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

[camlost]

@Northstar1989,

1. The default F-100 engine has isp=3000+ without AB and 2000+ with AB, which is quite right seems to me. If you want more efficient high bypass turbofans you should use the CF6 in B9, which is usually ~6000s

2. What do you mean by

doesn't upgrade the ISP values to match their real-world counterparts, and doesn't adjust the thrust values appropriately.

The algorithm of AJE is from NASA EngineSim which uses thermodynamic equations to model jet engines. The parameters of AJE are derived from public data (wet/dry thrust and SFC, EPR). Why do you accuse AJE of cannot being accurate? What is being inaccurate exactly?

3. Modern jet engines have not improved that much from 30 years ago, neither have rocket engines. However, aerodynamic designs have improved a lot. FAR's scope is more or less similar to 50-60's technique before CFD is available. So it's more interesting to build engines from 30 years ago.

4. If you play on Kerbin instead of Earth there's no need of changing anything of an airplane design. They have the same gravity and atmosphere density at sea level. A airplane will fly a little better on Kerbin, since its atmosphere is 70% high

[NathanKell]

Northstar1989: I apologize.

If you want to know whether a jet engine's fuel consumption is being properly modeled, look at its fuel consumption. Conveniently, these stats exist in real life (SFC, in lbf-h) and can be calculated in KSP (FAR will tell you this, but you need to convert to lbf-h). You will find that with the Isp as AJE has it configured, the SFC is absolutely correct. (Assuming static thrust in both cases, since SFC is given for static thrust).

Since, again, AJE models real engines (it's not something like "remove intake air from stock jet stats"), you will hopefully realize that talking about stock engines' stats (and how, yes, their Isp is lower than contemporary real engines, once you correct for intakeAir) is utterly immaterial. AJE is replacing existing KSP engine parts with real engines, in this case with an F100 and a J58. So of course the stock turbofan is now going to perform like a 30-year-old engine; that's because it is one, one in particular: the F100. If you want a modern engine, make a modern engine. You can (heck, with B9 you get a modern high-bypass turbofan *and* the F119).

Mass is not being scaled; size is not being scaled (well, the compressor of the J58 is about 1.4m, but the nozzle is close to 1.25m). These are real size, real stats, real engines.

[Northstar1989]

the engine configs are taken right off real ones, it only makes sense to compare it with RSS. The engines are, plain and simple, modeled after real ones, there's no "kerbalizing" going on, which is nice. Also, AJE does adjust the values to real engine stats. It's just that those engines it simulates are old (at least, stock ones are converted to old engines). It's best used with jet engine mods like B9 that add newer engines.

The engine stats are taken off the 30-year old versions of those engines. You have to understand that, with newer materials and more advanced engineering, retrofitted versions of those engines have been created that drastically outperform their 30-year old versions, One player pointed this out earlier on this thread on like the 3rd or 4th page, and he was completely ignored.

I wouldn't want to use AJE without up-to-date retrofit stats being used for the 30-year old engines.

Regards,

Northstar

Edited May 21, 2014 by Northstar1989

[camlost]

NathanKell:

SFC is in lb/(lbf*h). Basically Isp=3600*g/SFC.

I'm still hazy about SFC being static. Are you sure about it? Where do you usually find engine specs?

[Guest]

The engine stats are taken off the 30-year old versions of those engines. You have to understand that, with newer materials and more advanced engineering, retrofitted versions of those engines have been created that drastically outperform their 30-year old versions, One player pointed this out right on the AJE in like the 3rd or 4th page, and he was completely ignored.

I wouldn't want to use AJE without up-to-date retrofit stats being used for the 30-year old engines.

Regards,

Northstar

In case you didn't notice, most KSP realism stuff is geared towards 30-40 year old tech. Besides B9 and LazTek, the most prominent realism patches deal with Apollo-era tech. It makes sense to put in some jet engines from that era, too. Now, a tech level system (similar to what RF uses) would be nice, but for a future update. For now, you can update configs yourself, or simply don't use stock engines.

[Northstar1989]

1. The default F-100 engine has isp=3000+ without AB and 2000+ with AB, which is quite right seems to me. If you want more efficient high bypass turbofans you should use the CF6 in B9, which is usually ~6000s

I'm sorry, but "AB"? Keep in mind that, even if I am familiar with the acronym you are using, it require context for me to know which "AB" you are talking about at the time...

2. What do you mean by The algorithm of AJE is from NASA EngineSim which uses thermodynamic equations to model jet engines. The parameters of AJE are derived from public data (wet/dry thrust and SFC, EPR). Why do you accuse AJE of cannot being accurate? What is being inaccurate exactly?

