Propellers Please?

[KerikBalm]

While craft with electric rotors have not been operated on worlds other than Earth (ie, not as part of space exploration), they clearly have been built (unlike nearly complete NERVA units, and disjoint SABRE components). Scramjets have also been built and tested, but we don't have those (nor do we need them for stock size kerbin, no need for airbreathers to get one to escape velocity).

They would be more useful for space exploration (usable on Eve, Duna, and Laythe  - Jool to some extend, but its nature means there wouldn't be much advantage relative to simply gliding/parachuting down until the kraken strikes) than various parts that we already have that need atmospheric O2 (usable only on Laythe - Yes, I'm excluding Kerbin itself, because that exploration need not involve space-travel).

Sure some of the jet engines are usable for space exploration by helping one get to orbit, but by that logic (plus the rapier objection), we should get rid of the Juno, the wheesley, the Goliath, and the panther. The Turboramjet should be our only airbreather.

I'd argue it would fit your vision of KSP's focus even better if we added an electric prop part, and deleted the majority of jet turbine engines in the game except the Whiplash. We have only actually constructed engine types that are useful for getting in space or exploring a destination in space.

" I'm very well aware KSP is a game - ... I'd wait until it has actually successfully accomplished its mission in 2020 before considering the inclusion of electric rotors "

Oh come on, waiting to add something to a game until after its been accomplished, when all that we know says that it will work and can be built with just normal and very surmountable engineering challenges?

"I think a distinction needs to be made between propellers (electric or turboprop) as a means of propulsion, and rotating turntables/bearing/actuators that actually move rocket parts relative to each other. The latter should be discussed in another thread."

Oh, there is most certainly a distinction... but there is also most certainly a relationship as well. The thing is, we can make stock propellers (electric, and pseudo turboprops), because we can make stock "rotating turntables/bearing ...  that actually move rocket parts relative to each other". They just balloon part count and don't play so well with the physics warp/on rails system.

This is a "two birds with one stone" scenario.

[sumghai]

As neither of us will concede our respective positions, I think we're just going to have to agree to disagree, then.

[Klapaucius]

It may be Kerbal Space Program, but if you say that is the primary goal, then why have air-breathing jet engines as well?  The Juno won't get you to the Mun. Many of us spend a lot of time designing and flying planes.  Perhaps that was not the original goal of KSP, but it has evolved to a big part of the gameplay for many.  Just look at how many planes are on KerbalX.  From a sheer business standpoint, Steam would be wise to throw a few more bones to a large constituency.

Also, as far as planetary exploration goes: propellers are the only reasonable propulsion system for atmospheric flight on non-oxygen planets: Eve and Duna, and for those who delve into planet packs, dozens of others.

In real life, there are proposals for prop-driven drones for Mars and Titan exploration.   Take for example the AVIATR, which would have been a nuclear powered prop driven drone for Titan.  Unfortunately, the proposal did not make the cut, but the point is, the concept is there and it will happen eventually.

https://en.wikipedia.org/wiki/AVIATR

And, copied and pasted from Wikipedia:

Proposed Mars Airplane concepts include:

• ARES (Aerial Regional-scale Environmental Survey)^[20]
• MAGE (Mars Airborne Geophysical Explorer)^[17]
• AME (Airplane for Mars Exploration)^[15]
• MATADOR (Mars Advanced Technology Airplane for Deployment, Operations and Recovery)^[15]
• Sky-Sailor, solar powered airplane with micro-robots^[21]
• Kitty Hawk, multi-glider mission^[17]
• Daedalus, glider with 400+ km range^[22] (Mars Scout 2011 proposal)^[23]
• ARMaDA, "Advanced Reconnaissance Martian Deployable Aircraft"^[24]
• MAREA, "Martial Aerial Research Euroavia Airplane"^[24]
• Prandtl-M^[25] (Preliminary Research Aerodynamic Design to Land on Mars)^[26]
• NASA Mini-Sniffer, considered for sampling the atmosphere of Mars, tested running on hydrazine (air independent).^[27]

[Frozen_Heart]

A lot of people still think that adding the SPH, wings, and airbreathing engines was a mistake. I see the opinion on a regular basis.

 

Personally I see space exploration as more than just going into space itself. The goal is to get to other planets and explore them. Things like wheels and propellers help with that task.

 

 

[Jimmidii]

I'd argue that a prop part would have at least as much use as a Wheesley in terms of space exploration.

For me, having a part for early game that's more efficient than jets over short distances at low altitude would fill a capability gap, and having a part that provides efficient propulsion in non-oxygen atmosphere would fill another capability gap.

