Even more space combat questions
- Thread starter kashre
- Start date
hdan said:
That's not how it works.
Example. You want to use enough plexi-glass to make a 100 ton ship protected from pistol fire. It takes one inch of the material to reach that armour level. One inch times the amount of area to cover = 1 ton (example only.)
A 10 ton fighter to get one inch of plexi-glass over its surface area takes 1/10 ton.
The Volume var in MGT rules takes the place of surface area var for simplicity. So, the % is the way to do it. it isn't total armour mass but, thickness.
DFW said:
I realize that, and I was wrong to use the term mass. I was thinking in ablative terms, and that was incorrect. (As in "x amount burns away under the laser in Y time".)
Since surface area doesn't relate to volume linearly, the % formula is an abstraction for game's sake, and abstractions can break down. I suspect it breaks down below 100 dTons, but only because high armor 10 tons fighters offend my sense of propriety.
A 10 ton fighter with 1" of armor over its entire surface has given up more % volume to that armor than a 100 ton ship with 1" of armor covering it, yes?
It's certainly possible that Traveller armor is so thin that the volume v. surface area is irrelevant on anything 10 tons or larger. I suppose it would be relatively easy for someone with a good grounding in geometry to compute how thick the hide of an Armor 4, 100 dt starship would have to be, and then how much volume that thickness of skin would take on a 10 dton fighter....
DFW said:
I'm not sure that thickness really scales that way. I'm no math genius (which is a hindrance playing Traveller some times
), but I think if you assume cubes for the hull form of the ship (cause that's how its easy for me to do the math) with 5% of their volume as an armored skin then:10t ship = .088m thick armor
100t = .189m thick armor
1000t = .4085m thick armor
I'm not sure if the "thickness" scales differently based on different hull shapes though... and I certainly don't want to calculate all of that out when designing ships.
I *do* think that armor should be less on a fighter for a given percentage of hull volume than on larger ships though... I might just declare it to be half as effective on any ship under 50t and leave it at that.
<snip my duplicate cube calculations>
DOH! I got sniped.
Doing the same math for a 15% "12 armor" ship oddly gets the same roughly 2x factor, so the fighter must spend not 1.5 tons but 3. More substantial in a 10 ton hull, but still possible.
In other words, what am I getting so worked up about? Sure, the same thickness costs 10% instead of 5%, but it's not that big a deal. At most, I could push for an "You only get 1/2 the value of armor on craft < 100 tons for the same percentage" rule, which at the higher end could (hand wave) represent less structural support and at the lower end actually approaches the right values.
I'm not sure the fight is worth it though.
DOH! I got sniped.
Doing the same math for a 15% "12 armor" ship oddly gets the same roughly 2x factor, so the fighter must spend not 1.5 tons but 3. More substantial in a 10 ton hull, but still possible.
In other words, what am I getting so worked up about? Sure, the same thickness costs 10% instead of 5%, but it's not that big a deal. At most, I could push for an "You only get 1/2 the value of armor on craft < 100 tons for the same percentage" rule, which at the higher end could (hand wave) represent less structural support and at the lower end actually approaches the right values.
I'm not sure the fight is worth it though.
kashre said:
That's the problem. Take a constant, a sphere. A sphere has the least surface area to volume of and solid. So, it would have the thickest armour. A needle shape has MUCH more surface area to volume. Thus, it would be a royal to not use a simplification method. If you make <50 tons 1/2, you should make >1000 tons ~2X.
I tried to calculate the armour for a 10 dton fighter and a 100 dton ship
with Fire, Fusion & Steel as an example.
The fighter and the ship have the same configuration and the same ar-
mour material, armour thickness and armour value. The material used is
bonded superdense, the armour thickness is 2.14 cm and the armour va-
lue is 60.
Fighter 1o dtons, needle, streamlined, 6 G
minimum hull thickness 2.14 cm (Gmax x 10 divided by toughness of the material)
hull plating volume 1.9 (ship size, table) x 0.8 (configuration, table) x 2.14 cm = 3.25 cubic meters
= 32.5 % of the fighter's volume
Ship 100 dtons, needle, streamlined, 6 G
minimum hull thickness 2.14 cm
hull plating volume 6 (ship size, table) x 0.8 (configuration, table) x 2.14 cm = 10.27 cubic meters
= 10.27 % of the ship's volume
It is after midnight over here, so I am not certain that my mathematics
are perfect, but I think the example shows where the problems with ar-
mouring small craft are hidden.
with Fire, Fusion & Steel as an example.
