Ducted fans or other non-airbreathing propellors

[NecroBones]

Something I'd like to see added, is an option for fuel-efficient atmospheric propulsion in atmospheres without oxygen. Duna and Eve would be a lot easier to explore if we could have propellers or ducted fans (or some sort of turbofan) that run on liquid fuel +oxidizer. These could be a lot less powerful than jet engines, but a much better atmospheric option than rockets.

Sorry if this has been suggested before. But it's something that came to mind while planning planetary expeditions. Right now, Laythe is the only place worth taking aircraft.

EDIT: Now I see this in the list of "already suggested" items. Though in there, one of the links doesn't work, and the other is suggesting electric propulsion. My suggestion is similar but not identical. I'd rather have a fueled, ducted fan than an electric propeller.

Edited March 27, 2014 by NecroBones

[Red Iron Crown]

Why not both? A lightweight, electric unit for small, long endurance drones and a fueled version for heavier lifting/higher speeds.

[NecroBones]

Why not both? A lightweight, electric unit for small, long endurance drones and a fueled version for heavier lifting/higher speeds.

Yes, that would be even better.

[DoctorCruz]

Why not both? A lightweight, electric unit for small, long endurance drones and a fueled version for heavier lifting/higher speeds.

A electric powered prop/engine for exploring Duna and/or the various Kerbol system moons? +1. I really want this now that you bring it up. When the ARM pack comes out, the Ion engines will be beefed up, so you could easily use those to power a plane on duna.

[kellven]

Propellers done right is a lot harder than you think; especially when you have to rewrite the atmosphere system to have coherent densities so you don't have an invariant mach velocity like we do now. They also have absolutely no "power" relation to jet engines, it's comparing bananas and pineapples. They also really aren't that useful for spacecraft unless you prefer a stately, dignified crawl to orbit.

All that said, yes you can have them, I had a 32m rotor helicopter flying around before they gave us the partmodule catastrophe. Took ages to ascend to 10km, and balancing propellers/rotors against "Squad math" is an exercise in futility. They can, and do, fudge the numbers with rockets and even jets, but props and rotors require an actual coherent physics system underneath.

[PDCWolf]

I think the problen with electricity is that you can just slap a few batteries and a few solar panels and fly the thing forever. I wouldn't mind some sort of electric propulsion system if it was correctly balanced.

Any other form of "traditional" propulsion is ok, as long as it is balanced, turbojets are already op as it is.

[kellven]

If I remember correctly from when I was "foolin wit coptas", my working test models were a coaxial version of the Mil-12 rotor/plant, and the same for the ATR 72.

The problem with conversion to KSP was that the thrust on the ATR had to be scaled up(completely screwing conservation of everything) in order for it to make any sense compared to the rockets and jets, but there was a more or less constant scale factor I found for translating real thrust to KSP thrust. The helo just used the raw computed thrust values however, and was still able to "bob" up to around 20km carrying a Rockomax X200-32. No real world helicopter can do that, but I put it down to the size scaling of kerbin itself, having modeled the powerplant as a brushless dc "fuel only" motor unaffected by altitude, and being a cobbled together alpha job.

I have absolutely no idea where fractal got the numbers for interstellar, but he/she assumes battery charge is in kW, you have to realize that the Mil-12 used FOUR D-25 engines putting out 4.8 MW each ~= 19200 "electric charge" per second in game, or almost draining 5 Z-4K batteries for 1 "mass" per second using batteries as fuel. That's 1067 Gigantor XL's to keep it stable, for a total of 374 mass not even including the powerplant or rotor yet. Seeing as the max takeoff weight for the Mil 12 was only 105 tons, and only made 2.2 km with 40 tons, one could never, ever, even come close to having a solar powered lifting copter that flies forever like PDC was suggesting was so easy. Propellers and wings won't help a bit either, as the numbers just aren't even close, and an aerofoil is an aerofoil.

If there's anything to be concerned about, it's the completely nutzor scaling on the ion engines that make them able to be used this way, but that's completely stock Squad product. It's actually rather difficult to mod in anything that's more screwball than the stuff we're given in the base game.

The other issue is size. The coaxial ATR equivalent had some issues with ground clearance, but you have to realize:

That's 2 of the same powerplants just below the rotor assembly.

<note, not to be confused with this way back in the day using DYJ stuff and bigtrack I think it was>

In KSP, it became this at ~50 tons total, doing 106 at 2km, which is actually pretty darn close to the specs on the Mil-12.

<seems no better images of the actual engine size size survived from 2012 on imageshack, sorry>

Not that large of a payload, but it made the launchpad go cry in a corner.

Looking back, I really did have a lot more fun modding all that crazy stuff in than I do playing KSP now. Never mind sending Moe's bar and an IHOP to the Mun.

