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

[thorfinn]

@Nathankell: What does KJR do that Squad still does not? Because I use it, on .23.5 also used Stupidchris' rebalance that makes many things physicsful again, and had no wobble problems of any kind...

[NonWonderDog]

Honestly I just do this and am happier:

@PART[*]:HAS[#PhysicsSignificance[1]]:FINAL
{
    @PhysicsSignificance = 0
}

No problems so far, but on a fast-ish desktop.

You can also give landing gear mass with Firespitter:

@PART[SmallGearBay]:FINAL {
    // If it's going to have a mass, it should be much lower
    @mass = 0.075

    // Replace the main landing gear module
    @MODULE[ModuleLandingGear] {
        @name = FSwheel
        hasMotor = false
        motorEnabled = false
        deployedDrag = 0.4
    }

    // also make the landing light draw power
    @MODULE[ModuleLight] {
        %resourceAmount = 0.04
        %useResources = true
    }
}

Edited August 13, 2014 by NonWonderDog

[NathanKell]

ThorFinn: ferram would have an actual answer; all I can tell you is "it stiffens things up a lot still."

[Galenmacil]

@Galenmacil:

1. I cannot confirm. Testing on the stock FAR Thunderbird craft resulted in ailerons (behind the CoM) deflecting as expected: a roll left command resulted in the left aileron deflecting upward (to produce a downward force) while the right aileron deflected in the opposite direction.

Thanks for your reply ferram4.

I do not want to be rude but seems to me that either you or me got the control surface aerodynamic logic messed up. Here a bunch of picture showing what I consider to be wrong currently in FAR/KSP. Please, prove me wrong if I am.

Neutral control position. Just as reference:

Pitch up input as in "pulling back on the stick to climb":

Everything as expected here. Rear control (behind CoM) deflect up and canard deflect down (in front of CoM).

Pitch down input as in "push forward on the stick to dive":

Again, everything as expected. Rear control (behind CoM) deflect down and canard deflect up (in front of CoM).

So far, rear control are okay for pitch up and down only commands. To pitch up, the rear control needs to deflect up and the front control needs to go down. Inverse to pitch down. This is as I always believed it should work. Now let's see what I think is wrong with the next two pictures:

Roll left command as in "move the stick to the left to bank left":

Okay, so from the first two pictures we learned that to produce downward force, the rear control needs to go down. Logically, to roll left, the rear left control should deflect down and the rear right control should deflect up to produce adequate force. Similarly, the left canard should deflect up and the right canard should deflect down to produce adequate force to roll left. As you can see in this picture, the rear control do not deflect correctly. They are reversed. The canard show logical deflection thought.

Finally, roll right command as in "move the stick to the right to bank right":

Again here from the first two pictures we learned that to produce upward force, the rear control needs to go up. Logically, to roll right, the rear left control should deflect up and the rear right control should deflect down to produce adequate force. Similarly, the left canard should deflect down and the right canard should deflect up to produce adequate force to roll right. Again, reversed and consistent with the behaviors shown in picture number three.

I submit this argumentation with due respect and I assume that, considering I am wrong, you will point out and explain why.

Thanks

Edited August 14, 2014 by Galenmacil
Testing with image not showing in post...

[Master Tao]

Galenmacil,

Control surfaces can be counterintuitive. I'll try to explain, but the best way to understand them is to cut control surfaces into paper airplanes. Paper helicopters can help, too.

Control surfaces in real life and FAR don't provide force, but instead increase change the shape of the wing, tailplane, or vertical stabilizer. That shape change increases or decrease lift. Ailerons (roll control) deflect up to decrease lift on that side and down on the other side to increase lift. To emphasize: they're not pushing the wings, but changing wings' shapes. Elevators (rear pitch controls) deflect up, decreasing tail lift, pitching the plane up.

Edited August 14, 2014 by Master Tao
rewrite

[tetryds]

Yeah, not just increase drag, they also create lift.

Pretty much what Master Tao said.

If you think a bit more it makes total sense, like when you move your hand on the wind.

