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

[sober667]

Did you do this?

If so, I love you.

http://i.imgur.com/D0ItcU7.jpg?1

oh... didnt noticed that its nice to have some fancy warnings

[DaMichel]

I think you misunderstood me, the only original issue I had was that planes tend to glide way more than its expected, with power off its very hard to lose speed. As Mipe mentioned, I might be thrown off by the KSP ratio, where as there seemed to be a lot of wing for the plane, but the KSP parts are incomparably too heavy for them. I wasn't complaining for not getting enough lift at all, its quite the opposite, I'm complaining is quite hard to get the plane to slow down instead... Now given, propeller planes suffer indeed from heavy drag when tuned down, but mostly sure all planes will almost immediately lose speed and altitude when powered off. The level demonstrations were more to show just how long it took to lose speed without loosing altitude, the minimum speed in the last one were just for the fun of it.

You could try to find data on a planes lift/drag ratio which happens to equal the glide ratio (distance traveled forward divided by altitude lost). https://en.wikipedia.org/wiki/Lift-to-drag_ratio

Compare that to L/D from FAR flight data. Because this is essentially what you are complaining about.

But lets see. There is pic during the approach where you have vertical velocity of -10 m/s and an airspeed speed of 90 m/s which gives an L/D of approximately 9. Not too bad.

There are plenty of reference L/D on the wiki page, and 9 seems to fit really well. Example:

Gimli Glider (Boeing 767-200 with fuel exhaustion) ~12

Concorde (Approach) 4.35

Given that the Concorde lands at high AoA this makes sense, too.

Edited May 11, 2015 by DaMichel

[Wanderfound]

Dangit; just had another hard computer crash following an aero failure.

[UristMcKerbin]

I've heard when 1.0.2 released it had a lot of broken aerodynamics. Does I need to seek for config fixes with FAR enabled. I've installed FAR and 1.0.2 and now not only can launch not flipping rocket, but can't even deploy chutes - they are cut at 38km at 2km/s speed due to 'aerodynamic forces or over-heating'. I'm FAR veteran and get used to flipping rockets but they are overflipping now.

EDIT: also with FAR chutes start deploying far more earlier - I've set them to 0.01 atm and they deploy at 50km. How they found 0.01 atm at 50km is the mystery of mysteries. EDIT for EDIT: they somehow manage to be cut at 50km due to forces (no acceleration applied). Even umbrella is better.

Edited May 11, 2015 by UristMcKerbin

[Wanderfound]

I think you misunderstood me, the only original issue I had was that planes tend to glide way more than its expected, with power off its very hard to lose speed.

It really isn't.

...and that's without even using any S-turns or other such trickery; just throttled-off drag.

Sure, it'll take longer to slow if you're flying some 100 ton behemoth, but in that case you should be using a 747-style glideslope, not trying for a dive and flare landing.

[linuxgurugamer]

@Krakenfour: Do an AoA sweep at the Mach number you're interested in. If the yellow line slopes down, you're stable. If it slopes up, you're unstable. If it's flat, you're neutrally stable (which is, for our purposes, the same as unstable). If it changes slope as AoA changes, that means at some AoAs you're stable, and at others you're unstable.

@linuxgurugamer: That sounds really screwy, like something isn't saving. First thing I'd suspect is user error, tbh, the second thing I'd suspect is CKAN doing something screwy, because it's done a lot of that recently.

Also, any CKAN issues aren't my problem, I'm not even happy with my stuff there given the issues it's been causing.

OK, I'll try reinstalling FAR by hand and see if that fixes the problem.

LGG

[CrisK]

I've heard when 1.0.2 released it had a lot of broken aerodynamics. Does I need to seek for config fixes with FAR enabled. I've installed FAR and 1.0.2 and now not only can launch not flipping rocket, but can't even deploy chutes - they are cut at 38km at 2km/s speed due to 'aerodynamic forces or over-heating'. I'm FAR veteran and get used to flipping rockets but they are overflipping now.

EDIT: also with FAR chutes start deploying far more earlier - I've set them to 0.01 atm and they deploy at 50km. How they found 0.01 atm at 50km is the mystery of mysteries. EDIT for EDIT: they somehow manage to be cut at 50km due to forces (no acceleration applied). Even umbrella is better.

2km/s is far too fast for a parachute. Ideally you should wait until you're under 400m/s. If you're moving that fast, you're not performing a proper reentry.

38km is incredibly high up for a parachute. Parachutes should be used at 10km at the highest, and ideally you would wait until you're at 3km.

[linuxgurugamer]

@Obsessed: Aye, that's me. Even changes significance between VAB and SPH; it's a warning in the VAB (because normally, it just calls for more boosters there) and a critical issue in the SPH (because it tends to limit you to M < 1).

