Book2 designed Xboats

[Foxroe]

Perhaps this was solved elsewhere...

If I understand this correctly, there is a discrepancy between the 1st edition Book2 design of the Xboat as it appears in Supplement7, and the design rules from later editions of Book2. The newer editions necessitated that starships include a jump drive AND a power plant; therefore, by Book2 fuel formulae, a 100-ton Xboat needed 80 tons of fuel. This left no room for the drives, bridge, Model/4, 2 staterooms, and 1 ton of cargo.

However, reading through the description of the Xboat in Supp7, it states that there is only enough power/life-support for 3 days after jump. I assume that this is the case because there is no dedicated power plant in the design (contrary to later editions of Book2), or the ship is reliant on battery power for life support and lighting (see TTB, pg. 51, under "Drive Failure"). I can't imagine that the Imperial communications infrastructure would rely on a ship which resorts to emergency battery power after every jump.

So given all of this, I did some thinking (always dangerous of course! )...

By Book2 design rules, if we include a type-B jump drive, a type-B power plant, 40 tons of jump fuel, a 20-ton bridge, a 4-ton Model/4, 2 staterooms, and 1 ton of cargo, this totals 95 tons. This leaves 5 tons for power plant fuel.

Now according to Book2, 10Pn (40 tons for the Xboat) supports 4 weeks of routine operations and maneuvering. So, if 40 tons is required for four weeks of operation, ignoring the fact that there is no maneuver drive, shouldn't 5 tons of fuel support 3.5 days of operation?

This would jive well with TGB's "3 days out of jump", but only if we can assume that the power plant doesn't consume an appreciable amount of fuel while in jump space.

Is there a rule that specifically states/implies that jump-fuel supports powering the ship while in jump-space? Does this design work, or is it back to the drawing boards? The only other alternative would be that the Xboat relies on battery power following jump... but this leaves extra tonnage, which doesn't fit nicely with the Supplement7 design.

-Fox

 

[far-trader]

Perhaps this was solved elsewhere...

Yep, at least once before on this board that I recall offhand

Well, perhaps not solved, but some extra reading if you're interested...

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=3490

 

[Foxroe]

Interesting read (I didn't even think to look in the "Fleet" section <smacks forehead>!). There is an attempt at a LBB2 design there, but the others appear to be HG/MT/Other systems. The link to "Rethinking the Xboat System" appears to be dead, which might help prove/disprove my design. Otherwise, the thread is mostly about the practicality of using Jump-4 routes, economics of comm traffic, TL issues, content of communications... A little too much for me at 10PM after a day of football festivities!

The LBB2 design posted there would work also (IMO), but it only has one stateroom to make room for more fuel. The proposal I made seems to be closer to "canon"... so long as it works.

So the question remains: Is the ship powered by the J-drive or the PP while in jump space? If it is not supported by the PP during jump, then my design works. Otherwise, the Xboat must rely on battery power... not a fun prospect for the pilot if the tender is not on the way, but then again, maybe this contributes to failed survival throws for Scouts during CharGen!

Any ideas?

-Fox

 

[Foxroe]

BTW, the only reason I question the use of the power plant (or its fuel usage) during jump transit is the reference to power plant fuel usage in TTB (pg. 60, under "Fuel"):

"Power plant fuel under the formula (10Pn) allows routine operations and maneuver for four weeks."

Is Jump considered "routine operations and maneuver"? Don't non-jump-capable ships also consume 10Pn tons in fuel?

-Fox

 

[boomslang]

The link to "Rethinking the Xboat System" appears to be dead, which might help prove/disprove my design.

I'm the author of that article; I'll have to ask robject where it went.

It prompted some discussion on CotI and also the ct-starships mailing list over the years.

Here's the upshot: the original Xboat ("X-Boat" or "Type X") was designed using the long-out-of-print 1st Edition of B2, wherein Jump rives did not require Powerplant input, and thereby it was possible to design a starship without a Powerplant if you omitted the Maneuver drive as well. (This is also why you'll have trouble accounting Supplement 7's Type A2: it has j-drive-B but m-drive-A and a p-plant-A to power the m-drive, which is why the design skimps by with only 50 dtons of fuel total.)

