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

[iueras]

I apologize if this has been answered but I couldn't find it in a search and this thread is long...

Is there a way to use the control surface axis assignments in FAR to make a plane roll when I use the x-axis of my joystick instead of the twist, instead of having to exit and reassign them when I switch between rockets and planes? I tried using the assignments but the ailerons did not respond to the x-axis input at all.

Edited August 16, 2013 by iueras

[jrandom]

I apologize if this has been answered but I couldn't find it in a search and this thread is long...

Is there a way to use the control surface axis assignments in FAR to make a plane roll when I use the x-axis of my joystick instead of the twist, instead of having to exit and reassign them when I switch between rockets and planes? I tried using the assignments but the ailerons did not respond to the x-axis input at all.

I suppose you could reverse the FAR "Yaw" and "Roll" settings on your control surfaces, maybe? If you have your joystick left/right set to 'yaw' (which is good for rockets), you'd want to assign 'yaw' to your roll surfaces on your plane.

[Autochton]

What is Flap Key? I know Air-Brake is 'B', but how do you deploy flap?

Also,

How do I change Flap and Air-Brake keys?

Is there any other keys I should know about?

Air brakes are automatically assigned to the 'Brake' action group, IIRC, not sure if you can change them, since I haven't used them much (I prefer the B9 pack's brakes, but they don't count as control surfaces, they just increase drag). Flaps need to be assigned to a numbered action group (I often use 9 and 0, myself) for increase and decrease deflection.

[AndreyATGB]

Anyone else's CoL display completely wrong? It will show lift as backwards somehow instead of up, often it also moves to the side even though the planes are perfectly symmetrical. It will be correct if I reload the .craft but the FAR CAS option to recalculate CoL doesn't do much. This makes building planes extremely difficult.

[loknar]

If you are new to FAR like me, it is quite a shock and you have to change your design and piloting behaviour, notably the angle of attack must be low.

[Van Disaster]

Anyone else's CoL display completely wrong? It will show lift as backwards somehow instead of up, often it also moves to the side even though the planes are perfectly symmetrical. It will be correct if I reload the .craft but the FAR CAS option to recalculate CoL doesn't do much. This makes building planes extremely difficult.

The last few pages of the thread have examples of this - I've no idea why it's come back, it was an old issue that got fixed at some point.

Inward-tilting rudders - I've actually tried to use those because to me it would appear that tilting one inwards cancels some of it's roll moment by attempting to lift or push down it's side of the plane a little ( and the opposite rudder doing the opposite, obviously ). I take it that's not really a correct assumption?

[Torminator]

The last few pages of the thread have examples of this - I've no idea why it's come back, it was an old issue that got fixed at some point.

Inward-tilting rudders - I've actually tried to use those because to me it would appear that tilting one inwards cancels some of it's roll moment by attempting to lift or push down it's side of the plane a little ( and the opposite rudder doing the opposite, obviously ). I take it that's not really a correct assumption?

I can't claim any expertise with aerodynamics, but my assumption was that when the plane is rolling, the rudders are pointed into the roll; in other words, the side of the rudder that's resisting the roll is the thinnest side, at the top. Outward pointing rudders are exposing their broad sides to the roll.

[Julicos]

without FAR i cant fly because i amgood n fs2004 and te kerball aerodinamics are strange.Is compatible with the last update??

[birrhan]

Do you have a screenshot of your rocket? Where is it's center of mass? How fast are you attempting your gravity turn, and at what speed/altitude?

Elsewhere yeah. I can guarantee COL is well under COM, and that COM is centered. Spinning happens immediately after launch. Let's say 100 m. I check the flight log and no damage occurs to the rocket during launch. I was able to get it into space a couple of times last night, with some very very very nimble active controlling of the gravity turn whole spinning--done around 5000 m with a speed of 150 m/s, 220 m/s at 10 km and angle of declination of 10-15 degrees from vertical. Spinning dissipates around 70 km--end of atmosphere, and SAS can take control again. Super super weird.

[jrandom]

I've been doing very stable lifts and gravity turns, even with larger rockets, so I'm very curious to see yours. Have a link to a screenshot?

