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

[GabeTeuton]

Hi Ferram (and others),

Is it possible to figure out whether my craft has enough pitch authority to maintain level flight under certain conditions (speed + atmospheric density, etc...), just from the data provided by the analysis windows?

Sometimes I build a craft which seems aerodynamically sound (all the stability derivatives green, etc...) but then during low speeds (as when landing for example) it cannot keep itself level and it noses down until it crashes. Another situation where this problem sometimes occurs is a spaceplane in very hight altitudes when the plane cannot pitch up enough to keep climbing higher.

So, is there a way to predict these problems while still in the SPH? Or do I have to actually flight it to find out?

As far as I know and learnt, the thing about not being able to pitch up at high altitudes (high speed), MAY be due to the mach tuch effect, add canards to the front of the airplane (check CoL then).-

With the editor analysis you can get the pitch angle to maintain level flight, you have to set the air density, speed and temperature, then calculate, under "Data Stability Derivatives", fourth column, first raw, "Level Flight", AoA= pitch to mantain level flight, i guess if it's toooooo high, doesn't have enough pitch authority (at least not enough for this design, it may be strong when it comes to authority but your design requires too much AoA to maintain level flight), with that AoA you got there you can go to the Static Screen and do the graph, sweeping AoA between 0 and +/- 5º of AoA provided in the first analysis, and see what happens, i believe when the light blue line starts to fall, you are going to start stalling, that's your maximum AoA

If your case is that your AoA obtained from the derivatives analysis is too high, you might want to check how far back your CoL is in relation to your CoM, the further back the larger the AoA you'll need to maintain level flight, also keep in mind that CoL moves backwards with high speeds, so when editing the airplane try to place it closer so you account for that effect, which i believe FAR models!

Hope I helped!

[DaMichel]

Was about to write a full reply but again i was too slow. I'll just add now that you can also examine how much control authority you actually have.

On the right in the static analysis window you can enter a value for the pitch deflection with which the analysis is done, where 0 means no deflection and 1 means max deflection. Enter a 1. Now make an AoA sweep. Look at the cm curve (yellow). It should slope downwards from >0 to <0. See where it crosses the x-axis. This is the AoA that the craft will assume. If it is larger than the AoA needed for level flight, then you are probably good.

Ofc you can fiddle a bit more with the pitch setting to find more or less the pitch input required for the correct AoA. Then in-flight, you can use trim (ALT+WASD) to set the pitch input to this value.

[Matrix Aran]

Is there any reason why a part would show as shielded by a cargo bay in the editor, but would not show as being shielded on the runway? I'm fiddling around with putting Universal Storage quadcores in a cargobay to serve as a bus for cargo containers, and I'm wondering if it could just be an issue with Universal Storage or just something I'm doing wrong.

[madadam]

@GabeTeuton: Thanks for your reply, but most of what you wrote I already knew. I know that I can put speed and air density into the stability derivatives and get the angle of attack necessary to maintain level flight. But what I don't know is whether my craft has enough pitch authority under those condition to actually achieve this angle of attack. So i'd like to know if this information is somehow available in the stability derivatives or somewhere else.

@DaMitchel: Thanks, that sounds promising. I'll give it a try later on today. One thing though: I don't think you can put the air density into the static analysis window so not sure how I can use it to figure out the pitch authority in high altitudes. I'll check it out anyway. Thanks!

[GabeTeuton]

@GabeTeuton: Thanks for your reply, but most of what you wrote I already knew. I know that I can put speed and air density into the stability derivatives and get the angle of attack necessary to maintain level flight. But what I don't know is whether my craft has enough pitch authority under those condition to actually achieve this angle of attack. So i'd like to know if this information is somehow available in the stability derivatives or somewhere else.

Fine, then i guess what i can tell you from what i just learned from you guys is that the elevetors need to bee as far away from the center of mass as possible (Edit: in the long axis of course) in order to get better authority, i believe this is related to "leverage", adding more elevetors also helps as far as i know as control surfaces also lift so the more lift you have that you can control the more authority you'll have i guess...

Edited October 17, 2014 by GabeTeuton

[DaMichel]

@DaMitchel: Thanks, that sounds promising. I'll give it a try later on today. One thing though: I don't think you can put the air density into the static analysis window so not sure how I can use it to figure out the pitch authority in high altitudes. I'll check it out anyway. Thanks!

Hm, right, odd. Take this with a grain of salt, because this is not my area of expertise. AFAIK the total torque on the craft is M = cm * Q * terms-depending-on-the-shape-of-the-craft. So for cm=0, there is no torque on the craft, regardless of air speed or density. The restoring force, when the craft deviates from this stationary point, depends on airspeed obviously.

[endl]

hey ferram its me again i talked with the b9 boys and they say i should talk with you. my stuff in m2 cargo is blowing up says its not shielded on runway.

[blowfish]

hey ferram its me again i talked with the b9 boys and they say i should talk with you. my stuff in m2 cargo is blowing up says its not shielded on runway.

Just get the latest version - the issue is fixed.