[Nuke]

you can already do fans with the current part modules, you just cant animate the rotor (without firespitter). but thats just a basic animation issue.

[kellven]

No you can't. A jet engine is not a ducted fan, they just don't operate or perform anything like the other.

--Ducted fans and Rotors operate at near 0 axial velocity, ie they hover very efficiently, and have huge static(take/liftoff thrust), but putter out very quickly as axial airspeed increases. It's a general range of 0-0.3(or 0.15) mach they work in.

--Propellers operate in the 0.3-0.8 mach range, they don't have the static thrust, but they don't putter out until you hit transonic velocity(they have a nice "cruise" curve).

--Jets(all the atmospheric engines we have now) are generally designed to operate in the transonic(0.7+ mach) range efficiently, they also add fuel mass to the efflux, which drastically changes the equations, and have squat all for static thrust.

--Propulsive efficiency depends far too much on current airspeed to make any general comparison, but jets typically have a very very narrow band of efficiency, while propellers have a much wider curve; and simply by the fuel mass addition, lose out regardless.

Simple graphic, turboshaft means propeller, fans/rotors are another curve before that.

We've had things that LOOK like propellers, etc for years via mods; however, they don't BEHAVE anything like propellers. Even with the addition of the jet engine modules, you will never be able to tweak the cfg files to make them behave anything like propellers; the code just doesn't contort that way, never mind autorotation.

Edited April 7, 2014 by kellven

[Anthlon]

I think that we all can agree with one, we would like to utilize the density of other non-oxygen atmospheres, lets come with some type of "cheap" propulsion to use wingsail there.

[technicalfool]

I think the problen with electricity is that you can just slap a few batteries and a few solar panels and fly the thing forever. I wouldn't mind some sort of electric propulsion system if it was correctly balanced.

Any other form of "traditional" propulsion is ok, as long as it is balanced, turbojets are already op as it is.

Meanwhile, back in the real world, that's exactly what the latest solar-powered drones and aircraft are aiming at. 24 hours of power, with a long glide during night time.

[Random Tank]

This is why I love the Kethane Jet, it acts like an any-atmosphere jet engine, yet is balanced as you have to mine the fuel and it overheats after a while on full thrust. It makes no sense though

Though I think that any-atmosphere propulsion makes Eve very easy to return from...

[Anton P. Nym]

Though I think that any-atmosphere propulsion makes Eve very easy to return from...

For electric-driven ducted fans, though, it'd be simple to keep the thrust fairly low and have a steep fall-off of I(sp) with air pressure to prevent it from becoming a default Eve-killer.

-- Steve

[Nuke]

No you can't. A jet engine is not a ducted fan, they just don't operate or perform anything like the other.

--Ducted fans and Rotors operate at near 0 axial velocity, ie they hover very efficiently, and have huge static(take/liftoff thrust), but putter out very quickly as axial airspeed increases. It's a general range of 0-0.3(or 0.15) mach they work in.

--Propellers operate in the 0.3-0.8 mach range, they don't have the static thrust, but they don't putter out until you hit transonic velocity(they have a nice "cruise" curve).

--Jets(all the atmospheric engines we have now) are generally designed to operate in the transonic(0.7+ mach) range efficiently, they also add fuel mass to the efflux, which drastically changes the equations, and have squat all for static thrust.

--Propulsive efficiency depends far too much on current airspeed to make any general comparison, but jets typically have a very very narrow band of efficiency, while propellers have a much wider curve; and simply by the fuel mass addition, lose out regardless.

Simple graphic, turboshaft means propeller, fans/rotors are another curve before that.

http://engines.fighter-planes.com/JetSuitabilityEn.png

We've had things that LOOK like propellers, etc for years via mods; however, they don't BEHAVE anything like propellers. Even with the addition of the jet engine modules, you will never be able to tweak the cfg files to make them behave anything like propellers; the code just doesn't contort that way, never mind autorotation.

dont make the mistake of assuming that ksp correctly models the functionality of any engine, regardless of type. it doesn't. what we get is a once size fits all engine module. you can tweak your velocity curve to sputter out at certain speeds and be more effective at others, which i think is a fairly close approximation. you just need to make your curve match real world data as close as possible for more realistic results. want perfect realism, you can always build a kit plane in your garage.

Edited April 7, 2014 by Nuke

[coolitic]

Use infi-gliders.

[Random Tank]

For electric-driven ducted fans, though, it'd be simple to keep the thrust fairly low and have a steep fall-off of I(sp) with air pressure to prevent it from becoming a default Eve-killer.

Yeah, that's a point; that's pretty well exactly what Firespitter props do (even with the fuel versions!). Though pretty well any of the Firespitter parts are really crap on Duna; they can only fly up to about 1-2km then they just die (normal wings are only effective up to 5km, and you need a lot of them/large surface area up there too!).