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

[jrandom]

As the Mach number increases, the effectiveness of your wings decrease, your vertical tail is already very small, it just gets to a point where it's useless.

Try at least doubling them.

I figured that was the case. Thanks!

[Kitspace]

That is quite a large update!

Thank you!

By the way why the stock gimbal range increase?

[Motokid600]

I was having so much fun cruising through the atmosphere last night. Loving nuFAR Ferram amazing job. So much fun. However something really strange happened. I wanted to see how fast this particular craft could go.

And once the craft reached top speed I'd say around 340m/s or so... My roll controls flipped. Yaw was fine as was pitch. But out of nowhere q ( left roll ) became right roll. And E became left roll. Nearly wrecked the craft until I figured out what was going on.

Then once I slowed down they switched back. Now I segregate control surfaces. So I only have a pair just for roll, pitch and yaw. So what could have happened that my roll controls reversed like that at speed?

[Surefoot]

The SR-71 in X-Plane does not appear to have a SAS button (or I just haven't figured out where it is) and it's scary dangerous to fly w/out it.

On the real thing it was on the right hand side control panel, upper part. Look at this (scroll up a bit for a picture of the control panel).

That book also describes SAS and flight controls, and there are more books (written by former pilots) that are highly interesting on the subject. The details on aerodynamic design will give you a lot of ideas for Kerbal+FAR

[ratchet freak]

I was having so much fun cruising through the atmosphere last night. Loving nuFAR Ferram amazing job. So much fun. However something really strange happened. I wanted to see how fast this particular craft could go.

And once the craft reached top speed I'd say around 340m/s or so... My roll controls flipped. Yaw was fine as was pitch. But out of nowhere q ( left roll ) became right roll. And E became left roll. Nearly wrecked the craft until I figured out what was going on.

Then once I slowed down they switched back. Now I segregate control surfaces. So I only have a pair just for roll, pitch and yaw. So what could have happened that my roll controls reversed like that at speed?

wing flex, when the aileron deflects it will apply a force to the trailing edge of the wing which depends on the airspeed. If that force is large enough then it will flex the wing to move the angle of attack to the opposite direction and the change in lift will override the force of the control surface. This is similar to the operation of a trim tab.

You can fix it by moving the ailerons closer to the root of the wing where it won't flex as much.

[Surefoot]

I was having so much fun cruising through the atmosphere last night. Loving nuFAR Ferram amazing job. So much fun. However something really strange happened. I wanted to see how fast this particular craft could go.

And once the craft reached top speed I'd say around 340m/s or so... My roll controls flipped. Yaw was fine as was pitch. But out of nowhere q ( left roll ) became right roll. And E became left roll. Nearly wrecked the craft until I figured out what was going on.

Then once I slowed down they switched back. Now I segregate control surfaces. So I only have a pair just for roll, pitch and yaw. So what could have happened that my roll controls reversed like that at speed?

That's control reversal: http://en.wikipedia.org/wiki/Control_reversal

One cause is wing deformation. Are you using KJR ?

By the way why the stock gimbal range increase?

Ferram mentioned it a few pages ago, it's to prevent all your rockets from flipping when a little gimbaling goes a long way

Edited May 10, 2015 by Surefoot

[delta534]

What would be the best way to exclude a model of a part from being included as part of the overall mesh geometry. Right now the warp bubbles on Roverdude's warp drives are being included and are screwing up the aero.

[kcs123]

I was fine tuning plane, transition graph was showing correctly. I messed up something and deceided to reload craft in SPH. After reloading transition graph is showed upside down far from the craft.

Not long after that game crashed with folowing bug. I will try to reproduce same thing with latest release as it seems github is updated once again while I write this post.

