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

[ferram4]

Well, if the engine wasn't contained in a cargo bay, there are still forces acting on it. And FAR's aerodynamic failures don't account for things that interface with the stock drag system, like parachutes or B9's overpowered airbrakes.

[smunisto]

I tried reentering with my craft, and a couple funny things happened.

Since I don't know which mods are causing it, I posted in the respective threads for all three suspects:

FAR, DRE and TAC Fuel balancer.

You can see my posts here:

http://forum.kerbalspaceprogram.com/threads/25823-0-23-0-23-5-TAC-Fuel-Balancer-v2-3-22Dec?p=1124688&viewfull=1#post1124688

and here:

http://forum.kerbalspaceprogram.com/threads/54954-0-23-5-Deadly-Reentry-Continued-v4-6-4-7-14?p=1124695&viewfull=1#post1124695

So the issues:

1. The stock RAPIER engines just exploded when I tried manually switching from Closed Cycle to Air Breathing(the first two RAPIER entries in the log code below).

2. During reentry the rest of the RAPIERs just exploded for no apparent reason.

I can guess that the culprit is not FAR, since the log says engines were destroyed due to overheating, but who knows. There is this weird "dT" line around the time of destruction for each RAPIER.

See for yourself:

[LOG 22:02:26.315] dT is NaN! tA: 3.16733417659998, E: 0, M: 0, T: NaN
[LOG 22:02:41.177] Tac.FuelBalanceController[FFFA1DA6][337.14]: Rebuilding resource lists.
[LOG 22:02:41.190] Prandlt-Meyer Expansion Curves Initialized
[LOG 22:03:59.903] dT is NaN! tA: 3.28800155222416, E: 0, M: 0, T: NaN
[LOG 22:03:59.960] [00:41:15]: R.A.P.I.E.R. Engine exploded due to overheating.
[LOG 22:03:59.961] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:03:59.964] [RAPIER]: Deactivated
[LOG 22:03:59.967] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:03:59.968] ScienceAlert, Done
[LOG 22:04:00.030] 1 explosions created.
[LOG 22:04:00.047] Tac.FuelBalanceController[FFFA1DA6][376.78]: Rebuilding resource lists.
[LOG 22:04:12.273] dT is NaN! tA: 3.30267629027367, E: 0, M: 0, T: NaN
[LOG 22:04:12.385] [00:41:21]: R.A.P.I.E.R. Engine exploded due to overheating.
[LOG 22:04:12.386] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:04:12.387] [RAPIER]: Deactivated
[LOG 22:04:12.388] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:04:12.390] ScienceAlert, Done
[LOG 22:04:12.449] 1 explosions created.
[LOG 22:04:12.465] Tac.FuelBalanceController[FFFA1DA6][382.74]: Rebuilding resource lists.
[LOG 22:05:40.196] [00:42:14]: R.A.P.I.E.R. Engine exploded due to overheating.
[LOG 22:05:40.197] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.197] [RAPIER]: Deactivated
[LOG 22:05:40.199] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.200] ScienceAlert, Done
[LOG 22:05:40.216] [Explosion] Combined.
[LOG 22:05:40.216] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.217] [RAPIER]: Deactivated
[LOG 22:05:40.219] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.220] ScienceAlert, Done
[LOG 22:05:40.235] [Explosion] Combined.
[LOG 22:05:40.236] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.237] [RAPIER]: Deactivated
[LOG 22:05:40.239] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.240] ScienceAlert, Done
[LOG 22:05:40.255] [Explosion] Combined.
[LOG 22:05:40.255] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.256] [RAPIER]: Deactivated
[LOG 22:05:40.258] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.259] ScienceAlert, Done
[LOG 22:05:40.276] [Explosion] Combined.
[LOG 22:05:40.276] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.277] [RAPIER]: Deactivated
[LOG 22:05:40.279] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.280] ScienceAlert, Done
[LOG 22:05:40.296] RAPIER Exploded!! - blast awesomeness: 0.5
[LOG 22:05:40.297] [RAPIER]: Deactivated
[LOG 22:05:40.299] ScienceAlert, Vessel was modified; refreshing observer caches...
[LOG 22:05:40.300] ScienceAlert, Done
[LOG 22:05:40.381] 2 explosions created.
[LOG 22:05:40.425] Tac.FuelBalanceController[FFFA1DA6][436.26]: Rebuilding resource lists.
[LOG 22:09:03.848] Active Vessel is in atmosphere. Cannot save.

[Klingon Admiral]

@ ferram4

The bug occurs whenever I dock my craft with my space station in orbit, which uses a few parts from KW rocketry and talisar's habitat pack. If the same pod does not dock with the station, it shows normal re-entry behaviour. As docking with another stock-only vessel does not trigger this bug, I suspect it's a mod conflict. Sof, were you using talisars habitat modules on your craft?

