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

[camlost]

Ahhh-... -on the edge of my mind, I know there's a way to determine this.

From what I looked up earlier, jet startup requires N2 to reach a certain level before fuel flow is introduced to the engine. I would assume that said N2 level would be the rotation speed needed to generate the pipe pressure for stable ignition, plus a percentage wiggle room for adverse start conditions.

I think if you reference a known engine's ignition threshold for N2, you can calculate the pipe pressure in relation to Standard Temperature and Pressure and get a ballpark estimate.

You'll need a well-documented engine for the task. Max RPM of the N2 stage, the percentage of that value where the fuel flow is introduced and combusted, and the parameters of the N2 (high pressure compressor) stage so you can calculate what it produces in terms of pressure.

I think once you have that, you're golden.

Also, once that works, forced flameouts due to improper engine pressure would be cool.

AJE uses a steady-state model not a transient model. That means we don't have RPM at all. Feel free to look at https://github.com/camlost2/AJEsolverTester for acronyms and everything.

[AdmiralTigerclaw]

AJE uses a steady-state model not a transient model. That means we don't have RPM at all. Feel free to look at https://github.com/camlost2/AJEsolverTester for acronyms and everything.

TTR isn't explained. I mentioned that.

And you misunderstood what I said. You can use a known engine's parameters to find what the pressures are for ignition and standard sustained operation. Then you have the known values instead of @_@ guestimates.

Edited October 11, 2015 by AdmiralTigerclaw

[blowfish]

O_O camlost is back!!!

TTR isn't explained. I mentioned that.

And you misunderstood what I said. You can use a known engine's parameters to find what the pressures are for ignition and standard sustained operation. Then you have the known values instead of @_@ guestimates.

I know of no sources that go into this level of detail for an engine. To do this, we would need to know tailpipe pressure at engine idle. I have not seen tailpipe pressure or any stats given for idle for any engines whatsoever.

TTR stands for turbine temperature ratio. It's not something you have to set yourself. It works like this: you specify CPR (compressor pressure ratio) at the design point*. AJE then uses this to calculate TTR. That TTR is then used to calculate prat3 (compressure pressure ratio again) at off-design conditions.

* It's ambiguous, when looking at spec sheets, whether this is specified at some flight design point or at static conditions. AJE assumes the former, but I'm inclined to believe the latter.

[Svm420]

Hey are you still going to add the J75-P-17 when you get a chance?

[blowfish]

Hey are you still going to add the J75-P-17 when you get a chance?

Yes, but it's hardly worth pushing an entirely new version just for that and no new versions have been released since you requested it. If you want, I can whip up a quick config for you to use in the mean time.

[Svm420]

Yes, but it's hardly worth pushing an entirely new version just for that and no new versions have been released since you requested it. If you want, I can whip up a quick config for you to use in the mean time.

I'd take it . Really appreciated!

[legoclone09]

Can you make a version with the stock engines? I would like that, and a person asked for a more Kerbal-styled realism, and not real-life realism.

[blowfish]

Can you make a version with the stock engines? I would like that, and a person asked for a more Kerbal-styled realism, and not real-life realism.

Could you be more specific? All of the stock engines are converted to rough RL equivalents, and this will be even more true in 1.0.5 with the new engines added. AJE's model takes a lot of parameters which can really only be determined from real engines. What aspect isn't "stock enough" for your needs?

[legoclone09]

I mean like the stock engines having real behavior but not real engines, so it's Kerbal engines with realistic physics. Sorry for the late reply.

[blowfish]

I mean like the stock engines having real behavior but not real engines, so it's Kerbal engines with realistic physics. Sorry for the late reply.

Sorry, but I'm still not sure what you mean. All of the stock engines are matched to rough RL equivalents, and while of course there are some differences the overall performance and use cases and up being pretty similar. So which aspects of which engines specifically do you feel aren't to your liking?

[NathanKell]

blowfish: I think legoclone09 sees AJE's configs like Realism Overhaul's engine configs, but wants RF Stockalike-style engine configs.

[blowfish]

blowfish: I think legoclone09 sees AJE's configs like Realism Overhaul's engine configs, but wants RF Stockalike-style engine configs.

