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

[123nick]

anyone know what the name of the mod that adds in the control surface tuning dependent on speed, height, etc? i forgot what its called.

[kcs123]

36 minutes ago, 123nick said:

anyone know what the name of the mod that adds in the control surface tuning dependent on speed, height, etc? i forgot what its called.

I'm not sure, but it might be Pilot Assistant Atmospheric piloting aids or Dynamic deflection mods that you are seeking for.
You should also want to install StockBugFixes from Claw, that alows to fine tune control authority on control surfaces too, as well as gimbals on engines.

[ferram4]

Alright, so current state of things: it should be about ready for release, but I want a day or two to go over it to see if any other nasty drag things show up.  Transonic drag got a bit of a change pass to play nicer with low-fineness ratio vehicles (read: reentry vehicles and command pods) while leaving other vehicles relatively alone.  Also some changes that should reduce subsonic drag slightly for higher fineness ratio vehicles and increase it for lower fineness ratio vehicles.  I'd release now, but I'd rather not risk creating a negative drag or stupidly low drag situation where there shouldn't be one.

[the_machemer]

Not sure if anyone mentioned this in here already but does using KerbalJointReinforcement prevent your aircraft from breaking up as easily under high aerodynamic forces? And if so, are there settings i can adjust to negate this?

[kcs123]

30 minutes ago, the_machemer said:

Not sure if anyone mentioned this in here already but does using KerbalJointReinforcement prevent your aircraft from breaking up as easily under high aerodynamic forces? And if so, are there settings i can adjust to negate this?

Both, KJR and FAR were released by Ferram. KJR should prevent turning rocket into spaghett due to too low forces between joints. I have both installed and aerodynamic failures are more than possible if you are not careful with piloting and craft designs.

Point is - with KJR gameplay is not unbalanced, if that is thing that you worry about.

[tetryds]

3 hours ago, the_machemer said:

Not sure if anyone mentioned this in here already but does using KerbalJointReinforcement prevent your aircraft from breaking up as easily under high aerodynamic forces? And if so, are there settings i can adjust to negate this?

It does not directly affect the resistance of the wings, nor does adding more struts.

What ends up happening is that the wings break up more easily if you use KJR, wing flexing of stock joints reduces the load on them making them harder to break.

[gary85]

is this mod still better than new stock aerodynamics?

and is it hard on pc cause i only have 8gig ram and core duo prcessor?

[NathanKell]

Yes.

No.

[Volt]

Hey, not been playing KSP for a while as I quite smartly went and 'upgraded' to a 2.4GHz Core 2 Quad which can barely run KSP, so been waiting for 1.1. Also been busy with college, and I'm rather confused about something I've learnt in Aerodynamics.

So according to my tutor, a tail plane functions by providing 'negative' lift, countering the pitch-down effect of the lift/weight moment. However, obviously, in KSP the wings appear to always provide lift in the upwards direction. When you add a tail plane, the centre of pressure moves aft, as if the tail plane is 'adding' lift. How does this work? Also, I apologise in advance as I'm sure you've probably answered this question to death, but finding information about complex topics in a 466 page swath of aerodynamics facts is not easy.

Edited January 6, 2016 by Volt

[ferram4]

Well, for starters, a tail plane doesn't necessarily provide negative lift.  Consider a stable plane where the lift of the main wing is centered ahead of the CoM; to balance the plane out and prevent it from pitching downwards, the tail must provide positive lift to counter that.  It's just that in many designs, the horizontal tail does provide negative lift, though in those cases it's generally unnecessary for static stability and only provides extra pitch damping and pitch control.

Okay, second, FAR doesn't display the CoP.  Turns out, that leads to very un-useful results if there's any pitching tendency when lift sums up to 0; the math says that the CoP must be infinitely far from the CoM... which makes it rather useless.  Instead, we have the Aerodynamic Center, which handles this by allowing a constant pitch-moment of some kind into the analysis that helps stabilize that dramatically.

And finally, why does the aerodynamic center move back if the tailplane is producing negative lift in a steady configuration?  Because the actual magnitude of the lift is irrelevant for placing the aerodynamic center.  Only the lift slope is important, that is, how much lift you get from each part as angle of attack changes, and that is (almost) always positive.  It doesn't matter how much negative lift the tail creates, if the plane pitches up a smidge the tail will make more positive / less negative lift; if the tail is far enough from the CoM to push the plane's nose back down, the plane will be stable.  Perhaps not controllable, but certainly stable.

[steve_v]

30 minutes ago, Volt said:

obviously, in KSP the wings appear to always provide lift in the upwards direction.

Dunno about stock, but in FAR a wing with a negative AoA will quite happily produce "downwards lift", as evidenced by the ability to fly upside-down.

30 minutes ago, Volt said:

When you add a tail plane, the centre of pressure moves aft, as if the tail plane is 'adding' lift. How does this work?

The CoP is not the CoL as it would be in stock. Note that there is no arrow attached to the blue ball, indicating that the force the horizontal stabiliser (or any part for that matter) is adding is not necessarily "up" or "lift". Ignore that confusing little blue ball and look to the analysis graphs, they tell a truer tale.

 

Ed. OTOH, ignore my attempt to simplify and just listen to ferram, who actually knows what he's on about.

Edited January 7, 2016 by steve_v

[Volt]

Ahh, that makes sense. Not sure why it took until I got to transonic aeros before I started to wonder this! I need to get back into KSP... thanks, both.

[NathanKell]

Also, KSP wings haven't done that since .90.

