Criticals with (large) bays.

[Tupper]

In High Guard, in the weaponry chapter, it is noted that:

The Severity of a critical hit is based on 1% increments of the ship’s hull value (minimum 10 points of damage). For example, a ship with 10,000 Hull points that receives a critical hit that causes 224 points of damage, will sustain a Severity 2 critical hit.

So that would mean that even a large bay Meson Gun (doing maximum 140 damage) would be unable to cause a critical on a ship with more than 14 000 hits (i.e. having a hull size of 28 000 tons or more).

Two questions:

1. In the core rule book, the criticals seem to be based on increments of 10, rounded up. At what size does one start rounding down? My guess is 2000, since that's the smallest size mentioned in the large ships passage.

2. While a Meson Gun large bay might fail to register a critical on a large ship, could a missile bay do so? By my calculations, if all 120 missiles hit, even an average damage roll (14 on 4D) would give damage of 14*120=1680. This could critical an unarmoured ship with hull size 252 000 tons. Is this reasoning correct?

 

[AnotherDilbert]

1. In the core rule book, the criticals seem to be based on increments of 10, rounded up. At what size does one start rounding down? My guess is 2000, since that's the smallest size mentioned in the large ships passage.

Undefined. I have used the largest of 10 or 1% of Hull, so for a normal hull more than 2500 dT is considered a "Large Ship".

I believe the Core book system is basically intended for the ships in Core book, topping out at the 800 dT Mercenary Cruiser.

2. While a Meson Gun large bay might fail to register a critical on a large ship, could a missile bay do so? By my calculations, if all 120 missiles hit, even an average damage roll (14 on 4D) would give damage of 14*120=1680. This could critical an unarmoured ship with hull size 252 000 tons. Is this reasoning correct?

I believe not. A missile bay do no damage, missile barrages do. Conceptually a missile barrage is one or more missiles attacking the same target with a simplified procedure, but a large barrage is still a lot of small missiles doing small damage many times.

I believe the intent is not to have ships sniped by criticals, but ground down by attritional damage, with an occasional critical for spice.

 

[Tupper]

Great answers; thanks!

A follow up question would be: is the hull score used for the calculation the "initial" hull score or the "current" (post-damage) hull score? I had assumed it was the former, but if it was the latter, large bays could start critical hitting (badly) damaged ships, which would make them more useful.

 

[AnotherDilbert]

is the hull score used for the calculation the "initial" hull score or the "current" (post-damage) hull score?

As far as I know it's the initial Hull value.

I had assumed it was the former, but if it was the latter, large bays could start critical hitting (badly) damaged ships, which would make them more useful.

Not really, you need lots of (or high severity) criticals to disable a ship. It's probably easier to do the last hull damage to destroy the ship.

 

[Tupper]

I think if I'd done the rules, I'd have done without the +4 to hit with large bays (that produces disproportionate numbers of effect 6 hits, and therefore criticals) and then left the critical determination as round up. That way large bays would be useful for their ability to critical large ships, but having 100 large bays wouldn't necessarily be better than having one 50,000 ton spinal mount.

 

[AnotherDilbert]

I think the large bays were intended to be crit fishers, but during beta it was demonstrated that they were more effective at destroying large ships than spinals. That made battleships non-viable, so crits were nerfed to save the battleship concept.

 

[Tupper]

Say you need a 14 to get effect 6, and an 8 to hit, and you have:

Gunnery +2 (skill 2, unremarkable attributes)
Fire control +3 (because you're one of many large bays on a big ship, and so use advanced fire control)
Target evasion -3 (your target has a decent computer)
Range penalty -2 (long range)
Bonus for shooting at large ship +4 (because you're a large bay)

Then you hit on 4+ and crit on 10+. That means 10/33 of your hits are criticals (30%). This is scary if you have lots of large bays (hence the current problem).

On the other hand, if you get rid of the large bay bonus for shooting a large ship, that becomes:

Hit on 8+ and crit on 14+. That means none of your hits are criticals.

Now if you have a pilot who does a good job on helping the gunners (bonus +2), that's going to be: hit on 6+, crit on 12+. That means 3.8% of your hits are criticals. But you can't count on that every round. If you were in Medium range, you might be in this situation too.

