Still Waiting for that Electric Propeller Engine....

[NotDavidTenant]

Been begging for this for the last 2 years lol. Just crossing my fingers that the dev's (what's left of them) take some time and put one into the game. It would be LIT.

[klgraham1013]

6 hours ago, NotDavidTenant said:

It would be LIT.

I would hope so.  If it was the only part in the game not affected by the lighting system, that would just be weird.

[Wjolcz]

The funny thing is there isn't an electric propeller in the game, even though NASA built a flying drone using the technology, and yet we have one that hasn't even been built yet which is RAPIER.

Electric aircraft are more and more common so I don't really see a reason why shouldn't an electric atmospheric engine be in the game.

[KSK]

3 hours ago, Veeltch said:

The funny thing is there isn't an electric propeller in the game, even though NASA built a flying drone using the technology, and yet we have one that hasn't even been built yet which is RAPIER.

Electric aircraft are more and more common so I don't really see a reason why shouldn't an electric atmospheric engine be in the game.

Would be useful for boats too. Or at least it would look better than having every boat powered by jet engines. 

[ottothesilent]

And don't forget, an electric prop could be used to fly on Duna, Eve, etc., since there's not an O2 requirement.

[DrunkenKerbalnaut]

I sat down once and did a little napkin math on the kind of electricity it would take, with an eye to possibly making a 1 part mod. I used the most popular Cessna, and it's most popular combustion motor as my baseline. I think it was rated roughly 70-80kw. 

Then I started looking at the way other electricals in this game acted on -and reacted to- the environment. Batteries and solar cells, namely. I ignored SAS modules, cuz we all know that $#!+ cray cray. 

The numbers were all over the place, and basically it turns out that KSP "batteries" are super-capacitors of goofy energy density proportions. And KSP "solar cells" are solar flare focal point devices (a wee bit of sarcasm, but you get the point).  

My point is without revamping the whole EC system in KSP, electric props can't stand on their own. At least not with anything that passes for realism.

TL;DR:

So my theory is we don't have electric props yet because SQUAD devs don't want to redo the EC mechanic ground-up, or there simply going to give us 1.25m fuel cells to power them. (lol)

[Wjolcz]

14 minutes ago, DrunkenKerbalnaut said:

I sat down once and did a little napkin math on the kind of electricity it would take, with an eye to possibly making a 1 part mod. I used the most popular Cessna, and it's most popular combustion motor as my baseline. I think it was rated roughly 70-80kw. 

Then I started looking at the way other electricals in this game acted on -and reacted to- the environment. Batteries and solar cells, namely. I ignored SAS modules, cuz we all know that $#!+ cray cray. 

The numbers were all over the place, and basically it turns out that KSP "batteries" are super-capacitors of goofy energy density proportions. And KSP "solar cells" are solar flare focal point devices (a wee bit of sarcasm, but you get the point).  

My point is without revamping the whole EC system in KSP, electric props can't stand on their own. At least not with anything that passes for realism.

TL;DR:

So my theory is we don't have electric props yet because SQUAD devs don't want to redo the EC mechanic ground-up, or there simply going to give us 1.25m fuel cells to power them. (lol)

The energy consumption could be easily adjusted. It's just a matter of how much thrust it can produce and how much EC it needs to do so. Every single engine in KSP is unrealistic. The Dawn ion thruster has waaay too much thrust and the Juno can be used for supersonic aircraft. I don't remember the exact numbers, but I think it's something like 4x more powerful than it's RL counterpart (the Me-262 Jumo engine).

And I think the main reason of why we still don't have it in the game has to do with how animations and resources are handled. There's that mod with plane parts that has an electric prop and the thing uses infinite "Coolant" resource, because EC-powered engines need an additional resource to work, or something like that.

1 hour ago, ottothesilent said:

And don't forget, an electric prop could be used to fly on Duna, Eve, etc., since there's not an O2 requirement.

Probably barely on Duna. It shouldn't work well in thin atmospheres IMO. But still, I'd rather have it there than not.

[DrunkenKerbalnaut]

8 hours ago, Veeltch said:

-snip-

You're probably right. I was being a bit salty. I've been waiting for stock props for a minute, myself . Armchair developer over here.

