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

[Crzyrndm]

1. Do wings in FAR have "multiple areas"? A front, back, middle? Or are they counted as ONE part. Because that would mean - make your wings out of many parts so the wing can stall partially instead of stalling the whole thing.

2. I don't really understand how stalling the forward wing earlier will help the plane.

1) When ferram4 says forward surface, he means that if you have two+ seperate wing sections, the foremost one is the one you want to have stall first (ie. stall order should be: canard, main wing, tail).

2) When a surface stalls, it suddenly loses a significant amount of lift (it's not producing zero lift, just an awful lot less than when airflow is not seperating from the wing surface). If that surface is foward of the CoM, then the crat has a reduced pitch up moment and thus is more likely to pitch foward and recover.

To make a surface stall earlier, all you do is increase it's apparent AoA IIRC.

Spins of death => Larger vertically oriented stabiliser, or vectored thrust (Wanderfound's craft almost always have a couple of Vernor's on the nose for this exact reason)

[Hodo]

ech, then i must change something :-(. Need reinstall all :-(. i test stock pod with stock chute and hit sea 420 m/s. I think maybe i left file from RO or change seting. TY for help.

You may need to deploy a drogue chute to slowdown, like the real pod did in real life.

[Behemoth1702]

Thanks for your reply! I will look into Wanderfound's design thread, I haven't looked at it yet!

When I offset a part in the editor, will FAR take this into account? Like - if part of a wing is inside another wing or inside a body, will it still be calculated as if the whole wing was outside? For example if you stick two wings into eachother their whole area is smaller but will they be still calculated as "two complete" wings?

Also - let's say I attach a wing to a body and OFFSET it far to the back, where will the force of this wing be applied? At the attached body point or at the position where I put it?

Thank you!

[Hodo]

I looked at the picture of your design. The CoL is way far back from the CoM. This will make the craft really nose heavy expecially at transonic speeds. And if you clip to wings into each other I think FAR will only read one set of them, it may play crazy havoc with it also. I have never tried to clip two wings into eachother.

As for having parts of a wing clipped into the other you can do that and FAR will still read it correctly, it will read the leading edge of the wing and the total wing surface.

Your vertical stabilizer looks pretty decent for that sized of a craft, but the amount of lift behind your CoM is going to be your biggest problem.

[Wanderfound]

Thanks for your reply! I will look into Wanderfound's design thread, I haven't looked at it yet!

Advance warning: I build to my own tastes, and I like fast, responsive planes. Most of 'em aren't designed to tolerate heavy-handed piloting.

They'll fly just fine if handled appropriately, but if you tell them to kill you, they will happily oblige. Gain some altitude (i.e. 5,000m+) before going supersonic and keep an eye on the G-meter while manoeuvring.

The more recent designs are better than the earliest ones, and anything built before 0.25 will have serious weight balance issues due to the changes in wing mass.

[Zeenobit]

I still cannot get FAR's in-flight UI to show up, after deleting and re-installing the mod several times.

Here's my session log:

https://dl.dropboxusercontent.com/u/636663/KSP_12262014.log

[ferram4]

@Behemoth: They've already covered forward surfaces vs. rearward surfaces, but FAR isn't quite going to get that wing configuration (particularly, the spiky sith-like things) right; it'll be close, but not exact.

Also, yes, spins are deadly. The trick to get out of them is power off, ailerons neutral, rudder full against, elevator through neutral. Simple recovery technique. Problem is, your plane ends up becoming unstable in stall; see that uptick in Cm at very high AoA? That's where it's unstable; you'll have to reduce the sweep of your wing / increase its aspect ratio in order to bring that under control.

@Zeenobit: Known issue with cockpits with built-in intakes.

[Matt516]

The Mk1 pod has a terminal velocity of 160 m/s at 5 km, unless you are somehow confusing FAR by clipping unnecessary heat shields into the bottom of the pod. Just like everyone else who seems to think the pod with a built-in heat shield doesn't have one.

Out of curiosity - why does this happen? The aerodynamics model getting confused when the pod has an extra heat shield, I mean. Does it have something to do with how FAR decides which surfaces to apply drag/lift forces to? Is this something to be fixed in a future release, or is it impossible/not worth the trouble? I ask simply because I'd think that if this can happen with heat shields, it can happen with other (less superfluous) parts as well. But I don't know exactly what causes the problem, so can't really judge that.

[Gobur]

Are you running Advanced Jet Engine by any chance? I had the same issue and removing AJE restored normal drag behavior. Why this worked I have no idea.

Yes. I delete AJE and all back to normal.

Ps. Drouge chute break too when i fly Mach>1

Edited December 27, 2014 by Gobur

[Zeenobit]

@Behemoth: They've already covered forward surfaces vs. rearward surfaces, but FAR isn't quite going to get that wing configuration (particularly, the spiky sith-like things) right; it'll be close, but not exact.

Also, yes, spins are deadly. The trick to get out of them is power off, ailerons neutral, rudder full against, elevator through neutral. Simple recovery technique. Problem is, your plane ends up becoming unstable in stall; see that uptick in Cm at very high AoA? That's where it's unstable; you'll have to reduce the sweep of your wing / increase its aspect ratio in order to bring that under control.

