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

[ferram4]

The first deflection setting is for total deflection under standard controls (pitch, yaw, roll) and the second is only for deflection when using flaps or spoilers. So what's happening is you're setting the flap / spoiler setting and it's not having any effect since you don't have the control surface set up as a flap or spoiler (and it doesn't seem like you want to do that).

So unfortunately, you're either going to need separate control surfaces if you need different amounts of pitch and roll control or you're going to have to try and find a happy medium with that control surface. Max deflection is for total control and can't be set for each control axis.

[Luckfish]

The first deflection setting is for total deflection under standard controls (pitch, yaw, roll) and the second is only for deflection when using flaps or spoilers. So what's happening is you're setting the flap / spoiler setting and it's not having any effect since you don't have the control surface set up as a flap or spoiler (and it doesn't seem like you want to do that).

So unfortunately, you're either going to need separate control surfaces if you need different amounts of pitch and roll control or you're going to have to try and find a happy medium with that control surface. Max deflection is for total control and can't be set for each control axis.

There are four sliders (per winglet, it doesn't matter if I have one or four winglets on the ship) per tweak menu. You're meaning that the second from the top is for flaps/spoilers, or that the bottom two are?

Also, when adjusting any of the sliders or toggling on/off the axis, when I go to another winglet and then come back, the settings I had left will randomly change. I've tried right-clicking the other winglet, right-clicking somewhere in the VAB (to close the tweak menu), etc. I've tried with symmetry both on and off. There seems to be no rhyme or reason as to when it reverts.

Edited February 18, 2014 by Luckfish
Image addition

[Mystique]

I was just building artillery shell styled unmanned Eve probe that is supposed to go in atmosphere on ballistic trajectory, aerobrake and then land on chutes. I built probe using B9 pack parts, it has long sharp nose, blunt stern and 2 winglets on sides to put CoL a bit behind CoM (no possibility to make screenshot right not, but it's pretty much like a flying torpedo). The problem is, when I tested it at Kerbin, it tends to flip backwards and go ahead with its stern, like heatshield equipped landing module of a regular rocket mission. This is a bad idea, because stern doesn't have much of heat shielding (and, what's more important, I want it to come down as designed, in style). I'm not aerodynamics expert, but shouldn't vessel tend to enter atmosphere with its sharp point (especially when I help it by directing heading to surface prograde marker)? Or is it increasing vertical speed that generates drag where I didn't expect it and it flips vessel?

[NathanKell]

Luckfish: you have two (or more) copies of Module Manager somewhere in GameData. Delete all but one (the one with the highest version number) and place that in the root of GameData.

[Camacha]

I built probe using B9 pack parts, it has long sharp nose, blunt stern and 2 winglets on sides to put CoL a bit behind CoM (no possibility to make screenshot right not, but it's pretty much like a flying torpedo).

If control is not a requirement, I would try to get the CoL as far from the CoM as possible. That should make it stable - in the good sense that it does not deviate from its course, and in the bad sense that it is hard to turn.

[camlost]

ferram, seems the stock RAPIER engine is causing too much drag.

[ferram4]

@Luckfish: I'm gonna say that Nathan's right on this one. There should only be one set of tweakables there, which means that something broke. Be more careful when dealing with mods next time.

@Mystique: Things don't necessarily enter pointy-end first; after all, on most manned reentry capsules the pointy end is at the back and it enters blunt-end first. Odds are what's happening is that the nose is too light for how big it is and the back of the vehicle is too heavy. You might benefit from just using a smaller nosecone.

@camlost: That's because of the node on the back, and the drag on it is high (just like on all the other engines with nodes on the bottom) to deal with stability issues. Nothing I can do about it unless rockets flipping like crazy again is on the table.

[Luckfish]

Luckfish: you have two (or more) copies of Module Manager somewhere in GameData. Delete all but one (the one with the highest version number) and place that in the root of GameData.

That was it exactly, thanks NathanKell & Ferram. Since finding and getting rid of the extra copy of MM, I have full control of my control surfaces again. With MechJeb ascent autopilot on, it seems that having no control surfaces (and a reaction wheel in the lower stage) was actually a little more controllable and stable, and produced a lower dV ascent.

One other thing I ran across in my testing: If I put the MechJeb part on the cone of the capsule, it raises the Center of Lift quite a bit...slightly higher than the CoM of the ship. If I move it down to the vertical side of the fuel tank just below the command pod, it barely changes the CoL from what the craft would have without the MJ part. It makes intuitive sense that altering the aerodynamic shape of the front surface of the craft would have a greater effect than altering the side, but I was just surprised at how much of a difference it made.

[a.g.]

ferram, seems the stock RAPIER engine is causing too much drag.

To add to what Ferram said: if you don't want/need that node, you can nuke it with a MM config, like I did to those B9 VTOL engines:

@PART[B9_Engine_VA1]
{
	!node_stack_bottom = DELETE
}

It makes intuitive sense that altering the aerodynamic shape of the front surface of the craft would have a greater effect than altering the side, but I was just surprised at how much of a difference it made.

