[0.90]NEAR: A Simpler Aerodynamics Model v1.3.1 12/16/14

[TheReaper]

Hi,

I just installed this mod because I find FAR too complicated for me and so far I love it But I have encountered one situation and I would like to ask if this is normal behavior of this mod - I build small jet using Spaceplane Plus parts with 2 turbojets and its a bit too fast, right after take off it will reach approx. 780ms on sea level and without any difficulties it can make 75km suborbital hop just with these two turbojets!! It seems to me that spaceplane will be too easy with this behavior. Is it normal?

http://i.imgur.com/pSUmHPC.jpg

extreme speeds with far was something i was hearing about but 780 m/s? damn that i never heared of, not this much

[Renegrade]

I just installed this mod because I find FAR too complicated for me and so far I love it But I have encountered one situation and I would like to ask if this is normal behavior of this mod - I build small jet using Spaceplane Plus parts with 2 turbojets and its a bit too fast, right after take off it will reach approx. 780ms on sea level and without any difficulties it can make 75km suborbital hop just with these two turbojets!! It seems to me that spaceplane will be too easy with this behavior. Is it normal?

That looks like Spaceplane Plus, which as of version 1.3 supports NEAR supposedly. Is that 1.3? It seems to use ModuleManager config files; do you have MM installed too?

Without FAR/NEAR support, any engine designed around stock atmosphere will be way overpowered...

[Olterin]

As far as I can tell, Spaceplane Plus does not alter stock engines at all - you would be getting a similar result with a plane of similar weight and aerodynamical properties with just stock parts.

[Vexel]

Similarly to the above, I'm getting ridiculous speeds using stock turbojets now. In fact, I can go fast enough with nearly all my craft that I get reentry effects at around 8km. Is this a result of FAR conflicting with another mod?

EDIT: Turns out that the B9 parts I was using have 0 drag at all.

Edited July 20, 2014 by Vexel

[Palec]

I did a test and again used two turbojets, but this time I build plane from stock parts. As you can see, with same scenario, plane reached 500ms, so it really seems like SpacePlane Plus issue. Maybe these mod parts are too aerodynamic?

[TheReaper]

deleting near fixes it, with near i recorded some weird stuff

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i also noticed that with near: my single rapier provides up to 130 thrust even on the runway when i use breaks, whit stock it gives only 90 maximum at runway,might be one of the reasons taht give huge speed boosts to far and near

[Woodstar]

NEAR isn't showing up in my toolbar, is there a hot key I need to press?

Edit: I see there is no toolbar dll in it how can I add this to toolbar?

[biohazard15]

NEAR isn't showing up in my toolbar, is there a hot key I need to press?

Edit: I see there is no toolbar dll in it how can I add this to toolbar?

You don't need toolbar for it, since NEAR does not allow in-game configuration.

[Woodstar]

AHH I liked the Display that gave me Info, guess it's back to FAR lol, but other than that I loved the mod it does make FAR simpler.

[TheReaper]

FAR punishing Stock:unrealistic near: doesnt work

HELP!

[rynak]

i also noticed that with near: my single rapier provides up to 130 thrust even on the runway when i use breaks, whit stock it gives only 90 maximum at runway

That is what Kerbal ISP Difficulty Scaler is for. The stock drag values are wrong, but fixing them in turn makes engines too powerful and deltaV too abundance - KIDS fixes the thrust and ISP issue.

[TheReaper]

That is what Kerbal ISP Difficulty Scaler is for. The stock drag values are wrong, but fixing them in turn makes engines too powerful and deltaV too abundance - KIDS fixes the thrust and ISP issue.

what if... stock drag value wrong generaly too much drag , stock engine power wrong generaly too much thrust... 2 wrongs make a right? hmmm

[ferram4]

@Nereid: No, because NEAR assumes that there are no compressibility effects to make it simpler. Mach number is always 0 with NEAR.

@Everyone having lag and weird CoL issues: Make sure you're using NEAR v1.0.3 and then makes sure to follow the instructions in the OP for dealing with messed up craft files.

