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Post by gedzilla on Jun 20, 2019 9:22:47 GMT
So i Was wondering this. I looked at some other forums, and they said that the auther of the expanse said that they are not cost effective in-universe. This is becuase they are too easily countered, not powerful enough, and to complex. So much so that for PD, its more effective to mount a bunch of CIWS than a few big lasers. Same for medium ranges; railguns vs lasers. They seem to have concluded that laser ranges max out at 300km which seems really low to me. I think becuase of that, they are ignoring the main advantage of lasers: range. What do you think ? Are lasers feasible militarily in the expanse ?
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Post by airc777 on Jun 20, 2019 10:56:11 GMT
Well, do we have cannon numbers for velocity and accuracy and firing rate and projectile mass for their railguns? That would tell us both what the laser is competing against in terms of anti capital and how much power generation the laser would have to play with. In the Halo novels and Mass Effect lore the guns are monstrous compared to the guns modeled in CDE, but do we have hard numbers for the expanse?
There is one caveat that you would have to engineer lasers around in the Expanse that wouldn't be as big of a factor in real life. The ships in the Expanse are designed to accelerate at very high G forces, so the radiator area for the laser would have to be structurally sound and it can't just be a 1 kilometer square sheet of aluminum sponge foil with hydrogen circulating through nano tubes. Also, if the tens of kilotons crewed ships can sustain 10g for long enough to knock the crew unconscious and then fly out of the system then the missiles that your laser CIWS will be tracking will probably be hella fast.
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Post by AtomHeartDragon on Jun 20, 2019 16:35:44 GMT
There is also a meta-reason, I guess - laser battles are boring, so when wanting to create good fiction, when in doubt choose whatever nerfs the lasers.
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Post by dragon on Jun 20, 2019 21:09:51 GMT
Actually, 300km isn't a bad maximum range for a mid-tech laser. The kind of lasers people make in COADE would require multiple humongous, absolutely perfect crystals for both mirrors and laser's innards. With more reasonable apertures and laser sizes (still gigantic compared to what we can do today), your range plummets. Even in a high-tech setting, lasers are unlikely to be more efficient weapons than kinetics, or indeed, to exceed them in range, as far as practical weaponry goes.
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Post by cipherpunks on Jun 20, 2019 22:04:11 GMT
require multiple humongous There can be only one:
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Post by bigbombr on Jun 21, 2019 5:43:00 GMT
Actually, 300km isn't a bad maximum range for a mid-tech laser. The kind of lasers people make in COADE would require multiple humongous, absolutely perfect crystals for both mirrors and laser's innards. With more reasonable apertures and laser sizes (still gigantic compared to what we can do today), your range plummets. Even in a high-tech setting, lasers are unlikely to be more efficient weapons than kinetics, or indeed, to exceed them in range, as far as practical weaponry goes. You're completely ignoring the existence of gas dynamic lasers, glass fiber lassers and free electron lasers. All of those can scale up pretty well. The US has a program for scaling combat lasers up to 1 MW, with a target weight of less than 4 tons. They're going for fiber lasers AFAIK. As for large aperture sizes: so what is similar in size to existing telescopes is unreasonable, yet railguns with large capacitor banks aren't? IMO, unguided kinetics are extremely niche and outperformed by beam weaponry and missiles. Conventional cannons are likely close to useless. Ever tried to hit anything with unguided artillery beyond 60 km? Making munition with that kind of maximum range is trivial, yet tube artillery doesn't tend to use unguided munitions with that kind of range, because they can't hit anything at that range.
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Post by walterscientist on Jun 21, 2019 13:35:08 GMT
IMO CoaDE heavily shifts the weapon balance in favor of lasers. They have future level of performance while guns don't reach today performance. Hard to say how railguns and coilguns fare, but trying to reach performance of today guns will give you weapons 3x heavier than today, because of cylindrical barrels.
