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

[camlost]

@Gabe, aside from what NathanKell said, you need much lower aspect ratio (AR). Generally delta-wing designs, like Mirage, have sweep angle > 60 degrees. Or you'll not have enough pitching control and will be too draggy in supersonic

[GabeTeuton]

Okay I used your advices, and honestly i'm still having a large scale stall when i'm around 24k above kerbin @ 1400m/s +/-... Am I applying the advices in a wrong way?

-added the canards in the front, and also in the back and set them to pitch only

-the wing ctrl sfcs are roll only

-i believe the current angle of sweep is okay, is it??

-will that much vertical tail work?

-the only "problem" i'm still having and can't think of a way to resolve is the placement of the wings and how to move the CoM forward, I'm having trouble placing the wings as the LFO tanks are rather short so i can't play much with the placement, and where the main fuselage has empty space (like to place wings), it's either way in front or way back... I also tried to move those tanks forward/backwards but the CoM still moves too inline with them, forcing me to use them as the spot to place the wings... (tried to use LF tanks instead of those, and place the LFO tank in the main fuselage but the case is more or less the same, I did manage to move the CoM a little by placing the current main fuselage LF tank in front of the crew module)...

EDIT= {I just thought about the X-29, will forward sweep work in KSP with FAR?, 'cause i believe i could work around this issue with forward sweep,

Also i could just place the wings at the bottom of the fuselage or the top, and place all the engines on top, below them, to be able to center all the mass of the aircraft near the middle... But i'm not sure about the properties of such a design for supersonic flight}

The idea of this SSTO is to return 11 kerbals (in 3 trips, as using 3 crew modules is impossible, provided i can't even make it work even without one) that are in a space station that i'm going to deorbit, as a second iteration of it is going up, but i don't want to do it with a rocket (the return trip) because i should be able to do it with a f***ing spaceplane haha`(I've done it in previous versions, with FAR)... nor want to transfer them from one space station to another in orbit...

(by the way is it okay to keep posting in this thread or should i make a new one?)

Edited October 16, 2014 by GabeTeuton

[endl]

so i tried downloading the latest version, and redesigning my plane this current version stalls really hard when i try to nose up to vertical, i dont know if this is intended behavior but any advice would be welcome

[Voculus]

The 14.3 release is awesome! There's still some SAS oscillation, but the PID Tuner fixes that. Otherwise, the flight model is smooth as silk. Excellent work, and many many thanks, Ferram!

[Jovus]

So, to ask the stupid/obvious question: when you get this stall around 24k, have you already cut out the turbojets? 'cause if they're running out of air, they're flaming out, and they're almost certainly doing it asymmetrically - which will put you in a flat spin or other stall situation.

[GabeTeuton]

So, to ask the stupid/obvious question: when you get this stall around 24k, have you already cut out the turbojets? 'cause if they're running out of air, they're flaming out, and they're almost certainly doing it asymmetrically - which will put you in a flat spin or other stall situation.

According to the resource tab, total thrust in KE and % of air consumption over intake, and right clicking them, they are all working properly by then, and let me go further ahead, when i tested the turbojet/rapier combination, i kicked the rapier rockets and got past the 25k, the turbojets where still working, i believe around 30k, +/- 2k you need to cut them out...

[Starman4308]

According to the resource tab, total thrust in KE and % of air consumption over intake, and right clicking them, they are all working properly by then, and let me go further ahead, when i tested the turbojet/rapier combination, i kicked the rapier rockets and got past the 25k, the turbojets where still working, i believe around 30k, +/- 2k you need to cut them out...

That depends on velocity and number of intakes: there is no one constant altitude to cut your jets. If you use Mechjeb, in the Utilities section there's an option to have MJ throttle your jet engines to avoid flameout for you, and you can edit a window to show you intake air, amount of intake air needed, and amount of intake air with all intakes open (MJ also has something to open/close intakes for you to minimize drag).

[GabeTeuton]

That depends on velocity and number of intakes: there is no one constant altitude to cut your jets. If you use Mechjeb, in the Utilities section there's an option to have MJ throttle your jet engines to avoid flameout for you, and you can edit a window to show you intake air, amount of intake air needed, and amount of intake air with all intakes open (MJ also has something to open/close intakes for you to minimize drag).

