:

GURPS Traveller rules for misjumps is a little bit different than might be expected in comparison with any of the other Traveller rules. For a ship to enter jump-space, three rolls are involved, and potentially more.

Initially, there is the Pilot roll. Any crit failure with this roll, merely results in no jump. Any regular failure results in no jump. This is the least damaging skill roll resulting in a misjump possibility.

Then we have the astrogator roll. This roll, can result in a mishap, but only if the second roll against the astrogator roll fails again. So, the first roll versus Astrogator has to be a crit failure, and then the second roll has to be an actual failure - before the astrogator's mishaps can occur. For an Astrogator with a skill of 12 (deemed to be Professional level in GURPS), there is a roughly 2% chance of critical failure, and a further 26% chance of a secondary failure occurring immediately after a crit failure. Note too, that if the ship is within a given range of a planet, the skill rolls themselves are penalized by either a -4 (if within 100 diameters), -8 if within 50 diameters, and -12 if within 10 diameters of a body. This is further penalized by an additional -2 if using unrefined fuel. If an astrogation mishap occurs, there is only a 1 in 6 chance that it will be a misjump into deep space between the world of embarkation and the destination world. All other astrogation mishaps result in being somewhere in the destination system, but not where was originally plotted.

Last but not least, we have the Mechanic error (aka, Engineer's error). Again, we roll against the Engineer's skill roll, plus any penalties due to fuel type, distance from world being jumped from, etc). Then, if that roll results in a crit failure (generally 2% of the time), we're looking at another roughly 26% chance of failure after getting a crit failure on the first roll. This results rolling against a mishap table, where the results are:

No Jump
Normal Jump, but exit is in the same place as originally started from
Misdirected jump (see table on page 120 in GURPS TRAVELLER book)

Here, the odds of a misjump are markedly smaller than the odds of a misjump in CT. I'm a touch fatigued right now, and don't want to attempt to do the math, but in a nutshell, it looks like the odds of a Misjump for a skill 12 individual would be about .0052 (I hope I'm not screwing this up!). However, because there are three sets of rolls being made, two sets of rolls of which can result in what appears to be a Misjump - it appears that the odds will be slightly higher.

 

[Carlobrand]

MegaTraveller: no chance of misjump on a "safe" jump, defined as a jump from more than 100 diameters outside of any gravity source (including the local star), in a ship that is up-to-date with maintenance, with refined fuel (or a fuel purification system). No roll is required. (Imperial Encyclopedia, P. 92).

Otherwise it's a skill roll, therefore dependent on your Engineering skill and education, with the needed roll varying from Routine (7+ for a jump outside 100 diameters in a poorly maintained ship or one using unrefined fuel, bonus for skill and 1/5 education rating, round down) to Difficult (11+ for a jump within 100 diameters, plus bonuses) to Formidable (15+ for a jump within 100 diameters, plus bonuses). A natural roll of 2 is a fumble and fails irrespective of bonuses.

An attempt is Hazardous (affects the consequence of a missed roll but not the odds of missing) if it occurs from within 100 diameters or with unrefined fuel; there doesn't seem to be a cumulative effect for using unrefined fuel while within 100 diameters.

An attempt that is NOT hazardous (a roll from outside 100 diameters with refined fuel, but your drives are overdue for maintenance) simply results in no jump unless a fumble is rolled, in which case it is a routine (2D6) mishap. A hazardous attempt that fails by only 1 point likewise results in no jump, but a hazardous roll that fails by 2 or more results in a routine (2d6) mishap; a hazardous roll that ends in a fumble results in a 3d6 mishap (i.e. much higher odds of a serious outcome).

If you end up in a mishap, you roll the indicated dice: 2d6 for a routine mishap, 3d6 for the nasty one. The results are:

reroll on a 2

superficial mishap (the ship is in jumpspace 5 to 9 days instead of the usual 6 to 8 but emerges on target) on 3 to 6 (~39% at 2d6; ~9% at 3d6)

minor mishap (the ship is in jumpspace 5 to 9 days instead of the usual 6 to 8, and it is off target by 1d6 x 8 hours flight time) on a 7 to 10 (~50% at 2d6; ~41% at 3d6)

major mishap (the ship is in jumpspace 5 to 9 days instead of the usual 6 to 8, and it emerges at a random point in space: 1d6 for direction, 1d6 dice distance in parsecs) on an 11 to 14 (~8% at 2d6; ~41% at 3d6)

destruction (self-explanatory) on a 15+ (not possible on 2d6; ~9% at 3d6)

End result is that most of the time your wild chances end in a superficial to minor mishap if they fail, but there's a little under a 10% chance of a failure ending up in a full-on misjump or destruction.

 

[Hal]

Thank you Carlobrand. Somewhere along the way, I will dig into my T4 CD (when it arrives, as I just ordered it recently) and see what I can find there. I probably could look at the T4 book that came with my T5 CD, but it will have to wait at least three days as my home life goes into overdrive