That makes some sense, but it still doesn't point to exactly what legoclone09 wants to change. RF Stockalike keeps the thrust and overall role of rocket engines, while setting the mass and Isp to realistic values. In AJE, thrust is ambiguous because it can be dry/wet and the intended use cases are already pretty well matched (and will be even better with 1.0.5).

[Naten]

The SXT 0.625m engine for the Bonanza, the Continental something something, is not wörk wörk. It works completely fine except for the fact that it doesn't need any fuel to run.

[baldamundo]

Is there a good guide/summary to what altitudes/speeds each engine is best at, under what conditions they overheat, etc? I like the idea of more realistic jet engines, but I worry I'll just be replacing one system I don't understand with another system I don't understand...

Also how's this mod in terms of performance/RAM footprint?

Cheers

[Svm420]

Is there a good guide/summary to what altitudes/speeds each engine is best at, under what conditions they overheat, etc? I like the idea of more realistic jet engines, but I worry I'll just be replacing one system I don't understand with another system I don't understand...

Also how's this mod in terms of performance/RAM footprint?

Cheers

Yep search the real engines on google they should correspond pretty closely to the real world counterparts. Temp is listed in the part description.

[baldamundo]

Yep search the real engines on google they should correspond pretty closely to the real world counterparts. Temp is listed in the part description.

Wouldn't that only help me if I was playing RO given that presumably they'll perform differently in Kerbin's atmosphere compared to Earth?

[Svm420]

Wouldn't that only help me if I was playing RO given that presumably they'll perform differently in Kerbin's atmosphere compared to Earth?

No. Long answer a little, but not enough to really matter. If you plan to use the mod you are planning for a lot more complicated engines than stock. Complicated doesn't mean harder necessarily it just means more intricate. So if you want to use the mod just try it see how it feel watch some videos. The mod is aimed for people who hate stock magic engines. It aims for realism first fun second. Not to say the mod isn't fun you just have to want what the mod offers.

Edited October 18, 2015 by Svm420

[blowfish]

Is there a good guide/summary to what altitudes/speeds each engine is best at, under what conditions they overheat, etc? I like the idea of more realistic jet engines, but I worry I'll just be replacing one system I don't understand with another system I don't understand...

There's no documentation on this, sorry. I can however tell you how engines in AJE behave in general, and about specific engines if you ask.

Overheating happens when the compressor gets too hot, which happens at high speed. Note that it's not cumulative - how close the engine is to overheating is only a function of what the engine is doing at that particular instant in time. The overheat bar will appear long before the engine explodes (which happens when it fills up completely), so there's plenty of time to throttle down.

There's no "optimal" altitude/speed for any engine. Altitude matters almost not at all - thrust decreases with air pressure, of course, and Isp increases a little bit with altitude (but so little that you probably won't even notice). As for speed, as a general rule higher bypass engines are more efficient at lower speeds but won't allow you to go as fast. Use high bypass turbofans for subsonic planes, low bypass turbofans for transonic planes, and turbojets for the best supersonic performance.

Also how's this mod in terms of performance/RAM footprint?

Both should be negligible.

- - - Updated - - -

Wouldn't that only help me if I was playing RO given that presumably they'll perform differently in Kerbin's atmosphere compared to Earth?

The only meaningful difference between Earth's and Kerbin's atmosphere is that Kerbin's is only 80% as tall. So altitude won't quite match up but everything else should hold.

[Autochton]

Regarding propeller engines, I've been thinking some thoughts. (Dangerous territory, that.)

I've been fiddling with setting up sounds for the engines of the RealPlanes mod (Genius Evil has let it go, and I've picked it up). I'm finding that FSengineSounds is not at all up to snuff - I'm finding I can't get pitch variation from power, for example. So I was considering, what would it take to solve that? I suspect I could code a plugin myself that did something comparable to the aforementioned, but I'm short on time usable for KSP mod work. It also seems like it'd make sense to include in AJE, given how it handles props.

I've been looking at videos of WWII-vintage piston engine startups as research, and there's a certain pattern that asserts itself: The starter engages (most of the engines I'm looking at have electric starters) with a distinct electric whir as the prop turns slowly, almost deliberately. Then, the engine itself engages, typically with a bit of a burst of smoke. At this point linears and radials diverge: Linears typically start up fairly smoothly and begin sounding like they normally will at idle. Radials instead cough and sputter for a good few more seconds - and put out significantly more smoke, too - up to half a minute, from what I hear due to needing more effort to clear out oil in the cylinders. Ideally, that's the sort of startup patterns I'd want to have.

