Mating Airlocks to Cargo Hatches

[swordtart]

If each square is 1.5m, 6 of them makes the horizontal cross section only 6.75m. Even allowing for a 3m deck height that should be less than 2 DTons. You need a heck of a lot of packaging to bring that up to 4 DTons and having to have a 5 DTon docking space is excessive.

As the MGT2 air raft is an 8 space design (both from it's shipping volume and its components). It must be larger than it looks. A passenger takes up a space and this is considered 1/2 DTon for shipping purposes. There no way a passenger seat takes up 7 cubic metres. 2-3 cubic metres would be more reasonable.

So either shipping volume adds a mahoosive margin for... well I am not sure what exactly, but stacking that with a 1DTon minimum for access in a docking space seems far too much.
or the picture of the aircar should be more like a g-carrier.

As for a g-bike taking up 21 cubic metres...

S'madness I tell ye.

 

[Condottiere]

There's a difference between crated, and deployed.

We'll assume that shipping volume is a deployed vehicle, that can be accessed and maintained.

As for our five foot munchkins, they're in a cautious, semi crouched, pose.

 

[Terry Mixon]

If each square is 1.5m, 6 of them makes the horizontal cross section only 6.75m. Even allowing for a 3m deck height that should be less than 2 DTons. You need a heck of a lot of packaging to bring that up to 4 DTons and having to have a 5 DTon docking space is excessive.

As the MGT2 air raft is an 8 space design (both from it's shipping volume and its components). It must be larger than it looks. A passenger takes up a space and this is considered 1/2 DTon for shipping purposes. There no way a passenger seat takes up 7 cubic metres. 2-3 cubic metres would be more reasonable.

So either shipping volume adds a mahoosive margin for... well I am not sure what exactly, but stacking that with a 1DTon minimum for access in a docking space seems far too much.
or the picture of the aircar should be more like a g-carrier.

As for a g-bike taking up 21 cubic metres...

S'madness I tell ye.

I thought it was 4 spaces per dton. At least I think so.

 

[swordtart]

I thought it was 4 spaces per dton. At least I think so.

Vehicle Handbook p16
LIGHT GRAV VEHICLE
Once grav technology becomes cheap and widely available, most worlds make a rapid transition from ground to grav vehicles. In just about every measurable way, grav vehicles are better, being faster, smoother and safer.
Tech Level: 8
Skill: Flyer (grav)
Agility: +1
Spaces: 1-20
Cost per Space: Cr30000
Hull: 2 per Space
Shipping: 0.5 tons per Space
Traits: None
Examples: Air/raft, g/bike, grav car

From the Robot Handbook p14 we have "A spacecraft ton – approximately 14 cubic metres – is the equivalent of four Spaces or 256 Slots."

So a shipping space already includes an extra 100%* for... bubble wrap? An 8 space air raft in a docking bay ready to fly should take up 2 DTons plus 10%. Even with ridiculous rounding up it is still only 3 DTons including access. 4 DTons is enough space to maintain it on board (hangar space is double size of vehicle).

* 1/2 DTon/space is common but some vehicle types are different. Weirdly the unpowered boat (including a galleon)only takes up 1/4 DTon per space. Maybe all that practice with ships in bottles means crew can pack them in much tighter? Airships are 0.1 (presumably uninflated) but most conventional aircraft are more. Not much rhyme or reason to it really.

 

[Condottiere]

It scales.

And halves, at over sixty tonnes, I think.

 

[Terry Mixon]

Vehicle Handbook p16
LIGHT GRAV VEHICLE
Once grav technology becomes cheap and widely available, most worlds make a rapid transition from ground to grav vehicles. In just about every measurable way, grav vehicles are better, being faster, smoother and safer.
Tech Level: 8
Skill: Flyer (grav)
Agility: +1
Spaces: 1-20
Cost per Space: Cr30000
Hull: 2 per Space
Shipping: 0.5 tons per Space
Traits: None
Examples: Air/raft, g/bike, grav car

From the Robot Handbook p14 we have "A spacecraft ton – approximately 14 cubic metres – is the equivalent of four Spaces or 256 Slots."

So a shipping space already includes an extra 100%* for... bubble wrap? An 8 space air raft in a docking bay ready to fly should take up 2 DTons plus 10%. Even with ridiculous rounding up it is still only 3 DTons including access. 4 DTons is enough space to maintain it on board (hangar space is double size of vehicle).