The current thinking is that you have a choice of perhaps three fixes to make the Xboat system "work":

1. Grandfather-in the special Xboat-custom, powerplant-less j-drive-B from the deprecated 1st Edition B2. Of course, some smart-aleck like Yours Truly will always find hotrod uses for salvaged ones... handwaving tends to beget more loopholes than it closes...

2. Go with traditional, later-edition B2 rules & design for the engineering (perhaps omitting the m-drive), but cut corners on fuel: there's enough room for j-drive-B and p-plant-B and 50 dtons of fuel (plus bridge, comp Model/4, and a stateroom) in a 100-dton hull, which buys you one Jump-4 and about a week of life support -- the week spent in Jumpspace, for example. Not for the faint-hearted, but doable with a little Fast Drug for emergencies. You also end up giving up the 17 dtons or so of "data banks", which there are no real rules for anyway.

3. Rebuilt the Xboat entirely, trying to stay within the rules, adding a few other options, and think outside the box. IMTU, I have a two-man, J-4, M-1, TL10 Mail Courier that's completely within the B2 rules and is cost-equivalent to a squadron of Type Xs and the Type XT that mothers them. The particulars of that design are left as an exercise for the reader...

:devil:

 

[far-trader]

I'm the author of that article; I'll have to ask robject where it went.

It's still here somewhere, it's just that links from before the server move are no longer valid. If you do a specific enough keyword search and use your username to narrow it you should be able to find it pretty easy.

 

[aramis]

Let's see
020td Bridge
010td PPFuel 1 week for Rating 4
007td PP B
015td JD B
004td Computer 4
040td J Fuel
004td 1xSR

This makes a workable XBoat under Bk2, and one that meets the requirements "Just barely" by declaring the fuel to be 1/4th the canonical month of fuel.

 

[Foxroe]

So then the official take on fuel usage is that the power plant continues to burn fuel to power the ship during jump transit, and not that either (A) it only uses a negligible fraction of the power plant fuel during jump transit, or (B) that the jump drive supports ship power with its own power/fuel while in jump space.

It’s because of the wording for power plant fuel usage (normal operation and maneuvering for four weeks) as it applies to the case of a non-maneuvering ship... If the ship has no maneuver drive, it seems to me that [10Pn] tons should be plenty of fuel for powering the ship for longer than four weeks. Or maybe another way to look at it is that the ship isn’t maneuvering in the traditional sense while it’s in jump space; therefore, the rate of fuel consumption by the power plant while in jump space is much smaller than when in-system. This would lead me to believe that the same fuel consumption rate (if not less since the jump drive is “off”) would apply to a maneuver-less ship in normal space; therefore, [10Pn] tons of fuel would power a ship without a maneuver drive for much longer than four weeks. So shouldn’t 5 tons of PP fuel be enough for an Xboat for ~10 days?

-Fox

 

[far-trader]

It's a hard question to answer Fox. The way I've always looked at CT powerplant fuel usage (both B2 and the much reduced B5) is that the powerplant is required to operate in one of two modes, full on or full off, with no fuel conservation modes between the two. It's an abstraction of course, put it down to some handwave or another, or houserule a solution that you like. That's the beauty of CT, changing what you want. Just be mindful of the consequences.

I think it was MegaTraveller that introduced powerplant fuel conservation by idling back the powerplant. But I think it may have also spelled out the need for the full powerplant rating (equal to the J rating at least) to operate through jump.

Personally I like the old 1st ed rule that the Jump drive doesn't need a powerplant (i.e. it is a powerplant). If makes more sense to me. But I just shrug and accept the 2nd ed rule. And I actually prefer the fuel hog rules for B2 powerplants. They make more sense to me as I attribute the high fuel requirements to a combination of reaction mass for the maneuver drive and cooling ejecta to keep the ship from melting. So if you're not maneuvering the fuel is spilled out the thruster cones at low velocity and deflected to produce no thrust and just dumps the powerplant heat, when you're maneuvering the fuel is still spilled for cooling but now the deflectors are lined up and the thrusters accelerate it to produce useful thrust. I'm actually not a fan of anything about B5 ship design aside from the extra weapon choices (except for "meson" tech) and drop tanks.

