Jump Plant Requirements, Core Book vs. High Guard

[vladthemad]

I was trying to calculate the jump drive required for a 250 ton ship, and didn't like the idea of rounding up to a 300 ton requirement, so I took a look at the rules in High Guard as they seemed less modular and more exact. Things aren't matching up. Am I confused, or do the rules provided in High Guard ship construction give jump drives about half the size for the same jump distance of what you get when using the standard sizes in the core rulebook?

Assuming I am calculating it correctly, then what's the reasoning behind the 50% reduction in j-drive space required? Was this meant as a correction to the original rules, only meant for capital ships, or just an oversight?

Assuming I am doing something wrong, can someone explain what I missed so I can understand it better?

 

[ShawnDriscoll]

Each author has their own vision of what Traveller is (no two referees see Traveller the same way). None of the books are meant to be simulators of anything. Players don't even care about such stats. Then add to that the fact that the green title books are advanced rules that replace the basic core rules.

 

[atpollard]

Each author has their own vision of what Traveller is.

Fair enough, but this is a core rules issue.
High Guard adds options to and corrects other things in the starship design rules from the Core Book, so basic compatibility is not an unreasonable expectation.

None of the books are meant to be simulators of anything.

Except their own internal game balance reality ...
... Otherwise why not say that the ship and its components are whatever size you want them to be.

Players don't even care about such stats.

I respectfully disagree.
Some players may not care.
Your players may not care.
Many players, probably do care ... especially the players who want their own custom ship.

Referees who like to design ships (and the plethora of deck plans available on-line suggests that there are many), care a great deal.

 

[phavoc]

For building ships less than 2000 tons you need to use the Core rules (with errata and changes listed in High Guard). The percentages for drives and powerplants listed only apply to larger ships. In that sense the rules are incompatible. It has been an ongoing discussion since Classic Traveller High Guard came out.

I think while some players don't care, I do agree with you that many others do. But to what extent the different groups are more or less than another is debatable.

 

[Infojunky]

Am I confused, or do the rules provided in High Guard ship construction give jump drives about half the size for the same jump distance of what you get when using the standard sizes in the core rulebook?

Yes. It's a Traveller Tradition.....

Assuming I am calculating it correctly, then what's the reasoning behind the 50% reduction in j-drive space required? Was this meant as a correction to the original rules, only meant for capital ships, or just an oversight?

The issue steams from previous editions of Traveller as the source material got the Mongoose edition. In Mongoose there is a clear demarcation between Adventure Scale Ships (The Core Book) and Capital ships (HighGuard). Each of the design systems are supposed to be self contained.

Assuming I am doing something wrong, can someone explain what I missed so I can understand it better?

You haven't missed much, just hit on one of the legacy issues....

 

[GamingGlen]

For my spreadsheet I added a few drives, extended versions of A through G drives (AX to GX) for 100-ton ships to have an odd drive rating and for the 150-ton and 250-ton ships* to have less costly drives. I just averaged the two drives on either side and rounded up to a whole integer for space and cost. For example, the BX jump drive (halfway between B and C drives) takes up 18 tons and costs MCr. 25. For a 250-ton ship this provides a Jump rating of 2, not requiring the larger C drive.

I want to add 1-rated drives for a 100-ton ship, but haven't made up my mind on what drive letter to use (A1?, AZ?).

What was the first jump ship created by the Terrans? Is there any reference to it? Is it a museum piece? Did it have a Jump-1 engine and what was the hull size of the ship? I could see it being named Enterprise (too obvious) or Cochrane. I had an idea, and wrote down some notes, on a one-shot adventure (good for a convention) on that first jump (just across the solar system), with security breaches (by religious fanatics, isolationists, etc) and a mole in the ship crew to sabotage the effort. Never did expand upon it.

* those are the only x50-ton hulls I added, and only because of the 150-ton scout variant shown in the Scout book.

 

[phavoc]

For my spreadsheet I added a few drives, extended versions of A through G drives (AX to GX) for 100-ton ships to have an odd drive rating and for the 150-ton and 250-ton ships* to have less costly drives. I just averaged the two drives on either side and rounded up to a whole integer for space and cost. For example, the BX jump drive (halfway between B and C drives) takes up 18 tons and costs MCr. 25. For a 250-ton ship this provides a Jump rating of 2, not requiring the larger C drive.

I want to add 1-rated drives for a 100-ton ship, but haven't made up my mind on what drive letter to use (A1?, AZ?).

What was the first jump ship created by the Terrans? Is there any reference to it? Is it a museum piece? Did it have a Jump-1 engine and what was the hull size of the ship? I could see it being named Enterprise (too obvious) or Cochrane. I had an idea, and wrote down some notes, on a one-shot adventure (good for a convention) on that first jump (just across the solar system), with security breaches (by religious fanatics, isolationists, etc) and a mole in the ship crew to sabotage the effort. Never did expand upon it.

