tetryds

Official FAR Craft Repository

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19 hours ago, Drew Kerman said:

Here is the problem in action (all wheels are locked, also tried with the normal trike gear and it was worse, but I hear those gear are really bad in 1.1.3)

 

Turn on angle snap, absolute instead of local, and rotate the landing gear so that it's perfectly vertical and straight.  Angled gear don't work unless they're rigid; the suspension and part-joint flex warps the steering geometry in unpredictable ways.

Edited by Wanderfound

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2 hours ago, Wanderfound said:

Turn on angle snap, absolute instead of local, and rotate the landing gear so that it's perfectly vertical and straight.  Angled gear don't work unless they're rigid; the suspension and part-joint flex warps the steering geometry in unpredictable ways.

yea I did that so I would have the same angle of the aircraft during the ground roll. Anyways, I fixed it:

Spoiler

3a8XML0l.png

Takeoff with 0 control input at 2 flaps! Note I enlarged the tail fin and gave more dihedral to the rear stabilizers to completely remove all red lateral motion numbers in the static analysis up through takeoff speed. I then returned them to normal and took off again without issue.

Turns out it was the nose gear. I thought just the fixed trike gear were messed up but apparently all three are useless in v1.1.3 - can't wait for v1.2 to drop and get full mod support! :P

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Great! I built a lot of light aircraft recently ( er, more accurately I built one aircraft & then made a considerable number of versions of it ) & the easiest to handle on rough ground were all tail-draggers.

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After tail-draggers, the other best chance of success is simple inertia, but making a plane heavy to deal with bad landing gear seems a *really* strange thing to have to do.

Spoiler

30040435672_0a8889407d_b.jpg

 

Edited by Van Disaster

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A mod called NavHUD. Normally it shows a grid too, but you can configure it how you like.

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On 15/06/2016 at 3:32 PM, FourGreenFields said:

And screw not being able to post on the WT forum if you haven't played for a while.

I feel you. I really feel you.

Edited by Matuchkin

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On 13/09/2016 at 5:30 PM, Van Disaster said:

Pretty old, but this give you some ideas? the bay doors open downwards. Uses yaw brakes for steering, the little fins are just for a bit of directional stability & help reduce yawing in turns.

21522173779_0512e73e3a_b.jpg

21090077103_0d1a3392d0_b.jpg

Building something like an actual B-2 also works:

21721820671_6d16f1c51b_b.jpg

just not the best thing you could build.

 

I made a B2 clone as well. The yawing should be done with thrust vectoring. In fact mine was so stable, that I could fly at up to mach 2.5 without any dramas. The picture of it is on my profile pic. You can see I am going fast by the red glow of entry burn over the front of the plane.

I can see why they are very efficient as a bomber once building one. Two things, the lack of a tail and focus on epic amounts of lift, makes them have an amazing glide angle with crap loads of lift. The second thing is that all that lift means they can carry a huge payload. Which is why they are very suitable as a bomber.

I wonder if anyone on here managed to make a B2 style plane get into space and successfully re enter and land on the runway. :P

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Inspired by one of ferrams posts... BEHOLD; THE MEGA CESSNA; KING OF THE SKIES

Spoiler

V8OKoTy.png

This 50 TONNE BEHEMOTH SOARS above your PETTY REGULAR Cessna's, DOMINATING the COMPETITION and holding it's DESERVED TITLE; ALPHA MALE of ALL AIRPLANES. It CRUSHES any OPPOSING PATHETIC PLANES with it's GIGANTIC SIZE AND WEIGHT, cruising at a top air speed of an OUTSTANDING 30 M/S !!!!!

 

jlxVUkF.png

With it's IMPRESSIVE 80!!! METER WINGSPAN, it glides with EASE above *Insert Competitor Here*'s --> INFERIOR <-- products!

g3pDdAz.png

Able to take off, fly, then land again in ONLY 10 METERS! This craft has INCREDIBLE agility!

yKqMQvc.png

LEGENDARY COLLECTORS MILITARY EDITION is available for ONLY $50,000 more! Control the skies with this BEHEMOTH of SUPERIOR *ALL AMERICAN* ENGINEERING. For every unit solved we will donate $100 !!! DOLLARS to CRUSHING the *Facist-Commie* rocket-building terrorists in the VAB! A worthy cause!

