Pondering starship evolution

[atpollard]

Clearly the hole in the center of a Lab Ship is "External" to the volume of the ship.
Clearly the hold of an X-Boat Tender is internal.

RAW ... If I open the doors to the empty hold of an X-Boat Tender, is it now "exterior"? Is the Tender now 400 dTons instead of 1000 dTons? Is the H Drive now J4 instead of J1?

These are the things I ponder when I "Rules Lawyer" the CT Starships.

 

[Badenov]

Clearly the hole in the center of a Lab Ship is "External" to the volume of the ship.
Clearly the hold of an X-Boat Tender is internal.

RAW ... If I open the doors to the empty hold of an X-Boat Tender, is it now "exterior"? Is the Tender now 400 dTons instead of 1000 dTons? Is the H Drive now J4 instead of J1?

This has been an issue with cargo and fuel forever. If you consume 400T of fuel before you jump, are you not 400T lighter? The answers lie somewhere between a heavy sigh, a GM's wince, and a paragraph of technobabble. If I were DM, I would rule that a space mostly enclosed by the ship's hull counts as interior space, whether full or empty.


This raises the question of the clamshell cargo bay, which is a flat surfcace on the ship's exterior upper deck. You stack cargo on top there, close the clamshell, and boom, it becomes an inside space. Now you have to recalculate your Jump, Thrust, Agility, and Power Plant numbers. Designs like this should automatically allow things to be thrown at the player that tries this garbage. Although it seems like it ought to be doable, it also seems like it just exists to be a problem,

These are the things I ponder when I "Rules Lawyer" the CT Starships.

Sadly, CT is guilty of being a game, and so not up to all the questions RL might need answers to.

 

[casquilho]

Sadly, CT is guilty of being a game, and so not up to all the questions RL might need answers to.

It took me a while, but I did learn to accept this. Sometimes a rule is for game balance and has nothing to do with real life or real science.

 

[Badenov]

It took me a while, but I did learn to accept this. Sometimes a rule is for game balance and has nothing to do with real life or real science.

This raises the question of the clamshell cargo bay, which is a flat surfcace on the ship's exterior upper deck. You stack cargo on top there, close the clamshell, and boom, it becomes an inside space. Now you have to recalculate your Jump, Thrust, Agility, and Power Plant numbers. Designs like this should automatically allow things to be thrown at the player that tries this garbage. Although it seems like it ought to be doable, it also seems like it just exists to be a problem,

This all said, I just took a 500T combat cargo auxiliary (basically a military cargo ship with Jump 2 Thrust 6 and Armor 15) and expanded it to 1000T while keeping the components the same size (or no smaller). Cargo went from 77T to 577T. Went from Jump2/Thrust6G/6Agil. to Jump1/Thrust3G/Agil 3.

What I noticed:
1. M Drive Rating 3 in the 1000T hull had to be slightly beefed up to match the 500T Thr 6 numbers. Not enough to raise it to Thr 4, but raised to match the larger numbers.
2. J2 in the 500T was too small to convert to J1 in 1000T. The 1000T J1 is the size of a J3 drive in 500T. Solution, 500T drive bumped to J3. Still only has J2 fuel and but both ships now have the same J-3 Computer. Wasted in the J1 1000T ship. Slightly in ecxzess of needs in the 500T unless you can convert 50T of cargo to fuel storage.
2. The cockpit was the same size in both ships (Both at 20T min), but the 1000T cockpit cost more. The 500T cockpit cost was bumped up to match.
3. Hull and configuration were half the cost at 500T. Added a bump up to that sheet.
4. For 1000T, Hull Armor 7 had the same mass as Armor 15 on 500T. Had to Add the cost difference to the 1000T sheet. Apparently the armored clamshell doors that enclose the cargo provided protection for another part of the ship when they were retracted, which is now not protected when the clamshell is enclosing the cargo.
5. Power Plant is 93MCr and 31T in either configuration. The 31EP produced on either ship result in Agility 6 in the 500T hull and Agility 3 in the 1000T hull, but is a '6.2' PP in the 500T hull vs a '3.1' PP in the 1000T hull, hence that difference in the USPs.
6. Changed the Type from Combat Cargo Carrier, IC, to Military Cargo Carrier, QC. (Late edit)

Final cost: 511.5MCr. Crew (either config): 21.
500T USP: IC-52267C2-F00000-00004-0
1000T USP: QC-A2134C2-700000-00004-0

 

[Grav_Moped]

As soon as you stop thinking of the 10Pn tons of power plant fuel as being a "this amount consumed in 4 weeks" fuel consumption rate ... and instead start thinking of the requirement as being more of a regulatory "safety" requirement that exceeds the amount of fuel consumed within 4 weeks, but which yields "about 4+ weeks of endurance" regardless of circumstances, it starts making a lot more sense. The 10Pn computation should wind up yielding 4 weeks MINIMUM power plant endurance, rather than yielding a 4 weeks EXACTLY result (every time).

Yes, and....

