Ship Tare Mass?

what is the mass of an empty cargo ship to mass fully loaded? If an 8Mton cargo is half the maximum mass its drive system can handle safely, that would mean 4 million metric tons. That is a lot for interstellar trade.

Same question for passenger liners. If a passenger liner masses 600,000 and the ratio is 9:1 or ship mass to passenger/crew specific allowance it would mean 60,000 tons allocated to the passengers and crew. Allocating 1 metric ton to each passenger and crew and a 1:1 crew:passenger ratio that would mean 30,000 passengers.

That would translate to large floating cities running from orbit to orbit. And in HAE it would give a larger passenger complement on the passenger liner than the 3,500 listed.

For Houdini, Jesyk Combine could easily acquire several passenger liners, park them in an out of the way location and load piecemeal for the evacuation. Or am I being way off on this? KISS would seem to prefer this.

Ship mass in unknown, as it's actually a volume measurement expressed in tons because.

kzt wrote:Ship mass in unknown, as it's actually a volume measurement expressed in tons because.

You forgot *waves hands*

Edit - damn, once again beaten by a more concise answer.

kenl511 wrote:what is the mass of an empty cargo ship to mass fully loaded? If an 8Mton cargo is half the maximum mass its drive system can handle safely, that would mean 4 million metric tons. That is a lot for interstellar trade.

Same question for passenger liners. If a passenger liner masses 600,000 and the ratio is 9:1 or ship mass to passenger/crew specific allowance it would mean 60,000 tons allocated to the passengers and crew. Allocating 1 metric ton to each passenger and crew and a 1:1 crew:passenger ratio that would mean 30,000 passengers.

That would translate to large floating cities running from orbit to orbit. And in HAE it would give a larger passenger complement on the passenger liner than the 3,500 listed.

For Houdini, Jesyk Combine could easily acquire several passenger liners, park them in an out of the way location and load piecemeal for the evacuation. Or am I being way off on this? KISS would seem to prefer this.

I think the simple answer is, we're not sure.

The books do say that a wedge's acceleration is dependent on both volume and mass. But it appears to be vastly more dependent on volume.

I know for warships, in the "Great Resizing" their dimensions were re-calibrated by applying a standard average density to their listed mass. Which in effect means that their mass is more like gross register tonnage for ships - really a measure of volume rather than displacement weight.


Presumably freighters are measured the same way. So an 8Mton freighter is one with the same volume as an 8Mton warship. (However the only real data-points we have are the Trojan-class armed merchant cruisers (like Wayfarer) or one freighter from the SITS ship books. In both cases the tonnage seems basically inline with a warship of similar dimensions - though in both cases the merchant designs are shorter and fatter. But that only tells us their volume - not the max mass of cargo they can carry.

I'd guess that at some point you'd start losing acceleration if, for example, you loaded a freighter up with solid lead (or gold) - but at what point it starts to matter; and its possible to stuff them with enough dense material to over-stress their drive just isn't known...

IIRC Himself said long ago that the compensator parameters are set when the ship is built, and set for a fully loaded ship.
Thus the accel is always for a fully loaded ship, even if it happens to be empty.

Jonathan_S wrote:Edit - damn, once again beaten by a more concise answer.

kenl511 wrote:what is the mass of an empty cargo ship to mass fully loaded? If an 8Mton cargo is half the maximum mass its drive system can handle safely, that would mean 4 million metric tons. That is a lot for interstellar trade.

Same question for passenger liners. If a passenger liner masses 600,000 and the ratio is 9:1 or ship mass to passenger/crew specific allowance it would mean 60,000 tons allocated to the passengers and crew. Allocating 1 metric ton to each passenger and crew and a 1:1 crew:passenger ratio that would mean 30,000 passengers.

That would translate to large floating cities running from orbit to orbit. And in HAE it would give a larger passenger complement on the passenger liner than the 3,500 listed.

For Houdini, Jesyk Combine could easily acquire several passenger liners, park them in an out of the way location and load piecemeal for the evacuation. Or am I being way off on this? KISS would seem to prefer this.

I think the simple answer is, we're not sure.

The books do say that a wedge's acceleration is dependent on both volume and mass. But it appears to be vastly more dependent on volume.

I know for warships, in the "Great Resizing" their dimensions were re-calibrated by applying a standard average density to their listed mass. Which in effect means that their mass is more like gross register tonnage for ships - really a measure of volume rather than displacement weight.


Presumably freighters are measured the same way. So an 8Mton freighter is one with the same volume as an 8Mton warship. (However the only real data-points we have are the Trojan-class armed merchant cruisers (like Wayfarer) or one freighter from the SITS ship books. In both cases the tonnage seems basically inline with a warship of similar dimensions - though in both cases the merchant designs are shorter and fatter. But that only tells us their volume - not the max mass of cargo they can carry.

I'd guess that at some point you'd start losing acceleration if, for example, you loaded a freighter up with solid lead (or gold) - but at what point it starts to matter; and its possible to stuff them with enough dense material to over-stress their drive just isn't known...

