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


ferram4

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I was testing FASA Titan ICBM with FAR today, and I discovered something bizarre: First of all, even after making sure the warheads are shielded by nosecone/heatshield, the reentry vechicle couldn't keep attitude during reentry - it always flipped over and reentered backwards, base first (which would effectively destroy the missile if I was using DR). That is of course bull****, bc when reentering with a cone, especially at hypersonic speeds, both nose-first and base-first attitudes should be stable (that's why NASA worried during Project Mercury about spacecraft being caught in nose-first attitude during reentry, bc once it gets hot, it's so stable that it's impossible to orient heatshield-first anymore). Also the drag was ridiculously low - it may have been due to heavy payload, but even though it descended in least streamline attitude, it still hit the ground at Mach 1.1

Then I tried to keep it stable by keeping the last stage (tank + engine) attached at entry. Before I added 'fairing' to nosecone title it, ekhm, pushed the lifting body code to its limits. The drag of warhead plate caused it to reenter at something arround 80*AoA. Once it went subsonic, it violently pitched up and went upwards... gaining arround 1500m of altitude before it started falling. It hit the ground at arround 100m/s. After fixing nosecone to shield warheads inside I finally got stable descent... but at ludicrous speed. The missile hit the ground at 812m/s...

Something doesn't exactly work as expected here... I thought lifting bodies got nerfed?

EDIT: Playing arround with CoM (ie. moving them in each part.cfg to where they belong using CoMOffset, instead of the surface, where they were by deffault. Also changing fairing mass to something reasonable for the material it was made of) fixed the problem of reentering backwards, it still hits the ground at ludicrous speed with the full load of warheads - though judging by the masses and aerodynamics, it's probably correct XD

Edited by m4ti140
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Also the drag was ridiculously low - it may have been due to heavy payload, but even though it descended in least streamline attitude, it still hit the ground at Mach 1.1

I experienced something similar. I am using a lot of mods, including DR. When i launch, everything is normal (i do however also experience my rockets flipping around sometimes), but when is reënter kerbins atmosphere, it seems like there is no atmosphere at all. It just keeps accellerating untill i hit the ground of burn up.

I realy hope someone can tell me if there is a fix for this, of if i have to change some settings.

Thanks in advance

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@Erethron: They technically should, but are called interstages and not fairings, so FAR doesn't detect them. Either change the part title to include "fairing" or change the config.xml to include "interstage" in the fairing search.

Ah, that explains it. Thanks for clearing that one up!

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I experienced something similar. I am using a lot of mods, including DR. When i launch, everything is normal (i do however also experience my rockets flipping around sometimes), but when is reënter kerbins atmosphere, it seems like there is no atmosphere at all. It just keeps accellerating untill i hit the ground of burn up.

I realy hope someone can tell me if there is a fix for this, of if i have to change some settings.

Thanks in advance

I've also been seeing this with my mk1-2 pods heatshield in the deadly reentry pack completely ignoring drag at all ( I also have one of the S2 3m Bays between my pod and heatshield as well ). Acts like theres no atmosphere until the shield burns off then the pod suddenly slows like normal. https://drive.google.com/file/d/0BwYzqg0314S0eHRMc1hDcVBwZEE/edit?usp=sharing output log from after it happend

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So it is my understanding that node size affects amount of drag. When we are resizing parts, is there a rough guide we can follow for what diameter should correlate to what node size?

For normal KSP: divide diameter by 1.25, round normally (except: precisely 0.625m = size 0)

For RO: divide diameter by 1, round normally (except: precisely 0.5m = size 0)

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@m4ti140: The warhead CoM is about half the way down the length of the cone, and you sent it in spinning like a top, right? MIRVs are intended to smack the ground (on Earth anyway) at about Mach 4 or so, and make quite a bit of heat on entry (see time-lapse photo). Technically the nosecone on that only exists to protect the warheads on the way up; each should come down independently, but it doesn't sound like that's what you're doing here.

@photas: What are you reentering with? A payload chock-full of fuel, or a standard command pod? The density of the vehicle matters a lot. Also, what mod you're using matters since they might not be set up for compatibility properly.

@Kalista: I'm not seeing any errors in the log, could you post a picture of the problem-craft?

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@Kalista: I'm not seeing any errors in the log, could you post a picture of the problem-craft?

Whole Rocket

http://cloud-4.steampowered.com/ugc/579018555229753184/E24A8CCE31C3CB719167B261A93AE6846A94F20C/

Just the CM

http://cloud-3.steampowered.com/ugc/579018555229755518/08936661B49FA343B6ED81FA02A63995F5D63F57/

One thing to note as well. Just loaded up the save and Deorbited my Craft to try to catch it on fraps only thing diff than my first attempt is the brand new version of mechjeb that came out ( was using sabrins patch) and this time it reentered correctly. First attempt noticed that the CD and CM lines in the context menu were at 0 while CL was barely over that second attempt thing went as it was expected to so wondering if that was the ultimate cause of it.

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Try launching it again to see if the craft loading in orbit caused things to work correctly. I suspect that the heat shield just barely managed to be "shielded" by the bay, and if that's the case then I might have a weird transform error somewhere or I need to add some more margin-sort-of things to see if I can make sure that nothing bad happens again. Yay edge cases.

