Electric Propellers

[JMBuilder]

Yes, I'm aware that this has been suggested before, but I'm going to expand on it a bit.

It's pretty clear that electric propellers would be very useful for small drones and the like, but why just aircraft? I'm thinking that an electric propeller in KSP would be able to work as an aircraft propeller or as a boat propeller, having special properties that allow it to function better in water than any other form of propulsion. This, or just have two separate types of propellers for aircraft and boats. Propellers could also be set to "push" or "pull" depending on where it was placed on the craft or the situation.

[THX1138]

Plane and boat propellers have different designs because the physical media behave differently.

[TheDestroyer111]

Boats? LOL

I would vote for such engines to be usable on all planets that have an atmosphere, including those that have no oxygen.

[The_Rocketeer]

5 hours ago, THX1138 said:

Plane and boat propellers have different designs because the physical media behave differently.

This is true, but I think what @JMBuilder really means is propellor-engine parts, not just the propellors themselves.

The difference between air and water propellor systems is really only a question of the blade-shape and shaft rotation speed. An electric motor is equally well suited to either application as long as it's attached to an appropriate transfer-box and prop.

One way to do this might be to add a new resource (perhaps called Torque) that is generated from EC by a 'electric motor' part, which is then consumed as fuel by a 'propellor' part - different propellors having different thrust dynamics, efficiency and performance depending on their intended medium, just as different rocket engines do (e.g. vacuum vs pressure). The same resource could also be used by certain types of rover wheels. Bit over my head how far this could be taken, however.

Edited August 13, 2016 by The_Rocketeer

[Van Disaster]

The problem with generating resources is you can store them - while you can store torque in a flywheel, that has side-effects. A torque resource was something I thought about when trying to come up with normal modular engines a while ago. Unless I'm missing something & there's a "can't store" flag now, but that might break the resource system completely.

Boat engines should be usable on planets *without* atmosphere, although you're unlikely to have a planet with no atmo at all and liquid on the surface...

[The_Rocketeer]

6 hours ago, Van Disaster said:

The problem with generating resources is you can store them - while you can store torque in a flywheel, that has side-effects.

Well, a propellor functions more or less as a flywheel anyway. If the only part that stores torque is the prop, and the only part that consumes torque is also the prop, I don't see the problem.

[Kenobi McCormick]

While we're at it let's also get LFO and LF-Intake Air burning recip engines behind the props.

[Claw]

Yeah, I like the idea of electric and LF (possibly LFO) propeller type engines.

They aren't necessarily all that different from a functionality standpoint, but give some new freedoms in design and aesthetics. 

[Van Disaster]

11 hours ago, The_Rocketeer said:

Well, a propellor functions more or less as a flywheel anyway. If the only part that stores torque is the prop, and the only part that consumes torque is also the prop, I don't see the problem.

There were issues with resource flow last time I looked but I've seen more resource flags recently, so maybe that isn't an issue. What *is* an issue is that modules which convert resources to thrust are engines, so your propellor is always going to have to be an engine itself - so "torque" is just fuel and you might as well remove the conversion bit. What we actually need is a custom engine module that converts fuel into some sort of power dependent on the engine type - controlled by throttle/other graphs - and power consumers which provide motion of some sort. The basics are simple - just have to cut the current engine module in half, really - hooking the parts together sensibly when they're stuck on a craft might be a bit harder. I say "dependent on the engine type" because you will want to limit what consumers can be attached to what generators at some point.

[The_Rocketeer]

5 hours ago, Van Disaster said:

modules which convert resources to thrust are engines, so your propellor is always going to have to be an engine itself - so "torque" is just fuel and you might as well remove the conversion bit

Yes, if all you want is a straightforward aesthetic propellor engine; No, if what you want is an electric motor that can have application-appropriate prop blades mounted to it.

What I'm proposing is not that different from the air-intake part / LF engine part relationship:  you must have an intake (motor) module to harvest/generate the vital resource, but you choose the appropriate engine (prop) depending on where and how you're going to use it. Such a feature could be utilised in all sort of ways, like powering robotic arms or winches, or even centrifuges. Sort of like a Kerbal Dremel Tool, one motor for many applications.

But I digress. The main complication I see with my core suggestion arises from differentiating between air and water props: a water proprellor needs to work well below sea level, but would provide only trace thrust above sea level, and the reverse for an aero-propellor - good thrust above water, rubbish below. I conceive this can be done because rocket engines generate more or less thrust depending on altitude/atmospheric pressure, so a modification to the same system would probably make water propellors ineffective when out of the water and vice versa.

[Wjolcz]

Electric props are less sci-fi than SABRE (read as: they already exist and are fully functional) and NASA actually experimented with them, so I think they fit the game really well.

