Ground Effect Development Thread

[Capital_Asterisk]

Release Thread

This is a very simple mod that increases the lift of a lifting surface at close proximity to ocean, terrain, or buildings. It makes it a little harder to hit the ground. Though far from realistic, it allows ground effect vehicles to function nicely. Drag isn't decreased, but at least it considers wingspan.

All of these are old:

Ekranoplan of course: https://gfycat.com/TenderIllHedgehog
Floatiness over the runway: https://gfycat.com/slowordinaryamericancreamdraft
Test of old version: https://gfycat.com/HoarseFixedGroundbeetle

Requires Module manager
Tested to work on almost all versions above 1.3.1
Github
Releases

First post, I've just been looking around the forums for some help, though you might recognize me from the /r/kerbalspaceprogram discord server. I'm not really sure if I'm doing things properly. Plenty of testing, cleaning, and a few tweaks is needed for this mod to be considered complete. I also have a mod that creates particles on separations, and one that ejects kerbals when the cabin explodes. This was the only mod that seemed successful.

Edited August 16, 2020 by Capital_Asterisk
New version, update features

[Mecripp]

What about over land does dirt popup ? and on your particles on separation have you looked at smokescreen plugin ? and it could did it also and be launches like ice falling off tanks

but on ground FX there is also 

maybe give you something to thing about

Edited September 9, 2018 by Mecripp

[JH4C]

Welcome to the forums, and what a smashing first post! Ekranoplan! Awesome stuff.

If you can get that ejecting-Kerbals mod to trigger their parachutes, you could have another real winner...

[Beale]

9 hours ago, Capital_Asterisk said:

This is great! I wanted this for a wile! Nice job

[Capital_Asterisk]

3 hours ago, Mecripp said:

What about over land does dirt popup ? and on your particles on separation have you looked at smokescreen plugin ? and it could did it also and be launches like ice falling off tanks

...

I'm not sure what you are saying in these sentences, but these are exactly the mods I was looking at just to see if it exists already. I looked into the source code of a few of them to see how particle systems are done, with many complications as the new particle system is undocumented and I have never used Unity before. I took inspiration from a video of a NASA sounding rocket, and the Lunar Ascent Module.

1 hour ago, JH4C said:

If you can get that ejecting-Kerbals mod to trigger their parachutes, you could have another real winner...

That's already added as a tweakable, that reads "Emergency Procedure," which an either be "Deploy Chutes," or "Scream." There's also a tweakable for a random velocity that they eject at, but it's very glitchy. For some reason, the code I use to forcefully EVA the kerbals does not match up with the velocity of the cabin, and they spawn completely still for half a second before moving. It also messes up the save somehow and I have no idea how to fix it. 

44 minutes ago, Beale said:

This is great! I wanted this for a wile! Nice job

You're welcome.

[JH4C]

2 hours ago, Capital_Asterisk said:

That's already added as a tweakable, that reads "Emergency Procedure," which an either be "Deploy Chutes," or "Scream."

 

Oh I really hope you find a way to stop the saves corrupting; that sounds brilliant.

[GearsNSuch]

This certainly looks interesting. I'll have to try it out.

By the way... If it's convenient for you, would it be possible for you to publish your Kerbals-popping-out-of-the-capsule-when-it-explodes mod? I'm willing to try anything that increases my astronauts' chances of surviving.

Edited September 10, 2018 by GearsNSuch

[Mecripp]

I see in a small jet you have to be with in 1m from the water for it to happen and its hard to test over land with out hitting a hill by is there away over land the a dust cloud would show if you got to close to ground and is there away to increase the range just alittle ?

[AdmiralTigerclaw]

Watching and lurking.

 

Ground effect is very important for aircraft behavior, especially helicopters.

[theonegalen]

Oh, this is fantastic, if it can be balanced properly. My KSP computer is not currently functional, but I'd like to ask how the CPU load is.

[Klapaucius]

@Triop

This could make for some interesting race challenges!

[fourfa]

this has got "pod racing" written all over it

[linuxgurugamer]

Definitely keeping an eye on this

[Capital_Asterisk]

On 9/10/2018 at 7:59 PM, Mecripp said:

I see in a small jet you have to be with in 1m from the water for it to happen and its hard to test over land with out hitting a hill by is there away over land the a dust cloud would show if you got to close to ground and is there away to increase the range just alittle ?

