Spacelane Defense

[BardicNerd (OP)]

Just came back to Aurora after quite a long break, and have been very much enjoying the updates that have come since I last played .  .  .  and was a bit surprised and unprepared for the raiders.

I did have some basic defense ships when they first appeared, but they were not quite up to the task, and so I had to scramble a bit to come up with an effective counter.   By now I have a generally effective strategy to deal with them, and wanted to post my designs for review and get suggestions for the next generation as I move into a new phase of extra-solar colonization.

For reference, general specifications of the raiders I have faced so far: they use only railguns (with a max observed range of 160k km), have missile decoys, have a max observed speed just under 6k km/s, have a small level of ECM, and come in two sizes for the combat ships, 10k tons and 20k tons, both 90% cloaked so they appear to sensors as 100 tons and 200 tons

When they initially attacked, my armed ships consisted of 2 Scout Cruisers that had been intended as escorts for my survey ships out of system but were never actually deployed, and 6 patrol craft intended for system defense.   Neither could really counter the threat, as they were not fast enough to realistically make an intercept, and their active sensors couldn't see the enemy ships until they were on top of them.   I focused on the smaller ships, refitting the patrol craft as soon as possible and designing a Corvette that was specialized for interception.

These are the most recent generation of those:

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Enterprise III class Patrol Craft      8,719 tons       285 Crew       2,179.7 BP       TCS 174    TH 1,441    EM 0
8263 km/s      Armour 4-37       Shields 0-0       HTK 64      Sensors 16/8/0/0      DCR 13-14      PPV 52
Maint Life 2.55 Years     MSP 857    AFR 187%    IFR 2.6%    1YR 184    5YR 2,756    Max Repair 268.8 MSP
Magazine 344 / 0   
Commander    Control Rating 1   BRG   
Intended Deployment Time: 12 months    Morale Check Required   

Inertial Fusion Drive  EP480.31 (3)    Power 1440.9    Fuel Use 87.98%    Signature 480.31    Explosion 14%
Fuel Capacity 660,000 Litres    Range 15.5 billion km (21 days at full power)

15.0cm C8 Far Ultraviolet Laser (2)    Range 300,000km     TS: 8,263 km/s     Power 6-8     RM 50,000 km    ROF 5       
CIWS-200 (1x8)    Range 1000 km     TS: 20,000 km/s     ROF 5       
Beam Fire Control R320-TS8000 (1)     Max Range: 320,000 km   TS: 8,000 km/s    ECCM-2     97 94 91 88 84 81 78 75 72 69
Inertial Confinement Fusion Reactor R17 (1)     Total Power Output 16.6    Exp 5%

Size 7.00 Missile Launcher (75.00% Reduction) (8)     Missile Size: 7    Rate of Fire 65
Missile Fire Control FC9-R20 (1)     Range 9.5m km    Resolution 20
Kestrel Anti-Ship Missile Mk2 (48)    Speed: 63,200 km/s    End: 1.4m     Range: 5.3m km    WH: 30    Size: 7    TH: 210/126/63

Active Search Sensor AS81-R40 (1)     GPS 8960     Range 81.7m km    Resolution 40
EM Sensor EM1.0-8.0 (1)     Sensitivity 8     Detect Sig Strength 1000:  22.4m km
Thermal Sensor TH2-16 (1)     Sensitivity 16     Detect Sig Strength 1000:  31.6m km

Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s

This design is classed as a Military Vessel for maintenance purposes
This design is classed as a Warship for auto-assignment purposes


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Fletcher II class Corvette      6,688 tons       239 Crew       1,858.1 BP       TCS 134    TH 1,403    EM 0
10486 km/s      Armour 4-31       Shields 0-0       HTK 52      Sensors 0/0/0/0      DCR 11-16      PPV 54
Maint Life 1.27 Years     MSP 360    AFR 238%    IFR 3.3%    1YR 234    5YR 3,504    Max Repair 243.3 MSP
Magazine 264 / 0   
Commander    Control Rating 1   BRG   
Intended Deployment Time: 3 months    Morale Check Required   

Inertial Fusion Drive  EP467.50 (3)    Power 1402.5    Fuel Use 311.46%    Signature 467.5    Explosion 22%
Fuel Capacity 430,000 Litres    Range 3.7 billion km (4 days at full power)

37.50cm C8 Far Ultraviolet Laser (1)    Range 320,000km     TS: 10,486 km/s     Power 37-8     RM 50,000 km    ROF 25       
CIWS-200 (1x8)    Range 1000 km     TS: 20,000 km/s     ROF 5       
Beam Fire Control R320-TS10000 (SW) (1)     Max Range: 320,000 km   TS: 10,000 km/s    ECCM-2     97 94 91 88 84 81 78 75 72 69
Tokamak Fusion Reactor R8 (1)     Total Power Output 8    Exp 5%

