What house rules do you use, and how do you justify them within the ruleset you're working with?
Part of my list, mostly for LBB2 '81:
These are basically just my ways of mitigating LBB2's irrational power plant fuel use rule (10Td fuel per Pn) without discarding it outright. I suppose these could also apply to LBB5 power plant fuel, but the quantities involved in civilian ships are small enough that it doesn't matter. I probably wouldn't allow any of this for military ships (Pn 7+).
Amortized Power-Down:
The TCS/JTAS#14 power-down fuel use rule can be broken down into weeks and perhaps days or even hours, rather than whole months as written. That is, a Type S Scout/Courier on a Jump-2 trip, but limiting itself to 1G on the runs to and from the 100D limit, would only consume power plant fuel at the Pn=2 rate during the week in Jump, and at the Pn=1 rate during the transit to and from jump limit. Likewise, if it did the real-space part of the trip at 2G but only did a Jump-1, it's power plant would use fuel during the jump week at the Pn=1 rate (and Pn=2 rate for the rest of the trip). Computers that require Energy Points in LBB5 only need elevated power plant support during combat (ECM transmissions) and high-power active sensor use (that is, military/scout grade sensors doing active scanning).
This is partially justified within the context of LBB2: power plant fuel consumption rate for a given power plant is variable (it's based on hull tonnage and rating, rather than being directly based on power plant output as in LBB5 and pretty much every other version of Traveller). Yes, it's nominally a matter of efficiency in smaller ships, but it shows that it isn't always a fixed rate even in LBB2.
Referees should keep in mind that the power-down rule was intended to both enable ships that flee to the Outer System (in TCS campaigns) to stay out there for more than a single strategic turn (one week), while putting an upper limit to how long they can do so; and also to prevent them from doing so multiple times without refueling. If your players get themselves into a similar predicament with their ship, they only get one shot at coming in for fuel regardless of how they're managing their fuel use.
Also note that this enables building ships with high maneuver ratings in small hulls that would otherwise be impossible under LBB2. On the other hand, such ships are quite possible in LBB5, so it's not quite as disruptive as it may appear.
Yacht/XBoat Loophole:
Ships can be built with just a three- or two-week power plant fuel allocation (generally at the rated Pn, not powered-down as above) rather than the mandatory four weeks. Starships sharing the XBoat's mission profile (no maneuver, supported by tankers/tenders at both ends of a Jump) only need a one-week power plant fuel allocation. For XBoat types, keep in mind that a jump can last up to 10% longer than the nominal one week, so provide additional fuel to account for that.
If the fuel allocation is less than the mandatory four weeks (or three weeks plus a week for each Jump the ship can perform without refueling), the referee and players are going to have to track power plant fuel use instead of assuming there's enough to do everything the players want. It may cause problems for in-system trips to distant planets or in cases where the mainworld orbits within its star's 100D jump limit. If this house rule is combined with the amortized power-down house rule (see above), the result may look like LBB2 1st Ed. small craft maneuver burns or HEPlaR drive rules -- accelerate/coast/decelerate trips rather than the continuous acceleration/flip/continuous deceleration flights that are Traveller standard procedure. If you don't like math, don't do this.
This loophole exists because the canon Type Y Yacht can do two jump-1s with the rules-mandated four week power plant fuel allocation. This means that it could be doing the second jump with as little as two weeks of power plant fuel, but more likely three. The first case is with the standard "jump every other week" cadence, the second is with back-to-back Jump-1s to cross a two-parsec gap. Since only two or three weeks of fuel are needed for most trips, ships shouldn't be forced to carry far more fuel than necessary. [Edited to add: Also, while the canon XBoat is broken by the changes in LBB2 '81, it is possible to build J4/0G in 100Td under LBB2 '81 if it only needs 1 week of fuel for Jump rather than 4 weeks. Yes, the XBoat can be easily replicated in LBB5 '80, but canon doesn't indicate that it was, and doing so makes the use of LBB5 necessary rather than optional.] Again, with four weeks of fuel (or three weeks plus a week for each jump the ship can do without refueling), it's generally unnecessary to track power plant fuel use. If a ship has less than that, fuel use must be tracked. The narrower the margin of safety, the more closely it needs to be tracked. Don't like math and bookeeping? Don't use this loophole!
