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 Post subject: Shipbuilding
PostPosted: Wed Aug 11, 2010 6:46 pm 
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Layered armor

I've also given some thought to layered armor for ships.
relatively thin outer layer as a micro meteor bumper with a thick middle layer of foamed material to catch and disperse the plasma jet from micro meteor impacts backed by hard armor layer, maybe a layer of boron or lead based armor for radiation protection, and perhaps other layers too.

Striker gave a method for figuring total AV for multiple armor sources and gave an example of a battledress soldier inside a stone building.
So why not use it for custom armors?

Unfortunately, really high AV's can be had by careful choices of materials and thicknesses, so perhaps costs can be used as a brake on such gimmicks.

Make each layer double the cost of the layer underneath it?
or base cost of each layer added together times 2^number of layers?

making super-strong and very light armor should be possible, but it'll by cost prohibitive...

and no magic unobtainium armors needed to get strong AV's

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Last edited by Ishmael on Sun Aug 22, 2010 1:15 am, edited 2 times in total.

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 Post subject: Re: hull and armor ideas
PostPosted: Wed Aug 11, 2010 6:48 pm 
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I've become obsessive again :(

While doing a model of a largish freighter, I decided that I wanted to put the same effort into 'designing' it for a game. I'll end up using a weird hodge-podge on FFS1 and other bits and pieces taken from where-ever.

Wouldn't you know? I'm stuck on the hull already. I want more than just "hull= x dtons and heavy armor". I started thinking about structure and how it could be used in a realistic fashion as a limit to available thrust and the affects on performance when carrying different massed loads and how damage to structure can alter things.

I decided that structure covers any part of a ship that is responsible for carrying the mass of the ship/vehicle. Armor can be placed over the structure or else the armor can BE the structure ( monocoque construction ). I am just unsure as yet how to determine load carrying capacities for eiher the armor or the structure.

I've been studying materials and such things as stress, strain, young's modulus, buckling and toughness. I have a couple of ideas and I'll work through this all eventually.
Stress will relate to the strength of a material per unit area before failing in compression. strain relates to how brittle or flexible a material is. The ratio is Young's modulus, if I understand it correctly and can be graphed with stress and strain as the axis. Toughness is the area under the graphed curve and is the toughness described in the Striker, MT and FFS charts for armor.

So, given a structure's volume, we can determine the area of support in m^2 by dividing the volume by length along the axis of thrust. Using that and the material's compressive strength, we can find out the maximum force the structure can support without failing.
However, there is another factor to consider... buckling.
Given a material's compressive strength and the material's toughness, we should be able to guestimate at the material's modulus to be used in a simplified form of an equation giving the limit of stress before a structure buckles ( based on a simplified method from Euler).
F/A = E*(pi)^2/(l/r)^2
F/A is the same relationship for compressive strength
So the structure can support the lesser of the two amounts

For armor, I might use the thickness and approximate the x-sectional area of the armor using w*h*.7854 minus (w-2*thickness)*(h-2*thickness)*.7854 for use with the methods mentioned above.

Structure support and hull armor support add to each other.
The difference between the two is that structure takes damage only when called for by the hit tables once the armor is penetrated (MgT hit tables); the support from the hull armor takes damage every time the hull armor is penetrated regardless.

In order to make tracking damage easier, perhaps sructure can be given a number of 'points' based on load capacity ( 1 point per 50,000 Newtons, for example )
As damage is taken, the max thrust available before crumpling the ship goes down. You want more G's? Dump mass!
If aero drag exceeds the given amount of safe newtons, ship crumples in atmosphere.

As far as finding the young's modulus or compressive strength of materials, there is lots of info on the webs for common materials and alloys. Given that and the usual material lists' given values for toughness, I might be able to figure many of them out. Toughness is the area under the stress/strain curve and the slope of that curve is young's modulus. My calculus is very shaky, but I think I can work it out.

unless I've totally misunderstood things I've been reading that is

Just kicking an idea around.

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 Post subject: Re: hull and armor ideas
PostPosted: Wed Aug 11, 2010 7:50 pm 
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Some time ago I had to deal with a similar problem, the role of
armour and structure - and shape - in determining the crush
depth of submarines. It turned out that the shape of the ve-
hicle is no less important than the other factors. I am not sure
how much of an influence the shape would have on starships.
but it may well be worth to take a look at this factor, too.


