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[1.12] Explodium Breathing Engines v1.8.0: "Jet" engines for use on Eve and Jool [10 OCT 2021]


Gordon Fecyk
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36 minutes ago, Hohmannson said:

Yeah. but stock intakes (and EBE's) don't. Module in them has no animations attached

True. They might have been assumed to require that module. You don't exactly hear of Microsoft exces using Apple products or vice versa so I haven't exactly been out there trying out my rival's mod (yes, you :D  @Gordon Fecyk ) and helping him make his mod better. If he asks for advice I'll give as far as I know, though.

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3 hours ago, OhioBob said:

I'm just waiting to see how Gordon gets off Nara.

That's coming!

There's also another surprise for Nara that I won't spoil. It appears, unlike Jool (Stock or JNSQ) or Lindor with their really low atmospheric densities but high pressures, Nara has high densities as well. This lends itself well for certain applications not possible elsewhere.

6 hours ago, Hohmannson said:

I removed ModuleAnimationGroup because wasn't sure what it was doing(needed for action groups?), and added the above line in ModuleResourceHarvester. The harvester appeared activated on launch, I immediately received vapour and was able to fly. Also it works for ModuleResourceConverter if needed.

There was one other complication in that the harvester seems to need restarting if transitioning from space to atmosphere. I'd get resource rates of "n/a" unless I stopped and restarted the harvester. I'll have to experiment with this once I'm done the JNSQ Exploration series.

This isn't as much of a problem for a Space Center starting on a world with explodium in the air though, as the resource is available immediately when the craft spawns. 

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2 hours ago, Gordon Fecyk said:

harvester seems to need restarting if transitioning

Reproduced and fixed, made it stuck in activated state forever. Tested on Jool, works as intended, no need to re-enable the intake.

@PART[airScoopExL,airScoopExV,CircularIntakeExL,CircularIntakeExV,shockConeIntakeExL,shockConeIntakeExV,IntakeRadialLongExL,IntakeRadialLongExV,miniIntakeExL,miniIntakeExV,ramAirIntakeExL,ramAirIntakeExV,turboFanSize2Ox,turboFanSize2OxL]:AFTER[ExplodiumBreathingEngines]
{
	@MODULE[ModuleResourceHarvester]
	{
	%IsActivated = true
	%AlwaysActive = true
	!StartActionName = pwn
	!StopActionName = pwn
	!ToggleActionName = pwn
	}
	!MODULE[ModuleAnimationGroup]{}
}

 

Edited by Hohmannson
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@Hohmannson If you have a GitHub account and haven't already, go ahead and fork the source, make these changes, and do a pull request. This way you're listed as a contributor to the original source.

If possible, try to do these without needing Module Manager. In the current release, Module Manager is only needed for changes related to RealPlume and Ferram Aerospace, where it's already a requirement. I'd like this add-on to continue to work in Stock without it.

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On 9/12/2021 at 9:00 PM, Gordon Fecyk said:

without needing Module Manager

OFC i can edit files directly. This patch was for demonstration purposes. I just created GitHub account, it will take some time.

upd: PR tested and submitted.

Edited by Hohmannson
upd
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  • 4 weeks later...
On 9/12/2021 at 3:25 PM, Hohmannson said:

upd: PR tested and submitted

Sorry for the delay - I just got around to updating the repository and these updates look good, and also look like they'll work without Module Manager. Thanks!

 

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I integrated Hohmannson's changes and, while the extra button looks confusing, his changes did work as designed. The repository has these and other changes, and is usable for now.

I'm working on adding Waterfall effects to the next release. I already have the Hades and Dorothy engines working with this, mostly cloning the Stock Waterfall Effects examples. Once that's done I can release it.

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  • 3 weeks later...

I have a feature request:

Would it be possible to have jets that breath an inert atmosphere? It's not as dumb a question as it sounds: your reaction mass doesn't have to contribute anything to your heat generating reaction, it just has to be heated and expand. So you can carry both fuel and oxygen onboard and mix them in the combustion chamber, like a rocket, but still get better specific fuel consumption than a rocket (because you're still using the local atmosphere for reaction mass instead of just the stuff you're burning).