Size 14 Missile Launcher (50.0% Reduction) (6)     Missile Size: 14    Rate of Fire 300
Missile Fire Control FC45-R20 (1)     Range 45.8m km    Resolution 20   ECCM-2
Asp Anti-Ship Missile Mk3 (18)    Speed: 46,257 km/s    End: 20.4m     Range: 56.7m km    WH: 50    Size: 14    TH: 154/92/46

Active Search Sensor AS45-R20 (1)     GPS 2240     Range 45.8m km    Resolution 20

Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s

This design is classed as a Military Vessel for maintenance purposes
This design is classed as a Warship for auto-assignment purposes
There are definitely some improvements I could make, but this is a bit of a learning process, so I'd like feedback on what the best improvements might be.   They have been pretty effective in their role so far, but one can always get better.

Meanwhile, in preperation for extending my reach outside the solar system, I've designed some larger, higher endurance ships to protect me outside my home system.

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Arleigh Burke class Area Defence Cruiser      19,990 tons       679 Crew       6,678.3 BP       TCS 400    TH 3,341    EM 2,550
8357 km/s      Armour 8-65       Shields 85-510       HTK 135      Sensors 0/0/0/0      DCR 30-15      PPV 121.12
Maint Life 2.90 Years     MSP 4,088    AFR 320%    IFR 4.4%    1YR 716    5YR 10,736    Max Repair 556.875 MSP
Captain    Control Rating 4   BRG   AUX   ENG   CIC   
Intended Deployment Time: 12 months    Morale Check Required   

Inertial Fusion Drive  EP1113.75 (3)    Power 3341.2    Fuel Use 46.63%    Signature 1113.75    Explosion 13%
Fuel Capacity 1,570,000 Litres    Range 30.3 billion km (41 days at full power)
Epsilon S85 / R510 Shields (1)     Recharge Time 510 seconds (0.2 per second)

37.50cm C8 Far Ultraviolet Laser (1)    Range 320,000km     TS: 8,357 km/s     Power 37-8     RM 50,000 km    ROF 25       
25.0cm C8 Far Ultraviolet Laser (8)    Range 320,000km     TS: 8,357 km/s     Power 16-8     RM 50,000 km    ROF 10       
Single 15.0cm C8 Far Ultraviolet Laser Turret (4x1)    Range 300,000km     TS: 15000 km/s     Power 6-8     RM 50,000 km    ROF 5       
Single 10cm C2 Far Ultraviolet Laser Turret (8x1)    Range 150,000km     TS: 15000 km/s     Power 3-2     RM 50,000 km    ROF 10       
CIWS-200 (2x8)    Range 1000 km     TS: 20,000 km/s     ROF 5       
Beam Fire Control R280-TS15000 (2)     Max Range: 280,000 km   TS: 15,000 km/s    ECCM-2     96 93 89 86 82 79 75 71 68 64
Beam Fire Control R320-TS8000 (1)     Max Range: 320,000 km   TS: 8,000 km/s    ECCM-2     97 94 91 88 84 81 78 75 72 69
Inertial Confinement Fusion Reactor R120 (1)     Total Power Output 120.3    Exp 5%

Active Search Sensor AS8-R1 (1)     GPS 28     Range 8.4m km    MCR 760k km    Resolution 1
Active Search Sensor AS57-R40 (1)     GPS 4480     Range 57.8m km    Resolution 40

This design is classed as a Military Vessel for maintenance purposes
This design is classed as a Warship for auto-assignment purposes


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Alger class Escort Carrier      19,865 tons       313 Crew       3,432.7 BP       TCS 397    TH 2,775    EM 0
6984 km/s      Armour 3-65       Shields 0-0       HTK 97      Sensors 0/0/0/0      DCR 10-5      PPV 0
Maint Life 5.79 Years     MSP 11,080    AFR 316%    IFR 4.4%    1YR 562    5YR 8,429    Max Repair 462.5 MSP
Hangar Deck Capacity 4,000 tons     Magazine 1,080 / 0   
Captain    Control Rating 4   BRG   AUX   ENG   PFC   
Intended Deployment Time: 36 months    Flight Crew Berths 80    Morale Check Required   

Inertial Fusion Drive  EP925.00 (3)    Power 2775    Fuel Use 20.80%    Signature 925    Explosion 10%
Fuel Capacity 2,000,000 Litres    Range 87.1 billion km (144 days at full power)

