I like this a lot. My players have a scout ship (the Highndry) that they refitted with scavenged J-3 jump drive, computer, and power plant from a wreck. I'm at work right now, but I should plug in the numbers to see what their fuel consumption is, as I hadn't thought of that.For full transparency, I've posted my "reinterpretation" of the CT Beltstrike fuel consumption formula that is mathematically backwards compatible with LBB2, but redone to make things easier/simpler when working with a LBB5.80 paradigm that relies on Energy Points (EP).
7 days of fuel consumption (tons) = (Hull Tonnage / 2000) + (EP * 0.35)
So a 2000 ton hull requires 1 ton of fuel consumption per 7 days/1 week for Basic Power (what I like to think of as housekeeping). This is essentially your life support (lights, atmospheric recirculation, etc.) along with keeping the heat pumps running (L-Hyd fuel remains cryo chilled so it doesn't boil off, inhabited spaces remain "shirtsleeves warm" for passengers and crew) as well as whatever other various and sundry plumbing and services need "power" to stay operational.
EPs are used for maneuver drives, computers, weapons and screens.
Producing 1 EP for 7 days costs 0.35 tons of fuel.
Plug in values for a 100 ton Type-S Scout/Courier and you get:
The formula works for "everything" from small craft to million ton tenders.
- (100/2000) + (2*0.35) = 0.75 tons of fuel consumption per 7 days @ 2 EP output from Power Plant-A drive
- (100/2000) + (1*0.35) = 0.40 tons of fuel consumption per 7 days @ 1 EP output from Power Plant-A drive
- (100/2000) + (0*0.35) = 0.05 tons of fuel consumption per 7 days @ 0 EP output from Power Plant-A drive
And just to be even clearer, my "research" into the Modular Box containerization system (in this thread) is predicated upon the notion that the Boxes are (natively) "unpowered" because they do not have a power plant (of any size) installed into them. So instead, the Basic Power requirement for any and all Boxes needs to be supplied by the "parent" transporting craft ... whether that be a small craft or a big craft (or a hangar/starport berth).
So if a 24 ton Box (any type) is docked to a 24 ton Fighter Escort, for example ... the Basic Power requirement for the combination is 48 tons of hull (obviously) which needs to be "paid for" out of the Fighter Escort's fuel reserves, in addition to whatever EP generation is going on.
Likewise, a 280 ton starship with 4x 24 ton Boxes docked externally to it has a Basic Power requirement of a combined 280+24*4=376 tons of hull ... not just 280 tons of starship hull. However, if those same 4x 24 ton Boxes are loaded internally into a hangar (or cargo) bay, with no external load(s) docked to the exterior ... then the Basic Power requirement is calculated using the 280 tons of the starship's hull.
Point being that "there's no free lunch" when it comes to the amount of tonnage requiring Basic Power ... and the more tonnage you have (or need to support), the higher the fuel consumption (per week) to maintain nominal operating conditions for that tonnage.
Pondering starship evolution
- Thread starter Spinward Flow
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Spinward Flow
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LBB2.77, p5-6:
LBB5.79, p32:
LBB2.81, p14-15:
Basically, by the time LBB2.81 got printed, the entire "jump governor" issue got thrown away as an "unnecessary complication" that wasn't worth maintaining, especially since LBB5.80 had "fixed" the problem already as well.
So technically it's an issue for craft designed using LBB2.77 (see: X-Boats) ... but is not an issue for craft designed using LBB2.81.
Spinward Flow
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So ... LBB2 standard drives are "baseload" power plants that have only 2 settings ... ON (full blast) and OFF.
LBB5 custom drives can "throttle up/down" as power plants between 0% and 100% ... no problem.
Sounds ... legit ...?
Spinward Flow
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It basically works for any and all craft.
The fun part is when you need to do any kind of "run silent" type of maneuvering. You can charge up the jump capacitors (i.e. "battery power") and use them for power instead (for a limited duration) to reduce your signature on sensors (no neutrino emissions from a fusion power plant) which can then lead to misidentification by opposing sensor operators as you innocuously drift past a sensor net. Then when you've "finished" your inertial drift move, you fire up the power plant and "make your move" with an element of surprise.