From a personal point of view, I'd like to see them added.

[James M]

Seeing as there's a lot of talk about "This and that hasnt been made or done yet! It shouldnt be included!", I just want to throw in that reminder that Squad cooperated with NASA specifically to include the astroid redirect section of ksp. Its not that far fetched that they could team up with JPL or the Air Force to introduce an Aerospace dlc or add on including things such as our much debated prop engine

[Triop]

On 9/27/2018 at 5:40 AM, sumghai said:

My personal opinion is that given the theme of the game is Kerbal Space Program, any aircraft parts included in the stock game are those that can be feasibly used to construct spaceplanes - fixed wing aircraft that can transition between atmospheric and spaceflight. The fact that a player could also use some of the engines to build aircraft capable of only atmospheric flight just happens to be a bonus.

No propeller-powered aircraft are capable of escaping from or operating outside of the atmosphere, therefore they would see limited use. If propellers are added to the game, the title and theme would then have to be changed to Kerbal Aircraft and Space Program.

 

Somebody please fire this guy.

 

The propeller to me is a mandatory to prepare for space flight.

If it didn't excist men never would have reached the Mun....

But you can allways start your career with a Juno . . . 

 

Edited October 7, 2018 by Triop

[KerikBalm]

On 10/4/2018 at 2:30 PM, Frozen_Heart said:

A lot of people still think that adding the SPH, wings, and airbreathing engines was a mistake. I see the opinion on a regular basis.

Personally I see space exploration as more than just going into space itself. The goal is to get to other planets and explore them. Things like wheels and propellers help with that task.

I have never seen that opinion expressed by someone, and as you're not expressing that as your opinion I still haven't. I have heard people complain that too many resources were devoted to these parts, but not that the inclusion of the parts altogether was a mistake. Most complaints I saw focused on the fact that majority of new parts (before the MH DLC), were airplane parts (Goliath, Panther, completely revamped mk3 parts, large wings and control surfaces, etc). The complaints I saw were not that adding planes to the game was a mistake, just that there was too much focus on those parts.

On 10/7/2018 at 9:02 AM, Triop said:

Somebody please fire this guy.

He's not a squad employee, he doesn't have any more power over the game than you do, calm down and let him express his opinion.

[Arugela]

I wonder if they are afraid of adding propellers because of the potential of electic craft and balancing EVE and other atmospheres. It might take the challenge out from some perspective. Although it would be fun to designate it as a rotary world in essence. And I would imagine gains would be similar, just obtained in a different way. And it would probably take longer to get rotary craft off even or other planets. So it's not like you gain time. Like SSTO's its a matter of accomplishment. Not efficiency in time. Or does this save too much potential money from normal gameplay. I only play sandbox so I dont' know what it could involve realisticly in time and money during normal gameplay.

I would rather these were in the game stock in some form. Then you only need to design your own electric stock rotary machine to get past the designed limits of the single stock part. 8)

I would say rotary and other propulsions are definitely logically part of a space theme. So are a lot of other things they could add to the game. And stock is always better than mods. I hate mods.

Also, it could be an amazing tool for aero planets. It would help show how much of an advantage atmospheres are potentially. And on planets with air they would be the best explorers and something that doesn't move or explode in such a drastic way. It could help get around more easily(as ground physics tend to have issues.) and it could be good as a pull craft to move stranded vehicles etc. They would just need to possibly add more to the landscape at some point to sightsee or do as you could spend all day just flying around in them.

From what I've used of stock propellers I've designed for eve. It takes an hour(literally) to get the surface. And much longer to get up if it can. You aren't loosing anything challenge wise. Maybe just making a craft that can make sure you can launch from a similar altitude to a mountain at any location or have an alternative high altitude secondary version of the parachute. This would give a little altitude gain for rockets launch mid air and maybe save on descent in some ways. It's not like we can airhog up to max altitude like we could before 1.0. The propeller designs seem to have very hard limits in atmosphere as far as height gain. Just like jet engines artificially do now.

I bet it would cap out at around 20 tons off eve. which being it should have advantages have an atmosphere this makes tylo the new difficulty king potentially. Or at least it splits up the potential preferred means to get on/off planet.

Has anyone tried spinning rotary/parachute means to ascend off Eve as opposed to descend. I wonder if there is a way to exploit it?

