# 20 diameter limit variant

#### MrBackman

##### Mongoose
The canon Traveller rule of jumping beyond 100 diameters from a planet has always irritated me; why 100? (aside from the vague concept of diameter of course).
I assume it came about as a way to force characters to Travel (it is called Traveller after all) a bit before entering hyperspace. I have seen no space combat system where a planet and a safe jump distance from it could ever fit on a map. To be chased from a planet to jump point, to exit hyperspace directly into action etc, all of these have been impossible due to the huge measure of distance that 100 planet diameters really is. A space combat system with ranges maps a million km large would feel a way too super science (try focusing anything but x-rays over those ranges and learn what insanely-huge-mirror means)

I propose reducing the safe jump to 10 diameters and see what changes with the Traveller canon? Does anyone well versed in Traveller canon, adventures, fiction etc know anything that would make such a change weird or contradictory?

For an article on what 'diameter' really mean when calculating safe jump distances read this
http://vectormovement.wordpress.com/2010/05/30/100-diameters-limit/

The only Canon detail it changes offhand is the descriptions of how the various Major Races came to develop Jump drive. Those descriptions typically mention experimentation in "the outer system". This implies that normal space travel is mature technology before Jump is developed. In the case of the Vilani *very* mature, since they had to get out of the jump shadow of a gas giant.

Switching to ten diameters puts Earth's jump shadow inside the orbit of the Moon by a comfortable margin, instead of three times the Moon's orbital diameter. The Vilani would likely have had a neighboring moon to work from, since 11 diameters out is not unusual for gas giant moons.

Actually, I set the 100d limit as a minimum; ships can Jump relatively safely from 100d on up, but there is nothing to say that they have to Jump out at exactly 100d.

Likewise it is easier to just Jump into a system at any point, rather than Jump in at exactly 100d. I like the idea of the characters Jumping into empty space between planetary orbits and having to take three days to home in on the homeworld, taking the time to enjoy the sights along the way.

Some Starports could be set up in space stations in Lagrange points ahead of, or behind, the homeworld, far outside the 100 d limit; the ships can Jump close to the station and come nowhere near the planet, conducting all of their business offworld in the Lagrange station and having to travel to the homeworld via the station's regular 50-ton modular cutter bus service.

Keep in mind that some worlds will be inside the 100d limit of their sun/star, which means that ship may not be able jump out/in one of the closer planets.

Dave Chase

alex_greene said:
Actually, I set the 100d limit as a minimum; ships can Jump relatively safely from 100d on up, but there is nothing to say that they have to Jump out at exactly 100d.

I don't remember jump having to take place exactly at the 100D limit, just that its more common for that to happen since there usually isn't a reason to travel further, in real space.

Keep in mind that some worlds will be inside the 100d limit of their sun/star, which means that ship may not be able jump out/in one of the closer planets.

Dave Chase

This is very true, and apparently ignored in most adventures that I can think of. So the 10D limit probably is more in line WITH canon rather than breaking it. Nothing in any trade rules accounts for the 30 to 40 hours plus you'll spend travelling out to a point in space free of a 100D limit.

MrBackman said:
I propose reducing the safe jump to 10 diameters and see what changes with the Traveller canon?

Ok. So do it. Or did you mean that the core rulebook should be changed?

The main change is that it makes piracy a damn sight more difficult (which may or may not matter if you didn't like it anyway) - with safe jump altitude massively reduced, not only do jumpcussers have far less space to catch you in, but you're operating far closer to any putative defence force.

Not necessarily a bad thing or a good thing, just a thing.

The Notion that you need to be far away from gravitational fields to develop jump drive technology doesn't really set a limit on how far you must travel from a planet in order to jump, at least not how I see it.

[SPOILERWARNING, DON'T READ UNLESS YOU ALREADY KNOW WHAT THE ANCIENTS REALLY WERE ETC] Also, in my Traveller universe no race except the Ancients ever developed jump drives. Instead, each race found working jump drives in their home system, placed there by the Ancients. So, IMTU the reason why Solomani 'developed' jump tech in the asteroid field was because they found one there. The strongest argument for that is that the Droyne was given their Coyn sets by Grandfather way before they 're-developed' jump tech and before any other major race was anything but savages. The Coyne set still had six coins depicting the major races. How could Grandfather know which races would develop jump tech way before they they even had metal working? Also, the Traveller Digest had a great adventure about a missing archeological knife sought by the Aslan. The knife proved that humans saved Aslan from a suicidal nuclear war before they had space flight and also that humans gave Aslans their jump tech. All in my Traveller universe of course.