@Zeenobit: Known issue with cockpits with built-in intakes.

Ahh! So that's why. I'm using Ven's Stock Revamp.

Thank you for clearing this up. Can we expect a fix soon? If not, would removing the IntakeAir resource and ModuleResourceIntake module from the cockpit fix the issue?

[Wanderfound]

Yes. I delete AJE and all back to normal.

Ps. Drouge chute break too when i fly Mach>1

Chutes ain't designed for supersonic use.

What sort of reentry trajectory are you using? Is there anything else bolted onto the pod? Setting periapsis to 20km or so should see you safely subsonic long before you hit the ground.

[Gobur]

Chutes ain't designed for supersonic use.

What sort of reentry trajectory are you using? Is there anything else bolted onto the pod? Setting periapsis to 20km or so should see you safely subsonic long before you hit the ground.

I try any trajectory. And any time i hit Kerbin with speed Mach > 1. This is FAR - AJE bug. Now i delete AJE and all is ok. I think AJE messing with BC parametr.

[Behemoth1702]

I looked at the picture of your design. The CoL is way far back from the CoM. This will make the craft really nose heavy expecially at transonic speeds. And if you clip to wings into each other I think FAR will only read one set of them, it may play crazy havoc with it also. I have never tried to clip two wings into eachother.

As for having parts of a wing clipped into the other you can do that and FAR will still read it correctly, it will read the leading edge of the wing and the total wing surface.

Your vertical stabilizer looks pretty decent for that sized of a craft, but the amount of lift behind your CoM is going to be your biggest problem.

Thanks for the feedback. I read somewhere that with FAR the CoL does not have to be very close to the CoM anymore and looking at Wanderfound's amazing planes I see that he is also not tooo concerned with CoL being "right there!". I'll keep trying around.

[Hodo]

Thanks for the feedback. I read somewhere that with FAR the CoL does not have to be very close to the CoM anymore and looking at Wanderfound's amazing planes I see that he is also not tooo concerned with CoL being "right there!". I'll keep trying around.

Here's the thing about that.

The CoL actually shifts rearwards as the craft breaks the transonic speed line.

[blowfish]

It doesn't have to be that close - farther back means more stable but it will pitch down in flight. It should be manageable though.

[Behemoth1702]

Here's the thing about that.

The CoL actually shifts rearwards as the craft breaks the transonic speed line.

Oh really? I did not know that! Thanks for the info.

Man FAR is complicated, ahaha!

[ferram4]

Ho, ho, ho, merry Late-mas! Alright kiddies, here's FAR v0.14.6 with quite a few bug fixes and some changes that should make things smoother going forward. Changelog has info, as always.

[BudgetHedgehog]

Option for aerodynamic failures to result in explosions at the joint during failure.

When you put something like that in, it better be enabled by default

EDIT: Could you clarify "Fixed edge cases involving attach-node blunt body drag being applied when it shouldn't have" please? From what I gather, it's fixing unused attach nodes having drag applied to them, right? What are the edge cases? Just wondering. Imma go look at Git a minute, hang on..

EDIT 2: Ok, I'm stumped :/

Edited December 28, 2014 by ObsessedWithKSP

[ferram4]

The edge cases are the odd things that DaMichel found a few pages back. Mostly involving checking clipping and getting a false positive rather than a false negative.

Also, yes, it is enabled by default.

[BudgetHedgehog]

Ah yes, I see. Thanks for the update, info and for making aerostaging more exciting!

[taniwha]

Darn it, I just updated to 0.14.5.1 last night

[Wanderfound]

Oh really? I did not know that! Thanks for the info.

Man FAR is complicated, ahaha!

The supersonic CoL shift is why you'll get planes that are a bit unstable at subsonic speeds that suddenly become much more stable once supersonic. Run an AoA sweep on your ships at 0.8 Mach vs 1.1; you'll often get stalls at the subsonic speed but not for the supersonic.

The drag at the back of the plane tries to push the nose towards the airstream; the more distance between CoM and CoL, the more leverage available to this force. This is normally a good thing; nose to airstream is what you want to keep your plane stable. However, since planes always require a bit of AoA to maintain level flight, too much of a tendency to point the nose to the wind will make sustained flight impossible: you won't be able to keep the nose up, and the plane will go into an uncontrollable dive.

CoL right on top of CoM is ideal for maximum manoeuvrability, but it isn't essential. Not everything is built as a dogfighter. I tend to like a good amount of stability, but with the option to disrupt it when necessary; a bit of CoM/CoL distance, combined with a lot of pitch authority (thus the prevalence of canards on my designs).

[ThorBeorn]

Thanks for the update!

[Camacha]

merry Late-mas!

Late-mas. Now that is my kind of holiday!

[Behemoth1702]

Jesus, finally finished a plane for kerbin-only, that is 100% stable as far as the charts go.

http://imgur.com/a/toJRw#0

Thanks for all the help and the update too! Merry christmas to you too! I will post soon though about all the different "evil numbers" in the stability chart, hehe. As far as I know there is no easy "if this then that" guide around, like:

"if in level flight, you pitch downwards, your plane is likely to roll left".

I might just create a thing like that to soften the steep learning curve. But oh boy, is FAR amazing!!!

Edited December 28, 2014 by Behemoth1702