Alternatively, you can just simply "lie low" in hiding somewhere, running on Basic Power only ... until the sensor sweeps have moved on and you're free to maneuver again.
Or you're wanting to undertake a long duration assignment somewhere and need endurance more than speed, so knowing how economical your rate of fuel consumption is becomes a matter of "can we do THIS or not?" in terms of practicality in planning.
Spinward Flow
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{ temporary topic derail } Knowing what I know (now) about the CT Beltstrike fuel consumption formula, along with a few other various bits of various and sundry knowledges relevant to CT ... if *I* were to redesign the Type-S Scout/Courier with that greater understanding NOW I would make some very small tweaks to the design, which would yield the following:
For those who like to track changes against the LBB2.77/81 baseline assumptions:
- Fuel tankage increased by +1 ton from 40 tons to 41 tons
- Computer upgraded from model/1bis to model/2, allowing the Generate program to be included in the standard software package
- 3 ton cargo hold + 4 air/raft berth consolidated/shrunk to 5 ton multi-purpose cargo hold
- Bridge "upgraded" to manage 200 tons of total displacement, plus exterior hull "strengthened" to enable external docking of up to 100 tons of sub-craft for maneuver and/or jump towing to increase mission tasking flexibility
The computer model upgrade may, at first blush, seem like something of an extravagance ... until you realize that a model/1bis computer installation cannot afford the Generate program as part of the basic software package.
LBB2.81, p40:
Since a (stock, original) Type-S Scout/Courier is capable of Jump-2, but does not come with a Generate program as part of its standard package of software (LBB2.81, p41) because it CAN'T ... obtaining the Generate program has to be an "aftermarket upgrade" rather than a stock feature of the craft. This means that every time a (stock, original) Type-S Scout/Courier wants to jump, until a Generate program can be obtained ... there is an additional charge of Cr10,000 (J1) or Cr20,000 (J2) to obtain a jump cassette.
Simple mathematics will show that the "price" of a mere 40x J2 jump cassettes will equal the +MCr0.8 cost to obtain a Generate program.
Likewise, a (mere) 250x J2 jump cassettes will equal the +MCr5 construction cost price differential between a model/1bis (MCr4) and a model/2 computer (MCr9) installation at the time of construction. Volume production (90% construction cost) actually lowers this to 225x J2 jump cassettes equivalency (+MCr4.5).
Now ... ask yourself ...
How many times do you expect a 100 ton Scout/Courier to jump during a "nominal" operational lifespan in service of 40 years before being unloaded onto the surplus market?
- 250 / 40 = 6.25 jumps per year over 40 years
Yes, the construction cost is slightly higher going with the model/2 than the model/1bis ... but you wind up recouping that in terms of overhead expenses avoided on every jump the craft needs to make. It's either pay (some) more NOW at construction or pay (a lot!) more LATER when actually operating the craft. In other words, the life cycle costs are LOWER with the model/2 than with the model/1bis ...
And that's assuming jump cassettes are even "available" everywhere you go (see: type E-X starports, especially in low tech star systems).
The fuel tankage upgrade from 40 to 41 tons may seem like a "cute, but what's your point?" modification ... until you realize that with the CT Beltstrike fuel consumption formula in play, that extra +1 ton of internal fuel capacity makes J2+2 range a realistic possibility in actual operational practice. That "extra 1 ton" of fuel is enough for "over a week" of 2G continuous acceleration after making a J2+2 transit.
Likewise, that "extra 1 ton" of fuel capacity is enough for a J2+2 (origin > destination 1 > destination 2) through an intermediate location where refueling (starport, wilderness, whatever) is simply Not Available™ for whatever reason. This makes it possible to make "round trips" before needing to refuel.
If we assume that each "jump week" consumes 0.05 tons of fuel for Basic Power (see calculation in post #736 of this thread), that would leave a fuel margin of 0.9 tons of endurance for normal space operations after 2 jumps. Depending on EP demand ...
