Velocity and Jump Space

[Bense]

This has been addressed in several canon sources:

Marc Miller's Traveller (T4) Pg. 89 “Although jumps are usually made at low velocities, the speed and direction that a ship held prior to jump is retained when it returns to normal space.”

Traveller 5 Pp. 339-340 “Transition To Real Space: The ship fully returns to Real Space. Vectors Are Preserved. Conservation of momentum applies to ships as they enter and exit jump space. Absent any changes made in jump space, a ship arrives at its destination with the same vector (speed and direction) it had when it left. Speed and direction are expressed within a constant frame of reference which encompasses both start and destination (probably relative to the Galactic core).”
Yes, in T5 you can change your vector while in Jumpspace, though you need a drive that doesn't rely on being near gravity sources, as the maneuver drive in T5 does.

Or how about GURPS Traveller? GURPS Traveller (2nd Ed): pg. 120: Jump Types: When starships exit jump, they retain the velocity and direction they had on entering jumpspace. This leads to two basic types of jump:
Standing Jump: A standing jump attempts to give the emerging ship an orbital vector at the destination system. (Note that this will almost certainly require a non-orbital vector at the departure system.) Usually this is the safest type of jump, since it minimizes the possibility of colliding with a random asteroid or such. (Accidents still happen, which is why most starships have some armor.)
Running Jump: A running jump attempts to position the ship such that it need merely decelerate to approach the destination world. If poorly calculated, the ship will be off course and can waste considerable time maneuvering to the world.”

I believe the New Era had vectors preserved as well, but I don't have that one handy.

 

[phavoc]

This has been addressed in several canon sources:

Marc Miller's Traveller (T4) Pg. 89 “Although jumps are usually made at low velocities, the speed and direction that a ship held prior to jump is retained when it returns to normal space.”

Traveller 5 Pp. 339-340 “Transition To Real Space: The ship fully returns to Real Space. Vectors Are Preserved. Conservation of momentum applies to ships as they enter and exit jump space. Absent any changes made in jump space, a ship arrives at its destination with the same vector (speed and direction) it had when it left. Speed and direction are expressed within a constant frame of reference which encompasses both start and destination (probably relative to the Galactic core).”
Yes, in T5 you can change your vector while in Jumpspace, though you need a drive that doesn't rely on being near gravity sources, as the maneuver drive in T5 does.

Or how about GURPS Traveller? GURPS Traveller (2nd Ed): pg. 120: Jump Types: When starships exit jump, they retain the velocity and direction they had on entering jumpspace. This leads to two basic types of jump:
Standing Jump: A standing jump attempts to give the emerging ship an orbital vector at the destination system. (Note that this will almost certainly require a non-orbital vector at the departure system.) Usually this is the safest type of jump, since it minimizes the possibility of colliding with a random asteroid or such. (Accidents still happen, which is why most starships have some armor.)
Running Jump: A running jump attempts to position the ship such that it need merely decelerate to approach the destination world. If poorly calculated, the ship will be off course and can waste considerable time maneuvering to the world.”

I believe the New Era had vectors preserved as well, but I don't have that one handy.

Thanks for the cites Bense. I don't have those books on my handy thumb drive, just in dead tree form.

So Reynard you were correct, they have been discussed in some of the previous editions.

I have avoided the T5 rules since making the decision to stay away from the game system. The question then is how should this be handled? Should astrogators have bane plotting a proper exit if they are accelerating or moving? Should they get a boon if they are at a dead stop? Or should we assume calculations are always done with a ship at rest relative to the system it is jumping from? And would we increase the probability of error the longer they have been accelerating?

To put this into perspective, if you have been accelerating all the way from the orbit of the planet to the 100D jump limit of Earth takes roughly 400 minutes at 1G (1.3 million KM). Now if you were going into a potentially dicey system you might want to boost in your departing system for five or six hundred minutes to get your velocity up so when you emerge any potential pirate would find it very hard to intercept you before you were within range of the planet's defenses. No more lying doggo at the 100D limit waiting for prey to come to you. If you play within the rules you can racially alter a number of assumptions and expectations.

 

[NOLATrav]

The problem is Thrust to Change as opposed to accumulated velocity. Since there's no real rules for accumulating Thrust from turn to turn, you're kind of locked into your ship's Thrust rating.

I suppose you could cut travel times in half. Constant Thrust to 100D limit at Thrust 2 would be half what's listed on the Transit Times table. Then you emerge at Thrust 2, again halving the time to reach the destination world.

