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Post by ross128 on Oct 4, 2016 15:56:22 GMT
That's the formula for kinetic energy of an object, divided by the fire rate. As an example, if you fire a 1 kilogram object out of a railgun at 1 meter per second every second, you're producing power equivalent to .5 * (1 m/s)^2 * (1 kg) / (1s), you're producing .5 kg m^2 / s^3, or .5 Watts - IE, the power you'd be extracting from the gun if you used the projectile to push a (perfectly efficient) wheel or something. The formula is perfectly fine, you did your unit conversion wrong. (50 km/s)^2 isn't 2500 km/s, it's 2500 km^2/s^2, or (2500 km^2/s^2)(1000 m/km)(1000 m/km) - or 2,500,000,000 m^2/s^2. If you don't want to deal with unit conversions, I'd suggest using Alpha, which can handle a lot of it automatically. ...also I did get it wrong, it's .15 GW (or 150 MW), but that's just because I copied the result down wrong to the forum  . Still breaks physics! ________________________________________________________________ I think the main cause of "physics breaking" on rail/coilguns right now might rest in how rate of fire is calculated. Right now, your loader's power consumption and the projectile's mass are pretty much the sole determinants of rate of fire and the loader's power consumption is completely independent of the rail/solenoid's power consumption. What this means is that, as long as the loader is drawing less power than the rail/solenoid, we can arbitrarily increase our rate of fire with no change in overall power consumption. Which is obviously wrong, because that means we're changing our total power output without changing the input at all. The energy per projectile is in the kilojoule range, which isn't absurd at all, what is absurd is that cranking 100 rounds per second through the gun uses no more power than 1 round per second (and also doesn't increase barrel's heat buildup at all, which is also a problem for ballistics). To portray the guns more realistically, EM guns would have to multiply their power consumption by their rate of fire (assuming the base is calculated at 1 round/s). Conventional guns would not, because they don't draw power to fire (that's what the explosives are for), however a higher rate of fire would generate more heat for the barrel to dissipate in all projectile weapons, which may potentially have to be dealt with by cycling multiple barrels or using some kind of forced cooling system. It would be quite a devastating nerf to EM guns of course, as high-RoF EM guns would suddenly become incredibly power-hungry. |
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Post by blothorn on Oct 4, 2016 16:48:53 GMT
I believe that the developer has stated that railguns/coilguns are not using capacitative smoothing, and that power is supposed to be the peak power. So varying with rate of fire is not broken, but efficiency is off by a few more orders of magnitude than the trivial calculation suggests.
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Post by ross128 on Oct 4, 2016 18:00:09 GMT
That's quite an odd way to list the power consumption (it makes sense from the reactor's perspective, but not the gun's), and not using capacitors strikes me as terribly impractical. But if what you're saying about it being "peak power" is correct, I assume that means that the rating is the maximum draw of a single round while it is being fired.
Which would mean the average power consumption of the gun over time (the thing that we would compare to its total output) would actually be less than its peak power for a single round, proportional to how long the barrel contains a round in a given second (I'll call this "barrel utilization"). This is a bit complicated to determine, since we'd have to find the time between when the first round leaves the barrel and the second round is chambered (this is not quite equal to the loading time, because the loader can start actuating while the previous round is still traveling down the barrel).
Basically, a railgun with 200kW peak single-shot power would only actually consume 200kW over the course of a battle if it was short-circuited (100% barrel utilization, the barrel is never unoccupied). If the barrel was empty 50% of the time, that would be 50% barrel utilization, its average power consumption would be 100kW and its output correspondingly should not exceed that. So that doesn't help solve the discrepancy, if anything it makes it worse. If you calculate power consumption that way, then instead of multiplying your power consumption by your rate of fire, you'd have to cap your rate of fire to your power consumption: you can't have more than 100% barrel utilization, the previous round needs to leave the barrel before you can load the next one.
At the same time, a railgun that only delivered 200kW of peak power in a single shot would need absurdly long rails to achieve any significant muzzle energy (or would have to fire a heavy round at a very low velocity, but at that point you might as well use gunpowder) because the round would have to spend a lot of time in the barrel, which means capacitors are the only reasonable way to achieve low-power high-energy railguns.
Actually, the railgun on page 5 provides a great example of the barrel length problem. It fires a 1 gram projectile at about 50km/s, giving it a muzzle energy of about 1.25MJ (keeping in mind that our base units are meters and kilograms, so it's 50,000m/s and 1/1,000kg). It has a rated peak power of 6.4MW, so it's going to take at least 0.195 seconds (1.25/6.4, conveniently they're on the same order of magnitude) to deliver that energy to the projectile.
If the muzzle velocity is 50km/s, then the average velocity in the barrel starting from zero is 25km/s (assuming smooth, continuous acceleration). So, in the 0.195s that the gun needs to deliver its energy, the projectile will travel 4,882.8m. This is the shortest the barrel can possibly be without using a capacitor bank. If the barrel is shorter than this, the round will exit the barrel prematurely and have a correspondingly lower velocity. Also, 0.195s is the minimum time between shots because you can't load the next shot until the first one is out of the barrel, giving that gun a maximum rate of fire of about 5rps.
