The Xboat is a HG2 design

[mike wightman]

Where I'm coming from is that I see the rules as describing the game universe, rather than defining it. '77 describes a different universe from that which '81 does.

This is where you are "going wrong". The setting doesn't stick to the rules as written. So things are possible in the setting that
are not in the rules
contradict the rules
break the rules
and often are mutually inconsistent to boot

 

[Condottiere]

Rules must not only be done, but must also appear to be done.

 

[mike wightman]

Annic Nova, xboat, Gazelle, jump torpedo, different TL paradigm between LBB1-3 and the OTU - yup rules applied as written NOT.

 

[Grav_Moped]

This is where you are "going wrong". The setting doesn't stick to the rules as written. So things are possible in the setting that
are not in the rules
contradict the rules
break the rules
and often are mutually inconsistent to boot

Objectively, and in detail, that's absolutely true. This is simply because of the manner in which the setting and rules were written and re-written over time.

 

[Grav_Moped]

Annic Nova, xboat, Gazelle, jump torpedo, different TL paradigm between LBB1-3 and the OTU - yup rules applied as written NOT.

The first four were valid (or broken in non-obvious ways) in the rules systems under which they were designed. The breaks came from converting them forward into later rules (except for j-torps -- those were just incompatible with the new rules, in addition to messing up the setting).

The shift in TL paradigm was the LBB2->LBB5 shift.

In an ideal game-design world unconcerned with canon or the player base (market), the '81 rewrite of LBB2 aligns its build system with HG'80* and the trade mini-game gets worked over by a few Econ undergrads to match the changed ship capabilities.

For valid reasons, this did not happen.

‐----------------
* perhaps with letter drives that are point cases of the HG formulae, for old-times' sake.

 

[Condottiere]

One off artefacts and relics are rules plus, and generally okay.

Jump torpedoes are more a question of clarifying jump transition requirements.

Engineering was deconstructed.

 

[Grav_Moped]

Jump torpedoes are more a question of clarifying jump transition requirements.

In large part, it was a matter of revising the equipment requirements.

Under '77 rules, Jump didn't require a power plant (under a plausible rules interpretation enabling the XBoat), and only required enough computer space to run the programs, not a specific computer model. Further, everything about Jump happened before or at Jump time. (Mongoose retained a lot of that in their take on the rules.)

So, offload the navigation stuff to the host ship -- have it run Navigate/Generate and record a jump tape for the torp and you don't need a computer.

Build the J-torp from the LBB2 formula: J-drive is 2.5% of total Td (M) per Jn plus 5 Td, J-fuel is 10% per Jn; the message recorder/radio transmitter and the jump tape player are of negligible size and cost compared to the rest of it. Roughly, total tonnage M is going to be M=(0.125*M*Jn)+5 tons. Drive cost is extrapolated from the table, and is by capability rather than per ton of drives.

Solving that for Jn=1-6 yields the following:
J-1: 5.7Td, MCr 0.857, uses 0.57 tons of fuel.
J-2: 6.67Td, MCr 1.333, uses 1.33 tons of fuel
J-3: 8Td, MCr 2, uses 2.4 tons of fuel
J-4: 10Td, MCr 3, uses 4 tons of fuel
J-5: 13.33Td, MCr 4.67, uses 6.67 tons of fuel
J-6: 20Td, MCr 8, uses 12Td of fuel.

Probably ought to round cost and size upward for convenience.

These are the basic J-Torps that might have been in A4: Leviathan. They don't do anything except Jump and then transmit a message upon Jumpspace exit. They have to be released by their parent vessel at the 100D limit, and that ship has to be able to back away out of its own 100D distance of the J-Torp for a successful launch. (Maybe it can use the exhaust from the jump fuel burn as a reaction motor instead?)

Given the LBB2 TL paradigm, they might all be TL-9, limited by the TL of the ship's computer needed to run Navigate, Generate and Jump-N to enable them to function.

Completely impossible in any rule set after '77. HG'79 mandates Pn=Jn, Mod/n=Jn, 1%*Pn fuel,1Td minimum tankage; LBB2'81 as well (plus 10Pn tons fuel that simply cannot fit). Can't be modified to incorporate drop tanks because that would require at at least HG'79, which obsoletes the rules from '77 that otherwise let it work. Oh, and the 100Td minimum hull to jump makes them explicitly illegal.

Pretty to think about, though.

Other Jump Torpedo and related posts and threads:
Me in Vote Your Canon #4 Jump Torpedos (post #146)
The Littlest Starship (derived from a house-ruled jump torpedo based in LBB5).