Seems like there should some kind of penalty for that. I always used current Thrust as a -DM to the jump plotting and jump! rolls in conjunction with a table that exited you further and further from you destination based on Effect.

 

[Reynard]

Phavoc, it would seem only right to make the very first random encounter roll at the moment of jump space exit with any distance bands established. At the moment of exit, the sensor operator makes first sensor check possibly with a bane because you have little knowledge what's around for such an immediate glance. No Boon necessary as the Senop has time to look around while coming in immobile. The ref determines if any encounter hazard (depending on the zone you exit into) is noticed. Opposition means combat is initiated (with or without surprise) and the rules and order of activity begin. No changing thrust before this, you start with what you have from the reentry of jump. If no opposition, the encounter is played out again with the velocity you started with, however, the pilot would have their chance to adjust vector and velocity as normal. Remember you may have set vector for an Accurate pinpoint exit (169 hours) but being off by 154 hours to 185 hours while an Inaccurate jump (Effect -1 or Effect -2) can send you father away from your intended entry, a lot of referee playground, and you have to revector while considering any start velocity you brought with you. Bringing velocity with you can be advantage or disadvantage depending on the amount of paranoia.

"Seems like there should some kind of penalty for that. I always used current Thrust as a -DM to the jump plotting and jump! rolls in conjunction with a table that exited you further and further from you destination based on Effect."

That's worked into the JUMP! roll as the Inaccurate jump and you must make the Astrogation check to jump.

 

[phavoc]

The problem is Thrust to Change as opposed to accumulated velocity. Since there's no real rules for accumulating Thrust from turn to turn, you're kind of locked into your ship's Thrust rating.

I suppose you could cut travel times in half. Constant Thrust to 100D limit at Thrust 2 would be half what's listed on the Transit Times table. Then you emerge at Thrust 2, again halving the time to reach the destination world.

Seems like there should some kind of penalty for that. I always used current Thrust as a -DM to the jump plotting and jump! rolls in conjunction with a table that exited you further and further from you destination based on Effect.

There is a rule in regards to that, but it's not in the sense you mention. The travel tables assume constant thrust 50% of the time and constant deceleration 50% of the time. Accelerating and then jumping would be the same... but you are correct in that there's no real mechanism to track G-turns. So really the fact that a ship can retain it's heading and velocity is pretty much useless in gaming because there's no way to account for it.

Phavoc, it would seem only right to make the very first random encounter roll at the moment of jump space exit with any distance bands established. At the moment of exit, the sensor operator makes first sensor check possibly with a bane because you have little knowledge what's around for such an immediate glance. No Boon necessary as the Senop has time to look around while coming in immobile. The ref determines if any encounter hazard (depending on the zone you exit into) is noticed. Opposition means combat is initiated (with or without surprise) and the rules and order of activity begin. No changing thrust before this, you start with what you have from the reentry of jump. If no opposition, the encounter is played out again with the velocity you started with, however, the pilot would have their chance to adjust vector and velocity as normal. Remember you may have set vector for an Accurate pinpoint exit (169 hours) but being off by 154 hours to 185 hours while an Inaccurate jump (Effect -1 or Effect -2) can send you father away from your intended entry, a lot of referee playground, and you have to revector while considering any start velocity you brought with you. Bringing velocity with you can be advantage or disadvantage depending on the amount of paranoia.

"Seems like there should some kind of penalty for that. I always used current Thrust as a -DM to the jump plotting and jump! rolls in conjunction with a table that exited you further and further from you destination based on Effect."

That's worked into the JUMP! roll as the Inaccurate jump and you must make the Astrogation check to jump.

In theory you have 100D space from any object of relative mass because it will pull you out of jumpspace if you come to near. Relative mass being, obviously, a relative term. At points I recall seeing that jump tanks have a potential to disturb your jump even though empty they would be pretty minor mass (though perhaps they may still possess their full displacement depending on their design).

I'm not sure which side would be more surprised- the side that was waiting for a random victim to show up, or the side that knows exactly when they are going to pop out of jumpspace. Either way a ship at speed would be hard to chase down if you are starting from zero, hence this would allow you to more or less avoid pirates at your leisure.

Once you reach your desired velocity you could cut your engines, and even with some inaccuracy if you are at 100D from a planet it's easy enough to correct your course and retain velocity. Now if you really screwed the pooch and came out on a diametrically different vector, THAT would be a pain as you'd have to kill all your velocity, then start all over in your arrival system.