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I checked the last few pages and didn't see anything about it, but I'm having a problem where the tweakables menus for defining what lift surfaces can act as what (yaw etc.) don't save, even when immediately launching. The same thing happens with control amounts. Using the .13 public build with .23.5

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Try launching it again to see if the craft loading in orbit caused things to work correctly. I suspect that the heat shield just barely managed to be "shielded" by the bay, and if that's the case then I might have a weird transform error somewhere or I need to add some more margin-sort-of things to see if I can make sure that nothing bad happens again. Yay edge cases.

Copied craft from my career save into sandbox and fired it sub orbital to 100km. Came back into the atmosphere as it should no wobble no funky aerodynamic bugs only difference still from when it bugged out and now was switching from the hotfixed mechjeb to the new version ram0n put out so thinking that was the cause of my issue.

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@photas: What are you reentering with? A payload chock-full of fuel, or a standard command pod? The density of the vehicle matters a lot. Also, what mod you're using matters since they might not be set up for compatibility properly.

I was deorbiting a satellite, way less mass than the standard command pod. I also checked if the standard command pod would act different, but it too would just keep accellerating.

I am using a LOT of mods, so it's probably one of them that's uncompatible with Ferram Aerospace. Some of them are not updated for 0.23.5, so maybe when all of them are updated, the problem goes away.

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@Jaxx: Using stock parts or mod parts? What other mods are you running? I haven't seen this in my save, so I'm assuming a mod conflict somewhere.

I had this happen when I was trying to get the KSO shuttle mod to work with FAR. It was because the stock axis settings were overriding the FAR axis settings, and the FAR MM config wasn't catching the part because the FARControllableSurface module wasn't added yet. Solved it by explicitly removing the ModuleControlSurface from the part in my MM config. You might want to change the section that removes the ModuleControlSurface so it has the :Final tag at the end. i.e:


@PART[*]:HAS[@MODULE[ModuleControlSurface],@MODULE[FARControllableSurface]]:Final
{
!MODULE[ModuleControlSurface]{}
}

Haven't tested that, but it should rule out that edge case.

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Oh that was terrifying, a mod that let me toggle engine fairings broke FAR and let me experience the stock drag model. How did I ever, ever manage to fly rockets in that soup.

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Oh that was terrifying, a mod that let me toggle engine fairings broke FAR and let me experience the stock drag model. How did I ever, ever manage to fly rockets in that soup.

I was just about to report that too. It should be the same issue that I already reported where an engine had the ModuleJettision for fairings but didn't have any in the model. Hopefully it will be fixed in the next version.

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Just recreated my bug. Launched 2 of the rockets I showed earlier for docking. After undocking had one rocket reenter and then everything went haywire with the capsule ignoring the aerodynamic model entirely.

output log

https://drive.google.com/file/d/0BwYzqg0314S0UE9ZTmhRdE5XbGM/edit?usp=sharing

Video

https://www.youtube.com/watch?v=xI3f8hxyXtM&feature=youtu.be

might still be processing when viewed

Craft trying to pitch up then roll was my doing attempting to get somethin to catch air to slow it down explosion at the end was due to me ditching the heatshield as a last ditch effort to slow down

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@Jaxx: Using stock parts or mod parts? What other mods are you running? I haven't seen this in my save, so I'm assuming a mod conflict somewhere.

It was entirely me being a dingus. Mod Manager was duplicated in Kerb Paint ( why people still include it in downloads, I don't know ) and just deleting it cleared the issue. Working fine now!

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@Kalista: Okay, so it's not sending the proper drag update event. I'll look into it; does it require docking and un-docking to cause the issue, or can it be caused without docking at all?

@Einarr: Ouch, a nullspace bug. The problem is that FAR is set up so that anything it can do that could possibly cause a nullspace bug causes it to stop and then print to the log (those are all the FAR Aerodynamic Error messages in there). I think that Firespitter might have needed an update for 0.23.5 compatibility, and you didn't specify that you updated that for 0.23.5 compatibility, so could you make sure that that isn't the issue? Does removing KAS fix the issue?

@Jaxx: It's distributed because ModuleManager is necessary for many of these mods to function. FWIW, I don't know if Kerb Paint is up-to-date, so you might still end up having issues with it.

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@Kalista: Okay, so it's not sending the proper drag update event. I'll look into it; does it require docking and un-docking to cause the issue, or can it be caused without docking at all?

6 Attempts only time it bugs out is on dock/undock just going up and coming back works fine.

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@Einarr: Okay, so something must be slipping by. See if you can recreate it with the fewest parts possible, and with only the active vessel loaded (so no debris within 2.5km) so that nothing else can interfere. I hope it's not some stupid floating-point-caused thing.

@Yarbrough08: Well, you'd need to do a bunch of simulations of the rocket during ascent, varying control inputs and such. This is one of those situations where there's no simple formula to use, unfortunately.

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Well, after reinstalling FAR and removing KAS, I can now load the craft onto the runway with out the issue I was mentioning... What a shame... I also hope the FAR extension for MechJeb gets updated soon as well, since now MJ can't seem to figure out how to keep a spaceplane steady...

Edited by Einarr
Added spaces where there should have been some...
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