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Post by dragon on Jun 21, 2019 19:45:30 GMT
True, though I think it manifests the most with user-made lasers. COADE makes it far too easy, compared with the rest of the tech, to make giant, hot-running lasers, where the engineering challenge of making crystals and mirrors of that size would be rather nontrivial. Railguns can be taken to extremes as well, but it's much harder (as for coilguns, the model is completely broken). Chemguns aren't that bad, but then, they are never going to be the top dog. It is possible to recreate a WWII-era battleship gun, at least, though it's not very feasible to mount in a turret. Indeed, if anything can be called "inferior tech" in COADE, it's turret technology. You're completely ignoring the existence of gas dynamic lasers, glass fiber lassers and free electron lasers. All of those can scale up pretty well. The US has a program for scaling combat lasers up to 1 MW, with a target weight of less than 4 tons. They're going for fiber lasers AFAIK. A FEL is basically a particle accelerator that converts its output to X-rays using an undulator. Potentially effective, but at this point, you've got a perfectly serviceable particle cannon on board. Any FEL question can be answered with "the same reason they don't have particle cannons". Indeed, given that a FEL will typically only convert a fraction of the electrons' energy to X-rays, it would probably be preferable just to shoot electrons themselves at the enemy. FEL only makes sense as a weapon in atmosphere, which generally makes things difficult for electrons. As for the others, I suspect thermals would be the killer. I don't think they can run hot enough to end up with a reasonably sized radiator. Now, neither glass fiber nor gas dynamic lasers are a part of my expertise, so maybe there are way to make them run at >1000K, but I would expect that to be quite a challenge, too. Telescopes use multi-piece mirrors, with small gaps between them. I don't think you can have that with a laser, seeing as anything that isn't a mirror will absorb the enormous energy that the laser generates, and promptly cease to exist. You can actually overwhelm a mirror in COADE, if you make the energy density too large. Think of how well any non-mirror material would fare in those conditions. So I don't think anything but a monolithic mirror will work. Hitting things at 60km or more with arty is quite trivial, and in fact tube arty does use unguided shells for those (and greater) ranges. How do they do that? A simple, yet effective technique called "shoot a crapton of huge shells". One of them is gonna come close enough. The principle of more dakka reigns supreme both in COADE and IRL, as far as kinetics go. Conventional cannons are useless not because they're inaccurate, but because they're very dodgeable. In COADE, "effective range" is mostly dictated by rounds' time of flight. Spread matters little (as long as it isn't absurd), you just fill a volume of space with glowing-hot armature material of your choice, and hope that enough of it will stick. Of course, that means high-mass weapons are only good for orbital bombardment. They just don't fire fast enough nor fly fast enough to score any good hits. Frag and explosives can help, but it's easier to make a gun that shoots the "fragments" one at a time, at a high rate and high speed.
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Post by walterscientist on Jun 21, 2019 20:15:10 GMT
To put out specific numbers, it is possible to replicate WW2 40mm L/60 Bofors. These are the parameters I am going for based on data available on the internet:
- 40mm bore - 881m/s muzzle velocity - 900g round - 300g propellant - 2.35m barrel length - 120rpm rate of fire - 270MPa peak barrel pressure
In CoaDE I can build this: 4.9cm thick vanadium chromium steel barrel (can handle 120% of regular firing pressure, a real gun cannot be safely used if it goes to bursting pressure with every shot) 410kg weight
The real thing weighed 470kg - that seems more or less OK. The problem is that by all accounts the real gun was pretty overbuilt. Moving to the modernized Bofors L/70 - that weighs 670kg in CoaDE - that is definitely excessive and we are still only in early post-WW2 era. A replica of a single 30mm barrel for the GAU-8 cannon weighs 270kg while a real GAU-8 weights 281 kg whole - with 7 barrels (and housing assembly). That means one of its barrels cannot weigh more than 40kg - a factor of 7 difference! And GAU-8 is nowhere near cutting edge technology - it was developed in the seventies.