Would be nice if this got addressed. You are right in that it's a lot of nice and naughty things a ref can use to, uh, spice up the campaigns.

 

[Reynard]

A couple more points. I would definitely say the majority of civilized port destinations have strict laws against ships screaming into their system at max velocity. If *you* can do it, everyone will be doing it. Does a starport need dozens or hundreds of shooting stars appearing out of nowhere? All this because, out of 60 possible encounters, three are pirates and one is 'hostile'. Remember your encounter distance depends on a sensor check and I again feel your first check should have a bane. That could mean very close encounters with other vessels, pirate or otherwise. In all reality I don't believe any police cruiser, SDBs or warships appreciate ANY ship coming out of nowhere unable to slow down very much and at close proximity. They can't take a chance your communication isn't a lie especially if your best excuse is "We're always afraid of pirates.".

If you are travelling so fast no ship can catch you, that should mean you are crossing ranges bands, many range bands per combat round. If you start at less than maximum range at the beginning, you will be very close to a vessel or facility. You probably will miss but such reckless behavior should get you arrested at best and shot at if you are bearing down at security or warships at worst. Wouldn't that be your crews' first reaction if the situation was reversed? And communication will cost combat rounds. Shooting past vessels at those speed should also be highly suspicious. Don't suppose you will always be moving away from encounters when you exit jump.

This all might not be canon somewhere or a game mechanic but it's very reasonable.

 

[phavoc]

I would agree with you on that. Planets are going to take a dim view of starships erupting from jump space with high delta-v because it's a safety hazard to everyone, especially somebody that is big and slow (though with no agility ratings, all ships are more or less equal in that sense).

Planets with traffic or say a C class starport or above are probably going to have local rules prohibiting that sort of thing. I had come up with rules that departure planets assign you an arrival zone prior to your jumping so it's more orderly on arrival. Basically it's traffic control from the other side since the arrival planet has no way of assigning anything.

Where you run more risks though is the lower end of the spectrum, or at planets that have more risk (i.e. more profit options). Those places are less likely to have patrols to keep piracy down. So if you do something like that there, it's next to impossible that you would ever get caught by a pirate before you were close enough to the planet - assuming the pirates don't have the run of the entire system that is.

I also agree that defenders may shoot first and ask questions later, especially if they are militaristic or high law kinds of guys (or if they've been snookered once or twice before). Warships tend to think of threats as threats and treat them as such. Police ships might be more wiling to give some room, assuming your flight path doesn't take you near any sort orbital or other ship - which a busy system will have more of both.

This probably isn't going to get addressed in the books, so either you just ignore the concept or generate your own tables. It really could be a big game changer play-wise, so it's sad that it's not properly addressed. Which I find personally very annoying. I purchase rule sets because I don't want to home-rule everything. Having something and modifying or not using it is much different than having something barely (or not, depending on the version) addressed and then left open for multiple interpretations.

 

[Reynard]

I think it's not addressed as such is because it is very complex just by the posts here, otherwise, like a lot of game minutia, it's up the refs and players to judge circumstances and procedure.

I thought I saw somewhere in a supplement velocity during exits was addressed and I mostly remember couriers and express boats get special exemption to high delta v entries for certain missions.

 

[phavoc]

I think it's not addressed as such is because it is very complex just by the posts here, otherwise, like a lot of game minutia, it's up the refs and players to judge circumstances and procedure.

I thought I saw somewhere in a supplement velocity during exits was addressed and I mostly remember couriers and express boats get special exemption to high delta v entries for certain missions.

I don't think it's "minutia". How often you need to flush the pipes in your trusty Scoutship after months of eating flaming hot space burritos is minutia. Explaining the underlying concepts of the game that may or may not mean the difference between survival is not minutia. Providing a rich background is the responsibility of game publishers. There is always a conceptual battle of providing too much vs. providing too little. I'm not expecting pages on the physics of this or crap like that. But a paragraph or two on (a) that it exist, (b) the dangers of NOT coming to a halt, and (c) some general direction on things a ref might want to consider when it happens.

I'm not sure about your gaming groups, but I've never been in one where at least half or more of the players were not min/max sort of people. I see the same thing in online RPGs too. You can see how some of the most successful games have a rich universe of stories and underlying explanations for what, why and how. Personally I find game systems that go through the trouble of explaining more of the underlying game system and mechanics provide me a far richer source of material to mine for my own adventures than those that provide the bare minimum and expect the ref to do the rest on their own. GURPS did a fantastic job of explaining things as well as providing future adventure nuggets in their books. And two of the ideas behind relaunching the product (aside from revenue) is getting old players re-interested in the game and enticing newer ones to come and try it out.

