Carried vessel/craft design trivia

[sabredog]

Aluminum would make sense for civilian craft in a safe universe, but Traveller in all its iterations isn't safe. Besides, while CT doesn't have any information on the materials used to make non-planetoid hulls, Striker defines the materials used for armor for all vehicles at the different tech levels. It implies the use of such materials as superdense and bonded superdense.

In Megatrav those definitions are explicitly included as materials choices when designing starships. Now you could also argue that only armored ships need those heavier collapsed steel armors, but doesn't it say somewhere in the rules that a starship making a jump needs a "strong" hull? Stronger than say, and airplane?

Plus, don't forget the thing has to withstand greater acceleration forces, lateral and otherwise, than an airplane does (and you'd probably be surprised to see how much even a small fighter built from composites weighs compared to a similarly sized -but slower and less maneuverable - civilian craft).

 

[aramis]

Actually, it says (in MT) that it requires Striker/MT AV40 for micrometoroid and radiation protection. Even in Aluminum, that's still going to be a significant chunk of mass - 33cm basic steel equivalent - 66cm of aluminum at .8x the mass of steel is about 1.6x the mass of steel, and twice the volume. (BSD is listed as 14x the strength, but 15x the density, so 15/14 the overall mass.

You want lighter spacecraft? You reduce the armor ratings required. (Disposables like current launchers only need AV8... 2cm equivalent..

And there's the error in the design system. It is, however, consistent in all editions...

The masses of the equipment are reasonable in MT and TNE, and match closely with those of other design systems and with density calcs I've done back of the envelope on autmobiles, busses, and trains (done back in the 90's).

So the only thing which is unrealistic is the armor required. A scout courier, for example, has a base armor mass for 1cm of 40Mg. Aluminum hull for the same strength would be 64Mg. Times thickness. BSD would be 15/14 (about x1.07).

 

[aramis]

Unit Conversions, courtesy of Rowlett's Dictionary of units.
pound per square foot (lbf/ft2 or psf)
a traditional unit of pressure. 1 psf equals about 47.880 pascals (Pa), 0.478 80 millibars (mb), or 0.192 79 inch of water (in WC).
kilogram (force) per square centimeter (kgf/cm2 or kg/cm2 or kgsc)
a common metric unit of pressure equal to 98.0665 kilopascals (see below) or about 14.2234 pounds per square inch (lbf/in2 or psi). Similarly, one kilogram force per square meter is equal to 9.806 65 pascals.
kilogram weight (kgf)
a kilogram force (see above).


1psf= 47.88 Pa
÷9.8 to get kgf/m²
kgf/m² = psf * 4.882401227738321
Tf/m² (=Mgf/m²) = psf * 0.004882401227738321
Tf/m² = psf/204.81725146198832
Tf/m² ≅ psf/205.

So your 4000psf concrete is about 19.5 Tf/m², or about 44Tf/1.5mDeckSquare.

Oh, and landing force is multiplied by the G's of impact... a typical airplane landing is a 1.1 to 1.5 G event. We can assume a landing force with gravitics of about 1.1x weight. (Yes, Weight. Mass as affected by local gravity.) So, on a world with 0.5G, that concrete can handle about 2x the mass it could on a 1G world... or about 88Tf/DeckSquare.

 

[flykiller]

I've always gone the same route figuring that "Bridge" tonnage was as much a catch-all for avionics, flight control surfaces (or directional thruster controls), landing gear, and all the myriad things not explicitly detailed, but implied as part of the "controls the ship" components.

landing gear does not control the ship.

I'd say 1% for landing on prepared pads, 2% on level solid ground, 3% on rough terrain, and 4% on unstable terrain.

 

[far-trader]

landing gear does not control the ship.

True, but where the idea is coming from, the full text (CT B2) is:

The Bridge is "...basic controls, communications equipment, avionics, scanners, detectors, sensors, and other equipment for proper operation of the ship."

That covers a lot of stuff not explicitly mentioned. Including the landing gear in that seems not only reasonable but necessary given CT design rules in both B2 and B5 which don't detail every item. Landing gear easily falls under the "proper operation of the ship" where it includes being able to safely land.

Other design rules may of course need a different method but even FF&S which is probably the most complete and complicated set of rules doesn't explicitly cover landing gear. Requiring an addition for the inclusion of landing gear, or even the other way around and gaining space and credits for not having landing gear means invalidating designs. That's more work. And work that imo is not required.

EDIT: For what it's worth to the discussion my current method of design allocates the Bridge tonnage of CT ships as:

25% Workstations (at 1ton per workstation, being 1/2ton couch and console and 1/2ton access) - Minimum Bridge by law contains 5 workstations(*1) which may be assigned any required crew duty, or simply kept in reserve for future need. Workstations are quickly configurable to any shipboard control function including but not limited to Piloting, Navigation, Engineering, Gunnery, Communications, Sensors and Command.