The real reason for jump tech not to be a given in the TL progression is the insane unlikelihood that all races should develop this galaxy conquering tech within a few thousand years of each other. Why is there no galaxy spanning super empire millions of years old? IMTU I also hold that jump tech is not natural but a by side effect from a super tech project created by an extinct earlier race that also accidentally created Grandfather. Jump tech is only possible along a corridor from the galactic core to the rim, the width is about the size of known space, this explains the Zhodani core expeditions as IMTU they are the only race that knows how jump tech really works and that it is not natural and only occur in a tiny part of the galaxy.

I think I'll add these shorter range jump limits as optional rules to Intercept. Having jump ranges that fit on the map will allow a lot of fun scenarios to be played, escape from Mos Eisley anyone?

MrBackman said:
The real reason for jump tech not to be a given in the TL progression is the insane unlikelihood that all races should develop this galaxy conquering tech within a few thousand years of each other. Why is there no galaxy spanning super empire millions of years old?

That may not be the default political behavior for the galaxy. Hardly any of the galaxy has been explored. So that doesn't mean there isn't jumpdrive technology outside of Traveller's mapped space, or that there never was any.

If jump tech comes naturally for a technological civilization why is the galaxy not filled to the rim with super old hyper tech civilizations? With jump tech the Fermi Paradox is even harder to answer. I find the insane improbability of so many civilizations maturing and getting jump tech within an eye blink of each other in space and time too hard to swallow. And why do they all stop at around TL 15? If civilizations almost always kill themselves at TL 15 it would be very unlikely that they emerge at the same time, if civilizations typically live much longer than that they would most likely meet with vastly different TLs. I k ow this is the background for all Traveller inspiration; Poul Anderson's Falkayn and Flandry novels as well as Piper's books but the question is still begging.

MrBackman said:
If jump tech comes naturally for a technological civilization why is the galaxy not filled to the rim with super old hyper tech civilizations?
It may very well be, after all Traveller's charted space is just a tiny region of the galaxy.
There are lots of possible reasons why more advanced civilizations did not contact the
inhabitants of this specific region of the galaxy in recent history, my preferred one would
be that it is a kind of nature preserve for the local ecosystem of tool using animals. 8)

ShawnDriscoll said:
MrBackman said:
I propose reducing the safe jump to 10 diameters and see what changes with the Traveller canon?

Ok. So do it. Or did you mean that the core rulebook should be changed?

No no no, the rules are just fine. I was merely tapping the collective knowledge of the forum for any sideeffects I might have missed if I do it. You know, like when someone added the jump masking rule and changed so many adventures and settings that it wasn't even funny. (yeah GURPS Traveller, I'm looking at you).

rust said:
It may very well be, after all Traveller's charted space is just a tiny region of the galaxy.
There are lots of possible reasons why more advanced civilizations did not contact the
inhabitants of this specific region of the galaxy in recent history, my preferred one would
be that it is a kind of nature preserve for the local ecosystem of tool using animals. 8)

LOL

I was wondering why we were so isolated.

Dave Chase

Seems very much canon.

If someone came up with an interesting and understandable algorithm that could vary the exact distance and/or the risks of a misjump, making highly skilled astrogators worth their weight in gold.

MrBackman said:
If jump tech comes naturally for a technological civilization why is the galaxy not filled to the rim with super old hyper tech civilizations?
Maybe it is. Someone will have to explore the rest of the galaxy to see.

With jump tech the Fermi Paradox is even harder to answer. I find the insane improbability of so many civilizations maturing and getting jump tech within an eye blink of each other in space and time too hard to swallow. And why do they all stop at around TL 15? If civilizations almost always kill themselves at TL 15...
Where did you read that? It is unknown what TL the rest of the galaxy is at.
No no no, the rules are just fine. I was merely tapping the collective knowledge of the forum for any side effects I might have missed if I do it. You know, like when someone added the jump masking rule and changed so many adventures and settings that it wasn't even funny. (yeah GURPS Traveller, I'm looking at you).

