LBB2 M-Drives in LBB5: When does it help?

[Grav_Moped]

It would immediately appear that you'd always want to use a LBB2 (second edition) maneuver drive in any ship built under LBB5, whenever you can.

There are some limits. The first is that LBB2 TL limits on maneuver drive power (Gs*Tons) are sharply constrained by TL, since LBB3 does not split out drive type (MD, JD, PP) by TL.

The second is that the main design penalty for maneuver drive capacity in smaller ships is the power plant fuel requirement.

The third is that if you're not intermixing drives, agility is almost invariably limited to a maximum of 5 since LBB2 power plants cannot have a rating higher than Pn-5, and computers larger than Mod/2 draw energy points.

A fourth is that TL affects LBB5 power plant size if you're intermixing LBB2 and LBB5 drives. I personally dislike the concept of intermixing them, as it's cherry-picking from systems with different underlying purposes.



I'll lay out some tables in subsequent posts, unless someone (hi, @AnotherDilbert!) wants to run them first.

 

[kilemall]

I’m not following some of these assertions.

The LBB3 tech limiter is for all engineering plant, want go faster cram it into a smaller hull within the available range.

You can put in a larger power plant then drives to get excess power for weapons and computers. There was already the double fire program so custom heavy hitter LBB2 combat ships would have extra power plant even before High Guard was a gleam in Miller’s eyes.

 

[Grav_Moped]

I’m not following some of these assertions.

The LBB3 tech limiter is for all engineering plant, want go faster cram it into a smaller hull within the available range.

You can put in a larger power plant then drives to get excess power for weapons and computers. There was already the double fire program so custom heavy hitter LBB2 combat ships would have extra power plant even before High Guard was a gleam in Miller’s eyes.

The LBB2 tech limiter is from the Technological Levels chart in LBB3'81 pp. 14-15, giving the TLs of the drives. That is, (to start with), the largest ship that can have 6G at TL-9 is 100Td because TL-9 only allows drives A-D (Size C is rating 6 in 100Td, only 4 in 200Td).

Putting in a larger power plant gets you double fire in LBB2. It does not get you any more energy points in LBB5 (beyond Pn=6) because the maximum drive rating in LBB2 is 6, and EP is Pn*Td/100. I mean, it should -- and I'd consider house-ruling that it does -- but that's not what the rules as written say.

 

[Grav_Moped]

First table:
Maximum rating by TL and hull size, LBB2'81 and LBB3'81:

Maximum Available Rating by TL and ship tonnage (LBB2):

TL/Tons 100   200  400  600  800 1000 2000 3000 4000 5000
09       6     4    2    1    1
10       6     6    4    2    2    1
11       6     6    5    3    2    2    1 
12       6     6    6    4    3    2    1
13       6     6    6    5    3    3    1    1 
14       6     6    6    6    4    3    1    1
15       6     6    6    6    6    6    6    4    3    2

So, a rating of 6 is possible for up to:
100Td at TL-9
200Td at TL-10 and 11
400Td at TL-12 and 13
600Td at TL-14
2000Td at TL-15 (there's your Z drives).

On the other end, the maximum hull that can use a LBB2 drive (rating of at least 1) by TL:
09: 800
10: 1000
11-12: 2000
13-14: 3000
15: 5000

If extrapolation is permitted:
TL-15 drives could have a rating of 1 in a 12KTd hull (Z for 4 in a 3000Td hull, x3)
(The extrapolations from lower-TL drives fall between the LBB2 tonnage breakpoints.)

 

[AnotherDilbert]

Yes, they are generally smaller if available due to size and civilisation TL.

But they are often more expensive than LBB5 M-drives; might occasionally not be worth it for civilians.

The really OP drives are the high-letter drives, such as Z-drives.

I wouldn't extrapolate Z-drive performance, lest we end up with Z6 drives doing 6 G in 12 kDt ships, or 2 G in 36 kDt ships, completely obsoleting LBB5 drives.