P.S. If anyone knows how to ,,benchmark‘‘ railguns and coilguns in similar way, please do tell.
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Post by bigbombr on Jun 22, 2019 15:05:19 GMT
IMO CoaDE heavily shifts the weapon balance in favor of lasers. They have future level of performance while guns don't reach today performance. Hard to say how railguns and coilguns fare, but trying to reach performance of today guns will give you weapons 3x heavier than today, because of cylindrical barrels. 1) CoaDE has higher operating temperatures and higher power to mass ratio but poorer efficiency and beam quality factor compared to IRL. Keep in mind that sensors and sensor burning isn't modeled either, nor are their pulsed lasers in CoaDE. 2) Multistage capacitor coilguns are broken and unusable in game. IRL they're pretty interesting but heavy. IRL railguns tend to have a higher efficiency but lower muzzle velocities. Multi-shot barrel erosion also isn't modeled. 3) Yes, IRL guns perform better relative to their mass, and most of that is IIRC because they use complex propellant mixtures/grain geometry and have barrels more complicated than a homogeneous tube. Keep in mind that the game doesn't take ammo handling/ammo belts into account.
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Post by bigbombr on Jun 22, 2019 15:19:35 GMT
A FEL is basically a particle accelerator that converts its output to X-rays using an undulator. Potentially effective, but at this point, you've got a perfectly serviceable particle cannon on board. Any FEL question can be answered with "the same reason they don't have particle cannons". Indeed, given that a FEL will typically only convert a fraction of the electrons' energy to X-rays, it would probably be preferable just to shoot electrons themselves at the enemy. FEL only makes sense as a weapon in atmosphere, which generally makes things difficult for electrons. Electrostatic blooming would like to have a talk with you. Besides, IMO, XFEL's are less interesting than far UV FEL's. Being able to easily reflect, steer and focus a beam is important for a laser weapon.As for the others, I suspect thermals would be the killer. I don't think they can run hot enough to end up with a reasonably sized radiator. Now, neither glass fiber nor gas dynamic lasers are a part of my expertise, so maybe there are way to make them run at >1000K, but I would expect that to be quite a challenge, too. Absolutely. IRL max operating temperatures are significantly lower (for fiber lasers, gas dynamic lasers can dump their waste heat at pretty high temperatures but they have beam quality issues IIRC). However, IRL their efficiency is also noticeably higher, so heat pumps would allow for a total system efficiency similar to CoaDE with similar waste heat temperatures. And in CoaDE, the best beam quality factor M² = 3, while IRL lasers have demonstrated an M² < 1.3. IMO, the main difference between IRL laser performance and CoaDE laser performance is that CoaDE lasers have more power to mass, are powered by reactors with a higher power to mass ratio, have a poorer beam quality factor and can't pulse.Telescopes use multi-piece mirrors, with small gaps between them. Not the case for all telescopes. I remember multi-meter single mirror telescopes existing.I don't think you can have that with a laser, seeing as anything that isn't a mirror will absorb the enormous energy that the laser generates, and promptly cease to exist. You can actually overwhelm a mirror in COADE, if you make the energy density too large. Think of how well any non-mirror material would fare in those conditions. So I don't think anything but a monolithic mirror will work. Actively cooled carbon allotropes would work pretty well.
Hitting things at 60km or more with arty is quite trivial, and in fact tube arty does use unguided shells for those (and greater) ranges. How do they do that? A simple, yet effective technique called "shoot a crapton of huge shells". One of them is gonna come close enough. The principle of more dakka reigns supreme both in COADE and IRL, as far as kinetics go. Conventional cannons are useless not because they're inaccurate, but because they're very dodgeable. In COADE, "effective range" is mostly dictated by rounds' time of flight. Spread matters little (as long as it isn't absurd), you just fill a volume of space with glowing-hot armature material of your choice, and hope that enough of it will stick. Of course, that means high-mass weapons are only good for orbital bombardment. They just don't fire fast enough nor fly fast enough to score any good hits. Frag and explosives can help, but it's easier to make a gun that shoots the "fragments" one at a time, at a high rate and high speed. I largely agree, but with this kind of logic lasers are more credible weapons as they can afford to fire more. Even little damage can accumulate over hours.