 

zk25VaY.png

buy now

Suprisingly, for a craft with only 100kN of thrust at the front, it flew pretty well. I suppose the gigantic frame and wings provide it with so much lift, a light breeze will pick it up. Suitably, it flew like a paper airplane.

Edited by SirusKing

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I posted to the FAR thread a moment ago asking for thoughts on behaviour changes with the current dev build, but figured I better post the craft files here and not on the main thread.

Here are the craft files I've been testing with. They're FAR-compatible versions of Mark Thrimm 's low tech space planes, and they were modified in KSP 1.1.3 for use with FAR Lanchester. They seem to load and fly in KSP 1.2.2 with the current dev build, but I'm finding I need less fuel to get to orbit and needed to move my tail planes to the rear a bit.

Is anyone here testing the dev build noticing a similar change with fuel use and tail stability? These files weren't changed for 1.2.2

--

Edited by Gordon Fecyk
How do you do the @username in blue properly?

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On 13/09/2016 at 6:30 AM, Van Disaster said:

Pretty old, but this give you some ideas? the bay doors open downwards. Uses yaw brakes for steering, the little fins are just for a bit of directional stability & help reduce yawing in turns.

21522173779_0512e73e3a_b.jpg

21090077103_0d1a3392d0_b.jpg

Building something like an actual B-2 also works:

21721820671_6d16f1c51b_b.jpg

just not the best thing you could build.

How do you build a plane without tail fins that don't sideslip?

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50 minutes ago, Scoppio said:

How do you build a plane without tail fins that don't sideslip?

Notice in the last picture how the control surfaces on the wing are deploying in opposite directions?  That causes drag on that side and allows the flight control software (or SAS, to a lesser extent) to  fight the natural yaw instability.  I think there's a control surface setting for that in FAR but I don't remember what it's called.

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On 15.1.2017 at 6:43 AM, Scoppio said:

How do you build a plane without tail fins that don't sideslip?

The B-2 there used artificial stability, as blowfish mentioned (I think the setting was called yaw brake).

However, it is possible to make a plane yaw stable (aerodynamically, not artificial stability) without dedicated tail fins. The most kerbal way is probably to add drag on the tail (like a chute), but that kind of limits your speed. Wing sweep also increases yaw stability, although not usually to an extend that allows you to remove a tail fin. Probably the easiest way is to add an di-/anhedral angle to your wingtips, when using wing sweep - they'll work similar to a tail fin, but aren't technically tail fins. Usually a good idea to use artificial stability/fly-by-wire on top of that.

And keep your CoM close to the nose, as that'll increase stability anyway.

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Hangar from my 1.1.3 save:

4gPnbxM.jpg

From bottom to top;

The Happy Hopper: built for scenic sunset flights and so the other planes could feel superior.

The Jolly Jumper: built to travel Kerbin in style, when speed (or safety) isn't necessary.

The Straight Arrow: built for serious, simple, stable flying, and not for doing cobras over the VAB.

The Calavera: built for doing cobras over the VAB.

The Hazard: built through a series of accidents, the tail planes being accidentally installed on the front of the plane, and the wings being installed backwards. Later declared "an important first step into innovative technologies".

The Titanium Titan: built for taking cargo to orbit at hypersonic speed. Unfortunately the only cargo it could carry all the way to orbit was itself.

The Carbon Composite Colossus: popularly known as the "spaceplane that takes spaceplanes to space", it was built to prove that an SSTO that took SSTOs to orbit wasn't a stupid idea. Largely considered a stupid idea.

Calavera SSTO version: although capable of reaching orbit by itself, was usually carried on the back of the Carbon Composite Colossus. Built for doing cobras on Minmus.

 

I would really like to see similar posts by you guys, with all your planes shown on a single picture (even the ones that didn't work so well!) with a small description. I think it's cool seeing all the planes in scale.

As a bonus, my F-16 replica built to test mods on 1.2.2.

4F22hRl.png

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I've recently gotten back into playing KSP and after settling in and getting back into the saddle, I've created two planes I'm somewhat satisfied with, though both do have a lot of problems. Here's a picture of them both.

What I'm concerned with is the beauty in the back, the F-5E Mayfly (One can easily guess where the inspiration came from). Here's another shot.