It may rather be the orientation of the part: FAR emulates parts as cylinders and cones, and is rather sensitive to the orientation of the main axis of those that it guessed relative to the flow.

[colmo]

Oddball question - does FAR have any influence on how drag works in water?

If not, could it be added?

I understand air and water are both fluids, so there are some commonalities?

Edit: This was previously asked here -http://forum.kerbalspaceprogram.com/threads/20451-0-23-Ferram-Aerospace-Research-v0-12-5-2-Aero-Fixes-For-Planes-Rockets-1-7-14?p=616024&viewfull=1#post616024

P.S. I know someone who has worked on hydrodynamics, though he's not a KSP player - I can relay questions to him?

Edited February 20, 2014 by colmo

[AndreyATGB]

I really doubt making water act like water is something Ferram wants to do. The water is KSP is so weird and unrealistic I can't think of a way to fix it without effectively making your own from scratch. Would be nice, but I don't see it coming from outside of Squad since it's not something most people deal with.

[Dekker3D]

Personally, I'd like for the water to be Ferram'd as well. It'd make submarine style vehicles doable, and someone might be crazy enough to create a plane that can survive diving straight into the water... Not saying that this someone is me, of course.

[Imca]

Is there any way to make ASAS not bounce around like its on a bumpy road with FAR installed?

I love the improvments it makes planes amazing to fly, I just want some more stability

[ferram4]

Given the way that water currently works in KSP (at least based on my knowledge of it) I don't think that anything can really be done on my end to fix it. Also, fluid interfaces can be really, really nasty to work with, so that's an entire new bit of code to try and handle the switch from atmosphere to ocean.

@Imca: Fewer control surfaces. Reduce deflection of all control surfaces. As I've said time and time again (stuff that should come up in this thread if you search for it), SAS is not designed to deal with lots of control authority. It's simply not good as a controller for planes, and it never seemed to be designed for them anyway. If you can't design the plane to work around SAS, you'll have to just not use it.

[SpaceGremlin]

Try using the FAR roll and yaw levelers and manage pitch with the trim controls. Once the atmo thins enough turn the SAS back on (and alt + x to clear trim). SAS is not needed for flying at all in the lower atmo. It also seems that when I use procedural wings I get less SAS flapping. Not sure if its because it is inherently more stable of if I am just getting lucky with balancing the control authority.

[Motokid600]

Question. Im building an N1 themed launch vehicle with modular fuel tanks and StretchySRB which will make up each stages design and Im confident I can get a rocket to greatly resemble the N1. But before I begin I have a large concern. The effect FAR will have on my interstage design. As you know the N1 interstages were just.. struts. And correct me if im wrong, but it was to be a hot stage rocket. ( which id also like to replicate ). So I was just going to use a small 1.25 or 2.5 decoupler to connect the center engine to the top of each tank. Then run struts along the outside. ( You can actually make it look really good ). But since there will not be a fairing so to speak.. ( the top of each stage will be slightly conical ) will FAR cause this rocket to repeat history?

[ferram4]

It won't be as aerodynamic as a rocket with a standard interstage, but it should work. I would advise making the lower section of each stage conical, since the conical sections will make more drag than the cylindrical sections; by putting the conical section at the bottom of the stage it will be more aerodynamically stable than if it were placed at the top.

[Motokid600]

Cool thanks ferram. Both the top and bottom of each stage will be somewhat conical. It depends on the length of the engines I choose. I don't want the struts too long. And then it comes down to the fact that it needs to put about 400 tons into orbit including the 3rd stage which will eject this thing to Eve. Im going to need lots of very big, very powerful engines... should be fun lol.

EDIT: How would I go about putting a thousand tons into orbit with FAR? Im going for an Eve land and return. And.. is it even possible? I mean I have StretchySRB's so I can build to ANY size. But the base of the lander is id say 20 meters. So the top, 3rd stage of the lifter has to be 20 meters. I may have to abandom my N1 replica idea. It'd be over 60 meters wide at the base. And id need a hundred engines on the first stage.. Oi.. this project is turning into something else.

Edited February 23, 2014 by Motokid600

[celem]

So....I've been playing around a bit with a supersonic fighter-style thing. Love the design i've come up with, but I'm getting some stability issues you guys might help me diagnose.

The 'viper' in the SPH. It's mainly wing shapes and such I want you guys to look at. For those curious the tanks are KW, thermal turbojets and radiator from Interstellar.

Now this thing flies just fine in the lower atmosphere, however around 12-14km (900-1000ms) it starts to 'dutch roll' and then loses roll stability altogether (it will fly level if trimmed and left level. If roll occurs it does not self-correct, the roll surfaces currently seen are 'just' enough to reign in most rolls but a return to true stability/level-flight is rare). Several flights have ended with the craft inverting completely around this point in the climb (where its actually pretty stable).

Im starting to think I need to angle the wings from the root (anhedral/dihedral angles). Now normally i'd want dihedral to promote roll stability, yet when i look at many modern high-velocity aircraft im finding anhedral angles. The wing currently is 0 angled and emerges from the horizontal 'datum-line' of the fuselage.