This then should allow dispensing with some of the "safety margin" requirement when it won't be needed and/or can't be used, as in a LBB2'81 XBoat with 51Td fuel. If 40Td of power plant fuel will last more than 4 weeks (by some unknown amount) during a 4 week period that includes a Jump-4, then 10Td will last more than the 1 week that the Jump-4 requires (by an unknown, but proportionate amount). Add 10% (1Td) for the maximum possible Jump duration variation (variation is 10% with respect to an exact 1-week duration) and that 11Td will cover all possible power plant fuel consumption. There is no fuel consumption before the Jump because it's fed by a tender before departure, and none afterwards because it will be refueled by a tender upon arrival. Used as designed (outside 100D limit, only refined fuel, no engineer required due to ship size), misjump is not possible under LBB2 so the jump will always be 168 hours +/- 16.8 hours. Rules nonetheless say it needs an extra 29Td of fuel that it will never use (and, operated as designed, cannot use), and which of course do not fit into the hull anyhow.

Rules can get bent.

That's because LBB2.81 (and LBB2.77 before it) didn't use formulas to calculate fuel consumption proportional to the hull size, so things "get wacky" below 1000 tons (and let's be honest, above 1000 tons as well!) using standard drives.

The thing is, even if the Pn changes because of a modification in (combined) displacement, the drives themselves ARE NOT CHANGING. The Pn code value is a convenience for combat resolution purposes rather than something that modifies fuel consumption rates. You don't have a "double the hull, halve the fuel consumption" phenomenon going on, just because you added external fuel tanks ... because that would be SILLY.

Yes, I know that the "structure" of the LBB2.81 lookup tables and fuel allocation formula suggests that the same drive letters in bigger hulls consume less fuel, because the Pn "yield" of those drives goes down as the hull size goes up, but that's essentially a function of the excessive oversimplification used in the presentation of details and information in the design sequence used in LBB2 (77 and 81).

The power plant fuel consumption formula for LBB2 (77 and 81) is basically "padded" in such a way as to force "extra endurance" onto ACS starship designs.

This is the big problem with LBB2 fuel requirements -- in '77, the rule was based on actual fuel consumption (in small craft, and established as a the amount supporting 1-week-full-acceleration in starships at the small craft rate, then handwaved away as "one trip"). In '81, it was changed to the LBB5 "4 weeks" amount, without changing the deranged fuel formula that ignored tonnage. In retrospect, this was for backward compatibility with 4 years of LBB2 designs built with that formula.

You note that with variable tonnage (such as with drop tanks) the drives do not change. Of course, this is only true for drives that stay in the same ship. If one disassembed a Type S and extracted its Size A power plant (which required 20Td fuel in that hull for a month's operation, being Pn-2), and transplanted that exact Size A power plant into a Free Trader (where it would be Pn-1) it would only need 10Td fuel for a month. That's the rules. I think I said something about that in the previous section.

Sadly, CT is guilty of being a game, and so not up to all the questions RL might need answers to.

Fair point. Still, it has to make sense in order to foster suspension of disbelief.

 

[Spinward Flow]

If 40Td of power plant fuel will last more than 4 weeks (by some unknown amount) during a 4 week period that includes a Jump-4, then 10Td will last more than the 1 week that the Jump-4 requires (by an unknown, but proportionate amount).

Not to put too fine a point on things, but starships don't need maneuver agility (or weapons or screens) during jump.
In fact, the only onboard system that ought to be consuming EPs during jump ought to be the computer (if model/3+).

Point being that a starship with a model/1-2 computer spends EP: 0 on computer ... so during jump would only need to consume enough fuel for housekeeping/basic power (a mere 0.05 tons of fuel consumption per 7 days for a 100 ton hull).

The LBB2.77 design of the XBoat used a model/1bis computer (invalidated later by LBB5.80 and LBB2.81) since a CPU/Storage of 4/0 was all that was needed to run the required computer programs to achieve J4 out of the XBoat.

Consequently, the CT Beltstrike fuel consumption formula would mean that 40.1 tons of fuel (40 for the J4 @ 100 tons, 0.1 tons for the power plant) would be sufficient for 2 weeks of power plant endurance (with no capability to maneuver).

According to LBB5.80, the power plant would need to generate 8 EP within 2 combat turns in order to initiate jump, so a Power Plant-4 in a 100 ton form factor would need to have a max power output of 4 EP. However, LBB2.77 does not require a power plant for jump drives ... so ... handwavium.

So what you wind up with to construct an XBoat is:

• 100 ton standard hull (15 tons engineering/85 tons main)
  • 15 tons for LBB2.77 Jump-B drive
  • 0 tons for LBB2.77 Maneuver-none drive
  • 0 tons for LBB2.77 Power Plant-none drive
  • 40 tons for jump fuel
  • 20 tons for bridge
  • 1 ton for model/1bis computer

15+40+20+1 = 76 tons

That leaves 24 tons remaining for staterooms, cargo bay and the all important "Extensive Data Banks" for data recording and storage during jumps (whatever tonnage THAT was supposed to consume).

