Fuel Swap- Game Effects

[kilemall]

People mentioning their swap of jump and maneuver drive sizes got me thinking about the game effects of using the 10% fuel tankage per number if used for maneuver instead of jump.
It's attractive to me since I am big on reaction drives instead of the various gravitics, but it might create some interesting possibly undesirable situations- most notably having multi-jump capability if you use acceleration sparingly or the design had large fuel tanks anyway.

It also occurs to me that ship economics could be better if refined fuel is only needed for small jump usage, and most of the 10% per M-number was unrefined.


Thoughts? Preferences?

 

[AnotherDilbert]

Anything that makes jump cheaper disrupt the setting.

Instead of J-2 & M-2 ships people would use J-6 & M-1 ships and before you can react they are two sectors away.


You can of course make jump a little cheaper, say 5% per jump, and require reaction fuel to make up the difference.

 

[McPerth]

This would not only disrupt the economics, as AnotherDilber says, but the strategical disrupting is also enormous...

The standard Traveller rules (this time in most its versions, MT being the only one where high jump needs less fuel) make the military fleet to rarely be able to jump more than J-4, and having to stop several hours (at least) to refuel. This is even worse when you are on offensive, entering enemy territory, as you cannot rely on the existing infrastructure to reduce this real space time.

This makes the "front lines", while fluid (mostly due to somunications lag), reduced to about 2-3 jumps, and gives the defender the advantage of those infrastructures (bases, starports, etc.).

This same fact makes the GG very important, alowing you to "ignore" any system without it on the defense, as the advancing fleet would have trouble to refuel there, and makes GG defense (with SDBs) an important part of the strategy.

If ships don't need to refuel after each jump, you can suddenly have J6 fleets advancing without delay, not allowing the defender the time to react, probably unaware about the advanicng fleet until it has reached deep in your rearguard.

I don't say this is good or bad, just explaining why I see this as too strong an strategic change to keep with current settings.

 

[Straybow]

GURPS Traveller cut the jump fuel requirement in half. That was courtesy of MM's good friend Loren Wiseman, not some dastardly saboteur. Somehow people managed to play GT and enjoy it without worrying about "disrupting the setting."


Change fuel requirements all you want. It will have some effect on gameplay. I would posit that a significant decrease in J fuel will likely make it better, unless the change is so big that it trivializes J fuel.


All the excuses people use for not fixing big problems with Trav econ are just that: excuses. Not actual rational engagement with the problem. MM could have fixed every bugaboo with T4 and made it something really worth the effort of superseding one's old favorite version. There would never have been a need for Mongoose Traveller, or Cepheus Engine, or T5. MM could have fixed everything in T5...


Meh. It's his game and he can do whatever he wants. Maybe he feels his IP would be weakened by taking fan suggestions. It wouldn't, and even if it might almost anybody on this forum or any like forum would happily sign over rights to ideas they've expressed publicly.


But it's your game, too, when you take it out of the box. You can do with it as you please. Don't let anybody restrict you with what is or is not canon. Unless you are producing work for hire under MM his wishes don't matter. Unless you want to publish outside of OGL and desire approval, his wishes don't matter.


@@ <= my two CrImp

 

[Condottiere]

What would disrupt the Traveller Universe is an alteration of time spent in hyperspace and/or an increase in jump range.

 

[nobby-w]

People mentioning their swap of jump and maneuver drive sizes got me thinking about the game effects of using the 10% fuel tankage per number if used for manoeuvre instead of jump.
[ . . . ]

If you do this, I would suggest something more like 5% each for both. But, consider pegging the manoeuvre fuel to a measure of total delta-V for reasons to be explained below.

Delta-V gets consumed in one of two ways:

1. Travelling in-system - from world to jump-point, taking off and landing. I would consider pegging it to somewhere like 1% per 10km/sec D-V. You might also consider making the manoeuvre drives less efficient in an atmosphere. Transit to and from jump points will use a few percentage points worth of fuel - say 1-5% delta-V at each end.
2. If you have a ship combat system that uses movement then manoeuvres or agility use D-V at a rate of 1% per point per turn. This works quite well if you have a hex grid system like the one used in Mayday. Use 1% of fuel per hex of delta-V or agility (whichever is higher) that you wish to apply in a turn. If you want to get mean you could even make the player allocate their total manoeuvre between delta-V and agility.

