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Post by underwhelmed on Feb 6, 2017 5:52:58 GMT
First it was my missiles running out of propellant despite being set to a 15% reserve... I saw in some threads people suggesting reducing the turnaround time and that seems to have helped, but now I'm getting this issue where my missiles will for some reason start firing their thrusters when getting hit by a laser, even with dodging turned off. This wouldn't be too large of an issue, except for some reason my entire fleet of missiles will also start thrusting when one missile dies... and after one or two go down, the entire fleet runs out of dV. Any bright ideas why this is happening?
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Post by n2maniac on Feb 6, 2017 7:59:29 GMT
Does it also happen for smaller missile fleets (say, under 30?)
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Post by vegemeister on Feb 6, 2017 8:38:27 GMT
What is their Δv, burn time, and acceleration? What's the engine gimbal RPM? What's the turnaround time for the whole missile? What are the guidance settings on the remote control unit? Midcourse phase is most important, 'cause that's when they're supposed to be coasting.
There's kind of a tradeoff between missile acceleration and capability against high-acceleration maneuvering targets. High acceleration missiles are more fun because they're usable in combat mode, but you can't reduce the turnabout time much below 1 s without running into stability problems with the attitude control, so they use more fuel turning, and they seem to require greater guidance damping, so the fuel isn't used as efficiently.
I did run into a problem with drop tanks where if the jettison velocity was too slow, a flight of missiles would go squirrely trying to dodge each other's drop tanks. But if you turned dodging off and the problem persisted, it wouldn't be that.
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Post by The Astronomer on Feb 6, 2017 14:21:07 GMT
Try to have the burn time at least 30 sec. My missiles usually have them in range of 1 minute.
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Post by ross128 on Feb 6, 2017 16:24:38 GMT
As mentioned, there are a number of different things that can cause this. One factor is missile acceleration: if acceleration is too high (~20Gs seems to be the usual cutoff, give or take a bit) missiles will fail to shut off their engines for coast stages. Because missile acceleration increases as they burn fuel (they're getting lighter), this can crop up even in seemingly low-acceleration missiles if your terminal reserve is small. Reducing engine thrust or holding a larger reserve (ie shutting off the engines while the missile is heavier) can alleviate this.
Alternatively, you can do away with the need for a boost phase by staging the missiles from a drone. With a careful intercept the drone can boost the missiles in to give them a good closing velocity, and the missile's RC can simply be programmed to not light the rocket until terminal stage (at which point inability to shut off is no longer a problem). Gun-launching can produce similar results if you want to launch high-acceleration missiles in combat mode.
Another thing to look out for, in bipropellant rockets at least, is fuel ratios. If your tanks don't match your fuel ratios, it causes errors with the dV calculation: the game will calculate the missile as having more dV than it actually has, because it'll run out of one propellant before the other. This throws off the guidance computer, causing it to burn through all its propellant because it thinks it still has some left, but half of a redox pair won't light any fires by itself.
As far as missiles trying to "dodge" lasers though, I actually haven't encountered that before. But it's possible that the laser might have breached one of the propellant tanks. Venting a propellant tank will typically generate enough force to throw a missile off course, which could cause it to try to correct. Though if a tank has been breached, that missile isn't going to live much longer anyway.
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Post by underwhelmed on Feb 7, 2017 0:21:18 GMT
Missile stats in question. It happens for fleets as small as 5. Midcourse does not have accelerate selected (Boost is PN with 0.2 and accelerate; terminal is APN with 1.0 and accelerate). No drop tanks involved. Too high acceleration might've been a problem in earlier iterations, but my missile doesn't have any problems stopping the burn at the right time now. The problem is them restarting engines for reasons unknown when one of their cohort get destroyed. The missile I'm having trouble with right now is actually a drone used to launch smaller missiles... I'm using a bi-propellant, but I'm pretty sure the ratios are right to like the 4th digit.
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Post by lieste on Feb 7, 2017 0:50:34 GMT
They have dodging active? I've seen AI drone fleets do this too and it often costs several dead due to collisions, which is amusing and helpful (for the PD job) even if obviously not optimal.
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Post by underwhelmed on Feb 8, 2017 2:54:23 GMT
So, I've done some more experimentation and I believe I can explain at least part the problems I've been having.
1. Missiles start out 1000km from my laser test ship and enter boost phase until they expend their allotted propellant 2. After entering midcourse guidance (which really is kind of a misnomer, IMO, because it doesn't really do minor course corrections as far as I can tell but just keeps accelerating if you check the box), my laser test ship keeps merrily accelerating at a breezy 1.2Gs 3. And since missile guidance algorithms aren't taking into account constant acceleration, they're going to miss by a pretty wide margin as they just keep drifting 4. At some point, when in homing mode, the missile goes "Oh, crap, I'm undershooting!" and turns the engine back on, burning for a second before running out of dV
It would be really great to have additional missile guidance options... it's pretty odd to be able to tweak reactors and engines down to the millimeter but be stuck mixing a few algorithms with pure pursuit.
