Hardpoints and surface area

[mike wightman]

What if hardpoints and their associated weapons were limited by available surface area only?

No need to worry about EPs and all that, can you fit them on your hull and in your hull?

A bit like LBB2 really

I dug out FF&S and put this together:
hull..hp
100 2
200 3
300 4
400 5
500 5
600 6
700 7
800 8
900 9
1000 9
2000 14
3000 19
4000 23
5000 26
6000 30
7000 33
8000 36
9000 40
10000 43
20000 66
30000 86
40000 106
50000 123
60000 140
70000 156
80000 170
90000 183
100,000 196
200,000 313
300,000 406
400,000 495
500,000 576
600,000 650
700,000 720
800,000 786
900,000 850
1,000,000 913

1 hardpoint can mount either a 1 ton turret, a 5 ton barbette, or up to a 35 t weapon bay.

50 and 100t bay weapons cost two hardpoints to install.

Note, one hardpoint requires 300 square metres of hull area. I chose this so that the Gazelle becomes legal

My idea is to use this table for LBB2, High Guard, and T20 design systems. TNE, and T4 already use surface area in their design systems.

edited note - GT:ISW does something like this with the configuration modifier that pops up later in the thread which I will add now for completeness - thanks to Dan
hp mod
x2.0 for Open Frame/Dispersed
x1.3 for Needle
x1.5 for Slab/Wedge
x1.1 for Cylinder
x1.2 for Box
x1.0 for Sphere
x1.2 for Disc/Flattened Sphere
x1.4 for Close Structure

 

[The Oz]

Shouldn't the available surface area be altered by the hull configuration? A sphere is the space with the least surface area for a given volume (as my old geometry textbook says) and so I'd think there'd be more surface area available for other shapes.

Does this seem like a reasonable order to put the HG configurations, from lowest surface area/hull volume ratio to the largest?

Configuration (HG USP Code)
Sphere (5)
Planetoid/Buffered Planetoid (8/9)
Flattened Sphere (6)
Close Structure (4)
Cylinder (3)
Cone (2)
Needle/Wedge (1)
Dispersed Structure (7)

I'm sure it's possible to calculate the relative "efficiency" of the configurations in giving surface area per unit volume, but I'm too tired to play with that tonight.

 

[far-trader]

I also think that a couple other big features should impact usable surface area/hardpoint availibility.

Externally mounted craft and drop tanks. I'd say lose half the hardpoints for civilian ships. Military ships might get away with a system of structural bracing to avoid the loss of hardpoints but probably at the cost of lost volume.

Large hatches such as for small craft bays and cargo holds. I'd say 1 hardpoint lost per such feature on civilian ships. And again military ships could avoid the loss of hardpoints with added structural bracing.

Just a couple thoughts.

 

[far-trader]

As for the surface area of different shapes you're corrrect but I think a single surface area rating based on the most efficient shape might serve well enough. Yes your flat shape has more surface area than a sphere but is it all useful surface area?

 

[far-trader]

Ah, it was my own house rule

I was just checking FF&S1 because it has the shapes and modifiers and surface area. However the way it did surface area didn't take the shape into account. Unless it was some errata I missed.

Surface area was strictly 100 times the material volume which was based on displacement. I added the material volume modifier from the configuration table, as well as for the streamlining (x1.0 for US, x1.1 for SL, x1.3 for AF). FF&S1 only modified the surface area for Airframes (to account for the lifting surface/wing area).

So, for what it's worth, using the FF&S MVM as a guide for the surface area of the configurations:

2.0 for Open Frame/Dispersed
1.3 for Needle
1.5 for Slab/Wedge
1.1 for Cylinder
1.2 for Box
1.0 for Sphere
1.2 for Disc/Flattened Sphere
1.4 for Close Structure

Except for the Open Frame/Dispersed hull form all the others are fractional and round down to 1 if you don't want to be fussy. And the Open Frame/Dispersed hull form while having more surface area may not be the most useful of surfaces, much of it pointing inside at your other hull structures

 

[mike wightman]

Originally posted by The Oz:
Shouldn't the available surface area be altered by the hull configuration? A sphere is the space with the least surface area for a given volume (as my old geometry textbook says) and so I'd think there'd be more surface area available for other shapes.