 

[Condottiere]

I don't know about Leviathan, but as I recall Alphabet drives, you always had that default five tonne overhead for Jump(s), which got canonized at least by Tee Five/Mongoose, and expressed by High Guard customization as one percent, minimum one tonne total.

As regards energy requirement, probably not thought through to it's logical conclusion.

At the moment, there's a discussion regarding missiles, point defence, and fixed mounts, whether laser accuracy counts, do missiles have direction in their lives, and virtual volume, so contradictory text seems the norm.

Contradictory to what?

Succeeding, preceding, and common sense.

 

[Grav_Moped]

As regards energy requirement, probably not thought through to it's logical conclusion.

MgT kept the idea from '77 that once you go down the rabbit hole, your subsequent week-long stay in Wonderland is free aside from needing to keep the lights on.

HG (both) and '81 have the powerplant running at Pn=Jn* through the week spent on the other side of the looking-glass, presumably to support the jump drive keeping the bubble intact.

----‐---‐--
*at least. By default it should be at nameplate Pn even if that's higher than the Jn....

 

[Condottiere]

Power source has also been diversified, when previously only fusion reactors and black globes worked, disregarding collectors.

In theory, you could have an external (power) source charge up the jump capacitors, possibly attached to the drop tanks, but something needs to keep powering the life support.

 

[AnotherDilbert]

MgT kept the idea from '77 that once you go down the rabbit hole, your subsequent week-long stay in Wonderland is free aside from needing to keep the lights on.

HG (both) and '81 have the powerplant running at Pn=Jn* through the week spent on the other side of the looking-glass, presumably to support the jump drive keeping the bubble intact.

CT has the PP running at all times, whether the power is needed or not. You fill the tanks, the fuel lasts one trip or four weeks, then you need more fuel, regardless of level of activity. Of course it's a vast simplification...

The jump drive only uses power when you initiate jump, not during jump. See JTAS#24.

T5 has this to say:

T5, B2, p120:
For example, the Jump Drive is destroyed by a luddite bomb after one day in Jump. The time roll is 7+ Flux = 5. The ship emerges into RealSpace after 5 total days in Jump.
Or, the Jump Drive fails 6 days into the jump. Time roll is 7 +Flux= 2 days. Although 6 days have passed aboard ship, it emerges into Real Space where only 2 days have elapsed.
The ship emerges from Jump Space at its otherwise planned location.

You will arrive at the destination unharmed, even if the jump drive (or presumably power plant) is destroyed.

 

[Spinward Flow]

Or, the Jump Drive fails 6 days into the jump. Time roll is 7 +Flux= 2 days. Although 6 days have passed aboard ship, it emerges into Real Space where only 2 days have elapsed.

If that were the case, I see no reasonable reason for crews to "waste the lifespans" of crews and passengers in jump space. Why spend a week per jump "being bored" and idling around when you can simply deliberately shut down the jump drive early and "skip" a week of subjective time?

From the perspective of occupants then, the Jump Flash acts like an edit cut in a film.

1. We see the stars in their constellations outside our windows at our jump point of origin.
2. FLASH!
3. We see the stars in new positions outside our windows after breakout at our destination.

The ship still takes "1 week" to arrive at its destination after departure from origin, but "while the ship is in jump, no subjective time passes" so there isn't even the opportunity to "look out the window into jump space" (because that takes time to do and to see) because you arrive "instantly" from a subjective point of view.

• In OUTSIDE OBSERVER terms, jump would continue to function the way it always has (as a 1 week duration "teleport" between points).
• In SUBJECTIVE OBSERVER terms, it means that crews and passengers DO NOT AGE during jumps, effectively extending their lifespans into the future (by "skipping over" the subjective time required when jumping).

For anyone who has read John Scalzi's book series Old Man's War, you might recognize the "Skip Drive" concept at play here ... except in those books jumps were instantaneous teleports both objectively AND subjectively (with some mind melting closely aligned parallel universes stuff going on for good measure that just makes your head hurt) ... so not EXACTLY the same, but close enough.



Of course, doing that (no subjective ship time passes during jump weeks for objective universal time) does all kinds of interesting things to life support requirements, which then has various knock on effects in starship economics,, not to mention mucking up the aging tables for character creation with respect to careers that involve a significant amount of jumping from place to place (such as Navy, Scout and Merchant character generation, among others).

Time "works" in normal space.
Time "doesn't apply" in jump space will make scientific researchers collective heads explode.

It also makes potentially "wild" results possible, such as meeting someone who is only 22 years old who was born 30 years ago if they have TRAVELLERed a lot during their lifetime. It would also bring a new meaning to the Travellers' Aid Society since their especially "well traveled" members would essentially be "relics" from an earlier time, because their lifespans "get longer" every time they jump (into the future) ... so to speak.