Adding a Maneuver-A and Power Plant-A drive (which would yield a 2G performance in a 100 ton form factor under LBB2.77) would cost 15 tons for drives and fuel, in addition to requiring a custom 100 ton hull, rather than a standard 100 ton hull. The remaining 9 tons could be 2 staterooms (1 for the pilot and 1 for a "no frills" passenger transport) and a 1 ton cargo hold (for high priority specialty cargoes).

You note that with variable tonnage (such as with drop tanks) the drives do not change. Of course, this is only true for drives that stay in the same ship. If one disassembed a Type S and extracted its Size A power plant (which required 20Td fuel in that hull for a month's operation, being Pn-2), and transplanted that exact Size A power plant into a Free Trader (where it would be Pn-1) it would only need 10Td fuel for a month. That's the rules. I think I said something about that in the previous section.

Correct.
But a Power Plant-A installed into a 100 ton hull with a 100 ton external load docked to it would not "automagically and retroactively" stop needing its 20 tons of power plant fuel requirement, transforming to only need 10 tons of power plant fuel as would be the case in a 200 ton Free Trader using the same drive.

The 200 ton Free Trader is a different design and class of starship, even if the drives used are exactly the same kind as the 100 ton Type-S Scout/Courier.

Yes, the drives are A/A/A in both classes of starship, but the fuel design requirements are different between them.

 

[atpollard]

This has been an issue with cargo and fuel forever. If you consume 400T of fuel before you jump, are you not 400T lighter? The answers lie somewhere between a heavy sigh, a GM's wince, and a paragraph of technobabble. If I were DM, I would rule that a space mostly enclosed by the ship's hull counts as interior space, whether full or empty.

Respectfully, I was not talking about WEIGHT, but the TRAVELLER defined INTERIOR and EXTERIOR volume.

Let me illustrate with a REAL WORLD example: The Space Shuttle.

• When the Payload Bay Doors are closed and an Astronaut is walking around the Cargo Bay, he is clearly INSIDE the Shuttle.
• When the Payload Bay Doors are closed and an Astronaut is walking on the outside of the Bay Doors (EVA), he is clearly OUTSIDE the Shuttle.
• When the Payload Bay Doors are open and an Astronaut is walking [EVA] around the Cargo Bay, is he INSIDE the Shuttle or OUTSIDE the Shuttle?

For TRAVELLER, the MD and JD want to know the area (VOLUME not MASS) closed from space and subtract the area open to space (like the hole in a Lab ship or the empty truss volume in a Dispersed Structure). Opening a cargo bay door CHANGES the volume (like removing the CUTTER MODULE from a Modular Cutter changes the Volume) converting the internal cargo bay to an empty hole in space (like the center of a Lab Ship).

 

[Badenov]

Respectfully, I was not talking about WEIGHT, but the TRAVELLER defined INTERIOR and EXTERIOR volume.

I was talking about volume also.

Let me illustrate with a REAL WORLD example: The Space Shuttle.

• When the Payload Bay Doors are closed and an Astronaut is walking around the Cargo Bay, he is clearly INSIDE the Shuttle.
• When the Payload Bay Doors are closed and an Astronaut is walking on the outside of the Bay Doors (EVA), he is clearly OUTSIDE the Shuttle.
• When the Payload Bay Doors are open and an Astronaut is walking [EVA] around the Cargo Bay, is he INSIDE the Shuttle or OUTSIDE the Shuttle?

In the example above, I would consider the astronaut inside if he is in the cargo bay whether the doors are open or closed. I understand the astronaut is in the vacuum of space when the doors are open. Inside has different meanings in different contexts, but for purposes of load on the M-drive, I would consider him inside.

For TRAVELLER, the MD and JD want to know the area (VOLUME not MASS) closed from space and subtract the area open to space (like the hole in a Lab ship or the empty truss volume in a Dispersed Structure). Opening a cargo bay door CHANGES the volume (like removing the CUTTER MODULE from a Modular Cutter changes the Volume) converting the internal cargo bay to an empty hole in space (like the center of a Lab Ship).

Opening a cargo door changes volume? That one makes no sense to me.

 

[Badenov]

So inside and outside have different contexts, and it seems like we're getting crossed up because different things and different cases intersect strangely sometimes. 'Inside volume' can mean 'volume interior to the hull', and that's the normal definition, but it can also mean 'volume that is not subject to the vacuum of space' in the case of open/closed bay doors or 'volume that is under the influence of my drive', which is a corner case because distributed hulls are allowed to carry riders externally (by the first definition) and have it still subject to the ships' drives.

In that last case, 'volume under the influence of my drive' a distributed hull carrier like a Lurenti can carry 7 Battle riders that are not inside in either of the first two ways, but because it's inside under the third definition, the Lurenti doesn't leave its riders behind when it jumps.

 

[atpollard]

I was talking about volume also.

I apologize. Your opening with a point about Empty vs. Full Fuel/Cargo changing performance made it appear otherwise:

This has been an issue with cargo and fuel forever. If you consume 400T of fuel before you jump, are you not 400T lighter? The answers lie somewhere between a heavy sigh, a GM's wince, and a paragraph of technobabble.