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Post by airc777 on Jun 22, 2019 16:06:17 GMT
I don't think guns scale up as cleanly as CDE would lead you to believe. Even with very expensive carbon fiber overwraped barrels and cnc spun homogeneous projectiles and ballistics computers it's highly expensive and non trival to build a firearm with 0.25 minutes of arc (or about 0.07 milliradian) accuracy (granted most of that is trying to combat atmospheric related inaccuracy). However in real life we've shot low powered lasers off of one foot square reflectors on the moon.
The 18.1 inch guns on IJN Yamato had gun barrels that weighed 147 tons each, mounted in turrets that weighed more then a thousand tons each, and had a muzzle velocity of only 0.78 km/s. CDE guns are hella fast. IRL guns with comparable velocities are pretty much limited to the Paris gun and Project Babylon and Project HARP.
The thing that CDE does not let you do is put a water jacket on the gun, so real life Maxim gun patterned guns can sustain continuous fire better, having said that there aren't many water jacketed guns still in service that I'm aware of most military's having decided that lower mass quick change barrels are just more practical or at least more economical. However CDE does let you do things like making Kiloton homogeneous diamond barrel jackets, we can't do that yet in real life.
The guns in CDE are monsters. At first I was kind of disappointed that Battlestar Galactica style flak wasn't very efficient, and the EM guns don't quite preform like the colossal beasts in the Halo novels or Mass Effect lore, but I just needed a reality check. CDE guns are still monsters.
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Post by walterscientist on Jun 22, 2019 18:11:45 GMT
I don't think guns scale up as cleanly as CDE would lead you to believe. That is beside the point. If you look at the numbers I provided, you will see that CoaDE guns are less efficient than real post-WW2 guns. Only reason why CoaDE guns get high muzzle velocities is because they fire absurdly light projectiles. For comparison: 40mm Bofors L/60 gun projectile: 900g @ 880m/s = 350kJ kinetic energy 12.7mm BMG: 45g @ 900m/s = 18kJ kinetic energy 5.56mm NATO: 4g @ 950m/s = 1.8kJ kinetic energy 33mm Internal Cannon in CoaDE: 5g @ 2,250m/s = 13kJ kinetic energy That CoaDE gun weighs 180kg and can fire a rifle bullet so fast that it has nearly as much energy as a heavy machine gun bullet. A heavy machine gun weighs 40kg - about 4 times lighter. I call such performance abysmal. While high muzzle velocity is definitely advantageous in space combat I would argue that hitting enemy ships with what pretty much is hyper-velocity gravel would have very limited effect. It should be possible to build guns that fire cannon shells weighing several hundreds grams at extreme velocities, but they immediately end up ponderously heavy and unsuitable for anything supposed to quickly maneuver.
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Post by airc777 on Jun 22, 2019 18:40:41 GMT
- 881m/s muzzle velocity - 900g round - 300g propellant - 120rpm rate of fire 410kg weight Do: Vanadium Chromium Steel barrel material. 1.5meter barrel length. 1.0mm barrel thickness. 0 barrel armor thickness. Octogen propellant. 300gram propellant mass. 5.0mm grain radius. Osmium projectile. 4.0cm bore radius. 900gram projectile mass. 340watt loader. External mount. No attached ammo bay.
Makes 880 meters per second, reloads in 495ms, masses 60.2Kg. Yes it's not the correct shape, but it makes the correct numbers and it's far lighter then 410kg.
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Post by walterscientist on Jun 22, 2019 19:20:44 GMT
Hmm, just... 1 millimeter thick barrel? That can't be right So the key to hyper-velocity is to shoot hockey pucks? I have to say, I am kinda confused how such gun could work at all.
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