Yep, the tables are for spherical hulls and configuration should be taken into consideration, I just haven't got around to that bit yet

 

[mike wightman]

Originally posted by far-trader:
I also think that a couple other big features should impact usable surface area/hardpoint availibility.

Externally mounted craft and drop tanks. I'd say lose half the hardpoints for civilian ships. Military ships might get away with a system of structural bracing to avoid the loss of hardpoints but probably at the cost of lost volume.

Large hatches such as for small craft bays and cargo holds. I'd say 1 hardpoint lost per such feature on civilian ships. And again military ships could avoid the loss of hardpoints with added structural bracing.

Two very good ideas.

 

[castlebravo]

Sigg- I think your surface area vs. hard points ratios are right on the money.

Originally posted by The Oz:
Shouldn't the available surface area be altered by the hull configuration?

I calculate surface area by configuration. I also try and estimate surface area based on a configuration of multiple substructures. So one ship is built around a number of basic geometric substructures. For instance a single ship might be three large cylinders (cargo holds/propulsion systems) mounted underneath an oblong box (main superstructure) with another smaller oblong box mounted on top (forecastle/bridge decks). I use the general dimensions of the substructures to calculate total dimensions, mass, volume, surface area. I also try and guesstimate the number of hard points that can engage by direction or line of sight—bow guns, stern guns, port guns, starboard guns, dorsal guns, and ventral guns—based on the layout of the substructures.

Originally posted by far-trader:
I'd say lose half the hardpoints for civilian ships.

For me, this is not a engineering rule, but a design consideration. Civilian ships have less mounted weapons because the ship is not intended for combat, but for economic profit. Every credit spent on weapons and their associated systems and supplies makes a civilian ship less profitable. There is an implicit economic impulse to only mount the number of weapons absolutely necessary for self-protection. Since there is no physical/engineering reason why the surface area couldn’t be used for a mounted weapon, there should not be a engineering rule that demands it. In other words, don’t tell the naval architect how to suck the egg. He is compelled not to use hard points anyway.

Originally posted by far-trader:
Large hatches such as for small craft bays and cargo holds.

Agreed. I also think sensor and communication arrays, and propulsion nozzles should reduce available surface area and therefore available hard points.

 

[mike wightman]

Originally posted by far-trader:
So, for what it's worth, using the FF&S MVM as a guide for the surface area of the configurations:

2.0 for Open Frame/Dispersed
1.3 for Needle
1.5 for Slab/Wedge
1.1 for Cylinder
1.2 for Box
1.0 for Sphere
1.2 for Disc/Flattened Sphere
1.4 for Close Structure

And this saves me some effort, thanks Dan

 

[mike wightman]

Originally posted by Castlebravo15:
Sigg- I think your surface area vs. hard points ratios are right on the money.

Thanks

I calculate surface area by configuration.
<snip of useful stuff>

What I was aiming for was an alternative way to balance the number of weapons available to a ship, without having to track EPs for the weapon systems.
Following some excellent suggestions I'm wondering if max. hull hardpoints can be used as a much more versatile accounting system in simple ship design?

For me, this is not a engineering rule, but a design consideration.
<snip again>

I agree completely.

I also think sensor and communication arrays, and propulsion nozzles should reduce available surface area and therefore available hard points.

More to add to the list

Thanks for the feedback.

 

[castlebravo]

Originally posted by Sigg Oddra:
What I was aiming for was an alternative way to balance the number of weapons available to a ship, without having to track EPs for the weapon systems.
Following some excellent suggestions I'm wondering if max. hull hardpoints can be used as a much more versatile accounting system in simple ship design?

I think you hit the nail squarely on the head. You can generalize away EPs by saying that a ship of 'X' displacement has the necessary EPs inherently to supply ‘Y’ hard points. Works for me.