 

[Foxroe]

Thanks FT!

I guess I was kind of fishing for some CT reference that talks about varying power plant fuel consumption (I don’t have the CT CD from FFE yet).

I like your hand-waving by way of cooling the fusion plant, even if it doesn’t support my idea of lower fuel consumption for the Xboat.

I guess the only way to treat it by the book is by reducing the endurance (consumption time) of the plant/fuel, but not the consumption rate… unless I house-rule it of course. Although I must admit I’m not much of a house rule guy. I’m never satisfied with any “fixes” I come up with, so I always end up playing BTB.

-Fox

 

[boomslang]

It's a hard question to answer Fox. The way I've always looked at CT powerplant fuel usage (both B2 and the much reduced B5) is that the powerplant is required to operate in one of two modes, full on or full off, with no fuel conservation modes between the two. It's an abstraction of course, put it down to some handwave or another, or houserule a solution that you like. That's the beauty of CT, changing what you want. Just be mindful of the consequences.

I favor the interpretation that the powerplant must run at a minimum level equal to the operating level of the drives attached to it -- so, although I would allow it to be throttled back to powerplant-3 during a Jump-3, it would need to run full blast during a Jump-4.

The one week of powerplant fuel at powerplant-4 is only a real problem if you go with the popular-but-not-strictly-CT-canon formula of '168 hours plus-or-minus 10 percent' for Jump duration. Your Scout Pilot will need a vacc suit and/or some Slow Drug about half the time he undertakes a Jump-4 under that formula.

IMTU, we use a fixed 150 hours/Jump, which leaves a tight, but manageable, 18-hour margin either side of the Jump, and allows the Xboat and/or Mail systems to move packets in calendar-friendly steady one-week increments. (It guarantees a Free Trader a full week in port to scrounge cargo and passengers too, but I digress.)

A fourth possible fix is to allow alternate powerplant fuel consumption (I'm partial to Thomas House's HG2-inspired EP-based system, which Google should be able to find if one hasn't seen it); an Xboat with a p-plant-B would only need, say, 4 dtons of fuel per month -- and that actually buys one room for a second stateroom and even an m-drive-A (omitting much of the need for Xboat Tenders), as well as perhaps a hardpoint and some fire control (I'm just sayin')....

But that is another one of those handwaving strategies that can have huge unintended consequences if you don't think it all the way through... so caveat emptor.

 

[boomslang]

Thanks FT!

I guess I was kind of fishing for some CT reference that talks about varying power plant fuel consumption (I don’t have the CT CD from FFE yet).

It's inferred from a dead-tree JTAS article or two, as well as perhaps the Beltstrike module, IIRC.

I guess the only way to treat it by the book is by reducing the endurance (consumption time) of the plant/fuel, but not the consumption rate… unless I house-rule it of course. Although I must admit I’m not much of a house rule guy. I’m never satisfied with any “fixes” I come up with, so I always end up playing BTB.

IMTU, I rationalize the as-written powerplant fuel requirements the same way I rationalize the impossibly-low long-haul cargo/passenger rates: it's a regulatory thing. In the required-fuel matter, a starship won't be granted an SPA/IN/whomever spaceworthiness certificate and allowed to practice commerce (or even operate in civilized space) unless it meets minimum safety requirements as regards available powerplant fuel. This then, I figure, is where the ridiculous 10Pn powerplant fuel number comes from. Regardless of whether fuel is consumed at that rate, or at the lower rate I mentioned in my previous post, non-Imperial-government starships must allocate that much tankage or it's fines -- and even impoundment -- to avoid creating a hazard to navigation.

The IISS, being a 3I government agency, is exempt from this minimum fuel requirement due to the "essential nature" of the communication services provided by the Xboat system, and the extensive operational support in place (in the form of Xboat Stations and Xboat Tenders) to insure the safety of both the (non-maneuverable anyway) Xboats and all other traffic nearby.

And thus is canon preserved and a dread House Rule avoided...

 

[far-trader]

Yeah, X-Boats routinely come out of jump with very little fuel left imtu.

