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Post by airc777 on Oct 13, 2018 18:04:55 GMT
I'm trying to build a 1 gw ship that only uses lasers. I've tried a number of different custom lasers, but I can't seem to build one that's actually more effective then the stock 100 mw laser. The current most effective ship I have uses ten of the 100 mw lasers driving forty turrets. It deletes drones and missiles with hilarious efficiency, but it's not particularity good at killing ships. (At least not when comparing the time-to-kill of the Vesta Overkill fleet with three of these laser ships versus one 1 gw ship armed with forty custom 100 mw railguns.) Improvements I've made to the stock design have been incremental and small, like raising the radiator temperature or lightening the turrets. Custom lasers I've attempted to make have always had far higher time-to-kills on missile and drone fleets, let alone the Vesta capital fleet, regardless of power input or intensity at range. Is there a guide on building lasers that I'm not currently aware of?
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Post by vegemeister on Oct 13, 2018 20:07:51 GMT
All lasers should be unmounted, because it reduces the crew requirement (which competes with the radiators for heaviest part of a laser system), and because the optimal shape for the laser cavity is long and thin -- much longer than the width of reasonable turrets. (Although short cavities don't hurt efficiency *that* much.)
The best (non-modded) lasers are Nd:YAG with Krypton gas lamps. Ti:Saph with Xenon is sometimes used, but the greater efficiency of Nd:YAG allows a wider beam at the same intensity, which is good for small targets. There are also more temperature options with Nd:YAG: Cavity Wall/Mirror
| Output Coupler
| Radiator Temp
| Approx Eff.
| Silver
| Fused Quartz
| 1173 K
| 4.34 %
| | Gold | Fused Quartz
| 1270 K | 4.10 %
| | Copper | Fused Quartz | 1290 K
| 3.96 %
| Molybdenum
| Fused Quartz | 1841 K
| 2.16 %
| | Molybdenum | Diamond
| 2131 K
| 1.91 %
|
I like copper at 1290 K. For large aperture lasers, the mirror material (*not* the "focusing mirror" material) affects the weight of the laser. I think that's why apophys uses copper for that and gold for the cavity wall at 1270 K. If you want to use Ti:Saph, gold and copper are no good. Arc lamp envelope is always diamond (strong and transparent), and coolant is always hydrogen (low density and transparent). Lasers should always be frequency-quadrupled, unless you don't care at all about turret size and want to squeeze out that last bit of efficiency with a silver primary mirror. The cavity should be very nearly round.
Efficiency is somewhat improved by reducing power density in the arc lamp gas, which shifts its power into the longer wavelengths. Increasing the radius of the lamp greatly reduces Cavity Shape efficiency, which must be counteracted by increasing the cavity radius (a lot), which requires re-tuning and bloats weight. So it is better to use the minimum lamp radius and make the cavity very long ("Optical Nodes"). This is a small effect at reasonably high powers, however, so if you want to make short lasers (perhaps directly attached to turrets), you don't lose much.
The takeaway from the ablation cap is that aramid and polyethylene are the best armor against high-intensity lasers. but if you're facing low-intensity lasers tuned against them, the best choice is amorphous carbon. The crossover intensity is 17.4 MW/m^2 for aramid, and 38.8 MW/m^2 for polyethylene. This means missiles should have an outer crust of amorphous carbon, and AC is also preferred for laser turret armor if you expect laser dueling. Furthermore, lots of low-power lasers are better than one high-power laser.
An interesting consideration for dueling, is that if you define survival_time * intensity_at_target as a figure of merit for laser turrets, it works out to be proportional to the mass of the turret and only the mass of the turret, under the assumptions that 1) the armor is thin enough to treat as locally flat, and 2) the mirror is large enough that all of your laser energy lands on the enemy's turret (no overspray). This is because the area of the armor and the area of the mirror are both proportional to the area of the turret.
