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Belts and safe jumping

nDervish

SOC-10
Is there anything canonical regarding safe jump distances for asteroid/planetoid belts? Or anything resembling a consensus on the topic if there's no canon?

WBH includes a method of generating the average and maximum sizes of the rocks in a belt, but I'm not so sure that's useful information for determining how closely you can jump in. You may be 100 diameters from your destination rock, but I doubt that you'd be able to plot accurately enough to take all the other rocks in the neighborhood into account. (Or at least not at early jump-capable TLs.)

The same method also produces the width of the belt in AU, but assuming that the safe jump-in distance is at the edge of the belt seems a bit excessive, especially given that belts can, under this method, be up to 10 AU wide.

I would expect that you'd be able to jump out from closer to an origin asteroid in any case, although how much closer depends on whether YTU has jump shadowing or not - without shadowing, you could easily jump from within a few thousand km from the asteroid, while with shadowing, you'd need to get a bit further out to avoid passing too close to any other asteroids, but real-time data on asteroid positions should at least make it possible to find a closer point than for a jump in, albeit at the cost of more complex calculations.
 
I think it comes down to how detailed you want to be as a GM and what the needs of the session and/or campaign happen to be.

You could easily inform your players that they can jump almost directly to a given planetoid's 100D limit this time and that they cannot do the same another time or with another planetoid because of shadowing, masking, etc.

I would think that, the wider a belt is, the harder it is to jump to a planetoid within it. Again, you could tell your players they can jump close to this planetoid because it is currently on the belt's edge and they cannot jump close to this other planetoid because it is currently "deeper" within the belt.

All this means that you as the GM should apply the rules in a manner which best meets the needs of the session and/or campaign.
 
Emm, I think you are making a pretty fundamental error in imagining the distances between planetoids.

Asteroid fields like ESB?
 
Emm, I think you are making a pretty fundamental error in imagining the distances between planetoids. Asteroid fields like ESB?


Planetoids are very distant from each other, but the OP did mention jump shadowing/masking and the 100D means each rock is two orders of magnitude larger as far as jump drive is concerned.

I know I'm not assuming a belt swarm like ESB or a impenetrable wall. I am suggesting that planetoid 100D limits could preclude certain jump courses at certain times.
 
Emm, I think you are making a pretty fundamental error in imagining the distances between planetoids.

Asteroid fields like ESB?

I at least try not to. :D I don't know the exact average distance between asteroids in a belt, but I do know that it will typically be far more than 100d and suspect that, if you're standing on one, you're unlikely to be able to see another with the naked eye. That's why I figure that you'd be able to jump out from pretty close to the asteroid you just left.

On the flip side, though, there are a lot of them in a belt and I doubt that a TL 9 or 10 navigational database is going to be complete enough to calculate the position of every one of them when plotting a jump into the belt with enough accuracy to ensure that one won't just happen to wander past your destination point while you're in the process of arriving there. I'm not even sure whether a TL 15 computer would be up to that level of accuracy, given the sheer number of gravitational interactions coming into play.

There's also the question of just how accurate jump plots are. If you're aiming for 100d from a 1 km asteroid, are you guaranteed to arrive 100km from it? If so, that's pretty impressive precision when you're coming in from a parsec or two away... When 100d out is tens or hundreds of thousands of km, being off by a km or two doesn't really matter, but, when 100d is itself only a handful of km, I can see the precision of your jump plot being a greater concern than the 100d limit.
 
There's also the question of just how accurate jump plots are.


Physically, jumps can accurate to within 3000km per parsec jumped. It's when you add time to the equation that things get screwy.

Depending on which formula you choose, jump exits have as much as a ~34 hour window. With everything moving within a system and with the system moving too, aiming is going to be rather tricky if your bullet can arrive anytime within a ~34 hour period.

When you take into account that time variable involved, you can beleive that all those various planetoid 100D limits just impacted a lot more jump courses.
 
You know your time in jump from the moment you jump. If you have an accurate chart of the target system you will know where everything is when you arrive.

The jump time variable is a meta game randomiser for the referee to simulate the jump time, to the actual characters in the game they know the time spent in jump.

A lot of people have been making this mistake for a very long time now.
 
You know your time in jump from the moment you jump. If you have an accurate chart of the target system you will know where everything is when you arrive.