[camlost]

Reporting a bug:

The Cd of Mk1-2 heatshield from DRE seems too small. Other heatshields seem normal

[jrhii]

I've been away from the game for a month or two while my video card was being replaced. Is there some sort of change that has occurred that requires more Delta V to get a rocket to space or am I just having trouble? I was getting there with 3300 to 3500 m/s, now it is in the 4000 m/s+ range. I find myself having to provide a larger and hazier safety margin when I used to be able to build everything at a delta v budget of adding 10% to my estimate and being good to go.

[NathanKell]

I just made a 2-stage launcher with quite low TWRs that takes ~3350 to get to orbit (that's "give it 3400 vac dV, have 50 left at 75x75km", not "how much dV did Mechjeb say I expended" which would be less). I have no doubt that a low-drag, high-TWR launcher could manage closer to 3000.

[Wanderfound]

How are folks doing with the wing strength tweakables? I'm finding 0.4 good for workhorse stuff, and 0.2 acceptable for more fragile speedsters.

Anyone successfully made an ultralight work? Any opinions on what's the maximum beyond which extra strength is pointless?

[DaMichel]

I think strength 1 is very sturdy ...

This was in a kinda sustained turn, flying with trim controls. On a side note, the launch escape tower works nicely as nosecone, too.

I made glider with minimal wing mass but it is still pretty heavy.

[Matrix Aran]

Seeing as I've been playing on a non revertible hard mode (with Kerbal Construction Time Simulations because I'm not completely insane), I've stuck with 0.7 on my 45 ton design and 0.5 on my lighter designs in the interests of having some safety margins. Over time, as I grow more confident in the designs and how they fly I'll slowly shave some weight here and there to get better performance from them. I know that the 45 ton design has had some moments where it was sustaining 10g turns without issue so it could probably stand to lose some weight, however I know from previous testing that 0.5 really wasn't enough for Kerbal safety.

[JackCY]

Hi Ferram (and others),

Is it possible to figure out whether my craft has enough pitch authority to maintain level flight under certain conditions (speed + atmospheric density, etc...), just from the data provided by the analysis windows?

Sometimes I build a craft which seems aerodynamically sound (all the stability derivatives green, etc...) but then during low speeds (as when landing for example) it cannot keep itself level and it noses down until it crashes. Another situation where this problem sometimes occurs is a spaceplane in very hight altitudes when the plane cannot pitch up enough to keep climbing higher.

So, is there a way to predict these problems while still in the SPH? Or do I have to actually flight it to find out?

Look at the yellow line in AoA graph, if it's going down way too much it might not even take off and will pitch down a lot. If it's about level but under zero, then it's fine, if it's above zero then it's going to pitch up by itself a little. If it's going up above zero too much, Kerbals are going to die. Change the speed, pitch, etc. to see how it behaves at different speeds and other settings.

I find this really easy to correct and remember for future builds.

Is there any reason why a part would show as shielded by a cargo bay in the editor, but would not show as being shielded on the runway? I'm fiddling around with putting Universal Storage quadcores in a cargobay to serve as a bus for cargo containers, and I'm wondering if it could just be an issue with Universal Storage or just something I'm doing wrong.

On runway it shows as partsShielded: 1 when cargo is closed and 0 when open, there are 5 quadcores each with 4 modules. I suppose 1 = true, 0 = false. Dropping parts didn't change it, still 1 or 0.

In editor it shows partsShielded: 25. The number of parts. Parts shows as isShielded: True.

Attached to the front of cargo, mounted by the joints, no surface mounting.

How are folks doing with the wing strength tweakables? I'm finding 0.4 good for workhorse stuff, and 0.2 acceptable for more fragile speedsters.

Anyone successfully made an ultralight work? Any opinions on what's the maximum beyond which extra strength is pointless?

Seeing as I've been playing on a non revertible hard mode (with Kerbal Construction Time Simulations because I'm not completely insane), I've stuck with 0.7 on my 45 ton design and 0.5 on my lighter designs in the interests of having some safety margins. Over time, as I grow more confident in the designs and how they fly I'll slowly shave some weight here and there to get better performance from them. I know that the 45 ton design has had some moments where it was sustaining 10g turns without issue so it could probably stand to lose some weight, however I know from previous testing that 0.5 really wasn't enough for Kerbal safety.

I found even 0.5 to not have enough strength for my hard flying. I guess 0.7 should be fine but I'm not interested in changing stats of every darn wing I add on a plane, too time consuming. If it could be predefined, cool.

I've made a tiny glider with 0.1s but it's no fun to fly really. Unless mods and folding it in a cargo bay and dropping it out up high to glide. Used an ion engine on it but it doesn't get far and 0.1 can rip it apart on hard maneuvers.

And even a 1 strength I just torn apart doing a turn at slow speed, too many Gs I bet I tend to max out the G meter. Kerbals seem resistant to G forces.

