Engine Nacelle vs Pre-cooler vs Mk1 Driverless Intake

[Jestersage]

What's the difference between their performance as air intake? Does one work better at lower speed, one work better at higher speed, or is one better overall?

Edited September 20, 2017 by Jestersage

[bewing]

Yes. The nacelle is low tech, and works best at low speeds. The divertless intake works a little better at higher speeds, and holds more fuel. The precooler weighs a lot less, has even better performance, and significantly lower drag.

[AeroGav]

From what I remember,  all 3 of the axial intakes (engine nacelle, diverterless intake, pre-cooler) have very similar drag value - about equal to a mk1 liquid fuel tank.    

@bewing said, different intakes have different air gathering performance.   Some intakes have a very high "static" rating,  and pull in a lot of air even when the craft isn't moving.    As speed increases, all intakes are able to gather more air, but eventually they reach a peak and beyond this, they take in less air the faster you go.    High speed intakes tend to have a worse static rating, but gain more rapidly as speed rises and hit their peak flow at higher speeds.

Most jet engines also increase in thrust (and air consumption) as speed rises,  and have a similar peak after which thrust and air use goes back down.

So,  it's important to match the characteristics of your intake with your engine.    

The Panther engine peaks at Mach 2.5 and stops producing power altogether at mach 3, so it will do fine on any intake.   However, I've had problems running a RAPIER on the supersonic radial intakes.   The air flow drops to zero above mach 3.5, right when the RAPIER gets into its peak,  so you'll get spluttering no matter how many you spam.

The Shock Cone is the most high speed optimised intake.  At high speeds, one shock cone can feed multiple rapiers, (but you might get spluttering at low speed with less than one intake per engine).  

The Adjustable Ramp and Pre-Cooler are not quite so high speed, but are well balanced enough to work with any engine on a one engine per intake basis.   The pre-cooler in particular has a high static rating despite being a high speed design, but on the other hand doesn't hold much fuel.

If you want to test this out for yourself, build a plane with multiple intake types , enable the drag data in the ALT F12 menu,  and fly around with the right click menus pinned in place, taking screenies.

Not moving - 

1. Engine Nacelle wins, flowing 18.9

2. Pre Cooler  flows 12.2

3.  Diverterless flows 6.8

4.  Shock Cone only does 4.5

Low Speed - 

Shock cone only has 60% of the drag of the others, which are all the same 0.90kn of drag. Looks like it's drag got reduced in the last patch.

1. Shock Cone pulls in 96 units of air

2. Engine nacelle pulls in 80

3. Supersonic intake does 77

4. Pre cooler does 68

Mach 2.65  (top speed for Panther, pretty much)

At supersonic, the engine nacelle and supersonic intakes are still the same for drag, but the pre-cooler has about 30% less and the shock cone 30% less again.

Shock cone pulls 31 units

Pre-cooler jumps to second place, with 18.9

Supersonic intake pulls 18.7u

Engine Nacelle falls behind the pack, with just 8u