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

[Romuless]

How do I decrease "Lp" to negative? I think... and I know almost nothing obviously that I should put more ability to control the roll somewhere via control surfaces vertically or something, but I don't know for sure I like your mod but it's obviously extremely confusing to someone who knows literally nothing about aerodynamic terminology.

[BudgetHedgehog]

One thing that bothers me however is how the deltav requirements to get into LKO drops from 4500dv (stock) down to 3100dv or maybe less with FAR. For me it shifts the game balance a bit too much.

dV to LKO (stock) - 4400 m/s

dv to LKO (FAR) - 3300 m/s

dV to LEO - about 9500 m/s

FAR isn't OP, Kerbin is. You're only talking about 1km/s less, really not that much, all things considering. If anything, it highlights just how weird Kerbin is (scale, density, it's atmosphere etc).

[forsaken1111]

It should also be noted that this reduction is only for nice aerodynamic rockets. If you launch a brick, it should be much harder.

[BudgetHedgehog]

It should also be noted that this reduction is only for nice aerodynamic rockets. If you launch a brick, it should be much harder.

That too. While watching Robbaz's latest VSP video with The Cube, my only thougt was 'how the hell is that getting into orbi.. oh yeah, no FAR'.

[DuoDex]

I heard that Mechjeb works with FAR. What's the word on that?

[Wanderfound]

I heard that Mechjeb works with FAR. What's the word on that?

http://forum.kerbalspaceprogram.com/threads/60933-Optional-MechJeb-Modules-for-FAR-NEAR-km_Gimbal-(Sept-7)

Word.

[ThorBeorn]

Ferram4: I want to make a suggestion. I build a lot of aircraft, sometimes replicating real life counterparts which includes part clipping to achieve the various fuselage shapes etc.

Now, I know it's possible to turn off drag for parts one at a time while piloting the aircraft. But it would be really nice to turn off drag in the SPH/VAB. If this setting could somehow be saved in the craft file it would be really neat IMO.

Two reasons for this. One, it get's tedious to turn off drag for a bunch of clipped parts every time you launch a vehicle. Two, if the FAR GUI could take this into consideration while in the VAB, it would be easier to predict how your plane flies.

[peachoftree]

My game lags a lot; what's going on?

First, check your debug log in game (ALT + F2) to see if any errors are appearing (NullReferenceExceptions are the most common, but anything in red is bad). If there are, then follow the guide below for reporting a bug.

there is no bug reporting guide below this.

[planes]

"Lift coefficient increases for a given angle of attack as Mach number increases, drag coefficient increases to a peak at Mach 1 and then drops off, as in real life." no. lift coefficent decreases because the amount of lift at any given angle of attack rises as speed rises. drag coefficent increases increases by the square due to wave drag. please add these details, because that would make this add-on a lot better. Thank you.

[Kitspace]

What is going on with the new version that is already discussed and shown in a few places around?

[ferram4]

ThorBeorn: That feature was removed after experiments showed it interfered with other aspects of FAR. It will not be coming back in any form.

@peachoftree: Noted, fixed with link to support guide.

@planes: At a given AoA, lift coefficient increases due to compressibility effects; drag coefficient remains steady until reaching the transonic regime, where it spikes up before coming back down on the other side of Mach 1 where there are fewer separation effects. This is common stuff taught in pretty much every aerodynamics textbook that covers compressible flow. Perhaps you neglected to read the part that mentioned, "at a given angle of attack" indicating that it was not considering how much lift necessary to keep a plane in the air.

Also, all of the details you are thinking of are already accounted for.

@Kirspace: That's a dev version that is not ready for full release.

[Drew Kerman]

Tried my hand at planes again. Still suck. After a day of beating this thing around would like to post for some direction anyone would like to share. Decided the C-130 would be a good airframe to emulate, hence the creatively-named K-130. I did not install RealFuels or Advanced Jet Engine, but I'm willing to if anyone thinks they will help. I'd like to think my overall design is sound and I just need to figure out how to tweak it to perform better, but I could also be missing something important. Another note is that I derived the FAR values for these lifting surfaces myself a while back, although they were vetted by Ferram so I don't think their .cfg is an issue. They are also wet wings. The LLL cargo fuselage and tail barely weigh as much as the cockpit, so that could also be another factor, and why I stuck a fuel tank in there to help move the CoM back further towards the CoL without having to shorten the fuselage. Although, given as I'm not using the cargo space for anything really, taking out a section would just make it look stubby but I can live with that. More comments in the gallery. Let me know what other information would be helpful. Thanks, plane gurus!

