MGT Fuel

[far-trader]

I know that, personaly, I'd feel a whole lot safer travelling in a ship with enough fuel to get to a destination and make the trip *back*.

Oh certainly, but... what transport does?

Not horses. You relied on finding feed and water (fuel for the horse) at waystops or took enough to get you there, not there and back.

Not steamships. Not trains. Not modern ships. Not airlines.

In fact not one type of scheduled transport I can think of off the top of my head does. Why? Simple. Because you don't have to and it cuts into revenue (or other) space (and profits if you're commercial).

There is no need to fear not arriving at your destination and being stranded without fuel in Traveller UNLESS someone does something stupid. Granted PCs do all the time. That's their nature. But they are the abberation. The exception. Not the norm, and to saddle the whole of creation with extreme measures to cover the actions of a few psychotic individuals makes no sense at all.

The only place I'd expect to see some fuel reserve is in military ships. And I generally do that. Typically through drop tanks since so many cannon designs neglected reserve fuel in the plan. Besides, drop tanks allow the fuel reserve without impacting the combat effectiveness of the ship.

In MTU drop tanks are not allowed for safety reasons on commercial ships. And are not (typically) seen as required for other civilian ships. The military is the only one with the need, the requisite training and personnel to mitigate the risks, and the occasional need to accept the risks. FWIW.

 

[far-trader]

Averages out to a monthly refuel, which corresponds to other expenses (mortgage, salaries). One week in jump, one week in system, repeat.

The bookkeeping is not that difficult Besides monthly doesn't work either, really, at least for simplicity as I've found/defined it. I always work things out to annual totals (presuming full capacity and fuel) and then divide it by the number of trips over the year. I find that much simpler. If you really want to count your credits just bank the savings whenever you need less life support or fuel or whatever.

Merely to conform with what has been a traditionally reasonable number of jumps that they can handle on a full tank. It could be whatever number that works for you though.

Isn't the traditionally reasonable number of jumps that they can handle on a full tank = 1? Perhaps there is the odd exception but for most (if not all) rule sets the standard is 1 jump of the maximum the ship is rated for.

 

[scrabble]

Isn't the traditionally reasonable number of jumps that they can handle on a full tank = 1? Perhaps there is the odd exception but for most (if not all) rule sets the standard is 1 jump of the maximum the ship is rated for.

Consider it "one trip out, plus the trip back".

 

[Vargr]

Oh certainly, but... what transport does? (...)

In fact not one type of scheduled transport I can think of off the top of my head does.

Well, the automobile and its variants kind of follow the "there-and-back" design, at least for an area limited to provinces/counties.

In MTU drop tanks are not allowed for safety reasons on commercial ships.

What about fuel bladders? Internal or external?

Awesome words about psychotic PCs and ship design, btw.

 

[aramis]

One form of scheduled transport does routinely carry "there and back" fuel; busses. In fact, they often carry 5-10 sorties (out & back=1 sortie) worth of fuel. But busses are not the best model.

Most scheduled shipping doesn't carry more than "There and divert just beyond", tho' in Alaska, quite a few scheduled flights do in fact carry sufficient fuel to Return to point of origin from above destination due to the high frequency of airport closures. But again, airport traffic isn't a good model, either; it's still short term.

 

[robject]

The bookkeeping is not that difficult Besides monthly doesn't work either, really [...]

Isn't the traditionally reasonable number of jumps that they can handle on a full tank = 1?

My car handles 5 round trips per tank, for my current job. And monthly works fine if you're doing the numbers by month. It makes as much sense as anything else.

But, my preference is to use the traditional jump fuel assumptions.

 

[aramis]

One thing to keep in mind: In MT, the JFuel was 5x the volume of the JDrive. Given the canonical access to empty hex jumps (see Chapter In Search of Longer Legs, in The Traveller Adventure), it is posisble to design warships to cross the rift without expensive calibration points. In fact, it's possible to get 3J4 (5% drive, 25% fuel per jump) with a model 9 on a 400 ton hull and small staterooms. At which point, the Rift no longer functions as a barrier to information. In fact, 2J4 is all that's needed. Heck, MT it's possible to build a 2J6 ship (7% Jdrive, 35% fuel per J6, 77%) but you need to go to turrets only, and crew in hot bunks, and officers in Small Staterooms, doubled.