This achieves a couple of things:

1. Firstly, you can trade off in-system manoeuvre capability against jump range. If you don't need to do much but land at the starport you can jump further. If you need to do something insystem then you trade off jump range for endurance at the destination.
2. Secondly, you can add the dimension of endurance to starship combat. Note, however, that you will need to ensure your damage isn't too attritional as starships will run out of delta-V and agility pretty quickly.

Note, that this mod will almost certainly require you to pay some attention to the balance of your system. For example, LBB5 combat is pretty attritional unless you're engaging with capital ships armed with spinal mounts. If your ships only have a few turns worth of Delta-V and no weapons capable of inflicting critical hits then you might need to twink the damage a bit.

 

[nobby-w]

GURPS Traveller cut the jump fuel requirement in half. That was courtesy of MM's good friend Loren Wiseman, not some dastardly saboteur. Somehow people managed to play GT and enjoy it without worrying about "disrupting the setting.
[ . . . ]

Really, the 'balance' of short jump ranges comes down to a couple of points, both of which are essentially to do with the logistics of reffing sandbox games:

1. A short range Jump 1-2 ship lets you run a sandbox game in just a couple of subsectors. While we have travellermap.com now, back when I were a lad you had to get out dice and roll up your subsectors by hand. Rolling up a whole sector manually is a very tedious business - I tried it once sometime about 1982 and then automated it shortly after I got a computer that christmas. Rolling up one or two subsectors can be done in a few hours.
2. With a short range ship the number of places you can jump to is limited. In a sandbox game this limits the scope that the ref has to prep for at any given point in time.

A corollary to this is that if you want to do a game spanning a sector-sized region, a J1-J2 ship is really too short-ranged. Really, if you are thinking about a game where your party is gallavanting around a sector-sized region then you will need much longer ranged ships anyway - otherwise it will take far too long to get anywhere.

Now that we have apps that can generate sector-sized regions automatically or just download them from the interwebs, the logistic issues that drove short jump ranges aren't so relevant any more, and you may want much longer ranged ships in your 'verse.

OTOH, if you want to do a trad sandbox game with a free trader, then you really only need a couple of subsectors for a J1 or J2 ship to have enough elbow room. In this type of setting you could easily whip up a basic trading campaign in a few evenings.

 

[kilemall]

To Nobby's suggestions-


1% per 'G-expended' is elegant to be sure, but definitely limits maneuver speed and greatly slows down interplanetary travel, not to mention combat destiny being more about acquired DV/course then usual vector movement.
It's very Triplanetary, except I would say even the non-torch ships have a higher vee then yours would.
In-system jump assumes an even greater role as 10% fuel is far easier to handle then the VERY slow 5-G coast then 5-G decel, not to mention time.

I don't know about the point about non-spinal attrition- much more likely that the 'light' surface hits will drain off the fuel and leave the target on a one-way trip to the Oort Cloud. Having escape craft and/or low berths might assume greater importance, not to mention a TU with a lot of ships heading out-system waiting for enterprising sorts to salvage.


I would also anticipate piracy could be more of a thing- small craft loaded up with expendable fuel in the hold burn hard to match vee/course, load up the most valuable cargo in the now empty holds, then jet off before the Navy can arrive.
Merchant ships have to judge whether to cooperate and have their ship left alone, or have their fuel/drives shot out and left on the drift. A new level of vulnerability might make pirating more successful.

 

[kilemall]

As to the other points-


I don't know that J-6 ships ruin the enviornment and economics. Doing CT economics, there is no 'per-parsec' rate and so zipping between a J-1 and J-6 destination pays the same only the J-6 drive will be incurring greater financing/maintenance costs. That's reasonable given that higher jump allows for more destinations.


Going to Cr100 for maneuver fuel and Cr500 for refined fuel on the now-reduced jump costs (remember, on a monthly basis per PP#) means an overall reduction in cost, something like 80% less for the first jump and 100% for the second- a nice money break for the merchants, and J-4 ships are within sight of being usable.

