HG 2e Medical Bay and Central Supply Catalog (CSC) Autodoc

[AnotherDilbert]

I suspect it's more like spacecraft turrets and small (ground vehicle) weapon systems: a space is allocated for every quarter tonnes, anything more it gets overflows into another space; default is upto a quarter tonne per space.

The only conversion that will be necessary is to turn the Mass of each weapon (usually listed in Kg or tons) into Spaces. This is done at a rate of 1 Space for every 250 Kg or 0.25 tons of Mass or part of.

So, for example, a light autocannon has a Mass of 0.25 tons, which is equal to 1 Space. An orbital defence cannon has a Mass of 35 tons, which is equal to a whopping 140 Spaces!

[NOLATrav]

I understand the difference between Mass and Volume but I’ve been using the 250kg = 0.25 tons rule for everything - weapons on vehicles, cargo, how many map squares big animals take up, etc. Haven’t hit any real snags yet and it provides a basic conversion factor which is handy.

[snrdg121408]

Hello AnotherDilbert,

Thank you for the reference on how to determine the spaces for vehicle handbook weapons and spacecraft weapons is found in Section 4 of the Vehicle Handbook (VH) page 44/PDF page 45.

[Condottiere]

These design sequences are abstract.

If one cubic metre of steel weighs in at seventy hundred kilogrammes, a quarter tonne would require that to be divided by about sixteen, which is what, the size of a Christmas present?

No weapon system is exactly a quarter tonne, which a surprisingly number are in Traveller; personally, I wouldn't care if that didn't force me to tweak them to achieve a mass below that threshold, since anything that is a quarter tonne, automatically requires the entire one tonne allocated to the spacecraft turret.

If the budget version of the orbital defence cannon had a mass of forty two tonnes, plus a ten kilogramme targetting computer, it would require one hundred and sixty nine spaces.

And if you consider the high explosive bomb, it's a tad above a hundred kilogrammes, and requires one space.

If a passenger weighs in at Terran standard gravity 255 kilogrammes, or 562 pounds, can he still fit? Because if it isn't standing room only, you have to add in the weight of the seat.

[snrdg121408]

Hello Condittiere,

These design sequences are abstract.

If one cubic metre of steel weighs in at seventy hundred kilogrammes, a quarter tonne would require that to be divided by about sixteen, which is what, the size of a Christmas present?

No weapon system is exactly a quarter tonne, which a surprisingly number are in Traveller; personally, I wouldn't care if that didn't force me to tweak them to achieve a mass below that threshold, since anything that is a quarter tonne, automatically requires the entire one tonne allocated to the spacecraft turret.

If the budget version of the orbital defence cannon had a mass of forty two tonnes, plus a ten kilogramme targetting computer, it would require one hundred and sixty nine spaces.

And if you consider the high explosive bomb, it's a tad above a hundred kilogrammes, and requires one space.

If a passenger weighs in at Terran standard gravity 255 kilogrammes, or 562 pounds, can he still fit? Because if it isn't standing room only, you have to add in the weight of the seat.

You are correct that the design sequences based on CT are abstract which allows for easier and quicker designs and game playing. The abstraction, in theory, also makes laying out deck plans easier.

[snrdg121408]

Hello all,

While searching CT LBB 2 1977/1981 for something else I found this reference on pages 20-21.

Building Ships
1. Custom hull with mass displacements other than the hull sizes shown on the drive potential table are treats as the next larger hull size. The maximum hull possible in these rules is 5,000 tons."

IIRC mass is measured, using the metric system, in grams, kilograms, and metric tons.

If I am remotely in the ball park the scout/courier is 100 metric tonnes.

On CT LBB 2 1977/1981 page 17 a sand canister weighs 50 kg or 0.05 tonnes.

Jumping back to page 21 Deck plans has the following information: "...The preferred scale for the interior should be 1.5 meters per square, with space between decks put at about 4.0 meters. One ton of ship displacement equals approximately 14 cubic meters. Therefore one ton equals about two squares of deck space...."

A CSC autodoc is 500 kg which is 0.5 metric tonnes which appears to mean the autodoc requires approximately 14 cubic meters x 0.5 = 7 cubic meters of 1 interior square of space.

How foar off course am I on this one?

[AnotherDilbert]

Building Ships
1. Custom hull with mass displacements other than the hull sizes shown on the drive potential table are treats as the next larger hull size. The maximum hull possible in these rules is 5,000 tons."

IIRC mass is measured, using the metric system, in grams, kilograms, and metric tons.

If I am remotely in the ball park the scout/courier is 100 metric tonnes.

It's a displacement (volume), not a mass:

The Hull: Hulls are identified by their mass displacement, expressed in tons. As a rough guide, one ton equals 14 cubic meters (the volume of one ton of liquid hydrogen).

The Scout is 100 displacement tons (≈1400 m³), not 100 tonnes.

If we take a peek at MT, where mass of spacecraft is specified, the Scout is very roughly 1000 tonnes.

