Ethen Sun

Partially air-breathing engines

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I was thinking about how jet engines work on Earth, since the air is only 21% oxygen, the rest of it (nitrogen) also helps by being heated and accelerated out as exhaust right? I'm assuming Kerbin's atmosphere is not 100% oxygen. If my understanding is right, terrestrial jet engines don't even burn all the oxygen.

What if, in places like Eve, intakes would take in whatever was in the atmosphere and combine it with oxidizer you brought along, therefore using less oxidizer?

Burning LiquidFuel as normal, I assume.

Edited by Ethen Sun
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53 minutes ago, Ethen Sun said:

I was thinking about how jet engines work on Earth, since the air is only 21% oxygen, the rest of it (nitrogen) also helps by being heated and accelerated out as exhaust right? I'm assuming Kerbin's atmosphere is not 100% oxygen. If my understanding is right, terrestrial jet engines don't even burn all the oxygen.

What if, in places like Eve, intakes would take in whatever was in the atmosphere and combine it with oxidizer you brought along, therefore using less oxidizer?

According to the game's code, once you use a basic "intake" to feed your engines, the atmosphere is 100% of that resource. But if you use an atmospheric harvester module then the proportion of resource received can be anywhere < 100% as it should be.

There's a prominent mod out that perfectly answers the question of Eve. It introduces Explodium Vapor to Eve and suitable worlds in planet mods, and needs you to burn Oxidizer with it.

As the following link reveals, not every atmospheric resource combusts if you mix it with Oxidizer. Some things even burn better if you mix with toxic chemicals like Fluorine.

40 minutes ago, goduranus said:

Here's a kicker, what if on Jool, you don't even burn fuel, but take hydrogen from the atmosphere and combine it with oxidizer?

 

Not the same but here's a cool read:

http://www.wickmanspacecraft.com/marsjet.html

Problem. Although Hydrogen is a 'perfect' propellant, its density is far too low for you to be able to gather up more of it than you're burning at a given time if that's your main propellant. It will only make sense to fuel scoop Jool's atmosphere while trying to aerocapture, or fuel scoop a far more powerful propellant added by a mod that adds advanced tech. Such mods include Karbonite (it's like SolidFuel though), KSP Interstellar Extended and Far Future Technologies.

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"Air augmented rocket" is the concept being described. Atmosphere is used as reaction mass but not combusted, which increases specific impulse. 

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I think Porkjet's nuclear engines mod has/had a nuclear tuturbojet engine, which is similar to what you're thinking of. Rather than use fuel and oxidizer to heat the atmosphere as a reaction mass, it uses (surprise) a nuclear reaction.  This would conceivably provide thrust for as long as your nuclear fuel lasts (well, until the engine needs to be rebuilt anyway). 

 

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2 hours ago, Red Iron Crown said:

"Air augmented rocket" is the concept being described. Atmosphere is used as reaction mass but not combusted, which increases specific impulse. 

Great answer. :) Mk2 (and I think Mk3) Stockalike Expansion has a couple of these..

1 hour ago, natsirt721 said:

I think Porkjet's nuclear engines mod has/had a nuclear tuturbojet engine, which is similar to what you're thinking of. Rather than use fuel and oxidizer to heat the atmosphere as a reaction mass, it uses (surprise) a nuclear reaction.  This would conceivably provide thrust for as long as your nuclear fuel lasts (well, until the engine needs to be rebuilt anyway). 

PorkJet's Atomic Age, Mk2 (and Mk3) Stockalike Expansion, KSP Interstellar, and I believe Eskandare Thermonuclear Turbines all have nuclear jet engines like this.

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4 hours ago, Red Iron Crown said:

"Air augmented rocket" is the concept being described. Atmosphere is used as reaction mass but not combusted, which increases specific impulse. 

Yeah, I'd love to see an air-augmented engine. Or, even better -- a setting or module that allows existing intakes to increase the thrust and specific impulse of rocket engines. Maybe an Exhaust and Airflow Diverter, a 1.25-m module you place between a 1.25-m intake and a 1.25-m engine to combine the airflow with the rocket exhaust.

I'd love even more to see an aerodynamics update that allows you to build your own intake to combine with rocket exhaust but that's just wishful thinking.

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