I think you might need a higher payoff per ton/passenger for getting ships to go to small pop planets.

As to the strategic game- it certainly would obliterate chokepoint systems in all but a few cases. Fleets would end up being more of a guessing game as to which assets to cover with how much force- or risk all on intel or a guess and concentrate, with the consequences being horrific.
Navies would operate more like sailing fleets cut loose from 'coaling/oiling' stations, dependent more on food and ammunition supply. Unfortunately, one might expect more deep raiding/strategic warfare of destroying planetary war support economies.
Catching enemy fleets at High Guard 'anchor' for planetary supply may involve trickery and timing to be rid of invaders.
That may be more or less desirable depending on whether you want to play jump route games or not.

 

[Straybow]

I would think the way to go is to have jump engines sized and priced differently for higher jump ratings. It shouldn't be that one engine is J2 if installed on the 100dT scout and J1 if installed on the 200dT trader. A jump engine is specified at a jump rating and can never exceed it just because it is installed on a smaller ship.



So, take the standard jump engine table as J1 engines. For each higher jump rating add a fixed amount and a percentage of the J1 engine, both for cost and for drive size.


Then make jump fuel use depend on jump distance and loaded mass. The partially empty trader saves a significant amount of fuel. The freighter filled to the gunwales with bulk commodity is going to take more than the standard jump fuel.

 

[Straybow]

As for fuel costs...

The energy cost of H2 liquifaction is 14GJ/ton. Assuming a process with 75% efficiency gets us to a round 5MWhr/ton. The cost of supplying power is not the cost of fuel but the amortization and operational cost of the generating and distributing facilities. Even assessing at a measly Cr0.02/kWhr (about $0.08/kWhr) is Cr100/ton. This could be an underestimate by up to 50%.


That cost also assumes a local power source, either the producer owns the plant or has a deal with a provider close enough that there is no distribution expense. If you look at your power bill they may actually charge separately for generation and for distribution. Power purchased off a large-scale grid would be about 50% higher in cost.

But the fuel processor isn't doing this for free. This company is also running a large scale plant to liquify fuel with amortization and operational costs. It's probably less than the cost of a fusion plant, so add another Cr50/ton. Storage isn't free, either. The customer doesn't want to wait a day (or longer if there is a queue) for the plant to produce the fuel needed, so the producer's storage has to exceed the average daily sales. Let's say another Cr25/ton.

Now you have to get hydrogen from somewhere. Electrolysis from water takes a whopping 142 GJ/ton! Using heat from the fusion plant can cut that in half, but that would still be an energy cost of Cr500-750. Add 50% to that for purchased power and the cost is unthinkable.


So that means cracking hydrogen from hydrocarbons. That takes about one quarter of electrolysis energy, so that's in the Cr150-200 range (+50% for purchased electricity). That plant has amortization and operational costs, probably in the Cr50/ton range.

But you have to buy the hydrocarbons to start with. Now that probably costs the canonical Cr100/ton. That is, if the source is near the fuel processor. If you need to transport the oil (or whatever) to the plant, that could add 50% to that cost

Our total cost per ton is Cr475-575 for a self-powered plant that cracks locally supplied hydrocarbons and stores LH2, with a ~50% higher cost for grid power adding Cr150-200 and transport cost for non-local hydrocarbon adding up to Cr50.



__________________________________________________


I know, I know. What about fuel scooping? Operational cost for a starship is higher than operational cost of dirtside fusion electricity generation and hydrocarbon cracking. True, you don't "see" the cost when you do the scooping for your own fuel, but it's there.

To scoop fuel you would need completely separate tankage and piping (scooped H2 is pressurized, LH2 is not; valving would be different). Hypersonic compression is probably limited to about ¼ the density of LH2, so if you had equal size of tankage it would take four passes.

Maybe it could work with flexible piping and an inflatable scoop tank that would be only 20% of the size when not in use (taken out of cargo space). You probably can't do a hypersonic fuel scoop maneuver with an external tank. Of course, the cargo space for the full size of the scoop tank would have to be available, so you can't do it while substantially loaded.