As far as Duna use: bigger blades? More blades? High RPM? Tip rockets (haha)? I'd prefer a system that allows mixing blade profiles and motors, anyways.

Worth a try: Heya, @SQUAD. Anything planned for electric props?

[wumpus]

22 hours ago, ottothesilent said:

And don't forget, an electric prop could be used to fly on Duna, Eve, etc., since there's not an O2 requirement.

They might have to rebalance fuel cells, batteries, solar, or NTR won't cut it for planes (well batteries might for short distances, but you really want a fuel cell).

[Jonfliesgoats]

Agreed.  Props in general would be useful.  Electric, reciprocating and turboprop.  With regard to performance and speed, like Veelch said, KSP is sometimes less than realistic. Supersonic flight with a subsonic intake should cause a jet to flame out, wing sweep should affect stall progression, etc.  

Ideally a motor/propeller combination could be achieved with motors that offer x torque and propellers that offer so much thrust as so much torque.  Most of the props would be constant speed, so they would turn at whatever optimum RPM (we could forego having KSP work in minimum governing speed, etc.).  I could imagine a running propeller animation could just be a blurry disc with start up and shutdown animations.

Props on Duna would struggle in the thin atmosphere, but that's the engineering challenge to overcome. I think they'd love it on Eve, Laythe or flying around Jool's atmosphere, even.  There's a lot of possibility with propellers.

Boat propellers too.  It would be nice to sail around Eve, beaching to collect science from different biomes.

[Azimech]

Just build them yourselves guys. We've been doing it for quite some time now. Look in Spacecraft Exchange for instructions.

Boat propellers won't work under water though but there are people (including myself) that have built electric water planes for use on Eve.

http://imgur.com/a/XCr7J

 

 

[Jonfliesgoats]

Azimech makes a good point.  The problem is making a constant speed propeller requires some pretty large scale vehicles and high part counts for our already laggy machines.  That said, there are some beautiful examples of what people have engineered out there.

[Azimech]

26 minutes ago, Jonfliesgoats said:

Azimech makes a good point.  The problem is making a constant speed propeller requires some pretty large scale vehicles and high part counts for our already laggy machines.  That said, there are some beautiful examples of what people have engineered out there.

Depends ... there are a number of small planes with low part count. The constant speed thing ... you need to adjust prop pitch manually.

[Pds314]

On 11/19/2016 at 0:32 PM, Veeltch said:

The energy consumption could be easily adjusted. It's just a matter of how much thrust it can produce and how much EC it needs to do so. Every single engine in KSP is unrealistic. The Dawn ion thruster has waaay too much thrust and the Juno can be used for supersonic aircraft. I don't remember the exact numbers, but I think it's something like 4x more powerful than it's RL counterpart (the Me-262 Jumo engine).

And I think the main reason of why we still don't have it in the game has to do with how animations and resources are handled. There's that mod with plane parts that has an electric prop and the thing uses infinite "Coolant" resource, because EC-powered engines need an additional resource to work, or something like that.

Probably barely on Duna. It shouldn't work well in thin atmospheres IMO. But still, I'd rather have it there than not.

IRL Turbojets can be used supersonic. Their exhaust is well in excess of mach 1, so as long as the intake geometry is done right, you have no insurmountable problems. I believe the first supersonic US fighter was the F4D Skyray, which used a single J-57 Turbojet with 45 kN thrust.

It isn't fair to compare a KSP engine with an exact real life one. Instead, we should compare type for type. Modern small Turbojets can easily match the TWR of the Juno, which is around 8.0, nominally.

Where the Junk is impossible is its immensely high ISP. IRL turbojets have about 1.1-1.3 lb/lbforce/hour of fuel consumption. The Juno has 0.6, which is plainly absurd. It should drink about double the fuel for what it's doing.

Regarding size, it's about accurate, although obviously real engines have a turbine, not just a nozzle.

So to fix this engine to match modern performance, we need to double the fuel consumption. To match end-WW2 engines, double the thrust-specific fuel consumption and weight and cut the thrust by at least half.

As for the other engines:

Panther: thrust and weight are alright. Double fuel consumption and the engine is on the optimistic side of modern tech.