 

[Badenov]

I apologize. Your opening with a point about Empty vs. Full Fuel/Cargo changing performance made it appear otherwise:

Well, there was another thread where I finally came to accept 'tons', for Traveller, as a measure of volume, even without noting it dT. But I was lazy and just wrote 'tons', so that part of any misunderstanding is on me.

 

[Spinward Flow]

Well, there was another thread where I finally came to accept 'tons', for Traveller, as a measure of volume, even without noting it dT. But I was lazy and just wrote 'tons', so that part of any misunderstanding is on me.

To be fair, in CT displacement is the understood primary meaning of "tons" in the starship design context, with a secondary (and prone to confusion) meaning of 1000kg increments as "tons" as well ... so you can see how confusion can arise.

The important thing for CT naval architects is that "weight/mass" really was something of a handwave, since everything "worked" on volumetric displacement and the "mass" of a starship was more or less a matter of Fluff Text™.

MegaTraveller went the route of trying to incorporate mass into the starship design sequence, by scaling up Striker to encompass starship designs as well ... but that only made things more confusing, rather than less. Hence why the notation of dTons has cropped up on forums like CotI so as to help specify "what kind of tons" are being discussed ... displacement tons (14m³) or mass tons (1000kg).

For CT starship design purposes, the ONLY kind of "tons" that matter are displacement tons.




The sole exception to that is when dealing with "dense cargoes" (of the speculative variety) that may have high specific gravity (such as iron, silver, lead, gold, iridium, etc.) and therefore high density. So high density cargoes hit the 1000kg mass limit faster than they hit the 14m³ volume limit, which in Simulation versions of Traveller means that "weighty" cargoes will require a lot of "wasted volume" in order to transport them, simply due to their high density.

Kind of like how a 1 lb of mercury is a lot smaller in volume than 1 lb of water, because mercury is a high density material.

So from a Practical Simulationist standpoint, a starship isn't always going to be filling the complete volume of its cargo hold every single time until there is no volume left to put anything into. Instead, there is going to be "wasted volume" in the cargo hold that isn't always occupied, but the "mass limit" of the cargo hold will almost always be reached, given sufficient cargo to "fill" the cargo hold's carrying capacity.



Note that one of the few ways to actually maximize the volume AND mass loading of a cargo hold (or hangar bay) at the same time is to fill it with liquid hydrogen fuel ... either in the form of demountable or collapsible fuel tanks ... because liquid hydrogen occupies 14m³ per 1000kg of L-H₂.

 

[Spinward Flow]

Let me illustrate with a REAL WORLD example: The Space Shuttle.

1. When the Payload Bay Doors are closed and an Astronaut is walking around the Cargo Bay, he is clearly INSIDE the Shuttle.
2. When the Payload Bay Doors are closed and an Astronaut is walking on the outside of the Bay Doors (EVA), he is clearly OUTSIDE the Shuttle.
3. When the Payload Bay Doors are open and an Astronaut is walking [EVA] around the Cargo Bay, is he INSIDE the Shuttle or OUTSIDE the Shuttle?

My answers:

1. Inside
2. Outside
3. So long as the Astronaut is within the volume boundary defined when the doors are closed, the Astronaut remains "inside" the Shuttle ... even if the location they are in is currently open to space (as it would be with the doors open). However, when the Astronaut moves beyond the boundary of where the doors would be when closed, then the Astronaut can (in Traveller terms) be defined as being "outside" the Shuttle.

A different way of looking at this particular question would be simple airlock.

1. With the outer door "closed" anyone who is "inside" the outer door is also "inside" the outer boundary layer of the outer hull bulkheads, so they are "interior" to the hull.
2. Anyone who has moved "outside" of the airlock outer door to the outer hull is therefore considered to be "outside" the hull.
3. The transition case then becomes when the inner door of the airlock is closed but the outer door is open (to the vacuum of space) and there is someone "inside" the airlock volume but they haven't moved "out" of the airlock volume yet beyond the outer door. Under such circumstances, I would argue that even though the outer door is open and the airlock volume is still in vacuum and exposed to space, the volume of the airlock is still "within" the bulkhead of the outer hull line and is therefore "inside" the hull.

Point being that there are going to be cross-over transition conditions where the boundaries of inside vs outside can get a little bit fuzzy, since the very notions of inside vs outside are a bit subjective/relative as concepts, rather than being absolutes in and of themselves.

Compare and contrast with the notion of a pressurized habitat versus an unpressurized one.

A pressurized habitat can include not only the interiors of spacecraft and starships, but also planetary world surfaces ... despite the fact that (most) Garden Worlds have no containment boundary structure for their atmospheres (because gravity does most of the work), while spacecraft and starships require containment boundaries to retain habitable life support conditions.

Conversely, an unpressurized location can be bounded (such as an airlock or a hull breach) or it can be unbounded (open, empty space). Walls are not "needed" for an unpressurized location to exist, although (sealed) boundary walls make it easier to change that condition of being unpressurized if desirable.



