Need a simple explanation on wings effects

[Kar]

Hi all.

Can someone explain to me in simple terms (I am not technical enough for high math stuff but I do understand simple physics concepts) the effects of angles in wings in a aircraft. Consider this to apply to KSP and not to real life since the physics on KSP are different.

So, usually wings on a aircraft are at 90º perpendicular to the center body of the aircraft, something like this -----O----- .

What are the effects of lower the angle a few degrees for example, lower the angle near the ground (best example I can think of is the X-302 mentioned in Stargate SG1).

Also, whats the effect if it's the opposite?

Is there any advantages using different angles or not really?

Hope I am making myself clear.

Thank you.

Edited March 14, 2015 by Kar

[Empiro]

In stock KSP aerodynamics, not very much, I believe.

If you're using FAR, then it has a much larger effect. An anhedral angle (wings pointing toward the ground) increases maneuverability while making your craft less table. A dihedral (upwards) angle improves stability.

For spaceplanes, I usually use a dihedral tilt at the wingtips when I'm playing in FAR. It significantly improves stability at very high altitudes and speeds.

This wikipedia page explains things in more detail: http://en.wikipedia.org/wiki/Dihedral_(aeronautics)

[Kar]

Thank you very much. I do not use FAR, I already have too much work in my career game with many of the mods I use. I will test the wings angle and see how it goes in a "stock" aerodynamics way.

[Deutherius]

In stock KSP aerodynamics, not very much, I believe.

I believe it does. I think the wings produce different amount of lift under different angles. Increasing the angle on a wing (say, dihedral design, port side wing, aircraft rolling to starboard) will decrease its lift generated. The other wing (now more parallel to the ground) will produce greater lift, and this differential naturally corrects the roll of the aircraft (up to a point). I could be wrong though.

[Taki117]

For all your KSP aircraft building needs.

[GoSlash27]

In stock KSP, it will add a natural tendency to roll wings level if they're tilted up. If tilted down, they will create a roll instability, increasing maneuverability. Other than that, it reduces the overall lift.

Best,

-Slashy

[NathanKell]

Ah, my understanding was that they would merely produce less lift in stock KSP; I thought that lift was always *applied* straight up and down in stock KSP.

Btw this isn't angle of attack; angle of attack is the angle between the *oncoming* wind and the forward edge of the wing (when the little velocity pip is below the center caret on the navball, you have positive AoA).

[GoSlash27]

Ah, my understanding was that they would merely produce less lift in stock KSP; I thought that lift was always *applied* straight up and down in stock KSP.

NathanKell,

It is actually vectored and you will get dihedral effects, but only if the inclined panels are outboard to give them leverage. All lift and drag are generated at the attachment point, so if you have (for example) a parasol wing with anhedral you won't notice any effect beyond the loss of lift.

Bonus: If you add dihedral to outboard panels and set them behind the center of mass, they will also add yaw stability.

Best,

-Slashy

[Huntn]

I assume the following is true, but would appreciate confirmation. As a space plane designer, this is very important to realize! I watched a Scott Manley Youtube Video on Space planes where he said all of the airfoils in the game are symmetrical and produce no lift at 0° angle of attack (AOA). These are the kinds of airfoils you'd see on a rocket for stability, but not on a plane designed to fly in the atmosphere. Instead they rely on "barn door effect", wind hitting the bottom or top side of the airfoil at something more than 0° AoA to produce some amount of lift. How much I don't know, but is it safe to say from a design standpoint that all/most of the lift being produced is based on thrust from the engine?

The description of a dihedral wing adding to stability means there is some amount of atmospheric physics, but I've always thought the effect had to do with a lifting wing. I just don't know how much. But based on the videos I've watched there appears to be enough barn door lift to glide a plane to a landing. It's just that from a realistic aviation standpoint, flying through the air, I don't think barn door effect cuts it. For most airplanes a lifting wing is required. For KSP, think about this, for all those fancy space planes with fancy cool looking wings, they may serve little purpose except to look cool and add weight.

