ferram4

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

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I found an odd incompatibility between Mechjeb2, FAR VoxelAeroPort that I pulled a day or two ago, and at least one other mod - I'm not sure exactly what the other mod/part is and it may in fact be a stock part (I'm suspecting the stock service bays actually). What happens is, while in orbit (have to be in orbit for this), and I use the MJ2's "show landing predictions," it cuts the FPS down below 10. Turn this checkbox off and it goes back up to 40-60+ fps like normal. On 0.90, oldFAR definitely did not do this, but.. we didn't have service bays then either. Has anyone else run into this? I'm going to do a few more tests.

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I've been playing around with with nuFAR and have made a "single engine" Black Bird.

It doesn't look amazing, but it works. I can get it up to 400m/s (Mach 1.15) at sea level. Flying higher than 4000m it an accelerate until the new heating mechanics combust it. I have been getting it up to 1200 m/s at 5000m, before it exploded due to overheating. It uses a standard turbojet (not the basic jet). It has no modded parts, so it would work as a stock craft. You can get it here: http://www./download/40n2zu43g64e6ka/Sonic+Hunter+III.craft.

As you see I went 740m/s in the last image and I was still accelerating at 10m/s.

PS: The landing gear sticking out the top of the fuselage underneath the elevator isn't there to look funny. I had to place it there to smooth out the derivative of the cross section area graph. It reduces the mach shock wave drag area by 0.2m^2 from 1.85 m^2 to 1.65 m^2. So it reduces the supersonic drag by ~10 % (!).

Now some pictures:

VStFduE.png

ULXyWrZ.png

lodiKMN.png

Edited by 4plains

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@Vegemeister: 1) I need reproduction steps.

2) It's not supposed to save its position.

@ss8913: The only thing odd is that you expect a prediction to work perfectly when MJ has no idea what to call to predict. NuFAR is a complete refactor with very little left of the old methods. If it was compatible, that would be damn amazing.

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@Ferram4

Reproduction steps for +/- infinity, using a fresh copy of 64-bit KSP on Linux with only nuFAR and its dependencies installed:

1. Create a new sandbox game.

2. Go to the SPH.

3. Place a MK1 Cockpit.

4. Open the FAR dialog, go to the stability derivatives panel, and hit calculate.

5. Launch.

6. Revert to SPH.

7. Calculate stability derivatives again.

The important part seems to be that you calculate the derivatives, launch and revert, and calculate the derivatives again.

Edit: Actually, it also happens if I exit to the overview and return to the SPH, instead of launching.

Edited by Vegemeister

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B9 procedural parts has variable thickness wings. I don't know about pwings.

I can't wait. This is going to be awesome.

Yes, that's why I mentioned them ;) we are not flush with parts which vary their thickness lengthwise though. I'm aware of odd tail pieces and proc structural parts, but clipping won't help if parts start eating cargo bay space. Once again an issue for parts packs.

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@ferram4 - I'm still trying to nail down the exact part that's the third variable in the equation. I'm also trying to figure out why this is an issue on, say, the Mun, which has no air. I've mentioned this over on the MJ2 forum thread as well and they don't seem to have much of an idea. Wasn't complaining about FAR by any means; was just wondering if you or anyone had noticed this and/or had any ideas as to what might be causing it, or a workaround of some sort.

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I'm not sure what is causing the conflict, but I don't get a FAR button on my toolbar, though I can tell during test flights that it is installed. I'm running the latest devbuild, will try deleting other mods 1 at a time to find the cause.

EDIT: Deleted KSP, reinstalled, this time only having Squad, FAR, and ModuleManager in gamedata, still no FAR GUI...weird

Edited by Bloodbunny

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Yeah, actually placing the aerodynamic center in the right place is actually a difficult challenge to get right, unfortunately. The indicator is currently wherever the forces are applied, but with a moment attached that can also vary with angle of attack, and that kind of defeats the purpose of using it for stability. Frankly, I prefer the graphs myself, they're clearer, but people want indicators, so I'll see what I can do.

The subsonic zero-lift drag is probably a little low simply because I'm not accounting for all the interference drag and what not, I may be able to add a factor to increase that based on variations from a nice, simple body of revolution, but I don't know how bad that might be.

Would it be possible to use the slope of the best-fit line for Cm vs. AoA (the yellow graph) as a basis for the distance of the CoL indicator from the CoM indicator? A positive slope would place the CoL in front while a negative slope would place the CoL at the back.

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Everything's working all nicely enough for me with 1.0 and nuFAR, but for some reason every time I return to the space center, the Aerodynamic Failures button gets checked again. Is there a cfg file I can edit so it doesn't revert?

