Condottiere
Emperor Mongoose
The pragmatic solution would a a semi-randomized exit table of events; the astrogator would be aware of the result, which is why it would be diced for when planning where the transition takes place.
Jump Shadowing/Masking
- Thread starter mancerbear
- Start date
Reynard
Emperor Mongoose
"What's the solution? I guess the practical answer is to change the setting so that jump drives can't be obstructed by anything except the specific 100D limit of their target"
Which is exactly how the majority of Traveller games are played! Ship always exits jump space at the intended destination, barring misjumps, at the 100D mark without any interference from any other stellar body. For a normal adventure, there is no such thing as shadows/masking unless the referee really, really wants to use it for plot device. No need to change the setting because your solution is already there.
Which is exactly how the majority of Traveller games are played! Ship always exits jump space at the intended destination, barring misjumps, at the 100D mark without any interference from any other stellar body. For a normal adventure, there is no such thing as shadows/masking unless the referee really, really wants to use it for plot device. No need to change the setting because your solution is already there.
Reynard said:
Which begs the question - if it's so practically difficult to actually incorporate the effect of jump masking/shadowing into games, then what's the point of mentioning it in the rules in the first place? And it has caused a lot of arguments over the years too. It just seems like bad design to me.
Sigtrygg
Emperor Mongoose
It was never mentioned in the original rules at all.
One sentence in MWM's Jumpspace article is taken out of context to imply that a ship can be pulled out of jump space if to gets too close to the 100D limit of an object, despite the fact that the article clearly states that gravitational effects (or however you want to handwave them) only affect the jump process when the ship is trying to enter or exit jump space.
One sentence in MWM's Jumpspace article is taken out of context to imply that a ship can be pulled out of jump space if to gets too close to the 100D limit of an object, despite the fact that the article clearly states that gravitational effects (or however you want to handwave them) only affect the jump process when the ship is trying to enter or exit jump space.
Reynard
Emperor Mongoose
The majority of the time, it's solely been focused on the destination world. You seldom hear any mention of the star interfering with a jump. I'll say again, it was MegaTraveller and T5, maybe others, that go in depth as part of a campaign to introduce masking and shadowing in detail. I really don't mind Mongoose made mention of the star's shadow effect in Scouts (and, as far as I remember, it's the only place referencing shadow) but there is little to no detail game wise such as the actual distance to calculate time for a ship to reach final destination rather than an abstract location showing not much more than positions of planets within star shadow and in relation to each other. I add the property when using the expanded world creation system but don't really bother using it. It's referee eye candy dressing. Look for an older edition for actual system body placement and sizes of stars and gas giants Maybe a revised Scouts book will address it.
mancerbear
Mongoose
GURPS Traveller uses Jump Masking, and can be found in the supplements GURPS Starships, and GURPS Far Trader. I adapted their technique for my Traveller game, primarily just converting the 3D roll of GURPS to a 2D roll of Traveller, and everything else works out just fine. Essentially, the largest stars never mask destination worlds as they orbit a significant distance away. Small stars tend to always mask target worlds, as they need to orbit close to be habitable. Medium stars sometimes mask the targe world. It's not hard to adapt at all if you have 30 minutes spare time and willing to put in the work.
Mind, it does take a touch of common sense too. If I'm going to jump to a planet in the first orbit around a giant star, then it's going to be masked regardless, more so if it's behind the primary, and if I'm jumping to a planet in the Kuiper belt of a red dwarf it's not going to be masked at all... UNLESS it's behind it's primary from your point of view.
I would like the new MgT Scouts book to address it actually, so there's a unified rule to use, and that I'm not house ruling it for my games.
Mind, it does take a touch of common sense too. If I'm going to jump to a planet in the first orbit around a giant star, then it's going to be masked regardless, more so if it's behind the primary, and if I'm jumping to a planet in the Kuiper belt of a red dwarf it's not going to be masked at all... UNLESS it's behind it's primary from your point of view.
I would like the new MgT Scouts book to address it actually, so there's a unified rule to use, and that I'm not house ruling it for my games.
ShawnDriscoll
Cosmic Mongoose
What more rules do you need other than 100D?mancerbear said:
Sigtrygg said:
From JTAS 24:
"The perturbing effects of gravity preclude a ship from exiting jump space within the same distance. When ships are directed to exit jump space within a gravity field, they are precipitated out of jump space at the edge of the field instead."
and:
"On the other hand, there seems to be a built-in safety feature for ships trying to leave jump space within 100 diameters of a world. Ships naturally precipitate out of jump as they near the 100 diameter limit."
I don't think there's not much to be misinterpreted there. if you're in jump space and you're trying to exit within 100D of a world, you won't be able to do it - you'll be naturally pulled out of jump near (or at) the 100D limit.
And I this is explicitly stated in T5 too:
T5, p321: "The J-Drive interacts with gravity sources: a ship in jump is automatically precipitated out of jumpspace when its course brings it within about 100D of a gravity source. "
Elsewhere (T5, p371), T5 says that the ship will exit jump at a point on the 100D sphere surrounding an object.
Also (T5, p372): "If the Exit Point is within a 100 Diameter sphere, the ship automatically exits at a point where the straight line course intersects that 100D sphere."
