AnotherDilbert
SOC-14 1K
Two days is a lot more than "288 accelerations"...
The Bridge, Ship Size, and Hull Size
- Thread starter robject
- Start date
288 10-minute turns is 48 hours.
LBB2'77 used 10-minute turns.
LBB2'80 used 1000-second turns.
HG used 20-minute turns.
AnotherDilbert
SOC-14 1K
Yes, sorry, I used six minute turns.
So we've established that in LBB2'77, the 10Pn is at least 2 days (typical case of size 8 to size 8) and might be as much as slightly over 19 days (gas giant to gas giant, which might be an edge case in a universe without universally available onboard fuel processing) -- but in any case it's always 1 trip as a simplification.
And ships without maneuver drives (XBoat) did not even need a power plant.
And ships without maneuver drives (XBoat) did not even need a power plant.
This may well be where the 4-week fuel-requirement (that superceded the 1-trip requirement) came from. Add in transit time from the mainworld to the gas giant at each end (and call it 4 weeks total), and that allocation is effectively all you could use up in a single trip's acceleration without taking silly detours.
Then HG added the Pn=Jn requirement, which meant that the maximum power plant endurance had to cover an additional week...
AnotherDilbert
SOC-14 1K
I wouldn't go that far. We don't need a power plant to support the jump drive.
Strictly by RAW I do think we need a power plant:
But LBB2 was never applied that strictly by GDW, see the Xboat or the Annic Nova.
Perhaps we can say that you need a good excuse to omit the power plant?
I have defended the Xboat by saying it's arguably legal, not that it's definitely legal...
AnotherDilbert
SOC-14 1K
Agreed.
Likely they didn't consider it all that closely; we need some fuel, it covers a "trip", simple, done.
So, to sum up how I see the LBB2'77 rules in relation to fuel use and the maneuver drive:
Lower limit case: XBoat, no maneuver drive, needs no power plant even during jump.
Typical case: Fuel provides for at least the acceleration needed for a typical trip (size 8 to size 8). In this case, fuel burn is 3.5x the small craft rate (~35kg per G per turn vs. 10kg per G per turn).
Definitional case: Fuel provides for acceleration needed for any trip. (Assuming the small-craft burn rate of 10kg per G per turn, that's ~6 days of continuous acceleration)
Upper limit case: Fuel provides for the acceleration needed for a gas giant to gas giant trip. (~20 days continuous acceleration.)
The upper limit case is just a simplification of the definitional case, reducing the burn rate by a factor of about 3 to avoid the math of a burn-coast- deceleration calculation.
Lower limit case: XBoat, no maneuver drive, needs no power plant even during jump.
Typical case: Fuel provides for at least the acceleration needed for a typical trip (size 8 to size 8). In this case, fuel burn is 3.5x the small craft rate (~35kg per G per turn vs. 10kg per G per turn).
Definitional case: Fuel provides for acceleration needed for any trip. (Assuming the small-craft burn rate of 10kg per G per turn, that's ~6 days of continuous acceleration)
Upper limit case: Fuel provides for the acceleration needed for a gas giant to gas giant trip. (~20 days continuous acceleration.)
The upper limit case is just a simplification of the definitional case, reducing the burn rate by a factor of about 3 to avoid the math of a burn-coast- deceleration calculation.
AnotherDilbert
SOC-14 1K
Yes, but note that for starships the power plant consumes the fuel, not the M-drive, unlike non-starships:
AnotherDilbert
SOC-14 1K
To be petty, it requires less power, perhaps covered by a battery or something, not no power at all.
Or something tapping the waste heat from the jump drive...
.... and that's how you get to the "maneuver drive doesn't use much power" in High Guard, from the '77 fuel burn rules:
Step 1: fuel allocation is enough for the average trip's maneuvers as a minimum (2 days), but that's at 3.5x small craft burn rates.
Step 1a: fuel allocation is enough for 3.5 times the average trip's maneuvers at small craft burn rates (7 days).
Step 2: fuel allocation is enough for any plausible trip, as a handwaved simplification.
Step 3. Longest plausible trip (gas giant to gas giant) is almost 3 weeks (jump doesn't count).
Step 4: Because HG says it now includes the jump, the longest plausible duration is now 4 weeks.
Step 5: Maneuver for the average trip was only 2 days.
Therefore, maneuver is only 2/28 (~7%) of total power consumption.
At that point, HG'79 turning the reaction drives into grav drives justified the low fuel requirement, while simultaneously solving the "Hey, my Beowulf has a dual plasma gun turret pointing out the back for free!" problem for an army of annoyed referees.
Last edited:
The stats for nonstarship maneuver drives are identical to those of starship maneuver drives.
Note that maneuver fuel for book 2 gets added back in Beltstrike, but that also notes that the M-Drive includes shields....
This was a pretty severe thread drift, but I'll run with it for another step or two.
Assume that the LBB2'77 starship fuel burn rules were an extension of the small craft rules. That gives starships/nonstarships approximately 7 days of full acceleration -- a nice round figure that both coincides with Jump duration, and looks like "enough beyond the typical trip's requirement" that you don't have to keep track of it. Just assume it's always enough, and count it all as burned every trip and the variation will balance out over time.
This goes along with small craft often using what appear to be Size A drives (40Td pinnace at 5G, 50Td cutter at 4G, 30Td Ship's Boat at 6G -- if you round down...). They needed smaller fuel tanks (less than 10Pn) because they didn't need to do constant full acceleration for a week straight when used as interface craft for starships (which is exactly how they were presented in LBB2).
Assume that the LBB2'77 starship fuel burn rules were an extension of the small craft rules. That gives starships/nonstarships approximately 7 days of full acceleration -- a nice round figure that both coincides with Jump duration, and looks like "enough beyond the typical trip's requirement" that you don't have to keep track of it. Just assume it's always enough, and count it all as burned every trip and the variation will balance out over time.
This goes along with small craft often using what appear to be Size A drives (40Td pinnace at 5G, 50Td cutter at 4G, 30Td Ship's Boat at 6G -- if you round down...). They needed smaller fuel tanks (less than 10Pn) because they didn't need to do constant full acceleration for a week straight when used as interface craft for starships (which is exactly how they were presented in LBB2).
Now, bring in Beltstrike with its fuel burn rate that finally adjusted for ship tonnage, and we might be entering a HEPlaR-ier new era!
Last edited:
AnotherDilbert
SOC-14 1K
Nothing in Beltstrike suggests rockets, or that the m-drive consumes fuel or propellant, rather than just power from the power plant. I see something similar to powering down.
It just applies LBB5'80 fuel consumption to LBB2 ships for ridiculous endurance, ridiculously long for small ships and ridiculously short for large ships.
Last edited:
AnotherDilbert
SOC-14 1K
Yes, they use that sloppily for both ships and small craft, but in same sentence specifies small craft. Large non-starships use the starship design system, with the same drives and fuel consumption as starships.
LBB2 explicitly says ships consume fuel for the PP, but small craft consume fuel for the M-drive.
You are assuming a 5000 Dt starship would use the same reaction mass as a 20 Dt small craft, which would be a bit too much of a simplification for me...
mike wightman
SOC-14 10K
That could be due to null grav technology reducing inertial mass as well as gravitational mass
AnotherDilbert
SOC-14 1K
Jokes aside, there is no hint of inertia manipulating tech in Traveller.
mike wightman
SOC-14 10K
Inertial compensation says otherwise - besides, gravitic mass and inertial mass are the same thing until someone proves a patent clerk wrong.
