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Post by the_Demongod on Dec 23, 2016 19:16:30 GMT
Has anyone else had issues with missiles exhausting all their deltaV during the boost phase? I first noticed it with a missile I was building and wrote it off as a problem with my design (I'd heard high acceleration can cause engines to be unable to shut off fuel flow) but after further testing and a brand new missile design (with relatively low acceleration), I'm still having the same issue. I even tested the stock missile schooner and had the problem occur a couple times (but not nearly as often). An issue or something I'm missing with the new guidance system? I'm only using the stock remote control module and default tracking behavior though... and the remote control very clearly has a 65% boost deltaV setting so something's not working right.
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Post by amimai on Dec 23, 2016 19:33:56 GMT
There are 3 reasons why this can happen:
1) most common- your target is moving too fast, if your target is constantly accelerating the missiles needs to correct its flight path a lot and will exhaust dV eventually
2) fuel evaporates- thermal damage from lasers and nukes can boil the fuel inside the tanks until it's all gone
3) leaky engines- some conventional engines can't stop burning fuel immediately, but unless you have really huge engines/low burn time this is almost never an issue
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Post by lieste on Dec 23, 2016 19:57:38 GMT
Could it be the 50% available delta-V 'bug' noted in the bugs section.
After all if the burn is based on 65% of the planning delta-v it will run out completely if being expended at 2x rate.
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Post by the_Demongod on Dec 23, 2016 19:59:56 GMT
Weird, I can't say that my situation meets any of those conditions. This happens against stationary, non-retaliating targets (cargo stations), using missiles with small engines. They simply burn all their dV during the boost phase and become "disabled," despite using default homing rules. This usually happens to at least 4/5 of all missiles launched in a barrage. I'll shoot 100 and only a few dozen actually reach the target, if any. Could it be the 50% available delta-V 'bug' noted in the bugs section. After all if the burn is based on 65% of the planning delta-v it will run out completely if being expended at 2x rate. You might be onto something there, I'll go look at the bugs section. |
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Post by concretedonkey on Dec 23, 2016 20:24:17 GMT
I usually get this with fluorine fueled small missiles... I think the explanation was that the acceleration was enough to force the fuel in the engine even without the turbopump doing anything. Try to decrease the acceleration if this is the case.
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Post by amimai on Dec 23, 2016 20:42:39 GMT
Weird, I can't say that my situation meets any of those conditions. This happens against stationary, non-retaliating targets (cargo stations), using missiles with small engines. They simply burn all their dV during the boost phase and become "disabled," despite using default homing rules. This usually happens to at least 4/5 of all missiles launched in a barrage. I'll shoot 100 and only a few dozen actually reach the target, if any. Could it be the 50% available delta-V 'bug' noted in the bugs section. After all if the burn is based on 65% of the planning delta-v it will run out completely if being expended at 2x rate. You might be onto something there, I'll go look at the bugs section. Yea definitely sounds like leaky engines. Some of my early missile designs behaved exactly like that until I learned to keep burn times>5s and dV>3km |
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Post by the_Demongod on Dec 23, 2016 23:35:32 GMT
It was indeed a Fluorine/Methane missile but the issue turned out to be related to that delta-V bug mentioned above. The bug masked the root cause which was that I hadn't properly worked out the fuel mass ratios, so I was burning through all my Fluorine well before burning through all the Methane, and couldn't tell that something was up because the delta-V readout seemed fine. Thanks for all your help anyhow.
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Post by The Astronomer on Dec 24, 2016 1:11:33 GMT
I got the very same problem, and I think I was using the NTR...
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Post by shurugal on Dec 24, 2016 2:14:24 GMT
I usually get this with fluorine fueled small missiles... I think the explanation was that the acceleration was enough to force the fuel in the engine even without the turbopump doing anything. Try to decrease the acceleration if this is the case. that's silly, there's such a thing as a solenoid operated valve for a reason. |
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Post by amimai on Dec 24, 2016 2:32:44 GMT
Burn time>5
dV>3
Dem be me guidelines for a working missile...
if your missiles running out of dV increase those stats and they will behave again.
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Post by concretedonkey on Dec 24, 2016 9:10:16 GMT
I usually get this with fluorine fueled small missiles... I think the explanation was that the acceleration was enough to force the fuel in the engine even without the turbopump doing anything. Try to decrease the acceleration if this is the case. that's silly, there's such a thing as a solenoid operated valve for a reason. Explanation was not mine  . I have no idea where it came from, it was a while ago. As for silly I can't judge really, in this game I'm operating mostly on trial/error. Anyway decreasig acceleration worked for me. Could be the delta V bug, could be amimai's leaky engines. |
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Post by morrigi on Dec 24, 2016 9:20:52 GMT
How much acceleration do people think is causing issues?
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Post by concretedonkey on Dec 24, 2016 9:24:51 GMT
Well, trial and error . When I encounter the problem just decrease it untill it stops. |
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Post by ross128 on Dec 25, 2016 2:37:20 GMT
I'm not sure what the exact value is, but I know of the missiles I have made, the ones with >50 gs of acceleration have that problem and the ones with <10 don't.
As mentioned, mis-matched fuel ratios can also cause problems by confusing the guidance algorithm (it'll think it has more dV than it actually has, so it won't save enough fuel to actually complete the terminal burn). One way to tell that's happening, is you'll see missiles getting disabled for "out of dV" when they still have dV left.
Another difference between the two is acceleration problems manifest in the coast phase, they won't enter coast because they can't cut their engines. Fuel mix problems show up in the terminal phase, when the guidance algorithm mis-calculates its fuel reserves and burns out too soon.
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Post by shurugal on Dec 25, 2016 4:24:29 GMT
How much acceleration do people think is causing issues? the problem is not that missiles have too much acceleration; it is that they have too large a gimbal range along with high acceleration. The game does not fire thrusters at anything less than full power, and always uses maximum deflection on the gimbal. As a result, something small and light like a missile will make continuous over-corrections. The solution to this is to reduce your missile's gimbal angle until the turn-around time for the missile is greater than 1 second. I find values anywhere between 1 and 2 seconds give good results for high-thrust missiles. |
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. I have no idea where it came from, it was a while ago. As for silly I can't judge really, in this game I'm operating mostly on trial/error.