The parameters themselves are what's inaccurate. The ones you are using are for the 1970's/1980's version of those engines, rather than the newer retrofits. You also have to realize, the *newest* retrofits for military jet engines are going to still be classified- so you won't be able to obtain accurate data on the current cutting-edge-technology.

3. Modern jet engines have not improved that much from 30 years ago, neither have rocket engines. However, aerodynamic designs have improved a lot. FAR's scope is more or less similar to 50-60's technique before CFD is available. So it's more interesting to build engines from 30 years ago.[/quote[

Modern jet engines actually have improved quite a bit. Materials science, in particular, has advanced a LOT. Unfortunately, as I've repeatedly stated, the newest retrofits are still classified (I know this because both my parents both used to work in the defense industry with high level security clearances- while they couldn't tell me specifics, which are still top-secret, they did explain that this kind of information is often classified or hidden/obscured from the public).

If you want to approximate current cutting-edge technology, look at the advancement of jet engine technology between about 1977 and 1987, and then extrapolate the rate of progress forward about 30 years... (progress in materials science has actually ACCELERATED in recent years)

4. If you play on Kerbin instead of Earth there's no need of changing anything of an airplane design. They have the same gravity and atmosphere density at sea level. A airplane will fly a little better on Kerbin, since its atmosphere is 70% high

Actually, no, just no. Did you not read anything I said about the relevant orbital velocities?

On Kerbin, orbital velocity is only about Mach 6.3. On Earth, it's over Mach 25. The difference is due to the difference in the curvature of the planets (larger planets have more gradual curvature).

That means that on Kerbin, you will be moving at a MUCH higher fraction of orbital velocity during atmospheric flight- which high velocity can for all effects be modeled as reducing the force of gravity on your plane... (ESPECIALLY when flying East)

Regards,

Northstar

[Northstar1989]

If you want to know whether a jet engine's fuel consumption is being properly modeled, look at its fuel consumption. Conveniently, these stats exist in real life (SFC, in lbf-h) and can be calculated in KSP (FAR will tell you this, but you need to convert to lbf-h). You will find that with the Isp as AJE has it configured, the SFC is absolutely correct. (Assuming static thrust in both cases, since SFC is given for static thrust).

The Specific Fuel Consumption (SFC for others following along- once again, please avoid using an acronym without defining it first) is correct for the engines you have adjusted the stats to match. The problem, once again, is that Advanced Jet Engines has adjusted the stats to match the WRONG VERSIONS of those engines- that is, versions built with materials science more than 30 years old...

With the newer retrofits of those engines (I use this term rather loosely- I know that sometimes an engine is renamed entirely when retrofitted like this, while still maintaining more or less the same appearance and overall major design elements- in which cases, you aren't even matching to the right engine names/models either...) you WILL see superior performance, and either better Specific Fuel Consumption, or Thrust Weight Ratio.

The reasons for the better performance are usually due to use of newer materials and cooling systems that allow higher core and compressor operating temperatures in the newest engine retrofits. By upgrading the compressors and cores to work at these higher temperatures (through altering some of the internal design a bit), the newer retrofit engines have been made to provide superior performance to the older designs. Sometimes, the upgrades are also simply use of newer lighter-weight materials with the same strength and heat resistance, or improvement of the heat management so as to save on weight instead of improve SFC or thrust...

Since, again, AJE models real engines (it's not something like "remove intake air from stock jet stats"), you will hopefully realize that talking about stock engines' stats (and how, yes, their Isp is lower than contemporary real engines, once you correct for intakeAir) is utterly immaterial.

AJE models 30 year old engines. As I said, you have to use modern retrofits and space-grade materials for a standard of comparison.

AJE is replacing existing KSP engine parts with real engines, in this case with an F100 and a J58. So of course the stock turbofan is now going to perform like a 30-year-old engine; that's because it is one, one in particular: the F100. If you want a modern engine, make a modern engine. You can (heck, with B9 you get a modern high-bypass turbofan *and* the F119).

The stock turbofan is based on a 30-year old base design, the F100, yes, but the newest retrofits of the F100 drastically outperformed the original design... This is where AJE goes completely wrong- they should utilize stats that are BETTER THAN the latest retrofits, not 30-year old technology.

Mass is not being scaled; size is not being scaled (well, the compressor of the J58 is about 1.4m, but the nozzle is close to 1.25m). These are real size, real stats, real engines.

