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

[MR4Y]

I'm still trying to replicate real life aircrafts.

Here's a badly done Blackbird:

[Delta Force]

Ferram, what plugins can you recommend for use with this? I remember earlier versions were compatible with several aircraft part sets and one of the major rocket mods.

[MR4Y]

Thanks to FAR being more realistic, here's a SpaceShip One:

[ferram4]

@m4ti410: For wing parts with built-in control surfaces I haven't added code to properly account for this yet; you'd probably want to use only FARControllableSurface though.

The way FAR here's the way FAR handles unused attach nodes:

First, get the orientation of the attach node with respect to the airflow

If it's oriented into the flow, multiply the value of drag added by the maximum pressure coefficient at that Mach number (M = 0, Cp = 1; M = 1, Cp = 1.28; M = Infinity, Cp = 1.86) This models the drag from compression on the front of the object.

If it's oriented backwards, if M > 1, divide by M²; this gives a limit on the minimum pressure coefficient and models the drag due to viscosity over the back of the object.

If it's towards the front, move the CoD to account for the little bit of positive stability given by the unused attach node.

It's possible that the main source of error is due to the way I accounted for my new part taper drag; you'll have to check it out in the next release when that is fixed.

@mdanny:

1. The main problem with mixing control axes is that the control surfaces can end up work at cross-purposes; if you try to roll right, the rudder (helping you to roll right) yaws the plane left, causing some serious dutch roll issues in every turn. What m4ti140 mentioned about ailerons being counterproductive if they act on pitch is also very true, especially with FAR at subsonic speeds: they reduce the lift of the entire wing drastically and prevent you from actually pitching up. Finally, there's the fact that having too much control authority can make planes difficult to control.
   
2. Try the trial-and-error approach: if the control system doesn't do what it's intended to do fast enough, increase the value; if it makes the plane unstable, reduce the value.
   

@Delta Force: Try out Taverius' TV Aerospace, DYJ's Procedural Wings, And Bac9's B9 Aerospace.

[MR4Y]

Is there a way to increase the attack angle of control surfaces? My SpaceShip One build can't maintain elevation after it reaches 10 Km altitude even though I'm already holding the nose up. It's CoL is way behind it's CoM.

[ferram4]

You can try increasing the angle that the control surface can rotate through.

Also, your SpaceShipOne is wrong; it should have a normal rocket engine at the back, with no intakes, and it should be carried up by another vehicle. But I'm nitpicking.

[MR4Y]

You can try increasing the angle that the control surface can rotate through.

Also, your SpaceShipOne is wrong; it should have a normal rocket engine at the back, with no intakes, and it should be carried up by another vehicle. But I'm nitpicking.

How?

As for the other thing. Yes, it's wrong, but I do'nt think KSP would be able to hold both things togheter. I can try another build with the same principle.

and if you want to be really anal about it, the back section of the SpaceShipOne wings bend up during reentry.

Edited June 17, 2013 by MR4Y

[ferram4]

In the control GUI in the editor, in the control surface tab, after you click the > to open up the option to edit the control surface options, look for the "max deflect" option. Change the number and click "update." It will now deflect up to that many degrees.

Also, it's perfectly possible for the vehicle to hold together, you just have to be careful about how you pilot it.

[MR4Y]

In the control GUI in the editor, in the control surface tab, after you click the > to open up the option to edit the control surface options, look for the "max deflect" option. Change the number and click "update." It will now deflect up to that many degrees.

Also, it's perfectly possible for the vehicle to hold together, you just have to be careful about how you pilot it.

Working on the fully SSO replica atm. Fighting pWings and not winning.

[MR4Y]

Testing SSO:

SSO with White Knight attached:

Wobble Fest, so far.

[Delta Force]

How can you compensate for thrust below or above the wing? I made a Tu-144 type aircraft (small canard in front, massive delta wing near the far back), but it keeps climbing out of control regardless of my control inputs.

