Small ship universe

[SanDragon]

Heh.

All true. I am simply working in the rules set that I chose to work in ... Does that sound redundant.

I also stumbled across one of those consipiracy sites that wondered why the vast majority airplanes are still built as straws with wings when lifting body designs were safer, more cost effective, more fuel efficient, etc.

And in the interest of minimizing costs, most of my designs were streamlined boxes. Box configuration has a x 0.6 multiplier, streamlined has x 1.5, result = 0.9

And a sphere can't be air-framed! I like air-framed designs. They can crash-land somewhat gracefully.

Throwing another sabot into the machinery, maybe the small ships are what a planet just beginning to reach for the stars feels comfortable in using. Less material/manpower lost should the worse thing happen..?

 

[Dragoner]

Oh no, not the un-streamlined sphere discussion!

Spheres being unstreamlined is one of my pet peeves and something I ignore for the most part.

The problem with lift and aircraft is that the more lift an aircraft has, the more susceptible it is to adverse weather conditions or just even crosswinds, safety would become a prime issue.

 

[rancke]

Throwing another sabot into the machinery, maybe the small ships are what a planet just beginning to reach for the stars feels comfortable in using. Less material/manpower lost should the worse thing happen..?

Quite likely. However, the distinction between small ship universes and big ship universes is the maximum size of a ship. 5000T and 1,000,000T respectively. There are going to be plenty of small ships in a big ship universe. (Though there are going to be orders of magnitude more ships in a small ship universe).


Hans

 

[Fritz_Brown]

I also stumbled across one of those consipiracy sites that wondered why the vast majority airplanes are still built as straws with wings when lifting body designs were safer, more cost effective, more fuel efficient, etc.

A primary reason being they fit better at the gate. And, of course, lifting body designs *weren't* safer, etc, until really recently, and airlines don't just go out and buy new airplanes like an Apple fanboy buys iPhones.

 

[Fritz_Brown]

Spheres being unstreamlined is one of my pet peeves and something I ignore for the most part.

For spheres to be streamlined, they have to have stitches or dimples on them.

(Though there are going to be orders of magnitude more ships in a small ship universe).

A good reason to *use* the smaller ship universe.

 

[SanDragon]

A primary reason being they fit better at the gate. And, of course, lifting body designs *weren't* safer, etc, until really recently, and airlines don't just go out and buy new airplanes like an Apple fanboy buys iPhones.

That last little bit had me laughing out loud!

Spherical configurations in the MT Ref's Manual have the cost modifier as x 1.0, automatically streamlined. Woot!

 

[Timerover51]

Quite likely. However, the distinction between small ship universes and big ship universes is the maximum size of a ship. 5000T and 1,000,000T respectively. There are going to be plenty of small ships in a big ship universe. (Though there are going to be orders of magnitude more ships in a small ship universe).


Hans

A reasonable analogy would be the different size of merchant and cruise ships in our own world. You have enormous tankers, bulk carriers, container ships, and cruise ships, but you also have a very large number of some coaster cargo ships, small tankers that can get into smaller ports, barge and tug combinations, small containers ships for smaller ports, and the small cruise ships for getting into the more obscure or less-visited areas. If you take a cruise in the Caribbean, you get a very good idea of to how wide a range in size of merchant ships there are.

In Traveller, the very large merchant ships are going to stick with high-population worlds with Class A and B starports. Your smaller liners, subsidized merchants, and Free Traders are going to be working the Class C and lower space ports, and those planets without orbital ports. It is the smaller population planets that would have little attraction to a large trading company.

What is needed is to work up two different ship building systems for the game, one covering merchant ships, and one covering warships. That is something that I am working on.

 

[Timerover51]

I also stumbled across one of those consipiracy sites that wondered why the vast majority airplanes are still built as straws with wings when lifting body designs were safer, more cost effective, more fuel efficient, etc.

For a lifting body to be certified by the US Federal Aviation Administration as safe for passenger and cargo carrying, it is going to have to prove to the FAA that it is as safe as the aircraft currently in service, and then, of course, convince the public of that. Current aircraft have gone through an enormous amount of safety development in the past 100 years, and are built to extremely rigid standards. Every nut, every bolt, every piece of equipment on a commercial aircraft must be approved by the FAA. Given the enormous cost of certifying an new version of an existing aircraft, I would suspect that any company attempting to get a lifting-body design approved is looking at spending between 10 and 20 Billion Dollars, with no guarantee of success, before they can proceed past a prototype aircraft.