On CT LBB 2 1977/1981 page 17 a sand canister weighs 50 kg or 0.05 tonnes.

Jumping back to page 21 Deck plans has the following information: "...The preferred scale for the interior should be 1.5 meters per square, with space between decks put at about 4.0 meters. One ton of ship displacement equals approximately 14 cubic meters. Therefore one ton equals about two squares of deck space...."

Yes, but 3 m deck height, not 4 m.

A CSC autodoc is 500 kg which is 0.5 metric tonnes which appears to mean the autodoc requires approximately 14 cubic meters x 0.5 = 7 cubic meters of 1 interior square of space.

It's not that simple.

1 tonne of steel is about ⅛ m³ or ~0.009 displacement ton.
1 tonne of water is about 1 m³ or ~0.07 displacement ton.
1 tonne of feathers is about 400 m³ or ~28.5 displacement ton.

We can't say how large an object is just from its mass.

[snrdg121408]

Hello AnotherDilbert

Building Ships
1. Custom hull with mass displacements other than the hull sizes shown on the drive potential table are treats as the next larger hull size. The maximum hull possible in these rules is 5,000 tons."

IIRC mass is measured, using the metric system, in grams, kilograms, and metric tons.

If I am remotely in the ball park the scout/courier is 100 metric tonnes.

It's a displacement (volume), not a mass:

The wording used clearly states that the displacement is mass not volume the only mention about volume is when drawing deck plans.

The Hull: Hulls are identified by their mass displacement, expressed in tons. As a rough guide, one ton equals 14 cubic meters (the volume of one ton of liquid hydrogen).

The Scout is 100 displacement tons (≈1400 m³), not 100 tonnes.

If we take a peek at MT, where mass of spacecraft is specified, the Scout is very roughly 1000 tonnes.

Unfortunately MT has changed the design sequence that makes the CT hulls different from the same hulls rebuilt with MT. Technically they are not the same system

CT LBB 2 is not technically the same design system as CT LBB 5 and the attempt to allow the use of CT LBB 2 drives and power plants really are not the same.

On CT LBB 2 1977/1981 page 17 a sand canister weighs 50 kg or 0.05 tonnes.

Jumping back to page 21 Deck plans has the following information: "...The preferred scale for the interior should be 1.5 meters per square, with space between decks put at about 4.0 meters. One ton of ship displacement equals approximately 14 cubic meters. Therefore one ton equals about two squares of deck space...."

Yes, but 3 m deck height, not 4 m.

Oops, looks like my fat fingers hit the 4 and my mind was sure I had typed a 3.

A CSC autodoc is 500 kg which is 0.5 metric tonnes which appears to mean the autodoc requires approximately 14 cubic meters x 0.5 = 7 cubic meters of 1 interior square of space.

It's not that simple.

1 tonne of steel is about ⅛ m³ or ~0.009 displacement ton.
1 tonne of water is about 1 m³ or ~0.07 displacement ton.
1 tonne of feathers is about 400 m³ or ~28.5 displacement ton.

We can't say how large an object is just from its mass.

The entire design system for CT LBB 2/LBB5 and others based on CT have made things simple to make designing quick and easy. MT added some complexity to the design system but skips a lot which increased the time needed to build. CT Striker, TNE, and T4 added more realism but at the same time simplified somethings to make it a more detailed system though still not accurate.

[AnotherDilbert]

The wording used clearly states that the displacement is mass not volume the only mention about volume is when drawing deck plans.

Mass displacement (https://en.wikipedia.org/wiki/Displacement_(fluid)) is the volume displaced by a ship of the specified mass floating is a specified fluid, see Archimedes' Principle (https://en.wikipedia.org/wiki/Archimedes%27_principle). For wet ships the fluid is water, for Traveller spacecraft the fluid is liquid hydrogen.


A Traveller displacement ton is a volume, the volume of a tonne of liquid hydrogen, hence about 14 m³.

[snrdg121408]

Hello again AnotherDilbert,

The wording used clearly states that the displacement is mass not volume the only mention about volume is when drawing deck plans.

Mass displacement (https://en.wikipedia.org/wiki/Displacement_(fluid)) is the volume displaced by a ship of the specified mass floating is a specified fluid, see Archimedes' Principle (https://en.wikipedia.org/wiki/Archimedes%27_principle). For wet ships the fluid is water, for Traveller spacecraft the fluid is liquid hydrogen.

A Traveller displacement ton is a volume, the volume of a tonne of liquid hydrogen, hence about 14 m³.

Mass displacement definition is the displacing in space of one mass by another. The weight or the volume of fluid displaced by a floating or submerged body. Archimedes' principle. https://www.dictionary.com/browse/displacement

Volume displacement is the displacement of a fluid expressed in terms of volume as distinguished from displacement expressed in terms of mass. https://www.merriam-webster.com/diction ... splacement

Mass displacement is not the same as volume displacement as far as I can tell.

