Ship tonnage

[Tobias]

This is an idea based on the reduced dton concept swiped from Anders Backman (https://vectormovement.com/).

Basically, the idea is to re-define a dton as two metric tons. For example, a Free Trader with a standard load, would have a mass of 400 metric tons.

Ship sizes are brought in line by re-defining one deck plan square as 1x1 meters, with a space between decks of 2.5 meters. This makes a "dton" about 5 cubic meters, and the average net density of ships thus about 0.4. Of course, there is lot of leeway since the governing statistic is mass, not volume.
Ships will obviously be a lot more cramped: More "sleeper car" or "submarine" than "Starship Enterprise".

Why? a.) To bring ships more in line with vehicles (also includes weapons, since energy points would be similarly downscaled). b.) To use mass as the relevant characteristic, which solves a lot of problems without generating new ones, and c.) to make ships smaller and less hotel-like for a more frontier feel.

The other option I pondered was defining the dton as five metric tons while leaving the volume and deck plan scale as it is (i.e. 1.5x1.5.x3).

Thoughts?

 

[whartung]

Hotel like?

You can barely get a shopping cart down a 1.5m hallway. The 4 dTon, with a 3m high ceiling is ~200sq feet which is in line with a 150 sq foot cruise ship cabin, never really renowned for their wide open spaces. And don't forget that the 4 dTon stateroom is including other ancillary stuff not necessarily within the cabin itself. And, yea, 3m ceiling height is a bit generous. Hotels seem to average over 325 sq feet.

No, a stateroom isn't bunking with the torpedoes in the forward torpedo room, or hot bunking with Chet "Stinky" McFarland.

But I don't know if I'd consider it hotel like.

Finally, we have unlimited power which means weight is not a real constraint to performance, hulls are reasonably cheap all told, so there's no real need to squeeze everyone into the ship like a sardine.

 

[Tobias]

Hotel like?

Yes.

You can barely get a shopping cart down a 1.5m hallway. The 4 dTon, with a 3m high ceiling is ~200sq feet which is in line with a 150 sq foot cruise ship cabin, never really renowned for their wide open spaces. And don't forget that the 4 dTon stateroom is including other ancillary stuff not necessarily within the cabin itself. And, yea, 3m ceiling height is a bit generous. Hotels seem to average over 325 sq feet.

I don't know what kind of shopping carts people use in the US, but around here they are about 60 cm (~2 feet) wide. A 1.5 meter hallway is actually pretty wide.
Cruise ship cabins almost always provide bedding for two, and even those that don't typically have a king-sized bed. Cabin space per person is about 6-8 square meters (~10 times in square feet), which would be the space they'd have in my scheme.

No, a stateroom isn't bunking with the torpedoes in the forward torpedo room, or hot bunking with Chet "Stinky" McFarland.

That would be a whole other step down. I meant modern submarines (or smaller types of modern surface warships.)

But I don't know if I'd consider it hotel like.

Depends on the hotel. I've slept in hotels even less spacious (capsules) but granted, I wouldn't want to spend weeks in such accommodations. I did spend weeks (months even) in similarly cramped conditions when serving in the navy.

Finally, we have unlimited power which means weight is not a real constraint to performance,

That's not a paradigm I'm following, but...

hulls are reasonably cheap all told, so there's no real need to squeeze everyone into the ship like a sardine.

... hull volume, under the standard technical parameters, is directly proportional to the cost of propulsion, which is the major cost factor. There is thus ample reason to conserve space whereever possible.

 

[atpollard]

This is an idea based on the reduced dton concept swiped from Anders Backman (https://vectormovement.com/).

Basically, the idea is to re-define a dton as two metric tons. For example, a Free Trader with a standard load, would have a mass of 400 metric tons.

Ship sizes are brought in line by re-defining one deck plan square as 1x1 meters, with a space between decks of 2.5 meters. This makes a "dton" about 5 cubic meters, and the average net density of ships thus about 0.4. Of course, there is lot of leeway since the governing statistic is mass, not volume.
Ships will obviously be a lot more cramped: More "sleeper car" or "submarine" than "Starship Enterprise".