It's hard to notice at leveled flight. The mod increases the lifting coefficient, but does not pitch the craft up. Only angled aero surfaces would feel like they're floating, such as landing at high angles of attack. I'm not exactly sure about the aerodynamics of Ekranoplans; but looking at the pictures, the wings are angled up.

On 9/11/2018 at 1:02 PM, AdmiralTigerclaw said:

Watching and lurking.

 

Ground effect is very important for aircraft behavior, especially helicopters.

Yep, I flew a stock helicopter with the mod installed, and it really had a tenancy to repel the ground.

On 9/14/2018 at 1:20 PM, theonegalen said:

Oh, this is fantastic, if it can be balanced properly. My KSP computer is not currently functional, but I'd like to ask how the CPU load is.

My computer is already a toaster so there was no significant drop in framerate. For each frame of an aero surface, distance from the sea is measured, and there is a small raycast towards solid terrain to determine how high the wing is. This is done regardless of there being any solid land or not, so there's plenty of optimizing to do.  So in theory, the load should be proportional to the number of wings.

[AdmiralTigerclaw]

Hey, a good measure for the effect of this mod would be with an SR-71 Blackbird.

 

The Bird has a behavioral quirk in ground effect on landing.  It likes to 'float' so much in ground effect that pilots have reported that you have to force the stick forward and push the nose to get it to finally touch down.  When you can get that kind of performance, the ground effect is working very much correctly.

 

 

 

Also, a suggestion for your code, use the radar altitude as a processing gate.  IF RAD-ALT < 50 meters, THEN execute code.  Saves on raycast passes.

 

Also, how's this work against FAR?

[bunjatec]

just a thought, does this have any effect for VTOL aircraft as the lift engines should be assisted by ground effect too.?

 

[Supercheese]

On 9/27/2018 at 10:04 AM, bunjatec said:

just a thought, does this have any effect for VTOL aircraft as the lift engines should be assisted by ground effect too.?

If I had to guess, probably not very much, since this mod just increases the lift generated by aerodynamic surfaces, and I believe said lift is only generated when there is forward velocity. Since VTOL will be mostly devoid of forward velocity, I wouldn't expect to see much effect.

[StevieC]

@AdmiralTigerclaw That thing about the Blackbird, is it anything like the issue that U-2 pilots have with trying to land?

[AdmiralTigerclaw]

6 hours ago, StevieC said:

@AdmiralTigerclaw That thing about the Blackbird, is it anything like the issue that U-2 pilots have with trying to land?

Yes and No.  The issue with the U-2 is that it's a gigantic glider with a jet engine hiding in it.  It's designed so that it has a LOT of lift at a low indicated airspeed, so that it can soar really, really high up in thin air.  When the Dragon Lady is trending towards an empty tank, and really light, it will descend very slowly unless you want to figure out how to get rid of excess speed.  So it just takes a LONG time to come down, and likes to stay flying at really low speeds.   Ground Effects on such a design make it REALLY hard to settle.  It can fly at speeds as low as 70 knots.  For comparison, a Cessna Skyhawk, your typical civil single engine prop you might see fly over your house on a given clear day, takes off around 55 knots, while air liners will take off more around 160 knots. 

 

The SR-71's problem is different in that its induced by its shape in ground effect specifically.  Delta wings are known for getting extra lift in ground effect.  But I think the chines on the Bird also play a part.  When they interact with ground-effect, they get a little more lift themselves, torquing the nose up just a bit.   Where most aircraft have to flare to smooth out the last few dozen feet of descent into a gentle touchdown, the SR-71 flattens out without the flare to the point that the plane won't settle on the ground.  Combined with a small amount of upward push from the chines, the bird likely naturally flares and tries to climb.  A little extra forward stick input corrects for the natural flaring, and cuts the lift the aircraft has, allowing it to settle.   Usually, on landing, the flare is induced by aft stick movement from the pilot.  To not only not need it, but need to reverse it, means a LOT.

However, for all this difficulty, the SR-71's doing its landings at a teeth-clenching 200 knots, not 70 knots. 

[The Amazing Popsicle]

My prayers have been answered. Always wanted a KSP mod that had ground effect. I’m looking forward to build the Caspian sea monster in KSP! 

[Capital_Asterisk]

Well, new release: https://github.com/Capital-Asterisk/KSP_GroundEffect/releases

A few new changes with this new version. Along with some optimizations, control surfaces are now supported properly, and the increase in lift now depends on how aligned the wing is with the ground. This means vertical stabilizers don't get an increase of lift, previously resulting in extreme yaw control during development. This version is compiled for KSP 1.3.1, and is practically ready for an actual release. It just needs more testing with different versions and crafts.