Edited October 11, 2018 by Arugela

[James M]

I've never once built a machine in my ksp saves as I pretty much exclusively play career mode. All the time building one would be time lost doing something more monetarily and scientifically beneficial. As such, my only two attempts at eve were with aerobrake entry profiles. My whole reason for bringing this up was that I've been wanting to more thoroughly explore Duna and Laythe, but a rover just felt too slow and I couldn't really vertically ascend up mountains and such. I hadn't really thought about Eve at that point, but assuming you landed your ascent vehicle on top of a mountain (Which you should)... and you wanted an unmanned drone to collect science and bring it back to you... an electric propelled craft makes a heck of a lot more sense than a rover. 

Edited October 12, 2018 by James M

[KerikBalm]

10 hours ago, Arugela said:

I wonder if they are afraid of adding propellers because of the potential of electic craft and balancing EVE and other atmospheres. It might take the challenge out from some perspective.

Very limited perspectives... imagine something with half the speed of a Goliath... and half the TWR. Back when I was still playing stock size KSP and stock Eve (now doing 3x, with Eve gravity reduced to1.2 g, and its atmospheric pressure doubled to 10 atms... only aerospikes work at low altitude, sea level ascent is a seriously monstrous task), there were some marginal Eve SSTO designs (their mass, minimal landing gear, and need to land at the highest mountaintop precluded them from being self sufficient reusable craft.... maybe if one set up a fueling station on top of the mountain (assuming you have ore there), and landed them empty and filled them up, it just might work). I made some modded "turborocket" motors that used LF+Ox and had an Isp of 0.9/2*4000, with the thrust and atm curve of a wet panther (and 10% worse TWR) ... and I wasn't having any SSTO success (wasn't trying from the highest mountain) because of drag losses and an inability to lift sufficient fuel.

Electric props may be able to get a craft above the thick atmosphere, but they won't be lifting enough to get the whole thing to orbit if they are balanced right.

They would simply make exploring the planet easier... right now you basically have to hope from ore concentration to ore concentration with basically a ballistic and gliding self refueling rocket to really explore the surface much.

[Arugela]

Yea, I've tried flying like that. I just wonder if that is the developers perspective. Or if there is some technical aspect to the balance they don't want to deal with. There may be some odd problem. They sort of seem to juggle Eve's workable parameters around each patch(or they used to). I wonder if they leave that versatility in order to make it easier to balance the rest of the game. Not to mention this might make more things to balance from the standpoint of aerodynamics in the heaviest body under those circumstances. There may be a technical reason because of the annoyance of development they are avoiding it. Or that is what it makes me think and wonder. Or is it easy from their end to balance the math related to aerodynamics ascent/descent? I'm assuming, either way, it might seal in some aspects of the game from a design standpoint. Obviously I could be wrong though.

[Kenobi McCormick]

On 9/26/2018 at 10:40 PM, sumghai said:

My personal opinion is that given the theme of the game is Kerbal Space Program, any aircraft parts included in the stock game are those that can be feasibly used to construct spaceplanes - fixed wing aircraft that can transition between atmospheric and spaceflight. The fact that a player could also use some of the engines to build aircraft capable of only atmospheric flight just happens to be a bonus.

No propeller-powered aircraft are capable of escaping from or operating outside of the atmosphere, therefore they would see limited use. If propellers are added to the game, the title and theme would then have to be changed to Kerbal Aircraft and Space Program.

Uhh, no. I can think of three uses for recips in KSP right off the top of my head:

 

* Early game science gathering.

 

* Sightseeing contracts.

 

* Cheap long-range aircraft.

 

 

That's, coincidentally, what I use the recips I build using mods for as well. I don't waste my time engineering some fancy-pants expensive jet to take a tourist over to the nearby island runway, I just warm up the cessna or throw 'em the keys to an old warbird. Why spend 125,000 spesos on an SR71 flight to satisfy a contract that only pays out 12,500 spesos?

 

I honestly think recips have a valid place in KSP right as they are and including them as options will not require a name change. If it did, then we were overdue for it when they decided to add all of C7 Aerospace's jet parts to the game back before it even went behind a paywall.

 

 

Also, yes, yes you bloody well can put a recip into orbit. I might actually give it a try tonight or tomorrow, build some sort of twin engine recip that can carry enough boosters to get it into orbit. Failing that, I'll just shove a normal launcher up the cheeks end of a Spitfire...