So the question is, is such a thing even possible, and if so, what would it take? If it requires me learning C# (cripes, that'd make... 27? 28 languages now? I hear it's not hard if you already know Java...) and getting to coding, so be it - I've faced worse, it'll just mean the results will be a while in coming since I'm short on time. So if someone else is interested in the subject, that might make for results a bit closer to the present day. Especially if someone already on the AJE team thinks this is a good idea.

And yeah, I know, what am I doing, working on propeller engines in a game about space rockets. But let an old man have his follies, right?

[Svm420]

Regarding propeller engines, I've been thinking some thoughts. (Dangerous territory, that.)

I've been fiddling with setting up sounds for the engines of the RealPlanes mod (Genius Evil has let it go, and I've picked it up). I'm finding that FSengineSounds is not at all up to snuff - I'm finding I can't get pitch variation from power, for example. So I was considering, what would it take to solve that? I suspect I could code a plugin myself that did something comparable to the aforementioned, but I'm short on time usable for KSP mod work. It also seems like it'd make sense to include in AJE, given how it handles props.

I've been looking at videos of WWII-vintage piston engine startups as research, and there's a certain pattern that asserts itself: The starter engages (most of the engines I'm looking at have electric starters) with a distinct electric whir as the prop turns slowly, almost deliberately. Then, the engine itself engages, typically with a bit of a burst of smoke. At this point linears and radials diverge: Linears typically start up fairly smoothly and begin sounding like they normally will at idle. Radials instead cough and sputter for a good few more seconds - and put out significantly more smoke, too - up to half a minute, from what I hear due to needing more effort to clear out oil in the cylinders. Ideally, that's the sort of startup patterns I'd want to have.

So the question is, is such a thing even possible, and if so, what would it take? If it requires me learning C# (cripes, that'd make... 27? 28 languages now? I hear it's not hard if you already know Java...) and getting to coding, so be it - I've faced worse, it'll just mean the results will be a while in coming since I'm short on time. So if someone else is interested in the subject, that might make for results a bit closer to the present day. Especially if someone already on the AJE team thinks this is a good idea.

And yeah, I know, what am I doing, working on propeller engines in a game about space rockets. But let an old man have his follies, right?

If you are familiar with Github Blowfish already seems to have this in mind. Here. Sounds like he wants to do something like you described.

[blowfish]

Correct, but I only indend to modify the firespitter module so that it gets the throttle from AJE. I wasn't planning anything fancier than that.

[Autochton]

Correct, but I only indend to modify the firespitter module so that it gets the throttle from AJE. I wasn't planning anything fancier than that.

That ought to do something, all right. Honestly, my one foremost issue is that there's no pitch variation with throttle change. All the other stuff I can make work, more or less.

[legoclone09]

That makes some sense, but it still doesn't point to exactly what legoclone09 wants to change. RF Stockalike keeps the thrust and overall role of rocket engines, while setting the mass and Isp to realistic values. In AJE, thrust is ambiguous because it can be dry/wet and the intended use cases are already pretty well matched (and will be even better with 1.0.5).

Sorry for being confusing but it's the stock engines (turbojet and turboramjet and rapier) with realistic physics. Sorry for the confusion, and late reply.

[Svm420]

Sorry for being confusing but it's the stock engines (turbojet and turboramjet and rapier) with realistic physics. Sorry for the confusion, and late reply.

Think about what you are asking how can they use real physics if they aren't based on real engines? There is no magic guide to make a engine real. They are only realistic in that they mimic real world engines. So what are you asking for? I mean you either want realism or you want Kerbal.

[blowfish]

Sorry for being confusing but it's the stock engines (turbojet and turboramjet and rapier) with realistic physics. Sorry for the confusion, and late reply.

Like Svm420 said, you're still not being specific enough, I'm sorry to say. What aspects of those engines do you feel are not stock enough? e.g. thrust (which as I mentioned is ambiguous), top speed, efficiency?