Fore-canards are set to roll, Ailerons are the two small controls either-side of the aerospike, elevators are the large surfaces further toward the wingtips. On a related note: when using procedural control surfaces like this, should i angle the back edge of the control surface to run parallel to the back edge of the wing its attached to? Or should it be running perpendicular to direction of flight?

Ideas? How can I make this design more stable in the roll-axis?

Edited February 23, 2014 by celem

[S4qFBxkFFg]

@ferram4 Couple of questions, one of which may not even be FAR related:

I've been using the HGR-57 "Radish" pod (http://forum.kerbalspaceprogram.com/threads/60974-23-Feb-12-HGR-New-spherical-pod-available) and have noticed some strange behaviour on re-entry - if often orients itself pretty much side-on to the airflow instead of tail-first, sometimes its own reaction wheels are enough to rectify this, sometimes not. On one occasion, it was performing as expected above M1 before "flipping" to the side-on attitude when speed dropped below M1. More details here: http://forum.kerbalspaceprogram.com/threads/64897-Reconstruction-a-0-23-career-mode-story

One detail that may be relevant is that this pod has two attachment nodes (for 1.25m parts as well as 2.5m), one of which will normally not be used, and I saw in an earlier post that this could affect drag.

The question: is there something in this pod's design that would need tweaked to work with FAR, or is there something else that's more likely to be causing this behaviour?

The second question: does it make sense to build a swing-wing aircraft with FAR (using Infernal Robotics, or similar)?

[Agathorn]

@ferram4:

Would you be willing to add these functions to FARControlSys to allow kOS to access some fo the FAR flight data? Right now you have pretty much everything locked down behind private declarations so I can't really grab anything externally. I was trying to do as much as I could without having to ask you to change/add code, but with everything being private I can't even dynamically link to what I need.

Or if instead of adding these, if you could add a proper API for accessing data that would be useful to everyone that would be cool as well.

        public Double kOSGetMachSpeed()
        {
            return Double.Parse(mach);
        }
        public Double kOSGetEAS()
        {
            float densityRatio = (FARAeroUtil.GetCurrentDensity(vessel.mainBody, (float)vessel.altitude) * invKerbinSLDensity);
            return (vessel.srf_velocity.magnitude * Mathf.Sqrt(densityRatio));
        }
        public Double kOSGetAtmosphericDensity()
        {
            return (FARAeroUtil.GetCurrentDensity(vessel.mainBody, (float)vessel.altitude));
        }
        public Double kOSGetRelativeAtmosphericDensity()
        {
            return (FARAeroUtil.GetCurrentDensity(vessel.mainBody, (float)vessel.altitude) * invKerbinSLDensity);
        }
        public Double kOSGetTerminalVelocity()
        {
            return termVel;
        }
        public Double kOSGetOxygenIntake()
        {
            return intakeDeficit;
        }
        public Double kOSGetLift()
        {
            return Cl;
        }
        public Double kOSGetDrag()
        {
            return Cd;
        }
        public Double kOSGetDynamicPressure()
        {
            return q;
        }

[softweir]

@Celem: Modern fighters have anhedral wings in order to de-stabilise them (for high manoeuvrability), and use high-performance fly-by-wire systems to regain stability. We can't get the high-performance fly-by-wire in KSP, so we have to use dihedral wings or much larger tailfins. If a larger tailfin causes roll artifacts when yawing then using two - mounted on the engines and angled in - may be better.

You may find putting the small, rear ailerons towards the wingtips may help SAS / FAR to maintain a level flight. As far in as you have put them they don't contribute much. (Nor will the canards have much roll authority, might as well disable that.)

[DaMichel]

@celem: I'm no expert but i learned that a vertical stabilizer so close to the CoM is no good. Try to put it further back in order to give it a longer lever arm. If it doesn't help enough try making in bigger as well.

[celem]

@Celem:...[snip]...You may find putting the small, rear ailerons towards the wingtips may help SAS / FAR to maintain a level flight. As far in as you have put them they don't contribute much. (Nor will the canards have much roll authority, might as well disable that.)

Not quite sure why I didn't consider this one during design. The canards are gutless and work mainly as a secondary elevator, which I knew. I then didn't consider the length of the lever on those rear ailerons, which as you pointed out leaves me little roll authority.

Repositioned the control surfaces in the back, lost a bit of the over-zealous trailing-edge sweep on the wing-root to make that segment more delta, then lifted the swept tips to give me a little dihedral angle. Much more stable in that axis. I also took the opportunity to move the CoM backwards a bit, as shown its balanced as I'd balance stock or most mods, but this design loses no mass until orbital insertion and that CoM was giving hardcore mach tuck. (im used to some CoM drift before I even rotate from runway acceleration. This flies for free until 20km and 2kms thanks to the interstellar mod components.)

[Boamere]

Hey any reason as to why I'm getting severe nose diving (mach tuck) at about 320 ms, when above mach 1 my plane won't deviate from prograde: is it possible that my plane is too stable? if so how would I go about making it less stable? thanks

Edit: here's a pic to help

Edited February 23, 2014 by Boamere