It's both sad and good to see some of us referring back to CT from 1977, and then rolling up through all the various versions of it over the decades. But I would posit that this is probably not the core gaming audience a publisher looks towards if they hope to stay in business.

 

[Reynard]

Considering the number of RPGs I have bought over the past 40 years, games got more and more detailed with lots and lots of rules and people were complaining not cheering. Now you see publishers putting out versions that are simpler. In Mongoose's corner was their decision to use the simpler rules of a modified Classic Traveller. Now the people complaining about T5's complexity want Mongoose to put out a 700 page version with every possible nit picking rule.

Can't win.

 

[-Daniel-]

After reading this thread I am going to continue with my old house rule that just ignores the real laws of physics and states they come out of jump in a slow drift allowing them to change course and react to what they find when they exit jump.

I do agree with phavoc that it is important and is interesting to think about in threads like this. But for the sake of playable games without the massive planet buster possibility, I am going to stick with what works.

 

[Bense]

You can have physics that work such that the vector is preserved and still have rules that largely ignore it. A good astrogator simply picks the right vector from his departure point in order to end up at a near-zero or even more convenient orbital vector at his destination, and it's all covered in the quality of the astrogation roll - no need for complicated tables to determine the differences in vector for the two systems, just change your transit time in a system based on how good the roll to jump there was. If it was a bad roll then he didn't quite get the right vector and the ship needs to spend more time accelerating to get to your destination planet; if it was a good roll then he got an exceptionally good vector and you need less time to match up. The Ref can rule on special cases if it makes for a good story.
As for the possibility of destroying planets (or more accurately, destroying their habitable surface) with super-fast rocks, well, even if you don't have a jump drive you have that problem because of the maneuver drives that don't need reaction mass and can work for months at a time.

 

[Bense]

As a side note, having vectors preserved makes piracy and defending a system easier.
If vectors are preserved, then there are predictable areas of a system that you want to jump from in order to have a good vector in specific destination systems. Likewise there are predictable entry areas in your system where a ship from another system is likely to emerge from jump space. Pirates and naval units can focus their attention in those areas and have a much better chance of intercepting the traffic they're after.
If your vector doesn't matter at all for jumps then where exactly you jump from and to doesn't matter either, and the number of likely places to find outgoing or incoming traffic increases enormously (to anywhere on the sphere of 100 diameters around your mainworld). Defending a system becomes much more difficult and pirates have a whole lot more space to try to find nice fat targets in.

 

[phavoc]

Considering the number of RPGs I have bought over the past 40 years, games got more and more detailed with lots and lots of rules and people were complaining not cheering. Now you see publishers putting out versions that are simpler. In Mongoose's corner was their decision to use the simpler rules of a modified Classic Traveller. Now the people complaining about T5's complexity want Mongoose to put out a 700 page version with every possible nit picking rule.

Can't win.

Again, that's not what I've been advocating for. Many ideas and concepts can easily be accomodated by a few short sentences, with or without a small table that outlines some of the consequences. If I wanted a basic rule set I'd use by CT books and stop purchasing nearly every version of Traveller that has since come out. But I keep looking for GOOD incremental additions to the game. Sadly I'm usually disappointed because the additions aren't always good in terms of playability and rather than fill in the gaps and holes they create new ones.

But you are right, T5 is a step in an entirely wrong direction. I feel it's taken all the worst of all the gaming systems and thrown them in a pot and then poured it out on pages.

As a side note, having vectors preserved makes piracy and defending a system easier.

If vectors are preserved, then there are predictable areas of a system that you want to jump from in order to have a good vector in specific destination systems. Likewise there are predictable entry areas in your system where a ship from another system is likely to emerge from jump space. Pirates and naval units can focus their attention in those areas and have a much better chance of intercepting the traffic they're after.

If your vector doesn't matter at all for jumps then where exactly you jump from and to doesn't matter either, and the number of likely places to find outgoing or incoming traffic increases enormously (to anywhere on the sphere of 100 diameters around your mainworld). Defending a system becomes much more difficult and pirates have a whole lot more space to try to find nice fat targets in.