 

[AnotherDilbert]

If that were the case, I see no reasonable reason for crews to "waste the lifespans" of crews and passengers in jump space. Why spend a week per jump "being bored" and idling around when you can simply deliberately shut down the jump drive early and "skip" a week of subjective time?

You get an extra roll on jump duration by sabotaging the jump drive. A bit expensive to gain an average day or so?

 

[Condottiere]

The Imperial family, megacorporation chief operating officers, and some of the aristocracy, could afford it.

Also, one shot jump drives are about a quarter to the cost.

 

[Grav_Moped]

CT has the PP running at all times, whether the power is needed or not. You fill the tanks, the fuel lasts one trip

(1977 rules)

or four weeks,

(Everything after that)

then you need more fuel, regardless of level of activity. Of course it's a vast simplification...

Well, yes. This is where my distinction between an in-game universe that is rules-defined and one that is rules-described is relevant.

The jump drive only uses power when you initiate jump, not during jump. See JTAS#24.

T5 has this to say:

You will arrive at the destination unharmed, even if the jump drive (or presumably power plant) is destroyed.

And this, plus the TCS power-down rule (The Outer System, p.38), explains how the LBB2'81 XBoat works. It breaks everything else, but it does explain the XBoat.

How much fuel does the Size B, Pn-4 power plant in an XBoat use solely to initiate jump over and above the 10% per Jn Jump Fuel burn? (It's undefined in the rules, so we're house-ruling here by necessity.)

Quoting the rule:
"Fuel may be conserved while waiting by lack of maneuver; the ship's power plant will consume fuel as if it were a power plant-1, regardless of its true value. Every full load of fuel for a power plant-plant-1 [sic] will last 4 weeks. Once all fuel is exhausted, all ship's systems including life support will no longer work."

"Fuel may be conserved while waiting by lack of maneuver..." No maneuver drive means maneuver is absolutely lacking here. That's covered. While the statement may be a synecdoche representing powering down all ship systems since the context is one in which only maneuver is relevant, it's the rule as written.

On the other hand, HG states that fuel consumption due to maneuver is "...inconsequential, and assumed to be part of the power plant consumption, regardless of the degree of maneuver undertaken." (HG'81, p. 17) Looks kind of difficult to reconcile with the TCS rule, unless TCS supersedes HG'81 on this point (as it likely does because of publication dates, let alone that TCS is specifically intended to modify/clarify HG'81).*

So, since it doesn't and cannot maneuver, an XBoat gets to apply the power-down rule and use only Pn-1 fuel.

Except for when it fires off the Jump Drive. And this brings me back to my earlier question -- how much of the power plant fuel allocation does this take? The answer should be informed by how long it actually has to be running at Pn-4. HG says two turns, due to EP requirements under breaking off by jumping. Now, as to how long it takes to get up to Pn-4 from a Pn-1 idle, one needs to look to JTAS#14, p.25 "High Guard Optional Rules" (some of which were incorporated into TCS). "One turn [20 minutes -- Ed.] is required for each level of power plant to be restored." So, 3 turns to reach Pn-4 from Pn-1 (during which it's treated as a heavily-limited Pn-1), and two turns at Pn-4 to provide the necessary 2EP/Jn. Five turns, or 1 hour and 40 minutes.

Assume it uses fuel for this at the average 4-week rate over this 1 hour and 40 minutes, and it then needs an astonishing 0.16 tons of fuel to do this.

So.

10.16 tons of fuel are enough since it's always in powered down mode (Pn-1, so 10Pn tons for 4 weeks is 10 tons) except for less than two hours per Jump.

That, and the 40 tons of jump fuel, fit into a 100Td hull with Jump-B, Power-B, a Mod/4, and a half-stateroom with a little room to spare.

QED.
‐----------
* It really does make sense, and I'll explain later.

 

[Spinward Flow]

This is where my distinction between an in-game universe that is rules-defined and one that is rules-described is relevant.

Rules Defined = there is nothing beyond what the rules describe
Rules Described = the rules are only a PARTIAL description, rather than encompassing all possibilities (forever and ever)

Assume it uses fuel for this at the average 4-week rate over this 1 hour and 40 minutes, and it needs an astonishing 0.16 tons of fuel to do this.