- 2 EP demand (continuous) = 0.9 / 0.75 * 7 days = 08d 09h 36m
- 1 EP demand (continuous) = 0.9 / 0.40 * 7 days = 15d 18h 00m
- 0 EP demand (continuous) = 0.9 / 0.05 * 7 days = 126d 0h 0m
Oh and ... side note ... jump cassettes for destinations 4 parsecs away would cost Cr40,000 per J2+2 jump, so ... even more reason to upgrade to a model/2 computer with a Generate program installed natively during construction.
Dropping the (dedicated) air/raft berth and replacing it with a "multi-modal" cargo hold ... which can accommodate EITHER an air/raft + life support consumable reserves (for longer duration exploration duty) OR a mail vault (for x-mail courier duty) ... just makes way too much sense to me. I figure that all you need are IISS "standard modules" that can be loaded into the 5 ton cargo hold space in order to "hot swap" mission duty tasking (Scout OR Courier) and you're "good to go" from a service perspective.
Note that 1 ton of cargo hold space is sufficient for 150 person/weeks of life support reserves (Cr150,000 cost to buy). With a 4 person occupancy of the starship, that's sufficient for a mission duration of 150/4=+37.5 weeks above and beyond the "standard" 4 person/weeks of life support endurance that a starship stateroom is capable of providing ... so maximum endurance of 39.5 weeks with a "full crew" of 4 persons aboard on an exploratory mission basis as far as life support goes (fuel endurance is a different issue).
Alternatively, the 5 ton cargo hold could have an additional 1x single occupancy stateroom installed instead of an air/raft berth, enabling VIP (or priority prisoner) passenger transport options.
Basically, you can "do more" with a 5 ton cargo hold than you can do with a 3 ton cargo hold + a 4 ton air/raft berth, in terms of options when it comes time for flexible outfitting for specific missions and assignments, as odd as that may sound.
The "external docking" modification makes it possible to take advantage of the 24 ton Box modular transport system that I've been working up in this thread, allowing the Type-S2 Scout/Courier to operate as a J1/1G transport with up to 4x24=96 tons of external load capacity ... which "could come in handy" in a wide variety of "second order/backup" operational tasking options, in which the Type-S2 Scout/Courier is "the only craft in the neighborhood" capable of hauling that kind of tonnage due to local logistics constraints (emergency or otherwise).
Note that a J1/1G "external transport" option makes the (redesigned) class work exceptionally well as a micro-jumper courier transport, in addition to all of the other potential capabilities built into the basic design parameters of the (updated) class.
{ we now return you to your regularly scheduled topic on Pondering Starship Evolution, already in progress ... } 
Yes but...Or to put it another way ... how long can you idle your petroleum product fueled ground car for, compared to how long you can drive it at highway speeds? The fuel tankage is exactly the same, but the fuel consumption rate due to the difference in demand load for power output is completely different. I would not expect the idle time endurance to be exactly equal to the highway driving endurance ... and I suspect that you wouldn't expect the fuel consumption rates to be the same in both contexts either.
If the power plant number is equal to the M-drive rating, and four weeks of fuel is based on that number, then the power plant would be working at a rate to supply the requisite power to the drive at that power setting for the four weeks. Not idling as the vessel coasted along, but supplying Pn for Mn. I agree with you that there is an oversimplification of needs, as there's no power listings for enviro and other life support systems including g-plates that crew walk upon, shielding against interplanetary debris that hits or is run through by the vessel, the computer and avionics, or the watts spend on the endless Z-box holo-games that Karl spends his time on instead of doing the One Job he had...
So maybe it's up to the ref to spitball how much fuel they think was used with the ship landed at the Class D port for two weeks. Could it run on batteries, or would it run at a reduced level? Could they run at a normal rate, sell the electricity to the local utility provider then skim later from a handy location? How much does this need to be codified? How you you handle all of that in YTU?
Spinward Flow
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Or you could just use the very simple formula provided in post #736 which I derived from CT Beltstrike and have something that is computationally consistent.
Well, in the Traveller context of craft construction, this would mean Jump Capacitors (which can be charged/discharged).
