ferram4

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

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Hi guys, sorry to post obvious Noob questions, but I'm having a hard time finding a "manual" for FAR.

Most of the ingame controls and values are document nicely with help buttons, but the tweakables in the editor kinda leave me hanging

DEDC077F31201622E4938C0DAF4FE6A02CED2887

- I guess Pitch/Yaw/Roll % are the authorities in that dimension expressed as a maximum.

- What the hell is AoA % ???

- Ctrl Dflct is probably "Control Deflection", probably in ° . But what does it do?

- Spoiler is pretty clear

- Flap is also clear, but how do I activate that ingame? Is there a hotkey or do I need action groups? That'd be a problem, because I don't have unlocked them yet. 1.4 M Funds is a lot of money.

- Flp/splr Dflct is the deflection of the flap/spoiler in ° I guess. How does it relate to the various flap settings? Is setting 4 20°? Or is it 80°? Ok, I guess I just answered my own question. Also, why is 25° the maximum?

- Mass/Strength: I can adjust the wing strength?? Wicked. That's some level of control right there. I just hope the default is fine for most, because I have no idea whats best for my plane.

You are welcome to RTFM me, but I just haven't found a manual, that's why I'm asking. Cheers.

ps.: How do I add those bloody spoilers so people don't have to see the picture if they don't want to?

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Does mass/strength affect part connections? More specific - could I increase this value to prevent the tail being ripped from my craft?

- What the hell is AoA % ???

AoA means Angle of Attack, but what exactly this modifies I am not too sure.

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Hi guys, sorry to post obvious Noob questions, but I'm having a hard time finding a "manual" for FAR.

Most of the ingame controls and values are document nicely with help buttons, but the tweakables in the editor kinda leave me hanging

http://cloud-4.steampowered.com/ugc/45365732577761885/DEDC077F31201622E4938C0DAF4FE6A02CED2887/

- I guess Pitch/Yaw/Roll % are the authorities in that dimension expressed as a maximum.

- What the hell is AoA % ???

- Ctrl Dflct is probably "Control Deflection", probably in ° . But what does it do?

- Spoiler is pretty clear

- Flap is also clear, but how do I activate that ingame? Is there a hotkey or do I need action groups? That'd be a problem, because I don't have unlocked them yet. 1.4 M Funds is a lot of money.

- Flp/splr Dflct is the deflection of the flap/spoiler in ° I guess. How does it relate to the various flap settings? Is setting 4 20°? Or is it 80°? Ok, I guess I just answered my own question. Also, why is 25° the maximum?

- Mass/Strength: I can adjust the wing strength?? Wicked. That's some level of control right there. I just hope the default is fine for most, because I have no idea whats best for my plane.

You are welcome to RTFM me, but I just haven't found a manual, that's why I'm asking. Cheers.

ps.: How do I add those bloody spoilers so people don't have to see the picture if they don't want to?

* The tweakables are generally not measured in degrees.

* You can see what the settings do in the SPH if you run an analysis with them activated (i.e. use one of the FAR analysis screens with the "spoilers on" button ticked, and you'll see the spoilers deflect).

* Pitch/yaw/roll: usually you want to set a control surface to do one thing only. Set elevators to 100% pitch and 0% yaw/roll; rudders to 100% yaw and 0% pitch/roll; etc.

* Control Deflection is the maximum range of a control surface; think of it as the throttle limiter for your elevators/ailerons/etc. Wind it down if the plane is overly twitchy, wind it up if you're struggling to get it to do what you want it to.

* Flap/spoiler in FAR doesn't mean quite the same thing as flap/spoiler in reality. In FAR, both flaps and spoilers can deflect up or down; spoilers default to up, flaps default to down, but both of them can be set to negative values to deflect the other way. The key difference is that spoilers use a single action group to toggle between full deflection and no deflection, while flaps use a pair of action groups to deflect more or less in a four-step range. Spoilers default to being linked to the brakes action group, but you don't need to leave them there. Setting a control surface as both a flap and a spoiler doesn't work; it has to be one or the other.

* AoA is a bit complicated to explain, but it's a control surface setting that causes them to react to the plane's Angle of Attack (the angle between where the nose is pointing and the direction in which the plane is actually moving, shown by the surface prograde vector). It's what you'd use if you wanted a control surface to stay parallel to the airflow regardless of how hard you pull the nose up.

* Wing mass: default strength of 1 represents fighter-strength wings: almost unbreakable, but very heavy. 0.5 is plenty strong enough for anything that a sensible pilot should do; 0.25 is strong enough to go to space if flown carefully. The mass tweakable does affect connection strength.

Edited by Wanderfound

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Farrem4,

Got a serrious question for you about FAR.

So I was reading about a few things on aircraft, trying to answer a question I had about the MiG-31 and why it had these fin like things on the middle of the wings. And I had seen them before on other aircraft that were nowhere near as fast. So when I found my answer I discovered information about the "Wave Drag" affect. So I am still trying to figure out how all that works and I was wondering is that modeled in FAR?