If this is true (there are no lifting airfoils) I assume it is because KSP physics don't correctly model wing lift as you would see in a traditional flight sim. I realize this game is primarily about space, but being so physics inclined, it's a shame if they can't model a regular wing. After all the Space Shuttle wing produces lift... History of the Space Shuttle.

Edited March 25, 2015 by Huntn
clarified

[Van Disaster]

Would imagine stock just uses straight up vectors, take velocity*air density, use AoA to get the length of the lift vector ( use the part's Z axis for direction ), multiply by lift factor from cfg & there you go. Nearer supersonic lift than subsonic but as you say this was originally about rockets.

FAR does it better, and the coming aero change will probably go most of the way too.

[Huntn]

Would imagine stock just uses straight up vectors, take velocity*air density, use AoA to get the length of the lift vector ( use the part's Z axis for direction ), multiply by lift factor from cfg & there you go. Nearer supersonic lift than subsonic but as you say this was originally about rockets.

FAR does it better, and the coming aero change will probably go most of the way too.

FAR? There is a aero change coming to KSP, as in improved aerodynamics? That would indeed be welcome. From a flight sim standpoint, X-Plane is the best (as far as I know ). Instead of using tables that determine performance, the game actually computes lift and drag based on the shape of the airfoil.

Edited March 25, 2015 by Huntn

[Starhawk]

There is a aero change coming to KSP, as in improved aerodynamics? That would indeed be welcome.

Yes. That is a large change in the upcoming version and heavily anticipated by many in the community. It wall also completely change the flight profiles of rockets as well, forcing all players to relearn how to get to space. We don't even know what the delta-v or TWR requirements will be to achieve orbit.

Happy landings!

[Captain H@dock]

there appears to be enough barn door lift to glide a plane to a landing. It's just that from a realistic aviation standpoint, flying through the air, I don't think barn door effect cuts it.

Well, there clearly seems to be a problem in default stock with flying at very high AOA*. It is way too stable and un-draggy**. This is due to current stock aerodynamic being improperly modeled, which will be improved in 1.0.

* Well, there's definitely is a problem with aero implementation in general, since it's liftCoef*mass or something like that, and wing rotations are poorly handled.

** My SSTO can glide its 10 tons the length of the runway with no trust and barely loose altitude while only shedding half of its 60 m/s final approach speed. And still not stall at 25 m/s with 30/40° AOA... This should be deadly induced drag territory, as far as i understand...

It's as if increasing AOA was only increasing lift but not drag, with the subsequent climb alone slowing you down... KSP aero low speed regimes are counter-intuitive to me...

Edited March 25, 2015 by Captain H@dock
typo + induced drag, not parasitic

[Huntn]

Yes. That is a large change in the upcoming version and heavily anticipated by many in the community. It wall also completely change the flight profiles of rockets as well, forcing all players to relearn how to get to space. We don't even know what the delta-v or TWR requirements will be to achieve orbit.

Happy landings!

Overall I feel very positive about this. I want to think my physics based game is mostly modeled on semi-realistic physics. :) Thank you. I've not thought about it previously, but if you look at the Space Shuttle, relatively small wings, steep glide ratio, but those wings do produce some lift. I assume on launch that the rockets had to counter that lift to some degree to keep it going in the desired direction and/or they used that lift to help point the desired flight path. And with the update, I don't expect but would accept the need for something as large a a Saturn V to get into orbit as long as the principles have some realism associated with it.

Well, there clearly seems to be a problem in default stock with flying at very high AOA*. It is way too stable and un-draggy**. This is due to current stock aerodynamic being improperly modeled, which will be improved in 1.0.

* Well, there's definitely is a problem with aero implementation in general, since it's liftCoef*mass or something like that, and wing rotations are poorly handled.

