Astrogation needs help

Gravity wells wouldn't be perfect spheres either, so if jump lines looked curved inside hyperspace, they appear to be straight when viewed from our reality.

4, Jumpspace would be five dimensions expressed in two dimensions, which would make the jump bubble a pimple being squeezed out of the epidermis of hyperspace.

Jumpspace (or a set of Jumpspaces) could be more than 5 dimensions: Our 4 dimensions plus an additional dimensional trajectory within an N-space of any number of dimensions. Which would help explain the results of some misjumps.

I think that jumpspace would be five dimensions, since it seems easiest to access.

1. Einsteinian deadstop, would be by necessity, relative to the local gravity wells, since it would look like you're not moving.
Stars and planets are constantly accelerating, they follow "circular" paths - actually much more complicated. If you are "at rest" relative to the motion of the system you are in then you have to be orbiting at the same rate, which means you are not at rest. The whole point of relativity really...
2. I don't know about GURPS, but when I enquired about bending the jump line, I was told it's straight; so you can't bypass gravity wells en route.
Which is inherently silly since nothing is in a "straight line", made more complicated by everything moving while you are in jump space.
3. I vaguely recall the timing being about the publication of Mongoose Second, since then I would be interested in that sort of thing.
Jump masking etc was a GURPS invention - it should never have been retconned into the setting.
4, Jumpspace would be five dimensions expressed in two dimensions, which would make the jump bubble a pimple being squeezed out of the epidermis of hyperspace.
There are a lot more Jumpspace dimensions than just five...

Regardless of whether jump masking makes any sense, it is a bad idea because it is basically unplayable. No referee is going to know where various stars and planets are relative to each other to decide you come out of jump space via precipitation instead arriving at the normal locale. It might be vaguely useful for local color in explaining a "bad jump" or other high variance result on the chart in the companion table, but that's retroactive explanation. That isn't particularly interesting or helpful.

The only way it actually affects gameplay is micro jumping. And even then, only if the ref has actually spelled out where planets are relative to each other at the moment. Which is pretty unlikely.

1. Since jumpspace is basically magic, you have to rely on the game mechanics as explained by the author(s).

2. And I take it, five dimensions expressed on a two dimensional hex paper makes a transition a straight line.

3. I don't really recall how Classic explained the hundred diameters, though the intent was to permit random encounters, so masking and precipitation would be natural factors to consider in jumping.

4. Going by the Honorverse, higher orders of existence permit faster transitions, which since time seems fixed, could be facilitated by adding an additional dimension to compress space, though I have no actual idea whether that is how it's supposed to work.

5. Apparently, once you move to more faster means of transition, time gets compressed, and you need more leeway, so perhaps there it's more of a question of time travel or manipulation.

6. And this may all get answered by Starship Operators Manual.

7. And yes, charting out a course is clunky, doesn't make much sense, and unless someone programmes an application, remains abstract to the point that a jump factor one free trader could transition seven light years from the far edge of one hex to the far edge of the neighbouring hex.

Regardless of whether jump masking makes any sense, it is a bad idea because it is basically unplayable. No referee is going to know where various stars and planets are relative to each other to decide you come out of jump space via precipitation instead arriving at the normal locale.
"Jump masking" is essentially how I think most people play the game - they might not do it consistently, but generally the assumption is that ships emerge from jump at or beyond 100 diameters from a world. Stars usually are not taken into account in this - often 100 diameters from the star would result in some inner planets being "masked" by the star's gravity well. This is maybe a problem from a consistency perspective, but not such a big one, since it does necessarily even change much in terms of gameplay - unless it does (i.e. if the referee needs a plot reason to make in-system travel more important)

So there is normally only one question to which the referee needs an answer, and that is whether the star is masking the destination planet. Other planets might theoretically precipitate a ship out of jump space, but the odds of this are very slim that this would happen even if you just enter the system randomly. Space is big. Really big. Even the 100D of Jupiter sized planets will still leave plenty of room to get around them, and by plenty of room we are talking about needles and haystacks. Furthermore, the planets are in predictable orbits, they don't just move randomly around. The astrogator will know where they are, unless exploring unexplored space, and plot the jump so as to be precipitated at the desired location, and not intersect any gravity wells: we don't need to go into details in-game, but just assume the astrogator is doing this.