@Everyone dealing with turbojet shenanigans: Alright, so then the plan for next time will be to nerf all the jet engines to 1/3 their current thrust, which should put them much closer to "realistic" than they currently are to start with. Given the size of the vehicles people are launching, you should be getting stuff like that, I mean, you've got more engine on some of these than the F-4, "with enough thrust anything flies" had. So nerfs will be in the next update, don't worry, I'll give you exactly what you're asking for.

@TheReaper: That is unhelpful, since you're not saying what's broken. For everyone els,e this is a good example of how not to make a bug report.

[rynak]

what if... stock drag value wrong generaly too much drag , stock engine power wrong generaly too much thrust... 2 wrongs make a right? hmmm

Not only do two wrongs not make a right (but they DO "compensate" - there's a difference , the stock behavior is much weirder than compensating wrongs: In stock, the drag depends on weight.... WET WEIGHT. That's right, in stock, drag changes as you empty your fueltanks. This makes launching vehicles experience much stronger drag, than landing vehicles. If in stock you fly with almost empty tanks, you get similiar drag to that in FAR, NEAR and SDF.

[TheReaper]

Not only do two wrongs not make a right (but they DO "compensate" - there's a difference , the stock behavior is much weirder than compensating wrongs: In stock, the drag depends on weight.... WET WEIGHT. That's right, in stock, drag changes as you empty your fueltanks. This makes launching vehicles experience much stronger drag, than landing vehicles. If in stock you fly with almost empty tanks, you get similiar drag to that in FAR, NEAR and SDF.

i guess i failed at word plays welll i really find it really awkward why would squad choose weight in the first place as adrag model, im not really an aerodynamic engineer or anything but .. come on, also i guess ill be re-installing far, perhaps i i disable failures it might be as good as it gets as if im having near.

@ferram4 honestly i dont really have any idea what to do, the problem i said happens to be in the assembly not sure debug log will help in there as much. if i am wrong, and appereantly i am, you can help by correcting, then i can help myself by properly making a bug report.

Edited July 20, 2014 by TheReaper

[Master Tao]

... the problem i said happens to be in the assembly not sure debug log will help in there as much.

The output_log.txt is useful for problems that happen at any time – it's used from when the game first starts loading until you quit (or it finishes crashing). It also helps to describe what doesn't work, provide pictures, example crafts, and say what you've tried to fix the problem already. It's particularly helpful to show that the problem happens with only one mod installed.

[TheReaper]

The output_log.txt is useful for problems that happen at any time – it's used from when the game first starts loading until you quit (or it finishes crashing). It also helps to describe what doesn't work, provide pictures, example crafts, and say what you've tried to fix the problem already. It's particularly helpful to show that the problem happens with only one mod installed.

thank you on the output log, on a more previous post i did described what it was, and with pictures

[Kerdan]

I seem to have come across a bug...

..I was able to replicate it using the following vessel:

MK1 Capusule * Stage 1

TR18-A Stack Separator * Stage 2

TR18-A Stack Separator * Stage 3

FL-T100 Fuel Tank

LV-T30 Engine

Launch the craft to a reasonable height and stage the bottom stage (Engine/Tank/Separator) so only the capsule and second separator are left. Turn off SAS and let the craft coast into the air. I would expect the heat shield end of the capsule to face towards the direction of travel, however instead the craft sits sideways - roughly 90 degrees to the direction of travel. If I stage the second separator the craft will then reorientate itself - with heat shield towards the direction of travel.

Has any one else come across this or be able to reproduce it as I described?

It still occurs even if I have a parachute attached to the top of the capsule. I might switch to FAR and see if it occurs there too.

[123nick]

does this require unique configs for aerodynamic parts? like far?

[ferram4]

@TheReaper: Could you post a link to that? I'm not finding where you posted the output_log.txt and repro steps.

@Kerdan: That is not a bug, that is intended behavior. The extra separator messes up the location of the CoM and CoD sufficiently that it is not stable in the configuration that you think it should be in. The stability of the mk1 pod is very delicate, and adding other parts can change its behavior drastically. Once again, not a bug, intended behavior.

@123nick: Only for wings, just like FAR. Payload fairings and cargo bays still need to proper info in their titles to be detected, but that functions as well.