The problem is, it turns quite slow. I've tried multiple wing sizes and configurations (and even a canard) but it either does little or makes the plane jerk upward while turning and have the "turning bob" problem. It's a big shame, since the fuselage looks amazing. Any suggestions on how to fix it would be greatly appreciated. It's supposed to be a fighter that dogfights at around subsonic speed, so supersonic turning performance isn't important.

Curves and CoP & CoM location

AoA Graph at 0

AoA Graph at 1

Derivatives

An unrelated question, does anybody know where tetryds' post about optimizing control surface is? I've been trying to look for it for ages. I've just looked through this entire thread and either I'm blind or it's gone.

Another question: What's the 'Ref Area' value for in the stability derivatives panel? Is it wing area? 

Thanks!

 

 

 

 

Edited by CrayzeeMonkey
Of course I would link to the wrong images :)

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It's on my signature :wink:

What you have there is that when you fully deflect your elevators for pitch up you stall, you can notice that because the yellow line crosses the zero after the blue line drops.

First of all edit every other control surface to not respont do pitch up, then edit your elevators to deflect less. (also make sure to make all control surfaces do what they are meant to do)

Reduce deflection until the yellow line crosses the zero line before the blue line drops, the closer the yellow line zero cross is from the point where the blue line drops, the harder you will turn, draining energy.

You can balance that until you find a point that is both great to fly with a keyboard and will still turn well for what your airplane is capable of.

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2 hours ago, tetryds said:

It's on my signature :wink:

What you have there is that when you fully deflect your elevators for pitch up you stall, you can notice that because the yellow line crosses the zero after the blue line drops.

*snip*

I think the three bottom links in your signature (including the deflection one) are broken. I think they're still using the old pre-migration links and they only send me to the thread that the post was in. I was actually trying to hunt those posts down a long time ago (Thinking they would change how I would build planes forever) and was considering sending you a PM about those broken links, but didn't considering that you might be quite busy (You were a former moderator, right?).

That one tip you just suggested may indeed change how I'll build planes from now on. Applying your techniques, the Mayfly now flies like a dream. I also applied the same to a bunch of my other planes and I'm seeing massive improvements. Thanks!

I'm trying to figure out why this trick might be working. I'm assuming that Cm is pitch moment where negative Cm = pitch down moment and inversely. I'm guessing that when the Cm's x intercept is before the Cl drop, the plane stops pitching up even more to reach the critical AoA, leading to a more stable flight. On the other hand, when the critical AoA is met before Cm's x intercept, the nose jerks back down, however, the plane can still pitch up, making it hit critical AoA, leading to the nose jerking back down again, pitching to hit critical AoA and so on, creating that bobbing issue that's been bugging me since I've tinkered with FAR.

Is this correct? I have never read the static analysis graph like this before. It's quite fascinating trying to figure out why this happens.

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8 hours ago, CrayzeeMonkey said:

I think the three bottom links in your signature (including the deflection one) are broken. I think they're still using the old pre-migration links and they only send me to the thread that the post was in. I was actually trying to hunt those posts down a long time ago (Thinking they would change how I would build planes forever) and was considering sending you a PM about those broken links, but didn't considering that you might be quite busy (You were a former moderator, right?).

That one tip you just suggested may indeed change how I'll build planes from now on. Applying your techniques, the Mayfly now flies like a dream. I also applied the same to a bunch of my other planes and I'm seeing massive improvements. Thanks!

I'm trying to figure out why this trick might be working. I'm assuming that Cm is pitch moment where negative Cm = pitch down moment and inversely. I'm guessing that when the Cm's x intercept is before the Cl drop, the plane stops pitching up even more to reach the critical AoA, leading to a more stable flight. On the other hand, when the critical AoA is met before Cm's x intercept, the nose jerks back down, however, the plane can still pitch up, making it hit critical AoA, leading to the nose jerking back down again, pitching to hit critical AoA and so on, creating that bobbing issue that's been bugging me since I've tinkered with FAR.

Is this correct? I have never read the static analysis graph like this before. It's quite fascinating trying to figure out why this happens.

You almost nailed it.

What happens is that the point where the Cl drops is the point where you stall and the moment you stall the wings lose lift and gain a lot of drag.

Depending on the design this can generate a lot of pitch down torque, your craft quickly goes back to an AoA where it stops stalling, but the deflection brings it back up and that happens again.

