General Jump Fuel decreases?

[Spinward Scout]

T20 had Jump Fuel decreasing as you went up Tech Levels. I wonder if we can implement that a little different.

Say a fuel decrease every 2 Tech Levels after it was invented.

Jump-1 is invented at Tech Level 9. At Tech Level 11, you cut the fuel cost in half. Then you can go twice as far on the same amount of fuel.

Jump-1
TL9 - Beginning stage
TL10- Widespread Normal Use
TL11- Advanced stage (cut Jump-1 fuel in half)

Jump-2
TL10 - Beginning stage
TL11- Widespread Normal Use
TL12- Advanced stage (cut Jump-2 fuel in half)

And sp on...

What do you think?

 

[Grav_Moped]

My main issue with this is that, having gotten into the game from a LBB2'81 perspective, it seemed to me that the fuel requirement was an intentional limitation. Well, before drop tanks anyhow...

For example, even if you could get a factor-7 rating for a jump drive, you literally could not fit the necessary components into a hull (again, before drop tanks). LBB5 has simpler (and smaller!) numbers, so I'll use them to make the point.
Jump drive 8% (1%+1% per Jn)
Power plant (TL-15) 7%
Power plant fuel 7%
Jump-7 fuel 70%
Total so far: 92%.
And bridge for 20%... yeah.

In other words, the reason you couldn't have Jump-7 is that as far as one can tell, it's physically impossible (before drop tanks, of course). Not that you don't know how to do it yet, but that even if you knew how, it still wouldn't work.

 

[Rupert]

It'll change the economics of J3/4 merchant ships quite a bit in the late Imperium (and J1/2 merchants somewhat throughout the 3I).

It will also massively change warfare. Aside from the logistics, jump-capable warships become much more competitive with non-jump vessels. For example, a jump4 ship normally requires 5% for the drive and 40% for the fuel, leaving only 55% of its displacement for everything else. That becomes 5+20 = 25% for jump capability and 75% available for the rest, a 36% increase. As this allow smaller ships, and they require fewer crew, etc. you'd probably get three for two, facing off against about four non-jump ships. Alternatively you can just jump-6 (7+30 = 37%) into what is currently not even a jump-4 ship, which makes jump-6 battlefleets somewhat practical a makes TL15 (and TL14) a much more powerful advantage over lower tech levels.

Another effect is that it reduces the value of battleriders vs battleships, because it changes very little for the riders (their carrier becomes a bit smaller and cheaper), but makes battleships much cheaper.

Note that these effects will be considerably less pronounced in rules like MT and TNE where the fuel requirement was already lower. Going from 40% fuel to 20%, as with a CT jump-4 ship is much more significant than going from 25% to 12.5%, as you would in MT.

 

[Condottiere]

Mongoose allows customization of the jump drive, if you're willing to pay the premium, and have the relevant technological level.

It seems a fairly good compromise.

 

[TamsinP]

My main issue with this is that, having gotten into the game from a LBB2'81 perspective, it seemed to me that the fuel requirement was an intentional limitation. Well, before drop tanks anyhow...

For example, even if you could get a factor-7 rating for a jump drive, you literally could not fit the necessary components into a hull (again, before drop tanks). LBB5 has simpler (and smaller!) numbers, so I'll use them to make the point.
Jump drive 8% (1%+1% per Jn)
Power plant (TL-15) 7%
Power plant fuel 7%
Jump-7 fuel 70%
Total so far: 92%.
And bridge for 20%... yeah.

In other words, the reason you couldn't have Jump-7 is that as far as one can tell, it's physically impossible (before drop tanks, of course). Not that you don't know how to do it yet, but that even if you knew how, it still wouldn't work.

Bridge is 2% (minimum 20 dTon), not 20%. Add M1 drive (2% in LBB5) and you're up to 96%, leaving just 4% for staterooms, etc.

 

[Spinward Flow]

Bridge is 2% (minimum 20 dTon), not 20%. Add M1 drive (2% in LBB5) and you're up to 96%, leaving just 4% for staterooms, etc.

You can do it, but the remaining fraction of 4% for "everything else" means that you're looking at something BCS scaled, just in order to have sufficient absolute tonnage in that 4% fraction for the required crew (never mind weapons, revenue tonnage for passengers/cargo, etc.).

CAN it be done? Sure.
Is it economically WISE to do that? Well now, that's a different question isn't it?

T20 had Jump Fuel decreasing as you went up Tech Levels. I wonder if we can implement that a little different.

Say a fuel decrease every 2 Tech Levels after it was invented.