(*1) Which are in addition to the Workstations included in Engineering (1 per required Engineer crewperson) and Gunnery (1 per turret, 2 per bay, 4 per screen, and 1 per 100tons of spinal). Optionally I'll include other Workstations in the common spaces for functions such as Steward, Medic and such.

10% Ship's Locker(s) which include 1 Standard Vacc Suit per crewperson (*2) and various emergency equipment stores.

(*2) In addition to the Engineering Locker(s) which contain 1 Hardened Vacc Suit per Engineer and 1 MMU per Engineer, as well as tools and parts for maintenance and damage repair.

15% Ship's Airlock(s) (*3) for personnel access in vacuum or hostile atmosphere.

(*3) Not including cargo airlocks and the Engineering Airlock(s), and the occasional specialized airlock such as for supplies or medical quarantine.

50% "Other" equipment and functions which is where I include commo, sensors, avionics, landing gear, attitude control thrusters, and docking clamps/anchors, and other equipment for proper operation of the ship.

 

[aramis]

I, also, usually took it from bridge tonnage. I'm now realizing, however, that given Traveller design parameters, anything that isn't landing on it's belly is cracking concrete.

If we take 1m tall gear (extends to 2m, for 1m past hull), and presume a + shape:

  +-----+
+-+-----+-+
| |     | |
| |     | |
+-+-----+-+
  +-----+

With 1.4m center square, and .9m flaps we get 3.2x3.2-4x.9x.9=7.0m² out of a 2.25m² bay, at 1/6th ton each, and we can assume about: 15 Tons per m² or about 105 tons per gear box, and then 5 boxes per Td, plus one box for hydraulic resevoirs, for about 525Tm per Td of gear, or about 1 Td per 50 tons.
Call it 2% for wilderness capable.
Call it 1% for rocky/large-gravel fields capable
Call it 0.5% for bedrock, heavily reinforced polymer, or interlocking metal plating fields capable.

Wheeled gears are going to be less efficient, too. Figure about 1/5th to 1/7th as effective...

Actually, given a 2m tall gear, we can extend the flaps to 1.9m... for about 12m² per deck square. but we only get about 3 per Td (36m²/Td for still about 50Td per TdLG)
A 1.5m gear, we get:9.8m²/deck square, but only get about 3.5 per Td... still about 50Td per TdLG.

 

[atpollard]

So your 4000psf concrete is about 19.5 Tf/m², or about 44Tf/1.5mDeckSquare.

Concrete compresive strength is 4000 pounds per square inch, not pounds per square foot, so your results need to be multiplied by 144 sq. inches per sq. foot.

 

[flykiller]

True, but where the idea is coming from, the full text (CT B2) is:

The Bridge is "...basic controls, communications equipment, avionics, scanners, detectors, sensors, and other equipment for proper operation of the ship."

That covers a lot of stuff not explicitly mentioned. Including the landing gear in that seems not only reasonable but necessary given CT design rules in both B2 and B5 which don't detail every item. Landing gear easily falls under the "proper operation of the ship" where it includes being able to safely land.

by that reasoning fuel is part of the "bridge" too. where the idea is coming from is "deckplans are hard" and "how far can the 20-dton bridge rule be ignored".

the proper solution is to detail out the individual bridge components and determine final actual bridge size that way. ain't difficult.

 

[far-trader]

by that reasoning fuel is part of the "bridge" too.

No, I really can't see that being a reasonable conclusion from the way the rules are written. Among other things fuel is already explicitly accounted for in the design separate from the bridge.

where the idea is coming from is "deckplans are hard" and "how far can the 20-dton bridge rule be ignored".

Again no, not in my case anyway. I do not believe deckplans are hard. They can be tedious, and some people have made easy to understand errors of scale. And sometimes I think it may just be laziness. Other times there is an artistic vision at play and the rules are set aside.

As for ignoring the 20dton bridge rule you'll note that my method does not. It accounts for it with a little more detail and in the spirit of the description.

the proper solution is to detail out the individual bridge components and determine final actual bridge size that way. ain't difficult.

But who would use it? "ain't difficult" ? I think you'd find it exceedingly difficult, short of using actual real life design software and fully trained experts. Any game simulation is going to be a compromise. It's just a matter of degree between full realistic simulation and suitable game simulation.

Detailing out every individual bridge component, and you can't stop there of course, every system aboard needs the same level of detailed accounting, is not the proper solution. Not for a game anyway. For building an actual ship of course. But not for a game.

I also expect, no matter how thoroughly you think you've accounted for every bridge (or other) component imaginable, before the ink had dried or the electrons had settled someone would be asking "Hey, you forgot about the widgets. ALL bridges (or other component) have widgets. Where are the widgets in the design? How much do they cost? How much space do they take? etc. "

 

[flykiller]

by that reasoning fuel is part of the "bridge" too.