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 Post subject: Re: hull and armor ideas
PostPosted: Fri Aug 13, 2010 12:56 am 
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found a cool site that give material properties for many materials such as might be useful for FFS1 armor ( much like Fok's material list )
The important bits are cost, density, tensile strength, young's modulus and rupture work ( rupture work is related to FFS 'toughness values )
the rest should help in my project

http://www.makeitfrom.com/browse-materials/

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 Post subject: Re: hull and armor ideas
PostPosted: Fri Aug 13, 2010 1:18 pm 
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One of the biggest problems in this area that Traveller has is that when you buy the hull, it has no initial size.

When you buy a 1000 ton hull, you get 1000 tons of usable space. So the hull, structure etc, have no physical size-cost.

What SHOULD have been done is that each material type should "cost" a percentage of the total volume to get your structure and hull ratings from the book. Then, as the material gets better, the percentage goes down and the cost per ton goes up. So you get a trade-off: low cost/lost tonnage or high cost/more tonnage.

Then reinforcing the hull or structure makes more sense and you add more material, which takes away more space. Even Armour should do that, which in the rules, it does.

Unfortunately, to fix that problem now would completely invalidate everything that had gone before and change how ships are designed.

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 Post subject: Re: hull and armor ideas
PostPosted: Fri Aug 13, 2010 1:56 pm 
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Cyborg IM1 wrote:
One of the biggest problems in this area that Traveller has is that when you buy the hull, it has no initial size.
When you buy a 1000 ton hull, you get 1000 tons of usable space. So the hull, structure etc, have no physical size-cost.

yes, I've been thinking about that and the best solution I can find is to base the ship's size off ellipsoids
V= l*w*h*.5236
in a spreadsheet, I have it rigged to give the dimensions based on volume and l:w:h ratios
I've also found a nifty approximation for ellipsoid's surface area. I'll dig it up if anyone is interested. It's suppose to give area with a max of 5% error for ellipsoids. I have that in a spreadsheet as well.
I figure that the '.5236' should be a variable where '1' gives a rectangular prism and can range down to '.3333' for a cone or '.17' for the classic type S scout. Perhaps this number should also play a part on the streamlining characteristics of the hull. I think, but am almost certainly wrong that the surface area of an ellipsoid should follow such a relationship. That's something I'll have to investigate.
Cross sectional areas for aero calcs and possibly structure calcs would be based on ratios of areas with squares/rectangles. A circular/elliptical section would be w*h*.7854 where the '.7854' might range from '.5' for a diamond x-section like a type 's' scout to '1' for a perfect box and the values' range between slowly changing between the two shapes with the ellipse being an intermediate shape.
But, wth, Traveller ships are all based off spheres anyways.

but right now, I'm fighting with material properties and traveller armor. Material 'toughness seems to be similar to Striker armor almost. Clearly this must be an artifact of the original designers merging other characteristics such as hardness/Young's_Modulus into it. They did focus on armor instead of structural bits and seemed to assume face-hardened steel. Published values for mild steel don't seem to match mild steel's material toughness values from sites such as I mentioned last post. Such values are given as Mj/m^3, but given how armor is rated per cm and that area units used to figure pen in guns,guns,guns are cm^2, this lets me use Mj/m^3 as j/cm*3. The differences caused by 'face hardening might be handled by the idea of layered armor from Striker where the face-hardened layer is high carbon steel layered on top of mild steel? Again...study study study.

Cyborg IM1 wrote:
Unfortunately, to fix that problem now would completely invalidate everything that had gone before and change how ships are designed.

That's okay by me
Even if this all goes in a wastepaper basket, its still 'playing' to me and I'm learning a lot of things I didn't know before
( which is partly why I do this sort of dopey non-standard stuff )
I really should finish the graphic though :|

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 Post subject: Re: hull and armor ideas
PostPosted: Tue Aug 17, 2010 1:57 am 
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I'm giving up up this stuff for now.
At least the structure stuff anyways....
I'll just use the equations for a cylinder that C.Thrash worked out before, but re-arranged to give max G's given the other variables.
I'll just apply them to the hull and the structure separately to find max G's that each can support. [Looks good in a spreadsheet so far.]
I'm assuming a ship density of .5, but will probably use a running tally once I get the sheet worked out better and use the .5 as an estimated performance.

