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Post by deltav on Feb 21, 2017 18:11:47 GMT
That's what I was pointing out with my bathtub analogy. We have those "energy cells", they're called capacitors. Well, we don't have them in-game, but we pretty much assume any EM weapon is using them because otherwise that peak power is ridiculous. But like the bathtub, the capacitor can't dump energy it doesn't have. So while the capacitor solves problem 1, you still have problem 2: you can't fire another shot until you've given your capacitor time to recharge. Now, that said, if you have a very large surplus of capacitors, you *could* use them to fire a rapid burst until they are depleted. But once that burst is done, you'll be back to one-shot-per-charge because now all your capacitors are empty. You won't be able to do another burst unless you spend the same amount of time charging as you would have spent firing those shots. And I assure you, no ship is carrying enough capacitors to fire their entire ammo reserve without charging. That would just be way too much mass and volume. Right, but the system I am talking about that the Navy is developing is in addition to the capacitors. At least that's what I got from the article. Did you read things differently? We know capacitors cannot store long term the way batteries or fuel cells can, but only temporarily, correct? They can only supply while they are being fed, while fuel cells can store and release even if not supplied at that time. These fuel cells would supplement the power going to the railgun allowing it to sustain a higher rate of fire than what normally would be possible. Does that make any sense to you based on your knowledge even with future battery tech?
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Post by elouda on Feb 21, 2017 18:21:02 GMT
That's what I was pointing out with my bathtub analogy. We have those "energy cells", they're called capacitors. Well, we don't have them in-game, but we pretty much assume any EM weapon is using them because otherwise that peak power is ridiculous. But like the bathtub, the capacitor can't dump energy it doesn't have. So while the capacitor solves problem 1, you still have problem 2: you can't fire another shot until you've given your capacitor time to recharge. Now, that said, if you have a very large surplus of capacitors, you *could* use them to fire a rapid burst until they are depleted. But once that burst is done, you'll be back to one-shot-per-charge because now all your capacitors are empty. You won't be able to do another burst unless you spend the same amount of time charging as you would have spent firing those shots. And I assure you, no ship is carrying enough capacitors to fire their entire ammo reserve without charging. That would just be way too much mass and volume. Right, but the system I am talking about that the Navy is developing is in addition to the capacitors. At least that's what I got from the article. Did you read things differently? We know capacitors cannot store long term the way batteries or fuel cells can, but only temporarily, correct? They can only supply while they are being fed, while fuel cells can store and release even if not supplied at that time. These fuel cells would supplement the power going to the railgun allowing it to sustain a higher rate of fire than what normally would be possible. Does that make any sense to you based on your knowledge even with future battery tech? Well, there's always research into better forms of energy storage, and from that article it seemed to just be talking about improvements to capacitors and capacitor networks. With regards to the other part, it gets a little more complicated. One of the important things for railguns is that the energy delivered to the system is very high amperage, and this is something you might not be able to provide out of your 'regular' power network onboard the vessel, but only by discharging said capacitors. Thus linking batteries or fuel cells directly to the rails probably won't do much - on the other hand, you could have a supplementary set of fuel cells or even a full on reactor dedicated only to providing energy to recharge the capacitors.
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Post by vegetal on Feb 21, 2017 18:24:37 GMT
vegetalPlease be a part of this if you want. If not, ignore, cause this is all about fun right? Totally understand if you aren't interested. Oh I am interested. I don't know why you think I'm not. I was just trying to make the situation clear for you: guns are broken, it's a fact. We just don't know why. If I were to hazard a guess, I think it has something to do with waste heat. It appears real railguns heat up a lot, and the ones we have in-game are able to fire a gazillion shots per second. That smells wrong. But I don't know how the game handles heat, gun barrels have ultra quick cooldown times, and I know the game treats the materials as if they were at a constant temperature, which could lead to some weirdness on some extreme cases.