The fighter and the ship have the same configuration and the same ar-
mour material, armour thickness and armour value. The material used is
bonded superdense, the armour thickness is 2.14 cm and the armour va-
lue is 60.
Fighter 1o dtons, needle, streamlined, 6 G
minimum hull thickness 2.14 cm (Gmax x 10 divided by toughness of the material)
hull plating volume 1.9 (ship size, table) x 0.8 (configuration, table) x 2.14 cm = 3.25 cubic meters
= 32.5 % of the fighter's volume
Ship 100 dtons, needle, streamlined, 6 G
minimum hull thickness 2.14 cm
hull plating volume 6 (ship size, table) x 0.8 (configuration, table) x 2.14 cm = 10.27 cubic meters
= 10.27 % of the ship's volume
It is after midnight over here, so I am not certain that my mathematics
are perfect, but I think the example shows where the problems with ar-
mouring small craft are hidden.
I don't know if this will be helpful, but....
Most Traveller editions base ships on spheres, which is convenient.
Assuming you start with a known volume in dtons and you know the length:width:height ratio, then a reasonable approximations for ship dimensions, including surface area, can be found. But I would use a rough ellipsoid to account for the different configurations.
First, find the diameters for the main axis of your ellipsoid.
vol = dtons * 1400
ratios = lr:wr:hr
C= (vol/(.5236*lr*wr*hr)^(1/3)
length of ship = C * lr
width of ship = C * wr
height of ship = C * hr
now, find the total area of the ship's bounding box; the area of a box with the dimensions lw, wr, and hr
Area= 2 * ((l * w) + (l * h) + (w * h))
now, approximate area of ellipsoid, or 'stretched' sphere will be .5236 * area of this box that encloses it...viola...approximate surface area of the ship.
As an example... a 300dton ship with a ratio of 8:3:2
vol = 4,200 m^3
C = 5.51 , therefore
ship length = ~44m
ship width = ~16.5m
ship height = ~11m
Bounding box area = ~2,783 m^2
Ship approximate area = 1,457 m^2
from there, its easy to choose your armor thickness and armor value from toughness and thickness, then figure armor volume, armor mass from armor volume and density, and armor cost.
Various ship configurations can be account for with differing lr:wr:hr ratios
Otherwise, I'm betting that the percentages vary with the square/cube law for a constant armor value.
Most Traveller editions base ships on spheres, which is convenient.
Assuming you start with a known volume in dtons and you know the length:width:height ratio, then a reasonable approximations for ship dimensions, including surface area, can be found. But I would use a rough ellipsoid to account for the different configurations.
First, find the diameters for the main axis of your ellipsoid.
vol = dtons * 1400
ratios = lr:wr:hr
C= (vol/(.5236*lr*wr*hr)^(1/3)
length of ship = C * lr
width of ship = C * wr
height of ship = C * hr
now, find the total area of the ship's bounding box; the area of a box with the dimensions lw, wr, and hr
Area= 2 * ((l * w) + (l * h) + (w * h))
now, approximate area of ellipsoid, or 'stretched' sphere will be .5236 * area of this box that encloses it...viola...approximate surface area of the ship.
As an example... a 300dton ship with a ratio of 8:3:2
vol = 4,200 m^3
C = 5.51 , therefore
ship length = ~44m
ship width = ~16.5m
ship height = ~11m
Bounding box area = ~2,783 m^2
Ship approximate area = 1,457 m^2
from there, its easy to choose your armor thickness and armor value from toughness and thickness, then figure armor volume, armor mass from armor volume and density, and armor cost.
Various ship configurations can be account for with differing lr:wr:hr ratios
Otherwise, I'm betting that the percentages vary with the square/cube law for a constant armor value.
Without working the numerical integration for each unique configuration (not so hard to do with a computer if you are modelling it), there will never be a satisfactory approximation for this as given.