As for the sporadic engine burns when getting lasered, my hypothesis is that when the laser ablates the armor, the engines temporarily burn to maintain course.
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Post by Enderminion on Feb 9, 2017 1:09:39 GMT
So, I've done some more experimentation and I believe I can explain at least part the problems I've been having. 1. Missiles start out 1000km from my laser test ship and enter boost phase until they expend their allotted propellant 2. After entering midcourse guidance (which really is kind of a misnomer, IMO, because it doesn't really do minor course corrections as far as I can tell but just keeps accelerating if you check the box), my laser test ship keeps merrily accelerating at a breezy 1.2Gs 3. And since missile guidance algorithms aren't taking into account constant acceleration, they're going to miss by a pretty wide margin as they just keep drifting 4. At some point, when in homing mode, the missile goes "Oh, crap, I'm undershooting!" and turns the engine back on, burning for a second before running out of dV It would be really great to have additional missile guidance options... it's pretty odd to be able to tweak reactors and engines down to the millimeter but be stuck mixing a few algorithms with pure pursuit. As for the sporadic engine burns when getting lasered, my hypothesis is that when the laser ablates the armor, the engines temporarily burn to maintain course. the missile that gets lasered tends to accerate ahead of the main body, IDK why
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Post by bigbombr on Feb 9, 2017 9:04:42 GMT
the missile that gets lasered tends to accerate ahead of the main body, IDK why Perhaps the missile gets lighter as the armour gets ablated?
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Post by bdcarrillo on Feb 9, 2017 13:51:46 GMT
the missile that gets lasered tends to accerate ahead of the main body, IDK why Perhaps the missile gets lighter as the armour gets ablated? Hmm, I noticed that too. I kinda doubt that ablating a few kilos of armor on stock missiles makes much difference in their acceleration. Is fuel temperature modelled? Edit- looks like I was incorrect, it's mass
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Post by underwhelmed on Feb 9, 2017 14:35:05 GMT
It's ablation. I've seen the dV of my missiles increase when getting lasered, which strongly implies a reduction in mass.
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Post by ross128 on Feb 9, 2017 15:06:21 GMT
Yep, I've noticed the same thing. It wasn't as noticeable back when missiles were armored with a milimeter of aerogel, but now that they're ablating several layers of rubber the change in weight is very noticeable.
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Post by vegemeister on Feb 9, 2017 15:35:55 GMT
So, I've done some more experimentation and I believe I can explain at least part the problems I've been having. 1. Missiles start out 1000km from my laser test ship and enter boost phase until they expend their allotted propellant 2. After entering midcourse guidance (which really is kind of a misnomer, IMO, because it doesn't really do minor course corrections as far as I can tell but just keeps accelerating if you check the box), my laser test ship keeps merrily accelerating at a breezy 1.2Gs 3. And since missile guidance algorithms aren't taking into account constant acceleration, they're going to miss by a pretty wide margin as they just keep drifting 4. At some point, when in homing mode, the missile goes "Oh, crap, I'm undershooting!" and turns the engine back on, burning for a second before running out of dV It would be really great to have additional missile guidance options... it's pretty odd to be able to tweak reactors and engines down to the millimeter but be stuck mixing a few algorithms with pure pursuit. As for the sporadic engine burns when getting lasered, my hypothesis is that when the laser ablates the armor, the engines temporarily burn to maintain course. I've had difficulty getting missiles to hit anything with that much acceleration, too. But on the bright side, if you've caused the opponent to accelerate at 1.2 Gs the whole time the missiles are closing, you've made him use up a lot of his fuel. That fuel potentially masses a lot more than the missiles you had to send to make your opponent expend it. Midcourse guidance will do minor corrections if you set the damping low enough, but with high-acceleration missiles that can make them unstable. Unfortunately the computer burns perpendicular to it's trajectory when it makes corrections, which increases instability because the perpendicular acceleration is greater and the missile has to make larger movements to change which direction it's thrusting. It also exposes the weak side armor to PD fire at steep incidence angles. I wish there was an option to make midcourse guidance blend with no-burn and then with accelerate, so that the missile would still point in the general direction of the target when making corrections. You might try using APN for the boost phase. If the target keeps accelerating in the same direction, that should put the missiles on the proper course from the get go. Of course, it can still evade by accelerating in different directions and varying it's thrust. And also APN can theoretically be fooled by running out a weight on a tether and firing the engines just a bit, to give your ship a continuously rotating centripetal acceleration without expending any additional fuel.
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Post by Enderminion on Feb 9, 2017 15:50:00 GMT
yeah, APN all the way for nukes, you want them to hit; but with directional warheads PN might work
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