Edited October 13, 2018 by Kenobi McCormick

[KerikBalm]

On 10/13/2018 at 4:17 AM, Kenobi McCormick said:

Uhh, no. I can think of three uses for recips in KSP ... I honestly think recips have a valid place in KSP ... you bloody well can put a recip into orbit

If they add prop motors, I really hope they don't just add a recirpocating internal combustion engine. As you may have seen in my previous posts, for me the biggest use of props would be on worlds lacking atmospheric O2, I'm not looking for another air breathing engine. I wouldn't mind recips if there are multiple new prop motors. I could see 3 types of propeller atmospheric propulsions: 1) Electric motor (2) Monoprop powered (see this thread: 

3) Air breathing internal combustion piston engine

but if we get 1 and only 1, I want electric

Quote

That's, coincidentally, what I use the recips I build using mods for as well. I don't waste my time engineering some fancy-pants expensive jet to take a tourist over to the nearby island runway, I just warm up the cessna or throw 'em the keys to an old warbird. Why spend 125,000 spesos on an SR71 flight to satisfy a contract that only pays out 12,500 spesos?

1) assuming you don't crash, the costs of a turboramjet flight won't be anywhere near 125,000. They'd be an order of magnitude or two less.

2) Its not that hard to make a working turboramjet craft, and for what you describe, the turbofans work fine

The use on Eve and Duna + mod worlds like Tekto are what appeal to me

[Kenobi McCormick]

On 10/14/2018 at 9:03 AM, KerikBalm said:

If they add prop motors, I really hope they don't just add a recirpocating internal combustion engine. As you may have seen in my previous posts, for me the biggest use of props would be on worlds lacking atmospheric O2, I'm not looking for another air breathing engine. I wouldn't mind recips if there are multiple new prop motors. I could see 3 types of propeller atmospheric propulsions: 1) Electric motor (2) Monoprop powered (see this thread: 

Late reply I know, but...mm, there's no reason you can't pipe LO2 into a standard recip with the right manifolds. Engine doesn't care where it gets its oxygen, only that it gets oxygen. I can't imagine the efficiency would be all that good, but hell, it at least should be better than an LF/O2 rocket engine.

 

I 'spose that's also a valid use case for recips in KSP, but to me, recips in KSP are an early game tech that is to be rendered obsolete later on down the line by more advanced systems. Kinda like what we've done in real life, generally, recips are only used on light personal craft and historic craft that originally had them.

 

 

Turboprops would be a nice addition too, I'll admit. Not quite a recip but the end result isn't much different.

Quote

1) assuming you don't crash, the costs of a turboramjet flight won't be anywhere near 125,000. They'd be an order of magnitude or two less.

2) Its not that hard to make a working turboramjet craft, and for what you describe, the turbofans work fine

The use on Eve and Duna + mod worlds like Tekto are what appeal to me

It costs maybe two thousand to throw a recip that'll carry 12 kerbals up. They're cheap as chips. Simple to engineer. Barely use fuel. Can just throw 'em together and generally they'll fly. I've found jets can be quite finicky at times but recips are pretty much 'throw airplane shaped boards at a washing machine and the end result flies half-decent'. If I try I can get pretty damn good performance out of them, too.

Some of it might have something to do with how slow they are, though. Typical stall speeds for my recips fall in the 25-45m/s range. With a stall speed that low you really have to balls it up to crash one, and landing gets rather easy. By default they tend to be seaplanes too on that same basis, they land so slowly that they can reliably splash down undamaged.

Edited November 2, 2018 by Kenobi McCormick

[kerbiloid]

(Haven't tried this but probably)
if

• add an Aether resource in CRP and define its presence everywhere outside of atmosphere,
• (re)define an engine part spending ElectricCharge and Aether as resources (they may have propellers)
• (re)define an Aether scoop part

we can fly between the planets with propellers.

Also instead of a propeller the engine part may have a pair of waving wings.

Edited November 3, 2018 by kerbiloid

[KerikBalm]

On 11/2/2018 at 8:21 PM, Kenobi McCormick said:

Late reply I know, but...mm, there's no reason you can't pipe LO2 into a standard recip with the right manifolds. Engine doesn't care where it gets its oxygen, only that it gets oxygen. I can't imagine the efficiency would be all that good, but hell, it at least should be better than an LF/O2 rocket engine.

And there's no reason that you can't do that with a turbofan, or a turbojet, or a ramjet. Then you've got what are known as ram-rockets/turbo-rockets/air-augmented-rockets:

https://en.wikipedia.org/wiki/Air-augmented_rocket

They use the atmosphere as working mass, but not a source of chemical energy. For the same amount of chemical energy as it takes to throw 1kg of mass back at 200 meters/second, you could throw 4kg of mass back at 100 meters/second for 2x the thrust, or 16 kg of mass back at 50 meters/second for 4x the thrust. If the reaction mass is "free", your effective Isp could go up by a factor of 4x.

