Need help with stock propeller

[AeroGav]

Hi folks,  

I've been turning my attention to the hardest problem of all, women  an Eve spaceplane.    SSTO is out of the question on Eve but I have an idea for something mostly re-usable -

Stock props to get the thing up to an altitude where the atmosphere is like it is on Kerbin at 8km or so.   Then ditch the propellors and activate the nervs to make the run to orbit.

It has 5 NERVs, 2 IONS,  the outboard pair of nervs can be discarded later in the ascent when our TWR is looking good.

Well,  the nerv powered part certainly has a load of potential.  I used hyperedit to drop the thing (stationary) at 10km over the space centre,  and it went hurtling upstairs soon enough.

The problem is, it's my first stock prop,  and it's rubbish.    I followed a Youtube guide,  deviating only in that i used an Oscar B and a pair of fuel cells rather than 4 RTGs, since that still gives 45 minutes minimum endurance and is much cheaper (given that they're not being re-used).  Unfortunately I can't get over 20 m/s on the runway.   I've been experimenting with various pitch angles on the blade,  some of which give better initial acceleration but then stop gaining at 10 m/s or cause RUD.

Anyone fancy working their magic on these props?  Or just graft one of your own subassembly's onto my spaceplane and be done with it?

https://www.dropbox.com/s/1g6mi5jg16ozes2/eve4.craft?dl=0

 

[Geschosskopf]

I really question where you got your ideas on what works on Eve and what doesn't.  All the high-Isp engines (nukes and ions) don't provide much thrust in atmospheres, and Eve's got way more atmosphere than necessary.  Also, Eve's got noticeably more gravity than Kerbin.

If you're only using stock parts, returning from Eve requires a massive amount of LFO rockets of small diameter in a huge number of stages.  If you're using mod parts, there are numerous solutions to Eve SSTOs.

[Helmetman]

@Geschosskopf He said he used stock propellers to 8km or higher even (who knows)
Surely Nervs work better that high (1 atmosphere or there below)

Although I to am surprised 5 nervs can push whatever that's left of that initial 28tons on Eve minus whatever he drops and burns by that point. But I'm sure he thought about that part. 

I to am going to experiment with stock props (never done yet) so I'll follow this thread to see how it goes.

[AeroGav]

24 minutes ago, Helmetman said:

@Geschosskopf He said he used stock propellers to 8km or higher even (who knows)
Surely Nervs work better that high (1 atmosphere or there below)

Although I to am surprised 5 nervs can push whatever that's left of that initial 28tons on Eve minus whatever he drops and burns by that point. But I'm sure he thought about that part. 

I to am going to experiment with stock props (never done yet) so I'll follow this thread to see how it goes.

Here's a test flight I created on Eve,  drops you in the atmosphere about 24km ish...    get into space but not much wiggle room !

Stay on Prograde hold on the SAS,  the inboard elevons on the upper wing are "deployed", if you tweak the "limit authority" slider you can fine tune nose angle.

At 1050-1100 m/s stage to shed the outboard nukes.      A bit disappointed it doesn't do it with a better margin.   The starting point is over 20km, which might be tough to do with props.  Then again it probably doesn't need all those batteries etc.

Other problem is you need a can opener.  Val can't get out ! Maybe use "Take Command" mod and dock it to something, she can leave seat by crew transfer.

[Geschosskopf]

49 minutes ago, Helmetman said:

@Geschosskopf He said he used stock propellers to 8km or higher even (who knows)

True.  Stock "propellers" are the new infinigliders.  So really, why bother?  If you're going to cheat anyway, just use HyperEdit to get back to orbit and save yourself a lot of trouble..

Edited September 20, 2017 by Geschosskopf

[Helmetman]

@Geschosskopf That's the main reason why I haven't really tried stock propellers yet. Then I'd rather used a modeled version from a mod or something like KAX.

But the fun thing in this is combining the stock application with the stock parts, balance and ratios to see how far one can come. 

If it means taking of from eve in a winged craft then we've just given infiniglide 2.0 a whole new description. I probably try the same if Aerogav proves this to be possible.

[AeroGav]

43 minutes ago, Geschosskopf said:

True.  Stock "propellers" are the new infinigliders.  So really, why bother?  If you're going to cheat anyway, just use HyperEdit to get back to orbit and save yourself a lot of trouble..

Can't believe you're making that comparison.     If you have a craft with nuclear reactors, in a thick atmosphere, it really should be possible to use their heat to drive propellers via steam turbine or whatever in order to travel at low speed and altitude around the planet.     Since the game doesn't provide electric propellers or nuclear turbojets,  stock propellers are the only answer if you're trying to create a craft you can share with people who don't want to install mods.      And BTW, stock propellers are hard.  Not quite the same thing as cheating to orbit with Hyperedit.