@amankd: It's figuring out, "is this entire section of the vehicle a wing?" for the purposes of it. Not a simple task. Once that's taken care of though, it should be relatively straightforward to get ground effect in. It's just a multiplier to lift and drag, tbh.

Ferram,

Regarding ground effect here is a suggestion. I base it on experience; I build and fly radio control airplanes.

First, assume that ground effect doesn't exist if you are higher than the wingspan of the airplane.

Second, assume that at altitude 0, it increases lift by a certain percentage (25% is reasonable). Then simply have that percentage decrease as you get higher, until you are at the altitude which is equal to or greater than the wingspan of the airplane.

You could even make the percentage as a relation to the width of the wing compared to the wingspan

This isn't perfect, but if you make the percentage configurable, it should be good enough.

Edited May 11, 2015 by linuxgurugamer

[ratchet freak]

you can look for a flat area on the bottom of the plane.

Then take that area as the wing for ground effect. This way the entire bottom of a low-winged spaceshuttle will be the ground-effect wing but the "keel" sticking out in a high-wing Cessna isn't part of it (just the actual wings and elevators).

[linuxgurugamer]

Ferram,

I did a new install, and only installed FAR and Kerbal Engineer.

I figured out my problem, and will detail it here in case anyone else has the same issue.

I _thought_ I had disabled the rudder from responding to pitch and roll, What I had really done was to set those number from 100 to -100, I didn't realize that 0 was in the center.

I had the same problem on the canard.

I had posted my original post because I wasn't sure it was a bug or not. Turns out it was not a bug, just a bad config. Hopefully this post will help others who may have the same problem.

And I know you don't like CKAN, so I'm not going to argue with you on that :-)

Just would like to say that CKAN did do a good install with the current settings.

LGG

The plane flies so much better now that the controls aren't fighting each other :-)

Edited May 11, 2015 by linuxgurugamer

[Wanderfound]

Under NuFAR, I'm finding it easy to extract extreme speed from sleek, single fuselage ships, but very very difficult (good!) to get anything multi-fuselage (AKA "hot dog") up to speed. I'd be interested in seeing if anyone's managed to get a larger ship working yet.

[balu0]

Still the best add on for KSP so far (see what I did there ? so far )

Lil things that concerns me:

Subsonic drag seems like too low for me, I can glide with a brick like a soar plane. From 0.8 mach to 0.2 it takes minutes to slow down without using air breaks. But when i add some spoilers with a high

deflection say 60 - 80 deg. then no matter how small they are they slow me down like a concert wall.

Edited May 11, 2015 by balu0

[Goddess Bhavani]

I expected nuFAR to totally break my favorite 1930 Soviet aircraft, which had the aerodynamics of an NYC subway car. But lo and behold the voxel aero actually granted it a spectacular drag reduction vs. stock and I just needed a bit of additional wing area since it's 10 tons overweight from historical specs!

But fly and fly well it did and it's both hilarious and amazing to try and closely replicate the historical top speed of 300kph for this 1936 variant of the TB-3.

Javascript is disabled. View full album

For anyone adventurous enough to try it, and have TweakScale, KAX and Infernal Robotics installed, you may get the craft file from here:

http://kerbalx.com/crafts/2287

It doesn't have any handling vices and is ridiculously easy to fly but do not exceed 300+ kph / 83m/s or else there will be insufficient pitch authority to control the aircraft (game balancing mechanism by yours truly )

[taniwha]

Still the best add on for KSP so far (see what I did there ? so far )

Lil things that concerns me:

Subsonic drag seems like too low for me, I can glide with a brick like a soar plane. From 0.8 mach to 0.2 it takes minutes to slow down without using air breaks. But when i add some spoilers with a high

deflection say 60 - 80 deg. then no matter how small they are they slow me down like a concert wall.

If you are flying on any sort of downslope, then it is perfectly normal to take a long time to slow. With sufficient downslope, you will be able maintain speed or even speed up (to a point, of course). Also, minutes is hardly a long time.

I suggest a visit to your local airport to watch a few planes land. Note how they come in low and slow (and that 50m/s is 180km/h) and consider that they have been slowing for some time. And next time you're on a plane, get a window seat over the wing and watch the flaps and spoilers. The spoilers don't come on "hard" until the plane is on the ground.

Subsonic drag is not too low for you. Your expectations of subsonic drag are too high. Remember that planes are designed to have high lift and low drag.

[jrandom]

Can confirm with my "flight experience" in X-Plane 10 that planes don't slow down very well. Even large airliner passenger jets are tricky to land without careful speed reduction to just above stalling + flaps, timing it just right so you've slowed down enough to stop when you finally reach the runway.

In KSP the problem is even worse because it's so easy to load up your plane with a zillion gallons of fuel. All that inertia contained in something streamlined enough for flight makes it difficult to slow down quickly.

[Hektos]

Does FAR tweak jet engine thrust value anymore? If it does, where can I find the .cfg that does this?