I call this concept the COuGHjet: "Completely Onboard GHuel"

It would be nice to have oxygen / explodium breathing modes for atmospheres with appropriate content, but just having the COuGH mode available everywhere would be nice, without further optimization.

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3 hours ago, jwbrase said:

Would it be possible to have jets that breath an inert atmosphere? It's not as dumb a question as it sounds: your reaction mass doesn't have to contribute anything to your heat generating reaction, it just has to be heated and expand. So you can carry both fuel and oxygen onboard and mix them in the combustion chamber, like a rocket, but still get better specific fuel consumption than a rocket (because you're still using the local atmosphere for reaction mass instead of just the stuff you're burning).

You could do that but it might actually hurt rather than help.  Wouldn't know without doing the math.

There's more involved in it than this, but specific impulse is largely proportional to SQRT(T/M), where T is the combustion temperature and M is the exhaust gas molecular weight.  So to get the best performance we want high temperature and low molecular weight.  When we add an inert gas, we're lowering the temperature.  That's because the heat generated by the combustion of the fuel and oxidizer must heat up the inert gas.  Lowering temperature will also increase the molecular weight because there is less dissociation at lower temperature.  And depending on what the inert gas is, that could also increase molecular weight.  So an engine that adds an inert gas will unquestionably produce a lower specific impulse than one that doesn't.  But the question is, does the extra reaction mass more than make up for the lower specific impulse?  I don't think there's a one size fits all answer to that question.

(edit)  We would also need to compress the inert gas so it has adequate pressure to force it into the engine.  That means extra machinery, and hence, more mass and cost.  So that also needs to be weighed against any benefit we might get in performance.  
 

Edited by OhioBob
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5 hours ago, jwbrase said:

Would it be possible to have jets that breath an inert atmosphere?

I think the Nuclear Jet in Near Future Technologies is what you're looking for there, using nuclear power to compress and expel inert gasses. This sounds like a closer match to the theoretical / fictional caterpillar drive from The Hunt for Red October

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5 hours ago, jwbrase said:

COuGHjet

Air-augmented rocket. Useless in oxygen-less atmosphere, sadly. Other set-ups(heating intake atmo with burning fuel) have questionable performance compared to an electric propeller running on fuel cell. Unless, of course, it runs on unlimited heat of reactor instead of fuel. Grab your nuclear jets in Near Future Aeronautics, CEDA Aeronautics, Spacetux Recycled Parts, SXT. Electric propellers in Firespitter, KAX and Breaking Ground DLC.

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2 minutes ago, Gordon Fecyk said:

I think the Nuclear Jet in Near Future Technologies is what you're looking for there, using nuclear power to compress and expel inert gasses. This sounds like a closer match to the theoretical / fictional caterpillar drive from The Hunt for Red October

Yes, that is one way of building a jet that will work in an inert atmosphere, but I'm actually proposing something more low tech: you just have a normal jet engine, and you squirt both fuel and oxidizer into the combustion chamber. Your compressor draws in inert ambient air, and forces it back into the combustion chamber, where it mixes with and is heated by the burning fuel-oxidizer mixture. The hot ambient air / exhaust mixture is then expanded through your turbine (*but see below), powering the compressor, and then expanded out through the back of the engine, producing thrust. Other than the oxidizer injector in the combustion chamber, this is just a normal jet engine. Keep in mind that 80% of our air here on earth *is* inert, and serves only as working fluid in a jet engine, having nothing to do with burning fuel. The 20% oxidizer that God was so kind as to mix into our atmosphere means we don't have to cart oxidizer along in onboard tanks, but in an environment where that is missing, the operation of a jet engine could be largely the same, just with different supply tankage and plumbing.

(*In reality, you might well structure the engine differently, especially if you expected it to operate exclusively in inert atmospheres, but the main point is that a existing oxygen-breathing design could be changed into a "COuGHjet" just by adding an oxidizer injector to the combustion chamber. It might not be the most efficient way to do it, but it would work on Venus or Mars or Titan (or Duna) with minimal changes). 