 

[Grav_Moped]

The really OP drives are the high-letter drives, such as Z-drives.

I wouldn't extrapolate Z-drive performance, lest we end up with Z6 drives doing 6 G in 12 kDt ships, or 2 G in 36 kDt ships, completely obsoleting LBB5 drives.

Why not? If that's what they can do, why not use them? Aside from neither LBB2 nor LBB5 allowing primary and backups to run simultaneously...

That is, the 12KTd value is just taking the rating*tons at 3KTd, and applying it to a higher tonnage. Nothing being added together, no additional rules needed, just scaling the drive's performance to a larger hull.

The TL-15 drives (W-Z) are overpowered because they had to fit the entire range into 24 columns (A-Z excluding i and o), and did so by tweaking those four drives' performance upwards. The only other variance from expected values in the Drive Performance Tables is the Size J drive in a 1000Td hull, and that's just rounded up by 10% to get a rating of 1 (allowing TL-11's Size J drives to reach the minimum necessary performance for a 2000Td hull*).



----------------------
*Wait. That may explain why my old "most efficient LBB2 ships" calculations have a sweet spot for that J-1 2000Td freighter...

 

[AnotherDilbert]

The drive's sizes are linear, but the ship size on the table is not, hence drive performance is not linear above 1000 Dt.

T5, where we can extrapolate performance, is linear on both axles of the table.

Example:

Drive     Performance     Size    Performance/Dt
A           200 G×Dt      1 Dt         200
B           400 G×Dt      3 Dt         133
C           600 G×Dt      5 Dt         120
...
T          3600 G×Dt     35 Dt         103
U          3800 G×Dt     37 Dt         103
V          4000 G×Dt     39 Dt         103
W          5000 G×Dt     41 Dt         122
X          6000 G×Dt     43 Dt         140
Y          8000 G×Dt     45 Dt         178
Z         12000 G×Dt     47 Dt         255

If you wanted to extrapolate from, say, D-V drives, I would have less of a problem...

A generic extrapolated LBB2 M-drive would be M × P / 100 - 1 Dt (just to make it complicated), i.e. 1% per G. Still about a third of the size of an LBB5 drive.

 

[Grav_Moped]

The drive's sizes are linear, but the ship size on the table is not, hence drive performance is not linear above 1000 Dt.

T5, where we can extrapolate performance, is linear on both axles of the table.

Example:

Drive     Performance     Size    Performance/Dt
A           200 G×Dt      1 Dt         200
B           400 G×Dt      3 Dt         133
C           600 G×Dt      5 Dt         120
...
T          3600 G×Dt     35 Dt         103
U          3800 G×Dt     37 Dt         103
V          4000 G×Dt     39 Dt         103
W          5000 G×Dt     41 Dt         122
X          6000 G×Dt     43 Dt         140
Y          8000 G×Dt     45 Dt         178
Z         12000 G×Dt     47 Dt         255

If you wanted to extrapolate from, say, D-V drives, I would have less of a problem...

Actually, it is linear through Size V, with one exception.
1. Assign each letter (skipping i and o) an ordinal value (1-24).
2. Multiply that ordinal value by 2 to get a Ratings Point value (like an Energy Point in LBB5).
3. Divide the Ratings Point value by (Td/100) for each hull size in the Drive Potential table in LBB2'81, rounding down.
4. This will match the corresponding drive potential value in the Drive Potential table for all listed hull sizes except as noted below:

Exceptions:
Size J in 1000Td (18 RP calculated, table shows rating 1 which would require 20 RP).
Size W: 1000Td should be (hereafter, "s/b") 4.2, is 5; 5000Td s/b 0.84, is 1
Size X: 800Td s/b 5.5, is 6; 1000Td s/b 4.4, is 6; 2000Td s/b 2.2, is 3; 3000Td s/b 1.467, is 2; 5000Td s/b 0.88, is 1
Size Y: 800Td s/b 5.75, is 6; 1000Td, s/b 4.6, is 6; 2000Td s.b 2.3, is 4; 3000Td s/b 1.533, is 2; 4000Td s/b 1.15, is 2; 5000Td s/b 0.92, is 1
Size Z: 1000Td s/b 4.8 is 6; 2000Td s.b 2.4 is 6; 3000Td s/b 1.6 is 4; 4000Td s/b 1.2 is 3; 5000Td s/b 0.96 is 2

 

[Grav_Moped]

Actually, it is linear through Size V, with one exception.

