[1.0.5] Advanced Jet Engine v2.6.1 - Feb 1

[Ser]

22 hours ago, blowfish said:

I have no idea if it's correct ... if you have data on the response rates of real engines I would definitely be interested to see it.

Couldn't find the concrete envelopes but here's some data:

Airbus flight operations briefing notes, read page 7.

An article on Harrier engines, view 1st paragraph on page 138: "the engine response time to throttle movements was found to be between 0.375 and 0.5 sec", but that is a special case.

A post in this thread states the following times:

CFM56-5:
29% N1 to 67%: 4 seconds
67% N1 to 83%: 1 second

In common, seems like those time limits are electronically set to prevent compressor stalling by rapid fuel flow into the engine, which may lead to reversing of gas flow. The process is described here.

From real world FAA regulations:

Spoiler

 

Part 33 AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
Subpart E--Design and Construction; Turbine Aircraft Engines

Sec. 33.73

Power or thrust response.

[The design and construction of the engine must enable an increase--
(a) From minimum to rated takeoff power or thrust with the maximum bleed air and power extraction to be permitted in an aircraft, without overtemperature, surge, stall, or other detrimental factors occurring to the engine whenever the power control lever is moved from the minimum to the maximum position in not more than 1 second, except that the Administrator may allow additional time increments for different regimes of control operation requiring control scheduling; and
(b) From the fixed minimum flight idle power lever position when provided, or if not provided, from not more than 15 percent of the rated takeoff power or thrust available to 95 percent rated takeoff power or thrust in not over 5 seconds. The 5-second power or thrust response must occur from a stabilized static condition using only the bleed air and accessories loads necessary to run the engine. This takeoff rating is specified by the applicant and need not include thrust augmentation.]


Amdt. 33-4, Eff. 4/23/71

 

 

 

Long story short, most info tells that the time should be not greater than 5 sec from idle to 95% TO/GA (in our case that is 100% thrust, I believe)

 

EDIT:

Here are some maths on the subject, but I doubt that such complexity is needed.

Edited February 9, 2016 by Ser

[blowfish]

2 hours ago, Ser said:

Couldn't find the concrete envelopes but here's some data:

Airbus flight operations briefing notes, read page 7.

An article on Harrier engines, view 1st paragraph on page 138: "the engine response time to throttle movements was found to be between 0.375 and 0.5 sec", but that is a special case.

A post in this thread states the following times:

CFM56-5:
29% N1 to 67%: 4 seconds
67% N1 to 83%: 1 second

In common, seems like those time limits are electronically set to prevent compressor stalling by rapid fuel flow into the engine, which may lead to reversing of gas flow. The process is described here.

From real world FAA regulations:

  Reveal hidden contents

 

Part 33 AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
Subpart E--Design and Construction; Turbine Aircraft Engines

Sec. 33.73

Power or thrust response.

[The design and construction of the engine must enable an increase--
(a) From minimum to rated takeoff power or thrust with the maximum bleed air and power extraction to be permitted in an aircraft, without overtemperature, surge, stall, or other detrimental factors occurring to the engine whenever the power control lever is moved from the minimum to the maximum position in not more than 1 second, except that the Administrator may allow additional time increments for different regimes of control operation requiring control scheduling; and
(b) From the fixed minimum flight idle power lever position when provided, or if not provided, from not more than 15 percent of the rated takeoff power or thrust available to 95 percent rated takeoff power or thrust in not over 5 seconds. The 5-second power or thrust response must occur from a stabilized static condition using only the bleed air and accessories loads necessary to run the engine. This takeoff rating is specified by the applicant and need not include thrust augmentation.]


Amdt. 33-4, Eff. 4/23/71

 

 

 

Long story short, most info tells that the time should be not greater than 5 sec from idle to 95% TO/GA (in our case that is 100% thrust, I believe)

 

EDIT:

Here are some maths on the subject, but I doubt that such complexity is needed.

Thanks for all the info.  I'm not 100% sure how to integrate it into AJE yet, but I'll take a look.

