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

[mecki]

Thanks for the update!

If not known: It's not on CKAN yet *duckingaway*

[CaptainBlue]

Hi, I'm flying around with a slightly modified Aeris 4A (tail changed into a dual 45 degree tail, added two more radial attached intakes) with a single RAPIER engine in the middle. KSP version 0.90, AJE ver. 2.0.2 (no RealFuel, and no RSS, FAR ver 0.14.6)

I get to around 18km at 900+m/s with the two P&W J58-P-4 and switched on the the single RAPIER in airbreathing mode, then got to 22km and switched off the two engines and changed the RAPIER mode to closed cycle, it instantly overheated and exploded. I can't figure out what I am doing wrong. Help!

[blowfish]

changed the RAPIER mode to closed cycle, it instantly overheated and exploded. I can't figure out what I am doing wrong.

Update to 2.0.3. A fix was implemented for this specific problem.

[CaptainBlue]

Thats a fast response heh, thanks.

[blowfish]

I've reached an important milestone on the variable bypass code - my testing has confirmed that increasing bypass ratio (at the expense of core area) does in fact reduce the rate of compressor overheats on the J58 at high speed. Expect a test build in the next couple of days

[camlost]

I've reached an important milestone on the variable bypass code - my testing has confirmed that increasing bypass ratio (at the expense of core area) does in fact reduce the rate of compressor overheats on the J58 at high speed. Expect a test build in the next couple of days

From a realism point of view, J58 should have FPR=1, mixer before nozzle, Area*(1+BPR)=constant while BPR is function of Mach number. Is that what you did?

[blowfish]

From a realism point of view, J58 should have FPR=1, mixer before nozzle, Area*(1+BPR)=constant while BPR is function of Mach number. Is that what you did?

Total area is constant, yes (that's how the code is designed), and the exhaust mixer is indeed enabled. The FPR is a little trickier because (1) prat2 varies proportionally with prat3 and (2) The bypass tubes divert flow from the 4th stage of the compressor so FPR=1 isn't quite correct. I've found sketchy data suggesting that the bypass flow gains a pressure ratio of 1.6:1 in the compressor when the whole compressor has prat3=2.9, so I've used that for now, but that data is unverified (source is this video).

As for how it's controlled, to maximize flexibility the bypass setting is adjustable using action groups and tweakables. It might make sense to have a default curve in there too though.

[blowfish]

Also, is there any data on the YF120? I would expect it to very similar to the F119 (though perhaps with a lower maximum BPR), but I can't seem to find anything definitive.

[blowfish]

Variable Bypass Test Build

It's done. You can get it here, with source available in the download and on Github. License is the same as the rest of AJE, available in OP and in download

Changes:

• Bypass can be controlled either via a default curve (as a function of mach number), or manually.
  
  • Switching between modes, as well as increasing and decreasing bypass in manual mode can be done via tweakables and action groups.
    
  • The increment for manual control is 20% (of maximum bypass). This may become adjustable at some point.
    

  [*]Adds variable bypass to two engines: The YF120 (new) and the J58.

  • The J58 opens bypass doors between mach 2 and mach 3 by default in order to create a turboramjet effect.
    
  • The YF120 (requires B9) closes its bypass doors between mach 0.9 and 1.0 to enable supercruise.
    
  • Little data is available on the YF120 so its parameters are based primarily on the F119. It may be adjusted if more information becomes available.
    

Please test and report any bugs to me, either on the forum or on Github .

[NathanKell]

That sounds most interesting...

[Errol]

I apologize if this has already been discussed here, I just discovered this thread. My question is are there currently any plans for integration with the new aero model that will be coming out in 1.0? Or at least making the FAR requirement optional once 1.0 is released?

[blowfish]

Bug: maxThrust is set the same for the both the Sabre M and Sabre S, meaning that the Sabre M's TWR ends up being much lower. Already reported on GitHub. What's the point of capping the thrust anyway?

- - - Updated - - -

I apologize if this has already been discussed here, I just discovered this thread. My question is are there currently any plans for integration with the new aero model that will be coming out in 1.0? Or at least making the FAR requirement optional once 1.0 is released?

Probably depends on the specifics of the new aero model. As far as I can tell there aren't any explicit FAR dependencies in the code right now, but it doesn't make sense to use it with stock aero since drag is so much higher in stock.

[Roikkeli]

Very nice mod, only issue that i have is that with this mod the rapier engine has a large performance gap between closed and open cycle modes. The engine pushes over 400kN in air-breathing mode, witch seems a little excessive for a 1.2 ton engine. when you switch to rocket mode the thrust drops to the stock 175kN and usually kills my acceleration until i get higher up in the atmosphere.

[Ramon91]

Nice mod, it worked perfectly for me in previous releases of the game, but today I installed aje in ksp .90 and it seems that engine's sound does not change nor go louder/quieter until I completely switch off engines. I've got also a problem with b9's engines (don't emmit any kind of smoke until afterburner, where it looks as expected) I know this is not the place for b9 issues, but it may be related or something.

