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

[NathanKell]

Balloon tanks, heh. Actually, with an NK-33* you might be able to make it to orbit with non-balloon tanks, although gawd help your payload fraction.

*Haven't run the numbers on whether you're better off with an RD-170 or deriv; higher Isp by ~10s both SL and vac, lower TWR.

[Kev]

Really nice mod. I have one little question however.

I build a spaceplane which flies perfectly (if skip fact that it tends to go perpendicular to velocity vector despite CoL is far back from CoM). However rocket engines create huge amount of drag despite being covered by interstage covers from KW.

Here is screenshots

http://i.imgur.com/ucYnJi3.png

http://i.imgur.com/wqgbAc6.png

There is plane's main body ending with Jets, with LFO tanks attached to it's sides. Behind this tanks i have interstage covers (front backwards) and Vesta rocket engines inside. And this engines creating tons of drag. A lot more than any other part of plane.

So, what is wrong here? Is that because i have open back of them?

Also, sometimes CoM stops showing for some reason. Looks like it begin doing so after i add some part.

I'm using 0.12.5.2.

Edited January 8, 2014 by Kev

[ferram4]

The center of mass issue is some other mod; FAR doesn't change masses, so it can't affect that indicator.

The drag on the engines is simply because it's the back-most part of that stack, which means that it gets all of the pressure drag that would be applied to the back part of that object. If you had any other part there, you'd get the same amount of drag so long as it's the back of a long stack, with the exception of the jet engines, due to the mass flow through the entire thing, so it's sort-of like it's not there. The pressure drag is something you'll have to design around.

That said, the drag is quite a bit higher than it would be in real life, but that's a necessary evil to deal with the fact that rocket engines in KSP are 3 times as heavy as they should be, making rockets much more unstable unless some type of compensation is added.

[Konnor]

@ferram4: 0.12.5.2 indeed fixed an issue with exploding inactive vessels, thanks!

@Virindi: AFAIK, getting a plane into space in reality is challenging because at hypersonic speeds the air is too hot to feed an air-breething engine. But yes, KSP does not take this into account, and recent update made it significantly easier. However, Interstellar mod has some intersesting overheating mechanics and precoolers for air-breathing engines.

[foamyesque]

Sure it's easy to make a SSTO in RSS. All you need to do is take an old Atlas rocket, replace the original engines with an NK-33 or some kind of equivalent and make sure you're only using a Mercury capsule. Bang, SSTO.

Pft Mercury.

(also illustrated: why people don't actually build SSTOs)

Also, ferram, I've noticed something somewhat frustrating: I have a Duna mission in mind, which has a winged lander hooked nose-to-nose of the rest of the stack. To test it without needing to assemble the whole thing in orbit, I built it in the VAB first and hyperedited it into space. The control surfaces are treated as being ahead of the centre of mass. That is correct as built, since the lander is reversed in orientation. However, even when switching controlling modules, the lander continues to have its control surfaces act as leading surfaces instead of the trailing surfaces they should be. Once undocked, they behave correctly again.

[Kev]

That said, the drag is quite a bit higher than it would be in real life, but that's a necessary evil to deal with the fact that rocket engines in KSP are 3 times as heavy as they should be, making rockets much more unstable unless some type of compensation is added.

Ah, i see. So drag of rocket engines is exaggregated to compensate exaggregated mass.

Ok, thanks for answer and for awesome mod. I'll see what i can do.

[Guest]

Would that be possible to make that a toggle? For mods with more realistic engine masses, such exaggeration would be unnecessary.

[AndreyATGB]

I don't oppose the idea of a toggle, but FAR's drag is IMO not very harsh at all. I doubt the added drag causes any significant changes in dV you might need for orbit considering drag is almost nonexistent compared to gravity losses.

[Kev]

I don't oppose the idea of a toggle, but FAR's drag is IMO not very harsh at all. I doubt the added drag causes any significant changes in dV you might need for orbit considering drag is almost nonexistent compared to gravity losses.

Yeah, added drag is not very significant. It just impedes plane's take off and climb to acceleration height. I'm fine with it. Actually, tailcones hepled me significantly, reduced drag of engines (including cones itself and decouplers) by about 70% maybe.

[NathanKell]

It already *is* configurable.

in config.xml, the sonic and incompressible drag lines, IIRC. Correct values for RSS/RF:

    <string name="incompressibleRearAttachDrag">0.01</string>
    <string name="sonicRearAdditionalAttachDrag">0.2</string>

And, if using RO,

    <string name="attachNodeDiameterFactor">1.0</string>

[Starwhip]

Something I've noticed is that when I try to rotate the view, it won't let me. This only occurs when viewing the rocket. In map, crew, and editor views it still works. I have Kethane and Procedural Fairings installed. Anyone have some advice.

I'm using a touchpad. A mouse might solve it, I'll have to check later.

[junkie_business]

@junkie_business: Try v0.12.5.2. I removed everything that should cause that issue from the code.

The problem I've had looks to be the same as the one in the video Selgad linked in post #2758. I've got 12.5.2 now and it seems to be working properly. Thanks Ferram.

[AndreyATGB]

Something I've tried to do was make a plane that can fly with one engine, supposedly like airliners can. Best I could do was a pretty huge delta winged plane that could do this up to about 30% thrust. It generates more than enough thrust to fly, but is not very stable without one engine. I was wondering how can I do this like real planes, their engines are much further apart than mine (mine were 1/3 a fuselage away from the middle). I can't post pics, it's too late at night.

