Inline intakes the new intake spam?

[Foxster]

Was just messing about with the Mk1 Fuselage - Intake, Engine Nacelle and Engine Pre-cooler and they all seem to have the same effect: They raise the RAPIER's air-breathing ceiling from 20km to 30km. This is extremely useful for SSTOs.

So, are they there to replace the intake spam of 0.9?

[ZooNamedGames]

Sorry mate- try as you like. Air hogging died with all prelease hype.

[Jouni]

It looks like airhogging is still possible to some degree. My test plane did a quick 40-degree climb in airbreathing mode and reached an apoapsis of 103 km. The engines flamed out at 29.5 km.

[Michaelo90]

It looks like airhogging is still possible to some degree. My test plane did a quick 40-degree climb in airbreathing mode and reached an apoapsis of 103 km. The engines flamed out at 29.5 km.

The engine flamed out at the same height for me with just one shock cone. Air hogging isn't possible.

[GoSlash27]

I'm able to keep my engines lit with just one shock cone or 2 XM-G50s per engine. While more intakes may extend the ceiling at which the engines stay lit, they don't seem to be adding any thrust, just mass and drag.

Therefore it makes more sense to use *enough* intake and no more.

Best,

-Slashy

[Foxster]

I didn't mean that more intakes help, I have found that more than one intake doesn't help. However, using a 'Mk1 Fuselage - Intake', 'Engine Nacelle' or 'Engine Pre-cooler' in addition to an intake does seem to help. Seemed to allow my test SSTO to go from 20km to 30km on jets.

[Jouni]

The engine flamed out at the same height for me with just one shock cone. Air hogging isn't possible.

The effect seems to be marginal. With the intakes in the pre-coolers closed, the engines still lasted until 29.5 km, but thrust went down a bit earlier. The apoapsis was 100.5 km instead of 103 km.

[hazens1]

I seems each jet engine has a hard altitude cutoff and having "just enough" intake air will get you there. I have not tested the basic engine and my numbers may be off, but the turbo-jet has a 25.5k ceiling and the rapier has a 29.5k ceiling and no matter how much intake air you have they will "fail combustion" at these altitudes.

[arq]

In pre-release, jet engines had velocity curves. More intakes allowed one to have more thrust at altitude without flaming out. In 1.0+, jets have both velocity and altitude curves (and the velocity curves are different than before). The RAPIER gets a 9% thrust modifier from altitude at 20km (though the velocity curve can make this number higher) and it decreases exponentially above that height (3.3% at 25km and 1.2% at 30km). Thrust also decays linearly to zero from Mach 5.5 to 6.

In pre-release, the turbojet had good thrust up to 1800m/s or so and at any altitude (provided enough intakes, and it didn't stop thrusting until 2200m/s). With the 1.0 changes, RAPIERS (the highest/fastest jets) simply provide very little thrust above 20km, and even then only up to just over Mach 5.5 (anyone know how fast that is at 20km on Kerbin?). This also means that less air is required. Engines will fall off to diminutive thrust well before flameout, usually. If you have multiple engines and they flameout together, that means that they are simply going too high/fast to thrust any longer. If they flameout asymmetrically, that can be solved with more intakes. I have never flamed out with 2 intakes per engine, and usually 1 does well enough. Intake spam is no longer necessary to extract the full performance from engines.

[Quiana]

In pre-release, jet engines had velocity curves. More intakes allowed one to have more thrust at altitude without flaming out. In 1.0+, jets have both velocity and altitude curves (and the velocity curves are different than before). The RAPIER gets a 9% thrust modifier from altitude at 20km (though the velocity curve can make this number higher) and it decreases exponentially above that height (3.3% at 25km and 1.2% at 30km). Thrust also decays linearly to zero from Mach 5.5 to 6.

In pre-release, the turbojet had good thrust up to 1800m/s or so and at any altitude (provided enough intakes, and it didn't stop thrusting until 2200m/s). With the 1.0 changes, RAPIERS (the highest/fastest jets) simply provide very little thrust above 20km, and even then only up to just over Mach 5.5 (anyone know how fast that is at 20km on Kerbin?). This also means that less air is required. Engines will fall off to diminutive thrust well before flameout, usually. If you have multiple engines and they flameout together, that means that they are simply going too high/fast to thrust any longer. If they flameout asymmetrically, that can be solved with more intakes. I have never flamed out with 2 intakes per engine, and usually 1 does well enough. Intake spam is no longer necessary to extract the full performance from engines.

A little helpful support on asymmetric flameout here: http://forum.kerbalspaceprogram.com/threads/119607-Airbreather-fuel-flow-logic?p=1909169&viewfull=1#post1909169

As indicated, Intake spam certainly does not work, engines perform much in the same manner as the RL versions do (albeit significantly higher thrust values). Just check your intake placement order to ensure each engine is fed correctly and you won't have issues with flameouts in anything but a symmetrical/staged pattern. If anything, the drag from additional intakes will significantly hurt you compared to actually gunning for a little under the max height to air ratio.