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[ferram4]

Well, I must say that's impressive. At low speeds you have managed the almost-unthinkable job of making your plane statically stable in pitch, but dynamically unstable. Good job, that takes work!

Okay, the airframe looks decent, though I'd probably say that the slope of your moment coefficient (in the static analysis) is a little steep, which probably makes pitching difficult. To fix that, you might benefit from moving the horizontal tail forward a bit, reducing its size, increasing the size of the elevator on that (not sure how you'd do that, but it will help) or build some negative angle of incidence into it to make it easier, since I doubt you're looking to dogfight with this guy.

The yawing and rolling are probably due to some minor asymmetry somewhere on the design. The usual suspect is the vertical tail not quite being straight; general solution there is to mount it somewhere where it is straight, get Part Angle Display and use that to guarantee that it's straight, or go for two vertical tails which should balance out. Even if it looks straight, sometimes it's not.

It might also be smart to drain the wings and run the fuel from the fuselage, since that will shift your CoM back a bit.

[NecroBones]

I apologize if this is asked and answered frequently, but I have a quick question. I looked at the info on the OP, and I think I have all the answer I need, but I just want to be sure--

People are starting to ask if my mods work with FAR/NEAR. I'm telling them "yes", because as far as I can tell, everything looks OK. Is there anything special I need to do, for parts packs that don't include wings?

I have a general parts pack with fuel tanks, nose cones, and some radial parts that are fairly aerodynamic in shape. I'm assuming the collision mesh matters more than the model, but I don't know if that's accurate.

My second mod is a fairings set, using the stock engine-fairing module to create payload fairings. My test launches flew straight with FAR, at least until I intentionally staged the fairings at > Mach 1 to watch it tear apart.

Part of the reason I'm asking though, is that I have collision-mesh gaps to accommodate decoupling, since the nose-cones are optional and the fairings can be used "inline" with diagonal top surfaces. Here's an image, with lines drawn to show where the collision mesh edges are (below).

So I guess my question boils down to-- what determines how aerodynamic something is? The collision mesh? the model? This will help me in continuing to design these parts for compatibility.

[Drew Kerman]

Well, I must say that's impressive. At low speeds you have managed the almost-unthinkable job of making your plane statically stable in pitch, but dynamically unstable. Good job, that takes work!

Well like I said I did spend all day on it

Okay, the airframe looks decent, though I'd probably say that the slope of your moment coefficient (in the static analysis) is a little steep, which probably makes pitching difficult. To fix that, you might benefit from moving the horizontal tail forward a bit, reducing its size, increasing the size of the elevator on that (not sure how you'd do that, but it will help) or build some negative angle of incidence into it to make it easier, since I doubt you're looking to dogfight with this guy.

Yea, the yellow line has been bugging me. By negative angle of incidence you mean tilting the horizontal stabilizers downwards a bit correct?

The yawing and rolling are probably due to some minor asymmetry somewhere on the design. The usual suspect is the vertical tail not quite being straight; general solution there is to mount it somewhere where it is straight, get Part Angle Display and use that to guarantee that it's straight, or go for two vertical tails which should balance out. Even if it looks straight, sometimes it's not.

The fin is place with 90 degree snap, but I do have Part Angle Display and will double check it. Could it indeed be the engines as RCS Build Aid showed?

It might also be smart to drain the wings and run the fuel from the fuselage, since that will shift your CoM back a bit.

Worth a shot. Thanks!

[NecroBones]

Oh, and one follow-up question-- The jet-engine nerfs. Are they applied to all jet engines (that is, those included in other mods and parts packs)? Or do I need to add settings for FAR/NEAR in my custom jet engines?

Thanks.