Also, B9 Procwings works well for me. The voxel aero debug takes account of the shapes nicely!

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For the MJ issue, I've encountered it during a landing for the Mun. It NaN's closest approach distance (which tanks FPS as a result). Since this is very similar to your situation, I suppose it is fair to say it's incompatible with nuFAR in this regard. For now, don't use this info item or modules that need it (I'd imagine landing assistant is one of them).

Everything's working all nicely enough for me with 1.0 and nuFAR, but for some reason every time I return to the space center, the Aerodynamic Failures button gets checked again. Is there a cfg file I can edit so it doesn't revert?

Also, B9 Procwings works well for me. The voxel aero debug takes account of the shapes nicely!

I saw some git commits about settings not saving yesterday, you could try a new build.

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Thanks, Ferram.

Would something like this work as well?

Beagle.png

I'm mostly worried about the scientific instruments and the radiators. I could remove the lights and find a better solution for the landing gear. The ladders are unavoidable.

Edited by SymbolicFrank

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Thanks, Ferram.

Would something like this work as well?

I'm mostly worried about the scientific instruments and the radiators. I could remove the lights and find a better solution for the landing gear. The ladders are unavoidable.

I know I'm not Ferram obviously but putting all the stuff in a Service Bay would work, and I would make the ladders 2x symmetry to even out the drag as I assume they are rendered unlike in stock.

also to deal with the landing gear in forwards motion I would put them under a lip like this

qvViQLW.jpg

for revealable flight air breaks should would work if you put them at the top of the craft but I haven't tried it in new FAR. If you get creative enough and use tools like tweekscales and when there updated B9 procedural wings B9 and some other stuff you would be surprised what you can do, even with stock only you would be supprized but you would have to work harder.

one other solution if your just looking for stability and not ease of motion though the atmos is to move the science and rad's to the bottom of the craft where they will make the smallest different to the cross section and create drag keeping you going on you velocity vector as long as you use symmetry or otherwise it will create drag on one side of your craft unless your very very very careful and iterate A LOT, you also have to balance the mass as well so its not even worth the hassle.

Edit: Also if when your ascending the first time you could use an interstage fairing, as I assume your dropping everything below the landing legs so it will make your first assent more efficient and will remove the drag from the landing legs which when your first lunching it will be near the top of the craft.

Which you should be aiming to reduce drag at the top of your craft and sharp deviation in width.

This is basically what you should be aiming for, I don't mean this vessel obviously but I mean this shape and the places where things like science have been stored.

GsARDIK.png

Edited by etheoma

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So I've made a plane that flies quite well on my install. It's subsonic as it uses a basic jet but it flies well and is fairly agile.

It flies so well that I'm suspicious of it and whether FAR is working on my machine.

Would anyone be interested in giving it a fly so I can see if it is OK?

http://www./download/4dtju2miy8s48ed/Nu_FAR_Stable_flyer.craft

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Thanks, etheoma. I'll try to fit the instruments into some service bays. But that does make it higher and more top heavy. Of course I fit a fairing when I'm happy with it.

The landing gear is a problem, because it has to be as much to the side as possible, to prevent the craft from tilting if the surface is a bit sloped.

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For the MJ issue, I've encountered it during a landing for the Mun. It NaN's closest approach distance (which tanks FPS as a result). Since this is very similar to your situation, I suppose it is fair to say it's incompatible with nuFAR in this regard. For now, don't use this info item or modules that need it (I'd imagine landing assistant is one of them).

I saw some git commits about settings not saving yesterday, you could try a new build.

That makes sense. Is this something (the MJ issue) that will need to be fixed on the MJ side or the FAR side at some point? I wouldn't expect the MJ team to go after it too hard until nuFAR is officially released, but I'm not sure where it needs to be fixed - it sounds to me and my ignorance like it's more of a Mechjeb issue than a FAR issue though..?

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Thanks, etheoma. I'll try to fit the instruments into some service bays. But that does make it higher and more top heavy. Of course I fit a fairing when I'm happy with it.

The landing gear is a problem, because it has to be as much to the side as possible, to prevent the craft from tilting if the surface is a bit sloped.

You could use infernal robotics with some telescoping parts to extend out the landing legs when you need them like so.

oyYJaqx.png

Yeah infernal robotics is another one I suggest if you want to be able to expand what you can do. and with NuFAR you should be able to make a fairing and open and close it with infernal robotics I think, Not 100% sure on that one, or even 70%.

Edit; I said the pod might have difficulty with re-entry but I looked at the centre of mass and centre of lift and it looks good although you still have those big ass RCS thrusters / radial engines which will probably screw it up, but you have the fuel in the bottom and what are you using the fission reactor for btw because do you need a 1.25m fission reactor because if your just powering the ship you could go down to a 0.625 then you can fit it in the service bay actually bring your centre of mass way down.

