Variable Incidence wing - possible?

[AeroGav]

https://en.wikipedia.org/wiki/Vought_F-8_Crusader

If you want my reasons, there's a detailed explanation here - 

 

The short version is that in stock aero most drag comes off the fuselage, even if the wings are angled to produce lift with the body of the plane pointing directly into the prograde.   Push the nose up or down only a degree or two however, and it can  up doubling.

This is a problem because some phases of flight require more lift than others.    If you prefer to penetrate sound barrier at sea level,  you need a low lift condition, so it doesn't try to climb when going fast in thick air.   If you are trying to do that at altitude to take advantage of the thinner air, you need quite a bit of lift.

During the speedrun, you are probably trying to get mach 5.2 at 21km air breathing.    Due to extreme high speeds, low lift is fine.    But if you use NERV engines to get from there to orbit,   you need high lift and good lift drag ratio because the air is so thin.    

Without variable incidence you can pitch up or down, but that leads to large amounts of drag.

So, is there a way to make a variable incidence wing

a) stock

or 

b) using infernal robotics

Imagine b) is a lot easier and more controllable, though if i could get a) to work with two presets (3 degrees and 7 degrees perhaps)  it'd make my day.  month. year.

[diomedea]

In stock you can get a similar behaviour of a variable incidence wing using a large control surface part, setting it to inactive for pitch, roll and yaw control, and setting a limited authority when it deploys. Then, have one custom action control its deployment, so it changes inclination as you like. Tested with a medium-sized SSTO with FAT-455 Tail Fins as main wings, worked perfectly.

Theoretically any of the stock wings can be modified in a variable incidence wing (so, would work with larger planes). But while changing a wing config to include a moduleControlSurface as appropriate (instead of the moduleLiftingSurface those parts have) is pretty easy (and the wing still works, tested), to have it really work requires to compute the dragcubes for its deployed states, and add them to its cubes definitions in PartsDatabase.cfg. Believe some routine with modelling programs allow to easily determine a cube values, but those are beyond my current knowledge.

[fourfa]

Maybe prototype the gameplay by tweakscaling up some of the all-moving control surfaces? Standard Canard, Tail Fin, R8 seem like good candidates.  Then as above, use Deploy with small control limits.  

Edited December 3, 2016 by fourfa

[foamyesque]

This is why flaps were invented

[fourfa]

Is it? I've never tried using flap deploy (limited to small ~5 degree amounts) to simulate wing incidence.  Seems like deployed flaps in KSP act more like drag than lift?  Is that just because the stock deploy limits are too high?

BTW flying a tiny toy plane with un-tweakscaled stock tailfins as wings, changing deploy limits in flight - really interesting! I think @AeroGav can get what he wants in semi-stock

Edited December 5, 2016 by fourfa

[AeroGav]

What I'm planning to do is use something like a big S elevon or a canard as a hinge on which to attach the main wing, thanks to auto strut it should be rigid enough.

Flaps in the stock game and FAR are basically useless imho, because in real life they work by  changing airflow over the whole wing, not just on the part that deflects up or down.  In game, the only extra lift and drag you get is from the flap part itself being at higher angle of attach.  Also they deploy to 30 degrees by default , which means if the aircraft itself has any AoA at all or the wing any incidence, the flap surface becomes stalled and acts more as an airbrake than as additional lift. 

[foamyesque]

Things attached to control surfaces don't move even if the control surface does, last I checked?

S'far as flaps go, what they deploy to depends on what control surface you're using and what it's authority-limited to. I not-infrequently use Big S elevons mounted to the underside of a wing and authority-limited to a fairly small range; yes, they cause a drag increase, but that's inevitable, and they do give you a lift boost. I generally use them for landing and, to a lesser extent, takeoff, since those are the areas where getting the absolute maximum amount of lift possible without boosting your plane's overall AoA is most useful. Never felt the need at hypersonic, since I'm generally riding my prograde marker at a 5-to-10 degree slope (depending on TWR) straight into space.