Also, you seem to be launching with the old stock atmospheric profile -- if you're only going 220m/s at 10km, you're going too slow.

This thing launched very well once I disabled gimballing on the outer engines.

[MAKC]

@ferram

http://pastebin.com/sY1kharE

some sort of unholy boeing x-37/kliper inspired partly reusable unmanned cargo craft. i jettison the fuel tank after retrograde burn to reentry. this way i have the CoM/CoL are exactly where i want them

Edited August 16, 2013 by MAKC

[Van Disaster]

Elsewhere yeah. I can guarantee COL is well under COM, and that COM is centered. Spinning happens immediately after launch. Let's say 100 m. I check the flight log and no damage occurs to the rocket during launch. I was able to get it into space a couple of times last night, with some very very very nimble active controlling of the gravity turn whole spinning--done around 5000 m with a speed of 150 m/s, 220 m/s at 10 km and angle of declination of 10-15 degrees from vertical. Spinning dissipates around 70 km--end of atmosphere, and SAS can take control again. Super super weird.

You're *way* off profile for a FAR launch - by 10km I'm probably doing 4-500m/s indicated ( maybe more, I can't go and launch to see and I've not put a rocket up for a few days ) and maybe 50deg from vertical. Full throttle off the pad and leave it there, start turning at 200m and bring it over keeping your thrust vector aligned with your velocity vector as much as you can.

When you say "spinning" do you mean rolling around the nose-tail axis? when I think of spinning aircraft they're rotating nose to tail in a relatively horizontal plane, which is probably not going to get a rocket to space. I get that frequently, usually slowly, and I've put it down to insufficiently solid rockets usually. You can try adding more fins.

[a.g.]

some sort of unholy boeing x-37/kliper inspired partly reusable unmanned cargo craft. i jettison the fuel tank after retrograde burn to reentry. this way i have the CoM/CoL are exactly where i want them

I tried making a similar construction with some additional markers added to FAR code:

http://imgur.com/a/wlMkg

The resulting observations are:

1) As you add the first part, a huge basic drag node appears and determines the CoL marker.

2) Adding more parts does not decrease the size of the node, and adds more rather big nodes. The effect of the wings is small in comparison.

3) Once the craft is saved and reloaded however, the drag nodes suddenly shrink to tiny size; some of them also change position (see cargo bays). Now the indicator is dominated by the wing lift.

This suggests to me that there may be a problem in recalculating drag from open attachment nodes in the editor.

[luckyhendrix]

Any help with the design of my VTOL plane ? the goal is to carry the middle section on the other side of kerbin.

If I maintain low AOA the plane is somewhat stable but as soon as AOA becomes to high or to low the plane tumbles

[ferram4]

@birrhan: If you're able to get it in orbit despite spinning, I gather that you're talking about spinning along the long axis of the rocket; that wouldn't be caused by anything in FAR, but by some type of asymmetry in your design, probably due to a part that is at some type of an angle that it shouldn't be. If you're using any couplers or have a large number of parallel boosters, you should look into struting those parts better and see if the problem reoccurs.

Also, your ascent profile is terrible. Start turning earlier and go faster and you'll be able to use a smaller rocket.

@a.g.: I've just added some code to my build to see if I can fix that.

@luckyhendrix: Your CoL is just above the CoM and slightly in front of it; it's supposed to be behind it. Basically, as soon as any stalling begins to happen (which looks like it will happen at very low angles with those high aspect ratio wings) your plane will start having stability problems. Try getting rid of the extensions on the front wing and see if that helps.

[Volt]

Ferram, I have a rather cheeky request which might be a big ask. Is there any chance at all that you could add a way to disable FAR aerodynamic effects for one part by adding a config string to said part's cfg file? I'm trying to use the Pirated weaponry pack's bass cannon but the rounds, as they should, tumble and slow down incredibly quickly in a FAR setup. I'd rather not remove FAR so I can design tanks!

[a.g.]

ferram4: Any comment on the flap stuff in PM?

BTW, speaking of those screenshots above, while I was unsuccessful in making those markers in the flight scene appear over the craft, some code that was left from those attempts suddenly worked when I reused the markers in SPH.

