T5 Only: Liberty Ship Development Discussion

[Enoki]

A SDB tender / carrier would be a variant of the Battle Rider / Battle Tender concept, only the carried ships would be smaller.

I personally don't like the idea because if the carrying ship is disabled or destroyed your riders are stuck. You can't withdraw because they lack jump capacity.

In a defensive setting where SDB's are used, I see them as anything from PT boat sized up to say destroyer sized but without jump capacity. They can be, and usually should be, scattered through the system to prevent an attacking force from taking outlying worlds or being able to refuel unopposed in the system they defend.
Against a major invasion fleet, they aren't going to stand up to it for long but rather provide time for one's own forces to group and arrive to oppose the attackers.
Their routine use would be to prevent piracy, deal with squabbles between merchant ships, and the like. They might be used in lieu of other ships for customs and police work too.

 

[Major B]

A SDB tender / carrier would be a variant of the Battle Rider / Battle Tender concept, only the carried ships would be smaller.

I personally don't like the idea because if the carrying ship is disabled or destroyed your riders are stuck. You can't withdraw because they lack jump capacity.

Well, it is pretty premature to start discussing this concept but now that the cat is out of the bag I can say that I don't see this as a battle rider/tender arrangement though there are some similarities. The SDB tender gives SDBs the strategic legs they lack and it can also fill some logistics support functions for an SDB force as long as the tactical situation permits. But they do not carry the SDBs into battle like a Battle Tender does. They jump in, drop off their charges, and then (fuel permitting) jump out. The SDBs stay behind and do what they do best - hide, harass, deny access to the gas giants by hiding within, and so on.

I'll cover that operating concept much later but first I need to come up with an original Liberty Ship.

 

[Whipsnade]

But they do not carry the SDBs into battle like a Battle Tender does.

That distinction cannot be emphasized more strongly.

We're not looking at a warship. We're looking at an auxiliary.

We're looking at a seaplane tender. We're looking at an aircraft ferry. We're looking at a depot ship.

We're not looking at a CV, a CVL, or even a CVE.

We're looking at a ship which supports and not a ship which fights.

 

[flykiller]

"In my experience the <fill in the blank> was often used in a role for which it was neither designed nor intended."

 

[aramis]

That distinction cannot be emphasized more strongly.

We're not looking at a warship. We're looking at an auxiliary.

We're looking at a seaplane tender. We're looking at an aircraft ferry. We're looking at a depot ship.

We're not looking at a CV, a CVL, or even a CVE.

We're looking at a ship which supports and not a ship which fights.

Technically, many CVE's should have been Auxiliary Carriers... the only difference being whether or not they were assigned to escort duty or ferry duty.

 

[whartung]

We're looking at a seaplane tender. We're looking at an aircraft ferry. We're looking at a depot ship.

We're not looking at a CV, a CVL, or even a CVE.

We're looking at a ship which supports and not a ship which fights.

Right, there's no supposition of deploying the SDBs in to combat, or even having that the SDBs are capable of combat after being released. They could be, they don't have to be. If it takes a day to unload the carrier of its ships, it's no big deal. If it takes a day for an SDB to be operational after unloading, that's no big deal either.

"Maybe we shouldn't carry a bunch of fueled up boxes stuffed with explosives packed tightly together."

 

[Major B]

I mentioned yesterday that I was thinking about 200 ton subhulls rather than 400. Here are some of the calculations I have been working on since then:

First, here is a dimensional diagram of the 200 ton subhull:



I like the 200 ton option for a number of reasons that boil down to it fits the original design intent better, provides more options to an owner, and gives me more flexibility in determining hull shape. My first idea gave me an overall hull length of over 250 meters so I came up with a different arrangement shown below. The two central subhulls are permanently attached together forming the central hull of the ship which should contain the drives and crew quarters. The six outer subhulls are connected with grapples and are detachable. Maybe.



I like this better but it has some problems fitting into the original concept.

First problem: The central hull is six subhulls long by two wide providing a 2400 ton central hull but this won't be large enough for either drives option. If I choose the M1,J2,P2 option I need 683.3 tons for drives plus 1,960 tons for fuel totaling 2,643.3 tons. The M1,J3,P3 option requires 1,087.5 tons for drives and 3,270 tons of fuel which sums to 4,357.5 tons (warning, this math was done by a history major).