That means you can put thick AC armor on your wide beam point defense lasers, and they are perfectly adequate for dueling laserstars -- or at least keeping them occupied long enough for your kinetics to hit. The laserstar will probably still win a lasers-only duel, given that they put all of their reactor power into lasers and you're probably using some of yours elsewhere.
If you want to kill the enemy's turrets quickly (important for kinetics), not just win laser duels, you need big apertures. But laser wobble makes big aperatures largely useless against small missiles. Here's a table relating aperture size to beam radius at 1000 km, for frequency-quadrupled Nd:YAG lasers: 1000 km Waist
| Aperture
| 30 cm
| 1.78 m
| 50 cm
| 1.07 m
| 1.0 m
| 53.5 cm
| 1.5 m
| 35.6 cm
| 2.0 m
| 26.7 cm
|
High time-to-kill is pretty much unavoidable, assuming the enemy has remotely effective armor. But the hope is that that you can lase off the enemy's guns from outside their effective range and dodge/tank any bullets they managed to get off before the guns were destroyed. Then slowly drift in and burn off their radiators over the course of minutes. |
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Post by airc777 on Oct 14, 2018 0:18:04 GMT
Well now I can make them really light and that's great, but I kinda just wanted to make them burn a better hole. Craft this is going on weighs 1.5k, this thing weighing 20 ton instead of 700 kg isn't gonna hurt anything. My output power hasn't really trended up, how are you getting 4.34% efficiency?
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Post by airc777 on Oct 14, 2018 1:37:19 GMT
Nope, still don't get it. Can not with an aperture of any size other then very small make my fleet kill the Vesta fleet faster then they can kill me. I'm just not seeing the in mission performance increase that stats suggest I should be getting.
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Post by vegemeister on Oct 14, 2018 1:50:28 GMT
You have to type in the "Cavity Semiminor Axis" parameter instead of clicking the buttons, which can't get close enough to circular. You're trying to maximize "Cavity Shape" efficiency, which is affected by cavity shape (obviously; set the semimajor axis then approach from below with the semiminor axis), and by the radii of the lamp (leave it at the minimum) and the lasing rod (tweak as necessary). With proper tweaking, you can get it fairly close to 100%. All of the other components of efficiency are either entirely dependent on material choices, or can be adjusted independently. While you're tweaking, crank up the turbopump to avoid temperature errors.
After you've got the cavity shape and lasing rod radius correct, you can increase optical nodes either until M^2 = 3.00 (for short/light lasers), or until you get worried that the laser is too long or heavy to fit in the ship (for a small increase in pumping efficiency).
Then, add each frequency doubler. Increase the optic radius until the error goes away, and then tweak the length to get as close as possible to 100% efficiency (the sweet spot is pretty wide).
Finally, tweak the aperture size to taste. It controls the size of the laser spot at the target. Big aperture -> small laser spot/high intensity. But, like I said in the other post, lasers have wobble, and if you go much bigger than 50 cm aperture, the laser won't be able to hit extremely small targets at long range.
Here's an example of a 4.34% efficient laser:
(Ignore the outlet temperature and turbopump parameters. It's modified from a 1290 K laser for this post.)
Edit: very small values of Optical Nodes will reduce cavity shape efficiency somewhat, so if you start with a clean sheet design you may be frustrated by that. Also, if you change the power of a laser, the only parts that really have to be re-tuned are the frequency doublers and the turbopump.
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Post by smithblack on Oct 14, 2018 1:52:26 GMT
You are getting way less power out of that tube than you should be at 1173 K. Can I see either a design screen or an export?
Also, and of critical importance, how big is the laser aperature?
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Post by airc777 on Oct 14, 2018 5:34:12 GMT
Ok, this one preformed far better in combat, and I've achieved 3.99% efficiency. I think part of it was it just did not occur to me to start with the arc lamp radius at 1 mm. Currently using 60 cm aperture radius so I can have a lot of redundant turrets without heavily increasing the crafts mass. It ate missiles pretty good, didn't do to bad against the Vesta fleet either.
Is it worth it to have two sets of lasers on the same ship, one with a small aperture set to only target shots and one with a much larger aperture set to target ships?