Why? a.) To bring ships more in line with vehicles (also includes weapons, since energy points would be similarly downscaled). b.) To use mass as the relevant characteristic, which solves a lot of problems without generating new ones, and c.) to make ships smaller and less hotel-like for a more frontier feel.

The other option I pondered was defining the dton as five metric tons while leaving the volume and deck plan scale as it is (i.e. 1.5x1.5.x3).

Thoughts?

Mass does nothing for verisimilitude except MOVE the "handwavium" to a new location:

"Specifically, to meet the 20 mSv/yr and 6.6 mGy/yr limits our calculations suggest that 6-7 tonnes of water or polyethylene radiation shielding per square meter of hull is sufficient in deep space, such as at L5" - The National Space Society

... in the end, Traveller is still 90% 'Space Opera' with a thin veneer of 'hard science' to cover the fact that the "Emperor has no clothes".

[So it is a fine alternative, but just creates a "different" feel, not a more "realistic" one. Sort of like the THRUST vs REACTIONLESS MD Question ... both are "magic" when you try and look under the hood with Physics, because REALITY is a boring "after 5 month of travel, the ship arrives at the Gas Giant, ready to explore a lifeless moon."]

 

[Tobias]

Mass does nothing for verisimilitude except MOVE the "handwavium" to a new location:

"Specifically, to meet the 20 mSv/yr and 6.6 mGy/yr limits our calculations suggest that 6-7 tonnes of water or polyethylene radiation shielding per square meter of hull is sufficient in deep space, such as at L5" - The National Space Society

I fail to see what that has to do with this concept.

 

[atpollard]

Cruise ship cabins almost always provide bedding for two, and even those that don't typically have a king-sized bed. Cabin space per person is about 6-8 square meters (~10 times in square feet), which would be the space they'd have in my scheme.

Setting aside ceiling height and focusing on floor space ...
One grid (1.5 x 1.5 m) is within spitting distance of a 5' x 5' square. So the area available for 1 standard passenger (2 in a pinch) as 4 dTons is eight of those squares (200 sf). In the real world, we have a 22' long travel trailer that comes close to that area. So HERE is your living space for the next 7 days when they bolt the door closed.

If they combine the "common room area" from multiple staterooms into a shared Living/Dining area, your "Private Stateroom" is closer to a 12' travel trailer:



How much SMALLER do these spaces really need to become? We are locking human beings in the back of a U-Haul for a week for the price of a voyage on the Titanic.

 

[atpollard]

I fail to see what that has to do with this concept.

Perhaps this would be simpler:

Thoughts?

Why change volume to mass and make things smaller? For what purpose/goal?

 

[Tobias]

First of all: My original idea was to simply use tonnage = mass in metric tons - as it was widely understood from the 1977 rules, the volume-based "ton" only debuting with HG1 (AFAIK). But ships seemed a bit too light then, so this 1:2 factor was a compromise.
I should also note that I'm happily throwing Striker-based technology assumptions, especially about armor materials, out the window here.

Perhaps this would be simpler:

Why change volume to mass and

Makes more sense for propulsion, gives you a lot more wiggle room for drawing ships. With volume as the technical set-in-stone factor, your deckplans are bound to be plain wrong (and almost all of the official ones are).
BTW, shielding is the same problem whether your defining resource is volume or mass, so it's got no impact. FWIW, I assume that Traveller ships have a magnetism-based solution to the radiation problem.

make things smaller? For what purpose/goal?

Firstly, to ground spacecraft a bit more (figuratively). In CT, even the smallest starships are often portrayed as this complete class of their own (with the 250 Mw standard laser being an absolute monster weapon by vehicle scale etc.); this change brings them more into line with vehicles.
Secondly, to give space travel a more gritty and frontier feel without upending the entire concept of it in the OTU. I like the feel of spacers being used to living in really cramped spaces. Late CT/MT onwards (TNE pulled back a bit), spaceship life seemed very "Star Trek TNG" as I said. While I love Star Trek TNG, I'm shooting for a bit of a different feel here.