[MarvinCZ]

On 7. 1. 2016 at 11:55 PM, blowfish said:

As for the effects, do you have RealPlume or HotRockets installed?  The way AJE interacts with effects was changed recently and I'm not sure that either has been updated to reflect this (HotRockets hasn't been updated in a very long time regardless).

I had the same problem with permanent afterburner plumes. I solved it by removing SmokeScreen, which came with B9.

[blowfish]

55 minutes ago, MarvinCZ said:

I had the same problem with permanent afterburner plumes. I solved it by removing SmokeScreen, which came with B9.

If you remove SmokeScreen, then all the B9 effects will break.  SmokeScreen doesn't do anything by itself, so you probably have some configs somewhere that are messing it up.  HotRckets (MP_Nazari) is the prime suspect.

[MarvinCZ]

39 minutes ago, blowfish said:

If you remove SmokeScreen, then all the B9 effects will break.  SmokeScreen doesn't do anything by itself, so you probably have some configs somewhere that are messing it up.  HotRckets (MP_Nazari) is the prime suspect.

Yes, I misunderstood how these FX mods work. After adding SmokeScreen back, it still works - I also removed the dummy HotRockets config that comes with B9 (contains only "BOGUS_NODE {}"), and if I add that back, the effects break.

I'm not sure whether this is again only proxy to the actual problem, though.

[blowfish]

52 minutes ago, MarvinCZ said:

Yes, I misunderstood how these FX mods work. After adding SmokeScreen back, it still works - I also removed the dummy HotRockets config that comes with B9 (contains only "BOGUS_NODE {}"), and if I add that back, the effects break.

I'm not sure whether this is again only proxy to the actual problem, though.

That folder is telling MM that MP_Nazari is installed, so certain AJE patches are activating that shouldn't be.  I should probably remove that from B9 anyway.

[winged]

Quote

If you wanted the glow back, you would have to switch the animation module to FXAnimateThrottle

Hi blowfish, thank you for your answer on github about Nene. May I ask what exactly I need to add? Something like this below probably but it also must be something inside the { } ?

[blowfish]

@winged things are in kind of a weird state right now.  The YJ93 config switches over all the animation modules before the clone parts (such as the Nene) are created.  Except that I forgot to update the config when I redid the animation stuff, so it changes it to ModuleAnimateHeatAJEJet which doesn't exist anymore rather than ModuleAJEJetAnimateAfterburner which it should.

The simplest thing to do is probably to just get rid of the existing module an re-add the original FXModuleAnimateThrottle with some modified parameters.  Something like this:

@PART[aje_nene]:FINAL
{
	!MODULE[ModuleAnimateHeatAJEJet] {}
	!MODULE[ModuleAJEJetAnimateAfterburner] {}

	MODULE
	{
		name = FXModuleAnimateThrottle
		animationName = jet_turbofan_heat
		responseSpeed = 0.01
		layer = 1
		dependOnEngineState = True
	}
}

the modifications being that it no longer has an engineName (which pointed to the other engine module which AJE gets rid of), and the response speed is increased a bit.

Put that in a config somewhere in GameData (I like to keep all my custom patches somewhere separate) and it should work.

Also keep in mind this only applies to the Nene and the Welland, the situation might be quite different for the FJ-44 and Derwent.  Not even sure if the parts those are built from in SXT even have thermal anims.

[winged]

It works fine, thank you!

[Tidus Klein]

SO im really starting to think that AJE do's not simulate reaction engines well. ive been reading up on the IRL Saber engine and this thing just seems godly, but anytime i use it in KSP with realfuels and the alike configs it just eats thru LH2 like a fat kid in a twenky factor, I understand that KSP,s fuel tank fractions  are poor and are tanks dont hold that much compared to IRL, but is this realistic? I can barly get to mach 4 on a full tank let alone obit on "stock" sized kerbin

I know that the ISP in rocket mode is off as the wiki says it should be 430 and not 360, but the airbreathing mode it says the isp is 3600 which AJE gets right, my question is, sense the saber is a rocket engine, is it realistic to simulate it as a turbojet in air breathing mode or as a straight rocket? I would try and find this info my self but info on the saber's actual specs..is limited at best.