So to do this right, the referee just needs to know, or to decide, if the target planet is masked. If it is, the ship will emerge at 100Ds from the star, if it is not 100Ds from the destination planet, and maybe add some distances if the astrogation roll is not that good. The referee will know if the planet is masked if the whole star system has been created by multiplying the star's diameter by 100 and checking the planet's orbital distance; if not, I would say the referee should just decide the matter and record that information for future reference, because if, at a future date, information about secondary bodies in the system is needed, s/he will have to ensure that the type of star, and orbits of planets are consistent with the earlier decision to mask or not mask.

Why is masking important and why have it at all? In gameplay terms it forces ships to emerge at least a certain distance from their destinations. This makes piracy possible. Consistent application of the principle makes it even more interesting, as certain places - such as near gas giants, or in systems where stars mask certain worlds, there is even more possibility for deep space interceptions since these 100Ds have the potential to be pretty big.

It is also important for not breaking the game universe. If you could jump right into a planet's orbit, you could just jump a fleet right next to a world and basically launch weapons salvos or troops with no need to engage system defenses. Also, kamikaze attacks by space ships emerging from jumps travelling at relativistic speeds smashing into planets become trivially easy. This unravels all the canon built up around system defenses and naval doctrine.

So in short, it is not hard to implement, has interesting gameplay implications and basically breaks the universe if not implemented.

The 100 D limit on emergence is how most people play the game, including worlds being in the shadow of the star. So if that's all you mean when you say Jump Masking, yes, that's true and easy to implement. But the full jump masking rules, which were being discussed in the preceding posts (it is why they are talking about curves and straight lines in jump space), argue that jump travel can't cross any large masses without precipitation. So, for instance, you can't micro jump from Earth to Jupiter if the sun is between them at the moment. It is not just where you come out, but the entire path of your travel. So if you jump 4 along a main, your astrogator is technically making sure your path never clips any stars or planets along the route or your jump is cut short.

That's unplayable. I guess if you were playing in the Earth system, you could have a physical or digital orrery to tell whether your path is clear or not. But for any other system, it is not a thing that any referee is going to know. And that is doubly true of interstellar travel.

By strict interpretation jump masking means a ship can be pulled out of jump in the middle of an empty hex by an errant asteroid, which for most ships of Charted Space is a death sentence for all aboard. I don't consider that acceptable, any more than the sociopathically high loss rate for low berths is. (Just because Dumarest did it that way is no excuse.)

It's worse than you think.

A ship in jump can be pulled out of jump bay any sufficiently massive object that intersects the jump line at any time during the week.

That means you need a "where everything is now to a week in the future" model, 4 years out of date sensor readings will not do.

And what if someone maneuvers a

I think we have another answer regarding the value of an astrogator: failure of the jump plot increases the likelihood of a jump precipitation (which the Referee would then have to plan out). I don’t recall any misjump tables having jump precipitation as an event.

I have been fascinated by “empty hexes” since day one, and the recent World Builders Guide makes an “unscheduled jump bubble displacement” in an empty hex because of a rogue planet or brown dwarf even more likely/explainable then before.

I think I may clarify my jump notes into a draft JTAS article.

By strict interpretation jump masking means a ship can be pulled out of jump in the middle of an empty hex by an errant asteroid, which for most ships of Charted Space is a death sentence for all aboard. I don't consider that acceptable, any more than the sociopathically high loss rate for low berths is. (Just because Dumarest did it that way is no excuse.)
Yeah. It is one thing for ships to basically illegally ship people in cattle freezers like in Dumarest. It is a whole other thing to have it be a standard transport mode used on legitimate transport lines.