[Zeroignite]

So some of my longer, bendier rockets are tricky to keep prograde, and having to microcontrol every launch gets tedious after a while...

Is using MJ ascent autopilot, set to start turn 100m off the pad, shape parameter ~45 pretty reasonable, assuming the rocket has a good thrust profile? Seems important to get the turn going pretty soon before you have vertical speed to try and overcome, and lessened drag for pointy-on-top rockets makes a shallower ascent work fine. So far I'm spending ~3.1-3.3km/s to get into orbit --- reasonable?

[Mystique]

So some of my longer, bendier rockets are tricky to keep prograde, and having to microcontrol every launch gets tedious after a while...

Is using MJ ascent autopilot, set to start turn 100m off the pad, shape parameter ~45 pretty reasonable, assuming the rocket has a good thrust profile? Seems important to get the turn going pretty soon before you have vertical speed to try and overcome, and lessened drag for pointy-on-top rockets makes a shallower ascent work fine. So far I'm spending ~3.1-3.3km/s to get into orbit --- reasonable?

I've spent about this delta-v before last FAR update, now I suddenly needed about 4000 for very simply pointy rocket (payload covered by fairings). I also found it difficult to start gravity turn as early as before since rocket started to flip over.

[Tiron]

Well, if the engine wasn't contained in a cargo bay, there are still forces acting on it. And FAR's aerodynamic failures don't account for things that interface with the stock drag system, like parachutes or B9's overpowered airbrakes.

Well every time I tried to use control surfaces as airbrakes they looked stupid and did essentially nothing.

[ferram4]

@smunisto: That's either an old DR that you're using (ModuleEnginesFX overheating bug) or you're using something like Interstellar that requires pre-cooling high velocity air.

@Klingon Admiral: Oh. That's an old bug from FAR v0.13. It was fixed in v0.13.1. This is why you should always update your mods.

@Zeroignite: That sounds like a pretty optimal ascent to me.

[dlrk]

I tend to find issues with everything, but this is working fine for me.

[Aedile]

@dlrk: No, it will not work with Module Manager 1.5.7; it requires the new features from 2.0.3.

@Mystique: Very light object, decent surface area, FAR not designed to handle very low speed aerodynamics = things are weird there.

There is indeed issue with 2.0.3

[BudgetHedgehog]

Ferram, you should update your download to include 2.0.5.

[NathanKell]

smunist: *complete* modlist please.

[Aedile]

I tried reentering with my craft, and a couple funny things happened.

Since I don't know which mods are causing it, I posted in the respective threads for all three suspects:

FAR, DRE and TAC Fuel balancer.

Are you using interstellar by any chance?

Edited April 28, 2014 by Aedile

[DaMichel]

@DaMichel: IAS doesn't account for compressibility effects, and becomes incredibly inaccurate over Mach 0.6. That's supposed to happen, that's why no supersonic planes use IAS, they use Mach or EAS.

Oh okay. I read some stuff on wikipedia now and i think i understand.

Still, speed = 0 happens from time to time. I have the impression that it happens when i land with too high vertical impact speed. 5 - 10 m/s is not uncommon for me That doesn't seem to make much sense tough.

[smunisto]

Yeah, I am using Interstellar. DRE is the latest version, Ferram.

Apparently, there is something I missed about Interstellar. So I need to use precoolers for my intake air?

Sorry for hijacking the thread, if someone wants to advise me - please do so on P.M.

The RAPIERs are the stock ones btw. But I don't have any precoolers on my SSTO

[ferram4]

@ObsessedWithKSP: Will be in the next release, which should be out soon.

@DaMichel: I've noticed that myself. I'll need to figure out what causes that, though it's probably just that it's grabbing the wrong velocity somehow.

@smunisto: High speed air has lots of energy. When you slow it down, that energy has to go somewhere, usually into heat. At high enough Mach numbers (>3) heating is significant enough that the intake air needs to be cooled down or else the combustion chamber risks being overheated by high-temperature, high-pressure gas. Interstellar models this and changes one of the engine bodies into a precooler.

[ferram4]

Alright, since Module Manager 2.0.5 is out to fix a serious bug, I've released FAR version 0.13.2.1, which includes the fixed Module Manager (note: old Module Manager must be deleted or issues will occur), as well as fixing a few minor issues. Also, it includes a new SSTO using B9 parts, the Eclipse III:

It includes some features that are useful in designing spaceplanes, such as slight anhedral on the wings to reduce wing rock during at high angles of attack and a wedge tail to produce more yaw stability at high Mach numbers.

[FenrirWolf]

Assuming I don't have B9, there's isn't gonna be a dependency issue so long as I never bother trying to fly that craft right?