 

[Dragoner]

Realistic specific gravity density would be closer to 0.25 tonnes to m^3, which would come out to about 3.5 t to dt, and while a normal hall is around 1 m, if you want two personnel in equipment, say vacc suits to be able to pass each other, 1.5 is closer to reality for fire codes (for Fire Fighters to pass each other) here in the US; though in Europe, they are not as strict. Cabins are usually 2 dt on plans, with the other 2 being hallway space and such; somehow that would have to be made up.

 

[Tobias]

Realistic specific gravity density would be closer to 0.25 tonnes to m^3, which would come out to about 3.5 t to dt, and while a normal hall is around 1 m, if you want two personnel in equipment, say vacc suits to be able to pass each other, 1.5 is closer to reality for fire codes (for Fire Fighters to pass each other) here in the US; though in Europe, they are not as strict. Cabins are usually 2 dt on plans, with the other 2 being hallway space and such; somehow that would have to be made up.

Passageways on warships, for which firefighting is a crucial consideration, are nowhere near 1.5 meters wide. (In fact, my knowledge of these is one of the reasons I think ~1 m is very reasonable.)

In any event, the great thing about using mass as the governing characteristic is that you have leeway here. Make cabins 20% larger, other parts smaller, no big deal.

 

[Tobias]

How much SMALLER do these spaces really need to become? We are locking human beings in the back of a U-Haul for a week for the price of a voyage on the Titanic.

Erm... mind checking out the size of second or even third class accomodations on the Titanic?
And nobody's locked into anything. That's what common areas are for. Of course one major issue with space travel is that you can't go above deck to get some fresh air.

 

[Dragoner]

Passageways on warships, for which firefighting is a crucial consideration, are nowhere near 1.5 meters wide. (In fact, my knowledge of these is one of the reasons I think ~1 m is very reasonable.)

In any event, the great thing about using mass as the governing characteristic is that you have leeway here. Make cabins 20% larger, other parts smaller, no big deal.

Which is another consideration, a warship vs a non warship.

 

[Tobias]

Realistic specific gravity density would be closer to 0.25 tonnes to m^3,

Do you mean for real spacecraft?
Because that would work too, for me, since I then could just use ton = metric ton of mass as I originally intended to.

And yes, the difference between civilian and military craft would figure into it too. Here, too, you can use the leeway provided by this scheme to provide more spacious accessways around accommodations for civilian craft (for comfort) and more around machinery for military craft (for damage control).

 

[Condottiere]

Volume is a consideration, since engineering performance is based on that, rather than mass.

Bulkheads could be more about atmospheric loss in passenger ships, rather than buoyancy.

 

[Dragoner]

Do you mean for real spacecraft?
Because that would work too, for me, since I then could just use ton = metric ton of mass as I originally intended to.

It would be around 14/4=3.5; figuring components such as in engineering, the hull likely milled aluminum and composite. Though a warship would be closer to 0.5.

 

[Tobias]

Volume is a consideration, since engineering performance is based on that, rather than mass.

Not in this IMTU, it isn't. Drive performance would of course be tied to mass. In fact, everything including design systems would stay the same, except being keyed to mass rather than volume.

 

[Tobias]

It would be around 14/4=3.5; figuring components such as in engineering, the hull likely composite. Though a warship would be closer to 0.5.

I've crunched the numbers for a downsized scout/courier. It would be 333.33 m³ (give and take a bit for turret and other stuff).
If tonnage = metric tons, net density would be 0.3. (Note that the standard sized scout/courier is only about 80 dtons by measurement.)
Unfortunately, most other small ships are not as easy to compute because they are not simple geometric shapes.

 

[TamsinP]

333.33 m^3 works out as 83.49 GT/117.72 GRT, smaller than most tugs and fishing boats, and smaller than a WW2 PTB.

 

[Tobias]

333.33 m^3 works out as 83.49 GT/117.72 GRT, smaller than most tugs and fishing boats, and smaller than a WW2 PTB.

Yeah, it'd be quite a small ship. For IMTU purposes, that would be just fine.
On the other end of the spectrum, a 100,000 ton ship would be ~333,0000 cubic meters, or 117,000 GRT.

 

[TamsinP]

117,000 GRT would be a bit bigger than the Nimitz and Ford class carriers, and about half the size of a 2nd generation Maersk Triple-E class (20,568 TEU) container ship without any containers above deck.