Fractional drives

[Spinward Flow]

The key issue is that (maneuver drive Gs * tons) must be greater than 200.

And that's just a foundational flaw built into the table's design.

I get the feeling that the first draft of this was drawn up with the notion that 100 tons would be the absolute minimum "floor" for tonnage (so why bother with anything fractional below it) coupled with the rule that if a hull size falls "between" any of the rows on the table, just "round up" on hull tonnage to comply with the table outputs (so a 300 ton ship uses the 400 ton row on the table for drive performances) in LBB2.

Within the limits of what was being attempted at the time when LBB2 was first written, that "worked" (more or less) ... but as soon as people start tearing into the system wanting to do "clever stuff" with it, the bare bones skeleton of the fundamental design work get exposed as the halfway measures that they are. One of those "pay no attention to the man behind the curtain!" kinds of realizations.

In other words, the lower bound of the table chart used in LBB2 was not located in a "good place" to handle cases beyond what the table explicitly detailed. So long as you stay "IN" the table's bounds, that's fine ... but all kinds of things break when you try going beyond the bounding limits of what the table details. Sure, you can extrapolate things ... but those extrapolations wind up being house rules rather than official "canon" RAW.

 

[Silverhawk]

This concept is similar to adding cylinders to the motor (2-4-6-8), or rotors in a Rotary motor.

But even still, while there are V-12, even V-16 motors, they're more a novelty.

It's a lot of trouble to engineer these things, and there's only real economy in scaling the operations.

Most V-12, V-16, even V-20 () are diesel used in industrial and heavy transportation applications such as locomotives. But as was discovered by railroads the bought the V-20 SD 45 in the 1960's the fuel use did not equate to the advantage of the extra cylinders and horsepower. Thus it was that the V-16 model SD 40 and follow on SD 40-2 sold much better.

 

[infojunky]

It is a set function, I just think it's a little dinked, From LBB 2, The J-drive and Power plant are (drive size number) * (number)+(number)
Jump drives are (5*drive size number) + 5, so {10,15,20,35....} etc.
Power plants are (3*drive size number) +1 so {1,4,7,10,13...} etc
Maneuver drives are (2*(drive size number -1)) +1 so {1,3,5,7...} etc

Honestly I would rearraign the numbers to be more in line with High Guard. With a set of "Standard" drives derived from those number laying atop the cleaned up function.

 

[Spinward Flow]

Honestly I would rearraign the numbers to be more in line with High Guard. With a set of "Standard" drives derived from those number laying atop the cleaned up function.

BURN THE HERETIC!!!

*ahem*

I mean ... what a brilliant idea!
Why didn't I think of that ...

 

[spank]

Honestly I would rearraign the numbers to be more in line with High Guard. With a set of "Standard" drives derived from those number laying atop the cleaned up function.

It's a little more complicated than just cleaning up, or re-arranging the numbers the two functions are a little different
LBB 2 = ((2.5% * JN)*HULL)+5 TONS
LBB 5 = ((1% *JN)+1%)* HULL


So a LBB 2 drive will always be large than a LBB 5 drive.
Not because of the +5 tons, because JN progresses in 1% increments in HG and 2.5% increments in LBB2.
I think the simplest fix is to make High Guard drives follow the same progression, and add +5 tons to all drives for hulls below 10,000 tons.

 

[Spinward Flow]

I think the simplest fix is to make High Guard drives follow the same progression, and add +5 tons to all drives for hulls below 10,000 tons.

You only have that luxury of thinking if you're looking at the jump drive exclusively (in a vacuum? ).
As soon as you plug the maneuver and power plant drives into the mix, you will rapidly discover that there is an error underlying your assumptions.

In LBB2, jump drives are large while maneuver drives are small and power plants are sort of middling.
In LBB5, jump drives are small while maneuver drives are large and power plants are big at TL=9-12, middling at TL=13-14, and small at TL=15.

The two paradigms do NOT neatly converge upon each other in a convenient way.
And then there's the fuel formula discrepancy piled onto that bonfire of the vanities.

Simplest example I can provide for this is a J3/M3/PP3 combination in a 400 ton hull form factor.

