[1.3.1] Ferram Aerospace Research: v0.15.9.1 "Liepmann" 4/2/18

[Van Disaster]

I think that bug has been known for a while. The cause less so.

I can remember that from a couple of years ago, I'm reasonably sure. As much as I can remember anything from a couple of years ago anyway.

[cantab]

OK, now I'm confused. I understand that on the Static Analysis page, the Cm graph should slope downwards for the plane to be stable in pitch.

On the Stability Derivatives page, the FAR wiki describes Mw as follows

Mw is the primary static stability parameter: it tells you whether the center of lift is in the correct position. If this is negative (red), the plane is going to rapidly depart in a backflip (or nosedive) at the slightest uncorrected disturbance. In mathematical terms, it's the first derivative of the pitching moment over normal velocity - i.e. angle of attack, effectively.

The Wiki contradicts FAR here, which colours it green when negative and the tooltip says that it *should* be negative.

Nothwithstanding the Wiki/FAR conflict, this sounds like Mw is basically the same thing as the slope of Cm. But now I have a plane with a firm negative slope of Cm, but at the same speed a slightly positive Mw - like 0.006 or so. So what's going on there?

Screenshots: https://flic.kr/p/ApZpEr

https://flic.kr/p/zsXARh

[ferram4]

Okay, so with that error? No idea, both run through the same exact simulation code. So, what's necessary to cause that to happen?

[Guest]

Okay, so with that error? No idea, both run through the same exact simulation code. So, what's necessary to cause that to happen?

It seems that when reverting a step the scaling of the graph is reset to default, but the graph calculations keep running correctly (ex. if I remove a wing I see lift curve lowering but the absolute values in the graph are misplaced).

After a randomly long while it scale normally again

[InfiniteAtom]

Windows 64 builds are VERY common, as 64 bit is better than 32 bit. Mods such as the newly updated b9 aerospace REQUIRE FAR or NEAR. If these disable on windows 64 builds, this means b9 aerospace can't be used on windows 64. That is not good. Please allow a option to run FAR or NEAR on windows 64 bit builds.

[blowfish]

Windows 64 builds are VERY common, as 64 bit is better than 32 bit. Mods such as the newly updated b9 aerospace REQUIRE FAR or NEAR. If these disable on windows 64 builds, this means b9 aerospace can't be used on windows 64. That is not good. Please allow a option to run FAR or NEAR on windows 64 bit builds.

64 bit Windows is fine. What is not supported is 64 bit KSP, which at this point only exists as an unofficial community hack.

[Beetlecat]

Windows 64 builds are VERY common, as 64 bit is better than 32 bit. Mods such as the newly updated b9 aerospace REQUIRE FAR or NEAR. If these disable on windows 64 builds, this means b9 aerospace can't be used on windows 64. That is not good. Please allow a option to run FAR or NEAR on windows 64 bit builds.

You'll find this to be a non-starter. In other news, B9 has been updated? Pre-release?

[tetryds]

@InfiniteAtom: this has been discussed to death and is not going to happen. Wait for KSP 1.1 update as it may have a stable w64 build, if it does mods won't restrict themselves.

Now there is nothing else to talk about that topic, so it should not continue to be discussed.

[Van Disaster]

On an unrelated note, is the issue with inconsistent behaviour from the analysis tools likely to be resolved. Simple things like reloading the craft, or making a change and then undoing it, have a habit of changing the reported aerodynamic behaviour. It makes plane design rather frustrating.

Did we ever discover if this was limited to the hangar? had one flight out of 15 by a BD AI drone ( a considerably more consistent pilot than me ) show some quite wonky aerodynamics.

[G'th]

Have a question and I haven't really seen it anywhere, but what exactly does the "DPCR" button do? The other toggles are pretty intuitive as to what they help you with, but DPCR isn't and I haven't been able to find anywhere that specifically explains what it is. I imagine it has something to do with Dynamic Pressure but I'm still not sure. (and just to clarify, I don't even need the toggles as the planes I have fly well without them. I'm just curious)

[Van Disaster]

It adjusts control deflection to account for changes in dynamic pressure, globally. If you want more fine grain adjustments then Dynamic Deflection does it per surface.

[G'th]

Okay interesting. So essentially it adjusts your CS' deflection to account for different situations then, which if I understand it means that you won't have too much control in any particular situation?

[Van Disaster]

I missed the keyword "range" after "control deflection". It's basically automatic gain for the controls so they adjust sensitivity to match dynamic pressure.