Sidenote: I don't usually bother with the hours calculation and imtu interpret the random hours as a metagame calculation of the exact and known in advance time for a jump between any two places. For example, a roll of 150 hours to jump from A to B would mean at that particular time and place for that particular ship in system A will require 150 hours in jump space to emerge at the desired time and place in system B. And it will be a known time and place before the jump is initiated. That's what the Navigator does with the computer and programs (or has done by the local SPA in the form of a NavCar (short for Navigational Cartridge, aka jump tape).

Don't forget though, that even if the jump takes longer than the week (presuming you're kind enough to allow that the ship doesn't simply vanish when the power runs out if it's still in jump space*) you still have emergency batter power for life support and basic lighting for 1D days (per drive failure rules B2 p6). Lots of time for the Tender to get there, most of the time.

* Note the misjump rules say that you roll 1D for the number of weeks the ship spends in jumpspace anytime it misjumps. Now what does that mean for a ship that has just 4 weeks of fuel and is going to spend 5 weeks in jumpspace? If the powerplant is what is keeping jumpspace from eating the ship, they're doomed. If the powerplant is not needed to keep jumpspace at bay then they ride it out and will need to be lucky with the battery power to survive on minimal life support the final week without power. It's one of the consequences affected by the choice of how powerplants work with jumpdrives, or don't. It could be one of the forgotten rules when the jumpdrive rule was changed from 1st ed to 2nd ed, with the unintended consequences overlooked. Errata or opportunity?

 

[Foxroe]

IMTU, I rationalize the as-written powerplant fuel requirements the same way I rationalize the impossibly-low long-haul cargo/passenger rates: it's a regulatory thing. In the required-fuel matter, a starship won't be granted an SPA/IN/whomever spaceworthiness certificate and allowed to practice commerce (or even operate in civilized space) unless it meets minimum safety requirements as regards available powerplant fuel. This then, I figure, is where the ridiculous 10Pn powerplant fuel number comes from. Regardless of whether fuel is consumed at that rate, or at the lower rate I mentioned in my previous post, non-Imperial-government starships must allocate that much tankage or it's fines -- and even impoundment -- to avoid creating a hazard to navigation.

The IISS, being a 3I government agency, is exempt from this minimum fuel requirement due to the "essential nature" of the communication services provided by the Xboat system, and the extensive operational support in place (in the form of Xboat Stations and Xboat Tenders) to insure the safety of both the (non-maneuverable anyway) Xboats and all other traffic nearby.

And thus is canon preserved and a dread House Rule avoided...

Good stuff, boomslang!

I would then speculate that there really isn’t a need to redesign the Xboat if your willing to explain away its differences as a special case (for whatever reason), or trim the design to 1 stateroom and no cargo, which would provide for 10 tons of PP fuel (is my math right?) – perhaps enough to support the one week in jump, then the pilot relies on battery power until the tender arrives. I would certainly assume, as you say, that the tenders are on station near the established jump point, or some young Scout will be making a survival throw!

-Fox

 

[Foxroe]

FT: “Note the misjump rules say that you roll 1D for the number of weeks the ship spends in jumpspace anytime it misjumps”

Now is that 1D weeks for the crew in jump space, or 1D weeks passes in the REAL universe while only 1 week passes for the crew…

FT: “It could be one of the forgotten rules when the jumpdrive rule was changed from 1st ed to 2nd ed, with the unintended consequences overlooked. Errata or opportunity?”

Opportunity!

-Fox

 

[Foxroe]

So by Aramis' design posted earlier, going by LBB2:

100dt non-standard hull, not streamlined, a 20dt bridge (including communications banks), a Model/4, Jump-4(B) drive, PP-4(B), 40dt jump fuel, 10dt PP fuel (for 1 week of operation), 1 stateroom (could be double occupancy in a pinch), and no cargo, that's MCr69.3 assuming no architect fees and 10% volume production discount, and it would take 10 months to build.

I would rationalize that as part of the "bridge" tonnage there is a small bank of rechargeable batteries (or some such similar future technology) to provide power for transmissions, life support, and lighting, for about 3 days, which should be enough time for the tender to recover the Xboat. Cargo isn't really necessary since most comm traffic is likely electronic (if not totally electronic), and mail can be handled by Scout/Couriers and contracts with traders.