[balu0]

Hi,

Quick question about mach number and IAS

Never mind I figured it out , my understanding of TAS was wrong

Basicly I was wondering if mach number is IAS or TAS , but it is TAS and it is good that way .

Edited January 10, 2016 by balu0

[Iago]

Does this mod include turbulence and ground effect?

[kcs123]

13 minutes ago, Iago said:

Does this mod include turbulence and ground effect?

No.

Ground effect could come when wing overhaull is made. Ferram mentioned this couple of posts back(or pages). I'm not sure about turbulence.
 

[Iago]

I am trying to make a mod that adds weather patterns, and was looking for a way to simulate wind.

[kcs123]

1 minute ago, Iago said:

I am trying to make a mod that adds weather patterns, and was looking for a way to simulate wind.

There is another mod that deals with wind: Kerbal Wind.
Although, I think that they have included only fixed wind velocity/direction. It wold be nice if someone simulate more realistic weather with air pressure drops area and such,
There is also askings about thermal pillars for glider fans. I think FAR can deal with those just fine, just need to dynamically alter atmosphere curve instead fixed one.
(Curve that describe atmosphere at different altitudes (pressure,temperature))

[Iago]

Also, with weather patterns: I want to make sandstorms that cover solar panels, rain which weighs your aircraft down and lightning that overheats your craft. And hurricanes/tornadoes.

[Drew Kerman]

5 hours ago, Iago said:

Also, with weather patterns: I want to make sandstorms that cover solar panels, rain which weighs your aircraft down and lightning that overheats your craft. And hurricanes/tornadoes.

Calling in @silverfox8124... https://kerbalstuff.com/mod/262/Kerbal%20Weather%20Systems!

[Nansuchao]

@ferram4 A little suggestion, if anyone is interested: it will be possible to see in the Far window or in the Flight data the stall speed? I assume that Far calculate the stall speed of every plane, so have it shown can help during landing, take off and other maneuvers.

[ferram4]

So, actually that's a lot more difficult than it sounds.  FAR doesn't bother to calculate stall speed at all, because wings don't stall at a specific speed, just at a specific angle.  Now, of course that makes calculating stall speed theoretically simple by calculating the maximum lift coefficient of the wing and then solving back for the speed at SL that would allow the plane to achieve 1g's worth of lift.

Except, it's not that simple.

Alright, so ignoring the problem of calculating the maximum lift coefficient achievable on a given vehicle with wings of all shapes and sizes attached at weird angles that makes even calculating that simple, there's another problem: what if the plane can't stall itself with pitch inputs?  Okay, so this is technically not solving for stall speed, instead it would be for the minimum speed for level flight, but it would probably be considered the stall speed by everyone who isn't a pedant aero engineer.  So now this has moved from a relatively simple comparison of lift vs. gravity to a more complicated comparison of lift vs. gravity + maximum angle achievable by full pitch-up inputs.

All of this is very doable.  However, it'll probably take a long time until I implement something like that because of all the weird things I might need to handle.

[tetryds]

That gave me an idea, what about plotting cruise speed/aoa or aoa/speed (depending on the plot) on the graphs?

It would help a lot on dimensioning the wings.

[Nansuchao]

4 hours ago, ferram4 said:

So, actually that's a lot more difficult than it sounds.  FAR doesn't bother to calculate stall speed at all, because wings don't stall at a specific speed, just at a specific angle.  Now, of course that makes calculating stall speed theoretically simple by calculating the maximum lift coefficient of the wing and then solving back for the speed at SL that would allow the plane to achieve 1g's worth of lift.

Except, it's not that simple.

Alright, so ignoring the problem of calculating the maximum lift coefficient achievable on a given vehicle with wings of all shapes and sizes attached at weird angles that makes even calculating that simple, there's another problem: what if the plane can't stall itself with pitch inputs?  Okay, so this is technically not solving for stall speed, instead it would be for the minimum speed for level flight, but it would probably be considered the stall speed by everyone who isn't a pedant aero engineer.  So now this has moved from a relatively simple comparison of lift vs. gravity to a more complicated comparison of lift vs. gravity + maximum angle achievable by full pitch-up inputs.

All of this is very doable.  However, it'll probably take a long time until I implement something like that because of all the weird things I might need to handle.

Thanks a lot for the answer. I didn't thought it was so complicated.

[Rodhern]

Positive Xu:

Hello.

I finally got around to install FAR. How cool is it to (almost) have your own KSP wind tunnel available at the SPH to play... I mean to conduct serious aerospace research for Kerbalkind? Ok, that isn't one of my actual questions. I hope one of you forum regulars can enlighten me some on this simple scenario:

• I go to the VAB (or SPH).
• I select a "Mk1 Command Pod" and leave it at its default position.
• I open the FAR window and select the Stability Derivatives tab.
• I click calculate (sea level Mach 0.35: i.e. 119 m/s).
• Xu shows up as 0.068735 (in red because it is positive).

 

1. Does this happen to you as well?
2. Is there a connection to level flight AoA showing ">0 deg"?
3. How should I interpret the value in this case?

 

By the way, what is the 'initial' state for the derivative calculation? Is the AoA set for level flight (i.e. calculated ahead of time and the craft rotated about the y-axis), and what is the state of the pitch control surfaces  (e.g. trimmed for zero pitch rotation, or set at neutral)? And what is the 'delta' for the Xu calculation, is it a simple (and small) change in 'u' with the AoA kept 'frozen'?

Edited January 20, 2016 by Rodhern
cosmetic