A idea for a big ship universe

[infojunky]

You'd want to multiply the draught by 2.5 or even 3.

As you can (hopefully) see, she's got a lot more height to the flight deck than just equal to her draught.

Ok, think 17 story building...
90 feet from the the flight deck to the water....

 

[mike wightman]

(GRTx2.8)/14=Traveller displacement tonnage for any ship of known GRT

 

[Rupert]

I generally assume spaceships need to be reasonably balanced to avoid excessive strain on the ship's structure and so they don't lose too much thrust having to thrust off-line and/or constantly add side thrust. Gravitics might counter weight, but mass and inertia still remain.

 

[mike wightman]

Inertial compensation...

 

[TamsinP]

You'd want to multiply the draught by 2.5 or even 3.

No. In my post before the one you quoted I provided the actual volume of the Ford-class carriers determined from the GRT registered with the USCG. That was 323,288m^3 (23,092 dTons) which is slightly lower than my calculation of 2 x length x beam (waterline) x draft = 331,068 m^3 (23,686 dTons)

As you can (hopefully) see, she's got a lot more height to the flight deck than just equal to her dr

She does indeed. However, multiplying the draft by 2x takes into account the non-box shape of the hull.

(GRTx2.8)/14=Traveller displacement tonnage for any ship of known GRT

Not quite - one GRT = approx 2.8 m^3, so you need to multiply the GRT by 5 to get dTons; your formula would divide the GRT by 5 so you'd get 1/25 of the actual dTons.

 

[mike wightman]

100,000x2.8 = 280000
280000/14 = 20,000

1 GRT is 100 cubic feet or 2.8 cubic meters.
(GRT x100) gets you volume in cubic feet
Divide by 500 to get Traveller displacement tonnage
(GRTx2.8) gets you volume in cubic metres
Divide by 14 to get volume in Traveller displacement tonnage.

Your suggestion 100,000 x 5 gives 500,000.

 

[TamsinP]

100,000x2.8 = 280000
280000/14 = 20,000

1 GRT is 100 cubic feet or 2.8 cubic meters.
(GRT x100) gets you volume in cubic feet
Divide by 500 to get Traveller displacement tonnage
(GRTx2.8) gets you volume in cubic metres
Divide by 14 to get volume in Traveller displacement tonnage.

Your suggestion 100,000 x 5 gives 500,000.

You're right. I clearly hadn't had enough coffee when I wrote that.

 

[whartung]

Inertial compensation...

It won't really help.

It prevents things from sliding around, but mass is mass, and there's still a center of mass to the ship that must be (somewhat) maintained.

So, when you take on the 10,000 dTons of lead, you may want to spread it around the ship a bit instead just shoving it all in the front by the door because your crew is lazy.

 

[mike wightman]

Mass doesn't matter in most iterations of Traveller.

 

[Rupert]

Mass being largely ignored in design sequences and the trade rules of most versions is not the same as it not mattering.

I'm sure the designers of ships in the TU have to consider thrust lines and getting them lined up so they go through a ship's centre of mass, and that they need to make sure that cargo holds are placed such that cargos within the ship's designed mass limits won't move the CoM too much. I'm also sure that proper, balanced placement of high-mass cargo is part of the cargomaster's job, along with making sure that cargo is placed so that the first stuff to come out isn't buried in the back corners, that any cargo passengers are entitled to access in-flight is actually accessible, and so on.

 

[mike wightman]

Inertial compensation deals with all that.
Inside the ship you can't tell if you are accelerating or not moving at all.

 

[Rupert]

She does indeed. However, multiplying the draft by 2x takes into account the non-box shape of the hull.

Fair enough, but you didn't mention that, and that makes it a non-universal method, and some ships (most steel-hulled cargo ships and big 20th century warships) are full in cross section, whilst others (sailing ships, for example) are not.

 

[Rupert]

Inertial compensation deals with all that.
Inside the ship you can't tell if you are accelerating or not moving at all.

That doesn't mean that an outside force (such as the engines) that's accelerating the whole ship doesn't care - inertia still exists, as does mass. This is especially the case if you take it that inertial compensation only functions in areas with emitter plates or the like, and isn't a field that encompasses the whole ship. If you do have it as a field, you could rule that the effective centre of mass is in the field's centre (or some other arbitrary point), which would be interesting (and what if the field goes off?), but I don't.

 

[bookwyrm]

I think inertia is actually a plot device?

On the one hand, no matter how much a space ship moves around, nothing on the inside budges a millimeter unless something affects the power or the 'inertial dampers'.

On the other hand, 'inertial dampers' are good enough to keep things in the ship from moving around during 'normal maneuvers', but when maneuvers become more energetic, that's when the effects of inertia can be felt and/or seen.

 

[Rupert]

I'm talking about inertia in the sense of ships as a whole - they keep moving when pushed, require thrust to change course, speed up or slow down, etc. What's more they require the same amount whether they have internal gravity, compensators, or whatever. From that we can assume they still have all their mass, and that says they have a centre of mass.

Thus the question is whether compensators, etc. remove the need to carefully place cargo, etc. to control the centre of mass or whether by some magic they make that unnecessary.

 

[Condottiere]

Depends on how far the inertial compensation field extends.

You might want to have the missile launchers outside that influence.

Wonder how a fired bullet fares?

 

[Grav_Moped]

Just for weirdness' sake, look at Annic Nova's deck plans and drawings.

Without the (hypothetical, fanon-ical) additional small craft docked where the plans in DA1 indicate, that thing's gonna be doing space wheelies... It looks cool and all, but then you get to the side view and -- whoopsie. (The designer knew this, but didn't say in the text what the problem was...)

Still going to be weird with one small craft pushing, 'cause it's going to be "hanging down" out the back by about 45^o if it's pointing through the center of mass.

 

[Silverhawk]

I'm sure the designers of ships in the TU have to consider thrust lines and getting them lined up so they go through a ship's centre of mass, and that they need to make sure that cargo holds are placed such that cargos within the ship's designed mass limits won't move the CoM too much. I'm also sure that proper, balanced placement of high-mass cargo is part of the cargomaster's job, along with making sure that cargo is placed so that the first stuff to come out isn't buried in the back corners, that any cargo passengers are entitled to access in-flight is actually accessible, and so on.

Sounds like this might be a plot complication to me.

 

[Rupert]

That is one reason I think it's better to assume that compensators do not interfere with the centre of mass, mass limits on cargo holds, and so on. Most of the time it can be ignored, assuming a competent crew, but when the referee needs something to spice things up, there it is.

 

[Marcatlas]

Given most of us are using some flavor of grav lift, do starships have weight limit for grav systems, more buoyancy then thrust, or need to be properly trimmed/balanced/ballasted?

Not according to RAW