That just creates an evolutionary pressure (on design parameters) in which Higher Tech = ALWAYS BESTEST™ ... which shouldn't necessarily be the case. It would mean that the only starships that are economically viable are the high(er) tech ones, because they need to spend less tonnage fraction on fuel (pretty explicitly).

Jump-1 is invented at Tech Level 9. At Tech Level 11, you cut the fuel cost in half. Then you can go twice as far on the same amount of fuel.

NO.

AT MOST ... and even this idea is notionally uncomfortable in terms of implications ... I would do a -1% jump fuel requirement per +1 TL beyond minimum requirement.

• J1 @ TL9 = 10% fuel requirement per jump
• J1 @ TL10 = 9% fuel requirement per jump
• J1 @ TL11 = 8% fuel requirement per jump
• J1 @ TL12 = 7% fuel requirement per jump
• J1 @ TL13 = 6% fuel requirement per jump
• J1 @ TL14 = 5% fuel requirement per jump
• J1 @ TL15 = 4% fuel requirement per jump
• J1 @ TL16 = 3% fuel requirement per jump
• J1 @ TL17 = 2% fuel requirement per jump
• J1 @ TL18 = 1% fuel requirement per jump

• J2 @ TL11 = 10% fuel requirement per jump
• J2 @ TL12 = 9% fuel requirement per jump
• J2 @ TL13 = 8% fuel requirement per jump
• J2 @ TL14 = 7% fuel requirement per jump
• J2 @ TL15 = 6% fuel requirement per jump
• J2 @ TL16 = 5% fuel requirement per jump
• J2 @ TL17 = 4% fuel requirement per jump
• J2 @ TL18 = 3% fuel requirement per jump
• J2 @ TL19 = 2% fuel requirement per jump
• J2 @ TL20 = 1% fuel requirement per jump

As you can quickly surmise, just from looking at this, that if such a fuel consumption rule were ever "allowed" in Traveller, only BLITHERING IDIOTS™ would ever operate starships constructed at minimum tech levels. There's simply too much incentive to build everything at maximum tech levels in order to maximize the tonnage fraction NOT consumed by drives and fuel.

Think about it in BCS terms and it gets even worse.

A TL=15 J4 military starship would need 32% of its tonnage for jump fuel ... but a TL=15 J3 military starship would need 21% of its tonnage for jump fuel. In other words, J3+3 could rather easily become the "norm" for military BCS, since that would require only a 42% fuel fraction (compared to the original starting point, pre-rule change, of needing a 40% fuel fraction for J4). So to put it plainly, you would basically be "gifting" BCS starship designs with a +50% range increase (6 parsecs vs 4) AND the ability to "attack J3 and retreat J3 without needing to refuel"(!!!) among other advantages that previously DID NOT EXIST under the prior rules.

By comparison, a TL=14 J4 military starship would need 36% of its tonnage for jump fuel, but the power plant would require an additional +4% just for the increase in power plant tonnage needed @ TL=14 to support the jump drive ... and you're basically back at "near parity" again with the previous rules. Alternatively, you could do TL=14 J2 and need only 14% fuel fraction per jump, so a J2+2 (for 4 parsecs of range) would only cost 28% instead of the previous 40% ... and J2+2+2 would cost only 42% for 6 parsecs of maximum range. Once again, you're creating a set of advantages that previously DID NOT EXIST under the prior rules.

So with the rules change I'm outlining above, there is a tremendous advantage to be had in "dialing down jump numbers" in ways that can in turn extend maximum ranges quite dramatically. A TL=15 J2 starship would only need 12+12=24% fuel fraction for J2+2=4 parsecs of range. Compare that to a TL=11 starship that needs a 20% fuel fraction for J2=2 parsecs of range.

As you can quickly surmise, just from looking at this, that if such a fuel consumption rule were ever "allowed" in Traveller, only BLITHERING IDIOTS™ would ever operate starships constructed at minimum tech levels.

To put it politely, the 10% per J# fuel fraction is one of the foundational limitations built into starship performance in the Traveller setting. Mess with it at your own peril ...

 

[mike wightman]

MT introduced jump fuel reduction by TL.

Converting to CT multiply the jump fuel required by the following coefficient.

Tech Level	9->16	17	18	19	20	21
J fuel coefficient	1.0	0.8	0.6	0.4	0.2	0.1

 

[whartung]

As you can quickly surmise, just from looking at this, that if such a fuel consumption rule were ever "allowed" in Traveller, only BLITHERING IDIOTS™ would ever operate starships constructed at minimum tech levels. There's simply too much incentive to build everything at maximum tech levels in order to maximize the tonnage fraction NOT consumed by drives and fuel.

Well, "as it should be", to a point, save for one thing.

