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

[blowfish]

Hi.

Could anyone help me with this design ?

http://s15.postimg.org/3o1glpffb/001.jpghttp://s15.postimg.org/uxcu07gif/002.jpghttp://s15.postimg.org/uzwpn1k5z/003.jpghttp://s15.postimg.org/pd0cpkhnb/004.jpg

Is there any way I can tune it to take off and fly ? Or is it dead End and I should think design something totally different ? In order to accomplish recon mision I need to fly quite a long distance (entire ocean), climb to 18,5 k meters and fly around some area. It's early stage of carreer mode, i'm restricted to 30 parts, 20t of weight and so on. I came with idea of plane equipped with 2 jet engines and one rocket engine in the middle which i would start to get 19k alt in area of recon. Is there any chance this could fly ??

There are various reasons why it might not be getting off the runway:

1) CoL is too far back, meaning you won't be able to pitch up.

2) Landing gear too far back, meaning you won't be able to pitch up. The rear landing gear should be just behind the CoM.

3) Too much mass for the wing area. Though I don't think that's the issue here.

There are a few other things I see which might give you problems:

1) Those blunt ends are going to give you a lot of drag. The Size 0-Size 1 junction between the Mk1 pod and the rocket fuel tanks may also contribute.

2) That doesn't look like much intake. If you're going to be flying high you probably want more.

3) I don't think you need rocket propulsion to get that high, even with just basic jets. My knowledge of stock jets is a bit rusty - been using AJE for a while (which should make it harder if anything), but with enough intake the engines should continue to function, though you will have to be going pretty fast to maintain lift. If anything another jet engine might do you more good. If you end up getting flameouts, you could try hitting the targets ballistically - give yourself more thrust than you need, then when you get close (within ~50km) of the target, throttle up all the way and pitch up sharply, holding the nose up until you get to the target altitude, at which point you should be in the survey zone or very close. Throttle the engines just before they flame out. Then fall back down until you regain thrust and control authority.

4) I doubt you'll have range problems - those basic jets are pretty efficient.

[tetryds]

So I'm having a small issue and I think its that I'm just unfamiliar with FAR's proclivities (had it two days). I'm able to make planes that fly just fine, but I'm noticing a tendency for them to oscillate. Now they are not flexing structurally, its more that I feel like it constantly overcorrects when cruising, making the thing wobble. I feel like it stops when I'm in a solid climb so I think it has something to do when I'm trying to remain stable and floating around my minimum AoA. I'm not noticing any difference if I have the flight assist stuff on or not.

If that is caused by SAS simply decrease the max deflection angle of your control surfaces.

If it's not SAS please send a pic of your craft, there are a few things that can cause oscillations.

[Khazar]

• Rear landing gear look like it may not be aligned with the direction of travel. If they aren't straight, they will flex and can cause all sorts of mischief
  
• Rear landing gear also looks to be a long way back. How close are they to the CoM? It will take a lot to rotate if there is significant seperation.
  
• Rear landing gear looks to be lower than the front. This will pitch the craft down on the runway and force it into the ground. You want to reverse that.
  

Thanks for help. I was losing hope

Damn landing gear is the issue !! Thanks, i was slowly loosing hope.

I didn't give much attention to the landing gear, thought it didn't matter much. Most of my concern regarding rear landing gear was to make sure engines wont hit the ground when pulling up, so i just put them as low and as far i could. Didn't bother to put it near center of mas.

• That's an awful lot of jet fuel (3 tanks per basic jet). You can almost certainly drop that down to a single tank (each for structural purposes) and probably remove about half the fuel and still get to most places.
  

Well i made calculations based on fuel usage during my earlier attempts and I was aiming for 2 way trip with fuel reserve allowing me to stay in area for some time, but i suppose there could be a lot of design flaws reducing fuel efficiency

There are 2 fuel tanks per engine. So you say i would be good with just 1 per engine ?

I will provide screenshots when I'll get home, but I'm pretty sure landing gear is the problem.

