Pondering starship evolution

[Spinward Flow]

Without reading through 400+ posts ... why are the "boxes" 16 dtons? (Why not 20 dTons or 10 dTons or 36 dTons or any other base value?)

The answer to that question lies within the 400+ posts that you're not reading.
But you're asking for a summary as a latecomer to the thread ... which is a fair ask.

For any kind of modularized "shipping container" useful for interstellar commerce, you first need to establish what is the "minimum useful displacement" for the job you want to be doing. The "solution" to this particular balancing act has multiple possibilities, each of which have their own strengths and weaknesses.

I started my research into this topic with some Traveller immutable assumptions.

• Major cargoes are 10 tons (minimum) per lot (LBB2.81, p8) (TTB, p53)
• Minor cargoes are 5 tons (minimum) per lot (LBB2.81, p8) (TTB, p53)
• Incidental cargoes are 1 ton (minimum) per lot (LBB2.81, p8) (TTB, p53)

This means that any "cargo container module" of less than 10 tons displacement would "not be useful" for shipping major cargoes, rather effectively defeating the purpose. So a 10 ton displacement becomes something of a "hard" lower bound for interstellar modularized container transport.

The next consideration to take account of is the possibility of putting staterooms (for crew or passengers) into these modular containers that are being designed. This becomes both a spreadsheet (multiples of 4 tons) and a deck plan "interior design" problem. For example, it's EASY to specify in a spreadsheet that a 12 ton cylindrical "tube" hull has 3 staterooms in it, but when you try to draw up deck plans for that, every gets WONKY and WEIRD really quickly because there's going to be so much "wasted space" involved around the curves of the tube shape. Even if you do a "two decks in the tube" with an over/under on one side and a "mid-deck access hallway" running along one side (to waste as little volume as possible) you still have a variety of mobility and access issues getting into those staterooms ... not to mention the odd number of them (3). Sure, that can be partially solved by making 4 compartments (3 quarters plus 1 common area) in order to try and balance things out, but the deck plan arrangement of "stuff" gets FUGLY really fast.

Also, if you're building "tubes" those don't exactly "stack neatly" into arrays with minimal packing losses between them, even if you're doing hexagons.

So rectilinear shapes (meaning Configuration: 4, close structure) became the obvious choice for the purpose.
Basically, one of these ... (albeit with different dimensions):

For a while, the 12 ton Box seemed like it would be the optimal choice, because it would be the "right size" for 3 staterooms while also being able to load at least 10 tons of cargo.

Additionally ... 12*14/3/1.5/1.5 = 24.89 ... in other words, a 5x5 deck squares deck plan, which worked out beautifully for 2x2 arrays of "square" boxes (rotate the top layer 90º and you only need a single central corridor access along with a single central vertical access).

So the deck plan for a 12 ton Stateroom Box would look like this (3 crew or passenger quarters plus 1 common area):

The problem with that "solution" was that it was nearly impossible to build a useful fighter craft within those constraints (tonnage and form factor). This created a "wrong size mismatch" problem of interchangeability when using modularization at this scale. It was good for Stateroom Boxes, but little else.

Then in post #246, I got the bright idea to try a 20 ton form factor instead, to help resolve the differences in displacement between Boxes and Fighter.

At that point, the Stateroom Boxes turned into this:

The Escort Fighter went from looking like this:

To looking like THIS in order to fit into the new form factor constraint:

And then THIS:

But all of that work was being done on a foundational assumption of building a TL=10 starship using LBB2.81 E-H drives (of some variety) and a TL=10 escort fighter that could have been originally designed for system defense patrols, which then gets adapted and redesigned (deckplan only, not spreadsheet numbers) for use as a mobile defense for merchant starships that need to go "across the border" outside of imperial controlled space.

I was still working on the assumption of doing an "odd number plus one" in order to make the interior design deck plans have bilateral symmetry to them, in terms of where the internal bulkheads/partitions ought to go. So that's how you wind up with 5 staterooms (20 tons) that collectively yield 1 common area (either a lounge/galley/laundry, or a sick bay/medical).