Second problem: The arrangement is a bit uneven because the 10,000 ton hull is made up of 50 subhulls while six layers of the arrangement pictured above only uses 48 subhulls. The last two are attached to the nose of the main hull, an arrangement I thought might work until I started figuring out the space required for grapples and connectors.

T5 requires 3 grapple or connector pairs per 100 tons of linked subhull. Grapples are detachable while connectors are permanent. Grapples are a ton each and cost MCr1. Connectors cost the same and have half to volume.

So each main hull subhull needs to have 6 connectors and 18 grapples leaving only 179 tons of usable space left. Worse, each detachable subhull needs 24 grapples (leaving 176 tons of usable volume) at least if I am going to make them able to attach anywhere. And if I really mean anywhere, add on 6 more for the aft wall of each subhull if I am going to allow for attaching two to the nose of the main hull. That means each detachable subhull can only carry 170 tons inside.

I could make the two nose subhulls part of the main hull which would increase main hull volume to 2,800 tons. Better but if we have that length sticking out the front why don't we attach subhulls around that? It looks like wasted space otherwise. The 6 extra containers increase the 10,000 ton ship to an 11,200 ton ship which means I need to redo my drive calculations. Doing that also makes it possible to take the aftmost rosette of six outer subhulls and make them part of the permanently affixed main hull. This will give me some surfaces to mount defensive weapons on and increase the main hull internal volume to 4,000 tons and leaves me with 36 detachable subhulls with 7,200 tons of volume less grapples.

And speaking of all those grapples, maybe the subhulls need to be tailored to a particular mounting location which also leads me to think that they will be detachable in theory but rarely done in practice especially after the war.

I am also thinking that I could do the J3 drive option but put only enough fuel for J2 in the main hull and the remainder into detachable subhulls.

Anyway, posting this for thoughts and feedback while I figure out what the new drive and fuel volumes would be for an 11,200 ton ship.

 

[Whipsnade]

Hmmm... so a configuration somewhat like the P.F. Sloan? A central, general purpose, main hull surrounded by several, single purpose, sub-hulls?

Granted, the Sloan can't/doesn't swap out modules as needed. The Sloan's construction could be modular however with the central main hull and surrounding sub-hulls built separately and (permanently) assembled later.

Anyway, I like it. The configuration neatly ties into the "Build 'em quick & dirty" thinking behind the design.

Addendum:

And speaking of all those grapples, maybe the subhulls need to be tailored to a particular mounting location which also leads me to think that they will be detachable in theory but rarely done in practice especially after the war.

Very nice touch. "Yeah, we could swap them out if we really needed to, but we've never really needed to..."

You could differentiate the subhulls by dorsal/ventral versus port/starboard with certain types always/usually in certain locations; i.e. "The fuel subhull is usually a ventral mount but the examples built by Bilstein have that subhull mounted dorsally."

Mike's point regarding different starports/yards building different components is a winner too.

 

[Enoki]

A possibly better version is you have a "standard" propulsion, crew, and command / control module. You then can stick X number of standard cargo, passenger, or whatever modules in front of it, or possibly behind it too.
With several different sized propulsion and control modules you can make any size cargo or passenger ship you want.

 

[mike wightman]

If you want a really quick and dirty merchant ship then you have A starport shipyards build a jump frame and B starports the modules to be attached.

 

[Selandia]

.
.............
I like this better but it has some problems fitting into the original concept.

First problem: The central hull is six subhulls long by two wide providing a 2400 ton central hull but this won't be large enough for either drives option. If I choose the M1,J2,P2 option I need 683.3 tons for drives plus 1,960 tons for fuel totaling 2,643.3 tons. The M1,J3,P3 option requires 1,087.5 tons for drives and 3,270 tons of fuel which sums to 4,357.5 tons (warning, this math was done by a history major)..