We do have one data point, albeit incomplete (tonnage and acceleration only):

On Basislisk Station, Chapter 25 wrote:Honor frowned as something about the name Sirius jogged her memory. Then her eyes widened.
"Exactly," McKeon said. "That ship's been sitting in a parking orbit for over three months. I may be getting paranoid, but that strikes me as a mighty interesting coincidence in light of what the NPA's reporting."
"Excuse me, Skipper, but what do we know about this Sirius?" Santos asked. "Do we have any idea why she's here?"
Honor gestured at McKeon. He glanced back at his screen, then looked at Santos.
"She's big—a seven-point-six m-ton Astra-class," he said. "Captain Johan Coglin, People's Merchant Service, commanding. According to our files, she suffered an engineering casualty—or, more precisely, she's afraid she will if she moves on. Coglin reported his engineers spotted a fluctuation in his Warshawski tuners when he left hyper and declared an emergency. She's waiting for replacement tuners from home."

On Basilisk Station, Chapter 29 wrote:And that brought Honor right back to Sirius, for the ship in front of her obviously had a military-grade drive and compensator. Her sheer mass meant her compensator field was larger and thus less efficient than Fearless's, but no freighter should have been able to pull her acceleration. Even a superdreadnought, the only warship class which approached her mass, could only manage about four hundred and twenty gees, and Sirius was burning along at four hundred and ten. That left Fearless an advantage of barely a hundred and ten gees, little more than a kilometer per second squared—and Sirius had a head start of just under fifteen minutes.

Italics are the author's, boldface is my emphasis.

ericth wrote:IIRC Himself said long ago that the compensator parameters are set when the ship is built, and set for a fully loaded ship.
Thus the accel is always for a fully loaded ship, even if it happens to be empty.

Cargo ships rarely travel empty as they need a certain amount of cargo value just to break even.

Vince wrote:We do have one data point, albeit incomplete (tonnage and acceleration only):

On Basislisk Station, Chapter 25 wrote:Honor frowned as something about the name Sirius jogged her memory. Then her eyes widened.
"Exactly," McKeon said. "That ship's been sitting in a parking orbit for over three months. I may be getting paranoid, but that strikes me as a mighty interesting coincidence in light of what the NPA's reporting."
"Excuse me, Skipper, but what do we know about this Sirius?" Santos asked. "Do we have any idea why she's here?"
Honor gestured at McKeon. He glanced back at his screen, then looked at Santos.
"She's big—a seven-point-six m-ton Astra-class," he said. "Captain Johan Coglin, People's Merchant Service, commanding. According to our files, she suffered an engineering casualty—or, more precisely, she's afraid she will if she moves on. Coglin reported his engineers spotted a fluctuation in his Warshawski tuners when he left hyper and declared an emergency. She's waiting for replacement tuners from home."

On Basilisk Station, Chapter 29 wrote:And that brought Honor right back to Sirius, for the ship in front of her obviously had a military-grade drive and compensator. Her sheer mass meant her compensator field was larger and thus less efficient than Fearless's, but no freighter should have been able to pull her acceleration. Even a superdreadnought, the only warship class which approached her mass, could only manage about four hundred and twenty gees, and Sirius was burning along at four hundred and ten. That left Fearless an advantage of barely a hundred and ten gees, little more than a kilometer per second squared—and Sirius had a head start of just under fifteen minutes.

Italics are the author's, boldface is my emphasis.

Good point. Even without her dimensions (which, being way before the Great Resizing, would be incorrect now anyway) that's still enough to indicate freighters and warships seem to be measured in the same tonnage scake

ericth wrote:IIRC Himself said long ago that the compensator parameters are set when the ship is built, and set for a fully loaded ship.
Thus the accel is always for a fully loaded ship, even if it happens to be empty.

But then there is the situation where you have the ship fully loaded & then you add mass onto it externally such as tractoring pods against the hull. From all the evidence I have read this does not seem to affect the acceleration, only when the pods are deployed clear of the wedge does the acceleration decrease.

Thoughts anyone?

Rincewind wrote:

ericth wrote:IIRC Himself said long ago that the compensator parameters are set when the ship is built, and set for a fully loaded ship.
Thus the accel is always for a fully loaded ship, even if it happens to be empty.

But then there is the situation where you have the ship fully loaded & then you add mass onto it externally such as tractoring pods against the hull. From all the evidence I have read this does not seem to affect the acceleration, only when the pods are deployed clear of the wedge does the acceleration decrease.

Thoughts anyone?

Interesting thought. We know the acceleration is more tied to the compensator field than the raw drive power; any warship, at least, appears t be capable of accelerating hard enough to overwhelm its own compensator and flatten its crew.

My guess, for those few pods ships could "tractor inside their wedge", is that they were really tractor into them inside the compensator field (otherwise even BCs could have fit lots more inside their wedge. We know the ship's hull tapers down towards the drive nodes and, IIRC, that's because that area is subject to massive grav here during wedge startup. But I'd bet that that empty volume is still covered by the compensator; that you can't shape the field so precisely to exclude the cutback outside the tapers, while still including the hammerhead. That in effect you're always paying for that volume, even though you can't normally use it. But since the grav sheer seems to stabilize once the wedge is up, maybe that's where you can tractor some pods to avoid acceleration loss. If it's already compensated volume then putting a Pos there is nomdiffernt than filling a cargo bay (except that if you don't move them before raising (or lowereing?) the wedge you'll accidentally destroy the pods.

But that's inference and guess.