And when you pitch with S you make your nose go up, they seem to be reversed because to pitch up you need a downwards force on the back, or upward force on the front.

To rotate it's the same thing, imagine a lever.

You apply downwards force on one side and upwards on the other, which creates a torque.

[Renegrade]

Control surfaces in real life and FAR don't provide force, but instead increase drag. That increased drag causes the plane to turn the opposite way. Ailerons (roll control) deflect up, causing the same side to move down and vice versa. Elevators (rear pitch controls) pitch up, causing the tail to move down, pitching the plane up. Canards (forward pitch controls) pitch down, causing the nose to rise, pitching the plane up.

What, really?

I've always interpreted it as a force/lift, and it seems to work for me...

To use Galenmacil's template:

Pitch up command: canards pitch up, increasing their AoA, generating more lift at the front, elevators/elevons pitch down, decreasing lift (or even becoming a downward facing 'lift'..a .. fall? push?). That creates torque around the CoM, in the direction of pulling the nose up.

Pitch down command: the reverse of above.

Roll left command: both canards and elevons pitch down on the left side, decreasing their AoA, reducing lift/making negative lift, and they pich up, creating positive lift on the right side, again creating a torque around the CoM that rolls the plane to the left.

Roll right command: the reverse of above again.

Of course the first controlled plane I ever flew had a single elevator on the.. .right side only? and a rudder, so I might view things weirdly~

[Master Tao]

I've always interpreted it as a force/lift, and it seems to work for me...

Yes, there's a little bit of lift involved, but most of the force is drag, whereas stock control surfaces produce magical anti-deflection force. I think that's easiest to see with the paper helicopter, which produces very little lift, but spins due to high differential drag across the vertical axis.

Of course the first controlled plane I ever flew had a single elevator on the.. .right side only? and a rudder, so I might view things weirdly~

What was that plane? It makes the Curtis Ascender sound... sane.

[tetryds]

Yes, there's a little bit of lift involved, but most of the force is drag...

From what I knew most of the effect would come from the difference on lift.

Can you please link some source? I would like to know more about this.

Edited August 14, 2014 by tetryds

[Master Tao]

NVM, you're right. It is lift. Someone must have explained it to me incorrectly ages ago.

Edit: fixed, so hopefully there won't be too much confusion. Thanks.

Edited August 14, 2014 by Master Tao

[Kethevin]

This is an interesting mod and I'm wondering if I should try it. I'm pretty good with rockets, but my space plane skills have a long way to go. Would you recommend me trying the mod now or waiting until I have improved my flying without it first?

[Master Tao]

I'd recommend trying this or NEAR. You'll mostly develop bad habits flying with stock aerodynamics. I find planes much easier to design and fly with FAR, but stock aerodynamics frustrated me by differing so much from my experience with airplanes.

[Wanderfound]

This is an interesting mod and I'm wondering if I should try it. I'm pretty good with rockets, but my space plane skills have a long way to go. Would you recommend me trying the mod now or waiting until I have improved my flying without it first?

FAR makes planes fly like planes, which for me is much more intuitive. But FAR makes you worry about aerodynamic failure, while with NEAR you can slam your plane sideways into the airstream as much as you like. Give 'em both a try and see which is more fun for you.

[Kethevin]

Thank you, I'll check them both out right now. :-)

[Renegrade]

What was that plane? It makes the Curtis Ascender sound... sane.

It's a House of Balsa entry-level, two-channel glider kit. It's called the "Two by Four" and had a plywood fuselage (made from pines I think?) and a pine dowel for the main wing spar. The rest was balsa wood.

The one I had would be about oh, twenty years old now, but they seem to exist still:

http://www.houseofbalsa.com/store/store-type-tem/k-26.html

It flew okay, although it's extra-sturdy construction made it kinda heavy. Basically the rudder would induce sideslip, but it was fairly tame so it would just gently roll to that same direction. All that nice dihedral and high-mounted wing made it very tame overall.

NVM, you're right. It is lift. Someone must have explained it to me incorrectly ages ago.