The pattern of exceptions for the TL-15 drives (and that it is a pattern of exceptions for the TL-15 drives, and not hull tonnage) is hidden by having drive TLs in a separate book, and the fact that Size V drives don't provide even a rating of 1 in 5000Td hulls so direct comparisons are harder.

 

[infojunky]

Putting in a larger power plant gets you double fire in LBB2. It does not get you any more energy points in LBB5 (beyond Pn=6) because the maximum drive rating in LBB2 is 6, and EP is Pn*Td/100. I mean, it should -- and I'd consider house-ruling that it does -- but that's not what the rules as written say.

Note with a little math one can do power plants by the number of EP they produce. In that if you set the Tonnage to 100 and the performance to 1, the Drive percentage effectively becomes the power plants tonnage in terms of EP.

 

[Grav_Moped]

Note with a little math one can do power plants by the number of EP they produce. In that if you set the Tonnage to 100 and the performance to 1, the Drive percentage effectively becomes the power plants tonnage in terms of EP.

I think you're addressing this from a different angle.

If you want EP by drive tonnage from LBB2'81, the formula is a little bit complicated.
For EP of 40 and lower (except 20EP in 1000Td hull per LBB2, which is treated as 18EP for tonnage calculations):
LBB2 power plant tonnage is (1.5% of hull tonnage per EP)+1Td
Restated, that's 1Td plus 1.5Td per EP.

They cost MCr4 per EP, regardless of size.

Note that this does not hold for EP>40 (size W+) in many cases. Refer to the Drive Potential Table in LBB2 for actual values.

Also note that this yields power plants as small as (size A) or smaller than (all others) LBB5 power plants up to TL-14. Fuel use per EP is higher until 1000Td. Cost per EP is lower than LBB5 power plants until TL-15.

The other consideration is the size of the power plant plus its fuel allocation. I'll address this in a subsequent post unless someone beats me to it.

 

[infojunky]

They cost MCr4 per EP, regardless of size.

Note that this does not hold for EP>40 (size W+) in many cases. Refer to the Drive Potential Table in LBB2 for actual values.

The problem is that there are different rounding systems involved with at least three different but related systems for design.Though the choice of the 2nd edition of book5 is for cause that it is the only one with EP.

Note 1st ed book5 has no EP, and it has max power plant of 6.

So the real question becomes do EP matter?

 

[Grav_Moped]

So the real question becomes do EP matter?

They only do if you're using a LBB2 ship in LBB5'81 combat.
Within LBB2 itself, not really. Agility isn't a thing in LBB2, so as long as Pn=Gs or Pn=Jn whichever is higher, they don't -- with the notable exception that a PP of one letter (not rating) above that needed to support Pn=Gs allows double-fire if that program is running, and that's not really a matter of EPs anyhow.

I'm only using them here as a proxy for output power (and using analogous "rating points" for the other drive types).

 

[infojunky]

They only do if you're using a LBB2 ship in LBB5'81 combat.
Within LBB2 itself, not really. Agility isn't a thing in LBB2, so as long as Pn=Gs or Pn=Jn whichever is higher, they don't -- with the notable exception that a PP of one letter (not rating) above that needed to support Pn=Gs allows double-fire if that program is running, and that's not really a matter of EPs anyhow.

I'm only using them here as a proxy for output power (and using analogous "rating points" for the other drive types).

Now that is the crux of the issue what does rules set you are using require.