The ship can then be monocoque, semi-monocoque, or space-framed.
monocoque uses the hull only, and takes structure point hits whenever the hull is penetrated ( Structure points based on mass of hull )
space-frame uses structure only and takes structure point hits only if hull is penetrated and the proper hit location is indicated ( Structure points based on mass of frame )
semi-monocoque uses the average G rating of the two and takes hits in either case ( Structure points based on mass of hull AND frame )
Still kicking ideas around in my head

monocoque works best from smaller ships and space frame works best for large ships.
Because I favor using thrust/mass to find accel, the flying tanks of the CT game won't exist imtu.

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 Post subject: Re: Shipbuilding
PostPosted: Sun Aug 22, 2010 4:32 pm 
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Code:
Zhang Qian
        "Silk Road" class transport ship built by Chilseok Industrial Manufacturing, in partnership with Ling Standard Products.
       
        length = 268m
       *width  = 43m
       *height = 27m
        Mass = ~22,400/~16,500 tonnes ( loaded/empty )
       
       *not including radiator panels
       
2200 dton hull                 
        unstreamlined
        open frame
                hull
                        xxx dton
                        material
                structure
                        75 dtons
                        material
                       
10 dton cargo containers        ( up to 80 attached )

500 dton fuel tankage

loaded means full load of cargo containers and up to 200dtons attached craft
( usually 2x 50dton shuttles but docking equipment can handle up to 2x 100dton craft )
unloaded means no cargo containers but up to 200dton craft attached
fuel mass used and its affect on performance not tracked for these examples
1 dton = 13.5 m^3

==========
Using MT reactionless thrusters

Main Engines
        3x 15 unit main thrusters ( tech-11 ) 54 dtons
                7500 tonnes thrust
                1050 Mw integrated power plant ( fusion )
                        uses 1.575 m^3 fuel per hour @ full output
                22,500 tonnes total thrust
                4.725 m^3/hr ( .35 dton/hr ) fuel use
                       
        1g accel fully   (  loaded  )
        1.4g accel empty ( unloaded )
       
===========
MT style jump drive
       
Jump Drive
        72 units Jump Drive installed
                64 units of jump drive for jump-1 ( loaded )
                        320 dtons fuel uses per jump-1 ( loaded )
                48 units of jump drive for jump-1 ( unloaded )
                        240 dtons fuel uses per jump-1 ( unloaded )
                72 units of jump drive for jump-2 ( unloaded )
                        360 dtons for jump-2 ( unloaded )
                       
I'm considering using MT jump drive numbers except that each jump drive unit should provide 500tonnes of 'J-thrust' and that the jump number available should be 'J-thrust/mass' so that very heavy battleships are slower to maneuver strategically than light-weight 'battle-cruisers'.

Besides, jump is affected by gravity wells which implies ( to me at least ) that mass, and its affect on gravity wells, should be an important factor in j-drive performance.                               
================================================================================

FFS1 rules
==========

Main Engines
        3x 16.64 dtons HePlar thrusters ( tech-10 )
                7500 tonnes thrust
                375 Mw integrated power plant ( fusion )
                        uses 94 m^3 fuel per hour @ full output
                22,500 tonnes total thrust
                282 m^3/hr ( 21 dton/hr ) fuel use
                       
        1g accel fully   (  loaded  )
        1.4g accel empty ( unloaded )
       
        after jump-1 uses 160 dtons of fuel, 340 dtons remain giving ~ 16 hours @ full thrust or ~48 gturns assuming 20 min turns ( 64 gturns for 15 minute turns )
        after jump-2 uses 320 dtons of fuel, 180 dtons remain giving ~ 8.5 hours @ full thrust or ~25 gturns assuming 20 min turns ( 34 gturns for 15 minute turns )

==========
FSS1 style jump drive
                     
Jump Drive
        64 dtons Jump Drive installed
                        160 dtons fuel uses per jump-1 (loaded)
                        320 dtons for jump-2 (loaded)
        48 dtons Jump Drive in use when jumping unloaded             
                        120 dtons fuel uses per jump-1 (unloaded)
                        240 dtons for jump-2 (unloaded)
==========


I'll probably go with FFS1 HePlar because I like the 'feel' of limited burns and limited fuel which forces serious planning and fuel management in combat ( fuel tank hits in combat will really hurt too ) and it seems more real science-y than flying around without any cares for weeks at a time at full thrust.
I think I'll want to work something out for jump-drives though. I'm not really happy with either version...they're close-but-no-cigar for me.
Hopefully, I didn't make any glaring mistakes so far

just kicking ideas around..