If so I have something else I can learn and design into new designs to make them FASTER!!!!!!

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Speaking of AoA(%) on control surfaces, I started to experiment with those, and it is quite usefull to fine tune pitching moment (Cm yelow line on FAR graph - check link in my signature if you are not sure what I'm taliking about). There is small bug with those however. In flight everything behave as should, but there is problem on runway before taking off.

I have set AoA to 100% on my elevators on tail. Tail horisontal wings are set on angle to pitch tail down and in that way pushing nose up. Plane is designed in a way that nose is pitching down on runway until take off. While I prepare plane to take off, I have activated brakes/spoilers. At that moment elevators go crazy. Elevator control surfaces moves randomly pitching up/down and doing that quite fast.

Looking at FAR flight data it seems that FAR can't determine properly AoA, numbers jumping from +5 to -90 AoA, it is hard to read them properly. Once I start engines and plane starting to roll on runway AoA numbers become normal and elevators starting to behave properly. Solution could be to disable AoA feature until plane gain some speed like 10-20 (m/s) and also should be disabled while plane is in space. There is no use of that outside of atmosphere and just causing unwanted CPU drain.

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Odd thing I've noticed with the latest version of FAR, it seems I'm no longer able to create horizontal control surfaces that react to yaw inputs (split-ailerons). Setting the slider to -100% or 100% yaw does not cause them to react visibly to inputs. Is this a bug, a bad install on my end, or working as intended?

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Odd thing I've noticed with the latest version of FAR, it seems I'm no longer able to create horizontal control surfaces that react to yaw inputs (split-ailerons). Setting the slider to -100% or 100% yaw does not cause them to react visibly to inputs. Is this a bug, a bad install on my end, or working as intended?

It works fine with me. Put only yaw to 100%, set others to 0% (not to -100% !). You may also want to set Control Deflection to higher value to be able to notice difference when you press (A,D) keys. It is easier to notice on bigger control surfaces then smaller ones.

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Why did you clip the heat shield into the bottom of the pod and confuse FAR? Why did you add a heat shield when the MkI pod has one built-in anyway?

Hell, how did you even manage that, I fixed that particular clipping-induced bug, why is it coming back?

This drag issue persists with or without the DRE heatshield, as noted by Zilentification as well :(

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Yeah, I'm seeing it too, no clipping either. Just add some mass to the pod or come in a bit too steep & you'll miss the 'chute safe zone :(

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@People having drag issue with Mk1 pod without DRE heat shield: I cannot reproduce the issue; all my reentries result in the pod slowing down to 180 m/s at 5 km. Wipe your FAR folder completely and reinstall it, following the instructions completely. No mod managers of any sort, period.

@Funeh: ModuleManager is included in the FAR download, as it is a hard dependency.

@Hodo: No, those are wing fences, and aren't there to reduce wave drag. The swept wings themselves reduce wave drag, and yes, it is modeled in FAR, that's what supersonic drag is mostly about.

The wing fences are there to reduce a nasty effect of swept wings called spanwise flow; when wings are swept, the airflow from the more forward part of the wing drifts towards the more rearward part of the wing, encouraging the wing to start stalling there. When the wing does start to stall, that causes it to pitch up noticeably as lift is lost from the most rearward part first (look up "Sabre Dance"). If it's a conventional rearward swept wing as well, you're also looking at the ailerons stalling and losing roll control. The wing fences are placed there to block the spanwise flow and prevent that from happening, at the cost of adding a bit more drag. There are other methods of implementing this, such as the dogtooth notch on the leading edge of the F-4 that causes a vortex to form at high AoA to block the flow, or the use of active boundary layer control to prevent stall entirely.

Unfortunately, FAR does not model wing fences, the dogtooth, or active boundary layer control.

@Matrix Aran: They were never possible under the current scheme.

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@Hodo: No, those are wing fences, and aren't there to reduce wave drag. The swept wings themselves reduce wave drag, and yes, it is modeled in FAR, that's what supersonic drag is mostly about.

The wing fences are there to reduce a nasty effect of swept wings called spanwise flow; when wings are swept, the airflow from the more forward part of the wing drifts towards the more rearward part of the wing, encouraging the wing to start stalling there. When the wing does start to stall, that causes it to pitch up noticeably as lift is lost from the most rearward part first (look up "Sabre Dance"). If it's a conventional rearward swept wing as well, you're also looking at the ailerons stalling and losing roll control. The wing fences are placed there to block the spanwise flow and prevent that from happening, at the cost of adding a bit more drag. There are other methods of implementing this, such as the dogtooth notch on the leading edge of the F-4 that causes a vortex to form at high AoA to block the flow, or the use of active boundary layer control to prevent stall entirely.

Unfortunately, FAR does not model wing fences, the dogtooth, or active boundary layer control.

Outstanding.

Learning something new today. So I have noticed the nasty affect of some of my delta wing designs having a yaw stability issue at .35mach at sea level, and it gets progressively worse up to mach 1.5, then it drops off and becomes amazingly stable, I am talking -9+ around mach 2 and higher up at 20km.