* 1/2 DTon/space is common but some vehicle types are different. Weirdly the unpowered boat (including a galleon)only takes up 1/4 DTon per space. Maybe all that practice with ships in bottles means crew can pack them in much tighter? Airships are 0.1 (presumably uninflated) but most conventional aircraft are more. Not much rhyme or reason to it really.

Ah. Well, I suppose we’ll see what happens in the new update. Maybe it’ll get clearer.

 

[swordtart]

We could do without the casual conflation of volume tonnage and actual mass tonnage. An air raft that masses 4 Tons seems plausible, it is in the same order as a car. As pointed out however its foot print should also be the same order as a car.

Those who want to stick to CT will doubtless be unhappy, but they should have been unhappy as soon as someone came up with the idea that an air raft was 4 DTons.

 

[Terry Mixon]

We could do without the casual conflation of volume tonnage and actual mass tonnage. An air raft that masses 4 Tons seems plausible, it is in the same order as a car. As pointed out however its foot print should also be the same order as a car.

Those who want to stick to CT will doubtless be unhappy, but they should have been unhappy as soon as someone came up with the idea that an air raft was 4 DTons.

This is Mongoose Traveler. They are hopelessly conflated and it will likely only become more so as things progress.

 

[rinku]

It's actually NOT saying an Air/Raft itself is 4 dTons. It says that its shipping volume is 4 dTons. Shipping Volume is pretty much only used for working out vehicle bay sizes, and occasionally how many actual items there are in a cargo lot.

I think Mongoose have threaded this old needle quite neatly. It's pretty easy to see that the 4000kg Air/Raft occupies 6 floor spaces and is too tall to stack two of them in a normal 2.5m deck clearance room. Just to physically accommodate them on a deckplan, you need 3 dTons, but that makes no allowance for access or maintenance. 1 ton for that and 10% rounded up for exterior access seems fair.

 

[Fluffy Bunny Feet]

It's actually NOT saying an Air/Raft itself is 4 dTons. It says that its shipping volume is 4 dTons.

Is that the one worth 600,000 Cr? The one used by the Scout/Courier and Marava class Trader is only 250,000 Cr and seems to be more of a ~1,000 kg unit (which is listed for shipping as 4 tons NOT dTons). If it is the larger unit it is more acceptable (and more useful to a trader/scout).

 

[rinku]

All the products just use "tons" in the various listings. Certainly the most up to date versions of MGT2e22 Core and HG, which are the relevant products with the table discrepancy do.

HG defines "displacement tons" on p.5 and never uses that term at any point later - it's a given that every reference to "tons" in HG is referring to "d-tons". Core has the same definition on p.149.

I would note that the cargo value number of the MGT2e vehicles is much reduced from the CT ones. CT Air/Raft can carry 4 tons, which is generally taken as 4000kg; the MGT2e one has cargo of 0.25 ton - clearly that is talking about displacement tons (in this case a cargo space of about 3.5m3). I'd also note that CRB vehicles are not given actual dimensions or masses, just the Shipping value, whose definition is "How much space the vehicle will require for transport in a spacecraft".

To be honest, it's probably easier to avoid using "tons" for any mass measurement in Traveller. Megagrams (1000s of kgs) are the same thing.

In these kinds of discussions I try to use dTons or d-tons when referring to those, to avoid confusion with metric tons/tonnes/10^6 grams/Mg.

Or, for that matter, measures that are 2,240 lbs, 2,000 lbs or 100 cubic feet. Classic Traveller does not actually define a ton; equipment mass has always been measured in kilograms... but in the 1977 books planets are measured in 1000's of miles and the space combat scale was one inch = 1000 miles (changed to 1mm = 100km in the 1981 Book 2).

 

[Fluffy Bunny Feet]

I would note that the cargo value number of the MGT2e vehicles is much reduced from the CT ones. CT Air/Raft can carry 4 tons, which is generally taken as 4000kg; the MGT2e one has cargo of 0.25 ton -

Have you looked at the associated picture of the MGT2e air raft? There is NO WAY for it to carry 4 tons. It doesn't look able to carry the .25 tons without dumping passengers let alone several cubic meters for a .25 dTon. It also is listed at around 250,000 Cr while the cited CT version that carries 4 tons is either 600,000 Cr or 6 million Cr depending on the source.

 

[rinku]

The CT vehicle is different in other ways - for a start it's a 4 seater - so they're not the same model. Which is fine. Air/Rafts come in lots of versions. and it's pretty clear that the payload of a CT air/raft is 4 people plus 4000kg of cargo, not 54 cubic metres.