However, after doing all of this (and building another complete starship deck plan) ... I started wondering about backwards compatibility, from TL=10 down to TL=9. Dropping -1 TL like that would put some pretty severe constraints on the design parameters (no model/4 computer for the fighter, fuel purification plants are 9 tons minimum rather than 8 tons, LBB2.81 drives are limited to A-D, etc.), so ensuring "backwards compatibility with the Stone Age J1 Discovery Era" meant questioning all of the assumptions I'd been making yet again.



And then in post #364, I was basically "forced" by the backwards compatibility criterion with TL=9 to re-evaluate and came to the conclusion that I should have been working in 16 ton Box form factors all along.

Why?
Because a TL=9 Escort Fighter armed with lasers (so it doesn't have ordnance resupply issues) and a model/2 computer plus bridge just so happens to weigh in at 16 tons of displacement. And Agility=6 in a 16 ton form factor costs 16*0.06=0.96 EP, leaving 1 EP (power plant-A drive generates 2 EP) or 3 EP (power plant-B drive generates 4 EP) available to power weaponry+computers (model/2 consumes 0 EP).
Additionally, 16 tons means 4 staterooms.

The challenge then was to figure out how to get 4 staterooms plus common area(s) into a deck plan that made sense.

Furthermore ...

• 1 Major Cargo (10 tons) + 1 Minor Cargo (5 tons) + 1 Incidental Cargo (1 ton) = 16 tons

The new form factor is 392 pixels long by 304 pixels wide on the deck plans (corner to corner).
That means that when 60 pixels=1.5m the dimensions are 9.8m x 7.6m x 3m (~29% longer than wide).
9.8*7.6*3/14 = 15.96 ≈ 16 tons

Without reading through 400+ posts ... why are the "boxes" 16 dtons? (Why not 20 dTons or 10 dTons or 36 dTons or any other base value?)

TL;DR
By process of Pondering Starship Evolution ... and thinking in terms of more than one tech level (specifically, TL=9-10).

Side benefit ... this means that I can design a TL=11 Medium Fighter "upgrade" that is 32 tons (2x 16) which has a model/5 computer in it while still using LBB2.81 standard drives.

• LBB2.81 Power Plant-C drive generates 6 EP
• Agility=6 in a 32 ton form factor consumes 32*0.06=1.92 EP
• Computer model/5 consumes 3 EP
• 1x Pulse Laser consumes 1 EP
• + (6) - (1.92-3-1) = 0.08 EP remaining surplus

This would then represent the "zenith" for system defense fighter performance, since at TL=12+ small craft fighters become less and less relevant for military fleet on fleet use. After TL=11, it becomes increasingly difficult to justify the "expense" that fighters represent, since they're basically "flying computers with only a single turret" while big craft (100+ tons) can mount more weapons per computer (and are thus a more efficient use of limited budgets).

Does that (adequately) answer your question?

 

[atpollard]

Does that (adequately) answer your question?

Yup. Thank you.

Setting aside the Fighter (which I would have to test the design to see if a 16 dT TL 9 fighter made sense or not and if a "cube" is a "cool" form for it; but giving it the benefit of the doubt) ... The arguments that 16 dTons = CARGO (1 major + 1 Minor + 1 incidental) = STATEROOMS (4 staterooms) provides innate merit to 16 dTons over other values.

 

[Spinward Flow]

The arguments that 16 dTons = CARGO (1 major + 1 Minor + 1 incidental) = STATEROOMS (4 staterooms) provides innate merit to 16 dTons over other values.

Suffice it to say, it wasn't an abritrary decision nor a capricious one.
Instead, it's the result of searching among a confluence of factors to strike the right balance between them. It's a matter of "following the math" when taking account of lots of different competing inputs.