[Surefoot]

Real planes that can do this have got a very stable aerodynamic configuration, and the first thing you'll notice is the huge tail fin (especially airliners). I managed to do it with my hypersonic jet so i guess it's easier to do with a subsonic one.

[themongoose]

I am a late entry to using FAR, but I had decided to give it a go.

So far I have been flying my stock plane designs and trying to modify or update them to work with FAR, so far so good. I have managed to get my mini-spaceplane into orbit with a few minor tweaks.

But I have come across one problem that I cannot seem to realise what is causing it. I was trying to create a gull-wing type craft, for landing on rough ground etc, however the damn thing just pulls to one side as soon as it is airbourne - so much that it cannot be recovered from. It doesn't pull to one side on the ground, like the usual misalligned gear issues.

The same craft works fine with straight wings, and the only problem I can think is because the propeller (firespitter) engines are mounted on the wings, the CoL has moved slightly above the CoM due to the gullwing shape, when it was previously inlined. But the difference is minute and I am sure real world gullwing planes like flying boats with wing mounted engines would have the same CoM placement, but fly succesfully.

The CoL is also ahead of the CoM and CoL, due to the design with front-mounted engines, but again, real world prop planes would have the same configuration.

Has anyone else out there succesfully flown a gullwing? With wing mounted engines?

[ferram4]

@foamyesque: That's because it saves the control surface "position" relative to the craft and its direction to try and save an extra calculation every frame. Fixing it is on my to-do list, but first I have to see if there's an event that runs when the referenceTransform of a vessel is updated so I don't have to poll the transform every frame.

@Dragon01: NathanKell is correct. I set that up when RSS came out so that I didn't have to force a compromise between stock real-like and actually real aerodynamics. Overall, it doesn't affect things too much since most craft are so large in RSS that the drag forces on them are mostly negligible until you're reentering something.

@Starwhip: I don't think that's something that FAR can cause. What other mods are you using? Can you post an output_log.txt (from KSP_Data)? Can you reproduce the bug at will? If so, how?

@AndreyATGB: Add a big rudder. Also, keep in mind that even with FAR installed the jet engines are still somewhat overpowered, so you're dealing with a greater yaw moment due to offset thrust than in real life.

[NathanKell]

Ferram, I'm running into an issue with NREs when I add your control surface module to the FASA Redstone fins. Appears on load craft in VAB, but seems to work fine thereafter (in VAB and in flight; error doesn't recur either).

NullReferenceException
  at (wrapper managed-to-native) UnityEngine.Component:InternalGetTransform ()

  at UnityEngine.Component.get_transform () [0x00000] in <filename unknown>:0 

  at ferram4.FARControllableSurface.CalculateSurfaceFunctions () [0x00000] in <filename unknown>:0 

  at ferram4.FARControllableSurface.FixedUpdate () [0x00000] in <filename unknown>:0 

[Black-Talon]

... I was trying to create a gull-wing type craft, for landing on rough ground etc, however the damn thing just pulls to one side as soon as it is airbourne - so much that it cannot be recovered from. It doesn't pull to one side on the ground, like the usual misalligned gear issues.

... the only problem I can think is because the propeller (firespitter) engines are mounted on the wings ...

Has anyone else out there succesfully flown a gullwing? With wing mounted engines?

I haven't tried any gullwings, but I have had trouble with a few firespitter parts in the past that caused a "pulls to one side as soon as it is airborne" issue. Two things ended up making a difference for me...

1. I discovered that some parts caused my CoL to be off-center for unknown reasons. I narrowed this down to specific parts and in the end removed their lift characteristics.

2. Firespitters control surfaces and special lift cases were good potential problems from my perspective when using FAR, so in my install I removed those modules with ModuleManager.

While this might not be your problem at all (I wasn't quite following about your CoL being ahead of your CoM ... but you may have mean Trust vector), and I didn't do sufficient testing of my changes, I can say that my instant rolling condition was fixed when I made the above changes. Perhaps this will give you some clues or ideas to try.

-Talon

[ferram4]

@NathanKell: I guess that one of the transforms is null on load? I can look into trying to fix it, but it's probably not that big of a deal for now.

[Motokid600]

So ive been doing some searching.. FAR+MechJeb. There is no way for MJ to properly manage my throttle? Even with the terminal velocity limiter MJ puts the hammer down and the rocket flips. I haven't discovered this problem until now because all my rockets have had a low TWR.

[AbeS]

You just don't have to limit your throttle with FAR unless you have a TWR bigger than 1.6 on launch (approximately). And reaching terminal velocity, if possible, isn't really the efficient way to do it. The flipping, in most cases is related to bad design, wrong ascent path or excessive TWR at low altitudes.

[ferram4]

Well, even if MJ was limiting the throttle to terminal velocity it would still do that, since terminal velocity is much higher with FAR installed. You'll have to limit the ascent autopilot's acceleration to get the same effect.

[NathanKell]

Ferram: yeah, I just worried since it's evidently not in a try/catch that it might stop the module. But since it obviously doesn't....yeah, no matter.

[Tau137]

Strange thing are happening with the latest update....

1. Very unstable rockets with any air control surfaces on then at about 0.5-2 Mach (weird rotational forces for no apparent reason).

2. Any attempt to aerobrake at Jool with any vessel causes immediate an uncontrollable rotation, even when barely touching the atmosphere at 135km.

[ferram4]

This is happening in v0.12.5.2? Are you sure that your rockets are not simply aerodynamically unstable?

And when you intend to aerobrake a vehicle, you have to design it to be stable during the aerobraking. This sounds more like aerodynamics functioning as intended.