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

[asmi]

@ferram, first of all, I would like to join others here to thank you for all the hard work you do which allows us to enjoy playing. I think I wouldn't be too far off if I'll say that the reason we all love your mod is not that it makes the flight hard, but because it makes it real. Simulation fidelity is the single most important aspect for FAR in my opinion. You know much more about aerodynamics than I ever will, so do what you think is right, and we all will just deal with it.

Also I would like to note if there is anything you need help with - just let me know and I'll do my best to make it happen. I'm not an aerospace engineer, so there isn't much I can help you with as far as physics part goes, but I am a software engineer so I could help with implementation side of things. I've noticed that you haven't incorporated the code that I've sent you - is there any problems with that? I've done some limited testing on my side, and it seemed to work OK...

Bottom line - there is no rush, so please take your time and make it real!

[jrandom]

Not to sound like a johnny-come-lately, but F.A.R. is one of my three key "won't play without it" plugins. I don't care how many bugs accidentally slip out into the wild, your hard work is vastly appreciated. Atmospheres in KSP just don't feel right without it.

Edit: Speaking of bugs, 9.5.51 seems to show an incorrect lift vector...

Edited July 29, 2013 by jrandom

[ferram4]

@NathanKell: I can look into that more, but I honestly don't know how much I can do without having to try and replace the stock parachute code. Especially since the parachutes should make some drag when they aren't deployed otherwise there would be a huge benefit to replacing regular nose cones with parachutes. I'll look into MechJeb's code a bit and see if there are any problems there; it might be adding drag that doesn't exist.

@asmi: I actually forgot to add your code... whoops.

[xclusiv8]

Is there a guide somewhere for building stable jets with this mod? I can build jets that fly but its always when approaching mach 1 that my aircraft plummit to the ground I understand that there are a lot of variables and i've tried to figure out all of them in the FAR CAS but without any luck.

[Van Disaster]

Hmm. I've managed to lose the CoL indicator completely now - I was trying to work out why it was pointing in all sorts of odd directions, so I started using stock wing parts in case it was mods and now it's disappeared.

Log is full of these:

[LOG 17:00:46.922] FAR Error: Aerodynamic force = NaN at Proceduralwing2(Clone)

[LOG 17:16:21.090] FAR Error: Aerodynamic force = NaN at wingConnector(Clone)

for *every* wing part I try. Modulemanager again maybe?

[finestgreen]

I'd love to know what all these numbers mean :-) Does anybody know of a good primer on real-life aerodynamics (online or reasonably priced kindle ebook) that will give me some hope of figuring it all out?

[DasPenguin85]

STUPID NEWB QUESTION ALERT!

Well, I'm only a newb to Ferram AR, and decided to try it recently - I spent most of the day yesterday trying to design super-sonic airliners with the B9 pack. One thing I noticed is that I can customize the functionality of the B9 control surfaces, however I cannot do this with the stock parts. So, my question is: Am I on a buggy version, or can you only customize the control surface functions on supported mod parts? Thanks!

[a.g.]

That suggests ModuleManager is not installed or working correctly.

[DasPenguin85]

That would be likely, considering I looked at that .dll and ignorantly exclaimed "Bah, I don't need this! It's not even in its own folder!"

The lack of installation specificity regarding this has probably led me astray, and I'm usually pretty good at RTFM.

Thanks!

[NegativePositive]

Hey ferram4 or any other experts out there, I'd like to know if the benefits of swept wings for transonic speeds are modeled.

I'm debating whether I should sweep my wing for my supersonic VTOL aircraft.

[Weatherman159]

Gah, running into rocket problems again. I'm doing my own take on the Apollo moon mission, but no matter what I do, at some point after launch the rocket tips end over end. I suspect it could be due to the CoM shifting up because fuel is burned, but there's really nothing I can do about that (other than building a short fat rocket instead of a tall thin one, but FAR rockets are supposed to be tall and thin). Help?

[Ralathon]

Gah, running into rocket problems again. I'm doing my own take on the Apollo moon mission, but no matter what I do, at some point after launch the rocket tips end over end. I suspect it could be due to the CoM shifting up because fuel is burned, but there's really nothing I can do about that (other than building a short fat rocket instead of a tall thin one, but FAR rockets are supposed to be tall and thin). Help?

Are you doing a proper gravity turn?

In FAR (And RL) you don't want to just flip 45 degrees at some point. You want to gradually tip over. You should never ever be pointing the rocket more than a few degrees from the prograde marker when inside the atmosphere.

