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

[ferram4]

The fuel drain is likely the main cause of that, and the only solution is to either add fins at the bottom of the rocket, redesign the rocket so that the CoM is above the upper-most tank of the first stage, or flare out the bottom of the rocket with boosters to prevent it from flipping.

In addition, remove any sudden changes in the cross-sectional area of the rocket, or put them below the CoM; those will create a lot of drag and make the rocket unstable.

[NathanKell]

Use 1 tank per stage (via Stretchy or Procedural Parts). Then the whole stage will drain at once.

[camlost]

Use 1 tank per stage (via Stretchy or Procedural Parts). Then the whole stage will drain at once.

Is that true in realism?

[NathanKell]

camlost: it's close enough, since in reality the stage would have a fuel and an oxidizer tank, so the combined CoM of both tanks, as they drain, will be decently near the middle of the stage (presumably oxy on top of fuel to keep mass higher in the stage).

[camlost]

If the tank uses LH2 and LO2, its CoM would be far from the center when full in the first place. If it uses kerosene+LOx, it will move from ~1/2 to near ~1/4 then back to 1/2.

This issue is extremely important for space shuttles, since keeping the CoM closer to the top will decrease the need for SSME gimbal range. Hope RF will address this but we can always use two tanks

[NathanKell]

Ah, yeah, it *is* bad for hydrolox. Lemme think on how RF might handle it.

[White Owl]

If it bugs you make two separate tanks, connected together so they look like one tank. That's how my shuttles work. No need to change anything in RF.

[wasmic]

@wasmic: Doing your gravity turn based on altitude markers doesn't make too much sense, since it's your velocity that matters. You should start your turn somewhere between 50 m/s and 100 m/s for TWRs around 1.4 - 1.7, but if you want to keep a TWR of 2 and not throttle down you can try giving it a slight kick right off the pad. If you're still having stability problems, the fairing might actually be the issue; fairings are very low-density, but do add a lot of surface area, so that can help make the rocket unstable; you can try putting whatever service module you have for the payload at the top of the fairing (upside-down, so the heavy engine is at the top) or you can try counteracting it with fins on the first stage.

And most non-wing parts are already FAR compatible, it's only the ones that are very, very different from stock that tend to be a problem. In that case, those need their own FARBasicDragModel Module defined, and the info for that can be found in the README. For wing parts, those need a FARWingAerodynamicModel or FARControllableSurface module, and the documentation for that can also be found in the README.

Thank you I've been having some progress with better gravity turns. I think I'll still have to lower my TWR, though.

[ThorBeorn]

This?

@PART[*]:HAS[@MODULE[ModuleEngines],@RESOURCE[ElectricCharge]]
{
	@RESOURCE[ElectricCharge]
	{
		%isTweakable = false
		%hideFlow = true
	}
}

How does this work? Is it just to copy paste it into a new .cfg and put it in gamedata? Does the "@PART[*]:HAS[@ModuleEngines]..." remove tweakable electric charge for all engines (that have "ModuleEngines")?

[BudgetHedgehog]

How does this work? Is it just to copy paste it into a new .cfg and put it in gamedata? Does the "@PART[*]:HAS[@ModuleEngines]..." remove tweakable electric charge for all engines (that have "ModuleEngines")?

Yes and yes. I've never had any problems with NaN EL or mass since I got it.

[m4ti140]

OK, I did some more testing with FASA, and it gets even worse... Both Mercury and Gemini pods get their CoL calculated in some wierd position (to the side from the CoM) making them reenter side first, without any control (especially Gemini). I don't know how is that even possible, especially that CoM placement is correct. Can someone else who uses FASA with FAR check it?

[Motokid600]

OK, I did some more testing with FASA, and it gets even worse... Both Mercury and Gemini pods get their CoL calculated in some wierd position (to the side from the CoM) making them reenter side first, without any control (especially Gemini). I don't know how is that even possible, especially that CoM placement is correct. Can someone else who uses FASA with FAR check it?

update to the latest version of FAR. Ive yet to try Gemini, but i do know t fixes Mercury.

I myself have an inquiry.. i need tips. MechJeb/FAR tips if you will. Im having a rampant problem of my rockets flipping over after stage separation and stage two ignition. Id say Mj is adding too much input. Because after separation at around 35-40km Mj is still steering the rocket away from prograde in order to follow my trajectory. But it seems no matter what i do to edit the ascent profile the same always happens. So... what does everyone else do in terms of their ascent profile in Mj? I have my Turn Start set at 700m and Turn End i believe its called set to 60km and the pitch rate set to 60%. Which is a little steeper then id like. Im trying to make it so Mj isnt trying to pitch the rocket so harshly by time the first stage burns out.

[Starstrider42]

I myself have an inquiry.. i need tips. MechJeb/FAR tips if you will. Im having a rampant problem of my rockets flipping over after stage separation and stage two ignition. Id say Mj is adding too much input. Because after separation at around 35-40km Mj is still steering the rocket away from prograde in order to follow my trajectory. But it seems no matter what i do to edit the ascent profile the same always happens. So... what does everyone else do in terms of their ascent profile in Mj? I have my Turn Start set at 700m and Turn End i believe its called set to 60km and the pitch rate set to 60%. Which is a little steeper then id like. Im trying to make it so Mj isnt trying to pitch the rocket so harshly by time the first stage burns out.