I would also theorize that since Xboat routes are well established, astrographical calculations have determined the ideal jump in/out points. This way the tenders would always be nearby these points.

-Fox

 

[far-trader]

Yep, same way I worked it out too. It maintains much of the spirit of the original and stays away from any wide changes in rules.

Rather than the batteries being part of the bridge tonnage I always figured it was part of the powerplant tonnage (and house ruled it as variable to the factor), but I think I like your idea of putting it in the bridge tonnage. Jives nicely with the single D6 of days of power regardless of powerplant and helps explain the standard minimum bridge tonnage being so large. Consider that adopted for mtu henceforth

About the only difference my design made iirc was to make the hull a standard (MCr2 and 9 months to build), the Imperium has had these around for ages and there's probably been more of them built than the Type S.

Yep, the IISS has been doing this long enough that it's extremely rare for one to go missing enroute and the Tenders usually don't have to go far to make the pickups the rest of the time, very often they are within kilometers of the precipitation point at the scheduled time, and that only to allow a little room for error. It's very routine and boringly dull, 99.999% of the time.

 

[boomslang]

3. Rebuild the Xboat entirely, trying to stay within the rules, adding a few other options, and think outside the box. IMTU, I have a two-man, J-4, M-1, TL10 Mail Courier that's completely within the B2 rules and is cost-equivalent to a squadron of Type Xs and the Type XT that mothers them. The particulars of that design are left as an exercise for the reader...

Ah, here we go; I knew I'd posted it to CotI at some point in the past...

 

[rancke]

I actually prefer the fuel hog rules for B2 powerplants. They make more sense to me as I attribute the high fuel requirements to a combination of reaction mass for the maneuver drive and cooling ejecta to keep the ship from melting. So if you're not maneuvering the fuel is spilled out the thruster cones at low velocity and deflected to produce no thrust and just dumps the powerplant heat, when you're maneuvering the fuel is still spilled for cooling but now the deflectors are lined up and the thrusters accelerate it to produce useful thrust. I'm actually not a fan of anything about B5 ship design aside from the extra weapon choices (except for "meson" tech) and drop tanks.

The trouble with all those handwaves is that none of them actually bear examination. For instance, hydrogen is not very efficient as cooling ejecta (nice term). If some of the hydrogen is used for that purpose, it would be more efficient to use part of the fuel tank to carry something else, like water (Note, I'm paraphrasing what someone with more knowledge of physics once told me).


Hans

 

[rancke]

IMTU, I rationalize the as-written powerplant fuel requirements the same way I rationalize the impossibly-low long-haul cargo/passenger rates: it's a regulatory thing. In the required-fuel matter, a starship won't be granted an SPA/IN/whomever spaceworthiness certificate and allowed to practice commerce (or even operate in civilized space) unless it meets minimum safety requirements as regards available powerplant fuel. This then, I figure, is where the ridiculous 10Pn powerplant fuel number comes from. Regardless of whether fuel is consumed at that rate, or at the lower rate I mentioned in my previous post, non-Imperial-government starships must allocate that much tankage or it's fines -- and even impoundment -- to avoid creating a hazard to navigation.

That works to explain why a ship has such a huge power plant fuel tank. IMTU I rationalize it as a safety requirement aimed at misjumps. If you misjump into empty space, you have enough fuel with you to run your maneuver drive long enough to get back to civilization a parsec away. (Though why a jump-6 ship is required to spend 6% of its meager payload on reserve fuel when its jump-1 sister ship can get along with only 1% of its far bigger payload is a puzzle).

But it doesn't explain why you have to buy new power plant fuel every four weeks. With several percents of your ship dedicated to power plant fuel, you have enough fuel to run the ship for its expected lifetime. You fill her up when she leaves the yard and don't bother about it henceforth! (OK, that may be an exaggeration, but not much of one).

The ramifications are interesting, though. You could decide to break the regulations (like turning the fuel tanks into hidden smuggling compartments and rig the gauges to show full tanks anyway ). Or you could have ships built in other jurisdictions where they don't have that regulation that don't have the tankage and has to install demountable fuel tanks before entering Imperial space.


Hans