No, I really can't see that being a reasonable conclusion from the way the rules are written.

completely agree, the rules definitely do not include fuel in the "bridge". but I wasn't talking about the rules, was talking about the reasoning, and the reasoning used to include landing gear as "bridge" would definitely include fuel. and for that matter just about anything else.

As for ignoring the 20dton bridge rule you'll note that my method does not. It accounts for it with a little more detail and in the spirit of the description.

not it doesn't. the "spirit" of basic controls, communications equipment, avionics, scanners, detectors, and sensors does not suggest landing gear, lockers, and air locks.

the proper solution is to detail out the individual bridge components and determine final actual bridge size that way.

But who would use it?

anyone willing to say landing gear is "bridge".

I think you'd find it exceedingly difficult

well, off the cuff, le's see.

communications
1 dton per light second of range, boosted by 1 light second per energy point diverted to comms, (1ep max)/(1dton of comm equipment). add 1 light second of range for each tech level above 9. these are for broadcast comms - directed comms at known frequencies to known locations may require 1 dton max at any distance.

there. now comm capabilities can be specified for individual ships in a regularized manner. don't like the numbers, change 'em, that's what refs are for. same for sensors, internal system monitoring, jump navigation, in-system navigation, etc.

I also expect, no matter how thoroughly you think you've accounted for every bridge (or other) component imaginable, before the ink had dried or the electrons had settled someone would be asking "Hey, you forgot about the widgets. ALL bridges (or other component) have widgets. Where are the widgets in the design? How much do they cost? How much space do they take? etc. "

I'm old school. anyone asks the question, I'll answer, "your game, figure it out. ain't hard."

 

[Scarecrow]

I think it was Scarecrow who made the front one (a narrow foot) double as a stairway from the forward airlock just behind the bridge.

I've never been keen on the landing gears on the Suleiman largely for aesthetic reasons. I don't like the vertical struts projecting from an angled surface. I just find it jarring - particularly at the front where the hull is so high off the ground that they need to be absurdly long. I wanted to design something that worked with the shape of the hull rather than sticking two fingers up at it.

I liked the way that Chiang did the landing legs on the Naboo yacht in Phantom Menace. They simply hinge up in line with hull and I decided that with mine, rather than have them dissapear inside a space-consuming box and have doors close over it, I'd make them part of the hull.

I wrapped the rear gears around the engines which meant I could have them quite large whilst not taking up a great deal of space.

Equally, the ship is a triangle and given that the only truly flat surface is between three points, it seemed logical to give the ship just one gear at the front. This meant that it could land more easily on uneven surfaces and the fore gear could be positioned mid-line, making it closer to the floor and thus shorter. It does make it less stable too, though so in the end I compromised and the single front gear was split in two.

I've always liked the Millenium Falcon style boarding ramp for my spaceships but the problem with that is that it doesn't work for ship-to-ship dockings out in the black. So I wanted an airlock that had both. So you have a walk-in air lock with a door at either end and a ring-dock-collar iris valve in the floor.
I wanted the ramp to come down at the front so that anyone boarding can be seen from the bridge (although that doesn't actually work on the Suleiman because of it's shape.)

As the front gear hinged down, it made sense to have the ramp be part of it and so I split it in half and had the ramp extend between the two halves.

Crow

 

[Gray Lensman]

Musta missed this one first time around....

but Scarecrows solution has always been mine as well, even had airlocks and ramps on all four when ships were big enough for four .

 

[BraselC5048]

I once ran the numbers for a free trader, and ended up with 4 landing pads, each 3 meters by 2 meters, or something like that (I can't quite remember, and I never wrote it down). It would be able to land in a field, as long as it wasn't too muddy. On the other hand, I used a mass of 1000 metric tons for the free trader. For armored ships, I calculated a density of about 9 metric tons per displacement ton, using titanium as the building material.
However, once you get much bigger then a free trader, having landing gear that can support a ship's weight becomes increasingly impractical. Of course, you can just have the antigrav support 95% of the ship's weight, decreasing the load on the landing gear. That does mean that you can't shut the ship down while you're doing that.
I allow ships up to 12,000 dtons (the maximum size in my campaign) to land on planets. They have landing gear, but it can't possibly support the ship's weight, so they have to keep the antigrav on when touching down in the wilderness. Landing in a port is pretty much exactly the same as dry-docking an ocean going ship, with the ship sitting on hundreds of blocks on a concrete pad. In fact, you can use a wet-navy drydock to do this without any problems. This does require that the ships have an essentially flat bottom, which means that spherical vessels are nearly impossible to design so they can land. These facilities are found in pretty much any port that expects to have anything larger then a couple hundred dtons come by.

 

[BlackBat242]

You don't even need a flat-bottomed hull.

Just a couple dozen independently-controlled hydraulic rams with swivel-mounted pads on their upper ends.

The ship hovers at the designated height, and the pads are raised until they make contact, then they are locked in place and the ship cuts its anti-grav.