Optional low-math way to settle this:
There are four things that normally add to the duration of an interstellar trip:
- Origin mainworld orbits within it's star's 100D limit
- Destination mainworld orbits within it's star's 100D limit
- Refueling at origin from a gas giant (or origin mainworld orbits a gas giant)
- Refueling at destination from a gas giant (or destination mainworld orbits a gas giant)
A ship with the mandated 4-week power plant fuel supply available (jump fuel that's not used for the trip counts for this purpose) can ignore all of these issues -- it's presumed to have sufficient fuel even if the trip takes more than four weeks total. With three weeks of fuel, it can still make the trip if two of these issues are present (but if the issue is a gas giant at the destination, it must refuel again at the gas giant before departure because the trip from the gas giant to the mainworld uses a week of fuel). With only two weeks of fuel, it cannot make the trip if more than one of these issues apply.
Power Plant Fuel in Collapsible Tanks:
Allowed if there is at least an equal amount of permanent fuel tankage also installed (typically for Jump fuel). The problem is that a fuel hit to a collapsible tank takes out the entire tank rather than the 10% of tonnage or 10Td of a normal fuel hit. Therefore, a starship should keep at least two weeks of power plant fuel in permanent tankage. Standard practice is to shift fuel from the collapsible tank into main tankage as soon as the Jump fuel burn frees up the space for it -- this limits the vulnerability of the fragile collapsible tank to the outbound trip, rather than both sides of Jump. Also, it frees up space for passenger and crew use, if desired.
This is supportable because fuel can be transferred from collapsible tanks to main tankage faster than power plants can burn it, so there's no reason this shouldn't be possible.
This one mostly affects LBB2 standard hulls.
Fuel Processors in Drive Bay:
LBB5 fuel processors may be installed in unused drive bay space. If the processor is larger than the available space, the remainder of the processor is installed outside it.
Fuel processors should be able to be placed in the drive bay because they are drive-related equipment. Also, the implicit fuel refining for military/scout drives is in the drive bay by default.
It's not all about fuel!
LBB2 exceptions to LBB5 Tech Level Limits:
Starships using LBB2 drives can have the performance shown in the Drive Potential Table regardless of the LBB5 TL limits to Jump capability (note that drive TL is listed in LBB3). That is, they can if the necessary computer is available at that TL, and all the required components fit... (The first couple of house rules I've listed above make this a bit easier.)
This is just interpreting LBB5 as not rendering LBB2 completely obsolete. The other alternative is that LBB5 TL limits apply to LBB2 drives, making some canon ships higher TL than they would be according to LBB2 and LBB3.
I'm not sure I'd allow drop tanks in combination with this house rule for game balance reasons (explained in-universe as that these are prototype/experimental ships, and drop tanks add too much additional risk).
Part of my list, mostly for LBB2 '81:
These are basically just my ways of mitigating LBB2's irrational power plant fuel use rule (10Td fuel per Pn) without discarding it outright. I suppose these could also apply to LBB5 power plant fuel, but the quantities involved in civilian ships are small enough that it doesn't matter. I probably wouldn't allow any of this for military ships (Pn 7+).
Amortized Power-Down:
The TCS/JTAS#14 power-down fuel use rule can be broken down into weeks and perhaps days or even hours, rather than whole months as written. That is, a Type S Scout/Courier on a Jump-2 trip, but limiting itself to 1G on the runs to and from the 100D limit, would only consume power plant fuel at the Pn=2 rate during the week in Jump, and at the Pn=1 rate during the transit to and from jump limit. Likewise, if it did the real-space part of the trip at 2G but only did a Jump-1, it's power plant would use fuel during the jump week at the Pn=1 rate (and Pn=2 rate for the rest of the trip). Computers that require Energy Points in LBB5 only need elevated power plant support during combat (ECM transmissions) and high-power active sensor use (that is, military/scout grade sensors doing active scanning).
This is partially justified within the context of LBB2: power plant fuel consumption rate for a given power plant is variable (it's based on hull tonnage and rating, rather than being directly based on power plant output as in LBB5 and pretty much every other version of Traveller). Yes, it's nominally a matter of efficiency in smaller ships, but it shows that it isn't always a fixed rate even in LBB2.
Referees should keep in mind that the power-down rule was intended to both enable ships that flee to the Outer System (in TCS campaigns) to stay out there for more than a single strategic turn (one week), while putting an upper limit to how long they can do so; and also to prevent them from doing so multiple times without refueling. If your players get themselves into a similar predicament with their ship, they only get one shot at coming in for fuel regardless of how they're managing their fuel use.
Also note that this enables building ships with high maneuver ratings in small hulls that would otherwise be impossible under LBB2. On the other hand, such ships are quite possible in LBB5, so it's not quite as disruptive as it may appear.
Yacht/XBoat Loophole:
Ships can be built with just a three- or two-week power plant fuel allocation (generally at the rated Pn, not powered-down as above) rather than the mandatory four weeks. Starships sharing the XBoat's mission profile (no maneuver, supported by tankers/tenders at both ends of a Jump) only need a one-week power plant fuel allocation. For XBoat types, keep in mind that a jump can last up to 10% longer than the nominal one week, so provide additional fuel to account for that.
