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

ferram4

By ferram4
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ferram4

ferram4

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It sets the exposed area for parts because that allows it to never need to consult the stock aero code ever. It's also more accurate. However, since the really nasty exacerbation was caused by the exposed area being too small for not-completely shielded parts, I set the lower bound to be whatever the stock game would calculate.

At this point, the only thing "exacerbating" the issue is stock. FAR's code will either reduce the heating issues to that of stock or make them more stable. There is absolutely nothing I can do about someone else's code.

Jesus, it's the win64 nightmare all over again with this one.

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Rithaniel

Rithaniel

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Hi. I'm having a slight issue which I believe to be originating in FAR. I've been building a massive orbital station part-by-part recently, and currently I'm sending up the heaviest/longest part, so I have an extremely large/tall ship to get into orbit. I have the important chunk stowed away in a 5m KW fairing, and have ensured that my center of lift is securely below my centers of mass/dry mass. Yet when I launch, if I try to enact a gravity turn where I turn my inclination more than 5° anywhere below 20-25km, my ship flips out every single time, no matter how powerful I make my gyroscopes or RCS blocks. This is fairly detrimental as, due to it's size, it will explode spectacularly if it flips. After turning on aerodynamic overlays, it seems that the fairing is acting like a colossal elevon tilting the entire ship into the direction it is already moving. Drag forces from the body of the ship (now flying sideways) come into play shortly thereafter, forcing it to spin even more. I've had this issue before, but have always been able to overcome it, but, due to the scale of this launch, it has not been possible this time.

I have currently rage quit after approximately 6 hours of repeated attempts at this launch, but was simply wondering if this could be my build, my flight skills, or FAR to blame. If it is FAR, what can I do to fix the issue?

(Also, my computer is old and was cheap even when it had been freshly bought. Thus, this computer is not designed to play KSP, and my install runs extremely slowly. One minute of in-game time with such a massive ship in the lower atmosphere, takes more than 15 minutes of RL time. I believe this has no bearing on the matter, but I'm just sharing my pain.)

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tetryds

tetryds

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@Hammer Head: "COL being under COM" is not enough, and that is also only for subsonic.

Set the right speed and altitude parameters and run a derivative test, watch your Mw.

When supersonic, the body generates a lot of lift, and the tip a lot of drag, if you are longer it gets harder to stay straight.

Other things that can help are either starting your gravity turn later or going slower, or both.

Every rocket works better with a different ascent profile.

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blowfish

blowfish

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Hi. I'm having a slight issue which I believe to be originating in FAR. I've been building a massive orbital station part-by-part recently, and currently I'm sending up the heaviest/longest part, so I have an extremely large/tall ship to get into orbit. I have the important chunk stowed away in a 5m KW fairing, and have ensured that my center of lift is securely below my centers of mass/dry mass. Yet when I launch, if I try to enact a gravity turn where I turn my inclination more than 5° anywhere below 20-25km, my ship flips out every single time, no matter how powerful I make my gyroscopes or RCS blocks. This is fairly detrimental as, due to it's size, it will explode spectacularly if it flips. After turning on aerodynamic overlays, it seems that the fairing is acting like a colossal elevon tilting the entire ship into the direction it is already moving. Drag forces from the body of the ship (now flying sideways) come into play shortly thereafter, forcing it to spin even more. I've had this issue before, but have always been able to overcome it, but, due to the scale of this launch, it has not been possible this time.

I have currently rage quit after approximately 6 hours of repeated attempts at this launch, but was simply wondering if this could be my build, my flight skills, or FAR to blame. If it is FAR, what can I do to fix the issue?

(Also, my computer is old and was cheap even when it had been freshly bought. Thus, this computer is not designed to play KSP, and my install runs extremely slowly. One minute of in-game time with such a massive ship in the lower atmosphere, takes more than 15 minutes of RL time. I believe this has no bearing on the matter, but I'm just sharing my pain.)

Nothing surprising here - rockets are naturally unstable. You shouldn't really need to be more than 5 degrees from prograde at any time - start your turn early (maybe 1-2km) and keep it gradual. For added stability, put some fins on the end of the rocket - this will allow you to deviate a bit more from prograde without flipping out. Finally, note that the CoL indicator is meaningless in FAR. If you want to know pitch stability, open the static analysis, run it for a particular mach number, and look at the slope of the Cm line - if it's negative, you're stable, if it's positive, you're unstable.

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eddiew

eddiew

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It sets the exposed area for parts because that allows it to never need to consult the stock aero code ever. It's also more accurate. However, since the really nasty exacerbation was caused by the exposed area being too small for not-completely shielded parts, I set the lower bound to be whatever the stock game would calculate.

At this point, the only thing "exacerbating" the issue is stock. FAR's code will either reduce the heating issues to that of stock or make them more stable. There is absolutely nothing I can do about someone else's code.

Jesus, it's the win64 nightmare all over again with this one.