[ferram4]

@Delta Force: You need to either move the CoM closer to the thrust vector or you need to use lifting surfaces to create enough of a pitching moment to balance the offset thrust vector. Or you need to reduce the thrust vector.

You could try any of these solutions:

1. Reduce the mass of the main fuselage to shift the CoM downwards towards the engines.
   
2. Tilt the engines upwards to point them more towards the CoM.
   
3. Add some positive camber near the back of your wing to help tilt the plane downwards.
   
4. Add some negative angle of attack to your forward canard to do the same.
   
5. Increase the size of the pitch control surfaces.
   
6. Carefully regulate throttle to help maintain control.
   

There's really nothing else you can do; the forces and moments must be balanced somehow.

[ialdabaoth]

@MR4Y: The link I gave for PID controllers has some info on what all the numbers mean. In short, increasing Kp and Ki will make the system respond faster, but make it less stable (read: oscillate more) and increasing Kd will cause the system to try to limit motion and make it more stable; a proper combination allows the system to respond very quickly, but without oscillations.

@Van Disaster: Make sure that the KW Rocketry parts have the proper size attach nodes; the engines might not be making the drag that they should, making the rocket less stable.

@m4ti140: The command pods already make some lift when they're oriented off of retrograde, just like all the other parts do.

@ialdabaoth: Noted, I'll test it out and release a new version of FAR with the modified ModuleManager.

Note, 1.2 was released while I had a 103 degree fever. I would strongly recommend trying with 1.3 instead.

[o_O]

Testing SSO:

Wobble Fest, so far.

Keep in mind you can attach one end of a strut to a radial decoupler thing. When decoupled the whole strut will evaporate.

[Delta Force]

Thanks for the tips Ferram. Now that I don't have to mount my engines on the centerline or wingtips I have been able to make more varied and faster designs.

Any advice on how to increase the pitch authority and/or speed on this aircraft? I almost got up to Mach 4, but I couldn't pitch up past 18,500 meters.

[ferram4]

@Delta Force: It needs larger control surfaces; those are tiny relative to the wings and unmoving canards. Also, get rid of the little winglets on the canards, they really aren't helping with drag and they make your plane less stable in yaw.

@MR4Y: Get rid of any unnecessary parts in your design; I've found that the key to building SpaceShipOne + White Knight vehicles is to try and reduce the number of parts as much as possible to reduce wobble. Try to get your spaceplane closer to the carrier vehicle so that you can get rid of the stilts it's on; that will help reduce wobble a bit. Also, try angling the carrier's wings so that the central fuselage is higher up for the same reasons.

[Delta Force]

Thanks for the help again. Is there somewhere that has information on what various types of wings, winglets, engine locations, etc. do to an aircraft? For example, I put winglets on the canards because I thought they would actually help reduce drag and increase stability (or at least that's what they do on normal wings).

[Kidneythump]

I like the idea of this mod however after installing it I'm experiencing extreme stuttering when deploying planes from the hangar. It all starts when the portrait becomes visible in the lower right corner, any way to work around this? I'm reasonably sure that it's the mod that's causing it since i installed it and the one with procedural wings at the same time and this mod seems to be the only constant...

[Van Disaster]

@Delta Force: your CoL is a bit too far back, once you go supersonic it'll go even further back - and I would hazard a guess that your CoT is above your CoM, which is going to pitch down. One mod I've found almost essential is TAC Fuel Balancer - and obviously split your plane's tanks up so you can shift fuel around.

IIRC winglets help reduce wingtip vortex drag, which I don't think is modelled here. Are you any nearer ground effect, Ferram?

[MR4Y]

@Delta Force: It needs larger control surfaces; those are tiny relative to the wings and unmoving canards. Also, get rid of the little winglets on the canards, they really aren't helping with drag and they make your plane less stable in yaw.

@MR4Y: Get rid of any unnecessary parts in your design; I've found that the key to building SpaceShipOne + White Knight vehicles is to try and reduce the number of parts as much as possible to reduce wobble. Try to get your spaceplane closer to the carrier vehicle so that you can get rid of the stilts it's on; that will help reduce wobble a bit. Also, try angling the carrier's wings so that the central fuselage is higher up for the same reasons.