[wolfman29]

Hi there - anyone have any idea how FAR interacts with drag in water? I'm trying to build a seaplane using radial intakes (as I have before I installed FAR), but ever since I installed FAR, while my intakes still allow me to float, I can't seem to get past about 22m/s. Anyone have any ideas as to why this is? Could this be related to Better Buoyancy? I know that ferram designed both mods and designed them to be compatible, so I don't imagine Better Buoyancy could be the case. If this is an artifact of FAR, I think I will try to remove this "feature."

[ferram4]

Well, considering intakes aren't exactly the lowest drag part to use, it's probably that. Most important thing to do is to make sure it floats high in the water to minimize water drag, and then you should be able to get up to decent speeds; I've managed 100 m/s on the surface, though granted that was with 4 engines pushing me along, so with one or two you should be able to max out around 50 to 80 m/s, which should actually be near the expected top speed of a seaplane, tbh. Takeoff at 30 m/s should certainly be possible.

[Van Disaster]

@Wolfman: attempted to answer/continue your conversation twice, both times posts have been moved to the FAR thread in the craft exchange forum, so check over there.

[Van Disaster]

Ferram: I'm running fights for a tournament challenge at the moment, I'm trying to track down reasons why people's craft will break up from aero stress on my install when they're fine on other people's. We're all using out of the box settings for FAR and a minimal mod set ( BD Armory & dynamic deflection, and in my case a few aesthetic mods ), nothing which should affect part strength, and I started with a completely fresh install.

The only possibility I've been able to think of is I'm running on a 4.4Ghz i7, some of the others are using rather less powerful laptops and somehow I'm doing more physics calcs per frame - but I've no idea what is really going on internally when it comes to aero stress. There's nothing whatsoever in logs. Any ideas?

[Jagzeplin]

not sure if its FAR doing this but im having an issue with air resistance suddenly disappearing on kerbin below 27-28000 meters. the craft slows down normally as it enters the atmosphere up until that altitude then abruptly starts speeding back up and of course my chutes cant be used without them getting ripped off. its possible that it could be an issue with the big (2.5m) heat shield since it only happens on this one ship ive made which uses that. i remember having issues way back with the heat shields seeming to deactivate air resistance but then clicking jettison on them used to fix it. not so this time

Edited November 4, 2015 by Jagzeplin

[ferram4]

@Van Disaster: That would have no affect on the physics whatsoever. They are either running other mods that they are not telling you about or vice versa. Make sure that mod sets are identical or else you're going to have a very hard time replicating any issues.

@Jagzeplin: Well, then you need to provide logs and full reproduction steps for causing the issue. I have never seen this behavior, but constant reports of it leads me to the conclusion that it probably exists, but people need to tell me how to cause it.

[Jagzeplin]

@Jagzeplin: Well, then you need to provide logs and full reproduction steps for causing the issue. I have never seen this behavior, but constant reports of it leads me to the conclusion that it probably exists, but people need to tell me how to cause it.

i know this is a dumb noob question but how do you upload logs again?

[tetryds]

[...] but people need to tell me exactly how to cause it, without skipping any single step of their full play session, nor considering anything as irrelevant as that may be the cause of the issue, with a full report and an output.log.

Fixed it for you, just so to make it clear that "launched a rocket, went to orbit, reentered" is a meaningless report.

[Camacha]

Fixed it for you, just so to make it clear that "launched a rocket, went to orbit, reentered" is a meaningless report.

Reproduction steps without the ability to reproduce the problem are not reproduction steps. It is pretty clear

[paul23]

The shear forces (and resulting stress) really break my re-entry vehicles constantly. - a simple pod + FL-T800 + swivel engine "breaks" on the fuel tank while going sideways.... Any way to "strengthen" the tanks (at the price of mass of course)?

I like structural failures: but I wish I could adjust the strength so I can still do the things I want, just at a higher price.

[Van Disaster]

@paul23: Ferram wrote a nice mod called Kerbal Joint Reinforcement, which strengthens joints that really should be stronger.

Edited November 4, 2015 by Van Disaster

[ratchet freak]

The shear forces (and resulting stress) really break my re-entry vehicles constantly. - a simple pod + FL-T800 + swivel engine "breaks" on the fuel tank while going sideways.... Any way to "strengthen" the tanks (at the price of mass of course)?

I like structural failures: but I wish I could adjust the strength so I can still do the things I want, just at a higher price.

struts, you need more of them