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23 minutes ago, Hohmannson said:

Air-augmented rocket. Useless in oxygen-less atmosphere, sadly.

Well, then it's not what I'm calling a "COuGHjet", as the fuel (that is the fuel-oxidizer mix) is not completely on-board.

A ducted rocket, where no burning of any kind happens downstream of the rocket chamber, would be a type of COuGHjet, but isn't what I'm asking for here.

Quote

Other set-ups(heating intake atmo with burning fuel) have questionable performance compared to an electric propeller running on fuel cell. 

Heating intake atmo with burning fuel is what I'm proposing, and at low speed, yes, it's going to be outperformed by a propeller, and the electrical efficiency of a fuel cell probably pushes the range at which the propeller is a better choice up to higher speeds (compared to a propeller driven by reciprocating engine with oxidizer supplied from on-board, or by a COuGHjet turboprop). But that's actually no different from the case for regular jets in an oxygen atmosphere, if you allow the fuel cell to use atmospheric oxygen. But at some speed (at latest Mach 1, for realistic propellers, and probably well before that), the jet will start outperforming the propeller.

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1 hour ago, OhioBob said:

You could do that but it might actually hurt rather than help.  Wouldn't know without doing the math.

There's more involved in it than this, but specific impulse is largely proportional to SQRT(T/M), where T is the combustion temperature and M is the exhaust gas molecular weight.  So to get the best performance we want high temperature and low molecular weight.  When we add an inert gas, we're lowering the temperature.  That's because the heat generated by the combustion of the fuel and oxidizer must heat up the inert gas.  Lowering temperature will also increase the molecular weight because there is less dissociation at lower temperature.  And depending on what the inert gas is, that could also increase molecular weight.  So an engine that adds an inert gas will unquestionably produce a lower specific impulse than one that doesn't. 

If reaction mass is not an on-board resource, then the ideal case, performance wise, is to be pushing against an infinite block of solid reaction mass, and for our exhaust velocity to match our forward velocity. The spherical cow for this case is a wheeled rover on an infinite flat plane of infinite rigidity. In real life, this is very well approximated by any wheeled vehicle sittting on the ground, and in KSP, given that celestial bodies are on rails, I'm pretty sure that this ideal case is met pretty much exactly for rovers. The reason this is the ideal case is that if you are pushing against a finite mass (with your exhaust velocity thus having to be a bit greater than your forward velocity to conserve momentum), then some of the energy from your fuel ends up in the backwards motion of the exhaust stream rather than the forward motion of your vehicle. Of course, with any engine using a fluid as a reaction mass, you're never going to achieve this ideal exactly, but you still want as much reaction mass as you can get if you're sourcing it from off-board.

Quote

(edit)  We would also need to compress the inert gas so it has adequate pressure to force it into the engine.  That means extra machinery, and hence, more mass and cost.  So that also needs to be weighed against any benefit we might get in performance.  

You only need machinery to force air into the engine in the low speed regime, which is where you benefit the most from very high mass flow. At high speeds, ram pressure suffices. In fact, at very high speeds, ram pressure is your enemy: most of the thermal energy in your combustion chamber at high speed comes from ram compression and the fuel you're burning contributes relatively little.

Given that your engine materials only remain solid up to a certain temperature, this places a limit on your maximum speed: once compression heating brings the gas stream up to the thermal limits of your engine, you can't add any fuel without melting the engine, so the engine can no longer provide any thrust. Now, if you had some super-material that could remain solid up to insane temperatures, you'd still have a problem: the temperature in your combustion chamber has to be less than the dissociation temperature of the products of whatever reaction you're using to provide heat (for kerolox, that will be the dissociation temperatures of water and CO2), or your fuel mixture won't actually burn until it's on the way out the tailpipe (so that some/all of the heat added by burning the fuel doesn't expand the airstream in time for the exhaust nozzle to turn it into forward motion of the aircraft).

Scramjets solve this problem by slowing down the incoming airstream less, so there's less ram compression. SABRE (the real-life inspiration for the RAPIER) solves this by using LH2 as fuel, and using the LH2 to cool the intake air as it's compressed (actually it's a bit more complicated than that, but that's the general idea).

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