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

[Surefoot]

Curious with all the numbers added by MM to the wings etc. is that I was able to gain altitude while screaming at 2km/s+ through Kerbins atmosphere by simply raising the nose of my lander above the horizon - no control surfaces involved.

If you have enough TWR, you can make a brick fly, even into orbit.. I recall seeing (was it in a movie ?) someone telling this precisely about the F-4 Phantom, which has poor aerodynamics but so much thrust it doesnt matter... As for control, it's the reaction wheels, provided your lander didnt have a much stronger opposing moment.

[Hodo]

If you have enough TWR, you can make a brick fly, even into orbit.. I recall seeing (was it in a movie ?) someone telling this precisely about the F-4 Phantom, which has poor aerodynamics but so much thrust it doesnt matter... As for control, it's the reaction wheels, provided your lander didnt have a much stronger opposing moment.

Most modern fighter planes are pretty poor gliders. I think the F-16s glide characteristic was something like for every 1000ft you might go a half mile.

[ferram4]

@KerbMav: FAR makes a tank more aerodynamic when it has a nosecone by adding extra drag to unused attach nodes when there is no part attached there.

Also, congratulations on building a lifting body; at ~2km/s pretty much anything will make significant lift (also, keep in mind that part of that lift effect is not actually lift, but the fact that you're very close to orbital velocities). At that speed, you only need to make about 1/10 the craft's weight in lift to keep it in the air.

@HogDriver: Aware of that, it is fixed in my build and should be fixed in the next release.

[KerbMav]

From Taverio's patch notes (snipped):

v1.5.1

Fix for stock engine nacelle doing 3x as much drag as it should for its intake size.

Update small engine nacelle using new base area values.

New wing data based on 3 decimal point precision measurements of mesh vertexes.

FAR already has these measurements, FAR data for stock wings removed.

Override FAR's thrust levels for jets, if present.

Redo Novapunch winglet rebalance as a ModuleManager file, with new vertex-based measurements of the wings.

Is the drag value of the nacelles only an issue if not using FAR or do we need some more MM cfg data here?

What's up/wrong with FAR's thrust levels?

[XNerd_Bomber]

I've tried using this with the realistic planet size mod, and my rockets keep flipping out of control when I try doing a gravity turn. What am I doing wrong?

[SFJackBauer]

I've tried using this with the realistic planet size mod, and my rockets keep flipping out of control when I try doing a gravity turn. What am I doing wrong?

As with most rocketry-related questions, the answer is "it depends".

Posting a pic of the rocket can help, as well as the gravity turn parameters.

[Surefoot]

Many possible reasons, bottom heavy, too much AoA, wrong aerodynamics...

[NathanKell]

Likeliest remains that you're starting your turn too late (if you're going faster than 100m/s, it's too late) and turning too sharply. Stay within 2-5degrees of your surface-prograde marker.

[Surefoot]

Just sent a bunch of cargoes to Jool and some smaller ships. Aerobraking with FAR is very stressful, especially when you have 9 ships coming. The results are nigh unpredictable, my nuke haulers with just cylindrical fuel tanks attached in line have so good aerodynamics that they lose like 10m/s and go back to escape, even with a 110km flyby... On the other hand my huge supertanker which has airbrakes has to go precisely into a keyhole to get a Laythe transfer. Really tricky Spent 5 hours just trying various aerobraking scenarios (facing retrograde with my haulers to get some drag !). Jool atmosphere model with FAR is very, very different from stock.

[LoSboccacc]

help! why would this craft,

which is quite symmetrical,

would want to steer left so badly?

craft file here

https://www.dropbox.com/s/25gd7v50le4gtjj/K5%20Cloud.craft

[jpinard]

@KerbMav: FAR makes a tank more aerodynamic when it has a nosecone by adding extra drag to unused attach nodes when there is no part attached there.

Also, congratulations on building a lifting body; at ~2km/s pretty much anything will make significant lift (also, keep in mind that part of that lift effect is not actually lift, but the fact that you're very close to orbital velocities). At that speed, you only need to make about 1/10 the craft's weight in lift to keep it in the air.

@HogDriver: Aware of that, it is fixed in my build and should be fixed in the next release.

Hi Ferram - I LOVE this mod! When do you think the next release will go up? My niece is coming over Thursday and I'd love to have your new version when I introduce her to "real airplane physics". She got her first taste of "Default" kerbal Halloween when they came over trick or treating and loved it (she got the hang of it really fast too). Setting her loose with jet design and watching the calamity will be super

[ferram4]

@KerbMav: The drag value of the nacelles is an issue whether FAR is installed or not; FAR doesn't change the stock intake behavior, and that's the source of the error.

The reason Taverius' pack overrides FAR's jet thrust values is because my values are a modification of the stock behavior so that it is slightly realistic, but can still be used for the same purposes, but his values are more grounded in real-life jet performance.

@XNerd_Bomber: Possible reasons:

1. Your "gravity turn" is not an actual gravity turn but is instead an overly aggressive pitch-over maneuver that causes the rocket to move out of it's stable regime.
   
2. Your rocket has a very light, but large payload at the top; this makes the rocket less stable.
   
3. Your rocket's fuel drains in such a way that it becomes less stable as fuel is drained.
   
4. You need more fins at the back of your rocket.
   
5. Your rocket is not designed to be an aerodynamic shape, but instead is designed with traditional Kerbal engineering in mind, which ignores aerodynamics in favor of dV and TWR. Take inspiration from real-life crafts.

