How big is a cargo unit anyway?

TerlObar's picture
TerlObar
February 6, 2011 - 4:11pm
This is something that needs to be addressed.  I'd like to see us define a cargo unit to be a specific size and then ships are designed to carry a certain number of them (and it would be more than 1 per HS).

The problem I see with the current system (and this doesn't just apply to the cargo units) is that the size (i.e. volume) of a ship goes up geometrically with HS while its capacity in terms of weapons, cargo, etc only goes up linearly.  Now I don't expect it to scale exactly the same as larger ships need more infrastructure but the current system doesn't make sense.

for example, the Gullwind is a HS 6 freighter and as such can carry 6 cargo units according to the standard rules.  However, if I build a HS 10 freighter, it has the same number of engines, only requires 4 more crew and according to the standard rules can carry 10 cargo units.  However, based on the standard sizes of the different ships in the Campaign book.  This ship is physically over 7 times larger than the Gullwind.  It should be able to carry about 7 times (700%) more cargo, not just 66% more.  And my HS 20 super freighter (which could put 3-5 gullwinds inside it's cargo bays) is ove 115 times its size and should be that much more cargo as well.

Let's use this tread to thrash out what a cargo unit should be.  We can work out the details of how that is dealt with in the construction rules elsewere.  As an different side project we could also work out how many cargo units various pieces of cargo take up (say a Class A atomic engine require 4 cargo units to transport).

My vote is to define it as something like a 5m x 5m x 6m (150 m3 ) volume.  It doesn't have to be exactly that shape but that is the basic size.  That means you might be able to shoehorn two cargo units into a HS 2 shuttle (you'd probably get only one) but there would be no HS 1 cargo shuttles.  (A HS 1 ship is only  ~31 m3 in total size.  In theory, if designed properly you could probably package a HS 1 ship into a single cargo unit.)

What are your thoughts?
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Comments:

iggy's picture
iggy
February 7, 2011 - 8:41am
I like this and I think that the standard unit should be an integer number of cargo units for a hull size one ship.  maybe even one unit for a hull size one.  I also think the standard mass should be a cargo unit filled with water.
-iggy

TerlObar's picture
TerlObar
February 7, 2011 - 10:02am
I don't think using a HS 1 ship will work as the minimum unless we redefine what volume constitues a HS 1 ship. Based on the average size given in the KH rules for a HS 1 ship, the total volume of that ship is 31.4 cubic meters or about 1110 cubic feet.  That is smaller than my office here in my house and translates to a space that is 10'x14'x8'.  And that is to hold the entire ship, not just the cargo space.  Even if you stretch the dimensions by 25% in each direction, you only get just under twice as much space. or about 2170 cu feet.

For comparison, at typical 48' tractor trailer is 8.5'x13'x48' = 5404 cu. feet = 150 cu m.  (I didn't know that when I first propsed 150 cu. m for a cargo unit, just computed it for the first time, cool.).  Anyway, I was thinking that would be something more reasonable as a shipping cargo unit.  You could fit one or two of those into a HS 2 shuttle (maybe even three if it is just a cockpit, cargobay and engines).  In a HS 3 shuttle you could put quite a few (probably close to a dozen).

Here is a quick table:


HS
Total Ship vol.
(ave. sizes from
KH manual)
Ratio to
150 cu. m
cargo unit
Estimated #
of 150 cu m.
cargo units
 1 31.5 0.20.1
 2 589 3.92
 3 2513 16.712

HS 1 ships are just small. Smile

As for the mass to volume, I'm all for using water as the standard, athough that might be a little light (I imagine most cargo units wouldn't float Wink).  Using water, 1 cu m. = 1 (metric) ton and that is good easy math.
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jedion357's picture
jedion357
February 7, 2011 - 5:20pm
I'm for "good easy Math" as tom puts it.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

iggy's picture
iggy
February 8, 2011 - 9:58am
I didn't bother to look up what a hull size 1 actually is.  But you are going how I am thinking, simple small cargo size that is familiar.  150 cu m matching a tractor trailer is cool and it turn out to be 150 metric tons of water.  Now for choosing water I did that because it is a valuable resource for a space going race and it's math is easy.  I couldn't think of anything that converts from volume to mass as easy that had more mass per volume.  But I would like it denser.

BTW, posting from Tiawan.  Foot in mouth
-iggy

TerlObar's picture
TerlObar
October 24, 2011 - 10:57am
The more I think about it, the more I think we should just use one ton per cubic meter as the average volume to mass conversion.

I just grabbed a bunch of random boxes (complete KH rule box, my new monitor's shipping box, boxes of instant oatmeal from Sam's club, bag of sugar, etc.) and measured their mass and volume  The sugar came out to just over a ton per kg but the others were all less.  I suspect that will be the case all around.  Bulk materials will come out to above that average, especially raw material resources.  Processed and technology items, that require packaging to ship, will be lighter since there will be a bunch of empty space around them for "cushioning".

So I think I'm going to propose that for ship construction, we use 1 ton per cubic meter when determining thrust, ADF, max cargo mass capacity, etc.  For the actual cargos, we just assume that is the mass to volume ratio (the extra weight for lighter cargs could easily be explained as being made up by shipping containers, etc.) unless we know for sure that it will be more.  I.e. gold has a mass of about 19.3 tons per cubic meter.  So we either say at a CU of gold masses 3000 tons instead of 150 or that a CU of gold still weighs only 150 tons but takes up only 7.5 cubic meters.  I think I'm more in favor of the latter.  You'll be carrying your rated mass but will have a lot of empty space in the hold.
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Shadow Shack's picture
Shadow Shack
October 25, 2011 - 8:43pm
Well, p.47 of the KH book lists ore/unit in tons for raw materials (mining). That might be a place to start. Although it's all over the map ranging from 500T mercury per unit to 25K tons/unit for gems. Titanium, one of the more dense materials listed, comes in at 8K so it's really not very accurate --- the old saw of which is heavier (rather which takes up more space per ton), a ton of feathers or a ton of lead just doesn't apply here either.


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