This is a major part of the efficiency gain of jet engines, and why high bypass turbofans do so much better than turbojets. The other efficiency gain is of course taking O2 from the atmosphere (in real rockets/jets has an Oxidizer:Fuel mass ratio of around 2-3 : 1 ... in KSP it is only 1.1 : 0.9)

Still, it would be simpler to just use monoprop, which is why I suggested a monoprop powered reciprocating engine. After all, we don't currently have a lot of use for the larger mono-prop tanks (unless you just like using monoprop engines for the lulz, or are really, really, really bad at docking, or decide that reaction wheels are OP'd, and only use RCS to maneuver).

If you make a LF+O consuming recip engine.. you might as well just make it electric charge consuming, and give players the option of pairing it with fuel cells for more flexibility.

[Guest]

Seconded.

I would love to make a craft capable of aerial exploration of Eve. A propeller would be ideal for that. There is currently no stock solution to that problem.

And yes this is squarely in the "nice to have" category, but then there's a ton of "nice to have but not strictly necessary" stuff there already -- Goliath turbofans, four different kinds of rover wheels including those lovely ridiculously big ones, those light fixed landing gear setups, and so on and so forth. A couple of stock propellers would not be at all out of place in that company.

[KerikBalm]

14 hours ago, Brikoleur said:

I would love to make a craft capable of aerial exploration of Eve. A propeller would be ideal for that. There is currently no stock solution to that problem.

But there is, my problems are:

1) High part count

2) They don't work under water, so stock subs are only really possible on Kerbin/Laythe/a body with O2 in the atmosphere

 



 

Edited November 6, 2018 by KerikBalm

[Guest]

Okay true, there is. But this really is unreasonably complicated for a tech level that predates spaceflight by... a long time.

[Kenobi McCormick]

On 11/5/2018 at 1:42 AM, KerikBalm said:

And there's no reason that you can't do that with a turbofan, or a turbojet, or a ramjet. Then you've got what are known as ram-rockets/turbo-rockets/air-augmented-rockets:

https://en.wikipedia.org/wiki/Air-augmented_rocket

They use the atmosphere as working mass, but not a source of chemical energy. For the same amount of chemical energy as it takes to throw 1kg of mass back at 200 meters/second, you could throw 4kg of mass back at 100 meters/second for 2x the thrust, or 16 kg of mass back at 50 meters/second for 4x the thrust. If the reaction mass is "free", your effective Isp could go up by a factor of 4x.

This is a major part of the efficiency gain of jet engines, and why high bypass turbofans do so much better than turbojets. The other efficiency gain is of course taking O2 from the atmosphere (in real rockets/jets has an Oxidizer:Fuel mass ratio of around 2-3 : 1 ... in KSP it is only 1.1 : 0.9)

Still, it would be simpler to just use monoprop, which is why I suggested a monoprop powered reciprocating engine. After all, we don't currently have a lot of use for the larger mono-prop tanks (unless you just like using monoprop engines for the lulz, or are really, really, really bad at docking, or decide that reaction wheels are OP'd, and only use RCS to maneuver).

If you make a LF+O consuming recip engine.. you might as well just make it electric charge consuming, and give players the option of pairing it with fuel cells for more flexibility.

Mm, but LF+O is more versatile. Can get a lot more power out of it without requiring a mountain of support systems, or scale it down to something barely larger than a soda can. Atop that, it can be dual mode, just as the SABRE engines we already have, burning intake air when available and liquid oxidizer when necessary. Of course it would need a vacuum thrust of basically nil, but yeah.

 

A monoprop engine, an electric engine, and a turboprop engine would all be nice little niche products, but the bread-and-butter oughtta be a selection of LF/IA recips with LF/O dual mode operation unlocked later in the science tree. They'd be the most versatile, and also the simplest, options here, good for general usage with the other engines available for specific missions that necessitate them.

Edited November 8, 2018 by Kenobi McCormick

[KerikBalm]

6 hours ago, Kenobi McCormick said:

Mm, but LF+O is more versatile. Can get a lot more power out of it without requiring a mountain of support systems, or scale it down to something barely larger than a soda can. Atop that, it can be dual mode, just as the SABRE engines we already have, burning intake air when available and liquid oxidizer when necessary. Of course it would need a vacuum thrust of basically nil, but yeah.

Dual mode could work... but I don't know what you mean about a mountain of support systems. In game or real life? In real life monoprop is simpler than a LFO system. In game its basically the same (ISRU can make either, so that support system is the same, and the fuel for each is stored in its own tank).

In game the electric prop would need  the least support. A battery + RTG or solar panel will enable unlimited travel, as compared to ISRU which requires at least a drill+converter+power source+ore tank+fuel tank, ideally with a radiator too, and its going to need to have sufficient range to cross areas without ore.