** My SSTO can glide its 10 tons the length of the runway with no trust and barely loose altitude while only shedding half of its 60 m/s final approach speed. And still not stall at 25 m/s with 30/40° AOA... This should be deadly induced drag territory, as far as i understand...

It's as if increasing AOA was only increasing lift but not drag, with the subsequent climb alone slowing you down... KSP aero low speed regimes are counter-intuitive to me...

Ug.

Would you say that as the game currently stands that it does space physics fairly well? I am no astronaut, but the mechanics of raising and lowering orbit feel right. I've done the transfer orbit in the tutorial and it feels acceptable, the maneuver node adds calculations which makes the game seem more realistic than just eye balling it. This simulation is very ambitious and I want it to feel somewhat realistic. Having to eyeball flying over a waypoint for a contract feels very unreal. Maybe the Kerbals don't have GPS, but they certainly should have some fairly sophisticated instrumentation besides looking out the window. The Waypoint Mod, came to my rescue for Kirbin surveys. Now I have to get up to speed with the scriptable auto-pilot. I don't want to be hand flying, not because I don't like the challenge, but because (my impression) it reminds me of how unrealistic that is. There maybe times when manual adjustments might be made, and in emergencies with equipment degredation, but I believe something along the lines of computers/autopilots is how astronauts really fly, not Kentucky wind-age.

Edited March 25, 2015 by Huntn

[Captain H@dock]

To be fair, this could really change with 1.0 and it still is fun to fly in the medium speed regime. That leaves the "going to space part" which is weird anyway, and the low speed regime which seems too slippery (or maybe my plane designs are bad, but I would expect be able to descend with a low thrust setup and a nose up attitude)

[jarmund]

Despite quite a few claiming that it makes little to no difference in stock, it actually matters a lot. If you sweep the wings backwards, it'll loose a lot of its lift, as the airspeed perpendicular to the wing is what counts. In other words, a wing turned 90 degrees before attaching will generate no lift in stock, while still having all of its drag, despite it'l clearly exposed to the airstream. FAR, however, models this correctly, as stated by others.

Scott Manley

[Huntn]

This is probably more of a rant but please bear with me. I've flown airplanes and flight sims for years but KSP is lousy from a space plane perspective. I realize a physics update is in work. First off I've seen some KSP planes that look fantastic. I've downloaded and they really fly, but I've not tested them extensively.

If I look at the purpose of a space plane, it seems that vertical launch is the most realistic way to go because aircraft are not built as a barrel of rocket fuel with a cockpit, wings, and stability added. That's how rockets are built. However in my endeavor to build a simple space plane that can take off with a horizontal takeoff roll, I make sure that the center of lift and center of mass are close to one another. I can find a configuration that will fly, but not fly well, and then sometimes my aircraft flips end over end while flying, no problem. I'm definitely to scared at this point to install FAR. I have completed several survey missions where you have to fly over an area below a specific altitude. I've equipped my airplane with parachutes so I don't have to worry about crashing at the end of a mission, lol.

Typically I build a fuselage with a delta or straight wing, but most of the time the basic aileron/elevator tabs are not efficient enough for rotating the aircraft. I've adjusted landing gear location to change the AoA of the airplane when it's sitting on the runway I've put a movable canard on the front, and it's not usual for my plane to flip over on it's back. No problem. Someplanes, simply will not rotate on with full backstick, but there's a bump at the end of the runway that seems to give them the little extra they need to become responsive. Anyway I'm frustrated. At the lower science levels, there simply is not enough good airplane parts, which if you use logic, there should be, as in airplanes developed before space flight. For now, I think I should stick to building rockets and just fly downloaded hot rods like the White Lightning.

Edited March 30, 2015 by Huntn

[psychopoak]

hey, you should have a look there :

http://forum.kerbalspaceprogram.com/threads/52080-Basic-Aircraft-Design-Explained-Simply-With-Pictures

this is one of finest tutorial I've come across so far, and it should be seen by anywho pretend to build a plane in ksp