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Author Topic: Warship cargo capacity  (Read 2438 times)

idea weenie

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Re: Warship cargo capacity
« Reply #30 on: 10 September 2022, 22:55:13 »
They never gave good numbers in btech but I always followed the ww2 10% rule.  10% in fuel and 10% in cargo let you range out on your own and effect repairs without needed a resupply.  The Bismarck fits the example.  Enough to maraud about but not enough to avoid capture by sailing around the world with no resupply.

From there I like half and double measures.  So 5% fuel and or cargo would be "low endurance" compared to the 10% standard, while 20% each would be "high endurance".  In this way a 10% fuel ship could run down a 5% ship and then have enough for the trip back while a 20% ship could do the same to a 10% fuel ship.  Since running battles where one side hits empty first and thus loses are both cool and in the fluff I tend to follow that design.

For cargo its a bit harder to put a number on it as how many tons of supplies a ground force uses in hostile territory is ill defined.  But we know it takes lots and lots of tons to support a planetary invasion so I like 20%+ on the sldf ships.

When you say 10%, do you mean gross tonnage or net tonnage?

I.e. a 1 Megaton ship has a jump core massing 452,500 tons, meaning its net mass is 547,500 tons.
Is the 10% that of the gross tonnage and equal to 100,000 tons?
Or is it 10% of the net tonnage, aka 54,750 tons?

Daryk

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Re: Warship cargo capacity
« Reply #31 on: 11 September 2022, 05:54:40 »
It sounds like gross tonnage to me, but only DevianID can say for sure.

BATTLEMASTER

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Re: Warship cargo capacity
« Reply #32 on: 11 September 2022, 08:50:21 »
I think it's gross tonnage.
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DevianID

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Re: Warship cargo capacity
« Reply #33 on: 11 September 2022, 22:30:12 »
Yeah gross.  So a 1 million ton ship is 100k cargo 100k fuel.  Its a lot by btech standards, but honestly 10% fuel for a space vessel is a super tiny fraction by most other universes.

For comparison the ~2 million ton mckenna has 13% cargo allotted and .085% (.00085 ship mass) in fuel.  So the cargo is decent but the fuel is a literal joke.  Id rather not track fuel at all then pretend that less than 1/1000th of your weight for space travel keeps your tanks topped off for over a month of burn time on a 2 million ton ship.

Daryk

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Re: Warship cargo capacity
« Reply #34 on: 12 September 2022, 03:10:34 »
Thanks for the confirmation!  :thumbsup:

BattleTech's ridiculous fuel fractions are all down to "strategic mode" magic.

Knightmare

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Re: Warship cargo capacity
« Reply #35 on: 12 September 2022, 14:48:59 »
...and also because you can carry fuel as cargo.

It's laborsome to transfer, but the small fuel bunker of SLN ships isn't so troublesome if some of their cargo is dedicated to extra fuel for the furnace.  ;)
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BATTLEMASTER

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Re: Warship cargo capacity
« Reply #36 on: 12 September 2022, 18:37:39 »
...and also because you can carry fuel as cargo.

It's laborsome to transfer, but the small fuel bunker of SLN ships isn't so troublesome if some of their cargo is dedicated to extra fuel for the furnace.  ;)

I like to think that there are fuel transfer lines built into the cargo holds to accommodate extra fuel stores.
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Daryk

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Re: Warship cargo capacity
« Reply #37 on: 12 September 2022, 18:39:42 »
You still have to pay for liquid cargo...  8)

Hellraiser

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Re: Warship cargo capacity
« Reply #38 on: 13 September 2022, 17:13:38 »
13.315% Space isn't bad on a ship THAT big.  257KT Combined.

On a Fox that % might seem small but a McKenna has a hefty cargo hold.

Fuel as Cargo does eat up some extra space for pumps IIRC from the old AT2 Construction rules.  Assuming that rule carried over but its not a huge %.
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idea weenie

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Re: Warship cargo capacity
« Reply #39 on: 13 September 2022, 18:58:45 »
13.315% Space isn't bad on a ship THAT big.  257KT Combined.