Back in the mid 1990s. I looked very seriously at getting an aircraft built in Poland called the AN-2, a biplane which makes a terrific bush plane, certified for use here in the US. Despite the fact that this aircraft had been flying since shortly after World War 2 in the Warsaw Pact nations, I was told that I needed to start from scratch. The minimum cost was likely to be about $2 Million, and that assumed that no modifications to meet US standards would be required. The funding people were open to the idea as long as the Polish government would privatize the plant were the plane was built at. The Polish government was not willing to do that, as they were also building military jet trainers there. That ended things right there.

 

[mike wightman]

The Happy Roger slow transport out of Hard Times, for example.
Any ship of tech 9 or less ( in MT, inertial compensation shows up at tech 10). TNE and FF&S1 has a section devoted to it ( ffs1 chapter 11 ). 6 G compensation doesn't appear in the OTU until tech 15.
tech 10 .... 1g compensation
tech 11 .... 2g compensation
tech 12 .... 3g compensation
tech 13 .... 4g compensation
tech 14 .... 5g compensation
tech 15 .... 6g compensation

You can stack them, so you can achieve 6g compensation by having 6 x the 1g compensation at TL10. FF&S2 made this explicit and the T4 books had a 14g fighter with full compensation.

Which 'rules as written'? TNE. MT, T4, home-made?
I merely gave my opinion as to why the 'big ship' vs 'small ship' question is moot.

Big ship vs little ship as per the OP - CT LBB2 vs HG2.

It would seem to me that many of these problems would be solved by applying some sort of 'realism' to them as well. Noone can survive 6 g for a month...so what? Only at tech 14 could that happen in the OTU anyways. Besides, if cube/square law is used, it quickly becomes apparrent that larger ships are incapable of such sustained accelerations anyways.

And once again you are picking and choosing which minor feature to invoke realism for. Plus you haven't got the compensators rule from FF&S right - you can stack the lower TL ones.

If you want realistic then no maneuver drives, no fusion power plants, no artificial gravity, no nuclear dampers, no meson guns/screens,

However, for small maneuvers such as evading, humans can survive more than 6g's without too much trouble with proper equipment even without g-compensation. Red Bull Air Racing penalizes pilots who pull more than 12 g's. The planes are generally rated in the -10g/12g range.

So now we have space fighters dogfighting like in Star Wars - and you want realism?

"Strawberry Jam" is a human limit to accelerations, not a structural one. And it is probably much higher than usually imaged in the OTU for ships...well over 15 g's, I'd think ( and I'd be right ).
And meaningless when discussing RPV's, drones, etc.

One of the reasons real world fighters will be replaced sooner or later by remotely piloted vehicles.

 

[Ishmael]

You can stack them, so you can achieve 6g compensation by having 6 x the 1g compensation at TL10. FF&S2 made this explicit and the T4 books had a 14g fighter with full compensation.

Not according to FFS1.

And once again you are picking and choosing which minor feature to invoke realism for. Plus you haven't got the compensators rule from FF&S right - you can stack the lower TL ones.

Not according to FFS1
Citation required.

But then again, MT simple allows any g-comp above tech 9 to completely negate the effects of inertia within the ship, but it is power hungry requiring .27Mw per dton, or 27Mw for a 100dton ship. Add grav plates at .675Mw/dton, or 67.5Mw for a 100 dton ship...... just over 94Mw just to power grav and g-comp only. Might be a little power hungry for some ships, eh? ( from MT RAW )

If you want realistic then no maneuver drives, no fusion power plants, no artificial gravity, no nuclear dampers, no meson guns/screens,

Irrelevant to my discussion for reconciling a 'big ship' vs 'small ship' universe, but yes, I have done ATU's like that, although I have used, and would use again, fusion power plants as a likely future development.

So now we have space fighters dogfighting like in Star Wars - and you want realism?

That's what you got out of my previous post demonstrating that humans can handle, without g-compensation, fairly high g's for maneuvers such as evasion? wow.... just wow.
( hmmm OTU battleships' spinal mounts equate to fixed forward firing guns.... jockeying for a shot and evading the opponent's forward field of fire would not be dogfighting how? )

But in such an ATU, fighters/small_ships would be much more agile than batteships, yes.

 

[Ishmael]

(Though there are going to be orders of magnitude more ships in a small ship universe).

I wonder if one might guesstimate the numbers using Zipf's law or some power law

 

[BlackBat242]

What is needed is to work up two different ship building systems for the game, one covering merchant ships, and one covering warships. That is something that I am working on.