The 100 D limit on emergence is how most people play the game, including worlds being in the shadow of the star. So if that's all you mean when you say Jump Masking, yes, that's true and easy to implement. But the full jump masking rules, which were being discussed in the preceding posts (it is why they are talking about curves and straight lines in jump space), argue that jump travel can't cross any large masses without precipitation. So, for instance, you can't micro jump from Earth to Jupiter if the sun is between them at the moment. It is not just where you come out, but the entire path of your travel. So if you jump 4 along a main, your astrogator is technically making sure your path never clips any stars or planets along the route or your jump is cut short.

That's unplayable. I guess if you were playing in the Earth system, you could have a physical or digital orrery to tell whether your path is clear or not. But for any other system, it is not a thing that any referee is going to know. And that is doubly true of interstellar travel.
Yes, I understand this. I just don't understand why it is unplayable, or in any other way undesirable. The only real issue is the stars at either end, which may be in the way of the jump you want to make, and if so you have to fly around the origin star before you can jump, or around the destination star after you arrive. If this is the case, it might take an extra day or two.

Objects along an interstellar route are theoretically an issue but assuming the astrogator does nothing to avoid them, the odds against intersecting a 100D limit during transition are, erm, astronomical. Each hex is 3.26 light years across; jump shadows for main sequence stars will be on the order of an AU or so in size if we are talking G or F stars, and there are about 60000 AUs in a light year. So even if the galaxy were flat, the possibility can be safely ignored. The possibility is real, however, even if tiny, so it could be a way for a referee to engineer an adventure situation.

There are giant stars around but they are rare. They would have really big jump shadows, maybe enough to raise a small chance of obstructing navigation through the parsec, since the odds become more like 1 in 1000s rather than 1 in 1000000s against. But the more interesting thing is that there might be long trips involved in maneuvering out of or around their jump shadows.

I think we have another answer regarding the value of an astrogator: failure of the jump plot increases the likelihood of a jump precipitation (which the Referee would then have to plan out). I don’t recall any misjump tables having jump precipitation as an event.

I have been fascinated by “empty hexes” since day one, and the recent World Builders Guide makes an “unscheduled jump bubble displacement” in an empty hex because of a rogue planet or brown dwarf even more likely/explainable then before.

I think I may clarify my jump notes into a draft JTAS article.
"Space is big, space is so unimaginable big..." or a quote something like that. It's almost impossible to cross the asteroid belt and manage to randomly hit a mission ending space rock. Interstellar space is many order of magnitudes less dense, even if it is also many orders of magnitude larger between two stars. I'm trying to remember if there was an explicit 'minimum size' rule for how big something had to be to drop you out of space. Something about it needing to be an object bigger than the ship in question pops into my head, but that has a high probability of being an hallucination (no did not put anything in my coffee).

As a more general statement, I do think Astrogation is written rather weakly (my favorite part of the ChatGPT answer was when I saw the word 'Hijinks') As written, the astrogator makes an Easy roll - with DMs for distance at least, but still Easy. But the current edition has no concept of uncertain tasks, so as written, a bad roll only means 'try again' (or ignore that and let it be unknown - otherwise, other than slowing down a jump when you really need to jump NOW, it has little effect). The engineer's roll as written only really ever gets a +DM out of the task chain and then off you go - especially since there's no mention of proceeding after a failed astrogation check. Part of why I put a second Astrogation check into the empty hex part of Special Circumstances was to make astrogators earn their living.

The Companion has more complicated rules for jumping that makes the astrogator roll a little more important (and makes the average time 160 hours instead of a full 168 hour week - fine, but it means you often end up emerging in the dead of shipboard night if you jumped in them morning) and I like the idea of it, but it adds a ton of extra work to determine who and how someone is affected by a Bad Jump - only something to use if it drives the plot forward, not for every jump use.

Yes, I understand this. I just don't understand why it is unplayable, or in any other way undesirable. The only real issue is the stars at either end, which may be in the way of the jump you want to make, and if so you have to fly around the origin star before you can jump, or around the destination star after you arrive. If this is the case, it might take an extra day or two.