Limit the fuel in the main hull to operation and J-1 (the minimum to operate as a cargo on the J-1 main). If strategic mobility require better of more jump, a number of the 200 t sub hulls will be fuel tanks (and use transfert pump). A trick is to use a carried on fuel shuttle (with 170 tons of fuel) that could be used to scoop from GG and will act as auxiliary fuel tanks

.Second problem: The arrangement is a bit uneven because the 10,000 ton hull is made up of 50 subhulls while six layers of the arrangement pictured above only uses 48 subhulls. The last two are attached to the nose of the main hull, an arrangement I thought might work until I started figuring out the space required for grapples and connectors.
..............
I am also thinking that I could do the J3 drive option but put only enough fuel for J2 in the main hull and the remainder into detachable subhulls.

that is the spirit, but see above, why not J-1 only in main hull?

Given the general purposefullness of the basic design, some 400 t stations will be welcomes and give more carrying capability/versatility to the ship and solve your under usage problem, The side stations are not crowded and extremities have rooms either fore or aft as well as up and down

Given yout visual. Put two rows of grapples (low and high) on each outboard side. Off set a row of subhulls upward and one downward and you have more subhull (10 per layer) that you need for 200 t carried subhulls

have fun

Selandia

 

[Major B]

Limit the fuel in the main hull to operation and J-1 (the minimum to operate as a cargo on the J-1 main). If strategic mobility require better of more jump, a number of the 200 t sub hulls will be fuel tanks (and use transfert pump). A trick is to use a carried on fuel shuttle (with 170 tons of fuel) that could be used to scoop from GG and will act as auxiliary fuel tanks

Thanks for the idea. I will get to filling the main hull pretty soon and if it comes down to it this is what Ill do.

Given yout visual. Put two rows of grapples (low and high) on each outboard side. Off set a row of subhulls upward and one downward and you have more subhull (10 per layer) that you need for 200 t carried subhull.

Hmm. I'll have to play with this over the weekend if I can - I have family visiting so may not be able to do anything with this until next week.

I have done some development that relates. I can limit the interior space devoted to grapples by designating which position the subhull will mount in. See the diagram for the picture version of this idea:



The top illustration shows the ship from the starboard side and below that from the aft end. Also, note that I corrected the hull length I showed in an earlier visual. The overall length of the ship (counting half meter gaps between subhulls) is 178 meters.

Here is the result of some more math work, calculating drives and fuel requirements for the 11,200 ton hull:

The most efficient arrangement for the M-Drive is a 2D7 providing 1G at a cost of 98 tons and MCr 196. That is a TL 9 Drive. A Modified Drive built at TL 11 provides 1.1 G for 49 tons and MCr 98. An Advanced Drive built at TL 12 provides 1.2 G for 33 tons and MCr 392. The small size of the Advanced drive is offset my the initial cost to install so I wonder whether the Modified Drive would be better.

If you strip all but 10 subhulls off of the main hull, the modified drive can make 2G. The advanced drive can do the same with 13 subhulls attached. The modified drive can push just the main hull with no subhulls at 3G and the advanced drive can do the same with 2 subhulls. However, none of those are possible unless I go with a braced cluster hull. Would there be an economic argument for the increased acceleration?

For the Jump Drive a Z7 arrangement is most efficient, allowing J3 at a cost of 875 tons and MCr 875. It is Standard at TL 12 so no reduction in price or volume allowed. Jump fuel requirements are 1,120 tons of fuel per parsec, 3,360 total.

A Z7 is best for the power plant too but that is a TL 10 product. A Modified P-Plant built at TL 12 only needs 255.5 tons and costs MCr 255.5. The efficiency of this drive saves some fuel volume too, with only 302.5 tons needed for a month of endurance.

Some comparisons:
Assuming I go with the Modified M-Drive to save up front costs, volume for all of the drives will total 1,179.5 tons.

If I want to put all of the jump fuel in the main hull, it wont fit (3,662.5 + 1,179.5 = 4,842 tons).

If I go with my idea in the last post and only put enough fuel for J2 in the main hull, it may work (2,542.5 + 1,179.5 = 3,722 tons) but with only 278 tons for controls, sensors, weapons, crew quarters, life support it seems unlikely.

Selandia's idea to only have fuel for J1 in the main hull seems like the best fit so far (1,422.5 + 1,179.5 = 2,602 tons leaving 1,398 tons of space in the main hull.