If you're using multiple stacked tanks it also helps to drain the bottom one first. This means that as you burn the COM moves up, stabilizing the rocket.

[asmi]

I'd love to know what all these numbers mean :-) Does anybody know of a good primer on real-life aerodynamics (online or reasonably priced kindle ebook) that will give me some hope of figuring it all out?

There are very good explanations right inside the plugin - click "Help" (or "?") button and read it all carefully.

@asmi: I actually forgot to add your code... whoops.

Ahhh, it happens. Hope to see it in the next release then.

Edited July 29, 2013 by asmi

[ferram4]

@8clusiv8: What's happening isn't that your vehicle isn't stable enough; it's that it's too stable at supersonic speeds. The CoL shifts back a bit when moving from subsonic to supersonic flight, so a vehicle that needs a lot of control input to stay on course at subsonic speeds won't have the control authority to stay on course at supersonic speeds. Try shifting the CoL forward and adding more pitch control surfaces and see if that helps.

@VanDisaster: Make sure you've re-downloaded FAR 0.9.5.5; I uploaded the wrong dll by mistake the first time. If you've done that and the problem persists, could you post a craft with the issue?

@finestgreen: This online resource is decent and should be a good start; it's free as well.

@NegativePositive: The benefits and detriments of swept wings are modeled at all Mach numbers, so you should probably sweep the wings on your craft.

@Weatherman159: First, make sure that you're not going above an AoA of ~5 degrees during the ascent. Second, consider what Mach number your craft flips out at; as Mach number increases, a fin-less vehicle will become less stable. You may want to consider adding fins to the bottom of the vehicle. You may also want to consider adjusting the staging so that it doesn't stage while still deep in the atmosphere; staging can sometimes precipitate a loss of control.

[Yarbrough08]

@ferram4: I am making a cargo bay with built in solar panels and I noticed a bug with it... inside the cargo bay everything is shielded like it is suppose to be when closed, and unshielded when open. However, anything attached to it directly on the outside "freezes" while the cargo bay is closed. At least the cd, cl, and cm values on the right click menu freezes at whatever value they where holding at the time when you click to close the bay. What can be done about this? I love your mod and want to add compatibility to it. Like many of the other members here, I feel that it is absolutely essential to the playability of the game. Thanks for your hard work.

[NathanKell]

ferram, yeah, wouldn't want parachutes to be OP. It's just as it stands a rocket that can get to orbit without parachutes will fail if you launch a capsule (that is .1t under its rated capacity), but with setting stowedDrag to 0 it will _just_ make it, with less safety margin than designed. Hence why I suggest setting them all to 0 and not fixing the incompatibility (thus leaving us with some extra drag for chutes), as the least-work option that doesn't overly penalize parachute users.

[Autochton]

Is there a guide somewhere for building stable jets with this mod? I can build jets that fly but its always when approaching mach 1 that my aircraft plummit to the ground I understand that there are a lot of variables and i've tried to figure out all of them in the FAR CAS but without any luck.

The trick is, aerodynamics change pretty significantly as and after you pass the sound barrier. So for a supersonic plane to fly right, you need to build it such that it is stable in the subsonic, transonic (around Mach=1) and supersonic regime as well. The CAS can help with that, as you can put in numbers for the speed you want to do your calculations at. It would be grand if we could get something similar for a center of lift (and prospective center of drag as well), but as it is, you can derive a lot from the stability derivatives. Type in the numbers for the mach regime you want to test, run the numbers, and check signs on things against the suggestion in the mouse-over tooltip for the value.

[Torham234]

Lemme just join the cult and say I really, really love the FAR mod. It makes designing planes much better experience. And thanks for the update, now I can go back to the Space plane hangar...

[Sokar408]

How does this effect parts mods like B9?

[jrandom]

I've tried both the Spaceport and MediaFire links, and I'm still getting incorrect CoL display in 9.5.5 FYI.

Screenshots (all stock parts, same plane in both images)

Edit: Here's the .craft file.

Edited July 30, 2013 by jrandom

[Van Disaster]

@Ferram: I haven't managed to repro that issue yet after a re-install, the CoL marker is all sorts of wonky though as others are saying. I seem to remember that being a rather old bug too.

Seems I can build Mk4-based designs again without them failing to reach rotation speed...