(Filename: C:/buildslave/unity/build/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 56)

Updating Space Plane Mk2 B9PW V100 06

(Filename: C:/buildslave/unity/build/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 56)

Updating Space Plane Mk2 B9PW V100 06

(Filename: C:/buildslave/unity/build/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 56)

NullReferenceException

at (wrapper managed-to-native) UnityEngine.Transform:INTERNAL_get_worldToLocalMatrix (UnityEngine.Matrix4x4&)

at UnityEngine.Transform.get_worldToLocalMatrix () [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARAeroComponents.FARAeroSection.PredictionCalculateAeroForces (Single atmDensity, Single machNumber, Single reynoldsPerUnitLength, Single skinFrictionDrag, Vector3 vel, ferram4.FARCenterQuery center) [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARGUI.FAREditorGUI.Simulation.InstantConditionSim.GetClCdCmSteady (FerramAerospaceResearch.FARGUI.FAREditorGUI.Simulation.InstantConditionSimInput input, FerramAerospaceResearch.FARGUI.FAREditorGUI.Simulation.InstantConditionSimOutput& output, Boolean clear, Boolean reset_stall) [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARGUI.FAREditorGUI.Simulation.SweepSim.AngleOfAttackSweep (Double machNumber, Double pitch, Double lowerBound, Double upperBound, Int32 numPoints, Int32 flapSetting, Boolean spoilers, .CelestialBody body) [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARGUI.FAREditorGUI.StaticAnalysisGraphGUI.BelowGraphInputsGUI (FerramAerospaceResearch.FARGUI.FAREditorGUI.GraphInputs input) [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARGUI.FAREditorGUI.StaticAnalysisGraphGUI.Display () [0x00000] in <filename unknown>:0

at FerramAerospaceResearch.FARGUI.FAREditorGUI.EditorGUI.OverallSelectionGUI (Int32 windowId) [0x00000] in <filename unknown>:0

at UnityEngine.GUILayout+LayoutedWindow.DoWindow (Int32 windowID) [0x00000] in <filename unknown>:0

at UnityEngine.GUI.CallWindowDelegate (UnityEngine.WindowFunction func, Int32 id, UnityEngine.GUISkin _skin, Int32 forceRect, Single width, Single height, UnityEngine.GUIStyle style) [0x00000] in <filename unknown>:0

(Filename: Line: -1)

Updating Space Plane Mk2 B9PW V100 06

(Filename: C:/buildslave/unity/build/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 56)

Updating Space Plane Mk2 B9PW V100 06

Sorry if it is already known issue, but stability derivates seems not showing proper numbers. I have tried to recreate some of my crafts from V0.90. I have created plane with similar shape and wing span as in KSP 0.90 as close as posible. In 0.90 at 0.35 mach and 0 km plane was stable and capable to lift off with 2-3 AoA degree. In KSP 1.0 stability graph shows that plane can't take off. For level flight at 0.35 mach (or 120 m/s) at sea level, needed AoA can't be calculated. Despite this on test flight craft behave very close as it was in V0.90, starting to take off effortless at 100-110 m/s, close as it was designed for.

Don't know if it is of any help, but based on my previous designes, it seems that I need to put 0.20 mach higher speed in stability graph to get closer results. Even with higher speed than I actualy need, stability graph is qrong within 10-15 AoA degree when comes to calculating level flight. It is only based on previous expirience with building crafts with FAR, so numbers are roughly estimated, take it with grain of salt.

[amankd]

i read the responce about how getting accurate ground effect wouod be very hard unless you could figure out how to treat the wings differently but would it not be possible to create a basic mod that is a rough simulation based on altitude to terrain? it would be far from perfect but it would allow for the creation of WIG craft, with maby a slider for control depending on the size and wing area of the craft? i dont know how it would work but it is just a possibility on how to get the possibility, if not total accuracy of wig craft, just an idea but i would love if it could work,

P.S is there any way to take the dimentions displayed in the editor and provide them a rough approximation of scraft size? or maby taking into account wing area if it could be calculated?

[Tarheel1999]

i read the responce about how getting accurate ground effect wouod be very hard unless you could figure out how to treat the wings differently but would it not be possible to create a basic mod that is a rough simulation based on altitude to terrain? it would be far from perfect but it would allow for the creation of WIG craft, with maby a slider for control depending on the size and wing area of the craft? i dont know how it would work but it is just a possibility on how to get the possibility, if not total accuracy of wig craft, just an idea but i would love if it could work,

P.S is there any way to take the dimentions displayed in the editor and provide them a rough approximation of scraft size? or maby taking into account wing area if it could be calculated?

IIRC Ferram has stated in the past that ground effect was computationally intensive and provided a negligible benefit.