That is however a really good and clear explanation - and I think people are definitely starting to realise that stock has some 'game breaking' heating bugs that aren't your fault :)

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Kobymaru

Kobymaru

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Alright, so it's my flight skills. Thanks for the advice, guys. I'll give it another go in about a day or so.

A little hint: look at (archery-) arrows. Where's the heavy part, and where's the part that makes the most drag?

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eddiew

eddiew

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Alright, so it's my flight skills. Thanks for the advice, guys. I'll give it another go in about a day or so.

In many cases, you can put the rocket at a small incline when it's in the VAB (assuming the launch stabilisers), which immediately starts your gravity turn the moment you hit the engines. Saves a lot of wobbling around trying to get the right heading without inducing flippage ^^

vTwPY7u.jpg

Most of my rockets start like this, go up with SAS on until about 150m/s, then turn SAS off until the upper atmosphere. Having aerodynamics do the work for you is much more efficient than constantly fighting against it with manual piloting. Only thing is watch your TWR and keep on the throttle control. I find that 1.6-1.8 is usually good for an efficient ride to orbit.

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damerell

damerell

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Alright, so it's my flight skills. Thanks for the advice, guys. I'll give it another go in about a day or so.

As far as possible you want to lean a _very_ little just off the pad (or even on it, as below) and then keep your hands off the controls thereafter until the atmosphere is so thin that dynamic pressure is dropping again. The initial lean will naturally be amplified as you ascend.

In many cases, you can put the rocket at a small incline when it's in the VAB (assuming the launch stabilisers), which immediately starts your gravity turn the moment you hit the engines. Saves a lot of wobbling around trying to get the right heading without inducing flippage

Crikey, that looks alarming, although I daresay it works. I tend to program in a little lean to MechJeb before lighting the engines, then switch rapidly to surface prograde then controls off (or KILL ROT if you develop a spin). Lately I've been experimenting with ever so slightly reducing the thrust setting on the eastward SRB.

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Rithaniel

Rithaniel

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As far as possible you want to lean a _very_ little just off the pad (or even on it, as below) and then keep your hands off the controls thereafter until the atmosphere is so thin that dynamic pressure is dropping again. The initial lean will naturally be amplified as you ascend.

I've attempted this method before, but it has been amplified far too quickly in my experience, often ending up 100% horizontal before 20km.

As for TWR, I'm actually starting this ship with solid rocket boosters, and I have them set to 1.23 TWR, to ensure I don't reach supersonic speeds until I'm above 6km.

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ferram4

ferram4

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Only SRBs, or SRBs augmenting a liquid core? If it's only SRBs, the complete lack of thrust vectoring is your problem; you'll need to either add some type of liquid engine that has thrust vectoring or add lots of control surfaces so you actually have some degree of control. Reaction wheels will not cut it unless you add a ton of them.

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tetryds

tetryds

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Would it even be possible to program a switch that toggles between FAR and the stock model for specific craft?

No, but why would you want to do that?

I find it much easier to have two installs, that also helps preventing that things get messed up.

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Maars

Maars

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hi ferram, i just wanted to submit a log report. it's tiny as i've isolated the game to pure stock v1.4 with only FAR and modular flight integrator. it seems to be throwing a null exception. i tested as a result of my heavily modded career game being compromised by a 60meg log file, in other words a giant null reference farm, crashes and poor performance

would you be so kind as to have a quick gander?

https://www.dropbox.com/s/y5zoveu3sc0s39m/Player.log?dl=0

in case you do have a look - thank you!, in case you don't - Thank you anyway for a great fundamental mod to ksp!

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Maars

Maars

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agico

@Maars: do you have reproduction steps and a specific craft file where this happens?

That helps a lot.

Hi Tetryds, Here's my issue : I have a linux mint ksp 1.4 which is very heavily modded and KCT kept throwing errors. After submitting to Magico, he commented on needing 2.4 gig just to open the 60meg log file because it was throwing a farm of null exceptions due to either DRE, FAR or Scansat. After isolating all three mods on a clean stock install, I noticed it's FAR. The log file provided is from the space centre view with a freshly started career save - no crafts, nothing. i don't get it, i have the latest FAR and modular integrator

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Maars

Maars

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Do you mean the lone ChuteCalculation exception? Yeah, that's known and fixed in the dev build. Otherwise, I don't see anything out of the ordinary in there at all...

see, this is what happens when you don't know anything and bother people with it. Sorry for the hassle, it seems i have multiple problems with my save and ignorantly thought it was FAR's doing. carry on :)

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cantab

cantab

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Ugh. Any pointers for fixing craft that seem to break FAR? In the SPH I get an IndexOutOfRangeException and a NullReferenceException when trying to use the static analysis or stability derivatives and no results there. In flight I don't seem to get any lift at all.

EDIT: Update. Reproduced in a clean 1.0.4 install with FAR 0.15.4.1 installed. .craft file and Player.log http://1drv.ms/1KgdUqa

Edited by cantab
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