MasterGwydion
Emperor Mongoose
Valid question.
Mating Airlocks to Cargo Hatches
- Thread starter Terry Mixon
- Start date
Condottiere
Emperor Mongoose
Ammunition and weapons used to have great bulk discounts.
Don't know how valid that is nowadays, or if it applies to other goods.
Don't know how valid that is nowadays, or if it applies to other goods.
Fluffy Bunny Feet
Cosmic Mongoose
The air raft is another one that is wacky. It has a 5 dton docking space for its "4 dtons". Generously calling it 2mx2m*3m = 12 cubic meters. Not even 1 dton. Seems that even in classic traveller that 4 metric tons was excessive. Seems to be about 1 metric ton.
Condottiere
Emperor Mongoose
Current Vehicle rules translate space for volume.
Halved, if over a certain amount.
Halved, if over a certain amount.
Fluffy Bunny Feet
Cosmic Mongoose
I don't have most of the updates but the older stuff that I have access to for the raft has it around 1 metric ton and less than that as cargo.
Condottiere
Emperor Mongoose
There would be a difference between the air/raft crated in cargo, and being readily accessible as an auxiliary craft.
Sigtrygg
Emperor Mongoose
Well here are the quotes:
"Air/Raft (8) Cr600,000, 4 tons. A light anti-gravity vehicle which uses null grav modules to counteract gravity for lift and propulsion. An air/raft can cruise at 100 kph (but is extremely subject to wind effects), with some capability of higher speed to about 120 kph. An air/raft can reach orbit in several hours (number of hours equal to planetary size digit in the UPP); passengers must wear vacc suits and interplanetary travel in an air/raft is nos possible. Range in time or distance on a world is effectively unlimited, requiring refueling from a ship's power plant every ten weeks or so. An air/raft can carry four persons plus four tons of cargo. The air/raft is unpressurised and usually open-topped."
"Air/Raft (8) CR 6,000,000. Also known as a flier, the air/raft relies on solid state null gravity modules for lift and propulsion. Four independent, individually replaceable modules (CR 1,000,000 each) insure a maximum of safety. Loss of one module reduces lift by one-quarter. The standard air/raft weighs 4 tons and can carry a payload of up to 4 tons including pilot and passengers. Cruise speed is 100 km per hour with unlimited range and endurance. Normally, air/rafts are open topped; the referee may allow a pressurized version or such options as gun mounts, searchlights, crash cushions or larger capacities at higher prices."
Note that tons is 1000kg not displacement tons.
"Air/Raft (8) Cr600,000, 4 tons. A light anti-gravity vehicle which uses null grav modules to counteract gravity for lift and propulsion. An air/raft can cruise at 100 kph (but is extremely subject to wind effects), with some capability of higher speed to about 120 kph. An air/raft can reach orbit in several hours (number of hours equal to planetary size digit in the UPP); passengers must wear vacc suits and interplanetary travel in an air/raft is nos possible. Range in time or distance on a world is effectively unlimited, requiring refueling from a ship's power plant every ten weeks or so. An air/raft can carry four persons plus four tons of cargo. The air/raft is unpressurised and usually open-topped."
"Air/Raft (8) CR 6,000,000. Also known as a flier, the air/raft relies on solid state null gravity modules for lift and propulsion. Four independent, individually replaceable modules (CR 1,000,000 each) insure a maximum of safety. Loss of one module reduces lift by one-quarter. The standard air/raft weighs 4 tons and can carry a payload of up to 4 tons including pilot and passengers. Cruise speed is 100 km per hour with unlimited range and endurance. Normally, air/rafts are open topped; the referee may allow a pressurized version or such options as gun mounts, searchlights, crash cushions or larger capacities at higher prices."
Note that tons is 1000kg not displacement tons.
The trouble with comparing CT, especially 1977 LBB CT, is that it was prior to the whole "displacement ton" thing. LBBs just refer to "tons" and there is no place in them that suggests a ton is not 1000kg.
