In another discussion, I was reminded that MgT2e generally makes jump drives very much less accurate that they were previously. Though there is a Mg JTAS article that retains their relative precision and The World Builder's Handbook as a third way of calculating accuracy that is somewhere in between.
In Classic Traveller, this wasn't a topic that was discussed in any of the rulebooks that I am aware of. It's not an issue raised in Bk2 or Bk5. You just arrived. In JTAS 24, Marc Miller asserted that one of the benefits of Jump drive was its controllability, claiming it was accurate to within 1 part per 10 billion. Claiming that that jumps of a parsec or so were normally accurate to within 3000 meters, though bad astrogation could increase that error tenfold.
The other CT data point I'm aware of is that both Tarsus and Beltstrike discuss jumping to the 100D limit of a large object with the intention of being as close as possible to a object orbiting the body whose limit applies. In the case of Beltstrike, this was arriving close to a moon around a gas giant and in the case of Tarsus, it was being as close as possible to the world of Tarsus, which was inside the sun's 100D limit. There it claims that commercial ships rarely make the kind of mistake that results in missing this optimum point, but it sometimes happens in private vessels. The rules there state that hitting this target (closest point at the 100D limit to the orbiting satellite) happens unless you roll 10+ on 2D6 with a -1 DM per skill level of the ship's navigator. At that point you could get pretty far off from the satellite, though not from the gas giant/sun.
I don't remember anything different being said in MegaTraveller. New Era was basically the same except with some additional complications related to accurately vectoring yourself at the destination since that edition used reaction drives instead of M-Drives, so the vector affected fuel usage.
I never bothered to learn the rules to T4. In T5, you can't fail to arrive at the 100D limit of a known celestial object (without a misjump), but if you try to emerge in open space for whatever reason, then there are scatter rules.
Which brings us to Mongoose 2e.
JTAS #3 has two articles "Jump Space Operations" and "Jump Point to Port". The first article basically uses Marc's 3000m accuracy, but makes the variance on longer jumps a little bit more than in the original article. The Jump Point to Port article does not talk about accuracy, but it does mention that Class A & B starports normally have designated emergence zones. That presumes some reasonable accuracy to jump arrivals. The exact quote being:
"Orbital space around a world with a Class A or B starport tends to be busy and subject to a strict set of traffic control guidelines. Often a busy port will post guidelines at neighbouring starports, indicating favoured emergence points for ships from that system. If pre-prepared jump solutions are available, these use standard emergence zones. A policy of giving priority to vessels emerging from jump at these points encourages traffic to behave in a manner that is easier for the starport authority to manage."
Then there is the World Builder's Handbook. It is talking about jumping to celestial objects in "empty" hexes. The variance there is 0 to 4 D6 diameters unless you make your astrogation roll exactly (0 effect), then it can be really inaccurate (up to 600D!).
Lastly, the rules in the Traveller's Companion. Again, these are mostly pretty accurate. 0-4 D6 diameters makes up a substantial majority of results. But bad results are more likely than in the World Builder's Handbook, albeit less extreme (120D is the worst variance). It also introduces a new concept "bad jumps" that doesn't previously exist.
I don't know that this makes much difference overall. But I find it interesting that jump seems to be steadily getting less accurate and more dangerous in newer editions. In CT, unless you were trying to do something funky like predict your arrival near to a satellite or jumping with some sort of malfeasance involved (in a gravity well, bad fuel, shorthanded), you jumped safely and accurately. Now you are unlikely to actually be accurate and simple bad dice can result in some pretty wildly inaccurate normal jumps.
In Classic Traveller, this wasn't a topic that was discussed in any of the rulebooks that I am aware of. It's not an issue raised in Bk2 or Bk5. You just arrived. In JTAS 24, Marc Miller asserted that one of the benefits of Jump drive was its controllability, claiming it was accurate to within 1 part per 10 billion. Claiming that that jumps of a parsec or so were normally accurate to within 3000 meters, though bad astrogation could increase that error tenfold.
The other CT data point I'm aware of is that both Tarsus and Beltstrike discuss jumping to the 100D limit of a large object with the intention of being as close as possible to a object orbiting the body whose limit applies. In the case of Beltstrike, this was arriving close to a moon around a gas giant and in the case of Tarsus, it was being as close as possible to the world of Tarsus, which was inside the sun's 100D limit. There it claims that commercial ships rarely make the kind of mistake that results in missing this optimum point, but it sometimes happens in private vessels. The rules there state that hitting this target (closest point at the 100D limit to the orbiting satellite) happens unless you roll 10+ on 2D6 with a -1 DM per skill level of the ship's navigator. At that point you could get pretty far off from the satellite, though not from the gas giant/sun.
I don't remember anything different being said in MegaTraveller. New Era was basically the same except with some additional complications related to accurately vectoring yourself at the destination since that edition used reaction drives instead of M-Drives, so the vector affected fuel usage.
I never bothered to learn the rules to T4. In T5, you can't fail to arrive at the 100D limit of a known celestial object (without a misjump), but if you try to emerge in open space for whatever reason, then there are scatter rules.
Which brings us to Mongoose 2e.
JTAS #3 has two articles "Jump Space Operations" and "Jump Point to Port". The first article basically uses Marc's 3000m accuracy, but makes the variance on longer jumps a little bit more than in the original article. The Jump Point to Port article does not talk about accuracy, but it does mention that Class A & B starports normally have designated emergence zones. That presumes some reasonable accuracy to jump arrivals. The exact quote being:
"Orbital space around a world with a Class A or B starport tends to be busy and subject to a strict set of traffic control guidelines. Often a busy port will post guidelines at neighbouring starports, indicating favoured emergence points for ships from that system. If pre-prepared jump solutions are available, these use standard emergence zones. A policy of giving priority to vessels emerging from jump at these points encourages traffic to behave in a manner that is easier for the starport authority to manage."
Then there is the World Builder's Handbook. It is talking about jumping to celestial objects in "empty" hexes. The variance there is 0 to 4 D6 diameters unless you make your astrogation roll exactly (0 effect), then it can be really inaccurate (up to 600D!).
Lastly, the rules in the Traveller's Companion. Again, these are mostly pretty accurate. 0-4 D6 diameters makes up a substantial majority of results. But bad results are more likely than in the World Builder's Handbook, albeit less extreme (120D is the worst variance). It also introduces a new concept "bad jumps" that doesn't previously exist.
I don't know that this makes much difference overall. But I find it interesting that jump seems to be steadily getting less accurate and more dangerous in newer editions. In CT, unless you were trying to do something funky like predict your arrival near to a satellite or jumping with some sort of malfeasance involved (in a gravity well, bad fuel, shorthanded), you jumped safely and accurately. Now you are unlikely to actually be accurate and simple bad dice can result in some pretty wildly inaccurate normal jumps.