On the worst case it will gain so much momentum that it stalls pitching down too, and keeps doing that without any input.

Be careful though, as applying what I suggested does not guarantee you won't stall, if you have enough pitch up momentum and little damping you will slingshot past the stall point and bounce back (or die).

It is actually possible to balance your airplane in such a way that the stall effects are neutral, the airplane does not bounce back nor flips backwards, you maintain stupid high AoA, only losing effectiveness on your control surfaces and bleeding a lot of energy.

I made airplanes which behaved like that a few times, it's fun, if you throw some artificial stability on it you get top notch control over your aircraft when dogfighting, as long as you don't overstress it.

I can share an airplane that does this later :)

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Low-Tech Space Planes by Thrimm Aerospace, modified for FAR

(Note: KSP 1.2.2 with FAR dev build. Aero behaviour may change with final release.)

lts-far.png

@Thrimm developed these great space planes about six months ago. Some folks asked about FAR compatibility, so I thought I'd give it a shot. This is the end result of on-and-off play and even experimenting with the FAR dev build for KSP 1.2.2. Here are the craft files. (79 KB, KSP 1.2.2) That is the wrong link; Here's the right one.

LTS Dove-F:

lts-dove-f.png

Required Tech: Aviation (T3), Advanced Rocketry (T3), Landing (T4), Engineering 101 (T1).

Optional Tech: Survivability (T2), Electrics (T4)

Power Plant: 8 x J-20 Juno, 2 x LV-909 Terrier, 1 x LV-T45 Swivel

Capacity: 1 x Crew, optionally 1 x OKTO, Batteries, Science

Thrimm built the Dove as a proof-of-concept for a low-tech space plane, but with an OKTO as auto-pilot it works as a rescue craft early in Career mode. With stock aerodynamics, this craft could only reach about 5500 m before needing to light the main engines, and even then in KSP 1.1.3 we didn't have fuel lines at this low tech level so the original Reliant would burn out too soon. FAR lets us take these Junos over 8000 m up, and in 1.2.2 with default fuel flow enabled we can use the Swivel and Terriers all the way up to a 75 km apoapsis, shut off the Swivel, then use the Terriers to close orbit. More tail planes help with yaw stability on take-off.

Instructions: Enable DPCR in FAR. Climb to about 8 km to 10 km, point 20 degrees, stage main engines. Throttle off and shut off Swivel after achieving 75 km apoapsis, then close your orbit with the Terriers. You'll need to start closing pretty early with the low thrust but you'll save a lot of fuel. On re-entry, point radial-out and shut off Terriers. You'll likely lose control at 20-25 km altitude, but your Junos should light back up shortly after. Find prograde, then pull up to level flight. Stage drogues no higher than 100 m altitude when over runway.

LTS Sparrow-FC:

lts-sparrow-fc.png 

Required Tech: Basic Rocketry (T1), Supersonic Flight (T5), Landing (T4), Fuel Systems (T4), Engineering 101 (T1), Aerodynamics (T4)

Optional Tech: Survivability (T2), Electrics (T4)

Power Plant: 2 x J-404 Panther, 2 x LV-T45 Swivel

Capacity: 3 Crew, 1.1 tonne cargo

Thrimm tells us this is for crew training and tourism, but the FAR drag model lets us use less fuel on ascent. I replaced the Mk2 liquid fuel fuselage with the Mk2 short cargo bay from his LTS Kestrel. The Sparrow-FC can fill the original Kestrel's role as a small satellite launcher. This example launches a 1.13 t FT-L200 fuel tank.

Instructions: Enable DPCR in FAR. Launch with Panthers in Wet mode (Abort action group) and point up 35-40 degrees. High dynamic pressure will give you maneuverability problems at too low an altitude, so climb quickly. Stage Swivels at 16 km up or higher, and try to avoid exceeding 10-12 degrees angle of attack. Cut thrust when hitting 75 km apoapsis and point prograde in Surface mode to reduce drag. Use RCS action group to open cargo doors once in LKO. On re-entry it may help to balance fuel between the rear and forward fuel tanks, otherwise descend and land similar to the Dove-F using the drogues. You might have trouble leveling off due to high dynamic pressure and (I think) Mach Tuck; if so, shift fuel more to the rearmost tanks or try turning DPCR off and pitch up gently!