About 14 cubic meters or 1 ton of volume displacement requires a mass/weight of 1,000 kg/Mg or 1 tonne of L-Hyd.

[Condottiere]

I don't think the hydrogen is under pressure.

[Old School]

I don't think the hydrogen is under pressure.

Liquid hydrogen is either absurdly cold, or its under pressure.

[Sigtrygg]

The trade chapter of LBB2 77/81 edition makes it pretty clear that a ship ton was originally intended to be mass.

[Ursus Maior]

It has been about hydrogen displacement tons for decades now. One ton(ne) of hydrogen at normal atmospheric pressure for a volume of around 14 m³. The idea seemed to be that volume is something that is easier to consistently integrate into the game via deckplans etc. where as weight is pretty much useless for a scifi universe, since who could possibly predict what equipment would weigh at TL12-15?

[AnotherDilbert]

Mass displacement is not the same as volume displacement as far as I can tell.

It is exactly the same thing expressed in two ways. The basic principle is that one tonne of object displaces one tonne of fluid (with a known volume).

Displacement creates a connection between mass and volume, for liquid hydrogen that is 1 tonne displaces about 14 m³.

Mass displacement expresses that in mass: A ship displaces 1 tonne of liquid hydrogen (hence a volume of ~14 m³).

Volume displacement expresses that in volume: A ship displaces 14 m³ (hence a mass of 1 tonne of liquid hydrogen).

Note that the mass of the ship does not enter into those statements, only the mass of the displaced hydrogen.


Only if we actually find our ship trying to float on a sea of liquid hydrogen, do we have to consider the mass of the ship. Obviously the ship will sink...

[AnotherDilbert]

I don't think the hydrogen is under pressure.

Liquid hydrogen is either absurdly cold, or its under pressure.

Quite, hydrogen can only be a liquid under a very narrow range of pressure and temperature, without enough pressure or cold it will gasify, with too much pressure or cold it will solidify.

See the area labeled "liquid phase":

[snrdg121408]

Hello Condottiere and Old School,

Thank you for the information about L-Hyd being either very cold or under pressure. Unfortunately, that is way out of my limited knowledge base.

[snrdg121408]

Hello Sigtrygg,

The trade chapter of LBB2 77/81 edition makes it pretty clear that a ship ton was originally intended to be mass.

That section of LBB 2 is what got this tangent thread going.

[snrdg121408]

Hi Ursus Maior,

It has been about hydrogen displacement tons for decades now. One ton(ne) of hydrogen at normal atmospheric pressure for a volume of around 14 m³. The idea seemed to be that volume is something that is easier to consistently integrate into the game via deckplans etc. where as weight is pretty much useless for a scifi universe, since who could possibly predict what equipment would weigh at TL12-15?

I wrote two letters to GDW with a number of questions one while stationed in 1978/1979 at Pearl Harbor, HI and the other in San Diego, CA after CT LBB 2 1977/1981 came out. One of the questions was about the mass displacement and how it fit with the deck plans. Unfortunately, I never got a reply back to either letter.

Yes, apparently with CT LBB 5 HG the hull displacement became the deck plan scale that 2 squares can hold the volume of about 14 m^3 is 1 ton of displacement. The issue is that CT LBB 2 1977/1981 still discussed "mass displacement" and then indicated that in deck plans 2 squares can accommodate about 14 m^3 and is one ton of volume.

There are a number of items that failed to be updated or clarified with the revisions to CT and then got out of whack even more with the other Traveller versions.

[snrdg121408]

Hi again AnotherDilbert,

Mass displacement is not the same as volume displacement as far as I can tell.

It is exactly the same thing expressed in two ways. The basic principle is that one tonne of object displaces one tonne of fluid (with a known volume).

Displacement creates a connection between mass and volume, for liquid hydrogen that is 1 tonne displaces about 14 m³.

Mass displacement expresses that in mass: A ship displaces 1 tonne of liquid hydrogen (hence a volume of ~14 m³).

Volume displacement expresses that in volume: A ship displaces 14 m³ (hence a mass of 1 tonne of liquid hydrogen).

Note that the mass of the ship does not enter into those statements, only the mass of the displaced hydrogen.


Only if we actually find our ship trying to float on a sea of liquid hydrogen, do we have to consider the mass of the ship. Obviously the ship will sink...

Not according to the definition

Volume displacement is the displacement of a fluid expressed in terms of volume as distinguished from displacement expressed in terms of mass. https://www.merriam-webster.com/diction ... splacement

The volume of about 14 m^3 is determined by using a grid of 1.5 m squares of which two squares. One square is 1.5 x 1.5 by approximately 3 m. Two squares is 1.5 x 3 x approximately 3 m = approximately 13.5 or about 14 m^3.

I lay out 100 squares which equates to about 1,400 m^3 of displaced L-Hyd which is equal to 100 ton volume displacement of L-Hyd. That does say that 1 ton of L-Hyd = 1 tonne = 1,000 kg.