I open and close them with Action Groups with the info that provides Kerbal Engineer (KE), which tells me the amount of air intake needed by the engines, and gathered by the intakes, and recalculates that amount in real time, so there is no need for mechjeb, i used that mod a long time ago, and it was awesome, but got bored really quickly, there's no point rather than building the rocket if mechjeb is gonna do the job hehe

[endl]

so i tried downloading the latest version, and redesigning my plane this current version stalls really hard when i try to nose up to vertical, i dont know if this is intended behavior but any advice would be welcome

http://i.imgur.com/D7A7yEN.jpg

can anyone tell me why im stalling?

[ferram4]

You are stalling because you went above the critical angle of attack. That happens. It's supposed to happen.

[endl]

thanks for the help ferram i thought it might be intentional. how do you build to create more stability for a vertical climb?

[Wanderfound]

can anyone tell me why im stalling?

As Ferram said.

If you want to climb vertically, you need to gradually pull the nose up, letting the prograde marker keep up with you as you go. Ideally, you want to keep your angle of attack a hair's breadth short of inducing a stall until you reach the direction you're after.

Lead the plane, don't force it. Planes like to fly in curves, not angles.

If you want to maintain the vertical climb, you also need a TWR above 1. It definitely can be done, though:

Edited October 16, 2014 by Wanderfound

[ferram4]

Make sure the frontward surfaces stall first. That means less sweep and higher AR than the main wing. Alternatively, look to make sure as much drag is near the bag of the plane as possible.

[endl]

ah so its my flying, im used to being able to do a sharp climb in stock so i guess i was doing it wrong.

[jrandom]

ah so its my flying, im used to being able to do a sharp climb in stock so i guess i was doing it wrong.

Real aerodynamics take a little getting used to, but after flying FAR for while you'll never want stock atmo again. (I never realized just how bad it was until there was an update of KSP and FAR hadn't caught up yet and I thought "I'll just fly around in stock for awhile!" and that lasted a whole 47 seconds before exiting KSP and waiting for FAR to update.)

Edited October 16, 2014 by jrandom

[lincourtl]

I'm not sure what I'm doing wrong with my rockets. Since 0.25 all my rockets tumble over to 180 degrees in FAR, no matter how simple they are. It's like there's some sort of unseen drag on that side of the rocket. I'm 99.9% positive that it isn't FAR -- that I'm just having a brain fart -- since planes are flying beautifully with FAR 14.3.

You can see what I mean in this two stager. It has a high center of mass, low center of lift, and low initial TWR. Almost right out of the gate it starts tumbling over toward the 180 degree mark. I also included as an example another simple rocket which I think should be fine. I can get both of these into orbit, but I have to fight them the whole way.

I've been doing all of my testing in a fresh install of 0.25 with only FAR 14.3, Deadly Reentry 6.2.1, Active Texture Management, Kerbal Engineer 1.0, and Blizzy's toolbar installed.

Javascript is disabled. View full album

On edit: Image gallery isn't loading for me. Seems to work fine with direct link: http://imgur.com/a/4JdyT#0

Edited October 16, 2014 by lincourtl

[ferram4]

I would suggest a complete re-install of FAR to check if that's the issue, but I suspect it's something else. Check what happens with the launch clamps set up differently, maybe it's the initial launch kick causing that.

[lincourtl]

I would suggest a complete re-install of FAR to check if that's the issue, but I suspect it's something else. Check what happens with the launch clamps set up differently, maybe it's the initial launch kick causing that.

Thanks ferram. My previous pics were from a completely fresh copy of KSP downloaded off Steam, with a freshly downloaded copy of FAR and DR. I sincerely doubt it's FAR too -- or DR for that matter. I'll try it without the launch clamps.

[jrandom]

I've just now starting testing out .14.3, and it's extremely stable and well-behaved. My planes are flying exactly as I would expect them to!

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[AetherGoddess]

I'm not sure what I'm doing wrong with my rockets. Since 0.25 all my rockets tumble over to 180 degrees in FAR, no matter how simple they are. It's like there's some sort of unseen drag on that side of the rocket. I'm 99.9% positive that it isn't FAR -- that I'm just having a brain fart -- since planes are flying beautifully with FAR 14.3.