If you muck with the fuel rates, you muck with the economics, and the information flow routes. An XBoat, for example, has a 9 day reliable cycle; 6-8 days in jump, plus 1 for meet, fuel, and launch. A 2j4 XBoat, however, has a 17 day reliable cycle (2x8 +1)... and those days add up. But it also means much more likely 16 days, and skipping many worlds. The average X-boat link seems to be about 3.4Pc; with 2J4, it's far more likely to be 4 and 3.5 for about 7.5 per 2 jumps, instead of 6.8, for an extra half parsec and one day less. It also means the scoutships can meet it in deep space and further marginalize the in between worlds. And a 100Td 2J4 is doable under MT. Not quite under MGT...
100 hull
010 Bridge
020 JD B
008 PP B
040 F-1J4
002 F-P 2W
003 MD B (4G)
005 mail cargo
008 2xStateroom
004 mission.

If one halves the fuel for additional parsecs... (the MT fuel rates), one gets an extra 15 Td, but if one halves the whole, you lose two tons mission, but gain a second jump.

BTW, note the 4G as well...

 

[Jame]

Averages out to a monthly refuel, which corresponds to other expenses (mortgage, salaries). One week in jump, one week in system, repeat.

I've always disliked the one week in system thing, on the basis that it doesn't make economic sense. Two or three days, sure, if that's how long it takes you to arrange cargo and passengers, but the week wait is only good for making space for adventures.

But I accept it at times, as this IS an adventure game.

 

[far-trader]

Consider it "one trip out, plus the trip back".

Ah, got it, thanks.

What about fuel bladders? Internal or external?

All in MTU: Internal and external hard tanks see some use (and no prohibitions or safety worries) on civilian and commercial ships. Bladders are internal only and again quite safe (within reason) and occasionally used. But in all these cases they impact the amount of space aboard (usually displacing cargo) for internals or reduce your performance when external.

Though I'm not recalling the MGT specifics for them at the moment which could change my S&P in that rules set.

Awesome words about psychotic PCs and ship design, btw.

Heh Thanks, but it was more satire than truth, though I've known (and played) some that fit the extreme And it would make for some "interesting" design parameters if they drove the standards :devil:

I've always disliked the one week in system thing, on the basis that it doesn't make economic sense. Two or three days, sure, if that's how long it takes you to arrange cargo and passengers, but the week wait is only good for making space for adventures.

But I accept it at times, as this IS an adventure game.

I know what you mean, but I figure it is a week to find (all possible) passengers and freight, and best speculative cargo. Note the "all possible" though. In MTU you can leave early, spend less time looking, and make more trips. But you may not fill your hold and pax capacity and the best speculative deal you can find on short notice may not be the best deal you might have found with a little more patience

I've never seen the week in port as an adventure window, more of a setup to the adventure. Oh sure "stuff" can and does happen in port, but it's more often just random encounters and short action sequences and not part of the overall story.

 

[E.D.Quibell]

I've always disliked the one week in system thing, on the basis that it doesn't make economic sense. Two or three days, sure, if that's how long it takes you to arrange cargo and passengers, but the week wait is only good for making space for adventures.

But I accept it at times, as this IS an adventure game.

It depends on the jump masking of the main system from the primary. If you have say a G2 IV star with the main system in orbit 3, you have 1.62 AU to travel before you get to the mainworld. 1.62AU at 1G takes 2 days and 19 hours (approx). Two days turn around on planet and 2 days 19 hours back to jump point ...

If there were a gass giant on the way to the main world you would of course stop for skimming on the way in or out (or both!).

