Starship Construction Manual Error

[tonyg]

I was looking through my newly reacquired Starship Construction Manal, and I noticed a rather significant (as far as the numbers go) math error in the cargo ratings.

According to the book, 1 Standard Cargo nit (SCU) is 6.75 cubic meters. Okay. Also, according to the book 1 SCU is assumed to have a mass of 50 metric tons, which is considered to be about 3/4th the mass of water. Not okay.

Water has a mass of 1 metric ton per cubic meter, so if 1 SCU has the mass euqal to 3/4th that of water it should be around 5 mt, not 50. Either somene muplitpled the number by 10 or was thinking in English (water is around 63 pounds per cubic foot, and 3/4 of that would be around 50 pounds per cubic foot).

So all the cargo tonnages for FASA ships are off by a factor of 10.

[UFC465537]

That's quite a difference. I posted a link to your thread at FasaTrekUniverse @ Yahoo!. It would suck to change stats and masses all over the place!

[tonyg]

Some ships would be unaffected. The big effects would be on ships that drop a Class or two and wind up with better engine performance, or worse, become too small to support their components. For example the MkI Constitution-class drops down to Class X and a 3/1 MPR, making the old Connie more maneuverable than the later version with the more powerful FWF Engines.

I think the best fix would simply to assume that the cargo holds are designed to hold something with around 10 times the specific gravity of water, say Silver, or a Tungsten-steel alloy, or some sort of fictional hull materal like duranium, with sg10. That would allow the cargo hold stuff to be used as is. It would also make a lot of sense since many things that a ship could be carriying as cargo are denser than water (steel lead, gold, uranium, alumininum, transpartent aluminum, latinum, and, probably self-sealing stem bolts and dilithium). Since cargo units measured in volume, changng the mass won't alter the ship's carrying capcity (just make sure to check masses given in Trader Captains). The only reason ship designers uses the mass of water for cargo calculation in the real world is to ensure that the a ship will still float. Starship don't have to worry about boyancy, and so only need to worry that the cargo won't be so massive as to fall through the deck or punch through a bulkhead.

For ships with a great deal of cargo space (fuel carriers, and cargo haulers), some of the difference in mass could be assumed to be for macherery and shielding (things like temerature controls, storage compantments, strucutual bracing, and radiation shielding). It probably takes a lot of equpment to transport anitmatter.


BTW, The only reason why I discovered this was that I've been having difficulties with designing cargo ships in CODA Trek and looked at FASA to see why FASA ships can carry ao much more tons of cargo than in CODA. For example a Constituion-class in FASA can carry 19,000-19,500 mt in FASA, compared to 1750mt in CODA (sing the mass of water for calculations). Upon closer inspection I noticed that FASA was getting a lot more mass per volume than made sense by thier calaculations.

On the plus side CODA ships seem to match up better to FASA ships in the cargo depatment than before.

[spyone]

I, too, was re-reading some old gaming books, and I realized that Traveller used the same standard as FASA (or more properly the other way around, since Traveller predates FASA-Trek): a deckplan is done in square 1.5 meters on a side, each reresenting 6.75 cubic meters of displacement.
Thus, every 2 squares represents 1 Traveller "displacement ton" (since Traveller's tons were based on liquid hydrogen), so 2 Trek SCU = 1 Traveller Ton.

No wonder people keep suggesting using Traveller deckplans for Trek ships.

[tonyg]

Thanks spyone,

Liquid hydrogen has a sg (specific gravity=density) of 0.07g/cc or 70 kg/cubic meter. Two travel cargo squares = 13.5 cubic meters, so two cargo unitts of liquid hydrogen would mass 945kg. Yippie!

Close enough, especially if we take into account some mass for a container to hold the hydrogen, for storage compantments, tie downs and such.