Um, and I assumed the cargo area was in the front, like a rear engined car usually has. That looks like it can enclose 3.5m3. Call it 2m wide, 1m high, 1.75m long.

I'm not sure what relevance price changes have to this discussion. Lots of prices change between editions.

 

[Fluffy Bunny Feet]

The CT vehicle is different in other ways - for a start it's a 4 seater - so they're not the same model. Which is fine. Air/Rafts come in lots of versions. and it's pretty clear that the payload of a CT air/raft is 4 people plus 4000kg of cargo, not 54 cubic metres.

The price does matter as the price on these ships closely matches the smaller low cargo capacity air raft making the docking space tonnage really ridiculous especially since even 1 ton of docking space is as expensive as the air raft and making it use 5 tons means your docking space is 5 times as expensive as the craft itself while also being way too big. You ought to be able to carry 4 of the little ones or 2 of the big ones in that space (or 2 small and 1 large).

If the CT air/raft is kg (most likely) it is operating on the same scale as the ships of the time as dTons came later. But it makes the docking space using dTons worse for it. But also if it IS kg then so should the packing weight of the air raft be and that is being used as dTons for calculating the docking space (though why packing would be included for an operating vessel that isn't IN the package I don't know).

Um, and I assumed the cargo area was in the front, like a rear engined car usually has. That looks like it can enclose 3.5m3. Call it 2m wide, 1m high, 1.75m long.

Like a classic VW Beetle? I assumed that was more like engine, power and fuel. Could be a forward trunk.

 

[rinku]

Does this help?


Even pretty well packed, you end up with a fair bit of wastage. And that's just in a shipping container, not a vehicle bay.

One further thought... there are other models of 4 ton Air/Raft that are enclosed and even pressurised. Even if it is possible to stack two of the open topped ones in a 3m x 6m x 3m space, there's probably practical allowance for the taller enclosed ones in most standard Air/Raft bays.

And after all, you don't build the vehicle as part of building the ship. You build a space to put vehicles, with a maximum size. You should be able to park most vehicles of shipping size 4 into that bay, unless their dimensions were especially long, wide or tall.

 

[swordtart]

The DTon volume of 14 cubic metres assumes a 3m decks separation. For staterooms and the like we tend to assume a 2.5m ceiling to accommodate servicing and the like. There is no reason for cargo bays (or fuel tanks) to be so constrained. Those standard containers referred to earlier in the thread have a 3m height, so a 2.5m cargo bay height cannot be standard.

An air raft doesn't have wheels or a drive train and is traditionally depicted as much flatter than a car. Traditionally it doesn't have a roof or much of a windscreen either (and frankly if it flipped over it would be a death trap. My car is just under 1.5m on from the ground to the top. That includes the 6" or so ground clearance. Two that were packed to conform to a space constrained environment (vs a weight constrained environment) could reasonably stack to fit in a 3m space (they wouldn't necessarily drive on).

Before reading Robot Handbook I previously assumed that the 0.25 tons it can accommodate as cargo are actual mass tons as most of it's cargo will be conventional equipment.

The space discrepancy could be resolved by the same logic as with robots. 1 space capacity for vehicle components requires a vehicle 2 spaces "big" to account for the body, actuators etc. This a single passenger vehicle would be 2 spaces "big". Shipping is a convenience as some vehicles need more volume for body (aircraft take a lot of space as the wings stick out etc.).

The only change then required would be to make the illustrations match that and make the components more credible sizes. A person does not need 3.5 cubic metres to sit in an open topped vehicle. If it were enclosed like a conventional car you might need 2 cubic meters per person including the seat, access space and some personal stowage. My car (Ford Focus) is perfectly comfortable for extended journeys (4+ hours without a stop and 13+ hours with 1/2 hour comfort break every 4.5 hours driving). It has a total passenger compartment volume of around 5-6 cubic metres. That can fit 2 normal people in the same comfort as the driver plus 2-3 slightly more cramped people so 2 cubic metres per person would be armchair comfortable.

My whole car is under 14 cubic meters in volume. The ground car in Vehicle Handbook is 3 Tons (and 6 interior spaces). That is a reasonable mass, but as a volume it is ludicrous.

 

[Condottiere]

For the generic air/raft, the only thing that sticks out is the windscreen.

Whether this can removed manually, or electrically lowered, you can stack them.