Hey there! So, I was wondering about the compatibility between the Traveller Editions, specifically between Traveller Classic and Mongoose Traveller 1e/2e. I wanna start doing the groundwork for a 40k game using Traveller, and I found a nice supplement with expanded psi powers. Another thing I'd like to use the alternative point-buy system of Mongoose Traveller 2e as opposed to the original creation system.

And before you ask, I want to run classic Traveller because it's what I've read the most and I like it; but then again, I'm no expert on this system, so I don't really know what important differences are between the different editions, hence the post.

Mongoose Traveller will give characters more skills to characters and the application of those skills uses a more unified mechanic than Classic Traveller. The combat system has changed to one where armor subtracts from damage done instead of the all or nothing to hit used in CT. The stats are close enough to be used freely between editions. Spacecraft are similarly statted, but differently expressed and designed between CT and MgT1e and MgT2e.

For a WH40K game, I'd suggest using Mongoose Traveller 2e because I think that would emulate the setting of 40K better. YMMV, of course. To get a taste of each in order to decide upon which rules set to use, you can download the CT rules for free and the MgT2e rules for $1 from DriveThruRPG with the links listed below.

https://www.drivethrurpg.com/en/product/355200/classic-traveller-facsimile-edition

https://www.drivethrurpg.com/en/product/380244/traveller-explorer-s-edition

Thank you very much!

Emperor protects!

Indeed!

Now, if you REALLY want to go down a rabbit hole, grab a copy of CT Adventure 4 Leviathan. I believe that most of the prototype ideas which became the WH40K setting were first described in that adventure. It was written by GW, after all....

So Classic Traveller, Mega Traveller, Traveller New Era, Mongoose Traveller 1e and 2e, and Cepheus Engine are all very compatible but not 100%.  Aside from having different skills lists, there area stats balance differences between editions.  Over all, you should be able to use material between editions without conversion most of the time.

Quote from: jeff37923 on April 28, 2024, 06:37:00 PMIndeed!

Now, if you REALLY want to go down a rabbit hole, grab a copy of CT Adventure 4 Leviathan. I believe that most of the prototype ideas which became the WH40K setting were first described in that adventure. It was written by GW, after all....

I'll give it a look!

Quote from: BadApple on April 28, 2024, 06:40:30 PMSo Classic Traveller, Mega Traveller, Traveller New Era, Mongoose Traveller 1e and 2e, and Cepheus Engine are all very compatible but not 100%.  Aside from having different skills lists, there area stats balance differences between editions.  Over all, you should be able to use material between editions without conversion most of the time.

Thank you very much!

Classic Traveller and Megatraveller are the most compatible - as Megatraveller is the updated version of Classic (in a particular direction), rather like 1e and 2e AD&D.

For the Cepheus Engine, there is now a generic rules set called Cepheus Universal by Zozer Games:

https://www.paulelliottbooks.com/cepheus-universal.html

Quote from: El-V on April 29, 2024, 07:29:08 AMClassic Traveller and Megatraveller are the most compatible - as Megatraveller is the updated version of Classic (in a particular direction), rather like 1e and 2e AD&D.

This one I didn't know.

Quote from: Rhymer88 on April 29, 2024, 09:40:20 AMFor the Cepheus Engine, there is now a generic rules set called Cepheus Universal by Zozer Games:

https://www.paulelliottbooks.com/cepheus-universal.html

Thank you, I'll check it out!

In Classic Traveller, there was a big disparity in character power between those made from the regular character generation process in the original books, versus the one in the various splatbooks for the careers.

Like you could have a character with maybe 1 or 2 skills in the original version and then one with a dozen in the splatbook.

Quote from: El-V on April 29, 2024, 07:29:08 AMClassic Traveller and Megatraveller are the most compatible - as Megatraveller is the updated version of Classic (in a particular direction), rather like 1e and 2e AD&D.

Nope. Combat is pretty different, vehicle/starship creation is way different and not backwards compatible, plus the amount of errata you need to run it is overwhelming.

Quote from: jeff37923 on April 29, 2024, 07:44:19 PM

Quote from: El-V on April 29, 2024, 07:29:08 AMClassic Traveller and Megatraveller are the most compatible - as Megatraveller is the updated version of Classic (in a particular direction), rather like 1e and 2e AD&D.

Nope. Combat is pretty different, vehicle/starship creation is way different and not backwards compatible, plus the amount of errata you need to run it is overwhelming.

I would like to clarify what I said about compatibility.  Jeff makes a good point and I tend to not explain it even if I think conversion is easy.  (Thank you, Jeff.)

I would strongly caution any GM to thoroughly understand the core rules of the edition he or she is using before importing anything from another edition.  Doing an edition mash-up willy nilly can lead to catastrophe. 

Core books and rules expansions aren't very compatible across editions.  Even within editions, some splat books and optional rule don't play well together.  However, conversion of an individual rule from one edition to another can be fairly straight forward as the core 2d6 mechanic is the same.  The most compatible rules sets would be Mongoose 1 & 2 and Cepheus Engine.  Traveller 5 is intentionally made modular so that you can take a part of the rules set and apply them to the game you're running. (T5 is a great GM toolbox for any scifi game even if you're not playing a Traveller game.)
 
Generally speaking, assets like equipment and creatures can be used across the various 2d6 editions because they for the most part share the same format and types of modifiers.  GMs need to be a bit careful because some editions were more generous with modifiers than others.  I have found over the years that I don't need to do any conversion but I do need to take into account the power level of an asset.

By extension, adventures generally don't need conversion either.  On some occasions, a skill check will be mentioned and it will be up to the GM to determine if it needs to be adjusted for either target number or skill use.  I will sometimes adjust or swap out the stat block of a piece of equipment or a creature based on how it will play out with a particular party but tend to I do this regardless of the game I'm running.

Ships and vehicles are their own issue.  You should always use the construction tools for the particular edition you're using.  Almost all the official ships and vehicles have been republished for all the editions.  If you're wanting to do something like use a ship from Star Wars and you have stats for it for another edition, I'd recommend you take some time to actually convert it rather than just throw it into your game as is.   

Taking something like a splat book and converting it to work with another edition will be very dependent on case by case issues.  The three biggest points of concern are power level, skills lists, and combat rounds.  Fortunately the first two are straight forward if you have a solid grasp of the edition you're playing with.  Simply changing the modifier to something more appropriate or reassigning the skill to one you have on your PC sheet is a simple matter.  As Jeff has mentioned, combat is different across editions and tend to be the most complicated place to convert a rule.  Even if you have these concerns nailed down, a splat book can potentially derail your game if you're not very careful.  You need to fully understand what you are actually doing to your game rather than just embracing the fluff.  It may be easier to adjust and refluff material for your edition rather than converting from another edition. 

All in all, it's still a lot less work to move things from One edition of 2d6 Traveller to another than it is for something like across D&D 3e and 5e.

Wow, such in depth responses! Thank you very much!

Quote from: GrimGrimnicus on April 30, 2024, 11:33:55 AMWow, such in depth responses! Thank you very much!

You asked guys with autism to talk about the thing they liked. 

As someone with autism, I can relate