CIWS-200 (2x8)    Range 1000 km     TS: 20,000 km/s     ROF 5       
Stinger Anti-Ship Missile (540)    Speed: 53,200 km/s    End: 0.4m     Range: 1.2m km    WH: 10    Size: 2    TH: 177/106/53

Active Search Sensor AS8-R1 (1)     GPS 28     Range 8.4m km    MCR 760k km    Resolution 1
Active Search Sensor AS72-R20 (1)     GPS 5600     Range 72.5m km    Resolution 20

Strike Group
2x Iowa Fast Attack Craft   Speed: 12000 km/s    Size: 20
10x Tennessee Fighter-bomber   Speed: 13524 km/s    Size: 3.99

Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s

This design is classed as a Military Vessel for maintenance purposes
This design is classed as a Carrier for auto-assignment purposes

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Iowa class Fast Attack Craft      1,000 tons       10 Crew       519.8 BP       TCS 20    TH 240    EM 0
12000 km/s      Armour 1-8       Shields 0-0       HTK 9      Sensors 0/0/0/0      DCR 0-0      PPV 12
Maint Life 0 Years     MSP 0    AFR 199%    IFR 2.8%    1YR 272    5YR 4,080    Max Repair 243.3 MSP
Lieutenant Commander    Control Rating 1   
Intended Deployment Time: 0.6 days    Morale Check Required   

Inertial Fusion Drive  EP120.00 (2)    Power 240    Fuel Use 1558.85%    Signature 120    Explosion 30%
Fuel Capacity 35,800 Litres    Range 0.41 billion km (9 hours at full power)

37.50cm C8 Far Ultraviolet Laser (1)    Range 320,000km     TS: 12,000 km/s     Power 37-8     RM 50,000 km    ROF 25       
Beam Fire Control R320-TS12000 (SW) (1)     Max Range: 320,000 km   TS: 12,000 km/s    ECCM-2     97 94 91 88 84 81 78 75 72 69
Inertial Confinement Fusion Reactor R8-PB40 (1)     Total Power Output 8    Exp 20%

Active Search Sensor AS7-R20 (1)     GPS 56     Range 7.2m km    Resolution 20

This design is classed as a Military Vessel for maintenance purposes
This design is classed as a FAC for auto-assignment purposes


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Tennessee class Fighter-bomber      200 tons       1 Crew       47.3 BP       TCS 4    TH 54    EM 0
13524 km/s      Armour 1-3       Shields 0-0       HTK 1      Sensors 0/0/0/0      DCR 0-0      PPV 2.4
Maint Life 5.06 Years     MSP 25    AFR 40%    IFR 0.6%    1YR 2    5YR 24    Max Repair 27 MSP
Magazine 16 / 0   
Lieutenant Commander    Control Rating 1   
Intended Deployment Time: 3 days    Morale Check Required   

Inertial Fusion Drive  EP54.00 (1)    Power 54    Fuel Use 1694.04%    Signature 54    Explosion 27%
Fuel Capacity 10,000 Litres    Range 0.53 billion km (10 hours at full power)

Size 2.0 Box Launcher (8)     Missile Size: 2    Hangar Reload 70 minutes    MF Reload 11 hours
Missile Fire Control FC9-R20 (2)     Range 9.5m km    Resolution 20
Stinger Anti-Ship Missile (8)    Speed: 53,200 km/s    End: 0.4m     Range: 1.2m km    WH: 10    Size: 2    TH: 177/106/53

Active Search Sensor AS7-R20 (1)     GPS 56     Range 7.2m km    Resolution 20

Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s

This design is classed as a Fighter for production, combat and planetary interaction
This design is classed as a Fighter for auto-assignment purposes


[nuclearslurpee]

In general, it is difficult to assess a fleet without some sense of the overall doctrine behind it. As such my comments will be mostly limited to technical details:

General comment on propulsion: I notice that for your large ships you are adhering very closely to a 3:1 engines-to-fuel ratio. While it is true that this ratio gives the smallest tonnage of engines + fuel for a given speed and range, this does not mean that a 3:1 ratio is strictly optimal. The cost of engines is usually* fixed by the speed and size of the ship only since the cost is based on the net engine power. However, the fuel requirement is not fixed and depends on the efficiency of the engine. If the "optimum" is, say, three size-40 engines with 125% boost and 40 HS (2,000,000 L) of fuel, you can achieve the same speed and range with three size-50 engines with 100% boost and 23 HS (1,150,000 L) of fuel. This requires a slightly larger propulsion section (160 vs. 173 HS) but conserves significant fuel in exchange for having somewhat less tonnage available for other capabilities. Note that the build cost of a ship with the latter propulsion section (assuming the total ship size stays the same) is somewhat cheaper as well, since the engines cost the same but make up a larger proportion of the ship, so you do recoup some of the lost tonnage efficiency by building additional ships for the same total cost. The point is that there is no singular always-optimal rule for designing propulsion, but in many cases a larger ratio of engine mass can bring important strategic benefits even if the resulting ships are not as capable on a per-ton basis individually.