As for analysis, I managed to get all green values at 0.25 mach with flaps down and values were green at various combinations of speed and alt I expected to be at during my flight.

I see a rocket engine there.

Your Center Of Mass is behind your Center Of Lift, almost certainly, that will cause your craft to flip over.

Also, you have roll instability, angle the tip of your wings upwards a bit.

Your craft is very heavy (assuming all tanks are full), thus you also need more tail, by that I mean bigger tail.

If you did not have the rocket fuel tanks on the middle you wouldn't need more tail, though.

A screenshot of the stability derivatives for 0m altitude Mach 0.35 and Mach 0.8, as well as a Steady-state "Sweep AoA" plot from 0 to 45 degrees, at Mach 0.35 and 200 pts would help a lot.

The "roll left and right" thing is because your landing gears are angled outwards.

Place them on the fuel tanks and you will fix that issue.

I'll check when I'll get back home, but i doubt I ever placed COM behind COL. Farthest I sometimes tried to place them as close to each other as possible but never moved COL past COM. And I don't flip over very often

I'll try tipping the wings, what to do about tail ? Is it better to use tailfins (no control surface) or controllable winglets ?

There are various reasons why it might not be getting off the runway:

There are a few other things I see which might give you problems:

1) Those blunt ends are going to give you a lot of drag.

Well I thought that entire part is an air intake and therefore it should remain open, but now after You mentioned it i suppose that those parts are actually fuselages with intakes visible at the bottom.

The Size 0-Size 1 junction between the Mk1 pod and the rocket fuel tanks may also contribute.

This 0-1 junction is supposed to be a bulb (or how to call that) helping during transsonic speeds, but originally there were another one cockpit making smooth pas, but i had to remove it when i reached 30 parts limit after adding more control surfaces. Now if I could remove 2 fuel tanks I could put it back. But would it work ? Is it good idea at all ?

2) That doesn't look like much intake. If you're going to be flying high you probably want more.

3) I don't think you need rocket propulsion to get that high, even with just basic jets. My knowledge of stock jets is a bit rusty - been using AJE for a while (which should make it harder if anything), but with enough intake the engines should continue to function, though you will have to be going pretty fast to maintain lift. If anything another jet engine might do you more good. If you end up getting flameouts, you could try hitting the targets ballistically - give yourself more thrust than you need, then when you get close (within ~50km) of the target, throttle up all the way and pitch up sharply, holding the nose up until you get to the target altitude, at which point you should be in the survey zone or very close. Throttle the engines just before they flame out. Then fall back down until you regain thrust and control authority.

4) I doubt you'll have range problems - those basic jets are pretty efficient.

I thought Rocket engine is easier way to get 18k for short time, than making efforts to keep jets running that high. I'll give it a try. How many intakes would I need to reach let's say 20k ? And do You consider 1 dual intake part as a 1 or 2 intakes ?

Edited February 24, 2015 by Khazar

[Crzyrndm]

Well i made calculations based on fuel usage during my earlier attempts and I was aiming for 2 way trip with fuel reserve allowing me to stay in area for some time, but i suppose there could be a lot of design flaws reducing fuel efficiency

Sounds like you have a particularly long trip to make, so maybe I was being a bit quick there. If you have already flown in the general vicinity a few times, you'd have the best idea of how much is required. Do you really need to come back all the way back though?

PS

I just built a replica for testing. Moving the gear in (reduces torque on wings which was causing some "fun") and forward meant I could take off if I was careful about how fast the nose came up.

The biggest issue I had with it is structural stability. Those side tanks are a complete nightmare attached as they are without any struts (not a huge issue in the air, but on the ground...)

Edited February 24, 2015 by Crzyrndm

[Khazar]

Thanks for help. So nice to hear that thing can actually fly

I tried so many tricks and changes to the design but didn't pay any attention to landing gear. <facepalm>

I haven't researched any structs so far, so I have to avoid more aggressive maneuvers for some time.

I would like also to ask if arranging fuel tanks like that would work ? :

Is it possible to put them like that ? Would they pass fuel if put that way ? Would it hold ?