It would have the same rate of fire cap if you use a capacitor bank(you'd just be trading charging time for time in-barrel, you're storing 1.25MJ at a rate of 6.4MW either way), but it would be able to have a much shorter barrel based on the quality of the capacitor bank.
tl;dr:
Rate of fire is relevant no matter which way you look at it, the only difference is whether rate of fire multiplies power consumption or power consumption caps rate of fire.
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Post by randomletters on Oct 5, 2016 0:18:06 GMT
Also, 0.195s is the minimum time between shots because you can't load the next shot until the first one is out of the barrel, giving that gun a maximum rate of fire of about 5rps.  I lowered power to the loader and lo and behold it stops breaking the laws of physics at 340W and is quite reasonable at 100W. I'll give it a test and see if it's still an effective weapon with a much lower ROF. |
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Post by pokington on Oct 5, 2016 1:55:23 GMT
I lowered power to the loader and lo and behold it stops breaking the laws of physics at 340W and is quite reasonable at 100W. I'll give it a test and see if it's still an effective weapon with a much lower ROF. If my math is right, that projectile is accelerating at almost 6.5 million gravities. wut It's not a gun. It's a rocket engine that produces 63.5kN of thrust with an exhaust velocity of 50.4km/s. There is zero way that projectile would survive as anything but plasma. |
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Post by blothorn on Oct 5, 2016 3:26:12 GMT
My investigations into capital ship armor suggest that for the weight of the armor necessary to survive a broad variety of weapons, you can carry enough ordnance that you never need to see it. The carrier itself is lightly armored and armed--just a laser to give some breathing room if engaged by drones or missiles (although if that happens, something has gone terribly wrong). Pre-deploying a squadron of drones for added point-defense is highly recommended.  The complement is 320 103kt missiles, 200 Hailstorm drones, and 80 Meteorite and Solar Flare drones. The Hailstorm is just a step up from a missile: very light and cheap. The kinetic cannon is devastating but short-ranged; it can make quick work of ships that have lost their lasers, but is unsuited to head-on assaults against balanced ships.  The Meteorite and Solar Flare drones are more technical. The Solar Flare's laser makes it an excellent anti-drone option, while in a pinch it can turret-snipe against capital ships (although its effective range when doing so is short enough that going for the kill with Hailstorms is likely a better option). The Meteorite features a long-range (>100km) railgun; while its 1g projectiles stand little chance against a properly-armored hull, it can hope for lucky hits on turrets and radiators from very long ranges.  This carrier relies on progressively stripping defenses: a missile can strip Whipple shielding, making the hull vulnerable to the Meteorite's railgun. Or the Meteorite can knock off lasers or radiators, giving the Hailstorm a chance to get close. Against enemy drones and missiles, the shear volume available to the carrier (and the high DV of the missiles and Hailstorm drones) allow it to trade 1:1 against most enemies. Note: Apologies for attaching the full UserDesigns; I am not going to attempt to isolate the transitive closure of all of this. Attachments:UserDesigns.txt (187.79 KB)
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Post by Durandal on Oct 5, 2016 5:26:37 GMT
snip Against enemy drones and missiles, the shear volume available to the carrier (and the high DV of the missiles and Hailstorm drones) allow it to trade 1:1 against most enemies. Note: Apologies for attaching the full UserDesigns; I am not going to attempt to isolate the transitive closure of all of this. Do you ever have frame rate issues? |
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Post by ross128 on Oct 5, 2016 5:46:13 GMT
I've been doing a lot of experimenting with missiles, and at one point I decided to make a missile as small as I possibly could while still being useful.  I could certainly make a missile smaller than that, but this is about where I put the "useful" cutoff. Making a tiny engine and tiny payload were simple enough, the main bottleneck was having to add enough fuel to get a respectable delta-V. It's too bad MPD thrusters are so power hungry, they'd make great micro-missile engines (you can make some that only weigh a few grams) if they didn't have to push around a couple hundred kilograms of reactor for power. A converted siloship was able to easily hold 7200 of these. They took up less space than the crew module and only weighed about 220 tons, I just stopped adding more because it was getting ridiculous. For the launcher I just slapped them in a copy of the 50kw Flak Missile Launcher, and because they were so light that thing was able to kick them out at 10m/s with a 0.5s load time. In other words, it could spit out missiles so fast that it could use them during a flyby. I stuck ten of those on the converted Siloship and sent it to Vesta.  Those red dots ended up as dead as my frame rate. Also pictured was an experiment with a gyrojet coilgun. Also remarkably effective, especially since all the coilgun had to do is kick the missiles in vaguely the right direction. Terribly expensive due to the sabot though, the standard missile launcher is much more practical even if making the missile do all the work results in a lower hit rate. |
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Post by blothorn on Oct 5, 2016 5:51:31 GMT