[Tiron]

Assuming I don't have B9, there's isn't gonna be a dependency issue so long as I never bother trying to fly that craft right?

If you go to the craft load dialog in the SPH on a save with stock craft enabled, it'll be greyed out with a notification that it has invalid/not unlocked parts, and won't even let you TRY to load it. It'll spam up the console with a list of the missing parts. Other than that, you shouldn't notice a thing.

And Anhedral reduces that wing rocking at high AoA? ...*goes to flip the wings on his planes* >.>

[jstnj]

Ferram: Is the FPS drop I have during Kerbin atmosphere escape (~2.5k-10k meters) due to the air vapor animation on screen...or the physics you put under the hood? It KILLS my framerate.

Thanks!

[ferram4]

@FenrirWolf: It's a craft file. KSP isn't going to freak out because you have a craft file that points to parts that you don't have.

@Tiron: Well, wing sweep contributes to the dihedral effect (due to more swept wings having lower lift slopes than less swept wings). At really high angles of attack, wing sweep is the dominant component of the dihedral effect. Too much dihedral effect can cause the plane to roll violently in response to slight sideslip, and if it rolls enough that angle of attack and sideslip start being exchanged, the dihedral effect overpowers any roll damping the plane might have as well as not giving the vertical tail a chance to get rid of yaw inputs. A slight amount of anhedral can make the dihedral effect less pronounced, resulting in better lateral stability at high angles of attack. Of course, it's less stable at low angles of attack as a consequence, but some sub-optimal performance at low angles of attack is acceptable when you're primarily concerned about keeping the thing from losing control during reentry and when climbing out of the atmosphere.

@jstnj: Dunno. I get lower FPS when the graphical aerodynamic effects show up, and then it speeds up when they're gone. If you're not getting an FPS drop in the upper atmosphere, it's not my fault, because you're still running expensive supersonic calculations up there.

[jstnj]

@jstnj: Dunno. I get lower FPS when the graphical aerodynamic effects show up, and then it speeds up when they're gone. If you're not getting an FPS drop in the upper atmosphere, it's not my fault, because you're still running expensive supersonic calculations up there.

Yeah it must be the graphic fx...is there a part of the cfg can I tweak to decrease the fx amount? Thanks!

[ferram4]

Check the settings menu for the AerodynamicFX slider and drop it down.

[Tiron]

@Tiron: Well, wing sweep contributes to the dihedral effect (due to more swept wings having lower lift slopes than less swept wings). At really high angles of attack, wing sweep is the dominant component of the dihedral effect. Too much dihedral effect can cause the plane to roll violently in response to slight sideslip, and if it rolls enough that angle of attack and sideslip start being exchanged, the dihedral effect overpowers any roll damping the plane might have as well as not giving the vertical tail a chance to get rid of yaw inputs. A slight amount of anhedral can make the dihedral effect less pronounced, resulting in better lateral stability at high angles of attack. Of course, it's less stable at low angles of attack as a consequence, but some sub-optimal performance at low angles of attack is acceptable when you're primarily concerned about keeping the thing from losing control during reentry and when climbing out of the atmosphere.

At the moment, I've only got three of my planes updated to the current version, and they're all variants of the same design. They're a mix of different sets of mod parts (B9 Fuselages, TVPP NTBI wings and control surfaces, stock and TVPP resized stock winglets and rudders, multiwheels landing gear, and aviation lights just for fun), with the same basic planform as my old, stock Ravenspear Mk3 derivatives(with one slight exception.)

This is the SSTO version:

It uses SABRE-S intakes and SABRE-S engines from B9. There's also a plane version of that one without all the orbit-specific stuff (Reaction Wheel, RCS, Monoprop tanks, Solar Panels, and some of the navlights) which is a tiny bit shorter and somewhat lighter (especially with the tanks not filled, which they don't need to be anywhere near for any reasonable flight plan.) The plane version uses stock Turbojets and TVPP cone intakes.

There's also an experimental derivative with TVPP ramjets, which has the tail replaced with a bicoupler with a pair of B9 turbojets, larger canards, and the wings moved all the way back (making it a tailless, slightly swept delta.)

All three have one tick of dihedral on the outer wings. All three do a lot of sideslipping and rolling when in a hypersonic cruise at altitude. I had no idea the dihedral was making it worse.

Edited April 29, 2014 by Tiron

[ferram4]

It's probably more the lack of a strong vertical tail. You probably want to copy the wedge tail more than the anhedral for this case. You'd probably be fine with no dihedral or anhedral on this, the sweep should be enough to make it work.

[Kalista]

Ferram question for you. Will reverting back to MM 1.5.3 cause any issues with the latest far ? Newest one completely broke another mod of mine that I rely on and it worked perfectly fine with 153 so wondering if far ( another mod I wont play without) will be fine using it.