Wheesley: massively reduce thrust. At least by a factor of 2. Also cut weight down to maybe 1.2 tonnes. ISP is good where it is.

Goliath:  Reduce thrust by 33% to match modern technology. ISP is good where it is.

Whiplash: double fuel consumption.

Rapier: considerably increase fuel consumption. I don't know enough about hybrid airbreathing rockets to know by how much, but I suspect doubling it is a good start. Also probably increase thrust.

 

Basically, KSP masks the differences between engines by making all of them OP, but in different ways. Irl, the high-speed engines, including the Juno, burn much more fuel, and the high-efficiency engines develop much less thrust.

A note on the Panther: some very very new engines are about the size of the Panther but produce much more thrust but also weigh more. The AL-41, for example, apparently produces 180 kN in a 1.280 meter node size engine weighing 1.65 tonnes. The F119 is a 1.2 meter engine that weighs 1.8 tonnes and produces greater than 156 kN. Some seem to speculate 165 kN. The F135 is 1.16 meters wide but produces 190 kN and weighs only 1.7 tonnes. So it's quite reasonable to add up to 50% to both the weight and thrust of the Panther and still call it realistic.

Edited November 21, 2016 by Pds314

[Azimech]

On 19-11-2016 at 9:32 PM, Veeltch said:

And I think the main reason of why we still don't have it in the game has to do with how animations and resources are handled. There's that mod with plane parts that has an electric prop and the thing uses infinite "Coolant" resource, because EC-powered engines need an additional resource to work, or something like that.

 

That's very much something of the past, the new ModulesEnginesFX is extremely configurable.

[DrunkenKerbalnaut]

15 hours ago, Azimech said:

Just build them yourselves guys. We've been doing it for quite some time now. Look in Spacecraft Exchange for instructions.

Boat propellers won't work under water though but there are people (including myself) that have built electric water planes for use on Eve.

http://imgur.com/a/XCr7J

 

 

That's downright amazing. Thanks for sharing. First one I've seen that didn't use the structural fuselage. One problem: it wouldn't survive on-rails time advancing. 

EDIT: unless it re-docks. Does it? Cuz that would be the bees knees  .

Maybe a simple solution would just be some stock rotational motors that you could node or surface attach to. Design your blade profile, spin it at whatever speed you deem necessary, apply however much torque your EC system can handle. 

Edited November 21, 2016 by DrunkenKerbalnaut

[Azimech]

13 minutes ago, DrunkenKerbalnaut said:

That's downright amazing. Thanks for sharing. First one I've seen that didn't use the structural fuselage. One problem: it wouldn't survive on-rails time advancing. 

EDIT: unless it re-docks. Does it? Cuz that would be the bees knees  .

Maybe a simple solution would just be some stock rotational motors that you could node or surface attach to. Design your blade profile, spin it at whatever speed you deem necessary, apply however much torque your EC system can handle. 

I could work on some kind of re-docking system. No-one has ever asked for it before but it did cross my mind.

[Majorjim!]

Just now, DrunkenKerbalnaut said:

First one I've seen that didn't use the structural fuselage.

 

You haven't been looking hard enough!  There are a huge number of ways people have made bearings in KSP.

Just now, DrunkenKerbalnaut said:

One problem: it wouldn't survive on-rails time advancing. 

Yup, an issue to be sure. The docking port would have to be on the rotational part most likely so it can move away enough from the other port to reactivate the docking mechanism.

Edited November 21, 2016 by Majorjim!

[DrunkenKerbalnaut]

1 hour ago, Majorjim! said:

You haven't been looking hard enough! 

You got me there.   

1 hour ago, Majorjim! said:

... so it can move away enough from the other port to reactivate the docking mechanism.

I know they changed some things about the shrouded ports recently. Maybe toggling the shroud would do it?

1 hour ago, Azimech said:

I could work on some kind of re-docking system. No-one has ever asked for it before but it did cross my mind.

Not asking, really. I half expected you to say

"oh well of course it does! And just behind the docking port, you'll notice an all-stock, Turing complete autopilot module made from structural beams and a monoprop tank!"

Edited November 21, 2016 by DrunkenKerbalnaut