So to bring this back around to the point that @atpollard was trying to make, when it comes to the spreadsheet accounting of starship design in the naval architect's office, the definitions of "inside" vs "outside" the hull are largely conveniences to help orient assumptions.

For example, you wouldn't say that the volume of an airlock space was "outside the hull" when the outer door was open, but "inside the hull" when the outer door was closed. Under both conditions, the volume of the airlock space is kept (firmly) inside the hull.

However, what you CAN say is that when the outer door of the airlock is open, the interior of the airlock is "exposed to external environment" conditions ... while when the outer door of the airlock is closed and the interior door is open, the interior of the airlock should be "consistent with internal environment" conditions. You then use the cycling of the two doors of the airlock to moderate the transition from interior to exterior in a controlled and purposeful way.

Same notion applies (broadly speaking) to the docking of 2+ craft together for (unified) transportation of both.

A "hangar bay" is effectively a Giant Airlock™ (in a lot of respects) that is sized for an engineered craft (of some particular size), rather than just for vacc suits worn by sophonts. A "cargo bay" is also a sort of "poor man's airlock" (after a fashion) that is made on the cheap (to cut down on construction costs and maintenance needs). So in both cases the concepts of inside vs outside the hull remain relatively consistent.



There are, of course, some "weird edge cases" that challenge that very basic and simplistic first principles notion ... but it gives the starting point for thinking about the question (or at least, it does for me).

 

[Badenov]

So, I think the thread of the discussion has gotten away from the latest point, which was that things needed to be accounted for in the hull volume of the ship, whether physically inside, like normal, or physically outside, like the battle riders on a distributed carrier, and the ship needs to have sufficient drives, a bridge suitable to the volume, etc, or it's not a legal design.

This actually brings up the point of towing a ship, and I see in that light now that towing simply isn't a matter of beefing up the engines. If you don't have sufficient bridge volume, your control of the linked craft, tower and towed, will be imperfect. How exactly that would play out, I can't speculate, but I can absolutely see towing ships with outsized, bulbous bridges because they need to monitor things on the towed ship as well as on their own ship. OTOH, towing with an undersized bridge could be as innocuous as jumping with unprocessed fuel when your system's not set up for it. A small risk, and one you take if an emergency demands it.

That said, where do I buy a military Jump drive and power plant that take no penalty for unprocessed fuel?

 

[Spinward Flow]

This actually brings up the point of towing a ship, and I see in that light now that towing simply isn't a matter of beefing up the engines.

Correct.
The way that external fuel tanks "work" makes it APPEAR like this proposition is true ... but it's only PART of the story, not the entire narrative (so to speak).

If you don't have sufficient bridge volume, your control of the linked craft, tower and towed, will be imperfect.

Or it will be "ad hoc" in such a way that while "workable" might also be potentially "risky" if sufficient care, setup and testing is not performed (see 1 week delay required when "linking" 2 craft together for transport through jump when 1 of the craft is disabled and incapable of jump itself). Yes, it CAN be done ... but it's not something you want to try and do on the fly with little to no preparation.

How exactly that would play out, I can't speculate

Actual results will tend to vary WILDLY depending on context, so it's not like you can just write some RAW and have done with it.
The opportunities for "stuff to go wrong" when controls and/or preparation are inadequate to the task can get rather formidable.

but I can absolutely see towing ships with outsized, bulbous bridges because they need to monitor things on the towed ship as well as on their own ship.

This is the direction I'm moving in as well.
If you want to have a 2000 ton craft which is capable of externally towing a 10,000 ton hulk ... you're going to need a bridge setup rated for 12,000 tons on your 2000 ton tug.

OTOH, towing with an undersized bridge could be as innocuous as jumping with unprocessed fuel when your system's not set up for it.

Calling such circumstances "innocuous" might be a case of looking through the wrong end of the telescope.

Done "wrong" (somehow), I can easily imagine that jump tug towing with an undersized bridge could qualify as trying to jump within the jump shadow of a planet (surface to 10D limit, or 10D to 100D limit) depending on the details (because other craft have jump shadows!). Very much a case of the demonology depends on the details of the circumstances.

As a Referee, the KINDEST outcome that I can think of is that the jump drive winds up ... and the automatic safeties abort the attempt, resulting in a failure (if you don't have enough "bridge" for the combined tonnage you're trying to jump). Not quite a Millennium Falcon "no lightspeed" situation, but as close as you can get to it with a jump drive.

A small risk, and one you take if an emergency demands it.

Depends on context, circumstances, and ... let's be honest ... PLOT ARMOR™.
Forgive me for assuming that Plot Armor™ may, from time to time, be in short supply to any and all who might "need" it (or just want it, because it's convenient to have).

That said, where do I buy a military Jump drive and power plant that take no penalty for unprocessed fuel?

Short answer ... Referee Fiat when building using LBB2 standard drives.
Better answer ... if it's a Player crafted starship design, you don't.