[Wanderfound]

Does FAR tweak jet engine thrust value anymore?

Nope. If you want to melt your cockpit with hypersonic low-altitude nuttery, you are now free to do so.

[tetryds]

Yep, also, on KSP parts tend to be supersmall and superdense, which helps with piercing the atmosphere preventing things from slowing down (check Mk3 cockpit, that thing has a blackhole on it).

@Hektos:

No it doesn't tweak engines anymore, the only thing it does is boost gimbal of all engines by 1.5x, because sanity.

[Hektos]

Nope. If you want to melt your cockpit with hypersonic low-altitude nuttery, you are now free to do so.

Awwwww yeah

I only ask because I can't seem to get the basic jet engine past ~320 m/s and was curious if was a design flaw in my plane or just an engine limitation.

[tetryds]

Awwwww yeah

I only ask because I can't seem to get the basic jet engine past ~320 m/s and was curious if was a design flaw in my plane or just an engine limitation.

Check a few pages back for transonic area ruling tips and explanations, that is the reason you cannot go past it (in a nutshell, it's the design)

Edit: Does not mean you can't do it with some boosters, by the way

Edited May 11, 2015 by tetryds

[Gfurst]

It really isn't.

http://i.imgur.com/21OtKLu.jpg

...and that's without even using any S-turns or other such trickery; just throttled-off drag.

Sure, it'll take longer to slow if you're flying some 100 ton behemoth, but in that case you should be using a 747-style glideslope, not trying for a dive and flare landing.

You just demonstrated another one of my points, look how low you came to the runway, you're technically level with it way before touch down....

If you are flying on any sort of downslope, then it is perfectly normal to take a long time to slow. With sufficient downslope, you will be able maintain speed or even speed up (to a point, of course). Also, minutes is hardly a long time.

I suggest a visit to your local airport to watch a few planes land. Note how they come in low and slow (and that 50m/s is 180km/h) and consider that they have been slowing for some time. And next time you're on a plane, get a window seat over the wing and watch the flaps and spoilers. The spoilers don't come on "hard" until the plane is on the ground.

Subsonic drag is not too low for you. Your expectations of subsonic drag are too high. Remember that planes are designed to have high lift and low drag.

If you're flying the downslope... yeah that's perfectly normal to maintain speed, one thing you're forgetting.... all airplanes in your airport are coming for a much steeper glide-scope, still holding up on that throttle until the last second, if you throttle off you immediately go into glide attitude or quickly lose speed being level. What I've demonstrated was being level (aka not loosing height) and taking a long time to lose off speed. And as mentioned, KSP is denser than anything, so we need to account for what looks reasonable in real life is fact very different in KSP.

As a side question, does tweak scale works properly with FAR now? Even wings can have their property scale up/down? Might make building the plane better.

[kcs123]

http://i.imgur.com/tEGjmHk.jpg

Under NuFAR, I'm finding it easy to extract extreme speed from sleek, single fuselage ships, but very very difficult (good!) to get anything multi-fuselage (AKA "hot dog") up to speed. I'd be interested in seeing if anyone's managed to get a larger ship working yet.

Yep. My Old Space Plane Mk2 V8 kicks again. Although I need some more balancing it due to various bugs encountered from various mods. Also I'm forced to use different parts since some mods are not updated yet. Anyway, 60t plane, wide shape, but can easy get above 4.5 mach. I need to optimize CoM and thrust, so it does not flip over in space, but when comes to reaching optimal speed, it is even easier than before.

WIP craft version is available from links in signature for anyone curious. I hope that I will be able to optimize it more with working stability derivatives.

[6.forty]

Found a bug with the UI caused by B9 procedural wings, setting the wing tip width to 0.0 causes the cross section graph display to disappear, wave drag displays NaN, and calculating stability derivatives results in the UI doing this:

Here's a Player.log of it happening with only FAR and B9 wings present.

[Hektos]

Check a few pages back for transonic area ruling tips and explanations, that is the reason you cannot go past it (in a nutshell, it's the design)

Edit: Does not mean you can't do it with some boosters, by the way

Found it thanks!

I sort of understand what I need to do, but now the only problem I'm getting is that when I place wings on the plane the CoL actually goes FORWARD making it impossible to get it behind the CoM

EDIT: For anyone else looking for the post, HERE IT IS.

[Hodo]

It really isn't.

http://i.imgur.com/X5qRqaP.jpg

http://i.imgur.com/21OtKLu.jpg

http://i.imgur.com/vvOKFCb.jpg

...and that's without even using any S-turns or other such trickery; just throttled-off drag.

Sure, it'll take longer to slow if you're flying some 100 ton behemoth, but in that case you should be using a 747-style glideslope, not trying for a dive and flare landing.

You are also landing at a REALLY high speed for most aircraft, 125m/s is FAST.

A F-16 lands around 80m/s fully loaded.