Lloyd's Rules for Ships

Lloyd's Rules for ships are derived from principles of Naval Architecture and Marine Engineering, and govern safety and operational standards for numerous merchant, military and privately-owned vessels all around the world. Lloyd's Rules govern a number of topics including:

Materials used for construction of the vessel.
Ship structural requirements and minimum scantlings, dependent upon ship type.
Operation and maintenance of main and auxiliary machinery.
Operation and maintenance of emergency and control systems.

Specific editions of the rules are available to cater for merchant ships, naval ships, trimarans, special purpose vessels and offshore structures.

See? A real-world example of different design rules for different ship types!

:rofl:



PS: scant·ling (ˈskant-liŋ, -lən) n.

1. The dimensions of a building material, especially the width and thickness of a timber.
2. In shipbuilding, the scantling refers to the collective dimensions of the various parts, particularly the framing and structural supports. The word is most often used in the plural to describe how much structural strength in the form of girders, I-beams, etc. is in a given section.

 

[Timerover51]

See? A real-world example of different design rules for different ship types!

Blackbat, I am well aware of the Lloyd's Standards. In order to speed production of ships in World War 2, the UK built several of the ASW escort classes to merchantile standards, among them the Flower class of corvettes, the Loch and Bay classes of frigates, the River class frigate, and the Colossus class of light fleet carriers. This also allows merchant shipbuilding yards that had no experience in building warships to produce escort ships. All of the World War 1 and World War 2 UK military trawlers were also built to merchantile standards.

That is why I say that there should be two different ship building systems in the game.

With respect to scantling, would you care to discuss the benefits of transverse verses longitudinal framing, and where you might wish to use a combination of the two? Or the tradeoff between increasing the strength of a ships hull plating compared to increasing the strength of the scantlings? Or what is meant by the term "ship strength girder"? Or why you might want to use external instead of internal framing for a submarine, even though the external framing means that you need a slightly thicker hull plating?

If you are interested, I would recommend reading a copy of Hovgaard's A Modern History of Warships or his Structural Design of Warships. I finally broke down and bought a copy of the latter to go with the earlier book. Go search SNAME or the American Society of Naval Engineers. At present, I have let my membership lapse. I still serve on the Marine Forensic Panel as the weapons, weapon effects, explosives, and explosions expert.

 

[BlackBat242]

I'm not THAT into maritime engineering (I'm an avionics guy, most of my structural knowledge, such as it is, relates to airframe structures)!




I simply am aware of some of the terminology, and have a very superficial, passing acquaintance with the meaning and use of some structures (mainly what you get from reading things like D. K. Brown's Rebuilding the Royal Navy).

As for your questions, I'd suggest the following as strictly amateur (and possibly mistaken) opinions:

For submarines the external framing allows maximum useable internal volume for minimum pressure hull diameter (crush depth being somewhat related to p-h diameter, the smaller the deeper). Additionally, this makes "double-layer hull" construction easier, which aids streamlining for ballast tanks and other external items, as well as providing a degree of damage-reduction due to the unpressurized outer hull reducing the pressure-wave hitting the pressure hull from depth charges, torpedoes, etc.

Internal framing is easier to build but restricts internal volume, makes streamlining harder, and is best for "single-layer hull" designs.



I think (not know) that you can get a lighter ship structure by increasing the hull plate thickness while decreasing scantling strength (good for displacement-limited designs, as well as reducing material costs for merchant designs), while stronger scantlings are more damage-resistant, and can support heavier structures (like armor plates, gun turrets, etc).



Transverse vs longitudinal relates to expected wave heights & periods, with transverse reducing twisting while longitudinal reduces bending along the ship's axis when the bow & stern are lifted by a wave but the amidships is over a wave trough (and vice-versa). A ship intended for high speed in rough seas absolutely needs both, as do long & narrow ships like destroyers.

Armored-belt ships have less need of longitudinal, as the belt adds strength in that area, while armored-deck ships need less transverse as the deck armor substitutes partially.



"Ship strength girder" is the combination of hull plating and framing which provides longitudinal strength. An example of this, and of differing approaches, is to compare USN pre & mid-WW2 carrier construction vs RN ships.

The US had the hangar deck as the "strength deck" (the upper-most deck which provides structural rigidity) with the hangar and flight deck being non-strength "superstructure". This requires fairly heavy hull framing due to the great length vs "depth" (height) ratio, but allows easy modification of the above-deck structure (like moving elevators from centerline to deck-edge).