Edited August 14, 2016 by Veeltch

[Van Disaster]

2 hours ago, The_Rocketeer said:

Yes, if all you want is a straightforward aesthetic propellor engine; No, if what you want is an electric motor that can have application-appropriate prop blades mounted to it.

What I'm proposing is not that different from the air-intake part / LF engine part relationship:  you must have an intake (motor) module to harvest/generate the vital resource, but you choose the appropriate engine (prop) depending on where and how you're going to use it. Such a feature could be utilised in all sort of ways, like powering robotic arms or winches, or even centrifuges. Sort of like a Kerbal Dremel Tool, one motor for many applications.

But I digress. The main complication I see with my core suggestion arises from differentiating between air and water props: a water proprellor needs to work well below sea level, but would provide only trace thrust above sea level, and the reverse for an aero-propellor - good thrust above water, rubbish below. I conceive this can be done because rocket engines generate more or less thrust depending on altitude/atmospheric pressure, so a modification to the same system would probably make water propellors ineffective when out of the water and vice versa.

But thrust producing devices are always going to be engines unless there is a completely new engine scheme - so you're still going to be controlling the propellor/device/whatever rather than the motor. You have to split the power production and consumption and control the production rather than all of it. In essence you had the right idea with producing an internal resource, but it can't really be done with the actual resource system.

Electric motor, Gas turbine, Reciprocating engine, all convert resources to power. Propellor, fan, wheel, winch etc, consume power to provide force. Just need to decouple the two so we can control power output & not direct force, and have the consumer just use all power it's provided unless there's some autonomous limiter.

Air & water props are easy, just has to check if it's splashed down - literally a one line check in code. Or you can just check if it's above or below sea level because currently all water is at 0m, but that might not always be the case. Also not sure if that will work on airless but liquid bodies.

Edited August 14, 2016 by Van Disaster

[AlphaKerman]

Yeah, great idea 

[The Optimist]

We already have electric propellers.

[The_Rocketeer]

1 hour ago, Van Disaster said:

you're still going to be controlling the propellor/device/whatever rather than the motor. You have to split the power production and consumption and control the production rather than all of it. In essence you had the right idea with producing an internal resource, but it can't really be done with the actual resource system.

First, I accept that the propellors I propose could be considered an 'engine' by current game terminology. However I think that the infrastructure already exists to make a modified 'engine' that performs according to certain limitations and depends on a resource produced by another throttle-controlled part, so I don't see why this (in quotation) should be so. Rover wheels use EC, which can be produced by alternator. Remove the thrust output from the engine, and u just have an EC generator tied to throttle setting. So the propulsion of a wheel can also be directly linked to the throttle setting (this is easy to set up using trim controls, but I don't see why a rover wheel shouldn't default to full forward throttle).

Now, I realise rover wheels aren't the same as thrusting parts, but they do fit into the resource system in more or less exactly the same way that I'm suggesting propellor/motor parts could.


 

[pandaman]

So @The_Rocketeer, if I understand your idea correctly..  You are suggesting a 'motor' part in maybe a selection of 2 or 3 sizes/outputs that could be 'place anywhere', like air intakes are for jet engines. And we also have a selection of 'propeller' parts, in Water or Atmospheric variants, that can be surface or node attached.  In essence copying the 'jet engine/air intake' format.

Another idea may be to have the 'motor' part you suggest simply integrated into the 'propeller' part.  So we just get 2 classes, Water and Atmospheric, in a selection of sizes. 

What I like about the separate 'motor' part concept though is that you could possibly increase power by having multiple motors, but still only have a single 'propeller', or multiple 'propellers' powered by a single 'motor'.  This would give greater design freedom and allow the heavy motor(s) to be placed centrally with the relatively light propellers elsewhere.

[The_Rocketeer]

@pandaman  I was agreeing with the view that boat and aircraft propellors are totally different and shouldn't work as well in both applications, but disagreeing with the view that that necessarily meant a single 'electric motor' part couldn't be used for both, assuming there was a choice of 'propellor' parts that reflected or determined the intended application. Personally my main interest is having boat propellors that don't create unrealistic thrust in air, and aircraft propellors that don't create unrealistic thrust in water, but for all I know this has already been achieved by someone.

I didn't really get into the specifics of sizes etc - a proof of concept is really required first - but beyond the above, I think u have the gist of it.

It always struck me as odd that in KSP jet engines are basically just the jet nozzle, and all the turbofan equipment and combustion chambers are... bigger on the inside^TM? For example, you can stick Wheesley turbofan engines anywhere without having to use a nacelle to actually contain the turbofan... So, I personally envisage a system in which the motor/propellor relationship makes some sort of mechanical sense, where transfer boxes or prop-shafts realistically could exist within the structure - I don't like the idea of torque magicking through an I-beam from one fuselage hull to another, for example - but there again the lack of such actually is no less Kerbal than the current jet engine system, and as you say does afford considerable design freedoms. I'm pretty relaxed on this tbh.