While the fuel costs are higher for a low TL ship, if I can BUY a used lower TL ship, then, in the end, for at least some duration, it will be overall cheaper to run the lower TL, used ship instead of a new, efficient ship, simply because of the acquisition savings. Trip costs go up, but amortize that against the total cost of ownership, and the lower TL ship may well work out.

And then the question shows up about whether a higher TL drive can be practically mounted and used in a lower TL hull, gaining those efficiencies without having to buy a new ship.

 

[Grav_Moped]

Yeah, I got the bridge percentage badly wrong, but I think the point mostly stands; RAW isn't going to give you a viable J7 ship in HG without drop tanks, and I'm pretty sure LBB2'81 didn't (even with the Z drives).

(I ran the numbers for LBB2'81 many years ago and remembered that it didn't work, but forgot the details when I reprised the point here.)

 

[Grav_Moped]

You can do it, but the remaining fraction of 4% for "everything else" means that you're looking at something BCS scaled, just in order to have sufficient absolute tonnage in that 4% fraction for the required crew (never mind weapons, revenue tonnage for passengers/cargo, etc.)

Please note that I hadn't gotten around to the maneuver drive, either. That's 2% in HG, minimum....

 

[aramis]

Yeah, I got the bridge percentage badly wrong, but I think the point mostly stands; RAW isn't going to give you a viable J7 ship in HG without drop tanks, and I'm pretty sure LBB2'81 didn't (even with the Z drives).

(I ran the numbers for LBB2'81 many years ago and remembered that it didn't work, but forgot the details when I reprised the point here.)

The economics work best for HG designs at about 20 kTd... but only GT gets you enough trade to fill that sucker RAW

Let's calculate the crew math a bit...

Capital Scale/BCS
 2%     Bridge
 8%     J7
 7%     P7
 2%     M1
70%     JFuel
 7%     PFuel
 0.2%   Command Crew (4Td*5 crew/10000 Td)
 0.685% Engineering Crew (4*(8%+7%+2%)/100)
 1.2    Service Crew (4*3/1000) - no Troops
 7 T    Model/7
======= ===================================
99.085% used

to have 1 Td Cargo, the minimum size needs to be 1.915%=8
so 0.01915×N=8 = 418 Td
But that ignore the 3 roundups: Command Crew Staterooms, Engineering Crew Staterooms, and Service crew staterooms

1000Td J7
  20   Bridge
  80   J7
  70   P7
  20   M1
 700   JFuel
  70   PFuel
  36   Command Crew (CO,XO, CMO, CompO, CNav, CHelm, 3 Admin)
   8   Engineering Crew (CEn, En)
  12   Service Crew (3)
   7   Model/7
====== ===================================
1038   Over by 38 Tons.

That overage is a minor issue...
Let's look at 10 kTd

10,000Td J7
   200   Bridge
   800   J7
   700   P7
   200   M1
 7,000   JFuel
   700   PFuel
    36   Command Crew (CO,XO, CMO, CompO, CNav, CHelm, 3 Admin)
    68   Engineering Crew (CEn, 16×En)
   120   Service Crew (30)
     7   Model/7
====== ===================================
 9,831 Used
   169 Payload

Not much can justify the need for this level of speed; the crew costs are pretty high. CO and XO should be at 7000 or so each, Helm makes 6,000, Nav 5000, Doc 2200, the Yeomen probably make 2000, the CEn is 4400, the En Rates 16@4000 is 56,000, the Service crew includes a Steward and Purser, so that section is 29*2000 + 2200= 60,200... 224 people to move 169 Td of cargo? salary runs per jump 76,900, plus 448,000 per jump in LS, plus 3,675,000 in fuel, total expenses of 4,199,900 per jump, or about Cr24,851.5 per ton, not counting maintenance share nor mortgage. Not much is worth sending at that rate... but RBC&C data is. (Recon, Border, Command, & Control.)

RBC&C data is almost always going to be worth insane costs, and double occupancies. Using hotbunking and crew in bunks, one can get the 1000 Td down to carrying data... an insanely expensive X-Mail courier.

Note that dropping below 1000 Td doesn't save much; the crew ratios are much higher for engineering. (triple, roughly) Command crew drops to 3: Master (CO/Pilot), Astrogator, Doctor. Lets try 500...

 500Td J7
  20   Bridge
  40   J7
  35   P7
  10   M1
 350   JFuel
  35   PFuel
  12   Command Crew (P, N, M)
  12   Engineering Crew (CEn, 2×En)
   0   Service Crew (3)
   7   Model/7
====== ===================================
 521   Just a bit over...

going double occupancy for all but Pilot and Nav saves 8 Td and only one jump of PP fuel saves 17.5 Td, for 25.5 Td in savings, and that allows this to be a viable J7 courier with 3.5 Td of cargo space, or 2.5 plus a turret... but then we double up the nav and gunner.
And that is without cheating the MD via a Bk2 C Maneuver, a dodge that gets us 5 more tons.