Slightly "saner" answer ... you pull the military drives out of a military (or scout) ship class that are known use such drives for use in your own starship. The Type-S Scout/Courier is a (known) scout ship with A/A/A scout drives installed into it. The Type-J Seeker conversion simply retains those A/A/A scout drives.

So the answer to the "where do I buy military grade drives from?" question essentially comes down to an answer of ... from the secondhand and surplus market(s).

 

[Badenov]

Or it will be "ad hoc" in such a way that while "workable" might also be potentially "risky" if sufficient care, setup and testing is not performed (see 1 week delay required when "linking" 2 craft together for transport through jump when 1 of the craft is disabled and incapable of jump itself). Yes, it CAN be done ... but it's not something you want to try and do on the fly with little to no preparation.

It seems like it should be complicated and non-standard, however it's done. That said, I'm not sure how different it is from docking a ship onto a Lurenti and jumping? If a ship is designed with cargo tonnage that includes the carried ship, it seems the only real requirement is secure stowage like a Lurenti does all the time so the carried ship doesn't shift in transit. The most complicated part of that is if the disabled ship has structural integrity issues.

Actual results will tend to vary WILDLY depending on context, so it's not like you can just write some RAW and have done with it.
The opportunities for "stuff to go wrong" when controls and/or preparation are inadequate to the task can get rather formidable.

Seems like each GM would write the rules that make their campaigns flow the way they want to.

This is the direction I'm moving in as well.
If you want to have a 2000 ton craft which is capable of externally towing a 10,000 ton hulk ... you're going to need a bridge setup rated for 12,000 tons on your 2000 ton tug.

It seems like you're essentially going to design it like a 12000dT tug with a 10000dT load.

Calling such circumstances "innocuous" might be a case of looking through the wrong end of the telescope.

Depends on your campaign rules. If it's more like jumping inside the 100 Diam limit, it will get done much less.

Done "wrong" (somehow), I can easily imagine that jump tug towing with an undersized bridge could qualify as trying to jump within the jump shadow of a planet (surface to 10D limit, or 10D to 100D limit) depending on the details (because other craft have jump shadows!). Very much a case of the demonology depends on the details of the circumstances.

Very yes.

As a Referee, the KINDEST outcome that I can think of is that the jump drive winds up ... and the automatic safeties abort the attempt, resulting in a failure (if you don't have enough "bridge" for the combined tonnage you're trying to jump). Not quite a Millennium Falcon "no lightspeed" situation, but as close as you can get to it with a jump drive.

Depends on context, circumstances, and ... let's be honest ... PLOT ARMOR™.
Forgive me for assuming that Plot Armor™ may, from time to time, be in short supply to any and all who might "need" it (or just want it, because it's convenient to have).

The opposite to this is Plot Hook. Want to take the players someplace strange? Next time they try shenanigans, boom.

Short answer ... Referee Fiat when building using LBB2 standard drives.
Better answer ... if it's a Player crafted starship design, you don't.

But what if you're using a player-created design for the Navy?

Slightly "saner" answer ... you pull the military drives out of a military (or scout) ship class that are known use such drives for use in your own starship. The Type-S Scout/Courier is a (known) scout ship with A/A/A scout drives installed into it. The Type-J Seeker conversion simply retains those A/A/A scout drives.

So the answer to the "where do I buy military grade drives from?" question essentially comes down to an answer of ... from the secondhand and surplus market(s).

If only there were some difference you could see between them. Ah well.

 

[Spinward Flow]

If you want to have a 2000 ton craft which is capable of externally towing a 10,000 ton hulk ... you're going to need a bridge setup rated for 12,000 tons on your 2000 ton tug.

It seems like you're essentially going to design it like a 12000dT tug with a 10000dT load.

And this is where the distinction between internal and external comes to the fore.

A 2000 ton hull (with high performance drives) is going to cost MCr200 (base, before configuration modifier) in construction costs.
A 10,000 ton external load capacity is going to cost MCr20 on top of that for the external docking capacity (which will reduce drive performance when loaded).
A bridge rated for a 12,000 ton craft will require 240 tons and cost MCr60.

A 12,000 ton hull (with low performance drives) is going to cost MCr1200 (base, before configuration modifier) in construction costs.
A 10,000 ton internal hangar bay is going to cost MCr20 on top of that for the internal docking capacity (which does NOT reduce drive performance when loaded).
A bridge rated for a 12,000 ton craft will require 240 tons and cost MCr60.



The difference between the two design paths is that they'll have (functionally) the same drive performance when fully loaded either way ... but the "small ship, external loading" option has the option of high drive performance when not fully loaded ... while the "large ship, internal loading" has low drive performance whether it is loaded or not.

 

[Badenov]

And this is where the distinction between internal and external comes to the fore.

A 2000 ton hull (with high performance drives) is going to cost MCr200 (base, before configuration modifier) in construction costs.
A 10,000 ton external load capacity is going to cost MCr20 on top of that for the external docking capacity (which will reduce drive performance when loaded).
A bridge rated for a 12,000 ton craft will require 240 tons and cost MCr60.