Pd: I don't know if anyone had this problem before, but i searched a little and found nothing.

[blowfish]

Very nice mod, only issue that i have is that with this mod the rapier engine has a large performance gap between closed and open cycle modes. The engine pushes over 400kN in air-breathing mode, witch seems a little excessive for a 1.2 ton engine. when you switch to rocket mode the thrust drops to the stock 175kN and usually kills my acceleration until i get higher up in the atmosphere.

That's not static thrust though, is it? It's reasonable to expect thrust to grow with speed, but maybe it's growing a bit too much?

Nice mod, it worked perfectly for me in previous releases of the game, but today I installed aje in ksp .90 and it seems that engine's sound does not change nor go louder/quieter until I completely switch off engines. I've got also a problem with b9's engines (don't emmit any kind of smoke until afterburner, where it looks as expected) I know this is not the place for b9 issues, but it may be related or something.

I've experienced the engine sound (and heat anim) issue you speak of (no idea about the B9 thing though). It probably has to do with the fact that how much thrust the engine is producing (set by AJE) and how hard the engine *thinks* it's working are controlled completely separately. I would expect them both to depend on the main throttle though - not sure why that dependence would be breaking in the presence of AJE.

[Ramon91]

I've experienced the engine sound (and heat anim) issue you speak of (no idea about the B9 thing though). It probably has to do with the fact that how much thrust the engine is producing (set by AJE) and how hard the engine *thinks* it's working are controlled completely separately. I would expect them both to depend on the main throttle though - not sure why that dependence would be breaking in the presence of AJE.

Thanks for the explanation, let's see if it gets fixed soon.

[Sampa]

Who would go w/o FAR?

*raises hand* guilty!

[NathanKell]

On the Rapier--at high mach, it's getting air rammed into it for free. In closed cycle, it has to pump the air (as LOX) in. That's why.

[strongest_2hu]

The engine pushes over 400kN in air-breathing mode

I just tested it and on the first try I saw a bit over 500 kN before my plane DRE'd the intake off. Thrust was still climbing at an alarming rate, if I turn off DRE it would probably go past 600.

On the Rapier--at high mach, it's getting air rammed into it for free. In closed cycle, it has to pump the air (as LOX) in. That's why.

Considering that it's producing almost twice as much thrust as I've ever seen on any other AJE-modified engine at high speed, I suspect there was either an error in the inputs or it's a classic case of "this imaginary engine isn't balanced because it's imaginary". As it stands it offers similar efficiency as the other extreme high-speed jet engines with twice the thrust, and it also functions as a rocket engine. Why use anything else?

[Roikkeli]

On the Rapier--at high mach, it's getting air rammed into it for free. In closed cycle, it has to pump the air (as LOX) in. That's why.

My point was that this mod adds realistic air breathing performance for rapier while it leaves the rocket performance at the unrealistic low stock performance, creating an engine that feels unbalanced. The REL SABRE that the rapier is supposed to represent has higher thrust in rocket mode, not the other way around

The mod author has no doubt spent a lot of time for this mod and i don't want to just complain, so i end this post thanking for the awesome mod. I did solve the above issue by buffing rapiers rocket mode thrust to match the aje performance. The engine is now probably owerpowered for stock but balanced for the 10x kerbin that i'm using.

[blowfish]

My point was that this mod adds realistic air breathing performance for rapier while it leaves the rocket performance at the unrealistic low stock performance, creating an engine that feels unbalanced. The REL SABRE that the rapier is supposed to represent has higher thrust in rocket mode, not the other way around

The mod author has no doubt spent a lot of time for this mod and i don't want to just complain, so i end this post thanking for the awesome mod. I did solve the above issue by buffing rapiers rocket mode thrust to match the aje performance. The engine is now probably owerpowered for stock but balanced for the 10x kerbin that i'm using.

Yeah, now that I look at it again, I think the RAPIER's (and SABRE's) rocket thrust could probably use a buff - in AJE, you're typically lower in the atmosphere when you switch to rocket mode, meaning much more drag to overcome in order to get into orbit, so the rocket thrust should reflect that reality. According to REL's data, the real SABRE's rocket thrust will be something like 2.5x it's static air-breathing thrust, so maybe that's a good starting point.

[camlost]

A few notes on RAPIER's thrust

1. 400kN is an artificial hard cap that I feel somewhat appropriate. The stock thrust of 175kN in rocket mode is not weak.

2. If you actually reach it, much to my astonishment, you're probably flying at high mach number at low altitude. In the game you'll be punished by FAR and the high fuel consumption from AJE. In reality, this point would be outside the flight envelope

[strongest_2hu]

There's an artificial hard cap? Or are you just saying that there should be one?

[blowfish]

It's really a soft cap. You only get 10% of any thrust gains above 400 kN. Without it you'd be getting 4 MN out of that engine. Isp stays the same though, so you're not sacrificing fuel efficiency.

[NathanKell]

A suggestion: the SXT tinyprop be modeled as the Continental IO-550, which is what the part says it is, rather than a PT6. That would also give us an actual light-plane engine.