Mass and size are scaled for *some* things in the stock game, so I didn't know if i was the case with the jet engines. If mass isn't being scaled, though, then the fuselages are going to be much denser than their real-life versions (assuming AJE doesn't fix that), and are going to cause planes to perform better than they should...

Regards,

Northstar

[regex]

The parameters themselves are what's inaccurate. The ones you are using are for the 1970's/1980's version of those engines, rather than the newer retrofits. You also have to realize, the *newest* retrofits for military jet engines are going to still be classified- so you won't be able to obtain accurate data on the current cutting-edge-technology.

So, uh, if all that info is classified how is the OP going to use up to date stats? I'll also point out that the source is freely available for personal use, so you could just compile your own copy that meets your needs. Or am I asking too much of you?

[Northstar1989]

I'll also point out that the source is freely available for personal use, so you could just compile your own copy that meets your needs. Or am I asking too much of you?

ME, compiling? I absolutely suck at programming. Yeah, you're asking too much....

So, uh, if all that info is classified how is the OP going to use up to date stats?

Like I suggested, look at the rate of progress over an arbitrary period of time from the past (I suggested from 1977 to 1987), and extrapolate. It's the closest you're going to come to cutting-edge jet technology without the FBI hunting you down for espionage...

Regards,

Northstar

[Guest]

You probably are. Newer engine configs could be made anytime (provided the data is there), but I'd rather have a bunch of 70s jet engines for my vintage plane needs. Also, FYI, guessing and extrapolating is not an option. Anything but hard test data is not good enough, and good luck finding that for modern engines. I'm fine with KSP being a bit behind the times, Apollo era is the most interesting one for realism addons anyway.

Also, there's nothing to compile. Configs are literally text files. Take some time and learn config editing instead of constantly complaining about not having the engines you want.

Edited May 21, 2014 by Guest

[Northstar1989]

In case you didn't notice, most KSP realism stuff is geared towards 30-40 year old tech. Besides B9 and LazTek, the most prominent realism patches deal with Apollo-era tech.

I'm aware- and it irks me to no end! I don't want to play with Apollo-era tech, I want to explore what's possible with cutting-edge technology today!

Now, it's not much of a problem in the stock game, because stock parts are so good that I can accomplish anything I could with modern tech there anyways, and then some (due to being loosely modeled after real-world jet and rocket stats, but considerably OP'd, and operating in a universe where the star system is only 1/10th the Sol system's scale...)

But the Apollo program *barely* reached Luna (Earth's moon). I DO NOT want to play with technology that has been appropriately adjusted to actually reflect 1970's-era technology.

May I also point out that the STS-inspired parts introduced is 0.23.5 are all based on modern technology? That's why so many players have been calling them OP'd- because they don't fit the TWR:ISP curves players generated to fit the earlier Apollo-inspired stock parts...

It makes sense to put in some jet engines from that era, too. Now, a tech level system (similar to what RF uses) would be nice, but for a future update. For now, you can update configs yourself, or simply don't use stock engines.

I have no intention of updating configs myself. It would take too much research, and require me to repeat the effort every time I update AJE.

Would it be so hard for AJE to post multiple (2) separate configs in the release post, like Real Solar System does? One modeling the engines after Apollo-era tech, the other modeling them after modern day cutting-edge (and maybe even slightly near-future) technology...

Players like myself, who have no interest in re-creating what's already been done in Apollo, would stick to the modern technology configs, of course...

Regards,

Northstar

Edited May 21, 2014 by Northstar1989

[Guest]

Cutting edge has one basic problem. It's usually classified, or in some cases not done at all, because a whole lot of nice things are still on the drawing board. If you want future tech, write your own, fictional configs, with, yes, a lot of research not only into the jet engine mechanics, but also engineering trends and engine physics, so that the extrapolation actually makes sense. It's a lot of work, and if you can't do it, don't expect Camlost to do it. Oh, and you wouldn't have to repeat you work with each AJE update. Most of them are small adjustments/more configs, not config-breaking changes.

I'd rather be stuck in the 60s, when big rockets flew, music didn't suck and you writers wrote hard SF that was more science and less fiction.

[Northstar1989]

Cutting edge has one basic problem. It's usually classified, or in some cases not done at all, because a whole lot of nice things are still on the drawing board. If you want future tech, write your own, fictional configs, with, yes, a lot of research not only into the jet engine mechanics, but also engineering trends and engine physics, so that the extrapolation actually makes sense. It's a lot of work, and if you can't do it, don't expect Camlost to do it. Oh, and you wouldn't have to repeat you work with each AJE update. Most of them are small adjustments/more configs, not config-breaking changes.