So a viable J7 is doable... but not economical for anything much... but this gives us a way to get a viable jump capable courier with a maneuver drive.
If we take the CT-77 exemptions, JD without PP, we can skip an engineer, 10 tons of MD, 35 of PP, and 35 of fuel.

 

[mike wightman]

Why are you putting a TL15 pp in these designs?
A TL16 power plant is smaller than a TL15 plant for the same output (using MegaTraveller and T20 at least)

 

[Rupert]

Why are you putting a TL15 pp in these designs?
A TL16 power plant is smaller than a TL15 plant for the same output (using MegaTraveller and T20 at least)

If you use MT you get all kinds of other problems. Remember that using MT the standard jump fuel requirement was 5+5xJn percent, but you still had to build most standard ships at TL15 to be able to get them to fit.

 

[Krikkitone]

T5 higher TL gave the
1. the higher order drives (where the range went up by a factor of 10 but with the same fuel consumption…although harder astrogation)
2. ability to use antimatter as jump fuel…which led to insignificant amounts of fuel volume %

 

[aramis]

Why are you putting a TL15 pp in these designs?
A TL16 power plant is smaller than a TL15 plant for the same output (using MegaTraveller and T20 at least)

Because I was using CT, which caps at TL 15. Extrapolating a CT TL-G without further references, whether it should be different or not is a judgement call; I chose to go the more cautious, «next break at 2 more TL»...
MT's fusion progression is also very different, with TL-F being 30× more powerful than TL-9, vs 3× for CT.

 

[mike wightman]

So use T20.

 

[bookwyrm]

T20 had Jump Fuel decreasing as you went up Tech Levels. I wonder if we can implement that a little different.

No.

T20 The Traveller's Handbook
Page 265
Jump Drives
Jump Fuel Option:
In campaigns where the Referee wishes to make interstellar trade and commerce more economically feasible, reduce the jump fuel requirement by one-half... the rest is an example of how this works and a mention about officially published ships wont be using this optional rule and that there'll be slight changes if using this option on officially published ships.

Now, I personally thought this is a great idea, but having been corrupted by ideas percolating on the CotI, thought it might be a little over-powered. My personal fix was to have the 50% less jump fuel available 2 tech levels past the introduction of a jump drive. There are other ideas out there, so please have fun Travelling!

J-1 50% less jump fuel at TL 11.
J-2 50% less jump fuel at TL 13.
and so on.

For those who think this isn't a good idea, there is a built in consequence to using this option. Using the space you save for anything other than cargo space or extra fuel space for a second jump is going to increase the final cost of the ship. Yeah, my excitement over having extra space evaporated quickly when I finally realized this. But I do like the extra options for ship design that are available when using the 50% Less Jump Fuel Option.

 

[aramis]

So use T20.

T20 rules have never been canonical outside T20. They're inappropriate for canon discussion.
The OTU evolved from CT Bks 1-5. MT, TNE/T4, T5 and MgT, while all portraying the OTU, are incompatible paradigms on the hardware side...
But that J10 exists is not just an element of rules in T5, it's an explicit change to the OTU Marc has made.

Plus, while I did do the math for T20, it was less interesting... the 1000 Td J7 1G is about 40 Td of cargo hold. I deleted it from the post before hitting send as It's not hardware canon. The difference is the TLG PP being much smaller and needing much less fuel.

The percentage items for J8, however, under the HG paradigm, is far less nice
Bridge 2%
PP 8%
JD 9%
MD2%
PPF 8%
JDF 80%
Crew Quarters ≅2%: Engineering (4*19%/100=76%/100)=0.76% and service (4*3/1000) 1.2%
as that runs to 111%, TL17, and that's the point where Antimatter canonically arrives as viable energy carrier...
But AM plants are not present in CT except as a reference on the TL table.
Even going DO on the crew and 2 weeks on the PPF still leaves it at 106%, and that's before accounting for the command crew and computer.

 

[mike wightman]

The jump 7 drive doesn't exist in CT. If you are willing to extrapolate it for HG purposes than do the same for the TL16 power plant which is an imnprovement on the TL15 plant according to MT, TNE, T4, T5.
For jump 8 again you are extrapolating the TL17 jump drive but ignoreing the MT jump fuel reduction at TL17, and the TL16 power plant improvements.

So yes, if all you do is say it is a TL15 ship with TL16 or TL17 jump drive then it is not achieving much- as in the ship capability, not your work.