So between all that, I think it's pretty clear that Marc intends that the intersection of a ship's "jump line" with a 100D limit will pull the ship out of jump (in a non-harmful way, it seems).
nats
Banded Mongoose
fusor said:
Its MEANT to represent the gravity of the object that is pulling the ship out of jump - which is directly related to its mass. But that would be far too complex to calulate for a role playing game so it is abstracted as 100 diameters. Simple, no need to complicate matters any further than that.
Ships dont have any substantial inherent gravity and I assume could detect a jump field easily enough from distance. So jump shadowing could be possible but how you would assess where the jumping ship is going with any accuracy is the question. I don't know about jump masking though - you either have a jump field to be very detectable or you don't. Space is very empty a strong electrical/hydrogen impulse would be easily detectable from extreme ranges. There is no way to be reasonably stealthy in space unless you stay completely cold and non-emitting which effectively means dead and inactive - not very productive to doing anything much.
I would expect any ship emerging from jump space would be lit up like a Christmas tree for several minutes to anyone inside the system. The trick would be losing any tracking once you emerged, presumably by starting on a heading and then going dead for several hours and drifting. Elite Dangerous has quite a good stealth mechanic concept of heat detection and signature reduction shame they haven't utilised it to any degree though.
nats said:
How is 100D calculated?
If you have the planet UWP there, you look at the size code (which is diameter in 1000s of miles), multiply it by 100, and that's how many thousands of miles from the planet the 100D limit is. OK, not so bad.
But for a star? Then you have to dig up the radius of the star, convert it to AU, multiply it by 200 (the radius of the 100D sphere is equal to 100 diameters from the centre of the object), and that's where the 100D limit is. That's more fiddly, especially since usually the radius of the star isn't given.
Or the designer could provide a table containing the size of object in one column, and 100D in the other column. Look at that and then pick the one closest to the object you're dealing with - no calculation required.
But if you can do that and if gravity was really the limiter, then they could also provide a table for that. The object's mass would be in one column, and the "100D" where gravity reaches whatever the limiting value is the other column. Again, no calculation involved.
So it's not necessarily more complicated at all. It just requires the designer to do the work beforehand to make the table, then the GM can just look up the mass of the star or planet. It's not that different to how it's done in 2300AD where they give you the stutterwarp limits.
Condottiere
Emperor Mongoose
I'm sure at some point in the future there will be a complete chart mapping out the Spinward Marches that will be turned into an app for easy consultation, that would allow players to draw a line between the entry point and nearest localization of the desired exit point.
In the meantime, you could get the same type of mechanism by rolling dice.
In the meantime, you could get the same type of mechanism by rolling dice.
Sigtrygg
Emperor Mongoose
In both of those sentences it is explicit that the ship has to be trying to leave jump space for the 100D precipitation limit to kick in.
Therefore once you are in jump space you can ignore anything in the real world, the jump line is purely imaginary - you are in a different universe. You could plot a jump line that goes through a star, but unless you are trying to exit at the star it has no effect on you. However if you are trying to exit at a world that is inside the star's 100D limit you may precipitate at the star's 100D limit or the world's 100D limit, depending on if the entire 100D limit of the world is inside the 100D limit of the star.
The GURPS authors took "Ships naturally precipitate out of jump as they near the 100 diameter limit" out of context and had it mean that if your imaginary jump line passes within 100D of an object during your time in jump you precipitate out at the objects 100D limit despite the fact that it clearly states you have to be trying to leave jump space for it to have any effect.
I know that MWM has now canonised the jump line theory in T5, as well as being able to park a larger ship at any point on the jump line and force precipitation.
Under the paradigm of the original article this was not the case, and the new interpretation has some pretty big setting implications.
Sigtrygg said:
All of this is why there's been 30-odd years of argument around the topic
. The phrasing (and peoples' interpretations) is ambiguous enough to fuel that. Yeah, well, that's just plain stupid IMO. First because there's no way a ship is going to be in exactly the right spot to block another ship's jumpline, and second because it just adds even more complication to something that's complicated enough for no real gain (but then this is T5 we're talking about, which seems to add complexity to everything for its own sake). And then what... a ship could spool out a wire that's 1000 km long and that has a 100D of 100,000 km? That's crazy talk.
Reynard
Emperor Mongoose
Those 40 years saw a lot of different people making interpretations and probably not everyone read every possible interpretation before them so, like most languages, there are exceptions to the rules. Movie and tv shows went through this all the time until someone created the first canon 'bible' saying what exactly happens and things are added to it by a committee. Mongoose has been doing that over the years but they also rely on a LOT of fan material. You see it in this forum constantly when people say they know something they heard is the Truth.
Yep. I have been watching this debate for decades now, and meanwhile it feels a bit like in the Groundhog Day movie, an endless repetition. In the end one can either accept the rules as they are ("It's Traveller's alternate universe ...") or replace them with other rules one likes better ("In my Traveller universe ..."), but the discussion with the hope that there will be a final result everyone can and will agree on would probably go on until the guys with the straitjackets appear on the scene. And the 100D limit is not the only topic of that kind, there are also the economy of piracy, stealth in space, Aslan footwear ... :shock:fusor said:All of this is why there's been 30-odd years of argument around the topic