Like this craft from .25 had that problem up till around mach 1.2 then it dropped off and became quite a joy to fly.

zwIwuGk.jpg

And my Mig-21 knock off SSTO works about the same except it is stable at all speeds.

ynZSnIr.jpg

Why is it that true delta wing designs have this issue more than the wing designs of the second craft?

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@People having drag issue with Mk1 pod without DRE heat shield: I cannot reproduce the issue; all my reentries result in the pod slowing down to 180 m/s at 5 km. Wipe your FAR folder completely and reinstall it, following the instructions completely. No mod managers of any sort, period.

Could this have to do with Vens Part revamp altered model for the pod and the way that FAR calculates the drag for the model? That's the only thing I can think of.

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Nope, because I use Ven's parts, and I don't see the problem. Reinstall manually and see if that fixes it.

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@Ferram4 is it possible under your new water model will submersibles be possible?

And on the flight subject.

I have designed a few swing wing designs, that use variable geometry swing wings with IR and Procedural wings. I never noticed a change in the display readouts for when the wings are in their straight possition and when they are in their max sweep possition. If anything the CoL shifts back and makes the nose heavier, as expected but had not noticeble effect on the L/D.

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I've been having odd issues with re-entry speeds as well (way too fast as you guys have said). I'll also test it out later with and without DRE to see what's going on.

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@Matrix Aran: They were never possible under the current scheme.

I figured as much, the last time I had tried them was 0.14.3

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Another bug report:

The stability derivates are changing depending on the flap settings of the previous calculation :confused:

http://imgur.com/a/WlNgU

Test Craft (all stock parts)

This bug is still present in FAR 14.5.1. Noticed on AoA value for leveled flight. Calculated with 0 flaps increment, folowed by flap 3 twice in a row and back to 0 flap increment (2 times pressed on simulation). On each simulation I got different AoA values.

Another bug that I have noticed is that FAR calculations are not the same when I design craft, test craft on runway and then reverted flight back to hangar.

First calculation shows drag close to zero (red line) and L/D (green line) close to 2. When I reverted flight to hangar and made the same calculations, drag red line was well above L/D green line.

I will try to make few more test to pinpoint exact mod dependencies and steps to reproduce bug. Still don't have much mods installed and on mentioned craft I have used adjustable landing gear, MechJeb embeded in command cockpit and kibal part from station science mod for heavy payload inside cargo bay.

Just posting it here for other to pay attention and try to reproduce bug.

EDIT:

Deleted ALL mods. Only FAR V14.5.1 left. Started game and loaded previously well designed plane in SPH editor.

FAR graph shows this:

dw0wH5D.jpg

Reattached same wing on the same spot and I got proper FAR graph:

qfzUzNd.jpg

Edited by kcs123

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Edit: I'll try shallower re-entry angles. I know my trajectory was a little steep as I was doing a crude sub-orbital test. I just assumed that I could still slow down.

Edited by Czerky
Retraction

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That is because the craft is officially a lawn dart at that point. You may want to deploy a drogue chute to slow down once your below 15km. This way you can get down below supersonic speeds before you try and deploy your main chutes.

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That is because the craft is officially a lawn dart at that point. You may want to deploy a drogue chute to slow down once your below 15km. This way you can get down below supersonic speeds before you try and deploy your main chutes.

Unfortunately you can't do that in career mode when you only have one chute available to you.

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Czerky: the issue which immediately suggests itself is that you are taking an extremely steep reentry path. Something like 100km x 35km is typical, but it looked like you were reentering at an almost 45 degree angle, suggesting a periapsis buried deep, deep inside Kerbin.

That is because the craft is officially a lawn dart at that point. You may want to deploy a drogue chute to slow down once your below 15km. This way you can get down below supersonic speeds before you try and deploy your main chutes.

Drogues would be destroyed just as much as main chutes if deployed at 450 m/s. FAR would make DRE unplayable if you couldn't get to ~250-300 m/s just on the capsule.

Granted, I still suspect Czerky's problem is his reentry profile: he was traveling well above terminal velocity, suggesting he had carried a lot of orbital velocity along with him, instead of killing almost all his orbital velocity in mid-atmosphere.

EDIT: Saw the "suborbital" bit. Suborbital reentries always freak me out because there's less control of vertical velocity. They're probably harder than orbital reentries.

Edited by Starman4308

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Okay, so I decided to stop being lazy and test with a less crazy descent (~110x35). Variables are the same except my landing location ended up being about 600m ASL. Here are the results w/ FAR data:

Javascript is disabled. View full album

I haven't actually played with FAR in a while, so I'm not sure if these numbers are normal (I think they're ok?). Just FYI, I'm playing with stock Kerbin. Impact velocity at 600m ASL was 380m/s.

Edited by Czerky

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As a datapoint, I've been having no trouble slowing down during FAR/DRE reentries, even during near-vertical suborbital hops up to 150km or so. Are you folks keeping the heatshield side pointed the right way? Are you brinng down more than just a capsule?

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