There's also a desire to min/max in order to find the "biggest small" that is also the "smallest big" (or words to that effect).
The fact that 100/6=16.6667≈16 is also thrown into the mix. That way, Agility=6 @ 16 tons costs 0.96 EP ... which is as close to 1 EP, without going over, as you can get.

So there's multiple overlapping breakpoints which make 16 tons a decent compromise to settle upon.

 

[atpollard]

The fact that 100/6=16.6667≈16 is also thrown into the mix. That way, Agility=6 @ 16 tons costs 0.96 EP ... which is as close to 1 EP, without going over, as you can get.

THAT makes a 16 dTon small craft a figure of merit [whether a FIGHTER or just a FERRARI].

IN MY UNIVERSE (where there exists a Half-A Drive because 100 dTon hulls at Factor 1 just make sense), that suggests a 6G performance at 16 dTons.

 

[Spinward Flow]

THAT makes a 16 dTon small craft a figure of merit [whether a FIGHTER or just a FERRARI].

"Trust me. I know what I'm doing."

that suggests a 6G performance at 16 dTons.

Yup.
That's the idea.
6G Agility=6 for 1EP @ 16 tons.

Which means, that 16 tons is the Just Right™ size for:

• 1x Major Cargo lot (10 ton minimum) + 1x Minor Cargo lot (5 ton minimum) + 1x Incidental Cargo lot (1 ton minimum)
• 4x Staterooms (16 tons)
• 6G Fighters (1 EP needed for Agility=6)
• 2x G-Carriers (8 tons each)
• 1x G-Carrier (8 tons) plus 2x Air/Rafts (4 tons each)
• 2x Speeders (6 tons each) plus 1x Air/Raft (4 tons)
• 4x Air/Rafts (4 tons each)
• 1x Mail Vault (5 tons) plus 1x Speeder (6 tons) plus 10x Low Passenger Berths (5 tons)
• ... and even more possible combinations ...

So in terms of "hitting a sweet spot" ... 16 tons is a pretty sweet spot to be in.

 

[RossWinn]

lovely ideas, but there are no closets or room for any luggage of any kind.

 

[kilemall]

lovely ideas, but there are no closets or room for any luggage of any kind.

He has one.

 

[Spinward Flow]

there are no closets or room for any luggage of any kind.

Actually, that's not true.
Each stateroom has a closet for use by the occupant.
If you're not familiar with the visual language of Geomorphs, that's fine ... I don't mind explaining what isn't intuitively obvious at a first glance.

The Galley has a refrigerator/freezer (forward is picture left) and a dry stores "pantry" (aft is picture right) in it for the storage of foodstuffs. The galley has a sink + countertop forward as well as a 4 "burner" magnetic induction stove top convection oven (by the entrance) next to a heat pump washer/dryer laundry machine (by the stores), the top of which can be used for additional counter/staging space when cooking. The Galley space is "barely a closet" itself, in terms of having room to move about it in, but it's adequate to meet the needs of 4 single occupancy staterooms when it comes to meal preparations and laundry services.

 

[TamsinP]

lovely ideas, but there are no closets or room for any luggage of any kind.

I'm assuming there would be drawers underneath each of the bunks and cupboards under (and possibly on the wall above) what I assume to be the desk for storage of luggage.

 

[Spinward Flow]

I'm assuming there would be drawers underneath each of the bunks and cupboards under (and possibly on the wall above) what I assume to be the desk for storage of luggage.

That ... would not be a correct assumption.

The bunks are a "loft" type of arrangement over the sitting area, comparable to (but not exactly like) what you see in Amtrak passenger trains.

The "sitting area" under the "loft bunk" has a retractable into the floor table between two couch seats on either side. The couches can be folded out to create a bed for a second occupant (like is shown in the above image) if double occupancy is required.

These updated deck plan images, which "remove" the loft bunks at the bottom of the images (for clarity, the bunks are still there), helps make this a bit easier to see.

The outer bulkhead has a window and a privacy screen/retractable curtain (which also doubles as a radiation shield), allowing occupants to visually see vistas and spectacles outside when the Stateroom Box is docked externally to other craft.

