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

[phoenix_ca]

Is there a guide for setting up flaps? I keep seeing the option but I don't know how to set it up in the SPH.

I sure wish there was. I've never gotten them to work. Actually I haven't seen the point. Instead of adding extra lift each time I've tried to use them they've acted more like elevators and pitched the nose down hard. O.o

[Kalista]

I sure wish there was. I've never gotten them to work. Actually I haven't seen the point. Instead of adding extra lift each time I've tried to use them they've acted more like elevators and pitched the nose down hard. O.o

Same with me they always behaved more like dive brakes than flaps for me.

[Gaugeforever]

The biggest thing you can do is to use struts to stiffen whatever the wheels are attached to. It doesn't matter if the wheels are straight if whatever they're attached to flexes. (and if it does, it'll be asymmetrically because of the bug NathanKell linked, which has been around for as long as I can remember and is why it always goes in the same direction on the same plane.)

I also use Multiwheels Landing gear (many versions old though they be), which have the ability to slip realistically (complete with resulting smoke clouds!) They also have a much better than average suspension, which is also helpful.

I feel silly but this ended up being user error. The bug you guys mention probably exists, but it wasn't the problem I was having :/ Stupid me.

[BudgetHedgehog]

Ferram, sorry if this has been asked before, but is there a way to disable aerostress destruction on a certain part, rather than globally? I want to make an attack helicopter with KAX but am worried about FAR ripping off my rotor blades.

[Volt]

I sure wish there was. I've never gotten them to work. Actually I haven't seen the point. Instead of adding extra lift each time I've tried to use them they've acted more like elevators and pitched the nose down hard. O.o

Your flaps are increasing the amount of lift at the point at which they are fitted, moving your center of lift backwards. A simplified explanation of the effect of this is that the center of lift 'pivots' the aircraft about the center of mass. The further the force assumed to apply by the center of lift is from the pivot point, the larger the pivoting effect, or moment. Moment = Force x Perpendicular distance, and the distance has increased, so the force pushing the tail up and nose down is larger. Try moving your wings forward a little if you can still safely trim it out, so the flaps don't move the center of lift quite as far back. I'm sure Ferram can offer better advice than me, though.

Whatever happens, deploying flaps will require a change in trim. The question for your design is if you have enough pitch authority to safely overcome the change in nose-down moment.

[phoenix_ca]

Your flaps are increasing the amount of lift at the point at which they are fitted, moving your center of lift backwards. A simplified explanation of the effect of this is that the center of lift 'pivots' the aircraft about the center of mass. The further the force assumed to apply by the center of lift is from the pivot point, the larger the pivoting effect, or moment. Moment = Force x Perpendicular distance, and the distance has increased, so the force pushing the tail up and nose down is larger. Try moving your wings forward a little if you can still safely trim it out, so the flaps don't move the center of lift quite as far back. I'm sure Ferram can offer better advice than me, though.

Whatever happens, deploying flaps will require a change in trim. The question for your design is if you have enough pitch authority to safely overcome the change in nose-down moment.

Or I could just not be a derp and not try to use them on a plane that only has elevons for pitch control in the first place. A very d'oh moment when I realized that pretty much all my aircraft I've made since installing FAR have had huge delta wings reminiscent of Concorde. Very, very stable, but flaps don't behave in the same way as a more conventional wing at all. Hrm. Maybe I could get away with small amounts of deflection on those control surfaces.

[DivisionByZero]

FALSE ALARM. I don't understand the intended use of flaps and spoilers, but I did find a "creative" way to use them in KSP.

I figured out flaps and spoilers. They work great together. They are nasty separately. I have a post in general add-on affairs if you want to read my long explanation. No more need for those air brake things, I think.

Edited May 17, 2014 by DivisionByZero

[Tiron]

Someone on IRC has been setting up flaps on the *underside* of the wings instead of the back, and says it works very well. I don't think I could get over the weirdness of how it would look, though, so I haven't tried it. I normally just don't bother with flaps, or maybe set up a few control surfaces I'm not really using as flaps. Almost all my planes are Deltas.

Exception being the big rover carrier SSTO, which used the huge B9 Transport wings. I had a fair portion of its control surfaces set up as flaps, and that seemed to work fine.

Also, they configure like any other control surface. You use tweakables in the SPH to set what axes it works on and the range. You seem to be able to set up stuff to work as control surfaces *and* flaps simultaneously now, which you couldn't pre-tweakables.

Edited May 17, 2014 by Tiron

[quasarrgames]

Hello! I was thinking of downloading FAR, but i just have one question:

I know FAR makes pancake rockets have more drag, but it also makes the lower atmosphere have less drag.

So i'm just wondering, would a pancake rocket have a lower terminal velocity in the lower atmosphere, or would it be about the same, or what?

[Lexx Thai]

FAR have trouble with reverting to launchpad: wings and control surfaces becomes "dummy plates" on next launch (surfaces moves, but do nothing). Also, KSP begins spamming to log with "MissingMethodException: Method not found: 'ferram4.FARWingAerodynamicModel.GetStall'."

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Guys, sorry for my grammar.