[longhornchris]

The trick is, aerodynamics change pretty significantly as and after you pass the sound barrier. So for a supersonic plane to fly right, you need to build it such that it is stable in the subsonic, transonic (around Mach=1) and supersonic regime as well. The CAS can help with that, as you can put in numbers for the speed you want to do your calculations at. It would be grand if we could get something similar for a center of lift (and prospective center of drag as well), but as it is, you can derive a lot from the stability derivatives. Type in the numbers for the mach regime you want to test, run the numbers, and check signs on things against the suggestion in the mouse-over tooltip for the value.

There are a few things I've found that can help when dealing with the stability problem. My easiest to fly designs are canard designs, with the main wing aft of the COM with flaps on the main wing. I try to place the subsonic no-flaps COL right behind the COM but very close. Next I adjust the max flaps to ensure that max deflection moves the COL aft - if the deflection is too large it will push the COL forward and/or stall which is bad. Because the COL moves aft as you transition to supersonic flight, the I use the flaps to start with my COL aft when fully deployed. Don't forget to set the flaps to action groups so you can adjust them. While you are in the action groups it I've found it helps to remove your nose gear from the brake command.

Now, for the basic flight profile. The first thing is to set your flaps to max deployment. Takeoff however you prefer and gain some altitude, but keep an eye on your mach number. As your speed approaches mach .8 cut your rate of climb to increase your acceleration through the transonic range. Next, start raising the flaps. This takes some timing, but the idea is to shift the COL forward by raising the flaps while the transition to supersonic speeds so your COL stays in approximately the same location. Once you've reached Mach 1.2 or better resume your climb.

If you are going to use the analytical methods, remember that you have to adjust mach number, speed, and air density. Because all 3 are inputs you can create some non-nonsensical situations (ex. high mach number & low airspeed) where the stability derivatives don't make sense. It took me a few flights to figure out what speed/altitude I could hit the critical mach .8-1.2 range.

[Event Horizon]

KSP crashed and in the log file, I found this:

NullReferenceException

at (wrapper managed-to-native) UnityEngine.Component:GetComponent (System.Type)

at UnityEngine.Component.GetComponent[FARWingAerodynamicModel] () [0x00000] in <filename unknown>:0

at ferram4.FAREditorGUI.Update () [0x00000] in <filename unknown>:0

at ferram4.FAREditorGUI.ControlSurfaceAttributionGUI () [0x00000] in <filename unknown>:0

at RenderingManager.OnGUI () [0x00000] in <filename unknown>:0

(Filename: Line: -1)

[Zarenor]

ferram, I've been trying to track down an issue with FAR and displaying the CoL in KSP versions since 0.21. I've run out of ideas, I can't seem to display a CoL on any craft, stock parts, modded parts, whatever.

I have thousands of lines of FAR Errors in my output_log.txt similar to the following generated whenever I attempt to display the CoL in the SPH.

(Filename: C:/BuildAgent/work/7535de4ca26c26ac/Runtime/ExportGenerated/StandalonePlayer/UnityEngineDebug.cpp Line: 54)

FAR Error: Aerodynamic force = NaN

at structuralWing

(Filename: C:/BuildAgent/work/7535de4ca26c26ac/Runtime/ExportGenerated/StandalonePlayer/UnityEngineDebug.cpp Line: 54)

FAR Error: Aerodynamic force = NaN

at structuralWing

I do have the output_log saved where I tested with the stock SR-71B craft. Planes seem to fly okay, and the other calculations appear to work, but it seems that something in the CoL calculations is DivByZeroing or exploding to infinity, to generate NaNs.

[ferram4]

@Yarbrough08: Gah! The cargo-bay-shielding-parts-outside-the-bay-bug still exists... That will require me to mess with the code more. Mind posting a copy of the craft with the problem so I have something to work with?

@NathanKell: Sounds good. I'll look into setting things up properly for the next release.

@Sokar408: For part packs that don't include any wing parts nothing needs to be done; FAR will account for everything without any extra input. If the pack includes wing parts then it needs to be specifically set up for FAR or the wings will not function properly. B9 Aerospace's wing parts are set up to be compatible with FAR.

@Event Horizon: Did KSP crash in the SPH or VAB? Is that the only NullReferenceException in the log, or are there more? How close was that error to the crash?

@People having the CoL bug: Make sure that ModuleManager.dll is properly installed and is loading; make sure that the wings actually have FAR aerodynamics applied to them (try right-clicking on them in flight). Try the static analysis and see what the results are. I haven't been able to reproduce the issue on my end.