[amankd]

IIRC Ferram has stated in the past that ground effect was computationally intensive and provided a negligible benefit.

the benifit in this gase is the possibilityof WIG craft, for which i have a certain passion, from what he said before accurate calculation is very difficult, but i am looking for approximate simulation, somthing that will make wig craft work, similarly to how the old aero model was made so that aircraft would work, somthing that will increase lift and decrease drag as you near the ground

[ferram4]

@delta534: If it's not visible when the part loads, it won't be voxelized. So in flight, that will not be an issue. I am working on a system to handle this slightly smarter than what it currently requires, but until then, it shouldn't be an issue in flight.

@kcs123: "Transition Graph?" I do not know what you're talking about.

Also, to the best of my knowledge, the Stability Derivs are correct. Units are correct, and so the math should be correct. It may have difficulty converging close to the stall point, and certainly won't if it requires some amount of vertical thrust to take off, but I haven't seen anything strange, tbh.

@amankd: If you're willing to take only approximations, just go with stock for now. I hear that their wings are stupidly floaty at low speeds, which should be exactly what you're looking for.

If I'm going to add it, I'm doing it right. If I can't do it right, I'm not going to add a hack.

Edited May 10, 2015 by ferram4

[NoClass]

the benifit in this gase is the possibilityof WIG craft, for which i have a certain passion, from what he said before accurate calculation is very difficult, but i am looking for approximate simulation, somthing that will make wig craft work, similarly to how the old aero model was made so that aircraft would work, somthing that will increase lift and decrease drag as you near the ground

Doesn't ground effect have a huge impact for takeoffs and landings for all craft?

[amankd]

Doesn't ground effect have a huge impact for takeoffs and landings for all craft?

yeah it does, it was first noticed by airline pilots who noticed their craft being floaty and hard to slow when landings, i would use stock aero but i would prefer a sharper change, one not based on speed, i cannot unfortunatly code as yet but i was thinking maby a plugin that increased the lift/drag multiplyer in the debug and reduced the drag multiplyer, i didnt know of anywhere else to look for an aero dynamic plugin, i tried starting my own thread but nothing came of it... i was not thinking of necessarily adding it into FAR as that has a stearling reputation for excelent accuracy, but maby a seperate mod, to augment the stock aero to makee a noticable difference when close to the ground at any speed

[B15HOP_xmen]

It's called Area Rule and knowledge of this allows you to decrease supersonic wave drag in nuFAR too. Before the concept of Area Rule, jet fighters had trouble breaking the sound barrier. Once those curvy coke bottle fuselages started appearing, they progressed quickly over a number of years to Mach 2 and beyond

In other news, I just finished my first designed-for-nuFAR aircraft based off a famous Gerry Anderson craft from Captain Scarlet.

This replica has Jeremy Clarkson approved levels of face-tearing acceleration and has a top speed of Mach 3.1. Thanks to nuFAR it is also stable enough to fly without SAS, although leaving it on is recommended for beginners.

Fly with DPCR at 9.0, fudge the number at pilot's discretion. Tweakscale required, as original design had many tiny but functional parts that would be omitted otherwise.

Angel Interceptor craft file on KerbalX:

http://kerbalx.com/crafts/2234

I tried your craft and it doesn't seem to work (installed the other mod).

Flipped straight up and then eventually killed itself with sheer G force changes.

[jrandom]

Huh. Stable flight at Mach 4 requires some hefty vertical surfaces. Go figure.

Javascript is disabled. View full album

[ferram4]

@kcs123: Nope, I'm wrong on the Stab Derivs, I was being stupid. Go figure. Fixed in my dev build.

@jrandom: Build them with some AoA built in. That's what the X-15 did (essentially) with its wedge tail. Also, maybe mount them even further back?

[B15HOP_xmen]

I built my first plane using the yellow cross section curvature guide to help minimize wave drag (and a little bit of area rule, but not much since I don't have Proc Parts installed yet), and this thing just screams through the air. (Previous designs where I didn't pay attention to the yellow curve had trouble pushing past Mach 1, even with more engines. Yay phyics!)