That happens to everybody, no problemo

FAR makes planes fly like planes, which for me is much more intuitive. But FAR makes you worry about aerodynamic failure, while with NEAR you can slam your plane sideways into the airstream as much as you like. Give 'em both a try and see which is more fun for you.

You can turn aero failures off (or turn them down) using FAR's nifty menu system.

[taniwha]

Or you can accept the challenge of building a plane to withstand the forces.

[TheGatesofLogic]

Anyone know a good way to dampen roll on a FAR rocket. My rocket is extremely stable until the boosters are ejected, but then immediately afterwards roll becomes ultra sensitive and there is no way to stably correct it. It's not that it has a tendency to roll, but rather that any roll correction I make is WAY over compensated for. Here's an image:

edit: by roll i mean in the aircraft sense, as in a moment about the axis of travel.

edit 2: nevermind I solved it, and that rocket was way overbuilt, was only meant to lift that payload to orbit and when it got there it still had 4000 m/s of dV left...

Edited August 15, 2014 by TheGatesofLogic

[Mandelbrot]

I just wanted to post to say thank you Ferram. During the first time I really got into playing with FAR, my rocket broke up in the atmosphere, and the way it sort of tumbled away under me as I fired up an upper stage -- I just cannot go back to stock now. It really even makes the game look better. Hope you don't mind a post just to say thanks!

[Sevio]

Hi Ferram,

I noticed your development update to the FAR github and decided to test it out, both with my test plane and the plane that originally had the issue with. Both planes now work entirely as expected (I was able to do the reentry and landing successfully with the spaceplane), so thank you for the fix

You probably already know but I figured I'd report it anyway: During a test flight with my spaceplane, I did spot an issue where the FAR in-flight window disappears during flight, couldn't see anything in the log indicating what went wrong though.

In any case, happy with the fixed control surfaces, keep up the good work!

[LostOblivion]

I'm making an SSTO lander for Duna. On Kerbin 1 atm it has a terminal velocity (according to FAR) of around 105… and around 200 on Kerbin 0.2 atm (Duna equiv). (Quite low, in other words.) Most places, I see people stating you need around 1500 to 2000 dV to get back into orbit after a landing on Duna. My question is, how much does FAR change this assumption? Will my very badly aerodynamic lander need more or less dV to get into orbit with FAR?

[AndreyATGB]

Still lower than stock, but not much. You should be able to get to a low orbit with 1500. Duna's atmosphere is thin so you don't need to worry much about aerodynamics. It's gonna be harder for Laythe or Eve though, it's tough to make something go down and up and be stable both ways.

[LostOblivion]

Great, thanks! :-)

[Kolago]

Is there a way to add an Max-Q data field into the Flight Data display? Not a pre calculated value but Max-Q actually experienced in the current flight.

Edited August 15, 2014 by Kolago

[Renegrade]

Or you can accept the challenge of building a plane to withstand the forces.

I don't think that's actually possible. The only way to prevent aerodynamic failures is by slow and/or careful flying.

I was performing Mach 4+ tests at sea level with aero failures on (and DCA off) prior to the engine nerf without breaking anything with 400KPA of dynamic pressure trying to kill me.... so technique definitely works.

Now I just gotta figure out the technique for re-entering a spaceplane...

[undercoveryankee]

Anyone know a good way to dampen roll on a FAR rocket. My rocket is extremely stable until the boosters are ejected, but then immediately afterwards roll becomes ultra sensitive and there is no way to stably correct it. It's not that it has a tendency to roll, but rather that any roll correction I make is WAY over compensated for.

<image snipped>

edit: by roll i mean in the aircraft sense, as in a moment about the axis of travel.

edit 2: nevermind I solved it, and that rocket was way overbuilt, was only meant to lift that payload to orbit and when it got there it still had 4000 m/s of dV left...

I've seen roll oscillations fairly regularly. I think it's because a typical rocket has a smaller moment of inertia in roll than in pitch or yaw, so the same deflection of the control surfaces is enough to produce a lot more angular acceleration. On anything with reaction wheels in it, I just disable the roll axis on the fins entirely. Sluggish roll response is better for a booster than oscillations.