Modular Jet Enginges, alternative air intake system

[Hector_919]

Currently, the Jet engine system in KSP works just like the Rocket engine system: move whatever the engine needs to it with pipes, no matter from where the fuel is pumped. While this makes perfect sense for rocket engines that only need Fuel and Oxidizer, the idea of Pumping intake air across an entire airplane to the Jet engines made the physics student inside me twitch uncontrollably. In reality, the air intakes are part of the engine and pumping air through pipes doesn't really work.

I'm not sure if it would be better to design jet engines seperately, save them as a whole jet engine and add them to your plane similar to subassemblys that you can't edit (which would allow engines to work like a single object, saving CPU power and preventing eventual wobbling) or just build them like anything else in the SPH/VAB - but now let's get to the actual engine concept:

My idea would be to construct each engine out of its single components: intake, compressor, combustion chamber and so on.

In order to simulate the engine behaviour, the airflow inside each engine will be described with four properties: air pressure, air temperature, airflow speed and the amount of oxygen/oxidizer. Every engine component will change these four values acording to its purpose and depending an 'how the air arrived here':

Intakes will basically provide the air 'as is', fan compressors will increase pressure behind them and decrease the pressure in front of them, bring the airflow speed closer to a target value (based on their rotation speed) and increase air temperature slightly, combustion chambers drastically increase pressure and temperature, increase airflow speed and decrease oxygen amount while burning liquid fuel and so on.

If radial intakes are needed, a radial intake body part that allows to use the air provided by them would be an idea to make them compatible with the new system.

Engine construction begins with a combustion chamber: it determins the radius of the engine (if we get engines of different diameters) as well as its type (Turbojet, Ramjet or Scramjet - each with different behavoiur in different altitudes / at different velocities). (nearly) all combustion chambers need their intake air compressed, and if the engine temperature gets too high precoolers would finally have an effect worth the name 'precooler'.

additional parts allowing a wide variety of engines would be:

-afterburners

-oxidizer injectors (quite self-explainatory)

-thrust vectoring nozzles

I know that this system may be quite complicated, but KSP itself also requires some explaining, and as tutorials are already planned and the description system present in SPH/VAB can help a lot, And for beginners some basic example engines should allow them to get used to the engine system.

If Engines are to be built seperately, allowing a testing function where you can test engines in a pressure tunnel would also be an Idea to help people build the engine they need.

I'd really appreciate hearing your opinion about this

Hector

[S4qFBxkFFg]

I definitely think the air-breathing jet engines could be improved, and made a thread about it: http://forum.kerbalspaceprogram.com/threads/72881-Changing-the-way-air-breathing-jet-engines-are-constructed

I would be perfectly happy with something more like you described, but maybe that's too complex?

[Scoundrel]

I completely agree with you in principle. Unfortunately your suggestion would be better put as a mod based around 0.5 and 1m engine casings and have sliders that modify the core via parameters for inlets, bypass ratios (for turbofans), spools, compressors, nozzles, etc. that generate an output engine - though some folks will argue that it's not realistic enough, and they'd be right since the mass flow calculations for a turbine are complex and well beyond the scope of a video game... and it still doesn't solve the issue people have with aircraft engines in the game in general.

I suspect sticklers wouldn't be happy unless jet engines were radially mounted, were only able to have ducting parts connect to them, and the ducting ended in a single intake. This would be the ultimate in "conceived" realism... but this is a comic book game about little green astronauts living on a planet that's as dense as (or denser than) the densest element in existence.

A better cognitive rationalization would be to simply have jet engines overheat at certain velocities (IRL this is the inlet temperature, and is why fighter jet engines don't do mach 5 - read up on the MiG-25/31 for how the Soviets dealt with that particular engineering solution to get interceptors to go Mach 3; there's not much on the SR-71 as the J58 is still classified for some reason), and have air intakes with a slider (like engines now have a "limiter") that allows them to have up to 10x their current intake value, but their drag goes up a corresponding amount, making spamming pointless. Perhaps the devs might consider something like that as it doesn't involve a major redesign of the parts or any additions.

Now, if the fact that the air intake going through a fuel tank still makes you go "bleah" like it does me, but you lack my ability to embrace denial and just pretend that there aren't any problems, just use empty fuselage pieces and pretend they're ducting, because, really, that's what ducting is: holes in a fuselage.

[Hector_919]

I definitely think the air-breathing jet engines could be improved, and made a thread about it: http://forum.kerbalspaceprogram.com/threads/72881-Changing-the-way-air-breathing-jet-engines-are-constructed

I would be perfectly happy with something more like you described, but maybe that's too complex?

It probably is - that's why I've asked for other people's opinions. If we start from what I've described here, your system basically welds the turbine and a compressor to the combustion chamber. It's a little less complex that what I've posted here, but it looks very similar. I personally would prefer being able to choose turbine and second-stage-compressor by myself, though.

I completely agree with you in principle. Unfortunately your suggestion would be better put as a mod based around 0.5 and 1m engine casings and have sliders that modify the core via parameters for inlets, bypass ratios (for turbofans), spools, compressors, nozzles, etc. that generate an output engine - though some folks will argue that it's not realistic enough, and they'd be right since the mass flow calculations for a turbine are complex and well beyond the scope of a video game... and it still doesn't solve the issue people have with aircraft engines in the game in general.

You're right - I've seen some of these mass flow calculations, and they're just sick - sorry for all the sticklers, but at some point stuff gets too complicated for everyone, some simplification will have to do.

The problem with determining every value of the engine parts by the use of sliders to me sounds like allowing to set the ISP and maximum thrust of Rocket engines - there would be one set of settings for the most OP engine ever, and no need to optimize for different purposes. Having different compressors/intakes/combustion chambers/nozzles allows not only some basic balancing to prevent people from creating said OP jet engine, the part descriptions would also help people by letting them know what a certain part is most useful for. Just being given a bunch of sliders to play with would probably have me end up like this.

I can understand that you would rather like to see a Mod for this instead of it being added to vanilla KSP, and at the moment I don't know what I'd prefer - I'd be happy with any of them.

I suspect sticklers wouldn't be happy unless jet engines were radially mounted, were only able to have ducting parts connect to them, and the ducting ended in a single intake. This would be the ultimate in "conceived" realism... but this is a comic book game about little green astronauts living on a planet that's as dense as (or denser than) the densest element in existence.

My first concern when posting this rather was a way to allow the creation of engines optimized for certain situations rather than realism - and the way people optimize engines in reality seems to work quite well.

A better cognitive rationalization would be to simply have jet engines overheat at certain velocities (IRL this is the inlet temperature, and is why fighter jet engines don't do mach 5 - read up on the MiG-25/31 for how the Soviets dealt with that particular engineering solution to get interceptors to go Mach 3; there's not much on the SR-71 as the J58 is still classified for some reason), and have air intakes with a slider (like engines now have a "limiter") that allows them to have up to 10x their current intake value, but their drag goes up a corresponding amount, making spamming pointless. Perhaps the devs might consider something like that as it doesn't involve a major redesign of the parts or any additions.

I don't think a velocity-based overheating would be such a good idea, since it would quite likely lead to the engines of SSTOs blowing up on atmospheric reentry - and this Suggestion was aimed at allowing to create specialized engines, not an overhauled overheating system (which would by the way also make sense).

Now, if the fact that the air intake going through a fuel tank still makes you go "bleah" like it does me, but you lack my ability to embrace denial and just pretend that there aren't any problems, just use empty fuselage pieces and pretend they're ducting, because, really, that's what ducting is: holes in a fuselage.

I'll try. *twitch*