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Post by jtyotjotjipaefvj on Oct 14, 2018 14:21:28 GMT
Ok, this one preformed far better in combat, and I've achieved 3.99% efficiency. I think part of it was it just did not occur to me to start with the arc lamp radius at 1 mm. Currently using 60 cm aperture radius so I can have a lot of redundant turrets without heavily increasing the crafts mass. It ate missiles pretty good, didn't do to bad against the Vesta fleet either.
Is it worth it to have two sets of lasers on the same ship, one with a small aperture set to only target shots and one with a much larger aperture set to target ships?
Looks like your range is set to 35 km? You can crank it up to 400 without any worries with that intensity, maybe even the full 1000 km. I've thought about having separate lasers for PD and anti-ship duty as well, but never got around to testing it properly. I'm fairly sure it would benefit you though, so go ahead and give it a try. |
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Post by airc777 on Oct 14, 2018 17:51:00 GMT
Tried 400 k engagement range, AI ignores maximum range and lags the game to where I walk away from it and come back when it's done. 90 k engagement range seems to be the sweet spot, frame rate holds steady and I can micro manage the ships around, causes the loss of fewer turrets on my ships.
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Post by airc777 on May 18, 2019 3:55:29 GMT
Ok. Currently trying to figure out how to make very high input powered lasers present a broader beam to target. Idea being if I have the energy to meet the target ablation cap then a broader laser covering the same area continuously will bore a hole faster then a pin point laser dancing all over the target. Probably not worth the mass, but I thought I'd double check my assumptions.
What does Laser Module, Arc Lamp, Radius variable do?
What does 'M^2 (Beam Quality Factor) is too high to be reasonably effective' mean?
I was building progressively higher powered laser systems and when I got up into tens of GW input my focusing mirrors could not withstand the entry intensity with aperture sizes at or below 0.5 meters, my lasers then proceeded to lose effect on target due to laser wobble. I'm currently exploring other avenues of gaining efficiency then just bigger apertures, as I already have plenty of PW/M^2 at desired engagement range, but I still want bigger laserstars because I can.
I have an exactly stock solarlance massed ship that bests the solarlance in every catagory and it's using a single 50GW input laser making 750MW/M^2@1,000km with a 58cm aperture and 1 meter of nitrile rubber turret armor and that's cool and all, but that's well under the mass budget of Vesta Overkill and The Fall of Titan and I want more laserstar. More the same 50GW lasers on one hull is fine, but 100GW is just a nice round number.
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Post by tepidbread on May 19, 2019 1:26:46 GMT
Ok. Currently trying to figure out how to make very high input powered lasers present a broader beam to target. Idea being if I have the energy to meet the target ablation cap then a broader laser covering the same area continuously will bore a hole faster then a pin point laser dancing all over the target. Probably not worth the mass, but I thought I'd double check my assumptions.
The game currently models all laser damage as a single point. To simulate beam waist, the point that is being damaged is varied in a Gaussian distribution.
Simply put the beam is to wide to do any damage.
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Post by airc777 on May 19, 2019 2:17:36 GMT
Ok. Currently trying to figure out how to make very high input powered lasers present a broader beam to target. Idea being if I have the energy to meet the target ablation cap then a broader laser covering the same area continuously will bore a hole faster then a pin point laser dancing all over the target. Probably not worth the mass, but I thought I'd double check my assumptions.
The game currently models all laser damage as a single point. To simulate beam waist, the point that is being damaged is varied in a Gaussian distribution.
Well that sucks.
Simply put the beam is to wide to do any damage.
But I'm getting that message with a beam that's still producing two gigawatt at one megameter, so I know that's just the 'lies we tell to children' version. What's actually happening?
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Post by bigbombr on May 20, 2019 14:41:25 GMT
Beam quality factor essentially tells you how far away your beam is from a diffraction-limited laser beam. You want an M² as low as possible. In the game, this is limited to 3 IIRC, but IRL lasers with a beam quality factor approaching 1 exist AFAIK.
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