Edited May 17, 2014 by Lexx Thai

[NathanKell]

Yep, the fact that control surfaces and wings sometimes get set to shielded on revert is a known issue. (I *think*; at any rate it happens to me too and I think ferram knows about it.)

[Motokid600]

Hello! I was thinking of downloading FAR, but i just have one question:

I know FAR makes pancake rockets have more drag, but it also makes the lower atmosphere have less drag.

So i'm just wondering, would a pancake rocket have a lower terminal velocity in the lower atmosphere, or would it be about the same, or what?

Uhm.. it's kinda moot. A pancake design simply won't work at all. You'll flip around after a thousand meters off the pad when you start to pitch over. Gotta build rockets that look more like real life. .. to an extent.

[NathanKell]

Meh, if you're careful with your angle of attack and sideslip, and have sufficient gimbal authority, you should be ok with a statically-unstable vegetable launcher. You'll suffer comparatively horrendous drag losses (although probably *still* less than stock's soupodynamics), and you'll have to start your turn exceptionally early and be very careful, but you should be ok.

Note that terminal velocity is unreachable, no matter the rocket, assuming you have a sane TWR. Don't worry about terminal velocity unless you plan to launch with a 2.5TWR and burn out at like 20Gs; but then, what should be worrying you is your TWR anyway.

[mdgates]

"Terminal velocity" refers to the airspeed at which drag equals weight, and you can reach it going straight up with TWR=2, or straight down with TWR=0. Another real-world concept misused by Kerbonauts.

But to answer Quasar: the thinner atmosphere makes your terminal velocity much higher, but that's the wrong question to ask. You can put nosecones on the top and fins on the bottom, and still go to space with a pancake. But the more realistic aerodynamics will drive you toward more realistic designs. I'm enjoying FAR, and I recommend it to those who would like to add a bit of complexity and immersion to the design process.

[NathanKell]

FAR has a terminal velocity readout. I'd be interested to see you hit it with a constant 2.0TWR, going straight up.

[Tiron]

it'd probably still have a higher overall terminal velocity... FAR really dramatically reduces drag in almost all cases.

The problem you'd have is not so much the drag, as the fact that it'd be aerodynamically unstable. You'd almost certainly lose control of it trying to gravity turn it, and then the aero stress might very well tear it apart.

[DaMichel]

You guys are aware that with FAR like in the real world, terminal velocity depends on the vehicle mass and surface area? Think of a falling parachute vs. a falling steel ball with equal masses. Stock aerodynamics would make both fall with the same terminal velocity which is super silly

P.S. I would like to see a comparison between stock & FAR pancake rockets as well. I guess you could reach terminal velocity if you make a rocket with really high drag, like some asparagus staging pancake monster, but keeping it under control will be a problem.

[phoenix_ca]

You'd have to be crazy to make a pancake rocket in FAR.

[AndreyATGB]

Terminal velocity will still be higher, but without an aerodynamic rocket you're gonna have to go straight up until you're out of the atmosphere then burn sideways which is extremely inefficient and will cost you a lot of delta-v. That is unless you're carrying KSPI transmitters which act like giant umbrellas, you're not getting to orbit without a fairing.

[KerikBalm]

Can anyone tell me why "wing pieces at wingtip make less lift and more drag than ones at wing root"

This would imply that low aspect ratio wings are better than high aspect ratio wings.... which seems a$$ backwards

[8749236]

Now the wings are tearing off so easily...

Can't fly any aircraft at speed at mach 1+ with less than 5 degrees of AoA...

Unless I attach tons of structs on to it...

Did I do something wrong?

[Tiron]

Now the wings are tearing off so easily...

Can't fly any aircraft at speed at mach 1+ with less than 5 degrees of AoA...

Unless I attach tons of structs on to it...

Did I do something wrong?

You're flying too low to be doing that kind of speed, is all. The higher you go the less air pressure there is, and thus the lower the dynamic forces are at any given speed. Get up around 25 km and you can do around mach 5 or 6 depending on your engines, and not break anything unless you TRY to.

[phoenix_ca]

Can anyone tell me why "wing pieces at wingtip make less lift and more drag than ones at wing root"

This would imply that low aspect ratio wings are better than high aspect ratio wings.... which seems a$$ backwards

I'd assume that is an approximation of the vortices that are created at a wing tip. But that's just a guess.

Edited May 18, 2014 by phoenix_ca

[camlost]

Can anyone tell me why "wing pieces at wingtip make less lift and more drag than ones at wing root"

This would imply that low aspect ratio wings are better than high aspect ratio wings.... which seems a$$ backwards

That is the result of calculation using lifting line theory.

KSP uses arbitrary coefficients to calculate lift for each part, then sum them up. FAR uses aerodynamic equations to calculate lift. So low AR wings and high AR wing are different, while in stock KSP they are the same.

[phoenix_ca]

That is the result of calculation using lifting line theory.

KSP uses arbitrary coefficients to calculate lift for each part, then sum them up. FAR uses aerodynamic equations to calculate lift. So low AR wings and high AR wing are different, while in stock KSP they are the same.

That's a much cooler answer. I like.