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Post by Easy on Feb 21, 2017 18:35:09 GMT
Right, but the system I am talking about that the Navy is developing is in addition to the capacitors. At least that's what I got from the article. Did you read things differently? We know capacitors cannot store long term the way batteries or fuel cells can, but only temporarily, correct? They can only supply while they are being fed, while fuel cells can store and release even if not supplied at that time. These fuel cells would supplement the power going to the railgun allowing it to sustain a higher rate of fire than what normally would be possible. Does that make any sense to you based on your knowledge even with future battery tech? Well, there's always research into better forms of energy storage, and from that article it seemed to just be talking about improvements to capacitors and capacitor networks. With regards to the other part, it gets a little more complicated. One of the important things for railguns is that the energy delivered to the system is very high amperage, and this is something you might not be able to provide out of your 'regular' power network onboard the vessel, but only by discharging said capacitors. Thus linking batteries or fuel cells directly to the rails probably won't do much - on the other hand, you could have a supplementary set of fuel cells or even a full on reactor dedicated only to providing energy to recharge the capacitors. simple amperage isn't insurmountable if you have enough power, simply use a transformer. Alternating current isn't an issue since railguns and coilguns have a short current duration. P = I*V
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Post by bigbombr on Feb 21, 2017 18:36:54 GMT
vegetal Please be a part of this if you want. If not, ignore, cause this is all about fun right? Totally understand if you aren't interested. Oh I am interested. I don't know why you think I'm not. I was just trying to make the situation clear for you: guns are broken, it's a fact. We just don't know why. If I were to hazard a guess, I think it has something to do with waste heat. It appears real railguns heat up a lot, and the ones we have in-game are able to fire a gazillion shots per second. That smells wrong. But I don't know how the game handles heat, gun barrels have ultra quick cooldown times, and I know the game treats the materials as if they were at a constant temperature, which could lead to some weirdness on some extreme cases. I suspect cannons, coilguns and railguns can fire until they reach the melting point of their barrel. IRL, they would only be able to fire until their barrel becomes malleable. Since radiating heat scales with the 4th power of temperature, this has a massive impact on cooldown time. This however is different from the impossibly efficient coil- and railguns. Their issues would be related to 'integer issues' or something like that. Qswitched made a few posts about it, somewhere.
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Post by Easy on Feb 21, 2017 18:40:27 GMT
Oh I am interested. I don't know why you think I'm not. I was just trying to make the situation clear for you: guns are broken, it's a fact. We just don't know why. If I were to hazard a guess, I think it has something to do with waste heat. It appears real railguns heat up a lot, and the ones we have in-game are able to fire a gazillion shots per second. That smells wrong. But I don't know how the game handles heat, gun barrels have ultra quick cooldown times, and I know the game treats the materials as if they were at a constant temperature, which could lead to some weirdness on some extreme cases. I suspect cannons, coilguns and railguns can fire until they reach the melting point of their barrel. IRL, they would only be able to fire until their barrel becomes malleable. Since radiating heat scales with the 4th power of temperature, this has a massive impact on cooldown time. This however is different from the impossibly efficient coil- and railguns. Their issues would be related to 'integer issues' or something like that. Qswitched made a few posts about it, somewhere. I think you are correct that the game gives the same material properties through the entire temperature range, so an alloy has a 300MPa yield strength at 3K and 900K, even if it melts at 901K.
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Post by deltav on Feb 21, 2017 18:48:13 GMT
So I think I get it. Back to our stock 0.2 MW 3 mm railgun. The 0.2 MW is a measure of how much "work" the railgun can do per second. So with a known velocity and round mass, the amount of "work" the round can do must be within a certain fraction of that, in this case about 13,000 J.
Although the round is impacted by the railgun for only a fraction of a second, the total amount of "work" done by the railgun (Energy) within a given frame of time (Power), here seconds, cannot be more than a certain number, Kinetic Energy / Second = 1/2 * Projectile Mass * (Muzzle Velocity)² / Time between shots.
0.5*mass*v^2 = KE per shot In this case (0.5* 0.0025 kg * (5060 m/s)^2)/1000ms = 12,801.8 J per shot.
Then taking Power into account, the fastest possible rate of fire is 65 ms per shot or about 15.38 shots per second, which is 3 rounds per second lower than the ingame rate of fire. I think I get it. Have I got it?
But how does the loader come into play? And what does it have to do with anything?
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Post by deltav on Feb 21, 2017 18:49:39 GMT
Qswitched made a few posts about it, somewhere. I've been searching but couldn't find any... so much is left out for new players.
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Post by xenophon13 on Feb 21, 2017 19:00:09 GMT
Regarding getting "under the hood,' here's a blog post where Qswitched goes into quite a bit of detail about where his railgun equations came from. I have no idea if these are the equations that are actually currently implemented, and I presently don't have the time to go over them myself, but they might offer some clue as to what's causing the bug.
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Post by Enderminion on Feb 21, 2017 19:26:00 GMT
We should probably check weather these weapons can propel the shots at the speeds were talking... Once. deltav loader power is abstracted in a way that makes it possible for energy in to be less then energy out
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Post by deltav on Feb 21, 2017 21:39:19 GMT
We should probably check weather these weapons can propel the shots at the speeds were talking... Once. deltav loader power is abstracted in a way that makes it possible for energy in to be less then energy out From what I understand, the speeds of the shots was never in contest, and comply with physics 100%. The issue is the rate of fire, and if that is realistic for the given MW or not. Am I right? All the railguns and coilguns check out if you lower the rate of fire enough.
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Post by vegetal on Feb 21, 2017 23:28:57 GMT
Actually, muzzle velocity would be less than what we have now, because the game doesn't model materials having different properties in different conditions, like higher temperatures. Things would become soft way before melting.
But I don't know how much that influences our problem of thermodynamics non compliance.