I launched 120 drones into a battle once and vowed never to do it again  . I tend to use groups of 5-40 drones at a time to avoid both framerate and friendly-fire issues. It is also generally a good idea to avoid excessive clumps of drones tactically; if you have too many drones in the air at once it becomes cost-effective for your opponent to try to dodge them, and large groups are very vulnerable to nuclear missiles. Edit: speaking of miniature missiles,  I keep meaning to see if it is useful as point defense. |
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Post by 123nick on Oct 5, 2016 16:44:27 GMT
I launched 120 drones into a battle once and vowed never to do it again . I tend to use groups of 5-40 drones at a time to avoid both framerate and friendly-fire issues. It is also generally a good idea to avoid excessive clumps of drones tactically; if you have too many drones in the air at once it becomes cost-effective for your opponent to try to dodge them, and large groups are very vulnerable to nuclear missiles. Edit: speaking of miniature missiles, I keep meaning to see if it is useful as point defense. im pretty sure the worlds smallest nuke ever made IRL weighed more than that. i think. IIRC. |
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Post by nivik on Oct 6, 2016 2:39:00 GMT
I launched 120 drones into a battle once and vowed never to do it again . I tend to use groups of 5-40 drones at a time to avoid both framerate and friendly-fire issues. It is also generally a good idea to avoid excessive clumps of drones tactically; if you have too many drones in the air at once it becomes cost-effective for your opponent to try to dodge them, and large groups are very vulnerable to nuclear missiles. Edit: speaking of miniature missiles, <snip> I keep meaning to see if it is useful as point defense. im pretty sure the worlds smallest nuke ever made IRL weighed more than that. i think. IIRC. Right now we're able to compress our fusion fuel 20 metric tons per cubic meter, which -- if my math is correct (and it might not be), means the resting pressure in the core of those nukes is something like 9.5 gigapascals. About half of what it takes to make diamonds out of carbon. Almost 100,000x atmospheric pressure. Granted, even liquid hydrogen only has a density of 70 kg/m^3 apparently, so...there must be something going on that I don't understand. Maybe we're using lithium deuteride/tritide, but those compounds would only have a density slightly over 780 kg per m^3. Then again, LiD is a valid fusion booster IRL, but I haven't gotten it to work in game, so I'm not exactly sure what's up. Either way, our boosted nukes are purely ludicrous. |
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Post by teeth on Oct 6, 2016 5:48:57 GMT
My Europa-Class frigate, carries 5000 nuclear missiles and a 21 MW laser. I was considering adding some higher yield missiles but it usually only takes 20-40 missiles to kill a cap ship depending on how they hit. Why bother with bigger missiles when I can always solve it with more missiles?  This is the missile it uses, I'd get it even cheaper but I want at least 3.5 km/s to pull off crazy intercepts.  I might make a destroyer next, with more powerful/multiple lasers, multiple types of missiles, and a better range. Might make a cruiser after that, but the Tsiolkovsky equation really doesn't like big ships. |
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Post by shiolle on Oct 7, 2016 4:27:36 GMT
My design is not as fancy as many others posted here, still I'm satisfied with it for now. During Vesta mission I've noticed that my ships fared poor in a direct gunfight with the enemy, and while they destroyed the enemy in the end, they were taking significant losses. The ship that was giving me most troubles was the enemy corvette. I've noticed how much beating it is able to take, even though by the time their fleets intercepted mine it was already damaged. Even though you can win any mission by just overwhelming the enemy with missiles (stock ones), I wanted to try to make a small and relatively cheap combatant for ship-to-ship brawl. Here's what I've got so far:  It's half the mass, almost half the cost, has missiles and can usually kill the corvette with little to moderate damage in a one-one fight (without using its missiles). It is also pretty survivable and has 50% more radiators for its reactor than it needs, meaning it will still shoot even when pretty beat up. The two inner-most layers of armor only cover the crew modules in front and are designed to protect against 11mm railgun rounds. The only really knew weapon system on it is the 5mm railgun.  It was an attempt to make a give 11mm railgun more penetration. It fires 15g slugs - 15 times heavier than 11mm rail gun, so each slug has 15 times the kinetic energy. However it has 10 times slower rate of fire, but still it puts out 40% more mass per second than the stock railgun. Nothing spectacular of course but it does give my gunship an edge over the corvette in terms of firepower. It also requires less power which means, I believe, that when your radiators are damaged other guns may stop firing but this one won't. |
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Post by tukuro on Oct 7, 2016 4:47:10 GMT
A cheap way to increase the survivability of radiators against kinetics is to make them long and narrow, and running your reactors at 2500k (exit temperature).
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Post by shiolle on Oct 7, 2016 5:20:17 GMT
Well, there are some problems with that. Making them tall and narrow, like spikes, will make them re-radiate tons of heat onto each other. With long and narrow radiators that's not a problem, but on the other hand you have to start fitting things between your radiators, which means that in a fight both your radiators and your weapons are likely to go down together if the enemy targets either of them. So there has to be a balance, but I will experiment with 2500K reactors. Are there any downsides to them?
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. Still breaks physics!
.