Regards,

Ewan

 

[robject]

I've always disliked the one week in system thing, on the basis that it doesn't make economic sense. Two or three days, sure, if that's how long it takes you to arrange cargo and passengers, but the week wait is only good for making space for adventures.

I don't make any time limit requirement. If a cargo is located early, ship out early.

But, if the adventure is not about being a merchant, or if time is not critical at the moment, then glossing over and saying "it takes X weeks to get from Y to Z" is just natural.

 

[Grognard]

Remember the one week was an average.

Some systems will require extensive travel time to reach the mainworld. (Some mainworlds are within 100 dia of other bodies, stars, or gas giants) and if you pop out of J space on the worng side of the system......its a long way in a slow boat.

Also, some starports will take longer to complete all of the admin required to land and secure/sell cargo. A busy starport may have a dozen ships ahead of you in the fueling queue.

For groups that want to speed things up by gassing up at the local GG, i allow them to cut their time by a percentage.

Now, GT Far Trader had a system for determining travel time and jump masking etc..

I dont like that much math, and use the effect of the Astrogation roll to influence the travel time, and vary the travel time. But using 7 days is a good average when exact time doesnt matter to the group.

Again, only use as much detail as you need at the time.

 

[swest]

You know, I read this entire thread and yet haven't come away with even a clue as to what is meant on page 142:

Suffocation
A spacecraft with power can sustain life support for one person per
stateroom for one month comfortably, and for six months at a stretch
(number of staterooms 5,000 person/hours). Without power, this
drops to two weeks at most.​

What is the point of this paragraph? Particularly in the context of fuel consumption...

Guess I'm just stoopid.

 

[aramis]

You know, I read this entire thread and yet haven't come away with even a clue as to what is meant on page 142:

Suffocation
A spacecraft with power can sustain life support for one person per
stateroom for one month comfortably, and for six months at a stretch
(number of staterooms 5,000 person/hours). Without power, this
drops to two weeks at most.​

What is the point of this paragraph? Particularly in the context of fuel consumption...

Guess I'm just stoopid.

Naw; it's just discussing three related issues (of 4 expendables). Plus time-use labels.

When you pay that life support charge, each Cr2000 life support charge is 5000 person-hours of air and water filtration, plus supplementary oxygen for that duration with active schedules. (It's also 2 person-weeks worth of food.)

If the power is off, due to powerplant damage or no fuel, then the air & water aboard is 2 person-weeks per stateroom, assuming you don't freeze first, WITHOUT using filtration. (Plus, the head is going to REEK... and there's no artificial gravity...) This is often called Reserve life support: how much air the system holds. Each 4 Td of empty cargo should be another 2 person-weeks.

A person–week (=168 person–hours = 7 person–days) is a sufficient ammount for one person for one week.

If I have 10 person-weeks (=70 person-days) of LS paid for (KCr1 per week, BTW), that's 1 guy for 10 weeks, 2 people for 5 weeks, 3 people for 29 days 8 hours, 4 people for 17 days, 5 people for 14 days, 6 for 11.5 days, 7 for 10 days, 8 for 8.5 days, 9 for 8 days, 10 for 7 days.