As for vacuum thrust, it shouldn't have any. Its super easy to add another intake resource (often named IntakeAtm instead of IntakeAir in mods, such as the community resource pack), and have intakes produce that regardless of O2 presence. Then the engine only works in an atmosphere, but it doesn't require O2. You'd have one mode using LiquidFuel + IntakeAir, and another version using LiquidFuel + Oxidizer + IntakeAtm.

Quote

A monoprop engine, an electric engine, and a turboprop engine would all be nice little niche products, but the bread-and-butter oughtta be a selection of LF/IA recips with LF/O dual mode operation unlocked later in the science tree. They'd be the most versatile, and also the simplest, options here, good for general usage with the other engines available for specific missions that necessitate them.

A selection??? We'd be lucky to get one part, and the simplest and most versatile would be an electric one.

+1 part (fuel cell array) and its an LFO engine (we could make Fuel cells essentially dual mode, using Oxidizer or IntakeAir)

They'd work for subs (plus with RTG instead of fuel, they'd never have buoyancy issues), they'd be simpler to operate long term (no ISRU). There'd be no mode switching needed or wondering if you need to bring oxidizer or how much fuel is needed, etc.

An electric propeller would be way better than reciprocating engines.

Reciprocating engines would be almost worthless compared to turbofans.

Dual-mode airbreathing/closed cycle atmospheric engines would be nice, but such a dual mode engine doesn't need to be a reciprocating one.... and for the goal of the game it might as well be something more like a turboramjet (Ie a turbo-ramrocket).

I'd much rather have air augmented rockets/turbo-rockets or  propellers turned by electric motors over propellers turned by reciprocating engines.

On 11/6/2018 at 9:08 AM, Brikoleur said:

Okay true, there is. But this really is unreasonably complicated for a tech level that predates spaceflight by... a long time.

I agree completely. It is unreasonably complicated (which is similar to the problem I mentioned: "High part count")

If they were going to make multiple new atmospheric engines, I would love for a piston engine+propeller to be available by default (like the flea SRB)+ basic wings (they could be worse than the wings unlocked later... cheap and light with a heat and impact tolerance as low as the basic fins.. so they aren't useful for spaceplanes).

Then you "upgrade" to turbojets and turbofans (juno, wheesley), then low bypass afterburning turbofans (panther), then ramjets (whiplash), then the dual mode Rapier.

At some point, there could be a branch for an electric motor (special R&D for ensuring it survives the rigors of space travel, that lubricants can operate in near vacuum, special sealing against fine dust/electrostatic discharges, etc), and a monoprop propeller.

But that would already be 3 new engines, and I think we'd be lucky to get one.

Side note... Could we possibly get a triple mode engine?

The Rapier could then just have its properties changed.

Open-cycle: acts like normal, uses incoming atmospheric O2

Atmospheric-closed cycle: injects O2 to combust with LF, but still uses atmosphere in turbine blades and as working mass, Isp would be reduced by 0.9/2 (the ratio of liquid fuel mas to liquidfuel+oxidizer mass), for an atmospheric Isp of 1,440 (nearly double what a LV-N gets, with a much better TWR, at sea level on Eve or Kerbin).

Vacuum-closed cycle: Acts like closed cycle now

Open-cycle and atmospheric closed cycle would have the same cutoff point in the atmosphere, so you wouldn't switch from open to atmo-closed to vac-closed.

Automatic switching logic would always favor open cycle over atmo-closed. Switching order (for manual switching, as by action groups) should probably be open>vac-closed>atmo-closed.

That way for normal rapier ascent, your switching works as normal (but if you want to manually switch back to open cycle after reentry, you press the switch mode action group twice instead of once).

For use on Eve or Duna, with automatic switching it would work just like automatic switching works now on kerbin/laythe, except switching to/from an IntakeAtm+LF+O mode instead of IntakeAir+LF mode. For manual switching, you'd set it to IntakeAtm+LF+O and have to press the switch button twice (instead of once) to go into full rocket/vacuum mode.

Then we'd have an efficient enough engine for subs on Eve, for planes on Eve or duna, and it wouldn't add any new parts, and would maintain a space-focus

Edited November 8, 2018 by KerikBalm

[Kenobi McCormick]

4 hours ago, KerikBalm said:

but I don't know what you mean about a mountain of support systems

Monoprop tanks are tiny and have love all monoprop in them. You need far more of your craft dedicated to containing fuel than you would an LF/IA engine. Electric? If you're building anything practically large you're gonna need far more than 'a battery and an RTG/Solar Panel' to get reasoanble performance out of the thing, and if you want to be able to run it full throttle it's gonna have to be 70% generation equipment. Even then it's gonna be beat out by a big ol' Pratt R2800 every time.