The jump time variable is a meta game randomiser for the referee to simulate the jump time, to the actual characters in the game they know the time spent in jump.

A lot of people have been making this mistake for a very long time now.

Say rather that a lot of people disagree with your interpretation of the available evidence.

In this case it doesn't matter, though. One can easily aim for a spot where no asteroid will be for the 34 hours during which one's arrival may occur. Indeed, one can easily aim for a spot where no asteroid will be for the forseeable future. Also, an asteroid belt is only slightly less empty than empty space. The odds against being hit by one if one jumped in at random are literally astronomical.


Hans
 
You know your time in jump from the moment you jump.

It's established canon that time in jump is fixed at the moment you jump. This does not necessarily mean that the crew knows the duration of the jump prior to initiating the jump and, more importantly to the question at hand, it does not necessarily mean that the duration of the jump is known when the jump is plotted.

If you don't know the jump duration at the time the jump is plotted and if you can't adjust your destination coordinates while in jumpspace, then whether you know the duration of the jump while in jumpspace is irrelevant to this question.

The first "if" is very much an IYTU question; my interpretation of canon is that the jump duration is unknown and unknowable prior to the moment that the jump begins, but others interpret it differently.

The second "if" is, well, iffy... My impression of canon is that you should not be able to adjust course while in jumpspace, but, on the other hand, Earth's orbital speed takes it approximately 1.8 million km, or roughly 150 diameters, in 17 hours, which makes for a significant difference in the time it takes to travel from your emergence point to the destination world, but there's no mention of this in canon (indeed, most assumptions seem to be that you'll normally precipitate out at exactly the 100d line), which would seem to indicate that ships "track" their destination world in some fashion while in jumpspace, whether through deliberate course correction or as a side-effect of how jump works.

Indeed, one can easily aim for a spot where no asteroid will be for the forseeable future. Also, an asteroid belt is only slightly less empty than empty space. The odds against being hit by one if one jumped in at random are literally astronomical.

Fair enough. :D Even with the knowledge that Hollywood's depictions of asteroid belts are wildly inaccurate, it seems that I've still overestimated their density.
 
"Speed of plot" also comes to mind, but really belts shouldn't pose a typical problem for astrogation (or navigation).
 
The second "if" is, well, iffy... My impression of canon is that you should not be able to adjust course while in jumpspace, but, on the other hand, Earth's orbital speed takes it approximately 1.8 million km, or roughly 150 diameters, in 17 hours, which makes for a significant difference in the time it takes to travel from your emergence point to the destination world, but there's no mention of this in canon (indeed, most assumptions seem to be that you'll normally precipitate out at exactly the 100d line), which would seem to indicate that ships "track" their destination world in some fashion while in jumpspace, whether through deliberate course correction or as a side-effect of how jump works.

I believe that part IS a game artifact. Arrival variance follows a bell curve, so by far the most arrivals will be plus/minus a good deal less than the full 17 that is possible. So you aim for where the destination world will be in 168 hours. Say the world moves 200 diameters in 20 hours (this depends on the orbit, but is a good ballpark figure). If you arrive in less than 158 hours, you will be further than 100 diameters in from of it; if you arrive in more than 178 hours, you will be more than 100 diameters behind it. But if you arrive in somewhere between 158 and 178 hours, you will be precipitated out somewhere along the 100 diameter limit. It seems a reasonable simplification for game purposes to ignore the possibility of arriving further than 100 diameter from the world.


Hans
 
It's established canon that time in jump is fixed at the moment you jump. This does not necessarily mean that the crew knows the duration of the jump prior to initiating the jump and, more importantly to the question at hand, it does not necessarily mean that the duration of the jump is known when the jump is plotted.
Read Marc Millers's Jump space article - not other peoples' interpretations of it.

In the article it states that the crew know the jump duration and man their bridge stations at the appointed time.
 
First, you guys are making the Mistake of Kahn - thinking two-dimensionally. If you jump to a 100d point out of the plane of the belt, then it will actually be pretty easy. Yes, the belt is 3-dimensional, as well. But, it will tend to sit (mostly) within a certain plane.