The abstraction of using volume - which is a good mechanic, btw - makes this level of detail hard to quantify. That is the nature of abstraction. Consider that one ship can have the same armour protection from 3 mm of 'armour' that another requires 15 mm for - due to configuration.
Of course, since this is fiction, one can rationalize the mechanic -> armour volume includes bracing and internal structural support (for effectiveness). Thus, one could then state a minimum X thickness of armour results in Y armour rating (the rest being the aforementioned justifications for the extra volume) for all but the more extreme cases (by ship tonnage and configuration type - this should be doable).
The abstraction of using volume - which is a good mechanic, btw - makes this level of detail hard to quantify. That is the nature of abstraction. Consider that one ship can have the same armour protection from 3 mm of 'armour' that another requires 15 mm for - due to configuration.
Of course, since this is fiction, one can rationalize the mechanic -> armour volume includes bracing and internal structural support (for effectiveness). Thus, one could then state a minimum X thickness of armour results in Y armour rating (the rest being the aforementioned justifications for the extra volume) for all but the more extreme cases (by ship tonnage and configuration type - this should be doable).
Well, I'm more interested in playability than in strict adherence to realism... which would be kind of silly in a game with reactionless drives and jump engines anyway.
My main problem is that almost any fighter is almost immune to the vast majority of weapons that might generally be shooting at it. In the play tests we did the fighters in the battles were more of a side show than anything else.
I think I'm going to split small craft in half and have the smaller half get 33% armor effectiveness and the larger half get 66%. If they're limited to 3-4 points of armor dogfights between a pair of 10 ton fighters will have some tension...
My main problem is that almost any fighter is almost immune to the vast majority of weapons that might generally be shooting at it. In the play tests we did the fighters in the battles were more of a side show than anything else.
I think I'm going to split small craft in half and have the smaller half get 33% armor effectiveness and the larger half get 66%. If they're limited to 3-4 points of armor dogfights between a pair of 10 ton fighters will have some tension...
Reading this discussion - found myself wondering about directional armour - a sphere doesn't really work but as soon as you go to a hull shape with less 'projected' cross-section, you should in theory be able to armour one facing and present that to the enemy.
Obviously it wouldn't work at close/adjacent range, you'd need to expend thrust to level the main armour at someone, and it'd (for the sake of rules simplicity) probably only work on one attacker at once, but the option for significant armour against one target without the volume associated with a 360' x 360' belt might be very interesting...
Obviously it wouldn't work at close/adjacent range, you'd need to expend thrust to level the main armour at someone, and it'd (for the sake of rules simplicity) probably only work on one attacker at once, but the option for significant armour against one target without the volume associated with a 360' x 360' belt might be very interesting...
I could even imagine it with a sphere. Just take a look at the mercenarylocarno24 said:
cruiser (the Broadsword type), the way it is designed it could be useful
to give the "northern hemisphere", which I think is normally turned to-
wards the enemy, a stronger armour than the "southern hemisphere".
Well... first off, under most any circumstances I think it's likely that fighters would be fired on by fighters as well, and pulse lasers vs 10+ armor aren't terribly useful.
As for warships, that depends entirely on the flavor and circumstances of the campaign. In the first (Megatraveller) campaign I ever played in we turned a 400t armed trader into an escort carrier and made our money doing anti-pirate work and escorting convoys during the Hard Times era. 90% of the fights we got in were against pirates with sub standard equipment, militarily speaking.
I have a player who has rolled up a fighter pilot, and I know he's going to do everything he can to involve fighters in the game somehow... so I want to balance and use fighters for the game in a way that gives him what he wants without making him immune to every non-warship we come across.
As for warships, that depends entirely on the flavor and circumstances of the campaign. In the first (Megatraveller) campaign I ever played in we turned a 400t armed trader into an escort carrier and made our money doing anti-pirate work and escorting convoys during the Hard Times era. 90% of the fights we got in were against pirates with sub standard equipment, militarily speaking.
I have a player who has rolled up a fighter pilot, and I know he's going to do everything he can to involve fighters in the game somehow... so I want to balance and use fighters for the game in a way that gives him what he wants without making him immune to every non-warship we come across.