Quote

As for vacuum thrust, it shouldn't have any. Its super easy to add another intake resource (often named IntakeAtm instead of IntakeAir in mods, such as the community resource pack), and have intakes produce that regardless of O2 presence. Then the engine only works in an atmosphere, but it doesn't require O2. You'd have one mode using LiquidFuel + IntakeAir, and another version using LiquidFuel + Oxidizer + IntakeAtm.

You could also apply a KISS approach and just set its ISP curve properly. The recips we get with Firespitter produce love all thrust above 15,000km even if you use cheats to keep them running that high up. The game fully supports engines having different thrusts at different altitudes and it'd be trivial for a skilled modder to set that curve up such that the engine just flat out stops doing anything useful above the sort of atomspheric densities required for a propeller to work at all. It's already done in the recip mods we have now.

Quote

A selection???

Yes. A selection. Small, Med, Large LF/IA recips, an electric, and a monoprop.

 

Quote

and the simplest and most versatile would be an electric one.

No. The most versatile would be the LF/IA recips. You can't scale the electric ones up very large before the weight of the support equipment exceeds the craft's ability to get off the ground, a problem that doesn't exist with ICE powerplants. You're not gonna be building any fully electric four engine propjobs that can carry several tons of payload, such a craft would be so heavy from all the batteries and such that it'd barely be able to carry itself to the heavens.
 

 

Quote

+1 part (fuel cell array) and its an LFO engine (we could make Fuel cells essentially dual mode, using Oxidizer or IntakeAir)

Fuel cells? Well hell, you're still burning LF/O, why not cut the middleman out and just pipe the LF straight into the engine? KISS is a wonderful thing to apply when it comes to engineering, especially when you're looking at early game tech which is where these engines would fall. The whole point of giving us prop jobs is to make fixed wing atmospheric flight more viable early game.

Quote

They'd work for subs (plus with RTG instead of fuel, they'd never have buoyancy issues), they'd be simpler to operate long term (no ISRU). There'd be no mode switching needed or wondering if you need to bring oxidizer or how much fuel is needed, etc.

Subs don't have to worry about lift. The also don't have to worry about batteries. Submarines in modern navies haven't run on batteries in 40 or 50 years, what with them all being run straight off a massive nuclear reactor and all. The only navies still using batteries in their subs are using hilariously outdated antiques that were state of the art back when the finest fighter planes in theskies were armed with nothing but machine guns.

 

Large electric props work here, but they'd have to come with nuclear reactors to power them. Also not the scope of our discussion, we're referring to aviation usage, not naval usage.

Quote

An electric propeller would be way better than reciprocating engines.

For certain applications, yes. For general usage, no. The best prop powerplant for general aviation has remained the gasoline fuelled recip for over a hundred years and doesn't appear to be changing anytime soon. If it does, itt'l be to move towards diesel, provided the tech inherent in manufacturing a reliable aviation diesel engine matures enough that they don't end up excessively heavy.

Quote

Reciprocating engines would be almost worthless compared to turbofans.

They'd use a fraction of the fuel a turbofan uses and an order of magnitude less fuel than a non-turbofan jet engine uses. You'd be trading off the ability to cruise along 575MPH @ 35,000' for being able to go nearly twice as far on the same quantity of fuel. Turbine engines are LUDICROUSLY thirsty and you need only look at the M1 Abrams to see this in action. Abrams has roughly the same shaft horsepower going to its tracks that the Leo 2 has, yet needs twice as much fuel to go the same distance.

 

Gas turbine engines are stupidly thirsty and will never match the fuel economy of a piston engine. The only reason we use them in aviation is because of the equally excessive amounts of thrust they can provide.

Quote

Dual-mode airbreathing/closed cycle atmospheric engines would be nice, but such a dual mode engine doesn't need to be a reciprocating one.

And yet it'd be nice to have one. Would let you operate a big ol' Pratt radial on Eve.

Quote

and for the goal of the game it might as well be something more like a turboramjet (Ie a turbo-ramrocket).

We already have one of those, in case you weren't aware. We've had it for ages, too.

Quote

I'd much rather have air augmented rockets/turbo-rockets

we already have a similar enough engine in the game.

Quote

  propellers turned by electric motors over propellers turned by reciprocating engines.