[Renegrade]

As far as I can tell, Spaceplane Plus does not alter stock engines at all - you would be getting a similar result with a plane of similar weight and aerodynamical properties with just stock parts.

My mistake, I thought he was using Spaceplane Plus turbojets or something (everything else in that screenshot looked Spaceplane Plus-y, which actually is very nice looking).. going through my parts list, it looks like it might not have engines afterall.

I did a test and again used two turbojets, but this time I build plane from stock parts. As you can see, with same scenario, plane reached 500ms, so it really seems like SpacePlane Plus issue. Maybe these mod parts are too aerodynamic?

Could be, but then again, they do look rather aerodynamic... having that big bulge from the bi-coupler on the stock plane can't be good for aero I imagine..

@Everyone dealing with turbojet shenanigans: Alright, so then the plan for next time will be to nerf all the jet engines to 1/3 their current thrust, which should put them much closer to "realistic" than they currently are to start with. Given the size of the vehicles people are launching, you should be getting stuff like that, I mean, you've got more engine on some of these than the F-4, "with enough thrust anything flies" had. So nerfs will be in the next update, don't worry, I'll give you exactly what you're asking for.

KHAAAAAAAAAAAAAAN!

Actually, y'know.....

Maybe a little nerfing is justified? Is this speed related to the lack of increased drag at supersonic speeds?

(actual engine output is 192.4kn about 2 seconds after that shot. A SpacePlane plus version of that was only able to reach 663@185... A double-engine SPP version of that reached over 900 :S )

By the way, having read the entire FAR thread back in the 0.23 days, I do seem to recall that FAR (and presumably NEAR) both use stock drag code for a handful of things.. Is that [still] correct? It was intakes and parachutes right?

[ferram4]

Intakes no longer run on stock drag, because for some reason the engine body parts now have fuel in them, which means that they'll make a ton of drag due to the extra mass from the fuel. Parachutes are still running on that.

If you want to, go and mess with the numbers yourself (there's a MM config in the NEAR folder with the changes) and find something that seems right. I don't have the time to do that, I'm working on some stuff for AJE and being prepared for more bugfixes for NEAR + FAR.

[NathanKell]

Basically, you can *never* make jets perform correctly with the stock engine code, because the stock engine code is written for rockets, not jets. KSP jets are air-breathing rockets, not actual jets.

[camlost]

@ferram,

About the new AJE solver, how much difference do you expect to see from the old one? Have you done similar work in your study before? Is this model from a textbook, some other software or did you recently figured it out?

[Renegrade]

Intakes no longer run on stock drag, because for some reason the engine body parts now have fuel in them, which means that they'll make a ton of drag due to the extra mass from the fuel. Parachutes are still running on that.

Oh okay - note that that was a problem with the big inline intake ("Engine Nacelle") even before it had fuel in it in Stock aero - an airplane with circular/ram/scoops would have noticeably less drag than any built around the inline. I used to have a design back in the .22 days that used the inline intakes as air brakes, heh.

I was asking about the intakes as I tried building one of those super-duper Mach 2+@Sea Level planes initially with the inline intake and it still seemed kinda draggy compared to the scoop.. it couldn't reach supersonic at all...

As an example, I've tested (with NEAR 1.03) a very simple design with a basic jet engine that has both a pair of scoops and an inline intake - using only the scoops open, the top speed at 1km altitude was 253, but only 216 with only the nacelle/inline intake. The nacelle is taking in less air too.

If you want to, go and mess with the numbers yourself (there's a MM config in the NEAR folder with the changes) and find something that seems right. I don't have the time to do that, I'm working on some stuff for AJE and being prepared for more bugfixes for NEAR + FAR.

I'll take a swing at it... (Hmm, maybe playing with thrust curves instead of overall thrust...)

Basically, you can *never* make jets perform correctly with the stock engine code, because the stock engine code is written for rockets, not jets. KSP jets are air-breathing rockets, not actual jets.

True! I understand that real life jet engines are sensitive to a lot of variables, whereas KSP ones are just sensitive to speed (and AirFlow, but if it goes below a certain level)... so a perfect replica isn't even remotely possible.

Therefore, should our goal be to approximate stock performance? Maybe a bit better/worse?