THEN, not too far down the track (1979? 1981?), a decision was made to swap to volume, basing a displacement ton of 1000kg of liquid hydrogen.
And we have been confused ever since, despite heroic attempts in MegaTraveller and TNE to replace dTons with cubic metres.
In reality both cubage (length, width, height... slightly different to volume, since a given volume's dimensions can vary, and cargo holds care about that) and mass are important. Although often one of them is less important than the other. If you pack a moving van to the brim, it doesn't matter as much as to what the mass is, within limits. If you reach an aircraft's maxiumum takeoff weight, it doesn't matter much how much space is left in the hold.
As a kludge, we seem to have ended up where mass in tonnes of a ship's vehicle happens to be the volume in dTons of its vehicle bay.
THEN, not too far down the track (1979? 1981?), a decision was made to swap to volume, basing a displacement ton of 1000kg of liquid hydrogen.
And we have been confused ever since, despite heroic attempts in MegaTraveller and TNE to replace dTons with cubic metres.
In reality both cubage (length, width, height... slightly different to volume, since a given volume's dimensions can vary, and cargo holds care about that) and mass are important. Although often one of them is less important than the other. If you pack a moving van to the brim, it doesn't matter as much as to what the mass is, within limits. If you reach an aircraft's maxiumum takeoff weight, it doesn't matter much how much space is left in the hold.
As a kludge, we seem to have ended up where mass in tonnes of a ship's vehicle happens to be the volume in dTons of its vehicle bay.
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Fluffy Bunny Feet
Cosmic Mongoose
Source? I haven't seen this air/raft before. The one I see is .25 tons cargo and much cheaper. Also the two versions you list have a 10 fold price difference between them. Any info on its physical dimensions or dTons?
For what it's worth, here are the relevant 1977 and 1981 ship tonnage definitions from LBB Book2:
1977 (p10) "Hulls are identified by their mass displacement, expressed in tons."
1981 (p13) "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)."
It should be noted that even in the 1981 text, it is still primarily talking about mass, and is not saying any component other than fuel has to be 14 cubic metres. You would, in fact expect accommodations and access areas to take up more volume than their mass, but engines and other particularly dense components to take up less. For what it's worth, the volume of one ton of water is 1 cubic metre.
I think this is a point that got lost later on, or was compounded by some of the choices made in MegaTraveller.
"Mass displacement" is a bit of a weird term, too. Shipping displacement is based on weight of water displaced, not ship mass. Google "Mass Displacement" and you get a lot of stuff about refugees and landslides.
Volume of a spaceship generally has little meaning in space (it does effect aerodynamics, so is important in atmospheres), so it makes total sense that ships are designed in terms of the mass of their units, and you work out their dimensions afterthat.
1977 (p10) "Hulls are identified by their mass displacement, expressed in tons."
1981 (p13) "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)."
It should be noted that even in the 1981 text, it is still primarily talking about mass, and is not saying any component other than fuel has to be 14 cubic metres. You would, in fact expect accommodations and access areas to take up more volume than their mass, but engines and other particularly dense components to take up less. For what it's worth, the volume of one ton of water is 1 cubic metre.
I think this is a point that got lost later on, or was compounded by some of the choices made in MegaTraveller.
"Mass displacement" is a bit of a weird term, too. Shipping displacement is based on weight of water displaced, not ship mass. Google "Mass Displacement" and you get a lot of stuff about refugees and landslides.
Volume of a spaceship generally has little meaning in space (it does effect aerodynamics, so is important in atmospheres), so it makes total sense that ships are designed in terms of the mass of their units, and you work out their dimensions afterthat.
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Fluffy Bunny Feet
Cosmic Mongoose
Thanks, never thought to look there. Seems like the 600,000 Cr price is the later one and should be used. Much better than the little one I've been finding and lots more cargo for a bit more than double the price. Still should fall in the 1dTon category though, 2 at the most if it has an enclosed cargo/passenger area. So the 5 ton docking space is excessive unless carrying multiple units or an even bigger one.