Now you need liquifaction equipment. It's not particularly cheap and it might be large-ish on a size per ton/day. Suppose it takes 10% of LH2 tons/day, and you're processing one scoop tank per day. So now you need space equivalent to 22½% of fuel tonnage to house the collapsible tank and liquifaction equipment, and it takes four days to scoop and liquify your fuel.


Wait a minute, it also takes time to go to the GG to fuel up, and then back to starport to load cargo into the space you needed to operate the scoop tank. That could take far longer than travel to and from the jump point. In the Terra system, if Jupiter is on the opposite side of the sun it is 6.2 AU away, whereas 100D is only 0.01 AU. This is probably only practical for systems with a starport in orbit around a GG.

And this assumes scooping from a GG with primarily H2 atmosphere. Methane would have to be cracked... more equipment cost and space aboard ship, more time and power, and a separate tank for the hydrogen (which could be smaller, as you would only need to hold enough to buffer the input for the liquifaction processor).
Wow, scooping doesn't look very economical at all.

 

[aramis]

Doing CT economics, there is no 'per-parsec' rate and so zipping between a J-1 and J-6 destination pays the same only the J-6 drive will be incurring greater financing/maintenance costs. That's reasonable given that higher jump allows for more destinations.

That's arguable.

Differences in starship jump drive capacity have no specific effect on passage prices. That is to say, a starship with a jump drive of 3 charges the same passage price as a starship with a jump drive of 1. The difference is that a jump-3 ship can reach a destination in one jump that would take the jump-1 ship three separate jumps (through two intermediate destinations) to reach. Higher jump numbers also may make otherwise inaccessible destinations within reach. But, for two ships of differing jump numbers going to the same destination in one jump, each would charge the same cargo or passage price.

This paragraph can be read two different ways. If the price on a J1 from world A→→→D is 3xJ1 (A→B, B→C, C→D), the MP price is Cr24000, the J3 doing it at the same price is also Cr24000.

We know it was LATER clarified to price per jump. I also know, and have shown the work elsewhere, that CT-77 costs per parsec are near linear to J3, and pricing per parsec is thus reasonable. J4+ get exponentially worse.

Flipping the fuel rates in CT B2 (77 or 81) leaves all J1 merchants at 10Td to jump, and 10% for powerplant fuel; this results in the following rates:

Type	Standard	Flipped
Type A (200Td)	60Td/month	40Td/Month
Type R (400Td)	100Td/month	60Td/Month
Type A2-77 (200Td)	80Td/Month	60Td/month
Type A2-81 (200Td)	100Td/month	80Td/Month
Type M-77 (600Td)	370 Td/month	90Td/Month
Type M-81 (600Td)	390Td/month	240Td/Month

Doing the same with Bk5 variants makes a lot more difference.

 

[kilemall]

The CT-81 phrasing is focused on the jump drive number and whether that has a bearing on the cargo or passage price. It makes clear that the 3 parsec destination involves buying three tickets, but does not make clear that the J-3 ship involves three tickets worth of fees in one ticket- reads more like one ticket. TTB reads the same way.

I have always played with per parsec pricing, because it's insane to do it otherwise, but the original wording is ambiguous and poorly expressed for the real question people want answered, how much do I pay/get paid from here to there. So for RAW discussions I assume it is as is despite whatever clarifications.



As for the fuel costs, a couple thoughts.

Storage is pretty cheap in the TravVerse, just the cost of hull, so if we have 100,000 tons of capacity at an A starport and say max use/replenish rates of 50,000 tons per day, that's a sunk cost of BCr10 for storage alone, plus the functional equivalents of station 'bridges' computers bays and staterooms, and purifier, let's double it.

Getting fuel there is by grav vehicle, which we've already established is more economical in near-planet space. Eh, call it another BCr10 for a total outlay of BCr30, plus crew/robot costs of guesstimate BCr1 per year.

Power is not a problem, solar in most cases. Fusion is cheap enough as well when it's just station power running the purifiers.

Further assume an average use rate of 25,000 tons per day (50K is just a surge value), 25,000 x 500 = MCr 12.5 per day, 4.6 BCr per year.


So even expensively financed, the whole thing gets paid off in something like 20-30 years. 10 years if it has some sort of subsidy writing off the capitalization/profits. Then at some point the whole infrastructure would have to be refreshed again, say every 50 years.


