Airhog IRL

[Lohan2008]

I was wondering what is the max number of air intakes on a real life airplane/rocket ?? Pics plz !

[PDCWolf]

There's no "airhog" because all the "intakes" have to follow a logical path as straight as possible to the engine.

On top of that, having to make the shapes of the intakes add weight to the plane, so everything is basically on a "just what is needed" basis.

In ksp, on the other hand, intakes -mistakenly- don't have to follow any logical path to the engine and can be placed anywhere. On top of that they can be stacked and clipped. ON TOP OF THAT yet again, jets are way too op both in thrust and efficiency.

[lammatt]

35.9km with a Mig25 if u are talking about flight height

http://en.wikipedia.org/wiki/Flight_altitude_record#Jet_aircraft

[MockKnizzle]

Lockheed Martin F-35 Lightning II - 2 intakes, one Pratt & Whitney F135 afterburning turbofan.

Boeing 747 - 4 intakes, 4 Pratt & Whitney PW400 high-bypass turbofan engines.

North American Aviation XB-70 Valkyrie - 2 intakes, 6 General Electric YJ93 turbojet engines.

It seems that the highest ratio of intakes to engines you ever see in real life is 2:1.

[Lohan2008]

Thanks for the info KSP. That MIG 25 sure does have BIG intakes.

[BubbaWilkins]

Actually, it's a 1 to 1 ratio. One induction stage for each combustion stage. The number of intake holes feeding those induction stages doesn't really matter as long as they allow enough air to be ported to the induction stages.

[Tiron]

There's no "airhog" because all the "intakes" have to follow a logical path as straight as possible to the engine.

On top of that, having to make the shapes of the intakes add weight to the plane, so everything is basically on a "just what is needed" basis.

This is one of the big things hampering Hybrid Jet/Rocket designs for SSTOs: You end up with a LOT of extra weight, if nothing else the ducting for the intakes, but in a lot of cases the engines themselves as well.

One thing you'll note is that planes designed to go supersonic tend to have fancier intakes with fancier ducts, up to and including variable aspect intakes (Moving ramps, moving cones, that kind of thing.) This is because most jet designs don't handle supersonic intake flow speeds well at all, and it has to be slowed down before it can be fed into the engine using a number of techniques, most of which involve particular shaping of rather long ductwork. The 'big circular opening' you see on airliners only really works at subsonic speeds.

This gives a decent view of the F-35's ductwork. You can see it in green leading back from the intakes into the front of the engine, going through a weird loop to get around the vertical lift fan (the -A model has a a fuel tank where the fan goes on the -B.) On a real aircraft, that's what you have to do: have an uninterrupted duct from the intakes to the engine(s) they service. Something like attaching it to a cubic octagonal strut or putting a cargo bay right behind them would, realistically, cut off the air flow.

In KSP the air just magically flows to the engine regardless of where the intake is, which is one of the main things that allows airhogging. Frankly the entire 'intakeair' system is kind of a dirty hackjob to make the engines better balanced than they were, as was changing rockets to bipropellant (they used to burn just liquidfuel, so you could run jets and rockets off the same tanks. I used to mix jets in on the first few asparagus stages on my rockets back then.)

It's also why we get flameout spins like we do: When one engine flames out, the intakeair it was consuming magically transfers to the other engines, which keeps them alive. On an even-engined plane, this puts you in a spin unless they're mounted very close to the centerline. Realistically, the output of each intake should be designated for a particular engine and unable to transfer to another if that one shuts down, meaning all engines would flame out at once. There'd also realistically need to be a logical flow path through parts with sufficient capacity, and very limited amounts of bending. Neither of these is possible with current game systems.

[allmhuran]

The thing about airhogging in KSP is that in KSP the intake is represented as a part, and you can clip parts on top of themselves to "hog" intake air.

But of course, in real life an air intake is a *hole*, and it doesn't make any sense to talk about stacking holes on top of each other.