Well... the docking area would need space to store spares and other related garage equipment and access space.
As well, the cabin and cargo spaces of the Air/Raft don't contribute to the 4 tons - those are payload additions. And... height is going to be well under the nominal deck height of 3m, or even the assumed 2.5m. So it will take up more squares than it's nominal volume might suggest.
As a four ton vehicle with a four ton carrying capacity, it's going to be roughly the size of a small truck. Using an Isuzu N series as a very rough example, 2m width and 4-5m length seems reasonable... meaning the standard depiction of it fitting into a 2x3 deckplan (3m x 4.5m) works out. That's three displacement tons in deckplan terms right there - another dTon for space to actually get in or out of it, and a ton for the hatch.
This gets back to the distinctions between mass, dimensions and volume needed to store a physical object. Standing people are taller than cars, so garage ceiling heights aren't set at vehicle height plus 10%, unless the vehicle in question is quite tall. Most often the ceiling height is dictated by other factors, that apply to living areas.
As it happens (probably by a complete fluke), there is a rough equivalence between metric tonnage of Traveller vehicles and the dTons needed to garage them.
As well, the cabin and cargo spaces of the Air/Raft don't contribute to the 4 tons - those are payload additions. And... height is going to be well under the nominal deck height of 3m, or even the assumed 2.5m. So it will take up more squares than it's nominal volume might suggest.
As a four ton vehicle with a four ton carrying capacity, it's going to be roughly the size of a small truck. Using an Isuzu N series as a very rough example, 2m width and 4-5m length seems reasonable... meaning the standard depiction of it fitting into a 2x3 deckplan (3m x 4.5m) works out. That's three displacement tons in deckplan terms right there - another dTon for space to actually get in or out of it, and a ton for the hatch.
This gets back to the distinctions between mass, dimensions and volume needed to store a physical object. Standing people are taller than cars, so garage ceiling heights aren't set at vehicle height plus 10%, unless the vehicle in question is quite tall. Most often the ceiling height is dictated by other factors, that apply to living areas.
As it happens (probably by a complete fluke), there is a rough equivalence between metric tonnage of Traveller vehicles and the dTons needed to garage them.
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Condottiere
Emperor Mongoose
I did some calculations after second edition, and decided you get more bang for your buck by replacing the air/raft at four tonnes, with a five tonne smallcraft, which needs a five and half tonne bay.
Since I design mostly Confederation spacecraft, there's very little discrepancy involved.
That would be a self motivated forty foot container.
Since I design mostly Confederation spacecraft, there's very little discrepancy involved.
That would be a self motivated forty foot container.
Fluffy Bunny Feet
Cosmic Mongoose
2x5x3 is 30 cubic meters or 2 dTons, add the mandatory extra ton minimum and you are at 3 tons. 3 tons for the docking space is much more reasonable than the 5 they are using. With the 5 there is no reason you couldn't have 2 of them aboard which also lets you carry your entire crew and cargo with the larger design you pointed out to me. The smaller design was more car like than truck.
Sigtrygg
Emperor Mongoose
Exactly the same trade section was found in 77, 81, TTB, ST. It was retained all the way to MT, when the trade system changed.
There is a very easy fix, track mass as a variable, which is something they did from Star Cruiser moving forward.
Configuration is needed so that surface area can become a factor too...
So you rate the maneuver drive for mass it can move and the jump drive for volume it can jump.
And it makes no sense.
In MT an air/raft displaces 2 displacement tons yet has a loaded mass of ~1,600 empty and 7,200kg loaded.
Sigtrygg
Emperor Mongoose
CT 81 and CT77. They both require 4 tons of vehicle space on a ship.
Condottiere
Emperor Mongoose
If you go by illustrations, and what raft implies, an enlarged dinghy.
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