A 12,000 ton hull (with low performance drives) is going to cost MCr1200 (base, before configuration modifier) in construction costs.
A 10,000 ton internal hangar bay is going to cost MCr20 on top of that for the internal docking capacity (which does NOT reduce drive performance when loaded).
A bridge rated for a 12,000 ton craft will require 240 tons and cost MCr60.



The difference between the two design paths is that they'll have (functionally) the same drive performance when fully loaded either way ... but the "small ship, external loading" option has the option of high drive performance when not fully loaded ... while the "large ship, internal loading" has low drive performance whether it is loaded or not.

Ah, yeah, I see that's inconsistent performance for two designs that are ostensibly the same. Higher performance for the unloaded version makes sense. On the other hand, a semi-tractor, while it has slightly better performance without the trailer, doesn't have substantially better performance. In CT, I don't think there's any advantage in larger size apart from the automatic criticals you'd avoid from very large batteries. I assume a smaller ship is much less expensive even if the engines are rated for the final combined mass. So the 'legal by the book way' (as I understand it) would be to make a distributed-hull ship at 12,000T that can carry loads 'outside' legally at 0% markup (which the more I read, the less I'm sure of - the way page 32 of Book 5 reads, is that Big Craft require 110% of their mass in the carrying ship, the 'no additional fittings' comment is directly related to the launch facilities - in a distributed hull external carriage, I can see the 10% extra tonnage being braces and cables and docking and securing equipment where in a normal ship that's hangar bay space.). Non-distributed hulls require a 110% of the subordinate craft's tonnage regardless, so we're avoiding that in this example.

If you allow subordinate craft/towing to be done some other way, i.e. with a 2,000T barge with oversized bridge and engineering section, you're avoiding paying for the tons of hull not installed to no purpose. your power plant is OK, but it seems like you ought to incur some cost in exchane for cheaping out on the original body.

 

[Grav_Moped]

Not to put too fine a point on things, but starships don't need maneuver agility (or weapons or screens) during jump.
In fact, the only onboard system that ought to be consuming EPs during jump ought to be the computer (if model/3+).

Point being that a starship with a model/1-2 computer spends EP: 0 on computer ... so during jump would only need to consume enough fuel for housekeeping/basic power (a mere 0.05 tons of fuel consumption per 7 days for a 100 ton hull).

The LBB2.77 design of the XBoat used a model/1bis computer (invalidated later by LBB5.80 and LBB2.81) since a CPU/Storage of 4/0 was all that was needed to run the required computer programs to achieve J4 out of the XBoat.

The basic problem here is that '81 obsoleted '77 where they conflict.
A power plant is required, and so is the fuel for it.

Also, baseline power consumption apparently changed in HG/LBB2'81. There is no "fuel use discount" for starships. Whether a ship spends a week (or two!) in Jump in a month, or is a non-starship that doesn't spend any time in Jump in that month, each requires 1%*Td*Pn (or 10Td/Pn) of fuel for 4 weeks operation.

My IMTU explanation is that you need to supply the jump drive with the EP from Pn=Jn (actual Jn, not rated Jn) to hold jumpspace at bay (misjumps are different though).

In '77, it's just 10T/Pn for "1 trip" (and that's essentally just maneuver fuel). HG made battleriders possible.

Correct.
But a Power Plant-A installed into a 100 ton hull with a 100 ton external load docked to it would not "automagically and retroactively" stop needing its 20 tons of power plant fuel requirement, transforming to only need 10 tons of power plant fuel as would be the case in a 200 ton Free Trader using the same drive.

The 200 ton Free Trader is a different design and class of starship, even if the drives used are exactly the same kind as the 100 ton Type-S Scout/Courier.

Yes, the drives are A/A/A in both classes of starship, but the fuel design requirements are different between them.

Again, it's a rules glitch (which is handwaved as in-universe regulation). I was describing a different fuel requirement for what would have literally been the very same piece of equipment, moved between two different hulls for comparison purposes.

But, as @AnotherDilbert puts it, LBB2's gonna LBB2. I munchkin around it to try to make it make sense even when it simply doesn't.

The extreme case of this would be to install a Size C power plant into a 600Td hull, where it'd be Pn-1 and need 10Td fuel. Then, remove it and remount it inside a 100Td hull, and then despite it being Pn-6, still only setting aside the 10Td fuel it required in the 600Td hull. Not legit, nor sensical. But it's where you end up by re-using the non-size-proportinal fuel formula that started in '77 and got papered over in '81.

The HG answer to this was, item by item, to rule that each and every specific starship component contributed nothing to fuel consumption.

 

[Spinward Flow]

On the other hand, a semi-tractor, while it has slightly better performance without the trailer, doesn't have substantially better performance.

To be fair, ground vehicle powered by ICE with transmission and wheels used for towing is a VERY DIFFERENT CONTEXT from mating two craft together in orbit by docking and then applying F=MA thrust to the combination on a specific vector.

The ground vehicle is "limited" by all kinds of engineering constraints (RPM, torque, transmission losses, power to load matching at speeds, contact patch friction limits on wheels, etc. etc. etc.) that simply do not apply when in orbit in space (with no friction worth mentioning and effectively in free fall). In space, it's all about F=MA thrust vectored through the center of mass (miss the center of mass with your vector and you start spinning).