The answer is "yes" ... but ... the endurance of that power loading is limited.
The way I look at it is that fusion power plants generate (up to) their rated EPs every single LBB5.80 combat turn (20 minutes duration) for days/weeks at a time ... they just need fuel in order to be able to do generate those EPs.
Jump capacitors (36 EP per ton, as per LBB5.80, p42) will need to supply the EP demand every combat turn (20 minutes duration) until their stored EPs are exhausted. So a 1 EP continuous load would require 3 EP per hour of supply (from either a power plant or jump capacitors). Therefore ... 1 ton of jump capacitors filled with 36 EP can supply a demand load of 1 EP for 12 hours ... which is noticeably shorter than "4 weeks" like the default expectation for fusion power plants installed into starships.
Obviously, if you vary the load demand you can extend the endurance of the EPs stored in the jump capacitors (0.5 EP load takes 24 hours to consume 36 EPs of stored capacity), but you're still not getting into the "multi-week" range of endurance without having a very low power load demand.
And just for reference, the CT Beltstrike fuel consumption formula also includes an equivalency between Basic Power and EPs in it.
- 7 days of fuel consumption (tons) = (Hull Tonnage / 2000) + (EP * 0.35)
- (700 tons of hull / 2000) = (1 EP * 0.35) ... as far as fuel consumption rates go ...
The "fudge" here is the notion that power plants are rated for the "excess" EPs they generate for agility, computers, weapons and screens ... not the "total" EPs they generate for Basic Power + EP demand loads (agility, computers, weapons and screens).
With a suitable "berth-side hookup" ... sure. A craft's fusion power plant COULD supply (electrical) energy to a local power grid, if necessary. Taken to its logical conclusion, so long as the jump capacitors "aren't completely full" of EPs (so there's some "headroom" for intake as well as output), it ought to be possible to use a craft (with jump capacitors installed) for grid power conditioning to smooth out unwanted harmonics in grid supply/demand loading.
With a "large enough starport" with sufficiently occupied berths hosting craft with jump capacitors installed in them (participating in the program), this could potentially be a "side benefit industry service" of that starport infrastructure to a local power grid.
Depends on how "deep" you want the Life In Space Simulator™ to go, I guess.
First ... you start with the CT Beltstrike fuel consumption formula that I've provided in post #736 ... and work your way out from there, as needed.
And from this we can get an idea of how much electricity costs in Traveller. Unless I'm way off, the cost to the producer is about Cr0.0004 per kW-hr 'unit' at TL7-8, dropping to Cr0.0001 at TL15. The costs of transmission (lines and their maintenance and so on) would massively outweigh power-plant and fuel, so for the retail consumer power itself is effectively free, but the line 'rental' is not. This also means there's very little incentive to make more power efficient consumer and business devices, or to conserve power. The fuel cost at retail prices is such a small part of this that it disappears in the rounding, though a power utility providing power to a city and its industries probably won't think that way.
FWIW using TNE/T4 numbers it's something like Cr0.0006 at TL9-12 dropping to Cr0.0002/unit at TL15, so in the same order.
Spinward Flow
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Well ... maybe, maybe not. It really depends on how the local power grid is structured for billing its consumer/prosumer base. Even if the cost to generate power is ... marginal to negligible ... the cost to maintain the infrastructure will not be (as you've correctly cited). So what you could wind up with is billing based on how many kwh "move" between the grid and the entities hooked up to that grid. If you "move" a lot of power (in or out) across the grid then your bill goes up ... which then creates an incentive structure aimed in the direction of efficiency and load balancing (the real objective).
So there's more than one way to square that circle.
True, but that's an artificial structure designed to encourage something the actual costs do not. Which is not to say that it won't happen, of course - we have taxes and fees set up to encourage and discourage various activities all the time. I could also see a consumption tax on power to cover the cost of mitigation the environmental impact of the waste heat, for another thing.
But overall, Traveller's fusion plants make power astoundingly cheap, even paying the reactors off using ship mortgage rates and a planetary government or government-owned utility should be able to get better rates than that. I'd just never worked out how cheap it actually would before.
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