LBB2.81
Jump: F = code: 3, 35 tons, MCr60, TL=10
Maneuver: F = code: 3, 11 tons, MCr24, TL=10
Power Plant: F = code: 3, 19 tons, MCr48, TL=10
Fuel: 150 tons (120+30)
Combined Tonnage: Drives (35+11+19=65 tons) + Fuel (120+30 tons) = 215 tons
MCr124

LBB5.80
Jump: 3 = 16 tons, MCr64, TL=12
Maneuver: 3 = 20 tons, MCr10, TL=8+
Power Plant: 3 = 36 tons, MCr108, TL=9-12
Fuel: 132 tons (120+12)
Combined Tonnage: Drives (16+20+36=72 tons) + Fuel (120+12=132 tons) = 204 tons
MCr182

The difference in combined tonnage is "close" at a difference of a mere 11 tons ... but the build cost is +47% higher for the custom LBB5.80 drives (mainly due to the cost of the power plant in that tech level range).

Also note that you can build a J3 starship at TL=10 using LBB2.81 drives in a 400 ton form factor ... while you have to wait until TL=12 to be able to build a J3 starship with custom LBB5.80 drives.



What this means is that in the TL=9-12 range for starships 600 tons and under, if you want high performance drives you'll often times be able to achieve jump ratings at lower tech levels with standard drives than you can with custom. You'll basically be paying a tonnage penalty for the privilege, but being able to get up to J4 in a 400 ton form factor at TL=10 is nothing to sneeze at (assuming the polity has "unlocked" J4 potential for the industrial base).

The two systems DO NOT RECONILE "nicely" with each other, since they approach the problem from completely different angles and fundamental understandings.

 

[Grav_Moped]

In other words, the lower bound of the table chart used in LBB2 was not located in a "good place" to handle cases beyond what the table explicitly detailed. So long as you stay "IN" the table's bounds, that's fine ... but all kinds of things break when you try going beyond the bounding limits of what the table details. Sure, you can extrapolate things ... but those extrapolations wind up being house rules rather than official "canon" RAW.

You can extrapolate down if you run with the '77 rules, sort of. The implication of the constant terms in the power plant and maneuver drive formulae cancelling each other out, and that the only use for the power plant was to support the maneuver drive (other power draws were handwaved, hence the XBoat), is that "small craft drives" -- a combination of the maneuever drive and power plant -- are actually linearly proportional to the craft's tonnage. That is, you scale down the maneuver drive by bundling it with the power plant before doing the downscaling. The "power plant component" of this "small craft drive" then only supports the maneuver drive and nothing else (ok, avionics and life support too, but that's it).

The update for LBB2 '81 (and LBB5 '79 by implication) would be to require an additional power plant to support anything beyond the maneuver drive, that's sized based on the implicit formula in the drive performance table. The only issue with this is the requirement for 10pn Td power plant fuel reserve. Cut the fuel burn rate to something that's both a bit smaller and proportional to craft/ship tonnage, and you're set.

 

[spank]

You can extrapolate down if you run with the '77 rules, sort of. The implication of the constant terms in the power plant and maneuver drive formulae cancelling each other out, and that the only use for the power plant was to support the maneuver drive (other power draws were handwaved, hence the XBoat), is that "small craft drives" -- a combination of the maneuever drive and power plant -- are actually linearly proportional to the craft's tonnage. That is, you scale down the maneuver drive by bundling it with the power plant before doing the downscaling. The "power plant component" of this "small craft drive" then only supports the maneuver drive and nothing else (ok, avionics and life support too, but that's it).

The update for LBB2 '81 (and LBB5 '79 by implication) would be to require an additional power plant to support anything beyond the maneuver drive, that's sized based on the implicit formula in the drive performance table. The only issue with this is the requirement for 10pn Td power plant fuel reserve. Cut the fuel burn rate to something that's both a bit smaller and proportional to craft/ship tonnage, and you're set.

You can certainly extrapolate downward, I think the bigger problem is that the M-drives are too small at the low end of the scale.
I think either,
a) All maneuver drives should be 2 tons heavier,
or
b) The very smallest drives should be 1 ton, and blended into the existing size charts sort of like what I did. M-drive a would be 2 tons.

 

[Grav_Moped]

You can certainly extrapolate downward, I think the bigger problem is that the M-drives are too small at the low end of the scale.
I think either,
a) All maneuver drives should be 2 tons heavier,
or
b) The very smallest drives should be 1 ton, and blended into the existing size charts sort of like what I did. M-drive a would be 2 tons.