[Crzyrndm]

Not quite sure what your picture is trying to convey. I rebuilt the plane to try and make it a little more structurally sound (plus a few other improvements). I can consistently get it off the ground now without it imploding which is a good start (Although I do keep clipping the rocket, which is less nice...). Short version is more wing, less control surfaces (what's there seems to be enough), and a big tail.

EDIT

Fixed link derp

Edited February 24, 2015 by Crzyrndm

[Khazar]

I meant something like above, but this is too extreme. Just to show the idea.

I always put fuel tanks in line, but how if I would twist them a little, the green ones outwards and the red ones inwards, and then pushing them one into another so there would be no irregular edges. This way I could manipulate with the shape of a plane quite a lot, and avoid sharp junction of one line capsule and 2 lines of engines. Thy would merge much nicer this way. But would this hold, and would they share fuel normally ??

In current stage of my career I can't exceed 15 m of width, 30 parts limit, 20 t of weight and so on. Your design has 19 so I can't afford it.

I can get a little bit around 15 m limit by folding wings up and down, but I doubt I could keep that long wings anyway.

[tetryds]

http://s9.postimg.org/fkgwwpkzv/003.jpg

I meant something like above, but this is too extreme. Just to show the idea.

I always put fuel tanks in line, but how if I would twist them a little, the green ones outwards and the red ones inwards, and then pushing them one into another so there would be no irregular edges. This way I could manipulate with the shape of a plane quite a lot, and avoid sharp junction of one line capsule and 2 lines of engines. Thy would merge much nicer this way. But would this hold, and would they share fuel normally ??

In current stage of my career I can't exceed 15 m of width, 30 parts limit, 20 t of weight and so on. Your design has 19 so I can't afford it.

I can get a little bit around 15 m limit by folding wings up and down, but I doubt I could keep that long wings anyway.

If you use the gizmos after placing tanks on the nodes, yes they will share fuel normally (it's actually a bit silly, floating around engines still work, etc.)

That is cool, I never thought about angling the tanks to shorten the aircraft before, mainly because I almost never play on career, haha.

FAR still does not know if there are sharp edges like that (it will, soon), so blending everything together is more aesthetics than functional, but yes you can do that.

Doing this will increase your Cd a bit, and bring your COL a bit forward, but nothing too bad.

About the COM/COL positioning, that is okay, to me it looks like it would be either very close or past it.

But did you check the COL movement during fuel burn? Sometimes starting and final COM positions are fine, but they can go past COL during the flight.

Just drain fuel like the game is going to drain it and see what happens.

Right now it consumes fuel from the furthest possible tank (given no fuel line loops).

It will change on 0.90, btw.

[Wanderfound]

I'd be inclined to just cut the wings down. Those wingtip extensions (shown at http://forum.kerbalspaceprogram.com/threads/20451-0-90-Ferram-Aerospace-Research-v0-14-6-12-27-14?p=1755270&viewfull=1#post1755270) are unnecessary; you can get away with short wings if you build appropriately.

[Khazar]

So far most of my flights lasted usually around second or something, so that possible weight distribution disturbance caused by fuel usage could be a problem I didn't have to worry about

This design is at stage where I gave up and decided I need to ask for help, so my efforts to make it fly despite dumb landing gear setup twisted it a little bit. Now that I know the importance of landing gear and some other useful things, I can go back and try to work with earlier versions of this design. I'll also try to put more intakes and go without rocket engine. If it turn out that jets will be able to run at 20 k alt that would make things easier. At the other hand that rocket engine could be useful during take off.

[Max.10.07]

Can you just make it not turn off on 64x i dont care if it crashes plz!!!

[tetryds]

So far most of my flights lasted usually around second or something, so that possible weight distribution disturbance caused by fuel usage could be a problem I didn't have to worry about

This design is at stage where I gave up and decided I need to ask for help, so my efforts to make it fly despite dumb landing gear setup twisted it a little bit. Now that I know the importance of landing gear and some other useful things, I can go back and try to work with earlier versions of this design. I'll also try to put more intakes and go without rocket engine. If it turn out that jets will be able to run at 20 k alt that would make things easier. At the other hand that rocket engine could be useful during take off.