I'd rather have a Pratt R2800 and R4360 in my game. I can do far more with one of those monsters than I ever could with a desk fan taped to the front of the plane. I don't build small recips, I build big ones. Think B-29, B-36, B-24, Lockheed Super-Connie. Planes like that are too large to be practical on an electric power system. You might could sorta half-assedly get away with jury-rigging a Cessna 172 using the ludicrously advanced batteries and generation systems Kerbals have but you're not gonna get a super-connie off the ground on batteries. Not even using Kerbal batteries. Thing's just too big and too heavy.

 

There's also another factor you're not considering that's incredibly relevant...perhaps moreso than any other point you've brought up so far...to our discussion: Part count.

 

I don't know the details of your machine, but I know mine well enough, and I know my framerate goes to absolute horseexcrements if I have more than about 150 parts on screen at any one given time. With fixed wing flight I like to keep part counts below half that just to guarantee at least 30FPS. So, 75 parts total. That's the part budget for my aircraft.

 

If I want to build a four engine long range prop plane, I need...let's say ten parts for the fuselage, the FAT-A55 wing parts add another ten, throw 5 more on for flaps and ailerons, three for LG, a MechJeb unit...we're at, what,28 parts already? Up to 32 for the engine nacelles, 36 with the engines mounted to those nacelles. The basic airframe comes in at 36 parts, not too shabby considering the size of the vessel, and certainly one flyable even on a potato grade laptop. But it's just a glider, so let's fit some engines...

 

Now, let's say you get your way and all I have are electric powerplants. That means I'd have to spam batteries all over the fuselage and solar panels will need to coat every last square inch of the sun-facing side of this airplane(Which due to its size we will assume is only the top, not something generally expected to fly inverted). Ok, my part count's now hovering around 130 parts, and I haven't even begun to apply a useful payload yet.

 

If I get my way and we get electric props and ICE props(Keep in mind I'm not arguing against having electrics, I'm arguing for having them alongside piston engines, something I think you're missing somehow), I throw a few  stonkin' huge radials on the necelles, add a single 1 meter fuel tank to each nacelle, and some fuel lines to the main fuel reserve. I'm still well within my part budget...somewhere around 40-45 parts...with adequate performance in flight and room to add a useful payload! I have room in the part budget to pack the thing full of every science experiment in the game if I want to, or I can load it up with a rover, or deploy an ISRU, base parts, passengers, whatever I want. I have room in the part budget to actually do things with the vessel without my framerate going to hell the instant I spawn in on the runway.

 

 I'm still in the upper 40th percentile as far as CPU power goes. The vast majority of KSP players are either on hilariously outdated consoles that make my computer look like the CRAY Supercomputer, or they're on craptops that can barely run Firefox properly. If I can't even run such an aircraft on electric power with an acceptable framerate how the hell are they gonna do so?

 

Edited November 8, 2018 by Kenobi McCormick

[Guest]

I get a feeling that @KerikBalm and @Kenobi McCormick are talking at cross purposes here a bit.

Fact is, stock propellers like Kerik is describing are currently ridiculously, insanely overpowered, they're effectively perpetual-motion machines and then some.

Stock props would certainly need to be balanced differently. That would mean that an electric prop would not be able to happily churn the Evian atmosphere powered by a couple of little solar panels. Reciprocating engines /should/ have much better power/weight ratios for reasonable endurance: i.e., the batteries and/or solar panels you'd need to feed an electric prop /should/ weigh more than the fuel tanks you'd use to power a reciprocator.

If Squad was feeling lazy though, I think they might be able to get away with only electric props, if they re-tuned fuel cells. That way they could make it so that you'd get reasonable power output and endurance from a fuel-cell powered electric prop, but a solar-cell powered one would still be marginal at best.

[TheFlyingKerman]

19 hours ago, Kenobi McCormick said:

I'd rather have a Pratt R2800 and R4360 in my game. I can do far more with one of those monsters than I ever could with a desk fan taped to the front of the plane. I don't build small recips, I build big ones. Think B-29, B-36, B-24, Lockheed Super-Connie. Planes like that are too large to be practical on an electric power system. You might could sorta half-assedly get away with jury-rigging a Cessna 172 using the ludicrously advanced batteries and generation systems Kerbals have but you're not gonna get a super-connie off the ground on batteries. Not even using Kerbal batteries. Thing's just too big and too heavy.

You know KSP is about space. The problem with any fuel burning engine is how do you supply the fuel when the craft is operating on another planet? ISRU + drill is heavy and draggy and at minimum you'd have to survey the planet for ore before thinking about sending one. An electrical prop with solar panel/RTG can run indefinitely. Even if it is a 0.5t drone going at 100m/s for 100km a time it is still some unique capacity.