[AdmiralTigerclaw]

On 10/16/2018 at 8:18 PM, Capital_Asterisk said:

Well, new release: https://github.com/Capital-Asterisk/KSP_GroundEffect/releases

A few new changes with this new version. Along with some optimizations, control surfaces are now supported properly, and the increase in lift now depends on how aligned the wing is with the ground. This means vertical stabilizers don't get an increase of lift, previously resulting in extreme yaw control during development. This version is compiled for KSP 1.3.1, and is practically ready for an actual release. It just needs more testing with different versions and crafts.

Have you tested it along side running FAR?  I don't think that was ever clarified.  I run 1.2.2, so I can't help you run that test if it's not at least backwards compatible.

[Pds314]

Hmm.. I'm pretty sure IRL the ground effect reduces LID and applies within one span of the ground (although the math is different and more complex for moving ACVs and rotorcraft).

Nice idea to make a mod that at least does SOMETHING in this regard though.

I know from flying quadrotors that you can hover about have a prop span off the ground with much lower throttle than what's required to hover mid-room.

On 10/1/2018 at 2:34 AM, AdmiralTigerclaw said:

Yes and No.  The issue with the U-2 is that it's a gigantic glider with a jet engine hiding in it.  It's designed so that it has a LOT of lift at a low indicated airspeed, so that it can soar really, really high up in thin air.  When the Dragon Lady is trending towards an empty tank, and really light, it will descend very slowly unless you want to figure out how to get rid of excess speed.  So it just takes a LONG time to come down, and likes to stay flying at really low speeds.   Ground Effects on such a design make it REALLY hard to settle.  It can fly at speeds as low as 70 knots.  For comparison, a Cessna Skyhawk, your typical civil single engine prop you might see fly over your house on a given clear day, takes off around 55 knots, while air liners will take off more around 160 knots. 

 

The SR-71's problem is different in that its induced by its shape in ground effect specifically.  Delta wings are known for getting extra lift in ground effect.  But I think the chines on the Bird also play a part.  When they interact with ground-effect, they get a little more lift themselves, torquing the nose up just a bit.   Where most aircraft have to flare to smooth out the last few dozen feet of descent into a gentle touchdown, the SR-71 flattens out without the flare to the point that the plane won't settle on the ground.  Combined with a small amount of upward push from the chines, the bird likely naturally flares and tries to climb.  A little extra forward stick input corrects for the natural flaring, and cuts the lift the aircraft has, allowing it to settle.   Usually, on landing, the flare is induced by aft stick movement from the pilot.  To not only not need it, but need to reverse it, means a LOT.

However, for all this difficulty, the SR-71's doing its landings at a teeth-clenching 200 knots, not 70 knots. 

200 knots? Wow. That's faster than a Tu-22, the Concorde, the F-104, a packed 737-900 landing on a hot day in Vegas, the Buran, and the Shuttle.

(yes, this list is in order. Landing a 737 at 166-175 knots is something that is done and it's weird landing at a speed some planes cannot even reach. I swear in the future airliners will be landing at cruise speed).

Edited October 23, 2018 by Pds314

[Capital_Asterisk]

2 hours ago, AdmiralTigerclaw said:

Have you tested it along side running FAR?  I don't think that was ever clarified.  I run 1.2.2, so I can't help you run that test if it's not at least backwards compatible.

It shouldn't work with FAR at all, it uses its own values and ignores the stock aerodynamic values during flight. I'll add FAR compatibility before the official release.

[AdmiralTigerclaw]

1 hour ago, Pds314 said:

Hmm.. I'm pretty sure IRL the ground effect reduces LID and applies within one span of the ground (although the math is different and more complex for moving ACVs and rotorcraft).

Nice idea to make a mod that at least does SOMETHING in this regard though.

I know from flying quadrotors that you can hover about have a prop span off the ground with much lower throttle than what's required to hover mid-room.

200 knots? Wow. That's faster than a Tu-22, the Concorde, the F-104, a packed 737-900 landing on a hot day in Vegas, the Buran, and the Shuttle.

(yes, this list is in order. Landing a 737 at 166-175 knots is something that is done and it's weird landing at a speed some planes cannot even reach. I swear in the future airliners will be landing at cruise speed).

 

There's a reason the Bird needs a drag chute on touchdown.  It does NOT like being slow.