An extended example: The Misjump.
So, on a scout courier, 4 staterooms. I've got 4 PC's. THey have 4 weeks power plant fuel and 1j2 fuel, and stocked up on food, so have 8-person-weeks of food, and 20000 man-hours (119 person weeks) of LS filtration.
Lets do this in person days for LS (Reserve and Active) and Food (Fd), and ship-days of PP Fuel
RLS ALS _Fd _PP p/d
056 833 056 028 000 Day 0 - launch
056 829 052 027 004 Day 1 - out to jump point
056 801 024 020 028 Day 2-8 - jump (Misjump)
056 799 012 017 012 Days 9-11 - searching for fuel - got enough to jump.
056 771 –16 010 028 Days 12-18 - Jump again. *
056 767 –20 009 004 Day 19 head for that world with life **
056 759 030 007 008 Days 20 & 21 - hunting for throgs***
054 757 026 006 004 Day 22: Jumped by pirates. Pirates left, but PP & MD KO'd.****
042 757 014 006 012 Days 23-25: fixing PP. Eating cold carcases Air starting to get stale. 0G adaptation complete.
046 749 010 005 004 Day 26 fly back to "gardn" *****
056 727 060 028 012 Day 27-29 hunting.†
056 723 056 027 004 Day 30 to jump point
056 695 028 020 028 Day 31-37 Jump to habited system.
056 694 024 019 004 Day 38 Land at breathable world with TL3 E port.
056 694 800 028 000 Day 39-45: shoppie-store with the natives. Powered down. ††
056 689 795 027 005 Day 46: out to jump point. Stowaway aboard
056 654 760 020 035 Day 47-53: jump. Stowaway found day 7, spaced in jump.
056 650 754 026 004 Day 54: get bearings, head in. due to bad nav, plot is 25 days...†††
056 550 654 001 100 Days 55-79: Long burn in.
048 550 646 001 004 Days 80-81: Forbidden to land for 2 days due to religious festival††††
040 550 642 001 004 Day 81: 12 hour inspection †††††
056 546 638 000 004 Day 82: Landing. ‡

* Note everybody starves for 4 days.
** another day of starvation. Plenty of air and water, but no food.
*** They got lucky. The air is toxic, but the critters are edible. Slaughter occurs.
**** half day under power, half without. Note the reserve LS spent two days, and the active 2.
***** note that the LS system only supports 2 people per SR, and with 4 aboard, that's 4 of 8, the system goes into overdrive to replenish the air, spending 8 person days ALS, supporting the 4 for 1 day, and recharging the "reserve" by scrubing out another 4 person-days of accumulated CO2, aldehydes, keytones, and sulfurous bodily emmissions, as well as water.
† Note that 22 person-days of ALS spent, 12 on keeping 4 guys going 3 days, 10 more to get the atmosphere back to normal ( reset the reserve). Also note: they've turned the lower gallery into an abbatoir and freezer... and it's full of meat.
†† bought three dtons of food; 1 each grain, jerkies, and pickled veggies. Cost them a few thousand credits. BORING, but it will feed them for several months. PP is off, because local atmosphere is breathable, and they camp under the ship. They also load 10 DTons of processable liquids in barrels. Well, they hope to sell the stuff, but see following entries...
††† Remember the booze? They run it through the FPP. Gives them an extra 7 days fuel.
†††† They park in orbit, and shut down for two days, so the locals can have their festival. Sucks, but sometimes, that's the harshness.
††††† 12 hours of 8 goons aboard, breathing the air, but not eating. Plant still off to have fuel to land.
‡ Note that local air is breathable and fresh... so they just open the doors, set up the fans, and swap onboard for offboard, and thus reset the reserve.

Also: people need a set range of O2 levels, and CO2 levels. One CAN, if one expects to be shutting off power, ramp up the starting O2 levels, but one can only run the scrubbers so fast. More people than scrubber capability, and that Reserve of air is important... because you'll be burning it in addition to active LS.

 

[swest]

Very helpful! Thanks.

- s.west

 

[swest]

How does one, with a reasonable amount of effort, keep track of this while running a game?

 

[Solomani666]

Now let's see if we can do this calmly.

I also dislike MGT's rule about fuel lasting only 2 weeks, but I did write up a retcoon about it - fuel efficiency would go up with TL. My other way around it would be to say that it's two weeks manuever fuel, and calculate it by the M-Drive type.

In Traveller, the power plants and jump drives consume large amounts of fuel for the following reasons:

1. 4H reactors are used. (4 hydrogen atoms are fused to create 1 helium atom.) This is much less efficient then say a tritium-deuterium reaction. The primary reason for using these types of reactors is that unrefined fuel can often be obtained for virtually free and then processed.

