Air-breathing/jet engines - what are all the numbers?

[Farrow]

Hi all,

So, I've recently gotten back into KSP, and I have basically no idea what all the numbers mean when it comes to jet engines requirements for intake air, intake power and all that jazz. It seems there used to be a great "jet compendium" but the forum implosion seems to have fed that to the kraken.

Intake airflow, intake size, intake power, intake air (initial/max)... it's all jibberish to me right now. I know I need intakes on my jet aircraft, but my "intake air" resource just constantly goes down. Is that a sign of too few intakes? A lack of speed? Too high? A combination of all of these?

Any help would be much appreciated.

[EndlessWaves]

A combination of all of these?

It means you buffer is reducing.

The IntakeAir resource bar just shows the buffer. The intake area (not shown in game, see wiki) determines how much intakeAir you're getting and the engines determine how much you're consuming (15x as many units as liquidFuel use).

In theory you need a big enough buffer that all engines can draw their required amount per turn, in practice you generally reach the maximum capacity of the intake before that point.

The amount in the buffer goes down with altitude because you have less air 'left over' - the amount the intakes are pulling reduces to be closer to the amount the engines are using.

[vencaslac]

in my experience i have found that a safe way to go is to ensure you have 0.07 intake air for every turbo jet you have... if it drops to 0.06 the engine will flame out... if you have multiple engines say 2 or 3.. if you drop below 0.14 or 0.21 respectively one random engine will flame out... you're in trouble with two since that will put you in a flat spin... with three you might be lucky enough that the middle one will flame out... but yeah correct me if i'm wrong here i will recant this statement but it's 0.07 intake air per turbojet

[Banbite]

The order of which the engines flameout is in the reverse order in which you place them. So the engine you placed last will flame out first, I think. So always place the middle engine last.

And as for the numbers, I aren't sure. The jet compendium has probably imploded and I can't recall all the details. But the amount of intake air generated is dependant of altitude (higher altitude means lower air), speed (the faster you go the more air is pushed into the intake), the intake area which is different for each intake and the angle of attack.

For the engines their isp is only (I think) dependant on the altitude and it's thrust only dependend on it's airspeed. The turbojet has much better high speed and high altitude thrust and isp than the basic jet engine but the basic one is much better at sea level.