I kinda like the idea of EP for rating the International energy requirements of ships. Thus how many EP does it take to drive the Maneuver drive, i.e. Agility.

And quite honestly I tend to rewrite the "standard" drives in a linear fashion. and use Ken Pick's Multiple drives for larger ships.

 

[kilemall]

Assuming you are using LBB5 81 and translating power plant number as EP, M-6 is not precluded, just full maneuver and powered weapons/higher order computer at the same time.

I would tend to calculate LBB2 to LBB5 Pn between levels for double fire extra power as a percentage. So say a line for a particular tonnage has 5 at minimum, 5 as extra for double fire then 6 would be 5.5 for the extra power level.

IMTU I tend to use capacitors pretty liberally. So a fighter that has say .1 dton devoted to a weapons capacitor would have 3.6 EP storage available for firing lasers. Lasers have to use the capacitor not power plant directly, they get charged a few turns before combat.

 

[mike wightman]

LBB2 - 77, 81, Starter
HG79, HG80
MT
TNE - FF&S, BL
T4 - Starships, T4QSDS, FF&S
T5
and then
GT Starships, Vehicles
GT:ISW
T20
HT
Ever notice how it all keeps coming back to LBB2 vs HG80? After forty plus years...
Back to the OP.
A HG80 jump drive is always smaller and cheaper, so you always go with a HG jump drive unless TL constrained.
For m-drive you always go for a LBB2 since they are also always smaller and usually cheaper (they sometimes cost a little more but you have to weigh up what you do with the reclaimed space since you can carry more cargo or passengers and thus more revenue).
Power plant is the interesting bit - you really need to consider pp+fuel as a unit and compare totals with regards to cost, tonnage and what you intend to do with the saved space.

And then there is the EP issue - how many EPs do you get from a letter drive since its number rating varies by hull size.

Take an X drive power plant

hull tonnage	800	1000	2000	3000	4000	5000
EP generated	48	60	60	60	40	50

 

[AnotherDilbert]

Ever notice how it all keeps coming back to LBB2 vs HG80? After forty plus years...

Presumably the level of detail (i.e. not much) is appreciated. It's quick and easy to build ships.

MgT is doing some things well, with similar level of detail, but with more payload options, i.e. not just "staterooms" and "cargo".

A HG80 jump drive is always smaller and cheaper, so you always go with a HG jump drive unless TL constrained.

For small drives, not large drives. As usual a Z-drive is much smaller and cheaper than a LBB5 drive, but even mid-letter drives are (slightly) cheaper.

If your ship is not exactly the right size for a LBB2 drive (e.g. 300 Dt), a LBB5 drive is probably better. The Drive Potential Table is a straitjacket for ship design.

For m-drive you always go for a LBB2 since they are also always smaller and usually cheaper (they sometimes cost a little more but you have to weigh up what you do with the reclaimed space since you can carry more cargo or passengers and thus more revenue).

LBB5 drives can be quite a bit cheaper, but I agree LBB2 drives are generally worth it.

Power plant is the interesting bit - you really need to consider pp+fuel as a unit and compare totals with regards to cost, tonnage and what you intend to do with the saved space.

Quite, this varies wildly with size of ship and TL.

 

[rlmercad069]

Where does it say one can mix and match construction rules?

 

[AnotherDilbert]

Where does it say one can mix and match construction rules?

LBB5'80, p22:
Drives: Three types of drives are required for starships– maneuver drives, power plants, and jump drives. Non-starships may omit the jump drives. Some ships (such as express boats) omit the maneuver drives. All ships require power plants. Custom- built drives must be produced and installed while observing restrictions as to tech level and interior space. It is possible to include standard drives (at standard prices) from Book 2 if they will otherwise meet the ship's requirements; such drives use fuel as indicated by the formulas in Book 2.

 

[kilemall]

Where does it say one can mix and match construction rules?

More importantly, who cares?

Only important point is for published product, which is past its expiration date by decades.

So we’re talking tastes not RAWLAW.