If I consider the Tigress battleship, with 66 000 tonnes of spinal mount, that could be replaced by 132 large bays. On a good turn (the pilot's had her coffee), I might expect that (1/36) of them would critical, or 3.7 criticals per round. Absent some good fortune, that would probably take 10 rounds or so to build up to enough to take a ship down.

On the flip side, with the existing spinal mount doing 22DD damage, I might expect to do 77,000 damage on a hit. Further, since I can dedicate fire control to this one big weapon, my chances to hit/crit are probably

Gunnery +2 (skill 2, unremarkable attributes)
Fire control +5 (because this is my one main weapon)
Target evasion -3
Range penalty -2

So hit on 6+ and crit on 12. I'm going to be hitting a good 72% of the time, and doing about 50,000 damage, on average per turn. That means in 6 or so rounds I'd have killed a pretty big ship just by wearing down its hull.

So ... I'd choose the spinal mount in a slugging match against one big ship, the 132 large bays if I was engaging lots of smaller ships, firing at very long range, or in medium range with good pilot rolls on top of that. That seems good, since it means that each weapon has its pros and cons.

 

[AnotherDilbert]

You are forgetting a few modifiers, such as Evasive Actions (dodge) and Aid Gunners.

I would assume a competent Navy would put well trained and talented people in charge of a few billions worth of warship (or trillion in case of spinal). I would assume a good gunner is skill +2, characteristic +1, augmented with skill augmentation +1, and characteristic augmentation +1. For EDU based tasks such as firing capital weapons we can use an expert system for an additional +1 modifier. In total I think a good capital ship gunner could provide a +6 DM. YMMV.

In the same way a good capital pilot could provide a +5 DM.

So, for a spinal it looks something like:
Gunnery: +6
Fire Cntr: +5
Aid Gunners: +1 .... Average of 2D + 5 - 7 = +4 => DM +1
Evasion: -3
Dodge: -5
Range: -2
SUM: +2 so you hit on a roll of 6+.
Disregarding screens it takes 5 hits to kill a Tigress or 5 × 36 / 26 ≈ 7 shots fired (3.5 MdT warships).


Crit fisher large bays properly belongs to ~2500 dT frigates:
Gunnery: +6
Fire Cntr: +5
Aid Gunners: +1 .... Average of 2D + 5 - 7 = +4 => DM +1
Large Bay: +4
Evasion: -3
Dodge: 0 .... Can't dodge lots of small attacks.
Range: -2
SUM: +11 so you crit on a roll of 5+.

You need around 50 crits to disable a ship (Severity 4 Fuel or Power hit), so around 50 × 36 / 30 = 60 Large bays mounted on frigates (0.15 MdT warships) would disable any capital ship, regardless of size, hence crits nerfed...

 

[Tupper]

I had forgotten about augments. Even if we scrapped the +4 to hit, they'd still be critting on 9+ which would make 50* 36/10 = 180 large bays. 0.45MT of ships, which is still too few.

Traditionally (Trillion Credit Squadron), Traveller has assumed that a paucity of pilots is a constraint on ship design, so while tonnage might be more economical, pilot-wise, the frigates with large bays aren't.

If, instead, the large bays were in one big ship, the fire control would decline by 2, making the crit 11+, so we'd need 50*36/3=600 large bays. Or, put another way, a Tigress could, with its spinal replaced by 132 large bays, take another Tigress down in 600/132 rounds=4.5 rounds, which is better than 7 with the spinal.

So I see your point, even then.

By the way: why do you see fuel 4 and power plant 4 as the killers? I would have thought it was fuel 4, and crew 5. Power plant 4 can still be repaired (instantly with a huge damage control crew on the job) since the plant isn't destroyed. Am I missing something?

 

[AnotherDilbert]

By the way: why do you see fuel 4 and power plant 4 as the killers? I would have thought it was fuel 4, and crew 5. Power plant 4 can still be repaired (instantly with a huge damage control crew on the job) since the plant isn't destroyed. Am I missing something?

No, you are correct, I had forgotten about battlefield repairs of crits. Even the Crew-5 will not disable a ship, only the Fuel-4 is a sure kill.

A Power-4+ will only leave a large ship vulnerable for the rest of the Attack step, until it can repair in the Action step.