Closet space is provided against the interior bulkhead wall of each compartment, opposite the private fresher in each stateroom. A portion of each closet is dedicated to the storage of a vacc suit and rescue ball, in case of a need to depressurize interiors in preparation for combat (vacc suit) or in case of unplanned emergency (rescue ball), permitting a "shelter in place" option until rescue can arrive. The remainder of the floor to ceiling closet space is available for stateroom occupants to fill with their personal effects and luggage.

Each stateroom compartment is "pressure isolated" from other sections, allowing occupants of each stateroom to control environmentals (temperature, gravity, etc.) individually as desired.

 

[aramis]

It was never "a rule" (per se), but it has always been a Default Assumption in almost every version of Traveller published. It even extends down into small craft, such that all small craft "have to be" Multiples Of 10 in their tonnages.

Every single design sequence in CT adhered to these "rules" for design (LBB2, LBB S4, LBB S7, LBB S9, LBB A1, LBB A4, LBB A8, LBB A10, CT AM1-8, etc.). It simply became Accepted Conventional Wisdom™ that all displacement tonnages come in Multiples Of 10 (small craft) or 100 (big craft).

In fact, one of the precious few designs to break with this pattern is (of all things) the Colonial Cruiser (LBB S9, p19) ... weighing in at 1250 tons ... instead of the 1200 tons published in LBB A1.

So everyone got into the habit of using Multiples Of 10 or 100 every time ... because that's what the published designs did.

You've cherry picked and/or missed a few. The first ed of Bk5 has fighter sizes that don't match.
TL7-9 fighters are 9 tons, not 10. TL10+ are 10, but not the early ones. (but also, no small craft design.)

Bk5 second ed has a 1250 Ton example... page 51
And a 35 ton Pinnace on the next page.

AHL includes details on the Rampart fighter, Supplement 5, page 40. 15 Td.

Further Bk2, both editions, allows for hulls of interim sizes... but without any benefit for unlisted tonnages, and it's only 100 to 1000 where its by hundreds. it's thousands to 5k.
And Bk5, the size table does support a log function... hundreds to 1000, thousands to 10k, 10k to 50k, 25k from 50k to 100k, then 100k to 1M.

These are clear proof your thesis is wrong.

The design sequences in Bk5 do set some granularity that matters...
Given that it's round up to 1 ton for ships means that JDrives round up by the 50 ton... for even drive numbers; per hundred for odd.
Maneuver Drives optimize by the 100 ton as well.
Turrets likewise optimize by the 100 ton, excepting when using bays. (A common misinterpretation of Bk5 is that tonnage of bays simply doesn't count towards turret ratios, rather than preventing 1000 tons from counting for turrets, and thus blocking 10 turrets each. So a 1050 Td, under that misinterp, could have 1× 50 Td and 10× Turrets or barbettes.)

Now, aside from Bk5-79, I've not seen published small craft in units other than 5 Td, nor ships other than in 50 ton increments. That counts the GW, GDW, and JG pubs for CT.

Also worth noting: TNE includes a few of 50-ton increment designs, so GDW felt no compunctions about breaking the "100 ton rule"... RCES Equipment guide has...
Aurora Clipper: 600/1080/2080 tons (depending upon configuration)
Maggert Clipper: 850/2750 tons (d.o.c.)
3 Ton Socket Lifeboat
5 Ton Liferaft
Wildbat/Foxbat matched fighter and "pathfinder" - both 16 tons.
Fury Assault Lander: 7 tons.
Hiver Tender: 4800/5000 tons

Regency sourcebook adds
RQS Faith Class 150 Ton quarantine cutter.

 

[mike wightman]

Here are a couple more.
The fighters carried by the Broadsword cutter fighter frame are 6 tons each
And the fighters carried by Zhodani patrol craft are 8 tons.

 

[Condottiere]

Obviously going for minimum tonnage, for a given payload.

Observing spacecraft design (component) minimums, depending on edition.