 

I guess the best way is to show you my craft, KSP's stock Mk3 parts have crap internal volume. i do note on stock fuels i can reach a 150.000 circular orbit with 1,200 DV left in the tank with no load. with Lh2 and Lox im lucky to get up to 30,000 on open cycle. (I know KSP's tanks are crap:P)

http://imgur.com/a/06voZ

 

Edited March 5, 2016 by Tidus Klein

[KerbonautInTraining]

After playing with this mod for a few minutes, I think this video is very relevant.

Fighter jet engines do not take the same amount of time to spool as a 777's GE-90s. I skimmed through some of the above discussion but evidently it's talking about large turbofans.

I'm sorry if there's a reason some of the engines aren't like this, but I think it's kind of a glaring oversight regardless.

Also, some of the engines idle at... 20% thrust? What?

Edited March 7, 2016 by KerbonautInTraining

[blowfish]

52 minutes ago, Tidus Klein said:

SO im really starting to think that AJE do's not simulate reaction engines well. ive been reading up on the IRL Saber engine and this thing just seems godly, but anytime i use it in KSP with realfuels and the alike configs it just eats thru LH2 like a fat kid in a twenky factor, I understand that KSP,s fuel tank fractions  are poor and are tanks dont hold that much compared to IRL, but is this realistic? I can barly get to mach 4 on a full tank let alone obit on "stock" sized kerbin

I know that the ISP in rocket mode is off as the wiki says it should be 430 and not 360, but the airbreathing mode it says the isp is 3600 which AJE gets right, my question is, sense the saber is a rocket engine, is it realistic to simulate it as a turbojet in air breathing mode or as a straight rocket? I would try and find this info my self but info on the saber's actual specs..is limited at best.

 

I guess the best way is to show you my craft, KSP's stock Mk3 parts have crap internal volume. i do note on stock fuels i can reach a 150.000 circular orbit with 1,200 DV left in the tank with no load. with Lh2 and Lox im lucky to get up to 30,000 on open cycle. (I know KSP's tanks are crap:P)

http://imgur.com/a/06voZ

A few things:

1. LH₂ takes up a huge amount of volume but isn't very dense.  Look at the vessel mass with stock fuels, and try to match it with real fuels.  If you're filling the same tank volume with less dense fuel, you're going to have less fuel.
2. The SABRE is a very unique engine cycle that doesn't really allow it to be classified as a rocket or a jet.  A jet is probably a better bet in air-breathing mode.  I've tried to come up with a better solver for the SABRE, but it has issues so it's not ready to see the light of day yet.
3. REL has very inconsistent data, but it's possible that the SABRE's I_sp is underestimated by a factor of 2.  I might consider changing it.
4. I_sp in rocket mode should be set by RF Stockalike, not AJE.  I added changes to RF Stockalike that increase it to 460s in a vacuum, but I'm not sure if those changes have been released yet.

hope that helps

20 minutes ago, KerbonautInTraining said:

After playing with this mod for a few minutes, I think this video is very relevant.

Fighter jet engines do not take the same amount of time to spool as a 777's GE-90s. I skimmed through some of the above discussion but evidently it's talking about large turbofans.

I'm sorry if there's a reason some of the engines aren't like this, but I think it's kind of a glaring oversight regardless.

The code that determines how fast engines spool has been in there for a long time and hasn't changed.  I'm not opposed to changing it, but it has to be based on hard data on how long it takes real engines to spool, and how to extrapolate those values to engines that don't have data.  I'm not going to change it to something that just "feels right."

22 minutes ago, KerbonautInTraining said:

Also, some of the engines idle at... 20% thrust? What?

It may be too high, but again, without hard data I'm very hesitant to change it.  And it's better than how it was before, where many engines would idle at negative thrust.

[KerbonautInTraining]

1 minute ago, blowfish said:

The code that determines how fast engines spool has been in there for a long time and hasn't changed.  I'm not opposed to changing it, but it has to be based on hard data on how long it takes real engines to spool, and how to extrapolate those values to engines that don't have data.  I'm not going to change it to something that just "feels right."

It may be too high, but again, without hard data I'm very hesitant to change it.  And it's better than how it was before, where many engines would idle at negative thrust.