Now if we are talking unrefined fuel, well yes the numbers are pretty ugly for that. If 50% unrefined use, double the pay off time. Could be the fuel facility has to be replaced about the time it's paid off. Which is about par for the course.

That's just back of the envelope costing. If people see a value to it, I'll actually do the detailed numbers, but just pointing out it's not unreasonable, even if off from what actually happens, if ever.



Of course I well know that your intent is to show that Traveller economics is fantasy. Eh, maybe. Probably.

But the system is not THAT unreasonable, plenty of technical cost structures we take for granted now would look like pure scifi 100 years ago, with people from 1918 arguing what is actually happening now is Not Possible.



Finally, yes I was largely thinking in terms of LBB5 fuel use. I'm still good with LBB2 not being quite the payoff, again commodity modular components optimized for compatibility and universal production/maintenance, not performance.

Not terribly important ruleset to consider, just a fun side thought that came to mind due to people who post about flipping their drives.

 

[kilemall]

Any thoughts about using methane instead? Pretty handy fuel to have around.

 

[HanleyTucks]

People mentioning their swap of jump and maneuver drive sizes got me thinking about the game effects of using the 10% fuel tankage per number if used for maneuver instead of jump.

From the perspective of the referee, you will now need to create many times as many subsectors for the players to adventure in.

With a J-1 or occasional J-2 drive, a single subsector can keep players busy for dozens of sessions, or even longer if the systems are detailed beyond the main world. With a J-6, and/or multiple Jumps possible, you need to create many, many more subsectors and systems for them to adventure in.

Getting but a single short Jump and then spending a week in Jumpspace works pretty well with the way most game groups work, with weekly sessions of a few hours. You adventure, you Jump, the session ends, and then one game and real world week pass and you adventure somewhere else. This gives the referee a week to prepare the details of the next game world. A week for one world, or at least the start of that world. Not bad.

With multiple Jumps possible, you've no idea where the players are going to end up, and so you'll have to prepare many game worlds - just in case. Lay out the subsector maps you have. Look at where the players are now, and then look at the worlds one or two Jumps away, and think about how much you'd have to prepare. Now look at how many worlds are several Jumps away.

Are you prepared to do that extra work as referee?

 

[SpaceBadger]

IMTU ways of doing these things...

Thread doesn't have an IMTU tag that I can see, but that seems to be the way most posts are tending, so I'll take a big double-gulp of that myself and wade right in... :coffeegulp:

As much as I can follow, there've been various proposals to impose fuel costs to trips insystem, whether interplanetary or just getting from a world out to a safe distance to enter Jump. Likewise, some proposals to twiddle with the amounts of Jump fuel with various goals in mind. And of course, a great deal of fun discussion of the many consequences, intended, unintended, obvious, hidden and otherwise, of all these proposals!

In One Of My TUs (IOOMTU?), the primary spacedrive is a bit like Stutterwarp from 2300AD. From high orbit to some arbitrary point of minimal gravitational influence from all nearby bodies (say 100D? sure!) the Mumbledrive functions as a very fast reactionless, inertialess drive. Once it gets beyond that 100D, it can shift to FTL warp pseudo-velocity. OTOH, the Mumbledrive is near-worthless from high orbit to planetary landing (again, it's really a function of gravity, so adjust accordingly when not landing on a standard planet!), so at civilized worlds it stops at a highport to let passengers and freight land by shuttle; ship's frequenting the frontiers must carry their own shuttles for this purpose, except for those very few designed to make their own landing and take-off with airfoil or lifting body designs and secondary engines.

[Writing now, that term Mumbledrive has jogged memories, and I recall discussing the idea once before. I'll run a quick search and see if I can save myself some further typing:]

April 16, 2014: Not as sleepy as I thought, so I have been reading more about power plants and drives, and have decided I like the breakdown between Jump, Maneuver, and Gravitic drives a lot, as the combination will enable me to juggle things around a bit to create the drive systems that I want for Firefly-type game, while still being able to (mostly) use mostly standard T5 ship designs and have the tonnages etc work out.