A picture would really be quite helpful.

@LoSboccacc: You probably need more struts to keep it from flexing. That is probably the cause of the issue.

@jpinard: I have no idea; probably whenever I finally get the lift of reentering capsules right. Odds are airplane physics will not largely be affected by any changes, so don't worry too much.

[LoSboccacc]

Struts fixed it, in the end I also removed the angled wing tips.

Thanks!

[KerbMav]

nvm.......

Edited November 6, 2013 by KerbMav

[Nemoricus]

It doesn't look like this has been brought up in here before, but does anyone have any idea what's going on in Scott Manley's video here? http://youtu.be/3_oMwlTDuiA?t=7m51s

The spacecraft is falling at a very weird angle, and it seems like it has something to do with FAR...

[ferram4]

That would be a relatively light vehicle (remember, it is empty) producing quite a bit of body lift due to its angle of attack. Yes, things other than wings can produce lift.

[a1270]

@ferram4 I'd like to say thankyou for your work, it has made the game more enjoyable for me.

I am currently trying to get data from FAR to calculate terminal velocity. Going through ARControlSys.ActiveControlSys i can get drag coefficient(Cd) but unfortunately projected area seems missing. Am i missing something? Thanks for your time.

[BrickedKeyboard]

Hey, I could use some help here. I've got the following parts available : Mk1 cockpit, basic jet engine, jet fuel fuselage, structural fuselage, tail fin, AV-T1 winglet, small control surface, swept wings, small gear bay.

I'm trying to make a flyable airplane. Here's a screenshot of the "plane shaped object" I tried making.

It isn't flyable. When it gets to the end of the runway it gets "picked up" and flung out of control.

I'm not sure if it's my plane design, or this mod. Can someone here come up with a readily flyable plane using these parts?

Edit : I got it to fly-ish by giving it a lot more cowbell and using a rocket to get it moving.

[AbeS]

I'd bet it wouldn't fly nicely in stock ksp either, check out this great tutorial: http://bit.ly/1914SpM

[Camacha]

Does FAR account for wing sweep? I am unable to test, but curious.

[BrickedKeyboard]

Ok, I made a few slight tweaks. Yes, I saw that tutorial. What it didn't mention was you need canards or you need to go home. With just these tiny tweaks, it went from being a crash magnet to a perfectly flyable and stable aircraft.

https://www.dropbox.com/s/4ug9eex9roto2eq/flyablebrick.png

I don't suppose someone has a better design using the same part limitations...

Where's a tutorial on what all this aerodynamic data actually means for FAR?! I'd love to be able to make a better design.

Edited November 7, 2013 by BrickedKeyboard

[Hodo]

Ok, I made a few slight tweaks. Yes, I saw that tutorial. What it didn't mention was you need canards or you need to go home. With just these tiny tweaks, it went from being a crash magnet to a perfectly flyable and stable aircraft.

https://www.dropbox.com/s/4ug9eex9roto2eq/flyablebrick.png

I don't suppose someone has a better design using the same part limitations...

Where's a tutorial on what all this aerodynamic data actually means for FAR?! I'd love to be able to make a better design.

Simple answer is, there is no tutorial on FAR.

But the easiest thing to remember in FAR is place the Center of Lift (CoL) just behind the Center of Mass (CoM). This will keep your craft from pitching up and flipping out of control. If you place the CoL to far back the craft will be nose heavy and want to dive every chance it gets. If you place the CoL directly on the CoM, the plane will be "twitchy" but flyable till the CoM changes due to tanks emptying.

The FAR plugin comes with the "Help" option, just click on it and read the long technical discriptions. Trust me I don't even understand 3/4 of it but I can get a stock designed plane to break mach 6 in FAR, so you don't need to understand EVERYTHING, it would help but if you understand a 1/4 of it you will do fine.

[ferram4]

@a1270: That would be because the projected area is marked "private" in the current version. I've switched over to a public projected area instead (labelled "S") in my version to fix that. Should be in the next version.

@BrickedKeyboard: You would need to put the center of lift right on the center of mass to make that work without control surfaces; that would allow the small gimbal range of the jet engines to control the vehicle. Keep in mind that it probably won't be flyable at supersonic speeds though.

Other than that, you need to shift your main gear forward or it's not going to pitch up and take off on the runway. The original complaint of flipping up like crazy as soon as it takes off sounds like it's unstable, which means you need to move the center of lift further back.

The best FAR tutorial is to look up aerodynamic theory in real life; where do you think all these principles come from?

@Camacha: Yup, wing sweep is accounted for.

[Camacha]

What it didn't mention was you need canards or you need to go home.

You do not need canards. Canards are often a sign of a badly designed aircraft. Just make sure the CoM en CoL are in the right order and you should be fine. Get them the wrong way around and you will not be flying today. Not for long, at least.

Mind you, that is not taking into account limited parts.

[BrickedKeyboard]

You do not need canards. Canards are often a sign of a badly designed aircraft. Just make sure the CoM en CoL are in the right order and you should be fine. Get them the wrong way around and you will not be flying today. Not for long, at least.

Mind you, that is not taking into account limited parts.

Well, it doesn't fly without them, so...