You can see what I mean in this two stager. It has a high center of mass, low center of life, and low initial TWR. Almost right out of the gate it starts tumbling over toward the 180 degree mark. I also included as an example another simple rocket which I think should be fine. I can get both of these into orbit, but I have to fight them the whole way.

I've been doing all of my testing in a fresh install of 0.25 with only FAR 14.3, Deadly Reentry 6.2.1, Active Texture Management, Kerbal Engineer 1.0, and Blizzy's toolbar installed.

http://imgur.com/a/4JdyT#0

On edit: Image gallery isn't loading for me. Seems to work fine with direct link: http://imgur.com/a/4JdyT#0

i have the exact same problem if i don't launch with SAS on, or give it a slight nudge to the right just after launch. i think there is something weird in how the physics system is settling stuff on the pad.

[SkyRender]

Maybe I'm just missing something, but is FAR getting more prone to introducing phantom fluctuations lately? It might just be the SP+ parts doing it, actually, because this problem was nowhere near as pronounced in 0.24.2 with the old parts. I just can't help but notice that my planes are more prone than ever to entirely unexplained rotation despite being absolutely symmetrical and exceptionally aerodynamic. To the point that craft now wobble unsteadily with SAS on, and require constant roll maintenance with it off. Is there some sneaky setting I have to trigger to get FAR to behave well with SP+ elevon parts, or perhaps some adjustment I'm expected to make to account for the new flap designs? Someone help me out here.

[Wanderfound]

Maybe I'm just missing something, but is FAR getting more prone to introducing phantom fluctuations lately? It might just be the SP+ parts doing it, actually, because this problem was nowhere near as pronounced in 0.24.2 with the old parts. I just can't help but notice that my planes are more prone than ever to entirely unexplained rotation despite being absolutely symmetrical and exceptionally aerodynamic. To the point that craft now wobble unsteadily with SAS on, and require constant roll maintenance with it off. Is there some sneaky setting I have to trigger to get FAR to behave well with SP+ elevon parts, or perhaps some adjustment I'm expected to make to account for the new flap designs? Someone help me out here.

Look upthread for regex's PID Controller mod: http://forum.kerbalspaceprogram.com/threads/20451-0-25-Ferram-Aerospace-Research-v0-14-3-10-15-14?p=1473120&viewfull=1#post1473120

Cutting both pitch kp and clamp to 1/3 of default got rid of all of my SAS-induced wobbles. You may want to try something similar on the roll axis.

Also: are you using the latest FAR release? There have been some aero bugs to sort out since 25 dropped; it appears to be fixed now.

[ferram4]

SAS has always had problems with FAR and NEAR, because SAS has always had problems with high control authority vehicles. This is why the stock thrust vectoring ranges are tiny, and the stock control surfaces only get away with it because their lift varies with velocity rather than velocity^2.

Unexplained rotation is an old problem, caused by uneven flexing of joints, which is a stock issue. It is exacerbated by the fact that lifting forces are higher with FAR and NEAR than in stock, so it's a lot more pronounced.

In both cases, complain to Squad. The latter is a bug that's been around forever, and the former was re-introduced after they tweaked SAS following its overhaul.

[ghimb2000]

SAS has always had problems with FAR and NEAR, because SAS has always had problems with high control authority vehicles. This is why the stock thrust vectoring ranges are tiny, and the stock control surfaces only get away with it because their lift varies with velocity rather than velocity^2.

Unexplained rotation is an old problem, caused by uneven flexing of joints, which is a stock issue. It is exacerbated by the fact that lifting forces are higher with FAR and NEAR than in stock, so it's a lot more pronounced.

In both cases, complain to Squad. The latter is a bug that's been around forever, and the former was re-introduced after they tweaked SAS following its overhaul.

Is there a way for FAR/NEAR to ignore uneven flexing of joints?

[Wanderfound]

Is there a way for FAR/NEAR to ignore uneven flexing of joints?

Doubt it.

Moar struts. Or, with the new version, increase your wing mass/strength tweakable values.