This may seem somewhat backward from the usual TL development. The combination of J+M drives is because I want it to work somewhat like stutterwarp in 2300AD - the same drive that lets you zip around the starsystem within 1000 diameters of centers of mass will also suddenly let you go FTL outside that gravitic influence - and is fairly useless when too close to center of mass (less than 10D).

Since I haven't got all of the TLs worked out, I'll just use X, X+1, etc.

TL X: System exploration using realistic ion or fusion drives, depending on need for speed (however even the fastest isn't much compared to what M drives will be able to do later). The greatest part of any ship is its fuel supply. No FTL at all. System ships don't land on planets; interface system is entirely separate, by shuttle, SSTOs, spaceplanes, etc.

TL X+1: Discovery of Mumble-Drive, allows FTL travel, but only outside ??? diameters from any significant mass. Still use TL X stuff to get around in system and interface to planet surface.

TL X+2: Refinements of Mumble-Drive allow use as M drive for fast STL in-system travel; no longer need the fusion drives in-system as these are much much faster; straight-line turnover trajectories replace Hohmann orbits and the like. Still need TL X infrastructure for interface to planets, as M drive efficiency drops way off within 10 diameters of large mass.

TL X+3: Further refinements of Mumble-Drive allow the M-drive function to be separated from the FTL function, so that system-ships can be built w M-drive only, saving the tonnage and expense of the FTL drive.

TL X+4: G-drive discovered, allows gravitic maneuvers within 10D limit (and only within 10D limit!). Shuttles w G-drive replace old TL X shuttles for massive fuel savings and much cheaper cost/ton lifted to orbit.

There may be further refinements, but this gives me the basic framework I want:

Starships: Have Mumble-Drive composed of components J+M, for outsystem FTL and in-system very fast travel. Usually do not carry G-drives and do not land on planet surfaces; interface is by G-drive shuttle, either carried by starship or available at local highport.

Frontier Starships: Some starships find it worth the tonnage and cost to also mount G-drives (and aerodynamic hulls) so they can land directly on frontier worlds without local facilities. (This is a trade-off compared to the interface shuttles generally carried by larger starships, which do not land themselves.)

System ships: Ships that don't need to travel out-system carry only the M-drive sized Mumble-drive; are not capable of FTL. Whether they have G-drive and aerodynamic hull depends upon mission/function.

Shuttles: Interface ships, in a variety of sizes (not just 90 tons ), equipped with G-drives only.

Haven't decided yet where I want Lifters to fit in.

Now how to fit in a reason for large exterior drive pods as on Firefly-class ships... Maybe the early G-drives weren't powerful enough to lift a ship off of a planet surface without some extra help from fuel-burning auxiliaries? Some of those old ships are still around, cheap because they are outdated?

 

[kilemall]

From the perspective of the referee, you will now need to create many times as many subsectors for the players to adventure in.

With a J-1 or occasional J-2 drive, a single subsector can keep players busy for dozens of sessions, or even longer if the systems are detailed beyond the main world. With a J-6, and/or multiple Jumps possible, you need to create many, many more subsectors and systems for them to adventure in.

Getting but a single short Jump and then spending a week in Jumpspace works pretty well with the way most game groups work, with weekly sessions of a few hours. You adventure, you Jump, the session ends, and then one game and real world week pass and you adventure somewhere else. This gives the referee a week to prepare the details of the next game world. A week for one world, or at least the start of that world. Not bad.

With multiple Jumps possible, you've no idea where the players are going to end up, and so you'll have to prepare many game worlds - just in case. Lay out the subsector maps you have. Look at where the players are now, and then look at the worlds one or two Jumps away, and think about how much you'd have to prepare. Now look at how many worlds are several Jumps away.

Are you prepared to do that extra work as referee?

Well, I'm just throwing out there just as a thought experiment to elicit comments just like this, nothing I feel strongly about.


Doesn't really concern me if I were OTU, I've got TravellerMap, and my IMTU has a 'there be dragons' line past where you are risking misjump.



Just might give a different feel if people could more readily cross deep space and get to remote worlds, it just takes time. Conversely, you could impose drastic maneuver fuel costs, and just getting to and from the planet to 100D means plenty of refueling anyway.