I just have to once more thank everyone for all of the feedback. I am really enjoying the collaboration. I will get another update up as soon as I can but it may not be until next week.

 

[Kaeto]

I'd like to know why they are calling it a Liberty Ship. The original Liberty Ship was a cargo ship designed to be easy and quick to build so as to keep up with the rate of cargo ship sinking done by the German U-Boat wolfpacks during WW II. They weren't meant for long term use. That the two remaining ones are still around is just short of a miracle.

 

[Whipsnade]

I'd like to know why they are calling it a Liberty Ship.

I explained that in Post #31 but it apparently bears repeating:

As also expected, sadly, this thread has been partially derailed by the Terminally Obtuse.

Clay Bush and Major B used the term "Liberty ship" as a bit of shorthand. Rather than type "A deliberately austere and technologically conservative design meant to be constructed rapidly in a number of locations in order to quickly replace ship losses and restore trade between the economic hubs in the Marches" they wrote "Liberty ship".

Clay Bush and Major B did not use the term because they wanted to and believed they should copy the Liberty ship down the pop rivets holding up the toilet tissue dispenser in the captain's day cabin.

Nor are Clay Bush and Major B stupid enough to think that the details concerning the merchant ship deficit in the 3FW era Marches are exactly those concerning the need for merchant shipping on WW2 Earth.

Let's keep focused on the idea and not on some minutiae-quoting, genital-sizing, contest.

 

[mike wightman]

You need to identify the civilian shipping that is being lost that warrants the construction of these things. The 3FW was long after the x-boat routes were established.

Megacorporations ship in bulk along trade lanes that mostly follow the x-boat routes - or the x-boat routes were set up to go where the megacorporations traded, take your pick.

We have the stuff in the Traveller Adventure, but it is a pseudo-small ship setting. In a large ship setting then the megacorp bulk tradeships need to be much larger, so the MT 10kt ship looks like a good fit.

Jump 3 should be the minimum, or they could be jump 4 in order to match the standard performance of Tukera ships.

I'm interested to see how a 10+kt ship can be constructed with the T5 rules...

 

[Condottiere]

They're disposables, manufactured as fast as possible with minimum resources necessary for marginal performance, and minimal crewing.

 

[Enoki]

That's why I'd suggest an engineering module that includes the crew accommodations, etc., as a single unit to which you attach the cargo and passenger modules. That way you have just one module that's really got any value. The rest of the ship is essentially disposable, from fuel tanks to cargo bays, to passenger accommodations.

 

[mike wightman]

Jump frame built at A starports and modules constructed at type B should speed it up a bit.
Something like a real world container carrier but instead of containers you have 90t 'cutter modules'.

 

[kilemall]

My earlier post got me rummaging around in my model railroad magazines for an article on the WW 1 ships built for government under the auspices of the Emergency Fleet Corporation. These were in the same vein as the WW2 Liberty ships.

The majority were built on by shipyards on the Great Lakes and model railroaders who are interested in creating dockside scenes refer to them as 'Lakers' their size determined by the size of the (ca. 1918) St Lawrence Seaway locks. Although a large number were scrapped in the 1920's, some lasted and served through WW2 into the 1950's in both American and foreign service.

The article mentions that many were actually more economical to operate in the 1930's during the depression than larger vessels.

I thought about building one of those laker models, perhaps giving it a different funnel for a 'later' version.

 

[kilemall]

I'd like to know why they are calling it a Liberty Ship. The original Liberty Ship was a cargo ship designed to be easy and quick to build so as to keep up with the rate of cargo ship sinking done by the German U-Boat wolfpacks during WW II. They weren't meant for long term use. That the two remaining ones are still around is just short of a miracle.

Hmm, perhaps there should be a starship build option for war contract vessels that are not supposed to last more then 5-10 years, and so not built to last for 40-80 years. Some multiple of cost and time to build, perhaps .3 to .5.

Of course that would make them more vulnerable to breakdown, damage by combat or environment, and not an option for normal new build merchant mortgage as they won't last long enough to pay off the note. In Traveller, TANSTAAFL.