LTS Kestrel-FC

lts-kestrel-fc.png 

Required Tech: Basic Rocketry (T1), Supersonic Flight (T5), Landing (T4), Fuel Systems (T4), Engineering 101 (T1), Aerodynamics (T4)

Power Plant: 4 x J-404 Panther, 2 x LV-T45 Swivel

Capacity: 2 Crew, 4.5 tonne cargo

Similar to how the Sparrow-FC can serve the Kestrel's original role, I thought with FAR's drag model I could get away with more cargo capacity. First I had to replace those really narrow wings though, since FAR laughed at them as this craft turned into a lawn dart. Swiping the wings from the Dove and Sparrow seemed to do the job. Everyone uses the Rockomax Jumbo-64 "Orange Tank" as the benchmark for Mk3 single-stage-to-orbit craft, but I wondered if the largest Mk1 tank, the FL-T800, could be a benchmark for Mk2 craft. It seems to work as long as I expanded the fuel capacity of the original craft as well; note the extra FL-T100s at the rear.

Instructions: Enable DPCR in FAR. Launch with Panthers in Dry mode. Aim 40-45 degrees up, and switch to Wet mode (Abort action group). Ironically, higher dynamic pressure seems to keep this craft stable on ascent. Stage the Swivels at 19-20 km up, and avoid an angle-of-attack greater than 10-12 degrees. Cut thrust at about 75 km apoapsis and point prograde in Surface mode to reduce drag. Use RCS action group to open doors once in LKO. Re-enter, descend and land similarly to Sparrow-FC, but its larger mass will mean greater momentum and possibly a more difficult time leveling off and avoiding Mach Tuck.

I tried using the elevons as air brakes once, and it didn't end well for the wings. Fortunately, the drogues still worked if I adjusted the deploy altitude, and an almost-empty craft will survive a nose-first impact at around 22 m/s.

I'll make corrections if needed, for instance if I got the tech tiers wrong.

--

 

Edited by Gordon Fecyk
Fixed wrong download link

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Here's a couple designs that make use of procedural wings:

B-900C (Cargo variant of the Kercel K-900):

6U1Fa1Q.png?1

nBp4hDH.png?1

Equipped with retrorockets because something about my install means there is practically no drag on aircraft.

X-33b:

Q7ro24w.png?1

lmN1bXC.png?3

A small scale flying wing test with airbrakes as yaw control (so it is a true flying wing). Surprisingly stable until it makes a major course change due to high yaw instability thanks to the way SAS works. It proved too difficult to fix, so the concept of building a true flying wing in KSP has been abandoned for now.

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Pseudo MiG-23:

0WkKDsAl.png

Does anybody know of any way to increase roll authority during sustained turns? A common problem with this plane is that it essentially locks up roll-wise and then proceeds to pitch up while turning.

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5 hours ago, CrayzeeMonkey said:

Does anybody know of any way to increase roll authority during sustained turns? A common problem with this plane is that it essentially locks up roll-wise and then proceeds to pitch up while turning.

I'd guess that might be due to dihedral effect. If you roll at high AoA without using rudder with ailerons (left ailerons -> left rudder) you'll turn your AoA into slip angle, which then causes roll in the opposite direction. Not entirely sure if it's that, but worth a try I'd say.

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On 2/9/2017 at 3:01 AM, FourGreenFields said:

I'd guess that might be due to dihedral effect. If you roll at high AoA without using rudder with ailerons (left ailerons -> left rudder) you'll turn your AoA into slip angle, which then causes roll in the opposite direction. Not entirely sure if it's that, but worth a try I'd say.

There was no dihedral on the plane, but on turns I discovered that the wings had a tendency to flex up and cause a dihedral of some sort. A strut later it was reduced and the plane can turn much better now.

Thanks!

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2 hours ago, CrayzeeMonkey said:

There was no dihedral on the plane, but on turns I discovered that the wings had a tendency to flex up and cause a dihedral of some sort. A strut later it was reduced and the plane can turn much better now.

Thanks!

To save on weight you could also try adding a slight anhedral that will naturally flex up during high G-loading for better roll authority and droop down in level flight for better stability. It seems to work pretty well for fast-mover designs, it made my Mig-25 lookalike really nimble.

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