OKAY, scratch the last part, I've just killed both of my crew members due to G force damage while the plane survived my low attitude turn

Edited October 18, 2014 by JackCY

[Jovus]

I'm findinng that 0.4 is about the sweet spot for my general purpose planes, with the bare possibility of 0.15 for craft I really want to baby to go fast, and up to about 0.7 for "I don't want to have to care about aerodynamic disassembly." 1 is what I use for slamming things into full pitches at Mach 3 to make myself giggle.

That being the case, I would love it if in the next release the wing strength tweakable could be rescaled from 1 to 0.1 - either so that finer gradations are possible, or just so it's easier to pick a specific value. (Right now it looks like about half the bar is wasted.)

[Naten]

My toolbar icon for FAR is dead... it's just black. I'm running Active Texture Management. What is happening? It looks so ugly... ;_;

It's just a black square. Uninstalling and re-installing FAR or Active Texture Management is not working.

[Naten]

It worked with my new Active Texture Management config fixes, so nvm. It was an issue with the fixes that "disabled" the FAR folder. I thought it was just disabling compression, but it looked like it disabled the FAR folder's textures altogether!

Cheers.

-Naten

[Matrix Aran]

On runway it shows as partsShielded: 1 when cargo is closed and 0 when open, there are 5 quadcores each with 4 modules. I suppose 1 = true, 0 = false. Dropping parts didn't change it, still 1 or 0.

In editor it shows partsShielded: 25. The number of parts. Parts shows as isShielded: True.

Attached to the front of cargo, mounted by the joints, no surface mounting.

This is more or less what I was seeing aswell. I went back and replaced the US bus with a simple contraption made out of a docking port, fuel tank and some RCS jets. On the runway it shows as parts shielded 17, so it's definitely something wonkey with Universal Storage. Just not sure who I should report it to. As Universal Storage also uses KAS, it gets just a bit complicated. Is it US, KAS, or FAR at fault?

Edited October 18, 2014 by Matrix Aran

[GigaG]

Why does it disable itself on Win64? Does it not work at all? Because if it does, I kind of want to use it. I understand the instability issue. I do not understand why you can't make people aware of it and make an "unsupported" build.

[GabeTeuton]

Why does it disable itself on Win64? Does it not work at all? Because if it does, I kind of want to use it. I understand the instability issue. I do not understand why you can't make people aware of it and make an "unsupported" build.

I didn't like that at first but in the end the one responsible for this thread is ferram, and some people just won't understand that it's UNSUPPORTED and keep asking once, twice... won't read previous post... Besides this feature forced me to use x86 version and it works so well... with a bunch of mods (around 1gb if i remember correctly)... it works so smooth... i was used to play the x64 version of 24.2, lots of crashes haha...

[BudgetHedgehog]

Why does it disable itself on Win64? Does it not work at all? Because if it does, I kind of want to use it. I understand the instability issue. I do not understand why you can't make people aware of it and make an "unsupported" build.

It's cute you think people read. If you understand the instability issue, then you understand why ferram will have no part in enabling it in x64. Bear in mind as well that 0.25 64bit is more unstable than 0.24.2 64bit - even the devs admit that. Anyway, this is why:

@smunisto: I tried that. It didn't work. Did you notice that I was one of the few modders that didn't have "will not support win64" in the OP during 0.24?

But I'm tired.

I'm tired of being sent off chasing bugs that aren't my own.

I'm tired of running damage control when someone says that "doing X fixes it on win64" when it doesn't.

I'm tired of trying to maintain higher stability standards for win64 KSP than Squad has.

I'm tired of giving people incentive to use a messed up and unstable build.

But most importantly, I'm tired of people not reading the warnings and following them. Since Compatibility Checker has existed, we've had more and more instances of people just ignoring it, advocating other people ignoring it, and then when something actually breaks, people complain to us. Win64 KSP is no different.

So after spending all this time trying so desperately hard to leave open the option to people who understand that they're being reckless, all we've gotten back is complaints, anger, and a flood of garbage that buries valid reports. Worse, CC has only drawn attention to those mods and brought more complaints and trash reports because a mod had the gall to draw attention to the fact that it wasn't properly functional. So now, after giving me hell in return for giving you a way around the warnings, you don't get to go around them anymore.

"But it's not my fault! I never complained to you about win64 issues! I'm innocent!" Of course. You're innocent of being a jerk directly. You're guilty of trying to enable other people by trying to get me back into that position. You're guilty of being the reason Squad decided it was better to release a broken win64 KSP rather than pull it like I asked. You're guilty of being the reason that they decided to rush a build out after someone hacked a broken win64 version together.

You can either switch to the win32 build or the linux 64-bit build. I'm not wasting my time on win64 anymore.

[Wanderfound]

The FAR flight assistance window has developed an unfortunate habit of launching itself every time I come within physics range of another vessel. Anyone else getting this?

[DaMichel]

Yes. I just noticed this too after updating to the current dev code.

[reteyez]

For some reason the mod doesn't work for me. The wings dont generate any lift, only winglets do. I have the same issue with NEAR. I tried it on a fresh install of KSP 0.25 with FAR 0.14.3 only.