Objects along an interstellar route are theoretically an issue but assuming the astrogator does nothing to avoid them, the odds against intersecting a 100D limit during transition are, erm, astronomical. Each hex is 3.26 light years across; jump shadows for main sequence stars will be on the order of an AU or so in size if we are talking G or F stars, and there are about 60000 AUs in a light year. So even if the galaxy were flat, the possibility can be safely ignored. The possibility is real, however, even if tiny, so it could be a way for a referee to engineer an adventure situation.

There are giant stars around but they are rare. They would have really big jump shadows, maybe enough to raise a small chance of obstructing navigation through the parsec, since the odds become more like 1 in 1000s rather than 1 in 1000000s against. But the more interesting thing is that there might be long trips involved in maneuvering out of or around their jump shadows.
A rule that has no effect on anything is a waste of space in a book where space has a cost. If you spend time explaining a limit that does not, in fact, limit anything, then it's just useless. Which is the case for the interstellar application of the rule.

For the in system application of the rule, it has the same problem with any other in system travel. There is no way for the referee or the player to actually know where two bodies are in relation to each other at the any given time that is consistent. Can I jump from Earthport to Jupiter at the moment or is the Sun's jumpshadow in the way? NO IDEA. So, again the rule becomes unplayable.

Real space has this problem, but it at least has a "take the average and then use a randomizer to determine where it falls at the moment" workaround. Jump is a yes/no question, however.

Edit: You asked how it is undesirable. I ask: how is it helpful or desirable? In what way does it add something interesting to the play of the game?

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"Jump masking" is essentially how I think most people play the game - they might not do it consistently, but generally the assumption is that ships emerge from jump at or beyond 100 diameters from a world. Stars usually are not taken into account in this - often 100 diameters from the star would result in some inner planets being "masked" by the star's gravity well.

I believe stars having a jump shadow has always been the rule, but the first place I saw it was in a work required form that makes it easy to skip over if you need it quick during a game session. It would benefit from having both a "here's the formula" paragraph and a "here's some common numbers for certain star types and orbits" table.

Yet another example of rpg writers being the "ideas guy" but not wanting to do the grunt work, or perhaps it not even crossing their minds when they're in Writing a Book mode rather than thinking as a GM.

Stars and planets have always had a shadow that prevented emergence from jump within it and made entering jump within it dangerous. It was a long, long time before anyone tried to extrapolate that into "you can't jump from one side to the other". I am not sure exactly when that happened. Sygtrygg's post above suggests it was a Gurps Traveller development, but I don't know.

It's more of how much influence our dimension has on jumpspace.

I suspect that like Star Wars, they don't want starships to phase through solid objects.

There are a few suggestions of other actions for the Astrogation skill scattered throughout materials, but it can be a hunt.
As mentioned, the Companion book offers a modified version of jumps so the astrogators result affects the emergence point distance from the target 100D point.
JTAS 3, along with Jump tapes and stages of drive readiness, uses Astrogation for Jump Tracking - verifying or determining where a different ship jumped.
Deepnight/Referee handbook offers using an Average Astrogation check for plotting between in-system bodies and having the results influence the travel times (with a couple helpful charts and one that could use additional clarification)
Deepnight/Near Side of Yonder offers its use to set up a gravitational slingshot and reduce the time needed to accelerate to the target speed (in this case to 8% of lightspeed).

Contributing to the dearth of examples is that opportunities to use the Astrogation skill as a chain with the Pilot skill can be presented as just the Pilot skill. To illustrate:
Drinax Companion, during the First Prize adventure, has our pirates looking to capture a prize and offers setting up a minimal-activity (and thus minimally detectable) intercept course with a Difficult Astrogation check, chained to an Average Pilot check to make the interception.
However, Pirates of Drinax Campaign book, walking through the various steps of piracy, simplifies target interception as:
Locating target: Average Electronics (sensors)
Estimating target value: Difficult Broker
Plotting an Intercept Course: Average Pilot

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