So yeh. I also think perhaps you're speaking of a bespoke and ideal system, whereas I'm suggesting something that simply modifies and re-applies what we already have.

[Wyzard]

If the propeller has to be an "engine" in order to produce thrust, can it ignore the throttle setting like SRBs do?  If it can produce thrust proportional to the available torque instead of proportional to throttle, it wouldn't really seem like an engine even if the game thinks of it as one.

[pandaman]

@The_Rocketeer.  Ok,  I think I'm with you properly now.  Yes I agree water and atmospheric props, even though they essentially work in the same way, are at 'different ends of the scale' as it were.  So one would not perform well in the other's environment, and if props are introduced to the game then they should reflect this.

I am divided on whether I think the motor should be separate to the prop part though.  I think it comes down to how the power (torque) is generated and fed to the props.  Electric props could gave the motor integrated,  but LF powered one could have it fed through drive shafts etc. so could have a separate 'motor'. 

[pincushionman]

We had a discussion some time ago about separate "core" and "nozzle" parts, in the context of jet engines. I made the point that you could then have piston or electric "cores" as well as gas turbines, and that could drive different effectors (nozzles) like airscrews, generators, or wheels driven by these cores via a resource like "enginePower" or "compressedAir" or something like that.

I'm glad the discusion has come back, not least because I was never savvy enough to even begin to mod it.

As for limiting the various effectors by whether they're in water or not, the AtmosphereCurve of current jet engines is ultimately about pressure, no? Could that be used to enforce proper behavior?

[Van Disaster]

20 hours ago, Wyzard said:

If the propeller has to be an "engine" in order to produce thrust, can it ignore the throttle setting like SRBs do?  If it can produce thrust proportional to the available torque instead of proportional to throttle, it wouldn't really seem like an engine even if the game thinks of it as one.

ModuleEnginesFX lets you lock the throttle, yes - not sure if it works with all types of engines it covers ( SRB's are "SolidBooster", dunno if that actually does anything internally ) or whatever other wrinkles there are like resource flow, but it's a good place to start. There's still the issue of "why bother" though, because you're setting a whole engine up anyway... I can see it if you want to drive different devices, but for singular ones there doesn't seem to be a reason to do it. Mass distribution, I guess.

@The Rocketeerif you can set up a stock rover wheel to default to full forwards, then please demo it ( also how to reverse it! ).

@pincushionmanyou can tell engines not to work underwater. I don't think you can tell them to only work underwater in stock but you can just tell them to provide 0 thrust above 0m.

Edited August 15, 2016 by Van Disaster

[Aladran]

I would love to have Electrical propellers. Some mods provide them, but having them stock would be a nice addition to the game.

 

I would use them for ultra light atmospheric probes, or naval exploration on Laithe or Eve

[KerikBalm]

If we're going to have different props for the electric motors... then jet engines shouldn't work underwater.

For now, I'm happy with my simple modded "Ducted electric fan" part

Spoiler

Note how it barely produces any thrust on Duna... its using the same atmosphere-thrust curve as the goliath. but that plane can fly on just 7.4kN of thrust

If we have a sharp atmospheric density transition at sea level, it would be relatively easy to make one motor or another work/not work when under water using the atm curve for jets... Suppose for every planet with an ocean, we set the atmosphere density at 0 meters and below to be 15 ATMs, and we have boat motors more best at 15 ATMs, and do almost nothing at 1 atm (maybe they work OK on eve with its denser atmosphere? or OK deep in Jools atmo? I don't know).

In contrast normal turbines generally produce more thrust as the atmosphere gets denser, but we can change the curve so that they start to lose thrust, or lose Isp as the "atmosphere" density gets above a certain point. Then we just redefine the atmosphere conditions below 0 meters. Make all airbreathing jets fail to produce thrust while under water.

I could do that with kopernicus, but I'm happy with my simple re-scaled Goliath turned into an electric fan, and not really motivated to go any further.

[John FX]

I (again) support electric props. Some form of aerial propulsion which can last more than a few minutes for places like Duna would be very nice.

[pandaman]

From a pure gameplay perspective we don't need LF powered props for Kerbin or Laythe as we can use jets for that, but electric propulsion could be used there and anywhere else with an atmosphere, so from that perspective alone there is a viable argument in favour of introducing them.

Add to that the 'reality' check that IRL jets don't work under water, but the fact that they currently do in stock is useful as a workaround.  That really should be fixed at some point, but ideally not until we have another solution - like electric props that are configured for use in liquid rather than gas.

Perhaps there is an argument for both EC and LF/O powered propellers.  EC powered ones could be of relatively low power suitable for smaller vessels and LF/O could be bigger with more 'welly'.  Both would be able to be used anywhere as neither necessarily rely on atmospheric oxygen, though maybe the LF/O ones 'could' use just LF if in an oxygen atmosphere.