*For engine power modifiers of 1.0x or greater. Smaller values confer an additional cost reduction which can make reduced-power engines (say, 80% or 90% power) highly efficient for some purposes.

Additionally, you could save significant minerals by asking yourself if your ships really need to be that fast. If the enemy you are fighting has a speed of 6,000 km/s, do you really need to fly at 8,000 km/s let alone 10,000 km/s? 6,500 or 7,000 km/s, for example, would be sufficient to guarantee an interception with good positioning, and would also guarantee that you can pursue the target either to its destruction or until it exits the system. There is, of course, something to be said for future-proofing in case the enemy improves his own engines, and it is also true that you need more than a minimal speed advantage for practical cases (6,001 km/s vs 6,000 km/s is a speed advantage, but not a very useful one, to give an extreme example). However, the point here is simply that more speed is not always the best use of your tonnage and minerals, particularly when the design specification is for a large number of cheap ships that can defend the spacelanes of a large interstellar polity.

Enterprise class: Note that you have a RES-20 MFC but a RES-40 active sensor. In this case it is "fine" because you will not have any problems spotting targets due to the much shorter range of the MFC, but it is a waste of tonnage and uridium when a RES-20 sensor one-tenth the size would do the same job.

Also, note that active sensors use the same EM strength tech as the passive EM sensors, so make sure you are researching that tech line as it would benefit your active sensors tremendously.

I don't much like the choice of reduced-size missile launchers here. Usually with missile launchers, the best choices are 100% size for rapid fire (best for AMMs and anti-fighter/FAC missiles) or 30% for maximum salvo size while keeping some reloading capability (usually for ASMs if not using box launchers). The intermediate sizes do have their uses but these are quite specific, generally if you are going to use something like 75% or 50% reduction you should have an express reason to do so. For the specific NPR you're fighting, I don't see much value in rapid-fire capabilities so 30% launchers would be the way to go IMO. You might also consider box launchers if you can count on reloading at a planet with maintenance facilities between engagements, since you shouldn't need a lot of endurance for this kind of fight. That way if you need a bigger salvo size against specific targets you can have it.

The use of CIWS here seems wasteful to me, for two reasons. One is that your NPR opponent is not using ASMs, so you do not need to spend tonnage and minerals for anti-missile defenses unless you intend to use these ships for some other mission (in which case you should say as much). The other is that CIWS only protects the ship it is on, which means it is primarily useful as the innermost layer of point defense on larger ships that will form parts of a fleet. In this case, the fleet provides PD by AMMs, beam PD, etc. and the CIWS exists as a last resort against occasional leakers. CIWS on single ships meant to operate alone is usually a waste, because any effective missile attack will overwhelm a single CIWS emplacement in any case.

Fletcher class: In addition to the above comments, where applicable, I note that a size-14 missile is probably excessive, and using twice as many size-7 missiles will probably do the job. This simplifies your ordnance logistics and also means you will lose proportionally fewer tons of missiles to point defense.

I might suggest including passive sensors in this design, they can be small and cheap but having some way to detect a NPR ship sneaking around your space is always useful for this kind of work.

Arleigh Burke class: This looks fine for the most part, I'm not personally a fan of laser PD and mixed turret calibers but with the 2.2+ changes to missiles it makes sense. The turrets do seem a little bit slow, 15,000 km/s tracking speed is an odd choice as you usually want to use 4x the racial tech level for PD turrets. Again, I recommend passive sensors on this or the Alger class, it is not wise to send a fleet into a war zone without passive detection capability.

I notice that this class is significantly faster than the Alger class. This is not a problem if you intend the Arleigh Burkes to operate on their own, but if they are meant as carrier escorts then you probably don't need that much speed. I'd probably use lower-boost engines here to conserve fuel, since flying military fleets around is a great way to drain your fuel reserves suddenly and unexpectedly.

Alger class: It is okay. The 4,000 tons of hangar space seems a bit light for a 20,000 ton carrier. I think you could get more space, and thus more striking power, if you reduced the magazine space somewhat. You do need enough reloads for a few bomber strikes, but after a certain point you should consider reloading from a collier if a sustained offensive is necessary.