First of all, you're talking about near-future technologies, not cutting-edge. Cutting-edge technologies are, by definition, technologies that have newly been *developed or implemented*, and are so "sharp" and new, and right on the technological edge of progress, we call them "cutting-edge"...

Therefore, while most of them ARE classified, they're certainly not future tech- and are not so far beyond what's currently public knowledge as that it should be too difficult to implement in a config...

Second, I don't know nearly enough about how to actually write configs to create one of my own. And I don't have the time to test them out, and make sure they work either (I barely manage to keep my current Career save humming along...)

I'd rather be stuck in the 60s, when big rockets flew, music didn't suck and you writers wrote hard SF that was more science and less fiction.

Ah yes- the 60's. When HIV was ravaging west Africa (having spent 80 years reaching epidemic levels) and had just reached the USA (and there were no treatments for it), personal computers didn't exist, and women were still treated like second-class citizens in the workplace...

http://www.theguardian.com/science/2003/may/22/research.science

http://news.nationalgeographic.com/news/2008/10/081001-hiv-aids-africa.html

Be happy with the present- you don't know nearly how far we've come...

Regards,

Northstar

Edited May 21, 2014 by Northstar1989

[NathanKell]

So basically you're complaining that a mod author didn't choose to model the engines you wanted her/him to model, but are also unwilling to do the research and make the changes to allow it to model the engines you *do* want modeled, despite all that taking is a web browser and some text file editing?

If you came here and said "hey folks, could someone help me make a late-mark F100?" the conversation would have been totally different.

[MedievalNerd]

As NathanKell said, all this time 'explaining' how things are wrong, you could have done said research and update the cfg file yourself.

Editing cfg files does not even require any programming skills.

Do more, ask less.

[Drew Kerman]

hey guys, what's the difference between the F100 and the F404? The only stat that changes between them is 0.7t of mass. Is the F100 just a backwards-compatible part? And other than being lighter is there any other advantage to the F404?

[Taverius]

Pizza 1.6 is currently waiting for approval on Curse ... should be trivial for you to update support if it needs any changes at all.

[camlost]

F404 is smaller, lighter and less powerful. Check out YF-16 and YF-17

[Drew Kerman]

F404 is smaller, lighter and less powerful. Check out YF-16 and YF-17

Sorry camlost, I still don't understand. How is the F404 less powerful when the stats show up exactly the same as the F101? When I mouse over them in the SPH the only things that change are the mass and descriptions. I'm guessing there's some back-end AJE coding at work to make the F404 less powerful, but it's not obvious at all when viewing the in-game stats.

[RedAV8R]

Sorry camlost, I still don't understand. How is the F404 less powerful when the stats show up exactly the same as the F101? When I mouse over them in the SPH the only things that change are the mass and descriptions. I'm guessing there's some back-end AJE coding at work to make the F404 less powerful, but it's not obvious at all when viewing the in-game stats.

You know...you asked about the F100 vs the F404...now in this post you are talking about the F101???...I'm sure one has to be a typo, but every single one of them is an engine...P&W made the F100, and GE made the F404 and the F101. My suggestion is especially when one number can mean an entirely different thing to proof read your post extra careful.

[camlost]

Whatever shows in editor is bogus. You need to see it in flight. Every tick AJE runs a calculation then change the thrust

[cagataypasa]

It looks like AJE is causing all the parts to dissappear. I am sure(or not) because when I uninstall they come back.

[camlost]

It looks like AJE is causing all the parts to dissappear. I am sure(or not) because when I uninstall they come back.

That is probably a MM problem. I tested with 2.1.4 version. Do you have RF and FAR latest version installed?

[NathanKell]

Here's some redone props you might like.

https://www.dropbox.com/sh/rphsxiwmhxnbp8k/AABFMwFfsJublFMgbvv24visa

Note that it's still for 1.1, before you switched to meters for r0.

The Reno stuff is Dirt_Merchant's work, although I tweaked it some (there were some stats issues).

[Drew Kerman]

Whatever shows in editor is bogus. You need to see it in flight. Every tick AJE runs a calculation then change the thrust

Fair enough, but I just want you to know that's not really helpful for people in the SPH/VAB looking at the stats window and trying to decide which engine to use. Not all of us like to just slap on a part and see what happens. I personally prefer the added challenge of trying to design things right withing the SPH/VAB. This isn't always possible due to various game limitations, like the stats window not being able to show real stats, but still - you can at least use the description field to help differentiate the otherwise-identical-looking (and thus confusing) parts.