* those are the only x50-ton hulls I added, and only because of the 150-ton scout variant shown in the Scout book.

GURPS Interstellar Wars covers that time period. but the sizing is off from the regular Traveller drive scales. They also list the initial Jump-0 drive, which took them about .25 parsecs. As far as I know, there hasn't been any other source material produced that covers this early time. Maybe one of the boardgames might cover it?

I like your idea about filling in between the existing tables. For your Less than A drive, why not continue with your existing drive lettering, and call it AX?

 

[Rikki Tikki Traveller]

The rules in HG were written assuming larger ships (2000 tons +) so at the lower end of the size range covered by the Core Book, the formulas don't really work.

Per the rules, you use the larger size ship to get the right column on the table.

Alternately, Interpolate and round performance DOWN

 

[Condottiere]

Jump Drives are tricky things to figure out, especially since they use make believe physics and are subject to game balance.

In theory, drives for Adventure Class ships tend to be off the shelf, any custom job would be the equivalent of a one shot Rolls Royce engine, with the appropriate costs and maintenance penalties.

There seems to be a minimum tonnage for what I assume is radiation shielding and other thingamajigs that allow the transition between dimensions.

 

[dragoner]

And you'll spend 10x the time* on deckplans as you do figuring the specs, which is where the players connect with the ship.

*at least I did with the Chatl and Endeavour, and I was going back over the originals from FASA.

 

[vladthemad]

Even when you look at the high end of the "player sized" ships, 2000 tons, it's still arbitrary. If you take the lowest jump 1 drive for a 2k ton ship, you get the K jump drive and it's 55 tons.

Now if you hop over to High Guard and start designing a 3k ton ship, to get it a jump 1 drive you take the tonnage (3k) and multiply that by 2% to get the jump drive tonnage. That's 60 tons. So, to move a ship that is 50% bigger, it only takes five more tons of jump drive?

If you even want to get really nitpicky you could go for a 2001 ton ship. For a jump 1 drive on that ship it would be 2% of 2001, so 40 tons. That's fifteen tons less than what's required for a ship that's 1 ton smaller!

Now I get the point that on 100-2000 tons ships that off the shelf drives makes sense, hence the A-Z drives. I have no problem with that. For ease of use it even seems that it's fairly linear and simple on the table on 108. I'd have liked to see a formula so that odd sized ships (150 ton or 1500 tons for example) were better represented, but I can extrapolate that information easily enough on the off chance that my players want to build one of those.

I was just confused as to why 2000 tons was the oddly arbitrary drop off point for suddenly much more efficient drives. It would make more sense that as you went up in size it wasn't so linear and the drives became more efficient at moving larger ships. Then you hit the 2000 ton point the size of the drives was inline with the next step up in the High Guard book. If the simple answer is "tradition", that they were following classic traveller as an example, it's disappointing but understandable I guess. I just wish they would have fixed the glaring discrepancies in the old system while updating. I never played classic traveller, it being a bit before my time. I only megatraveller, and the one after that...New Era? Never cared for the whole Virus idea. I seem to recall the book for creating ships back then requiring a huge amount of math, and probably took just as long making deckplans...

 

[Anonymous]

I'm not looking at the numbers so go ahead and shoot this idea down if it's way off the mark...

It's annoying that the two systems don't cross well, I'd like to see commercial ships up to around 10k dT designed on the same platform as the other ships PCs are likely to come across in an RPG.

I would guess that the size of drives for 2k dT and below were not arrived at by a formula, the numbers were derived from someone saying "Yeah, that's about right" after building a bunch of ships and seeing how the numbers balance. Balance and keeping to the spirit of CT being high on the priorities.

I don't think the numbers will match but you could extend below 2k dT the percentages from HG increasing them (making the drives less efficient) as the ships get smaller. It may be an option to scale things so that as you get to 100 dT you meet the small craft table in HG. How that affects the balance of building ships and incorporating them into the many existing designs in all the published MgT books I don't know. It probably can't be done!

If Mongoose see this as a problem (with any kind of priority as I am guessing their to do list might have other things on it too!) then perhaps the best solution is a rewrite of one or both the CRB or HG. But making such a pivotal book as they both are sit in the game/setting/rules is a mammoth task that's probably not going to please everyone.

 

[dragoner]

I never played classic traveller, it being a bit before my time. I only megatraveller, and the one after that...New Era? Never cared for the whole Virus idea. I seem to recall the book for creating ships back then requiring a huge amount of math, and probably took just as long making deckplans...

Real life is way worse for engines, there is no linear relationship.

