Carried Vehicles, Small Craft and Ships
- Thread starter far-trader
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mike wightman
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Smallcraft use less fuel for maneuver in CT than ships do.
That shuttle mentioned previously uses 2.85t of fuel per four weeks. The scout uses 20t per four weeks.
Note that these numbers are from second edition CT.
I'll have to go and check first edition (maneuver fuel use was different IIRC).
That shuttle mentioned previously uses 2.85t of fuel per four weeks. The scout uses 20t per four weeks.
Note that these numbers are from second edition CT.
I'll have to go and check first edition (maneuver fuel use was different IIRC).
far-trader
SOC-14 10K
For Bk 2 designs perhaps, but anything from Bk 5 on had it's own rules and I think treated all drives, small craft through ships the same.
And even there I think I've managed to re-create each of the Bk 2 small craft designs with Bk 5 rules within a reasonable degree.
And even there I think I've managed to re-create each of the Bk 2 small craft designs with Bk 5 rules within a reasonable degree.
far-trader
SOC-14 10K
As for the efficiency difference I think that's down to the difference between Bk 2 design and Bk 5 where Bk 5 seems much closer to the Bk 2 small craft designs that the ships. The old flip of tons for jump drives and maneuver drives between the two books, and the different fuel calculation for the power plants to explain the fuel amounts between small craft and ships.
Yeah, you've got to go back to CT Book 2, first edition: "All non-starships consume fuel at the rate of 10 kilograms (1/100th of a ton) for each G of acceleration for 10 minutes, regardless of mass or cargo carried."
This only matters if they kept the drives the same size when they changed the fuel rule. If they did, it might explain the discrepancy you've found.
mike wightman
SOC-14 10K
This is also more evidence that the ship ton was originally meant to be 1000kg rather than 14m^3... 
Hard to say for certain ... the terms mass and mass displacement are used interchangeably.
The fuel use adds to the confusion. The small craft numbers imply a kind of "almost" reaction drive; the M-drive seems to convert power plant output directly to some sort of thrust (possibly A-Grav) and the jump fuel is probably based on hull volume.
I say probably because the formula calls out mass, which may or may not mean mass displacement.
All academic, really. The inconsistencies don't effect play much and, as was pointed out, High Guard resolved all that. Sort of
The fuel use adds to the confusion. The small craft numbers imply a kind of "almost" reaction drive; the M-drive seems to convert power plant output directly to some sort of thrust (possibly A-Grav) and the jump fuel is probably based on hull volume.
I say probably because the formula calls out mass, which may or may not mean mass displacement.
All academic, really. The inconsistencies don't effect play much and, as was pointed out, High Guard resolved all that. Sort of
mike wightman
SOC-14 10K
Leaving High Guard to one side for the moment, since it is a different ship paradigm altogether , CT 1st ed. implied ships used reastion drives too for maneuvering
The type A drive combo is only 3 tons.
But in a ship 10 to 20 tons of fuel are required, while in a small craft this is reduced by a factor of up to ten (2nd edition - I notice that small craft fuel is higher in 1st. edition, 9 tons for a shuttle with 80t cargo and 30 passengers ).
Is the ship power plant operating at a greater output, so that more fuel/coolant are needed?
Is the small craft maneuver drive more efficient for some reason?
Are different types of drive used in small craft?
, CT 1st ed. implied ships used reastion drives too for maneuvering
The type A drive combo is only 3 tons.
But in a ship 10 to 20 tons of fuel are required, while in a small craft this is reduced by a factor of up to ten (2nd edition - I notice that small craft fuel is higher in 1st. edition, 9 tons for a shuttle with 80t cargo and 30 passengers
).Is the ship power plant operating at a greater output, so that more fuel/coolant are needed?
Is the small craft maneuver drive more efficient for some reason?
Are different types of drive used in small craft?
One guess: if you assume that, ton for ton, a ship has more systems to operate than a small craft does then more power would be required. The bridge, more involved life support, more weaponry, and computers would draw more power. Perhaps the fuel use was an attempt to account for this without going into the complexity of the EP system adopted later.
If, on average small craft have fewer secondary systems than more of the power generated can go directly to thrust. This would improve efficiency.
Well, the first edition Ship's Boat skill might provide another clue. There's some bits in there relating to planetary size that never made it to the second edition; almost as if the drives don't function properly in a field above one G.