2. The fuel is also used as a reactor coolant. And you can not reclaim the coolant without some sort of external radiators, which would increase the mass and cost of the ship and have the exact opposite effect if the radiators were used when in the line of site of a nearby star.

3. A huge amount of power (i.e. fuel) is needed to greate a singularity to enter jump space.

4. Hydrogen is also used to fill and expand the jump bubble. Fuel is also used to cool the ship from the thousands of degrees of temperature within the jump bubble. Reclaiming coolant in this scenario would be impossible without breaking the laws of thermodynamics.

5. Excellerating, then coasting to a destination increases the time greatly, thus increasing the time needed to cool the reactor, provide for ships power, life support, etc. Not really much of a savings. Not to mention that you will look like a derelict ship and become the bait for every pirate, corsair, and unscrupulous captain in the system!

A Type A Free Trader can operate and maneuver for 2 whole weeks on a meager 2 tons of fuel. This seems reasonable. You could just decrease it's carge capacity by 2 tons and increase its operational span to 4 weeks.

One could try to bypass these issues by usingthe rules for fission power plants, but the rules don't cover coolants, shielding, and meltdowns. Not to mention that a fission powered ship would show up on every pirates sensors like a lighthouse!

Another method around this could be the reintroduction of 'ultra refined fuel' (hydrogen doped with tritium) from CT that would halve the fuel consumption, at a cost of 1000cr per ton and gain the added benefit of leaving your fuel tanks radioactive...

 

[Solomani666]

I'm not sure this is really a valid way to do it - not because of any R00LZ, but sheer logic: you're not necessarily continuously "maneuvering" (running the M-Drive) - you could simply be accelerating to a 'comfortable' speed, and then 'going ballistic' for the middle part of your trip, and then accelerating again to match velocity with your destination. Admittedly, this isn't actually a LIKELY scenario; you'd want to spend as little time in transit as possible, and that will probably be accomplished by accelerating for half the trip, flipping, and accelerating to match destination velocity. Nevertheless, it IS a valid scenario, and that means that your "one week of maneuver fuel" is going to last longer than that.

On the other hand, power/fuel for OPERATIONS (life support, keeping the computers running, et cetera) IS something that is used continuously, and reasonably measured in terms of duration. About the only way you can reduce this is to shut down the ship and go into low berth (or emergency low berth) and just drain parasitic power to maintain the berths and maybe the computer in standby mode. A good move if you come out of misjump, or if your jump targetting turns out to be so poor that you end up in the outer Kuyper belt or the Oort cloud for your destination system.

(note: I use acceleration/accelerating in the physics sense of a change-in-velocity. Common usage would use 'decelerate' in the contexts that I have you matching the velocity of the destination.)

Not True

Actually you are accerating at maximum then turning around half way and decellerating at maximum to your destination, thus maximizing time and profits.

 

[Solomani666]

I did consider having PP fuel as coolant, but I think you can reuse coolant, can't you? So in the end I ditched fusion pps and instead used fission ones for my reaction drive campaign, all fuel is reaction mass, the fission drive replaces fuel at the annual maintenance.

All very real world, but not solving the issue, just ducking out ....

You can not reuse coolant without some way of cooling the coolant, and this requires you to add a bunch of stuff to your ship.
Standard drives use gravimetric thrusters and not reaction mass.
Fission reactor rules do not account for radiation (EVERYONE will see you!), coolants and meltdowns.

 

[Solomani666]

IMO, the "two weeks" is simply a standardized measure of fuel consumption. I lived in Germany for a year. While there, they didn't talk about fuel economy in terms of miles per gallon (or even liters per km). It was how much fuel the car used after travelling 100 km. Same thing, just multiplied by 100.

I think of Traveller's fuel notation as the same concept except that is measuring how many tons of fuel are used after 2 weeks at max speed. If the players are traveling slower or landing on a planet, I'd say the players should get a break and be allowed to consume fuel at a much lower rate of speed.

Ships use vectored movement, (acceleration and direction) which does not directly translate into a particular speed, or fuel consumption by distance travelled.