If the fuel allocation is less than the mandatory four weeks (or three weeks plus a week for each Jump the ship can perform without refueling), the referee and players are going to have to track power plant fuel use instead of assuming there's enough to do everything the players want. It may cause problems for in-system trips to distant planets or in cases where the mainworld orbits within its star's 100D jump limit. If this house rule is combined with the amortized power-down house rule (see above), the result may look like LBB2 1st Ed. small craft maneuver burns or HEPlaR drive rules -- accelerate/coast/decelerate trips rather than the continuous acceleration/flip/continuous deceleration flights that are Traveller standard procedure. If you don't like math, don't do this.
This loophole exists because the canon Type Y Yacht can do two jump-1s with the rules-mandated four week power plant fuel allocation. This means that it could be doing the second jump with as little as two weeks of power plant fuel, but more likely three. The first case is with the standard "jump every other week" cadence, the second is with back-to-back Jump-1s to cross a two-parsec gap. Since only two or three weeks of fuel are needed for most trips, ships shouldn't be forced to carry far more fuel than necessary. [Edited to add: Also, while the canon XBoat is broken by the changes in LBB2 '81, it is possible to build J4/0G in 100Td under LBB2 '81 if it only needs 1 week of fuel for Jump rather than 4 weeks. Yes, the XBoat can be easily replicated in LBB5 '80, but canon doesn't indicate that it was, and doing so makes the use of LBB5 necessary rather than optional.] Again, with four weeks of fuel (or three weeks plus a week for each jump the ship can do without refueling), it's generally unnecessary to track power plant fuel use. If a ship has less than that, fuel use must be tracked. The narrower the margin of safety, the more closely it needs to be tracked. Don't like math and bookeeping? Don't use this loophole!
Optional low-math way to settle this:
There are four things that normally add to the duration of an interstellar trip:
- Origin mainworld orbits within it's star's 100D limit
- Destination mainworld orbits within it's star's 100D limit
- Refueling at origin from a gas giant (or origin mainworld orbits a gas giant)
- Refueling at destination from a gas giant (or destination mainworld orbits a gas giant)
A ship with the mandated 4-week power plant fuel supply available (jump fuel that's not used for the trip counts for this purpose) can ignore all of these issues -- it's presumed to have sufficient fuel even if the trip takes more than four weeks total. With three weeks of fuel, it can still make the trip if two of these issues are present (but if the issue is a gas giant at the destination, it must refuel again at the gas giant before departure because the trip from the gas giant to the mainworld uses a week of fuel). With only two weeks of fuel, it cannot make the trip if more than one of these issues apply.
Power Plant Fuel in Collapsible Tanks:
Allowed if there is at least an equal amount of permanent fuel tankage also installed (typically for Jump fuel). The problem is that a fuel hit to a collapsible tank takes out the entire tank rather than the 10% of tonnage or 10Td of a normal fuel hit. Therefore, a starship should keep at least two weeks of power plant fuel in permanent tankage. Standard practice is to shift fuel from the collapsible tank into main tankage as soon as the Jump fuel burn frees up the space for it -- this limits the vulnerability of the fragile collapsible tank to the outbound trip, rather than both sides of Jump. Also, it frees up space for passenger and crew use, if desired.
This is supportable because fuel can be transferred from collapsible tanks to main tankage faster than power plants can burn it, so there's no reason this shouldn't be possible.
This one mostly affects LBB2 standard hulls.
Fuel Processors in Drive Bay:
LBB5 fuel processors may be installed in unused drive bay space. If the processor is larger than the available space, the remainder of the processor is installed outside it.
Fuel processors should be able to be placed in the drive bay because they are drive-related equipment. Also, the implicit fuel refining for military/scout drives is in the drive bay by default.
It's not all about fuel!
LBB2 exceptions to LBB5 Tech Level Limits:
Starships using LBB2 drives can have the performance shown in the Drive Potential Table regardless of the LBB5 TL limits to Jump capability (note that drive TL is listed in LBB3). That is, they can if the necessary computer is available at that TL, and all the required components fit... (The first couple of house rules I've listed above make this a bit easier.)
This is just interpreting LBB5 as not rendering LBB2 completely obsolete. The other alternative is that LBB5 TL limits apply to LBB2 drives, making some canon ships higher TL than they would be according to LBB2 and LBB3.
I'm not sure I'd allow drop tanks in combination with this house rule for game balance reasons (explained in-universe as that these are prototype/experimental ships, and drop tanks add too much additional risk).
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