Second, I have always used the time variance to explain those variables you describe. You precipitate 12 hours early/late/whatever because 1) the calculations were off and you're a little ahead or behind where you wanted to be, or 2) something crossed your path that your program failed to account for. (Yes, that second one goes to the whole argument over masking and when it might affect you - not wanting to open that can of worms, again, just saying that's how I use it.)

Either way, make it as easy or hard as you need to in order to drive your plot. Just don't be too inconsistent, or your players will catch you at it! ;)
 
My impression of canon is that you should not be able to adjust course while in jumpspace, but, on the other hand, Earth's orbital speed takes it approximately 1.8 million km, or roughly 150 diameters, in 17 hours, which makes for a significant difference in the time it takes to travel from your emergence point to the destination world, but there's no mention of this in canon (indeed, most assumptions seem to be that you'll normally precipitate out at exactly the 100d line), which would seem to indicate that ships "track" their destination world in some fashion while in jumpspace, whether through deliberate course correction or as a side-effect of how jump works.

No, there's no adjustment of course going on. The jump program takes into account all the orbital positions at your destination. It's why you need that 3dTon computer next to the bridge - to hold all the orbital information necessary to make those calculations. It's also why all those Scout vessels are necessary, even inside the well-mapped 3I - to constantly update all that astrographic information.
 
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Say rather that a lot of people disagree with your interpretation of the available evidence.



Hans
I'm not interpreting - that's the mistake others have made for years. They interpret and then other people use their interpretations rather than the rules as written.

If you read Marc's article there is nothing to interpret - it clearly states the crew in the game universe know the jump duration.
 
If you read Marc's article there is nothing to interpret - it clearly states the crew in the game universe know the jump duration.


They know the jump duration after they engage the jump drive. You don't know when you'll come out until after you start and that means you cannot aim as well as you'd like.

Robject used a phrase I should have in my first posts: Speed of Plot. I wrote about planetoids' 100D limits blocking jump courses not suggest some ESB style belt but to suggest that the OP could make a case with his players for both of the situations he mentioned.

By using masking and shadows in his game, he left himself the possibility as a GM to keep the players from routinely jumping to and from wherever they chose. If the plot demands it, the OP could say "Sorry, there's an intervening 100D limit along that course for that period. You cannot exit there, the best you can do is exit here."
 
Technobabble for the win!

The actual size and spacing of asteroids in an asteroid belt isn't quite as important as the effective mass density of the belt.

The reason to get 100 planetary diameters (PD) out isn't that 100 PD is the minimum safe distance, but rather that 100 PD is a distance agreed upon by Lloyds of London (or your Imperial equivalent!)

Now I seem to remember from a Thanksgiving dinner (I come from a family that is full of physics professors) that gravity falls off as a square of the distance, and that several smaller object will have an effective gravitic attraction as if they were a single solid object.

That's about as far as I managed to guide my family until they figured out that I was only interested in PHYSICS! in relationship to a game. But that should be enough for our purposes.

Now think about a belt. Lots of small randomly massed objects in a fairly random mess. You're not going to have to worry about the entire belt, as the square of the distance drops the gravitic effect fairly quickly.

What you do have to worry about is the random gravitic noise. Insurance companies don't like random things that could cause them to have to pay out.

Anyway, you can see where the physics buzword generator is running.

In practical terms, I simply roll a d6 and apply the result as modifier when you jump from inside a belt.

Oh, so sad, there was a huge dense rock fairly close to you seconds before you jumped...

I once had some players that asked very detailed questions about jumping from within an asteroid belt, and then did it anyway. The rest of the campaign involved their struggle to get back into Imperial space. Of course, they would have been happy to get back to Zhodani space. Nothing like their look of horror as I pulled out a blank hex map and said 'you are here.' It was a long way home at jump-2.

Senjak
 
I once had some players that asked very detailed questions about jumping from within an asteroid belt, and then did it anyway. The rest of the campaign involved their struggle to get back into Imperial space. Of course, they would have been happy to get back to Zhodani space. Nothing like their look of horror as I pulled out a blank hex map and said 'you are here.' It was a long way home at jump-2.

Oh dayum! Nicely done. (I hope you had some stuff already generated for that.)
 
Read Marc Millers's Jump space article - not other peoples' interpretations of it.

In the article it states that the crew know the jump duration and man their bridge stations at the appointed time.

Marc's jump space article in ... ?

And how does that interact with misjumps, or is that also in the article?
 
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