If you think that you are able to learn by comparing versions of your craft, please post it here or pm me and I will fix it for you, telling what was making it go wrong.

Since you are on career mode I will try to use only the parts already on the craft, and don't overdo it on the cost

@Max.10.07: Well, there is no way you can know if an issue is caused by FAR or the stock game, it's not your fault.

It's so bad that there won't even be a x64 version on 1.0.

[Khazar]

Ok, thanks again. I will send you some of my designs. Would you prefer saved aircraft files or sets of screenshots ?

[Wanderfound]

Jets will definitely run at 20,000m, unless you've skimped on intakes to an extreme degree. Build a high altitude specialist, and you can keep the jets running well over 30,000m.

[Khazar]

I'm in career mode and I'm forced to use quite basic parts so far. I even had quite similar design at some point of my struggle, but it had same landing gear

[Wanderfound]

How low-tech are we talking about?

This one uses nothing over tier 7:

http://forum.kerbalspaceprogram.com/threads/90747-Kerbodyne-SSTO-Division-Omnibus-Thread?p=1630075&viewfull=1#post1630075

(presented as a demonstration, I appreciate that you're wanting to build your own here)

The issue of wingspan is a separate issue to tech level, though. High tech or low, most Kerbal aircraft designs tend to have too much wing and not enough tail.

[smjjames]

http://s9.postimg.org/fkgwwpkzv/003.jpg

I meant something like above, but this is too extreme. Just to show the idea.

I always put fuel tanks in line, but how if I would twist them a little, the green ones outwards and the red ones inwards, and then pushing them one into another so there would be no irregular edges. This way I could manipulate with the shape of a plane quite a lot, and avoid sharp junction of one line capsule and 2 lines of engines. Thy would merge much nicer this way. But would this hold, and would they share fuel normally ??

In current stage of my career I can't exceed 15 m of width, 30 parts limit, 20 t of weight and so on. Your design has 19 so I can't afford it.

I can get a little bit around 15 m limit by folding wings up and down, but I doubt I could keep that long wings anyway.

Doesn't the part clipping screw with FAR though?

[Max.10.07]

@tetryds Idc if its caused by anything, i dont read or share the crash reports anyway..

[Wanderfound]

Max: there is no 64-enabled release of FAR, and there will not be. This has been gone over several dozen times in this thread since the release of .90.

If you want to recompile 64-bit FAR for yourself, you're free to do so, and the information required to do this is available in other threads. If that doesn't sound like something you want to do, your remaining option is to switch back to 32-bit and dump whatever bloaty part packs are causing you to want 64-bit in the first place. Or go back to stock aero.

[smjjames]

@tetryds Idc if its caused by anything, i dont read or share the crash reports anyway..

There isn't even going to be a 64x exe available to run, so you might as well just stick with 32x.

Besides, 99% of my crashes are caused by memory leak issues, not the mods or anything else.

[Max.10.07]

Okei time to find out how to dekompile stuff.. And kompile non-part stuff...

[cantab]

your remaining option is to switch back to 32-bit and dump whatever bloaty part packs are causing you to want 64-bit in the first place. Or go back to stock aero.

Or make a Linux install. It feels like a bit much for just one game and it's not a magic bullet (the game might or might not run as well as on Windows depending on your computer), but it's an option.

[tetryds]

Okei time to find out how to dekompile stuff.. And kompile non-part stuff...

You must not decompile anything, mods have licenses.

What you should do is compile the code that can be found on git.

[cantab]

You must not decompile anything, mods have licenses.

And it depends on the license. So far as I am aware the GPL v3 does not prohibit decompilation or similar of object code recieved under it. You might want to do that for any number of reasons.

[smjjames]

You must not decompile anything, mods have licenses.

What you should do is compile the code that can be found on git.

I assumed he meant the exe. Good point though.