I've successfully done MechJeb launches with turn start at 200m and the other settings as you described (and I'm pretty sure I stage at 20 km or so). Have you tried toggling "Corrective Steering" while in flight? I've found it tends to work well in the lower atmosphere, but overcorrects in the upper atmosphere.

[m4ti140]

update to the latest version of FAR. Ive yet to try Gemini, but i do know t fixes Mercury.

I myself have an inquiry.. i need tips. MechJeb/FAR tips if you will. Im having a rampant problem of my rockets flipping over after stage separation and stage two ignition. Id say Mj is adding too much input. Because after separation at around 35-40km Mj is still steering the rocket away from prograde in order to follow my trajectory. But it seems no matter what i do to edit the ascent profile the same always happens. So... what does everyone else do in terms of their ascent profile in Mj? I have my Turn Start set at 700m and Turn End i believe its called set to 60km and the pitch rate set to 60%. Which is a little steeper then id like. Im trying to make it so Mj isnt trying to pitch the rocket so harshly by time the first stage burns out.

I _do_have_ the latest version of FAR installed. The Mercury CoL is outside of the pod and Gemini currently behaves like a plane - goes nose first and behaves as if it had wings; the CoL position is nonsense too.

[ferram4]

@m4ti140: Go to the GitHub repository and download the latest versions of FerramAerospaceResearch.dll and ferramGraph.dll from there. You'll also need to go grab the FARAeroStress.cfg from the GameData folder there and put it in the FerramAerospaceResearch folder. The latest dev builds of FAR have the issue fixed, but there's a lot of work to be done before a full release is possible.

[m4ti140]

@m4ti140: Go to the GitHub repository and download the latest versions of FerramAerospaceResearch.dll and ferramGraph.dll from there. You'll also need to go grab the FARAeroStress.cfg from the GameData folder there and put it in the FerramAerospaceResearch folder. The latest dev builds of FAR have the issue fixed, but there's a lot of work to be done before a full release is possible.

OK, turns out I don't have the latest version installed XD. Gonna test that out.

On a side note, since we're at FASA vs realism mods - is it just my install, or FASA parts don't get heated by DRE?

[Pikachu8091]

Heyo, I'm not very avid with FAR, but I downloaded it for .22, and it had a flight computer which could connect to Mission Control or a kerbal-made comm-satellite array. I did not find that in 23.5. Was it removed or have I done something wrong?

[Motokid600]

I've successfully done MechJeb launches with turn start at 200m and the other settings as you described (and I'm pretty sure I stage at 20 km or so). Have you tried toggling "Corrective Steering" while in flight? I've found it tends to work well in the lower atmosphere, but overcorrects in the upper atmosphere.

I believe I do indeed have corrective steering toggled. Ill try playing with it, thanks.

[NavyFish]

@ferram4: Hello, me again. I'm still having the error where the editor analysis will not plot anything. As recommended, I created a .cfg file in GameData with the following text:

@PART[*]:HAS[@MODULE[ModuleEngines],@RESOURCE[ElectricCharge]]
{
	@RESOURCE[ElectricCharge]
	{
		%isTweakable = false
		%hideFlow = true
	}
}

Like last time, the first FAR Error seems to occur when it encounters "winglet3", Aerodynamic force = NaN. This error then propogates forward.

I've uploaded an output_log.txt here: http://www74.zippyshare.com/v/99753960/file.html

The error occurs at line 123219 in the file.

Please let me know what further information I can provide!

Thanks,

-Navy

[NathanKell]

Pikachu8091: You're thinking of RemoteTech.

[ferram4]

@NavyFish: That's not the same exact problem, since all the forces coming out of that shouldn't matter; the NaNs are set to zero when the code finishes to make sure nothing breaks horribly.

It looks like the error starts from some divide by zero in the aerodynamic center calculation, which I believe I fixed for FAR v0.13.1. Are you running the latest version of FAR?

[NavyFish]

I am indeed using 13.1, with FerramAerospaceResearch.dll having a date modified of 4/11/2014 : 11:24 PM and ferramGraph.dll on 2/18/2014 : 5:47 PM

[PLB]

There should be effects on surfaces from engine exhaust. That's a lot of modeling and temperature calculating, but it may have significant effects on certain designs.

[ferram4]

@NavyFish: Hmm... can you provide the craft file so I can reproduce the issue? I'm not sure what's causing the problem right now.

@PLB: I actually do have some correlations on hand to calculate how exhaust would affect control surfaces, but it's not a huge priority to add those effects; in fact, there are far more important induced velocity effects (mostly from wings) that I'd like to implement first. But yes, it is something that's on the table, if not right now anyway.

[NavyFish]

Here you go: http://www38.zippyshare.com/v/17145205/file.html

Please note, I'm using B9 with the community fix for .23.5, which can be found here: http://forum.kerbalspaceprogram.com/threads/66020-B9-0-23-fixes?p=907484&viewfull=1#post907484

Thanks for looking into this!