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 Post subject: Re: Shipbuilding
PostPosted: Thu Aug 26, 2010 3:51 pm 
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The rabbit hole goes deeper.....

I've about decided to discard Thrash's nice work because it doesn't take shape into consideration and that the idea of using compressive strength gave me really good numbers when modeling deeps sea stuff like the Trieste. Cross sectional area of the armor shell on each axis and compressive strength of the materials looks good, so I'll continue along that path.

After playing with numbers concerning material properties, it looks like Trav toughness is based on rupture work ( for ductile materials ) and resilience ( for brittle materials like glass ). Using E.Fok's listing of Aluminum as toughness=1 for my base material, I can get toughness numbers for a multitude of materials that are either close or even dead on for many of the homogenous materials in Trav. There are some curve breakers like 'music wire' that are a steel alloy and yet are very brittle though very strong ( crystaliron?). It fails without deforming much ( or at all ). the other characteristics give insane numbers for rupture. More than likely, this is characteristics similar to the face of face hardened steel, so Trav 'hard steel' may be mild steel with face hardening.
Looks like I'll have to focus on laminated materials and how their characteristics are determined

I think I've already found some good references on figuring characteristics of composite materials.

The obsession continues

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 Post subject: Re: Shipbuilding
PostPosted: Sun Aug 29, 2010 12:04 am 
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First pass at a spreadsheet testing my ideas on hulls
https://sites.google.com/site/moukotiger/files/vehicles.xls?attredirects=0&d=1
excel sheet w/ no scripts

this gives a reasonable approximation for different measurements of a hull given a specific tonnage in dtons, and a ratio of length:width:height
There is a slider to 'choose' a hull shape that ranges for 'box' through 'ellipsoid' to 'wedge'.
What's actually happening is that the hull is inside a bounding box and the shape morphs from filling that box 100% for 'box' to an ellipsoid and past that to an octahedron. An octahedron is the smallest shape that can fit inside a box where its 6 vertices touch the sides of the bounding box. Depending on where the vertices touch the bounding box, a type's' wedge can be made.
'Cylinder' is not a true cylinder but the ratios provided give a decent representation of one as far as volume and areas; cross sectional area is where the biggest flaw lies for cylinders.
There is also a ratio of total surface area to that of the bounding box's surface area, as well as ratios for each axis' cross sectional area ( useful for aerodynamic stuff.

I'm using E.Fok's material list for now and it turns out that a good estimate of a material's yield strength is material toughness * 225 MPa ( I'm sure Young's modulus would modify this somewhat...perhaps in the form of 'resilience?..more study is warranted ).
For many real world materials ( but definitely not all! ), this is also the same as compression strength ( for most metals at least ) and this allows me to figure the load capacity for a given frame as well as for an armored shell of a given thickness ( another good use for cross sectional area ).
By using this as the basis for load capacity, I can also estimate crush depth which also takes different shapes and dimensions into account besides spheres. So far, it gives a depth of ~11,000m for the Trieste along with other test cases such as the Japanese DSV within reasonable limits. I differentiated 'box' shapes by moving the yield strength to shear strength, which is ~60% of yield strength as the shape moves from 'ellipsoid' to 'box' or 'wedge'.
Discrepancies seem to be from differences in material capabilities between real-world and Traveller lists.

C.Thrash's method given less capacity than my method, but I cannot say exactly why as I have not yet considered buckling and I do not know what the parameters he's using beyond 'its a cylinder'.
I will later enforce a set percentage of the hull volume for structure/framework as the hull/armor itself is only made up of the outer shell. This percentage would comprise decks/gratings and other fittings inside the hull shell.

comments?

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