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Post by ross128 on Feb 22, 2017 0:11:31 GMT
Well, it depends on what assumptions you want to make.
If you want to assume that the EM weapons aren't fed by capacitors, but instead have a direct line to the reactor, then velocity also becomes a problem. In that you need really long rails to reach high velocities.
For example, let's say you want to accelerate a 1 gram projectile to 20km/s and you have 1MW to do it with. By the time it's done accelerating, that 1 gram projectile is going to have 200,000J or 0.2MJ stuffed into it, so you're going to need 0.2 seconds total to get it going.
0.2 seconds doesn't seem like much, right? Well, if you assume constant acceleration (which is a simplification, but a useful one) the average speed of that projectile in the barrel will be 10km/s. In those 0.2 seconds the projectile will travel 2 kilometers. And that's how long the barrel has to be, because if the projectile leaves the barrel before those 0.2 seconds are up? It won't be hitting the speed you want.
Nobody wants to build a 2 kilometer barrel to get a working gun. So we'd much rather assume that we have capacitors, even though the game does not represent them or account for them at all. But if you're using capacitors to shrink your barrel length, your reload time is still going to be capped to a minimum of 0.2s. Because that's how long it'll take 1MW to charge 0.2MJ.
So, if we just go ahead and handwave that away, that brings us to the problem of the loader. The loader is, as far as we can tell, power that is consumed by some abstract mechanism to pull a round out of an ammo bin, and stuff it in the breach of a gun. All of the loader's power, as the game treats it, is consumed by the loader itself. The game does not account for rate of fire in any way whatsoever when calculating the power consumption of the rails/coils, as you can see by the fact that you can set the loader to whatever rate you like, and neither the power consumption nor the performance characteristics of the actual rails/coils will change. They are completely separated from each other.
Of course, another way to go about it would be to take a cue from Home Improvement: more power. Let's say you want to pull off the same acceleration in a 2m barrel. You'll have the same average velocity (because you're still going from 0 to 20k at a constant rate), but you're going to have to cover it in 0.0002 seconds, or 1/1000th of the time. That means you'll need 1000 times the power, or 1GW. If you did hook that gun up to a 1GW reactor, you'd also have enough power to fire it with a 0.2ms reload time because that's how long it takes 1GW to deliver 0.2MJ.
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Post by theholyinquisition on Feb 22, 2017 1:32:48 GMT
Oh I am interested. I don't know why you think I'm not. I was just trying to make the situation clear for you: guns are broken, it's a fact. We just don't know why. If I were to hazard a guess, I think it has something to do with waste heat. It appears real railguns heat up a lot, and the ones we have in-game are able to fire a gazillion shots per second. That smells wrong. But I don't know how the game handles heat, gun barrels have ultra quick cooldown times, and I know the game treats the materials as if they were at a constant temperature, which could lead to some weirdness on some extreme cases. I suspect cannons, coilguns and railguns can fire until they reach the melting point of their barrel. IRL, they would only be able to fire until their barrel becomes malleable. Since radiating heat scales with the 4th power of temperature, this has a massive impact on cooldown time. This however is different from the impossibly efficient coil- and railguns. Their issues would be related to 'integer issues' or something like that. Qswitched made a few posts about it, somewhere. Actually, the heating limit would be the Curie point of the material in question.
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Post by deltav on Feb 22, 2017 1:40:44 GMT
I went on Qswitched Dev blog many times before I bought the game. Never saw this part until xenophon13 pointed it out... "A final concern is cooling. All of these weapon designs can use simple radiative cooling effectively in space to cool down, letting their long, exposed barrels radiate away all their excess heat. This is actually quite effective, and it is uncommon for projectile weapons to require additional radiators beyond their own gun barrel (unless you count the reactors powering them, which is a different story)." Why temp doesn't seem to be much of an issue. The railguns seem to be pretty good radiators as well. "...so I ended up setting some of the choices in stone. Only capacitors were implemented for pulsed power, and I implemented continuous power as well. Also, I set the power supply to only attach at the start of the rails. In any case, the current was derived in two different ways for both pulsed and continuous power..." "Thus, I had to use numerical analysis to calculate the final exit velocity (specifically, I’m using a Fourth Order Runge Kutta method), and I finally had my exit velocity."The exit velocities are approximated instead of calculated because it was decided that "the integral ended up being non integrable." It couldn't be calculated it seems, but could be approximated. "My inputs were the following values: Rail Bore Radius, Rail Thickness, Rail Length, Rail Material (for resistivity), Armature Material (for resistivity), Armature Mass, Capacitance, Power Consumption. Not bad. Capacitance is derived further, but that’s a whole other blog post."Capacitance did you say your grace? Capacitance? Perhaps the loader is "Capacitance", and the loader is our way of adding more or less capacitors? How much of a plot twist would that be!? If the loader is really more or less capacitors, then maybe that explains everything.
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