The RN had the flight deck as the strength deck, with the hangar sides providing part of the hull girder along with the lower hull sides. This allowed lighter scantlings due to the better length vs "depth" (height) ratio, but made moving elevators to the deck-edge far more difficult. HMS Hermes was modified after launch with her fore elevator moved from the centerline to the port deck-edge... this required extensive changes to the port hull structure below the hangar deck (and, I believe, to the flight deck support structure on the underside of the flight deck) to compensate for the loss of girder strength from the cut-out in the hangar side for the elevator.

 

[Timerover51]

Not bad, Blackbat. I thought that the thread had gone dead.

However, I did locate something in the MegaTraveller Referee's Manual that lets me load a 200 displacement ton Free Trader with up to 1000 tons of cargo or more, depending on the mass density of the cargo.

Page 57, Referee's Manual, MegaTraveller:

A starship that displaces 100 tons may actually weigh over 1000 metric tons.

Not only does that make operating a Free Trader a lot easier, it also makes all of the cargo ships far more capable of moving large weights of cargo, which means less of a need for larger merchant ships. Given that quote, a Free Trader can move 1107 metric tons of carge, a Far Trader can move 823 metric tons of cargo, and a Fat Trader can move 2700 metric tons of cargo.

That does assume each cubic meter (kiloliter) of cargo space equal to one metric ton of cargo, figuring that cargo to weight the same as 1 cubic meter of fresh water. However, even if I use a relative low loading of 100 cubic feet per ton of cargo, then for each displacement ton of cargo volume, I can load 4.76 tons, call it, 5 tons of cargo. That would give me 410 tons of cargo for a Free Trader, 305 tons of cargo for a Far Trader, and a 1000 tons of cargo for a Fat Trader. If you use the 1000 Credits per ton cargo fee, one full trip a month covers their costs, two full trips a month and they are turning a very nice profit.

I do not remember that gaping loophole in Classic, but I will need to go back and look.

Oh, and just for everyone's information, one metric ton of Liquid Hydrogen occupied a volume of 14.114326 cubic meters, based on the 70.85 kilograms per cubic meter reported by the National Institute of Standards and Technology. This is equal to 498.44272 cubic feet, which is easier for me to work with, as pretty much all of my loading data for possible cargos is measured in cubic feet.

 

[Fritz_Brown]

Cargo has always been in displacement tonnage, timerover. You start talking mass tonnage with Traveller ships and you're just going to confuse folks. Especially since the mass doesn't matter (between grav lift and acceleration compensation). I'm pretty positive the 1000 Credits per ton cargo fee is per displacement ton, too.

Calling Far-Trader! Oh, Dan! Far-Trader, come in!

 

[Orr]

Cargo has always been in displacement tonnage, timerover.

He does see to have confused volume with mass.

You start talking mass tonnage with Traveller ships and you're just going to confuse folks.

Doesn't GT use mass and Imperial units to boot? Maybe that's where he got confused.

 

[mike wightman]

The CT original edition trade section does imply that 1 displacement ton of cargo usually has a mass of 1000kg.

In fact if you read the original edition ship building rules sideways sort of you could get the impression that tons mean 1000kg in ship construction. The term mass displacement ton is used throughout the construction rules.

In the non-starship section it mentions fuel being consumed by smallcraft at the rate of 10 kilograms (1/100th of a ton) per 1G per 10 mins.

Slight aside it also implies the maneuver drive is some sort of reaction drive since the fuel is used for 288 burns.

 

[Fritz_Brown]

Doesn't GT use mass and Imperial units to boot? Maybe that's where he got confused.

I think I have heard that critique of GT before. (Never used it myself.)

info

It figures. /facepalm/

 

[PFVA63]

Hi

I think an important thing to keep in mind volume wise is that a small ship universe size limit of 5000 dtons really isn't necessarily that small.

I had a plot once (which I currently have misplaced) showing how the internal volume of modern naval vessels compare to their 'hydrostatic' deisplacement (or basically weight).

In general, if I am recalling correctly, the US Navy's amphibious ship LSD 49 USS Harpers Ferry is just a bit over 5000 dtons (70,000 cubic meters) in internal volume, and has a full load 'hydrostatic' displacement (~weight) of about 16,600 tons (37,184,000 lb) and is 610ft (190m) long with a width of 84ft (26m).

[Edit] PS. I also belive that a ship like the US Navy's Burke Class destroyers were near 2000 dtons in internal volume, while the Oliver Hazard Perry class frigates were close to 1000 dtons, and the US Coast Guard's 270ft Medium Endurance Cutters were close to about 460 dtons.

[/Edit]