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Post by pocok5 on Nov 17, 2016 21:36:40 GMT
Unlike most modules where I could get a decent grasp of things by observing some stock designs, making a decent laser above 0.1% efficiency continues to be a problem for me. Since there are basically no module design tutorials outside the rather sparse game info, it would be nice if you laser-savvy guys could write down some useful info about making effective laser systems for me and others.
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Post by teeth on Nov 17, 2016 21:52:27 GMT
The lasing medium and gas in the chamber is one of the most important things, for a low powered laser (Less than 100 or so megawatts) use ND:YAG with krypton as the gas composition. For mid to high powered (100 megawatts to 1 gigawatt) lasers use Titanium:Sapphire with Xenon, and for the highest powered lasers use Ruby and Xenon, but you can also use Titanium:Sapphire for that if you prefer efficiency over the higher frequency. Additionally, always use a frequency doubler. It halves the output power but also halves the wavelength, making the beam diffuse less. I usually use lithium niobate, increase the length until it can handle the output power then increase the radius until it reaches 99.9% efficiency.
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Post by apophys on Nov 18, 2016 0:12:13 GMT
Alright then...
You have effectively 2 choices for your laser medium: green (Nd:YAG + krypton) or purple (Ti:Sapphire + xenon). Green is more raw power (higher efficiency), but requires larger apertures to make up for its lesser intensity (green is lower frequency than purple). Purple has somewhat improved efficiency at low power, but still not more than green.
Green gets its best pumping when arc lamp radius is small. Purple gets its best pumping when arc lamp radius is large. This makes purple slightly more expensive when optimized, in my experience. (Most of your cost will be turret armor.)
Increasing lamp radius requires also increasing lasing rod radius, which worsens M2. Higher power input also worsens M2, but increases intensity. You want M2 to be 3.00-3.02 or else your intensity at range takes a hit. For these reasons, I recommend purple for low power (<100MW) and green for high power (>100MW, arbitrary cutoff by me). Exactly the opposite of the above recommendation...
Hydrogen or hydrogen deuteride are the only coolants that really make sense, because it doesn't need to work very hard and it must take a lot of space.
Cavity shape is best when it is as close to a circle as possible. Keep dimensions small; this saves a lot of mass (mostly as coolant) at a low efficiency cost.
Transparent parts are fused quartz.
Cavity wall and internal mirror are silver (standard) or copper (if you want to sacrifice efficiency to push your output temperature up for smaller radiators).
Use a frequency doubler for a greatly reduced aperture, and thus greatly reduced weight & cross-section. It is strongly recommended but not essential; you can choose to take the cost of a large aperture if for some reason you really want a laser in the near infrared. Silver gallium selenide always gets you to 100% efficiency here, and it is the only one to do so. Its cost and weight are negligible. Therefore no other doubler is relevant.
Focusing mirror is aluminum (for purple) or silver (for green or near infrared).
The turret should be as small as possible to hold the aperture, due to reaction wheel mass being added.
Crank up engagement range to 1 Mm, because that's what lasers are for. If you're getting terrible intensity, increase the aperture. Aim for at least 1 or 100 MW / m2
Following these guidelines, you can get effective lasers in a few tons of weight. Or even in less than half a ton, as I have on a drone that I didn't release yet.
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Post by ironclad6 on Aug 8, 2017 10:12:56 GMT
Guys. I've absolutely struggled with this. I'm getting efficiency peaking at 4.39 percent with a beam intensity of 55.5 Me at 1000 KM. I've optimized my aperture and turret radius to minimize mass I'm inputting 110 Mw. I can't increase my power input any further and I can't raise my efficiency. I am running both frequency doublers with lithium niobate. My facility with the maths is utterly exhausted. I've discovered I can get a 50% power output increase by tripling my power input. This doesn't seem like a sensible trade at all to me. Am I simply using too small of a turret?
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Post by someusername6 on Aug 8, 2017 12:15:53 GMT
Guys. I've absolutely struggled with this. I'm getting efficiency peaking at 4.39 percent with a beam intensity of 55.5 Me at 1000 KM. I've optimized my aperture and turret radius to minimize mass I'm inputting 110 Mw. I can't increase my power input any further and I can't raise my efficiency. I am running both frequency doublers with lithium niobate. My facility with the maths is utterly exhausted. I've discovered I can get a 50% power output increase by tripling my power input. This doesn't seem like a sensible trade at all to me. Am I simply using too small of a turret? Efficiency sounds alright without mods, actually; sounds like you probably want more intensity though? Suggestions: - Post the laser design itself so we can take a look at the materials you are using. Might be able to eke out a few more fractions of a percent by changing materials here or there (e.g. see if you can get better efficiency by using silver gallium selenide as frequency doublers, I am usually able to get to 99.9% efficiency from them or more, not always with the others, but that depends on the laser frequency)
- You may need to change a number of properties based on power input -- you can probably triple your output power by tripling your input, but that means changing sliders everywhere again.
- Use a larger aperture radius. This doesn't impact efficiency, but it does impact intensity -- larger mirrors can focus the same laser beam into a smaller area, burning things faster (up to about 200 MW / m2 if I remember right; after that you want to use more lasers instead of a single larger laser at that range).
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Post by apophys on Aug 8, 2017 18:07:54 GMT
Things have changed a little in the 9 months since I wrote the instructions 3 posts above. Yay for necroposting! Nowadays we have a second frequency doubler available. Highly recommended to use both. This results in aluminum being the focusing mirror to use for both green and purple when frequency quadrupled. Gold is the preferred cavity wall if you use green, due to a higher safe temperature achievable than silver at very little efficiency loss. It would be paired with a copper Mirror. Not an option for purple, though. Envelope is diamond. Nothing else really survives the pressure. Silicon makes a nicely cheap turbopump material, as well as laser radiator material, at this temperature. Otherwise unchanged.
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Post by the_Demongod on Aug 8, 2017 20:53:47 GMT
Look at the list on the left to see where your efficiency is lacking. The lowest category should be "pumping," (mine usually are in the realm of 5% iirc), with the rest being above 80% ideally. Those categories tell you what to fix, e.g. "cavity shape", etc.
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Post by Enderminion on Aug 9, 2017 18:17:32 GMT
if you use mods Hoolium and Ruby lasers are 32-33% efficent
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Post by bigbombr on Aug 10, 2017 6:57:37 GMT
if you use mods Hoolium and Ruby lasers are 32-33% efficent Ce:LLF with gold can get 39%-41% efficient.
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Post by ironclad6 on Aug 18, 2017 6:13:56 GMT
Up to 52% efficiency on a 8.8 GW laser design. Thanks for all your help. Can anyone help with improving pumping efficiency? I'm at or near 100% for all other categories but can't beat ~54.4ish there.
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