Edited by etheoma

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I've been playing around with with nuFAR and have made a "single engine" Black Bird.

It doesn't look amazing, but it works. I can get it up to 400m/s (Mach 1.15) at sea level. Flying higher than 4000m it an accelerate until the new heating mechanics combust it. I have been getting it up to 1200 m/s at 5000m, before it exploded due to overheating. It uses a standard turbojet (not the basic jet). It has no modded parts, so it would work as a stock craft. You can get it here: http://www./download/40n2zu43g64e6ka/Sonic+Hunter+III.craft.

As you see I went 740m/s in the last image and I was still accelerating at 10m/s.

PS: The landing gear sticking out the top of the fuselage underneath the elevator isn't there to look funny. I had to place it there to smooth out the derivative of the cross section area graph. It reduces the mach shock wave drag area by 0.2m^2 from 1.85 m^2 to 1.65 m^2. So it reduces the supersonic drag by ~10 % (!).

Now some pictures:

<snip>

I see your Mach 3.5 capable jet and raise you an SSTO:

E261C212B26200747194D705CD17B9F29C67EC95

No horrible lumps this time- I managed to get a smooth profile entirely by using careful part placement.

Oh, and the wave drag area? 0.69m^2. It actually beats my earlier fighter design in spite of being much bigger.

I haven't yet landed it- KSP crashed when I was about 40 km from the KSC.

Also, those RAPIER engines are totally OP. I was getting something like 300 kN out of them at 20km altitude and mach 3.5. I'm pretty sure that under those conditions my plane could accelerate in a vertical climb.

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I wouldn't worry too much if you cannot meet the ideal shape with rockets. As long as the drag is not too one-sided you should be fine, since rockets reach high altitude, where drag becomes negligible, rather quick. If your TWR is reasonable (I'd say about 1.5 during launch, and quite a bit less than 5 when dropping the first stage), the aerodynamic forces should hopefully never get strong enough to damage anything.

With surface attached stuff it might in principle be more difficult to get the rocket stable, so adding fins/control surfaces at the bottom might be a good idea.

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With surface attached stuff it might in principle be more difficult to get the rocket stable, so adding fins/control surfaces at the bottom might be a good idea.

The point was that the drag was going to be uneven and also would create drag at the top of the craft in the first lunch so that was kinda the point that it would be unstable, aerodynamic efficiency was just a nice bonus.

if you look at the image the craft goes on for what I assume is the orbital injection stage.

Also... it looks more neat that way so win win win.

Edited by etheoma

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So I've made a plane that flies quite well on my install. It's subsonic as it uses a basic jet but it flies well and is fairly agile.

It flies so well that I'm suspicious of it and whether FAR is working on my machine.

Would anyone be interested in giving it a fly so I can see if it is OK?

http://www./download/4dtju2miy8s48ed/Nu_FAR_Stable_flyer.craft

Its fine for me. Nice and stable, though I did manage to prang it on landing due to inexpert flying with the keyboard.

Your plane is subsonic because its design has very high wave drag- take a look at the transonic design thing in the editor and you'll see what I mean. You can easily go supersonic with the basic jet engine, but you need to shape the plane so that it has smooth changes in cross section to minimize the buildup of drag inducing shockwaves. Several people including Ferram himself have posted pictures in the thread of area-ruled planes, so you should be able to work out the various tricks you need to use pretty easily :).

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The new FAR Colibri has a wave drag area of 0.3923 m^2.

I hope it serves as a good example on techniques to help people handle area ruling using stock parts.

Oh, and since one stationary BasicJet engine is too weak to lift it, it's no longer a VTOL.

*slightly outdated image*

pwrZ2fA.png

I guess I could squish some more out of it (Like getting rid of the ladder on the cockpit :P ), but I have other things to do, haha.

Edited by tetryds

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Its fine for me. Nice and stable, though I did manage to prang it on landing due to inexpert flying with the keyboard.

Your plane is subsonic because its design has very high wave drag- take a look at the transonic design thing in the editor and you'll see what I mean. You can easily go supersonic with the basic jet engine, but you need to shape the plane so that it has smooth changes in cross section to minimize the buildup of drag inducing shockwaves. Several people including Ferram himself have posted pictures in the thread of area-ruled planes, so you should be able to work out the various tricks you need to use pretty easily :).

I made it so due to the plane being an early career plane for exploring and contracts. It has fixed wheels as they are not unlocked yet.

The transonic performance made me think it was maybe bugged but now I think it's just that bad a design for mach 1+ ;)

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