I only played CT before Mongoose, but everyone just used the High Guard math. MegaTraveller was bleh, just seeing all those zeros without scientific notation, TNE made it worse.

 

[Infojunky]

Now I get the point that on 100-2000 tons ships that off the shelf drives makes sense, hence the A-Z drives. I have no problem with that. For ease of use it even seems that it's fairly linear and simple on the table on 108. I'd have liked to see a formula so that odd sized ships (150 ton or 1500 tons for example) were better represented, but I can extrapolate that information easily enough on the off chance that my players want to build one of those.

Ask and ye shall receive;
M = Maneuver (H x M / 200) x 2 - 1
J = Jump H x J / 200 x 5 + 5
P = Power Plant H x P x 3 / 200 + 1
H = Hull tonnage

Internally these formula work up to the point of the Drive potential Tables, every edition that has used this system has had different drive potential tables that break/change efficiency in their own arbitrary manner. Part of this is due to a internal change in how Jump drives rated vs the Tech Level scale. The Standard drives letter rated drives were all given a tech level where they became available i.e. A through D were available at Tech Level 9, E through H at TL 10 and so on. The Drive potential table range was also greater in that it topped out at 5000 dTons (which as I said was one of those arbitrary rounding choices, but considering the "high Tech" TL 15 drives where required easier to make sense of)

Then you have High Guard which introduced a whole buncha different Ideas and is mostly geared toward being a Fleet Combat statistical simulation. Then Mongoose rewrote it.... Like the original it introduced a whole bunch of conflicting rules and such.

At the end I would say Choose a system that makes you happy.

Edit-Needed to clean up the math, I knew the error was in there and meant to fix it in my master Doc, but didn't. Is now and is fixed here.

 

[Condottiere]

As I interpret the Jump Drive tonnage formula, there is a minimum overhead; capital class was one percent, which would be a fraction over twenty tons without technology level adjustments, and for the Adventure Class, five tons.

You could drop in a forty plus ton capital class jump drive designed for two thousand and one ton ship into a one thousand ton hull, and have a four percent by volume jump drive, which would give you a jump three range (assuming the jump drive was built at a tech level that can support jump three).

In theory that could descend to five hundred tons, if you honour the minimum five ton overhead in the adventure class, though it's unlikely you'll achieve jump six or even seven.

 

[Reynard]

Mongoose went classic and keeping it simple. The micromanaging of everything became a hallmark for MegaTraveller but you soon spend much of gaming squinting at the huge columns of info on every ship, vehicle and star system.

I love the MegaTraveller system because I love building that stuff. Explains why I also have T5. I also very much love Mongoose Traveller because you can play the game fast and easy. It might be nice if they designed a unified construction system for ships but they didn't and I still play the game, ship building included.

 

[GypsyComet]

As I interpret the Jump Drive tonnage formula, there is a minimum overhead...

The percentage of a ship's total volume taken by a jump drive shows a distinctive pattern when graphed from 100 tons to 4000. It suggests either some required overhead or a weird physics related efficiency loss. Or both.

If someone really wants to use the HG percentages (or the MT percentages, for that matter), I have only one caveat: MENTION IT IN THE DESIGN. Document what you do, and if you share the ship with outsiders (like us), do not be coy about the changes.

Well, okay. two caveats. Be prepared to utterly break the trade rules if you change the relationship between available cargo space and monthly costs too much.

 

[Rikki Tikki Traveller]

One of the problems I have with the Tables without formulas is trying to design alien ships that are truly different.

WHY would an Aslan build a ship to standard human multiples of 200 Dtons?

Why not have them use multiples of 80 tons (Base-8 math instead of Base-10). If I had the formula that went behind the tables, I could make an ASLAN table that was different than the IMPERIAL table, but still followed the same "laws" for drive sizes at a given TL.

I think the formula should be:

Dtons = (A + BR)*M
Where A and B are numbers based on the TL and type of drive (A represents the minimum at that TL and B is the multiple for each Rating value).

R is the Rating of the drive/plant.
M is the size of the Ship (in Dtons)

Easy to make a table of "standard" ship sizes that way and easy to vary it by TL. THEN you could have a standard drive for a 250 Dton ship if you wanted.

 

[Infojunky]

One of the problems I have with the Tables without formulas is trying to design alien ships that are truly different.

I just posted those equations. They are Marc's not mine. What i don't have are the rounding/arbitrary changes that where used after the formula where run. Well I do, but it is a backwards examination from the results that one could used to make a limited Matrix equation with, but if simple percentages are too much Matrices are super beyond that.

 

[Condottiere]

For Adventure Class, it's five tons, with one ton undoubtedly being a workstation for local control/monitoring. Twenty percent consists of capacitors, and probably is part of the add-on.