Eh, that's more or less overcome if you spend the time in your origination system making the course changes and speed you want upon entering the target system. The volume of space at 100D around a planet is vast. Interceptions should be rare indeed since you can plot your arrival zone to be anywhere outside that space. Unless otherwise required by the arriving system for traffic control ships can appear anywhere they want to, thus making it highly unlikely that any one specific area would be used for more arriving ships than another.

Arriving ships, wanting to save time, would want to arrive along the orbital path so the planet's velocity is added to their closing, which would shorten the time frame to it's perceived safety. But you could do that along the orbital eliptical plane, or above it , or below it. Again, a vast amount of space to try and be in all at once. If you happen to be going in the wrong direction when a ship appears, you would have to kill your velocity, then start your new delta-v generation along an interception path. If your target had any decent head start you can't catch them unless you had very powerful drives.

That's the reality of it, though when you game it out you need not include all the ugly physics since the system doesn't support it. Still, you need to have some sort of idea how it all works and put something together so your PC's have some good chances of survival. Or not, depending on, umm, the dice rolls. Sure, that's it!

 

[Reynard]

"But you are right, T5 is a step in an entirely wrong direction. I feel it's taken all the worst of all the gaming systems and thrown them in a pot and then poured it out on pages. "

Seriously, where do you get all your hatred for T5? Do you own it or have access to know it so well?

Just this morning I was going over other items in it (I own it and love it) and came upon the rules governing space and jump flight. DETAILED information this topic has been discussing and sometimes even coming to similar conclusions. I'll accept what is written as Traveller canon since the same author has also published it in other editions and accepted enough it's brought up here. Still, it's a game. Each person running the game decides if the conservation of movement physically exists in Their Traveller Universe whether or not Mongoose feels it needs a notation.

 

[Condottiere]

There may be regulations, customs and etiquette involved, official and unofficial, local and Imperial.

It could be like a German autobahn, unlimited velocity as long as you can control your vehicle and not endanger yourself and others.

Which may mean that permitted velocity is related to your capability to break in an emergency.

 

[phavoc]

"But you are right, T5 is a step in an entirely wrong direction. I feel it's taken all the worst of all the gaming systems and thrown them in a pot and then poured it out on pages. "

Seriously, where do you get all your hatred for T5? Do you own it or have access to know it so well?

Just this morning I was going over other items in it (I own it and love it) and came upon the rules governing space and jump flight. DETAILED information this topic has been discussing and sometimes even coming to similar conclusions. I'll accept what is written as Traveller canon since the same author has also published it in other editions and accepted enough it's brought up here. Still, it's a game. Each person running the game decides if the conservation of movement physically exists in Their Traveller Universe whether or not Mongoose feels it needs a notation.

Yup, I was a Kickstarter contributor, got the dice, the barony, even the 4518th Lift Infantry shirt. I expected a much better game system and got much less. I don't hate it, but I don't have any problems calling out its shortcomings either. It's odd that you defend T5 but then call my asking for clarification of things in MG2 as overly detailed and nitpicking. T5 makes for a great reference book, but a poor gaming system. That's my opinion, but one that is shared by others. On COTI you can't even complain about it without getting threatened with having your account suspended.

Other game systems have jumped the shark with a new rules version and gotten deservedly called on the carpet for it. I don't bother referencing it much, though I do know there are some interesting rules and information in it. It sits next to my Shadowrun 5th edition book. Both are 5th editions (Traveller admittedly has had more than 5), but I will let you guess which one is more playable.

 

[Nerhesi]

This is neither here or there, but in support of the above, T5 is simply not applicable to anyone attempting to get into Traveller. That further narrows down the value add of the product, it does not appeal to most existing traveller players (as is evident by the reviews), and it definitely does not appeal to ANY gamer trying to get into traveller for the first time. Therefore, it appeals to a subset, of a subset, of a subset (if that).

Yes I'm a contributor, barony/dukedom something, dice, book, pdf, cd, and so on.

I think we're completely off topic now

 

[phavoc]

This is neither here or there, but in support of the above, T5 is simply not applicable to anyone attempting to get into Traveller. That further narrows down the value add of the product, it does not appeal to most existing traveller players (as is evident by the reviews), and it definitely does not appeal to ANY gamer trying to get into traveller for the first time. Therefore, it appeals to a subset, of a subset, of a subset (if that).

Yes I'm a contributor, barony/dukedom something, dice, book, pdf, cd, and so on.

I think we're completely off topic now

It's a tradition, like dimming the lights before jump. Hey, that's coming back into vogue!!

 

[Condottiere]

It will, once I figure out how to minimize power output in relation to transitional requirement.