On a Fox that % might seem small but a McKenna has a hefty cargo hold.

Fuel as Cargo does eat up some extra space for pumps IIRC from the old AT2 Construction rules.  Assuming that rule carried over but its not a huge %.

From Tech Manual p239, the 'Transport Bay' table, "Cargo, Insulated or Refrigerated" has a capacity of .87 times the allocated tonnage.  So if you have a 10,000 ton cargo bay, you can carry 8700 tons of H2 fuel.  Reversing, if you want to carry 10,000 tons of H2 fuel, you will need 11,495 tons of capacity.  Since the bay is empty afterwards, all I can think of is that these are standardized shipping container, specifically tanktainers.

Compare that to designing the extra fuel into the Warship/Dropship/Jumpship, where 10,000 tons of H2 fuel only needs an extra 200 tons of pumps (Strategic Operations -> Advanced Aerospace Unit Design -> Step 2: Install Engines and Control Systems -> Determine Fuel Capacity).  So if you expect the ship to need a larger H2 fuel tankage, you are better off allocating massive tanks of fuel as part of the design instead of using cargo bays to store the fuel.  You lose the flexibility, but you are only using 2% of the fuel mass instead of ~15% of the fuel mass.

The fun part is that H2 fuel for a Warship/Dropship/Jumpship only needs 2% extra mass, while carrying liquid cargo (from the Transport Bay table) only gives you 91% efficiency.  Perhaps this is due to being customized for a specific fluid type?  But that is where getting into fan rules would start applying.

Warship

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Re: Warship cargo capacity
« Reply #40 on: 29 September 2022, 12:36:51 »
Seeing a lot I agree with, here.  I always thought those large cargo bays must have held lots of fuel (and parts, weapons, food, etcetera) in separate tanks.  The extra fuel would give the BB or CA the ability to refuel not just fighters and dropships, but also their escorts.  With as many heavy ships the SLDF fielded, it seems to make sense.  The SLDF would not just have a single McKenna as the only ship in the quadrant, like in another series.  Instead, from the way I read things, there would be several BB's, CA's, and escorts.  Those escorts would probably be dependent upon go-go juice between ports-of-call.

Daryk

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Re: Warship cargo capacity
« Reply #41 on: 29 September 2022, 18:26:42 »
Capital ships being the ultimate source of fuel in forward deployed forces has a LONG history...  ^-^

DevianID

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Re: Warship cargo capacity
« Reply #42 on: 30 October 2022, 03:07:15 »
The only number that sticks out to me from the past is 10% fuel and 10% stores.  I did check out "Conway fighting ships 1922-1947" at the library to make sure I wasn't crazy as they have several mentions of ships with their fuel tonnage listed.  They are all close to 12% or so fuel, though the ships could vary their mass by quite a bit on heavy loads which pushes that ratio closer to the 10% I picked up from somewhere.  So not crazy there.  And they did have lower endurance ships/costal ships with less fuel and tankers with higher endurance.
« Last Edit: 30 October 2022, 03:10:34 by DevianID »

Knightmare

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Re: Warship cargo capacity
« Reply #43 on: 01 November 2022, 11:07:09 »
If you consider the abundance of refueling stations in addition to the ability to carry fuel stores, the smaller fuel bunkers aren't such a big deal. The SLN was predominately a peace-keeping force, so every port of call could conceivably serve as a refueling station. 

That said, even during the SL Civil War, the SLDF only needed one or two friendly realms to ensure their ships weren't stocked to the brim with fuel, say, over other war material before Chieftain kicked off.

Once in Amaris-controlled territory, fuel stops wouldn't be as readily available, but the supply chain head still began at the Hegemony's border vs. the former Rim Republic. Plus, there were places like Freedom Station and Luyten that served as secure refueling locations in Hegemony territory, and it only takes a couple of fuel-stocked Mammoths to serve the needs of a good-sized task force for a fair bit without tapping into any captured stores.
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