On the other hand, a lot of this could be explained by editing slips or ideas that didn't gel and needed tweaking.
I'm not sure I follow you on ship fuel use for M-drives. Do you mean the bit about "288 accelerations" from the Starship Economics section?
mike wightman
SOC-14 10K
Yep, that's the bit
The Oz
SOC-14 1K
Bk2 small craft are more fuel-efficient than the smaller Bk2 starships, but their advantage goes away once you start looking at the bigger starships, as long as you remember to use strict Bk2 rules for power plant fuel requirements.
Assuming that Ken Pick is correct (and I think he is) and the "A" M-drive/PP combination is what powers the Ships Boat, Pinnace and Cutter, you get these fuel efficiencies, based on dividing the powerplant fuel carried by tons of thrust (assuming the "A" combination gives 200 "tons" of thrust). I include the Type R and two hypothetical J1, 1G ships for comparison.
Fuel efficiency in TRAVELLER small craft</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> Fuel Efficiency
Type Carried (fuel/ton thrust/4 weeks)
Ships Boat 1.8 .009
Pinnace 2 .01
Cutter 2 .01
Type S scout 20 .1
Type A trader 10 .05
Type R trader 10 .025
1000ton J1,1G 10 .01
5000ton J1,1G 10 .002</pre>[/QUOTE]So the efficiency of the small craft is only valid as long as you're comparing them to the smaller starships or to starships that do more than Jump-1 and so need bigger powerplants. As a side note, if you use Ken Pick's assumption about the "1/2A" drive for powering the Slow Boat and Slow Pinnace, their fuel efficiencies match those of the other small craft (except the Launch and Fighter). To get the Shuttle to match you have to assume that it gets 285 tons of thrust from its drive, which would be just enough to push the craft at 3Gs, which also matches. I suspect the reason the Launch doesn't match (its fuel efficiency is as bad as the Type A) is that it has the minimum size fuel tank (one dton) which gives it more fuel than it really needs.
Assuming that Ken Pick is correct (and I think he is) and the "A" M-drive/PP combination is what powers the Ships Boat, Pinnace and Cutter, you get these fuel efficiencies, based on dividing the powerplant fuel carried by tons of thrust (assuming the "A" combination gives 200 "tons" of thrust). I include the Type R and two hypothetical J1, 1G ships for comparison.
Fuel efficiency in TRAVELLER small craft</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> Fuel Efficiency
Type Carried (fuel/ton thrust/4 weeks)
Ships Boat 1.8 .009
Pinnace 2 .01
Cutter 2 .01
Type S scout 20 .1
Type A trader 10 .05
Type R trader 10 .025
1000ton J1,1G 10 .01
5000ton J1,1G 10 .002</pre>[/QUOTE]So the efficiency of the small craft is only valid as long as you're comparing them to the smaller starships or to starships that do more than Jump-1 and so need bigger powerplants. As a side note, if you use Ken Pick's assumption about the "1/2A" drive for powering the Slow Boat and Slow Pinnace, their fuel efficiencies match those of the other small craft (except the Launch and Fighter). To get the Shuttle to match you have to assume that it gets 285 tons of thrust from its drive, which would be just enough to push the craft at 3Gs, which also matches. I suspect the reason the Launch doesn't match (its fuel efficiency is as bad as the Type A) is that it has the minimum size fuel tank (one dton) which gives it more fuel than it really needs.
mike wightman
SOC-14 10K
Thanks for the analysis Oz
mike wightman
SOC-14 10K
I agree with this.
Another thing to consider is that the drives etc. for the small craft are probably maintained from the outside, so life support, grav plates, and acceleration compensaors may not be required on the small craft while they are on the ship - and these things need energy, hence the higher power plant output and greater fuel use.
If, on average small craft have fewer secondary systems than more of the power generated can go directly to thrust. This would improve efficiency.I'm in agreement with this as well.
I'd forgotten about that.
In 1st edition small craft can only safely take off and land on size 7 or less worlds.
To operate on worlds of size 8+ a roll of 9+ is required, DMs +2 per level of skill above 1 (you have to love the CT skill system
This suggests to me that the inertial reduction or null grav component of the maneuver drive struggles to cope in so small a craft.
Ships can allocate more power to their null grav modules and so don't have to worry about such things.
YMMV
Thanks for the replies Piper, it's always a help to bounce ideas around