[Val]

Real life flaps also create a lot of drag. Enough, that I'm not in doubt when an airliner deploys flaps, even if I'm not sitting at a window to see it.

The difference between KSP flaps and RL doesn't seem that big to me.

 

[AeroGav]

6 hours ago, foamyesque said:

Things attached to control surfaces don't move even if the control surface does, last I checked?

correct, sigh.  so no stock hyper efficient ssto then, it will have to be robotics.

Building a wing out of elevons is ridiculous, they weigh twice as much as normal wings for the same lift rating and they don't hold any fuel, that would counter gains.      

[Val]

4 hours ago, AeroGav said:

Building a wing out of elevons is ridiculous.

I wouldn't go as far as calling it ridiculous, but definitively challenging. I got this craft to orbit with an Orange tank as payload.

Takeoff weight was 138 t. Large elevon 2+1 as "main" wing. Deploying 45 and 30% respectively. Large elevon 1 as flaps deploying to 65%. Elevon 2 as aileron. 5° base AoI.

Here's a 15 minute video of it going to orbit and coming back to KSC again. (But failing to land properly ) Video link (unnarrated, but I do point with the mouse occasionally)

I should have made the runway approach shallower and with engine power to counteract the drag from high AoA wings and flaps.

Still the landing speed would have been quite high.

 

[AeroGav]

1 hour ago, Val said:

I wouldn't go as far as calling it ridiculous, but definitively challenging. I got this craft to orbit with an Orange tank as payload.

Takeoff weight was 138 t. Large elevon 2+1 as "main" wing. Deploying 45 and 30% respectively. Large elevon 1 as flaps deploying to 65%. Elevon 2 as aileron. 5° base AoI.

Here's a 15 minute video of it going to orbit and coming back to KSC again. (But failing to land properly ) Video link (unnarrated, but I do point with the mouse occasionally)

I should have made the runway approach shallower and with engine power to counteract the drag from high AoA wings and flaps.

Still the landing speed would have been quite high.

 

Nice job ! I'd say you need to use more elevons though, at smaller deflection angles if better lift drag ratio is the goal ! I'm getting 3.5 to 4.5 to 1 supersonic/hypersonic on my conventional designs, so  unless variable incidence can improve on that it's not worth it .   Then again, with the low wing loadings i like to spam,  swapping big s wings for elevons would  be costly in terms of extra mass and lost fuel capacity.

+points for the crash landing ! love it !

[foamyesque]

1 hour ago, Val said:

I wouldn't go as far as calling it ridiculous, but definitively challenging. I got this craft to orbit with an Orange tank as payload.

Takeoff weight was 138 t. Large elevon 2+1 as "main" wing. Deploying 45 and 30% respectively. Large elevon 1 as flaps deploying to 65%. Elevon 2 as aileron. 5° base AoI.

Here's a 15 minute video of it going to orbit and coming back to KSC again. (But failing to land properly ) Video link (unnarrated, but I do point with the mouse occasionally)

I should have made the runway approach shallower and with engine power to counteract the drag from high AoA wings and flaps.

Still the landing speed would have been quite high.

 

 

That's pretty cool, but what was your return weight? That's an awful small amount of wing area for something that big.

[Val]

29 minutes ago, foamyesque said:

That's pretty cool, but what was your return weight? That's an awful small amount of wing area for something that big.

Return weight was around 60 t.

[foamyesque]

30 minutes ago, Val said:

Return weight was around 60 t.

Yeaaaah, that's way less wing than I'd feel comfortable with on that mass for landing. I usually design to a 1 wing area: 5 tonnes ratio for landing purposes. Not surprised you say you pancaked in on a glide :v

Edited December 5, 2016 by foamyesque

[Val]

2 minutes ago, foamyesque said:

Yeaaaah, that's way less wing than I'd feel comfortable with for landing. I usually design to a 1 wing area: 5 tonnes ratio for landing purposes. Not surprised you say you pancaked in on a glide :v

It wasn't that bad. I just wasn't paying attention to how fast my speed was dropping. Had I kept speed above 100 m/s until I reached the runway, I would have been fine. The last few seconds.