For the fighters and FACs, you might consider reducing the engine boosting a bit to gain more fuel efficiency/range as the range you have right now is a bit short. I would also recommend bumping up the sensor range a bit to better match your MFCs on the fighters - doubling the sensor size from 5 to 10 tons will do the job nicely.

[BardicNerd (OP)]

Thanks for the comments -- definitely a decent bit of stuff I hadn't thought about there.   

You are quite correct that I had focused primarily on having engines that are optimal in terms of space without thinking about potential cost or fuel efficiency.     At the moment, fuel supplies are not particularly a concern, though once the bigger ships come into operation, this is not likely to remain the case.     I will want to think about this for the future, though ultimately the answer is to simply increase fuel production (though eventually of course there is a limit to how much I can do that, in this game Sorium will not be a concern for a very long time, but pops to operate the refineries will be).     But it would be wise not to be needlessly wasteful, and in any case I don't want to develop bad habits for future games.   

I don't know if I need to be quite that fast, but I have found it useful.     The enemy ships tend to run as soon as they detect my warships (at least, I assume this is what is making them turn around), and I found that even above 7k km/s I would struggle to intercept them before they got out of my planetary detection range -- I could chase them off, but it was a constant game of cat and mouse that I didn't find very fun.     I've since increased Earth's detection range quite a bit, so that has helped (and I've newly improved the sensors on the ships, so they can get in their own sensor range quicker), still I think I really do want a speed of 8k km/s or so.     The Fletcher is specifically intended to be extra-fast, but it could probably be reduced to only 9k km/s.   

The choice of the RES-40 active sensor and the RES-20 MFC is due to the fact that the fleets I face usually include at least one ship sized optimally for that active sensor, but mostly ships sized optimally for the MFC.     So this helps me keep track of the fleet at a greater range, though at a cost of efficiency.     It would probably be better to simply field a separate dedicated sensor vessel, though.     I tend to prefer this approach for overall doctrine, though, even if it's ultimately less efficient.   

I have definitely not put as much priority into researching passive sensor techs as I really should.   

You are probably correct about the reduced size missile launchers, and definitely correct about the CIWS being a waste.     I'll be making changes to those for the next generation.   

It probably would be better to switch the Fletchers to using Kestrels for their missiles, though the Asps are proportionally cheaper, so there are some tradeoffs.     The range of the Asps is probably not as important for this particular use.   

Given the tech level my passives are at, I don't think the Fletchers would really benefit from having passive sensors on them -- they're designed as low-endurance, quick-intercept ships that operate from a major base that would have large passive senor coverage of its own, so they'd rarely get to use them, on the occasions when they do end up chasing their target outside that sensor range, I generally expect their active sensors to outrange most sensibly sized passives I could currently put on them -- particularly as their targets do use thermal sig reduction, so don't actually have very strong signatures to detect.   

I don't recall why I choose that tracking speed.     It is certainly not optimal.     I choose to research lasers at the start and haven't put much into other beam weapons, so I've defaulted to lasers for PD .    .    .    though even at the tech levels I have, gauss would be a better choice, I think.     I'm not sure about railguns, given that they can't be turreted, but they would output a lot more shots.     Conceptually, I like having a dual-purpose battery that can be used both against missiles and against small ships, but I might change my mind about it once I see it in action, so we'll see.   

Not sure why I didn't put passives on the bigger ships, it may have been an oversight, or I may have had a reason that I'm not recalling.     I suspect it's because my active tech is better than my passive tech, and I looked at ranges and decided it was better to have a larger active than a passive that didn't see that far.    EDIT: I did some calculations, and for the particular set of parameters I'm looking at -- 279 strength heat signatures on a 1k ton active signature or 558 strength heat signatures on a 2k ton active signature -- actives will always outrange passives of equal tech and size.    I might be wrong, though.   EDIT AGAIN: The formulas I found were incorrect, at my tech level actives are better for this use, but that may not always be the case.   Passives are probably not going to be very much better than actives for this particular detection, though, and since I'll always want an active, it makes sense to just use actives rather than both an active an a passive.

The Arleigh Burke isn't really intended to escort the Alger, though I have considered it.     I may design future generation with that in mind, I'm not sure.     I'd also want to harmonize their deployment time if I do that.   

I would definitely like to have more hanger space on the Alger class.     I may have given it more ordinance storage than needed, I'm not really sure where the correct balance lies yet.     I'm not very experienced in managing a logistics train yet, though, so I think erring on the side of easier logistics until then might be the better option.   

There were some compromises involved in the fighter and FAC design, and it's entirely likely I didn't get the balance right.   

Thank you again for your feedback, it is very helpful.