 

[mike wightman]

The next thing to do is get the number of hardpoints in the original tables sorted out.

As I said, I based the whole thing on 300m2 per hardpoint, and rounded down.
This could be changed, especially if hardpoints are also going to be used for:
weapons
external grapples
launch bay doors
cargo hatches
sensor/comms arrays
propulsion nozzles

 

[castlebravo]

Originally posted by Sigg Oddra:
I based the whole thing on 300m2 per hardpoint, and rounded down.

a ~17.5 meter x ~17.5 meter square is a fairly large area and provides allot of wiggle room for everything you mentioned, perhaps save the main aft propulsion nozzles (for large capital ships). Even a large 5 meter diameter antenna could fit comfortably within that footprint.

 

[castlebravo]

For comparison, a Trident II (D5) SLBM launch tube is only ~2 meters in diameter and ~14.6 meters deep into the hull. Launch bays... the wingspan of a F/A-18 Hornet (w/ wing-tip missiles) is ~12.3 meters.

 

[mike wightman]

Propulsion nozzles would be best handled by losing a percentage of hull hardpoints per G rating IMHO.

 

[Pickles]

This is saving me a lot of work!

Far Trader: Drop tanks, surface-mounted craft and hatches: I suggest calculating these on a case-by case basis and subtracting the area from the hull total.

Castlebravo: For sensor arrays, perhaps the old 'just how much of this computer volume is actually computer' debate can help out. Calculate hull space lost according to computer rating?

Sigg: The %/G rating for nozzles is elegant and going straight into my house rules.

 

[mike wightman]

I was thinking of something really simple:

weapons
hardpoints required already discussed, although spinal mounts should cost 1 hardpoint for the muzzle

external grapples
one hardpoint per grapple per "X" tonnage of carried craft or tank - what should the tonnage be?

launch bay doors
one hardpoint per launch bay, although a larger door would be needed for larger carried craft - I'll have to look at this one some more

cargo hatches
one hardpoint per cargo bay door

sensor/comms arrays
one hardpoint per full sensor/comm array. Extra systems may be carried for redundancy purposes but that'll cost you mare hardpoints.

propulsion nozzles
what's a sensible % per G rating? 1%, 2%, 5%, or 10% of hardpoints lost per G rating?

 

[castlebravo]

Originally posted by Sigg Oddra:
I was thinking of something really simple:
weapons
hardpoints required already discussed, although spinal mounts should cost 1 hardpoint for the muzzle

Not sure I am comfortable with my thoughts on this yet... but I note that per the three-gun turrets (guns elevate independently, so not triple-turrets) for the 16"/50 Mk 7 naval guns on Iowa class battleships...

13 meters long x 11 meters wide for the armored gun house (just the part of the mount you see above deck) with another 13 meters of gun tube protruding from the front of the gun house to the muzzle.

So say basically 26 meters x 11 meters.

This beats your 17.5 x 17.5.

Does anyone else visualize these type of ‘large’ mounts on heavy cap ships? Maybe two hard points for large mounts?

Even as I write this I am thinking... "the idea is to keep it simple stupid!"

 

[mike wightman]

Ah, but the triple turret you've just mentioned would be the equivalent to a 50t or 100t bay, and thus cost 2 hardpoints to install (see note at the bottom of the original tables )...

 

[castlebravo]

Originally posted by Sigg Oddra:
one hardpoint per grapple per "X" tonnage of carried craft or tank - what should the tonnage be?

The key value in one ship (the tender) conducting a close grapple of another (the rider) is not so much the rider's tonnage, but the contact surface area -- surface area of the rider that obscures the tender’s surface area.

Following again the kiss principle, if we think of the dorsal area of the rider in close proximity to the ventral surface of the tender, then say perhaps 1/4 (just the top) of the total surface area of the rider affects the tender’s available surface area.

At this point I would use whatever formula you use to relate displacement tons to surface area to convert and solve for your standard ‘X’ tonnage value (taking into account a 1/4 area value).