Under that interpretation, all you need is a Power Plant-B and 10 tons of fuel to run for 28 days (4 weeks).
However, if you reduce the power plant endurance down to 10 days instead of 28, you only need 2.8 tons of power plant fuel. Add in the 0.16 tons consumed ramping up to code: 4 output levels in preparation for jump and you're at 2.96 tons of fuel ... so just round it up to 3 tons of power plant fuel and call it done.

Jump fuel = 40 tons
Power Plant fuel = 3 tons
Total fuel load = 43 tons needed during normal operations.



Of course, I'm a weirdo who would think that the even smarter play would be to have the XBoat remain connected by an umbilical quick disconnect docking arm to an Express Tender (with a Power Plant-H drive, more than capable of delivering the requisite EP to the jump capacitors of the XBoat in a single combat turn).

That way all the XBoat "needs" onboard is the jump drive and the jump fuel, because the power plant part of the equation is "outsourced" to the Express Tender and works on a quick "fuel, power and GO" launch routine. The Express Tender undocks, maneuvers 7-10km away from the XBoat (Tenders are 60m long, so 100 diameters from that is 6km) and the XBoat jumps away before the power charge in the jump capacitors decays.

The jump capacitors in a 100 ton XBoat require 8 EP to jump and have a 72 EP storage capacity.
Even if you assume that 1/2 of EP stored in jump capacitors is "lost" every single combat turn (because the capacitors can't hold the charge long term or whatever handwavium you prefer), pushing 16 EP (the output of a Power Plant-H drive) per combat turn into an XBoat for "about an hour" from a Tender will still leave PLENTY of time for the Tender to undock and maneuver away to 7-10km distance before the XBoat's jump capacitors decay below the 8EP threshold.

And in THAT circumstance, you don't NEED a power plant at all in a LBB2.77 XBoat ... because power plant services are rendered "as needed, on demand" by the Express Tenders that are always recovering, refreshing and relaunching the XBoats.

 

[AnotherDilbert]

And this, plus the TCS power-down rule (The Outer System, p.38), explains how the LBB2'81 XBoat works. It breaks everything else, but it does explain the XBoat.

You keep ignoring the requirement for consistent power levels:

CT Consolidated Errata 1.2, p16-7:
Ships in non-combat situations can be “powered down” to reduce the fuel consumption of the ship’s power plant. The minimum level of power plant is one, which is enough to power the life support systems and maintain maneuver drive-1, jump drive-1, etc. No energy-using weapons may be used in a powered down condition. Under normal circumstances, a ship’s power plant uses a week’s fuel while in jumpspace. However, the power plant could be powered down to a factor equal to the jump being performed during that week. Ships which spend an entire 4-week period in a powered down state reduce the fuel consumption of the power plant to the powered down level.

You need to keep the same power level for weeks. A power plant in an hypothetical XBoat could be powered down to PP-4, using 40 Dt (or 4 Dt if HG) in four weeks.

While powered down, you can use power for the drives as the power down level, you can manoeuvre and jump as desired.


No matter how much fuel is actually used, a full four weeks for the power plant must be built into the ship, e.g.:

TCS, p13:
FUEL TANKAGE
. . All craft must be fitted with fuel tanks during the design and construction process. The size of those tanks is determined by the fuel formulae for jump drives and power plants. For jump fuel, 10%of the total hull tonnage must be committed per jump number the drive is capable of. For power plant fuel, 1%of the total hull tonnage must be committed per power plant number (this is equal to one ton per energy point produced by the power plant). Enough fuel for the power plant must be carried in normal fuel tanks; jump fuel and additional fuel may be carried in one of the additional tankage types outlined below.

It may be silly, but it's a clear and consistent requirement from LBB2'77 forward.


The LBB2'77 XBoat has no power plant fuel because it has no power plant. If made under any other rules it needs a power plant and hence a full amount of power plant fuel, whether it uses it or not.

 

[Grav_Moped]

However, if you reduce the power plant endurance down to 10 days instead of 28, you only need 2.8 tons of power plant fuel

Yes, but RAW demands 4 weeks. I mean, I agree with you here, but it's not necessary to call on that to make the point. I did say it breaks everything else...

 

[Grav_Moped]

Should be a quote, but am on phone and editing is a chore:

However, the power plant could be powered down to a factor equal to the jump being performed during that week. Ships which spend an entire 4-week period in a powered down state reduce the fuel consumption of the power plant to the powered down level.

Hadn't seen that, but have always assumed it worked that way too. On the other hand, this is incompatible with the assertion above (from T5) that jump requires no additional power expenditure after initiation --because it doesn't even need a jump drive at that point!

 

[Grav_Moped]

I did say it breaks everything else...

And the errata point @AnotherDilbert broughr up, above, fixed it. Then T5 broke it again.