Sorry for being harsh. The throttle response was the main thing I was looking for.

I agree, reverse thrust in flight = bad time. Do you usually just shut the engines down with an action group when descending?

[Tidus Klein]

43 minutes ago, blowfish said:

A few things:

1. LH₂ takes up a huge amount of volume but isn't very dense.  Look at the vessel mass with stock fuels, and try to match it with real fuels.  If you're filling the same tank volume with less dense fuel, you're going to have less fuel.
2. The SABRE is a very unique engine cycle that doesn't really allow it to be classified as a rocket or a jet.  A jet is probably a better bet in air-breathing mode.  I've tried to come up with a better solver for the SABRE, but it has issues so it's not ready to see the light of day yet.
3. REL has very inconsistent data, but it's possible that the SABRE's I_sp is underestimated by a factor of 2.  I might consider changing it.
4. I_sp in rocket mode should be set by RF Stockalike, not AJE.  I added changes to RF Stockalike that increase it to 460s in a vacuum, but I'm not sure if those changes have been released yet.

hope that helps

ya I know Lh2 was far less dense...part of the problem here is that Ksp's tankage has very bad Dry wet ratios and honestly very crap utilazation, a b9 HL tank holds 53,000 units while a stock mk3  only holds 25,000, im just finding it hard to believe that it uses up between 140-220 units a second in airbreather, i also note that the saber IRL is supposed to have a max thrust of almost 2,000 KN, in airbreathing? and 3,000 in closed cycle.  oops thanks skylon user manual, ok so its supposed to have a open cycle max thrust of 1350, and closed is 1800 kn.

its also skylons crazy stats that make me think the saber engine acts more like a rocket in both modes i mean the manal says its going mach 5 in 11/12 minutes and climbing to a ceiling of 28,000M at the same time...thats a lot of thrust right off the bat.

im going to do more research on reaction engines see if i cant get a soild answer

Edit. I cant seem to find static thrust info on any LACE or reaction engines, or any info at all on how it would work in airbreather mode, but using the info i did find i put together a simple theory,

all that giant intake is for is to feed the precooler to make LOX then that LOX is feed to the rocket engine, in the skylon users manual and wiki it said that the engine will have more then enough intake air to do its  job, this is why the engine has the small ramjets on the side's to make up drag losses, so if all that intake and compressor is doing is feeding LOX to the rocket woudent that mean that the engine would act more like a rocket then a turbojet do to the fact its thrust is not directly related to airflow? but the LOX obtained from that air.

but hay thats just a theroy

 

Edited March 5, 2016 by Tidus Klein

[KerbonautInTraining]

So I just realized how hard it would be to implement "true" throttle response...

The only sensible way I can think is to have a table of x and y values, x being throttle response speed or something along those lines and y being current thrust percent. Jet engines are more responsive near full thrust, which is why they have a "flight idle" and fuel saving "ground idle". But I'm sure you already know this.

This wouldn't really work because you'd need accurate performance graphs to base it on.... ugh. Not to mention a complete re-write of the code.

You mentioned you did math to find out how quickly the engines should respond, is this math done in or outside of the mod? Is there an engine spec in the cfg that effects throttle response alone (i.e. compressor mass) 

I like this mod a lot, but I'd prefer faster throttle response at the cost of realism for myself. What can I say? I love VTOL's.

Edited March 7, 2016 by KerbonautInTraining

[blowfish]

5 minutes ago, KerbonautInTraining said:

You mentioned you did math to find out how quickly the engines should respond, is this math done in or outside of the mod? Is there an engine spec in the cfg that effects throttle response alone (i.e. compressor mass)

It's just based on area (compressor+bypass), but clamped at a minimum of 5% per second.

On 3/5/2016 at 0:37 PM, Tidus Klein said:

Edit. I cant seem to find static thrust info on any LACE or reaction engines, or any info at all on how it would work in airbreather mode, but using the info i did find i put together a simple theory,

all that giant intake is for is to feed the precooler to make LOX then that LOX is feed to the rocket engine, in the skylon users manual and wiki it said that the engine will have more then enough intake air to do its  job, this is why the engine has the small ramjets on the side's to make up drag losses, so if all that intake and compressor is doing is feeding LOX to the rocket woudent that mean that the engine would act more like a rocket then a turbojet do to the fact its thrust is not directly related to airflow? but the LOX obtained from that air.

but hay thats just a theroy

Depending on what source you use, the static thrust of the SABRE is somewhere in the range of 600-800 kN/nacelle.