Players won't care about such things.

The Imperium will kill itself as it is edging into TL16, but its successor will, if Shawn's favorite edition is any indication, surpass it.

The real reason everyone "stopped" at TL15 in setting is entirely meta. Beyond 15 the social pressures of the technology are quite likely to produce a society we don't recognize and can't easily comprehend. The history of RPGs is littered with failed games that fell into the trap of incomprehensibility, discovered a fanatic audience of 20 people total, and were doomed to obscurity.

And really, if you understand the setting, you realize that TL15 is the snapshot TL in 1105. No one stopped. Interrupted, yes, but even Virus represented an advance.

MrBackman said:
I was merely tapping the collective knowledge of the forum for any sideeffects I might have missed if I do it. You know, like when someone added the jump masking rule and changed so many adventures and settings that it wasn't even funny. (yeah GURPS Traveller, I'm looking at you).
Few things come to mind, it would make smuggling easier. Being able to jump out significantly earlier would make someone leaving a world with an illegal cargo far easier. Presumably it means you could jump into the world significantly closer you would also have a better chance of "blockade running" or "bootlegging" your way onto the planet before anyone could react and stop you. They'd see you, they just wouldn't be able to get anything close enough to intercept in time. The later also assumes once on planet you could hide effectively, at least long enough to unload your cargo, this would in part be dependent on the world type.

Planetary raiders would have an easier time for the same reason. Would be come easier to land on a planet and raid a warehouse rather than try to intercept a free trader. But then again why raid the warehouse by force if thieves could quietly steal it and load it on a smuggler? (Of course on a world that's lightly defended, planetary raids may be a quicker opportunity.)

PB miners would still have to travel from the outer system to inner, same with passenger ships to outer colonies and bases (again depending on system inhabitation), so there would still be system traffic pirates could hit (most of which would not be jump capable; IMTU this was often the main target of pirates anyway since they can't jump away).

Intercepting jump capable ships and running battles in space would become even rarer and more unlikely because it would be too easy to just jump away.

Ironically, free traders and major freight liners would likely have fewer issues with piracy as a result. With less risk of piracy prices might drop, insurance rates on ships would go down, etc. (course Traveller doesn't actually make you insure your ship if you have a mortgage... always thought that was an oversight in the rules). Then again if warehouse theft went up along with smuggling, prices might remain the same, but ship insurance / mortgage rates might still drop. How you apply that in game is up to you.

The planet controls space within the jump limit, that just shrank which means the "Trade space" controlled and patrolled by the Imperial Navy just got bigger and their job likely just got harder. Might increase political tensions if your own moon is feasibly outside the jump limit, you might consider setting just beyond lunar orbit as the political boundary.

That's about all I can think of for now.

Consider this, withing 10 diameters you are still within range of the planets defenses....

Also consider how blindingly fast even a 1g Merchant is in respects to said jump limit. I have found that the tension of a risky Jump at 10 Diameters a wonderful plot device in actual play....

MrBackman said:
like when someone added the jump masking rule and changed so many adventures and settings that it wasn't even funny. (yeah GURPS Traveller, I'm looking at you).

Systems are not edge on to each other, and space is really, really empty. Jump Masking is only as significant as the Referee makes it. It is a Plot point that can be used to keep a ship in real space a bit longer, and it is just one tool to do that. MegaTraveller used a different tool (random jump arrival points) but the effect is the same.

If you really want that mental image of a ship entering or leaving jump while the destination world fills half the sky, just do it. You are removing "near space" as an environment of adventure (by making it a lot smaller), but this change alters nothing else in day-to-day play *of the setting*. However...

Food for thought: Traveller's writers spent a lot of time figuring out how to get the PCs out of their ship and/or air/raft to actually experience the places they visited. It isn't easy. Shortening the jump shadow makes that even harder, as now the PCs can jump away from just about *anything*. Running from interesting events can make for really boring play. This is why the Shlock Mercenary webcomic has denial technology, as another example; they *must* stay and figure out a resolution because they can't simply leave.

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