[Master Tao]

Oh, and one follow-up question-- The jet-engine nerfs. Are they applied to all jet engines (that is, those included in other mods and parts packs)? Or do I need to add settings for FAR/NEAR in my custom jet engines?

Thanks.

There are specific nerfs for the stock engines, and another nerf that applies to all air breathing engines, so it affects the B9 SABRE in air breathing mode, but not rocket mode.

[Infinity00]

Well like I said I did spend all day on it

Yea, the yellow line has been bugging me. By negative angle of incidence you mean tilting the horizontal stabilizers downwards a bit correct?

The fin is place with 90 degree snap, but I do have Part Angle Display and will double check it. Could it indeed be the engines as RCS Build Aid showed?

Worth a shot. Thanks!

It's a long shot, but I noticed you are building a turboprop plane; is the natural torque of the propellers modeled. If so, that's what is causing your instability. Propeller driven aircraft naturally exhibit some roll, which is typically compensated for in the airframe's design (See Sopwith Camel for early aircraft builders' experiences with torque).

Like I said, a long shot, but possible.

[Juncoph]

Looks like my question got eaten up by the trials of time--

Do winglets actually help realistically, or are they just rudders like in stock KSP?

[Taki117]

Looks like my question got eaten up by the trials of time--

Do winglets actually help realistically, or are they just rudders like in stock KSP?

Not sure what you mean. Winglets are wings where the entire wing is a control surface, they work best as rudders or canards, but if your aircraft is sufficiently small they could be your wing.

[Wanderfound]

Not sure what you mean. Winglets are wings where the entire wing is a control surface, they work best as rudders or canards, but if your aircraft is sufficiently small they could be your wing.

To demonstrate:

[Drew Kerman]

It's a long shot, but I noticed you are building a turboprop plane; is the natural torque of the propellers modeled. If so, that's what is causing your instability. Propeller driven aircraft naturally exhibit some roll, which is typically compensated for in the airframe's design (See Sopwith Camel for early aircraft builders' experiences with torque).

Like I said, a long shot, but possible.

Maybe - see the album, I include an RCS Build Aid shot that is showing me torque moving the aircraft to the right. I think the torque effect is mainly for single-engine planes however, since the torque is directly inline with the aircraft's longitudinal axis.

Well, was able to spend some more time on the K-130 today and here is where I am at now:

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Another change I made was to lighten the cockpit from 3t to 2.75t - at the same time I removed the torque wheels for the weight loss. I wasn't using them anyways. This made my CoM shift back even further towards the CoL

I found that dumping fuel from the wings actually shifts the CoM back forward, so kept the fuel in.

Flew three pattern flights tonight and she handles pretty damn well. No stalls, smooth takeoff - with flaps at 2 she'll pitch up at around 80m/s but not actually leave the ground at max pitch until around 110m/s. Landing is great once I got the hang of it. I have hundreds of hours logged in Flight Simulator and I use the X52 controller so didn't take me long to figure out a good glide path and work the throttle properly on final approach to control my vertical speed.

Actually my second landing was even smoother than my third one - of course I didn't video that one.

I'm also going to ask Lack if he will consider shortening the tail. This section specifically.

Any other suggestions?

[Entropius]

Ferram, could it ever be technically feasible for FAR to predict the aerodynamics of not the whole craft, but of just a future stage of the craft? I'm curious because if it could be done, then Atmospheric Trajectories could then figure out a reentry path of a capsule without having to decouple the capsule from the craft (possibly at the expense of losing one's engines).

I'm guessing the answer is no, but I thought I'd ask just in case.

[Dirt Diver]

does anyone have version 0.13.1 for 23.5, i have literally looked everywhere and cant find it

[tetryds]

@Gaiiden: the torque will happen as long as all the propellers spin at the same direction, even if they are not inline with the craft.

It will happen even if you have propellers spinning at different directions but one slightly slower/lighter/smaller.

That is how they control quadcopters yaw.

But the heavier the aircraft, and further from the middle the weight (fuel on wings) is, and further from the middle the propeller is, the smaller the effect.

Btw, what is the problem with the tail?

Edited September 25, 2014 by tetryds