Many weak lasers outdoing one powerful one - correct physics?

[cantab314]

So I have a 10 GW laser armoured with 100 cm of aramid. It takes it over ten minutes to destroy another one of itself. Then I made a 1 GW version, same size mirror so 10% power and intensity, and put seven of those on a ship, and they're able to destroy the 10 GW laser in about a minute and a half. Despite the weak lasers having *less* combined power and efficiency!

And there's a player on the subreddit whose made drones with 20 100 MW lasers, and then sends them in groups of say 10-30 drones, and they absolutely shred the enemy fleets, even though again their aggregate power is only about the same as a single 10 GW one.

What's going on here? Is this correct physics, and if so what's doing it? Or is there a flaw in the game?

[unwinged]

Lasers are rated by input power. What is output power of big and small lasers?

[cantab314]

440 and 44 MW respectively on mine, and at 1000 km it's about 1100 and 110 MW/m^2 intensity. JasonVance's (on the reddit) are 3 MW and 110 MW/m^2. Regardless, the absolute numbers don't really matter, it's the relative performance that I find surprising.

The forum mentions that there do indeed seem to be some issues with how laser damage is simulated: http://childrenofadeadearth.boards.net/thread/484/guide-defeat-laser-lowest-cost?page=9

Based on what I've seen, if the many-laser behaviour is correct then lasers might well be dominant. (And even more so if the big lasers require a buff). The range and power, on a per-ton or per-credit basis, of a couple hundred long-range lasers is like almost nothing else I've seen or heard of; large missile swarms might stand a chance. If on the other hand the multiple lasers are overperforming then things should be more diverse. Not that this matters - CoaDE is supposed to do what's accurate, not what's fun gameplay.

[dragonkid11]

The single powerful laser can focus all its energy into a single point.

However, you can only vapourise or melt a material so quickly as the vapour will refract the laser or the material is radiating heat away and causing the laser to be less efficient.

Where if you have multiple laser, you get to target different area of the ships and thus the laser points will be different, allowing you to melt more material for the enegy cost.

Obviously, the draw back is that you have more laser, so you have more weight, and bigger ships needed to carry them.

[cantab314]

"Where if you have multiple laser, you get to target different area of the ships and thus the laser points will be different, allowing you to melt more material for the enegy cost."

Except that in this case they're all targeting the *same* spot. Where they strike the target the beams almost entirely overlap; the 1000 km range makes the difference in angle from lasers on one ship miniscule. (And I suppose I could test with a less focussed beam to double-check). And if they weren't overlapping, I'd have thought that drilling seven separate holes wouldn't help much when all you really need is for one to penetrate fully.

I wonder if the game is simply omitting to consider the effects of ablation by one laser on the other laser beams?

[Gryphon]

It is possible, under certain conditions, for many small beams to out-perform a single powerful beam of equivalent power.

https://www.rp-photonics.com/beam_combining.html

[DeciNinja]

I think it's a beam divergence problem. A well focused beam is indicated by a low M2 factor, but the M2 factor tends to be be higher in more powerful lasers, due to thermal lensing in the lasing rod and some interesting nonlinear effects, which can be offset by increasing the size of the lasing rod and aperature, often to huge proportions. Because of that, I think putting less power into the same laser also decreased its beam divergence, improving its intensity at range.

[cantab314]

Gryphon, that page though seems to be talking about combining multiple laser sources into one beam, and is more about efficiency and scalability than effect on any target. In CoaDE I am using multiple separate beams, each of which is built using a game mechanic that scales well, to aim at a single target point.

DecidedlyNinja, I can rule that out too. My beam qualities are consistently close to 3 which is the best achievable, and anyway I checked intensities at the engagement range of 1000 km. After all I built the 10 GW laser first then downpowered it. When doing that all that's needed is to slow down the coolant turbopump to keep the radiators running nice and hot, and tweak the frequency doubler length to fix its efficiency. (As far as practical laser design goes, yes a multi-gigawatt laser needs a big lasing rod, but if you're building for 1000 km range the turret to hold the big aperture dominates the mass and cost anyway).