How much air the compressor requires depends a lot on mach number.  Just before switching to rocket mode, all the air is going to the compressor, but at other flight conditions the intake admits more air than the compressor will accept.  The ramjets offer an alternative to a highly complex movable intake geometry as on the SR-71 (but worse, since the required mach range is larger).

The SABRE does not liquefy the incoming air.  That's LACE.  Even in an engine like the SABRE, the majority of the flow is air, not fuel, which means that combustion chamber pressure is going to be roughly proportional to ambient pressure and TPR losses are going to affect I_sp a great deal.  A jet is not the ideal model but it's better than a rocket for now.

[KerbonautInTraining]

5 hours ago, blowfish said:

It's just based on area (compressor+bypass), but clamped at a minimum of 5% per second.

Sorry for the consistent posting, but is there a variable in the engine's cfg that can be changed to increase response rate, if so, which one? I changed "area" in the F-100's cfg up and down by an order of magnitude and it didn't appear to do anything. (time from idle to 100% was 20s)

Edited March 7, 2016 by KerbonautInTraining

[blowfish]

12 minutes ago, KerbonautInTraining said:

Sorry for the consistent posting, but is there a variable in the engine's cfg that can be changed to increase response rate, if so, which one? I changed "area" in the F-100's cfg up and down by an order of magnitude and it didn't appear to do anything. (time from idle to 100% was 20s)

There's no way to change it currently.  Decreasing the area will mostly just decrease thrust.  Well, response speed should be changing too, but maybe it's already hit the 5% clamp on response speed.

[Svm420]

@blowfish

IS it a known issue that setting thrust limiter has no effect on ModuleEnginesAJERotor in flight? I am unable to use the thrust limiter to balance my VTOL so this was rather disappointing . Hope this isn't intended as it appear to function in the editor but in flight I always have 100% thrust range. Thanks!

Edited March 24, 2016 by Svm420

[blowfish]

59 minutes ago, Svm420 said:

@blowfish

IS it a known issue that setting thrust limiter has no effect on ModuleEnginesAJERotor in flight? I am unable to use the thrust limiter to balance my VTOL so this was rather disappointing . Hope this isn't intended as it appear to function in the editor but in flight I always have 100% thrust range. Thanks!

That sounds like a bug, and I think I know the cause and fix.  Submit a ticket on Github and I'll try to fix it when I've got time.

[Svm420]

3 hours ago, blowfish said:

That sounds like a bug, and I think I know the cause and fix.  Submit a ticket on Github and I'll try to fix it when I've got time.

Done

 

Thanks!!

Edited March 25, 2016 by Svm420

[Ser]

On 07.03.2016 at 1:48 AM, blowfish said:

There's no way to change it currently.  Decreasing the area will mostly just decrease thrust.  Well, response speed should be changing too, but maybe it's already hit the 5% clamp on response speed.

People suffer so much with those spool up times. Do something please

Edited March 25, 2016 by Ser

[blowfish]

4 hours ago, Ser said:

People suffer so much with those spool up times. Do something please

Find me some hard data to "do something" with and I'll consider it .  Otherwise I'm just replacing made-up numbers with other made-up numbers.

[Ser]

On 25.03.2016 at 5:21 PM, blowfish said:

Find me some hard data to "do something" with and I'll consider it .  Otherwise I'm just replacing made-up numbers with other made-up numbers.

May be giving a configurable modifier to the spool up times could be the temporary solution until the "hard data" is found, so everyone could set the value that he feels right?

[Svm420]

@blowfish

 

Would ambient temperate affect rotor thrust as well? I am getting only ~83kN and ~33Khp from the f135 lift fan even though it is 90kN and 35kHP in the config. Though the thrust I am getting is pretty spot on for RL. Just curious as I am trying to get a functional f-35b. Thanks!