[ferram4]

@Volt: The best way to fix that is to manually add a FARBasicDragModel to the part.cfg. I'd probably go with something like this:

MODULE
{
name = FARBasicDragModel
S = 1
CdCurve
{
key = 1 0.05 0 0
key = 0 0.3 0 0
key = -1 0.05 0 0
}
ClCurve
{
key = 1 0 0 0
key = 0.5 0.05
key = 0 0. 0 0
key = -0.5 -0.05
key = -1 0 0 0
}
CmCurve
{
key = 1 0 0 0
key = -1 0 0 0
}
CenterOfDrag = 0 -0.05 0
}

The CdCurve and ClCurve are probably decent for a projectile, the CmCurve is zeroed and the CenterOfDrag is set slightly behind the part's center of mass. You can try adjusting that to make it function better, but this will allow you to fix it without waiting for one of my updates.

Realistically, the projectile is doing exactly what it should, but it needs a rifled barrel. Coding an extension of the decoupler logic to add a twisting moment on launch would fix it completely, which is probably a smarter thing to try.

@a.g.: Your suggestions were close, but not exactly right. I spent some time re-deriving the math and used that instead, but thank you for the help. It seems to work properly now.

[Volt]

Thanks for that, I'll try that out. I have unfortunately never written a line of code in my life, but yeah, it's behaving basically correctly. A rifled barrel would be pretty cool but as it stands the barrel of the bass cannon doesn't even have a collider, it's a rather barebones weapon mod!

[Pyromaniacal]

I am not sure whether or not I should use this addon. I want to put a Xenon powered flight probe on Duna, just to see if I can. It may or may not be an idea from a Youtube video. The problem is that I can't manage to get the craft out of Kerbin's atmosphere. The launch vehicles, whether spaceplane or rocket, flip spasmodically and fall victim to "Spontaneous Disassembly Syndrome". Is this a mod that can correct these odd behaviors?

[jrandom]

I am not sure whether or not I should use this addon. I want to put a Xenon powered flight probe on Duna, just to see if I can. It may or may not be an idea from a Youtube video. The problem is that I can't manage to get the craft out of Kerbin's atmosphere. The launch vehicles, whether spaceplane or rocket, flip spasmodically and fall victim to "Spontaneous Disassembly Syndrome". Is this a mod that can correct these odd behaviors?

You have to design your rockets so they work correctly with actual aerodynamics. Have any screenshots of your design? That might help us help you figure out where the problem lies.

[Pyromaniacal]

Here it is, the Dunaglider:

[Pyromaniacal]

The probe itself likes to flop about uselessly in orbit too. I'm curious to see if this will help with that. CoM, CoT and CoL all line up.

[ferram4]

You have a ton of wings at the front of the rocket, which puts the center of lift of the entire vehicle well in front of the center of mass; if it didn't flip out like mad I'd be surprised. You'd need a lot more fins at the bottom than you currently have to keep that from flipping. Considering how far in front of the center of mass the glider is, you might not be able to get the center of lift behind the center of mass without a radical redesign of the vehicle.

If you use FAR, placing a payload fairing around that glider will help reduce the stability problems you're having, since that will prevent the wings from producing any lift.

I have to assume that your statements about the CoM, CoT and CoL only apply to the glider itself; if you're talking about the entire rocket, then something is very, very wrong somewhere.

[a.g.]

@a.g.: Your suggestions were close, but not exactly right. I spent some time re-deriving the math and used that instead, but thank you for the help. It seems to work properly now.

One thing I noticed when I tried out my version is that with it deflecting flaps increased lift a lot (which according to some graphs I've found isn't unrealistic, especially at zero AoA), but drag remained rather low, so basically L/D increased with the lift. However I've read that large flap deflections in reality give a lot of lift, but decrease the glide properties. I note that the currently released flap code doesn't do anything at all with drag. Am I expecting too much drag, or is it just not included? Unlike flap lift, I couldn't find any (easily understandable) experimental numbers by a quick search.

Edited August 18, 2013 by a.g.