Well, I need to find a way so it takes off using only two engines, as the original White Knight only has two. I opted by using TT's Mk4 jet engines. They might not look asthetically correct, but they have enough thrust to lift the whole thing off the ground.

And this is only the tip of the iceberg, as I'm yet to test the thing during reentry using the feathered wings. i'm deciding if I should use Quantum Struts to hold the wing in unfethered state, as they wobble when I pitch.

[ferram4]

@Delta Force: Some of the effects of vortex drag are simulated, but on a canard like that they don't make much sense. Also, at supersonic speeds winglets really don't help at all.

If you want an idea of how different wing shapes and locations affect airplane performance, start Google-ing information about aerodynamics; you'll quickly find information on how a wing's aspect ratio, taper ratio, sweep angle and such affect its lift and drag.

@Kidneythump:

How to report a bug so I can fix it in a timely manner:

1. Narrow down the plugins and mods that you are using until you can re-create the issue; if the issue is with FAR alone and you're running other plugins narrowing down the source becomes more difficult.
   
2. Recreate the issue using the smallest craft possible; this leaves fewer options for the source of the error.
   
3. Post detailed and specific instructions on how to recreate the bug, along with the entire output_log and the problem craft; this will allow me to easily recreate the bug on my end.
   

If nothing shows up in the log, then it's probably just all the initial math that needs to be done to set up the aerodynamics combined with KSP loading the entire scene. If that's the case then you're not going to be able to get around it unless you consider waiting a few minutes "getting around it."

@Van Disaster: I tried modelling ground effect a few releases ago; it wasn't noticeable at all. So I'm not bothering to reduce computational overhead.

[Van Disaster]

Did it ever make it to a public release? I wouldn't mind going and fiddling if you can remember which one it was. Was that the cushioning or the vortex breakup or both? seems wierd there was *no* noticeable effect.

[Esulin]

I'm trying to figure out aerobreaking with FAR.

I've found the aerobreaking calculator at http://alterbaron.github.io/ksp_aerocalc/ but I can't seem to figure out how to calculate the drag coefficient, which I understand is calculated differently in FAR than in vanilla KSP.

MechJeb seems to show a 'drag coefficient' value (had to add this from the custom window editor) but the values don't make sense. Most of the stuff I've got has a D.C. of 0.001 - 0.002 and a lander that I've got Jeb returning from Minmus in has 0.000, which really doesn't help me to calculate how to get him safely into a stable orbit.

So, can someone tell me how to calculate drag in FAR?

[Bloodbunny]

Seems that Ioncross Crew Support gets borked by FAR for some reason.. my CO2 kept going up with scrubbers activated.. disabled FAR and went back to working as normal...hmmm

[Autochton]

I'm trying to figure out aerobreaking with FAR.

I've found the aerobreaking calculator at http://alterbaron.github.io/ksp_aerocalc/ but I can't seem to figure out how to calculate the drag coefficient, which I understand is calculated differently in FAR than in vanilla KSP.

MechJeb seems to show a 'drag coefficient' value (had to add this from the custom window editor) but the values don't make sense. Most of the stuff I've got has a D.C. of 0.001 - 0.002 and a lander that I've got Jeb returning from Minmus in has 0.000, which really doesn't help me to calculate how to get him safely into a stable orbit.

So, can someone tell me how to calculate drag in FAR?

It's tricky. Depending on your attitude to the oncoming airstream, your drag can vary quite widely. Generally your lowest drag will be nose into the wind, so basically flying straight into your prograde marker. Your highest drag will likely be belly-on (or back-on), so with your craft's vertical axis pointed prograde, since that will present, in most aircraft designs, the largest cross section. Calculating them, though... Not easy. Can't really help there.

Edit to add: One thought is to go into the SPH/VAB, and orient your craft the way you expect it to be when doing the maneuver. Then use the CAS to find your Cd?