The thing about LBB2 maneuver drives is that I'm pretty sure they were literally meant as "rocket nozzles" for the fusion power plant in the '77 rules; as such, the power plant and the fuel were the constraint on how many Gs you could give a ship. LBB5 '79 formalized this with the rule allowing the use of maneuver drive exhaust as a weapon, then the '80 edition undid that because giving a party of murderhobo PCs a 500MW plasma gun to play with tends to end badly for everyone.

So, they changed the technobabble describing maneuver drives without actually changing the drives themselves. So, yes, they probably should be larger. LBB 5 does that.

One quibble I have with LBB 5 is that while there's diminishing returns on increasing the size of maneuver drives (4G takes more than twice as many tons of drives as 2G does), the input power to the drives doesn't scale with the drive tonnage (4G takes exactly twice as much energy as 2G does).

 

[spank]

because giving a party of murderhobo PCs a 500MW plasma gun to play with tends to end badly for everyone.

Ha! I can certainly see how that could go very wrong.
But G-drives seem more futuristic than high energy plasma, so I guess that's a win.

One quibble I have with LBB 5 is that while there's diminishing returns on increasing the size of maneuver drives (4G takes more than twice as many tons of drives as 2G does), the input power to the drives doesn't scale with the drive tonnage (4G takes exactly twice as much energy as 2G does).

Leaving aside the +5 tons for LBB J-drives and the -1 ton for M-Drives LBB2 has a linear progression, just like HG, But the M-Drive and J-Drive progressions are almost exactly the opposite between HG and LBB2, IMHO the simplest change to bring the two system closer is to swap the maneuver and jump drive formulas in HG.

 

[Grav_Moped]

Ha! I can certainly see how that could go very wrong.
But G-drives seem more futuristic than high energy plasma, so I guess that's a win.

Leaving aside the +5 tons for LBB J-drives and the -1 ton for M-Drives LBB2 has a linear progression, just like HG, But the M-Drive and J-Drive progressions are almost exactly the opposite between HG and LBB2,

That's an artifact of LBB5's ship design rules' purpose: it's a space combat game, rather than a role-playing game. In LBB5, jump drives are just how you get ships into the same place to shoot at each other, a way to break off combat, and a place to stuff extra energy your black globe absorbs. Secondary importance. In LBB2, they're how you get from World A to World B. Very important.

The other thing about Jump Drives is that fuel is the big constraint, not drive size; Jump-2 in a Far Trader is 55Td (40 of which is fuel) not counting the power plant, the same with HG is 46Td (40 of which is fuel) -- the difference mostly goes away in larger ships. This wouldn't be that much of a problem except LBB5 introduced drop tanks... which make the difference in drive sizes a lot more significant.

 

[spank]

That's an artifact of LBB5's ship design rules' purpose: it's a space combat game, rather than a role-playing game. In LBB5, jump drives are just how you get ships into the same place to shoot at each other, a way to break off combat, and a place to stuff extra energy your black globe absorbs. Secondary importance. In LBB2, they're how you get from World A to World B. Very important.

Which is most likely why the M-Drives are much bigger in HG, they will play a far greater role than the Jump drives. You want to do 6 Gs? it's gonna cost you.
Still I think it should be possible to integrate the two rather than having two separate systems. If you want to have M-drive be larger in big ships, Jump drives be smaller then you need to find a cut-off and have the scales merge at that point. Maybe 10,000 tons.
Ships below 10,000 are designed with LBBs rules, and above 10,000 with HG rules. 10,000 ton ships are the same either way.

 

[Condottiere]

It's always an interesting exercise, if you have the time.

It's seems to be balancing design with possible performance and competing hull volume, which is why Classic required more tonnage per acceleration factor, and Mongoose about a third.

 

[mike wightman]

I have argued for decades that the authors of HG got the maneuver drive and jump drive tables flipped somehow.

Note you can not just compare m-drive and j-drive, the pp has to be included as well

Run the numbers for j-d LBB2 and m-d + pp for LBB2 as was the original intent of LBB2.

79 HG then coupled j-drive to pp and m-drive to pp (pp % is not TL dependent in 79 as it is in 80 - it is a flat 1-6%)

 

[spank]

79 HG then coupled j-drive to pp and m-drive to pp (pp % is not TL dependent in 79 as it is in 80 - it is a flat 1-6%)

I do like that High Guard has powerplants change size by TL, but it creates a few problems. Mainly, as you noted, powerplants are strictly a function of hull size, and output. But it is untethered from the Jump drives, there is no power consumption by jump drives, only fuel consumption.
To mate the two ideas you would have to come up with a power consumption table for Jump drives.
Or a progression table for Powerplant ratings.similar to the one in HG for Jump drives and Maneuver drives.