As I cross the Mach 2.5 boundary (or so, I wasn't paying close attention -- neighborhood of 700m/s at 12-13km) I lose all yaw control. What specific effect am I hitting, and do I just need taller yaw fins/controls to combat that? I'd like to push this thing up to Mach 3.

http://imgur.com/a/DJcYZ

Your craft effectively tramlines. Some of my early craft had the same problem. By tramline I mean locks into prograde and doesn't want to change direction. It's mostly due to it's arrow shape of the craft, being like a dart or an arrow. This can be a good thing as you really don't want to be changing direction quickly at high speed anyway. You just need a bit more turn speed and less arrow. There is a balance between too much turn speed and not enough.

[BudgetHedgehog]

Did you do this?

If so, I love you.

[NoClass]

yeah it does, it was first noticed by airline pilots who noticed their craft being floaty and hard to slow when landings, i would use stock aero but i would prefer a sharper change, one not based on speed, i cannot unfortunatly code as yet but i was thinking maby a plugin that increased the lift/drag multiplyer in the debug and reduced the drag multiplyer, i didnt know of anywhere else to look for an aero dynamic plugin, i tried starting my own thread but nothing came of it... i was not thinking of necessarily adding it into FAR as that has a stearling reputation for excelent accuracy, but maby a seperate mod, to augment the stock aero to makee a noticable difference when close to the ground at any speed

It would be nice to have, allowing slightly easier takeoffs for heavier planes, but I figure if ferram hasn't added it to FAR yet, then it's more complicated than it seems.

[amankd]

It would be nice to have, allowing slightly easier takeoffs for heavier planes, but I figure if ferram hasn't added it to FAR yet, then it's more complicated than it seems.

yeah from what he said before you have to treat wings differently and then mirror the vortecis againsgt the ground, but he cannot figure out how to teat the wings differently, i was sorta looking for a stand alonw mods that ust increased linft and lowered drag near the ground,so this was possible

[ferram4]

@Obsessed: Aye, that's me. Even changes significance between VAB and SPH; it's a warning in the VAB (because normally, it just calls for more boosters there) and a critical issue in the SPH (because it tends to limit you to M < 1).

@amankd: It's figuring out, "is this entire section of the vehicle a wing?" for the purposes of it. Not a simple task. Once that's taken care of though, it should be relatively straightforward to get ground effect in. It's just a multiplier to lift and drag, tbh.

[jrandom]

Build them with some AoA built in. That's what the X-15 did (essentially) with its wedge tail. Also, maybe mount them even further back?

I'm a little fuzzy on what the AoA control (angle-of-attack, yes?) actually does. I didn't see any visual changes. And what does that mean for tail fins?

As far as the mounting spot, I used the fine-tune translation control to place them in that exact spot to keep my center of lift riiiight where I wanted it. If I moved them even a hair back from that spot, the CoL jumped back far enough that it would have mucked up my pitch authority. That thing is on the raggedy edge of flyability, and definitely doesn't have enough lateral wing area (unless you like landing at 200m/s). The other side of the coin is it can fly at Mach 3.8 for an hour on a single turbojet.

Edited May 10, 2015 by jrandom

[amankd]

@ferram4 can you not use the lift generated by the part as an indication? if the part has a lift form in the config then treat it as a wing?

as a simplistic ideai was thinking that maby a pllugin to eddit the debug menue, where you can multiply up lift and drag and then multiply down drag could be a possible place to start? (depending on altitude i mean ) if the debug has enough effect

[kcs123]

@kcs123: "Transition Graph?" I do not know what you're talking about.

Sorry, new Cross-Section Area curves graph, under Transonic design tab.

English is not my native language, and i was thinking about subsonic to supersonc speed transition that is related to Cross-Section Area curves.

Anyway, didn't happened agaibn with latest github release and Cross-Section Area curves shows properly.

Well, for my craft it shows ">0" AoA for 0.35 mach at sea level on Kerbin - level flight. However craft is more than capable to take off with ~5 AoA degree.

It also shows some red numbers, but craft is actualy pretty much stable in flight. If I recall corectly someone mentioned that stability derivates were WIP prior nuFAR relese.

That is reason why I asked if those are correct or not. I was not sure due to craft behaviour.

Edit:

Just found another answer few posts below that I was not that crazy afterall. Redownolading github release again.

Thanks.

Edited May 10, 2015 by kcs123