In space, the F=MA reality is that if you 1/2x of the Mass (or in the CT context, combined displacement) you 2x the Acceleration from the exact same amount of Force.

This is why A/A/A drives are codes: 2/2/2 in a 100 ton hull (see: Type-S Scout/Courier) and the exact same type of A/A/A drives are codes: 1/1/1 in a 200 ton hull (see: Free Trader).
2x the mass (or displacement) = 1/2x the acceleration

In CT, I don't think there's any advantage in larger size apart from the automatic criticals you'd avoid from very large batteries.

Well, that's a COMBAT consideration, as opposed to being an economic/merchant type of reason.

I assume a smaller ship is much less expensive even if the engines are rated for the final combined mass.

The SHIP will.
However, if you're doing a modularized container system (like I am) you're "still paying for" the hull metal somehow.

Falling back on the napkin math I was using before:

• A 2000 ton craft pays MCr200 for its hull (before configuration modifiers)
• A 12,000 ton craft pays MCr1200 for its hull (before configuration modifiers)

So the hull construction cost for the tug itself is lower.
But if that tug is intended to tow 10,000 tons of "other hulls" around externally, those "other hulls" have to be paid for too (potentially by third parties).

So what you wind up with is something akin to a railway "locomotives and rolling stock" type of business model. The locomotives can be owned by one business, but the passenger coaches and box cars/tanker cars/flatbeds/etc. can be owned by entirely separate third party businesses, with everything being run around on the same railway lines.

In modern (real world) business practice, this is what has happened with containerized shipping by sea. The shipping companies build and operate the MASSIVE container ships, while third parties "own" most of the shipping containers that are used for transportation of goods ... and the contents of those shipping containers are filled up with "stuff" by yet MORE third parties who want to move their goods around by ocean going ships. No single company has the entire operation vertically integrated (completely) from container ship to containers to goods to fill the containers with. Some are more vertically integrated than others, but there's a LOT of "investments by third parties" possible in the containerized shipping business model, since no ONE company has to "do it all" in terms of investment and overhead.

My point being that even if the 2000 ton tug is smaller (and therefore, cheaper) to buy, once you add in the price of the hulls for the "barges" that the tug is going to be maneuvering around, that cost advantage diminishes. It doesn't disappear completely, but it's not as dramatic as the MCr200 vs MCr1200 comparison I was making above, because there's additional CONTEXT beyond the tug itself when you're dealing with external loading scenarios.

the more I read, the less I'm sure of - the way page 32 of Book 5 reads, is that Big Craft require 110% of their mass in the carrying ship, the 'no additional fittings' comment is directly related to the launch facilities - in a distributed hull external carriage, I can see the 10% extra tonnage being braces and cables and docking and securing equipment where in a normal ship that's hangar bay space.

I view the 110% for Big Craft requirement as being "always operative" regardless of tender configuration.

So a 12,000 ton configuration: 7 tender can allocate 9900 tons for facilities to dock 9x 1000 ton Big Craft which can all be launched and recovered in a single combat turn (because, configuration: 7). If a tender wanted to accommodate a 10,000 ton Battle Rider, the tender would need to devote 10,000*1.1=11,000 tons to the docking facilities necessary for that purpose, regardless of tender hull configuration (and whether those facilities were accounted for as being "internal or external" to the hull with regards to berthing/towing). It's just that a configuration: 7 tender can "launch and recover EVERYTHING" in a single combat turn, unlike all other hull configurations which have launch and recovery constraints/limitations.

If you allow subordinate craft/towing to be done some other way, i.e. with a 2,000T barge with oversized bridge and engineering section, you're avoiding paying for the tons of hull not installed to no purpose. your power plant is OK, but it seems like you ought to incur some cost in exchange for cheapening out on the original body.

Somebody still has to pay for the hulls of the external loads.
The tug/tender might be cheaper, but the barges still need to be paid for (by someone) in order to exist.

Which is why I've gone to such pains as to define the modularized container form factor in my research in this thread ... and settled on the 16 ton form factor as the "best biggest small that is also the smallest big" (if that makes any sense) building block unit for interstellar trade because of how multi-purpose the form factor winds up being. Under CT, the 16 ton form factor "works wonders" up until you reach the point where your combined overall tonnage exceeds 1000 tons (starship+external loading), at which point a different solution becomes preferable/more economical. At over 1000 tons, the market incentives switch back towards "internal cargo" accounting due to a variety of "efficiency" factors.

But for the ACS "small time free trader/speculator" market, external loading and containerized shipping makes for an extremely compelling business model for what amount to "mom & pop" type independent operators working the "lower end" of the interstellar trade economy. It makes it possible to design "flexible" starships that can survive and thrive in a variety of world market conditions that would be difficult for a more "one size fits all" type of starship to profit from quite so reliably.

In other words, there's a niche/boutique market for these kinds of ACS designs that I'm coming up with.