 

[whartung]

They are and they aren't, derated engines can provide more power than they are rated for with the proviso that the supporting hardware is up to snuff. It's not uncommon for a engine to be beefier than one would expect for it's rated power band, with looks towards durability or ease of manufacture and similar factors.

Indeed. I have one in my motorcycle. It's an "850cc" motor with "750cc" electronics. The mechanicals are identical between the two.

Also, in my Jeep, when cruising at highway speed, it's my understanding that 1/2 of the cylinders are cut out to improve gas mileage.

That said, the differences between the 750 and 850 is about < 20% more power for the 850. And it kind of goes to my point.

Clearly the reasons behind the same motor with different outputs are cost and engineering controls, combined with market segment details.

It's a single motor that the bikes are designed around, and then tuned for the application. Rather than running individual motors with specific spare part, support, and supply issues.

This is their second foray into this space. The previous generation 700/800 series also used the same motor. And it's the magic of modern engine management electronics and software that makes it possible and practical.

We also see this in cars. How may cars share the same motor in different states of tune? The generic GM Chevy 350 was used in everything, from docile family sedans to firebreathing muscle cars. Same fundamental motor, with different fuel systems and perhaps higher rated parts.

But this is different from a "input performance, get mass and fuel consumption" formula system. It just scratches the surface of powerplant development and engineering.

Now, that said, it perhaps would be nice to have the "standard powerplant" designs ala Book 2, but perhaps an ability to add a "tuning modifier". Give engineers the ability to squeak out an extra .1 or .2 G out of the M-drive.

Run a smaller plant, "supercharged", in a larger ship.

 

[Condottiere]

Balance is demonstratively proven by having starships designed with engineering in triplicate factors, whether one, two, three, or even four.

 

[Grav_Moped]

Which is most likely why the M-Drives are much bigger in HG, they will play a far greater role than the Jump drives. You want to do 6 Gs? it's gonna cost you.
Still I think it should be possible to integrate the two rather than having two separate systems. If you want to have M-drive be larger in big ships, Jump drives be smaller then you need to find a cut-off and have the scales merge at that point. Maybe 10,000 tons.
Ships below 10,000 are designed with LBBs rules, and above 10,000 with HG rules. 10,000 ton ships are the same either way.

When ships get big enough, the +5Td/+1Td/-1Td constants in the size formulae disappear in the noise and it becomes essentially a straight percentage. It's the percentage part where the tweaks ought to happen.

Note: I thought this posted last night. Evidently I neglected to press the button....

 

[Grav_Moped]

I have argued for decades that the authors of HG got the maneuver drive and jump drive tables flipped somehow.

Note you can not just compare m-drive and j-drive, the pp has to be included as well

Run the numbers for j-d LBB2 and m-d + pp for LBB2 as was the original intent of LBB2.

79 HG then coupled j-drive to pp and m-drive to pp (pp % is not TL dependent in 79 as it is in 80 - it is a flat 1-6%)

IMO it was a deliberate flip that they didn't think through. Adding Pn=Jn -- which happened in HG '80 before it did in LBB2 '81 -- means tech level affects the tonnage needed for Jump too. On the other hand, most of the tonnage requirement for Jump is in the fuel tankage, and drop tanks mitigate that factor.

Part of this is the underlying notion that Gs up to Jn are mostly included in sunk costs for the jump capability. In LBB2 '77, having only 1G in the A2 Far Trader was a big cost and tonnage savings over having 2G (needed to upgrade power plant too, and add 10Td fuel). In LBB2 '81, the savings weren't worth the reduced performance (only upgrade cost was for the M-Drive, since the larger power plant and fuel were already present).

In LBB5, the power plant is a big chunk of the drive bay, especially at lower TLs.

 

[Grav_Moped]

IMO it was a deliberate flip that they didn't think through. Adding Pn=Jn -- which happened in HG '80 before it did in LBB2 '81 -- means tech level affects the tonnage needed for Jump too.

Big Eureka! energy here: This is where the idea for the power plant burning all the jump fuel instead of the jump drive itself doing so, originated. Unlike LBB2 '77 jump drives, the small jump drives of LBB5 are meant to be just the field generators and not include the hot/inefficient power plant inside the jump drives of the LBB2 '77 rules (and carried forward into the '81 rules for backward compatibility).