If your objection is that anything other than a huge rocket is cheating - well, install a modded planet with 2x Kerbin's gravity and no atmosphere,  then you don't have to worry about people making props or planes or using anything other than a giant chemical rocket - bliss !

[Jas0n]

53 minutes ago, Geschosskopf said:

True.  Stock "propellers" are the new infinigliders.  So really, why bother?  If you're going to cheat anyway, just use HyperEdit to get back to orbit and save yourself a lot of trouble..

You have never built either, have you? If you have, you would know that an infiniglider only takes about 2 minutes to make in the SPH, by simply spamming many control surfaces, while stock propellers actually take time and experimentation.

[Geschosskopf]

8 minutes ago, Jas0n said:

You have never built either, have you? If you have, you would know that an infiniglider only takes about 2 minutes to make in the SPH, by simply spamming many control surfaces, while stock propellers actually take time and experimentation.

Actually, I've built both, helped with the development of the "Kraken drive", and was one of the pioneers of the "ladder drive".  I've been playing this game since 0.20, thank you very much.  And there's exactly zero difference between stock "propellers" and infinigliders.  OK, sure, with the old and now defunct infinigliders, it required no power to deflect a control surface (and back then, there was no requirement to maintain EC in anything EXCEPT probes), whereas a stock "propeller" requires power to spin the SAS units.  But seriously, both are equally exploits of loopholes in the game engine, nothing more.  Period, end of story.  Time spent carefully arranging parts makes no difference.  You have to take equal care making a "ladder drive" or "Kraken drive".  So what?

Doing any of these things is against the spirit of the game.  The game gives you a certain selection of parts, mods give you more, and almost all of them are intended to make you face and overcome realistic problems within semi-realistic parameters.  But the game isn't perfect so there are loopholes to exploit.  The stock "propeller" aka "neo-infiniglider" is one such.

[FleshJeb]

And all this time, I thought the spirit of the game was to have fun... Mein Gott! I've been playing wrong!

@AeroGav This looks like a fantastically fun project. You should page Azimech, I'm sure he could give some pointers on the props.

[AeroGav]

32 minutes ago, Geschosskopf said:

But seriously, both are equally exploits of loopholes in the game engine, nothing more.  Period, end of story.  Time spent carefully arranging parts makes no difference.  You have to take equal care making a "ladder drive" or "Kraken drive".  So what?

Doing any of these things is against the spirit of the game.  The game gives you a certain selection of parts, mods give you more, and almost all of them are intended to make you face and overcome realistic problems within semi-realistic parameters.  But the game isn't perfect so there are loopholes to exploit.  The stock "propeller" aka "neo-infiniglider" is one such.

This debate's getting heated - let's all try to calm down and not go accusing each other of things.

I still don't agree that stock propellers are comparable to cheating with infinite fuel etc.      Most seem to be limited to under 160 m/s and 7km on Kerbin.   They are bulky and create huge drag,  and self destruct if you fire up jet engines and try to push them much over their top speed.       It is pretty trivial to build an airplane that can circumnavigate on Duna, Kerbin or Laythe without resorting to stock propellers, but Eve is different.      

I did an experiment with an Aerospike rocket, asparagus staged, and it took 8 tons of rocket to get one ton of upper stage to 20km.      So yes I could  just build a rocket that stages away to a tiny capsule in orbit like countless Youtube videos have done but I am trying to challenge myself by making something different - no-one has built a stock eve spaceplane yet.  

Why are stock props considered cheating but mods aren't,   some mod engines are seriously OP? 

 

[Geschosskopf]

56 minutes ago, AeroGav said:

I still don't agree that stock propellers are comparable to cheating with infinite fuel etc......

I did an experiment with an Aerospike rocket, asparagus staged, and it took 8 tons of rocket to get one ton of upper stage to 20km.      So yes I could  just build a rocket that stages away to a tiny capsule in orbit like countless Youtube videos have done but I am trying to challenge myself by making something different - no-one has built a stock eve spaceplane yet.  

This is easy enough to answer. As I understand things from reading what more knowledgeable folks have written, 1 EC/sec = 1 kJ/sec = 1 kW =~ 1 hp.  The very top-end, high-octane, turbo-supercharged, late-WW2 frontline combat aircraft engines in service use, optimized for power-to-weight ratio, developed about 2500-3000 hp at war emergency power (for short duration, using water, methanol, and/or nitrous oxide injection from a low-capacity tank).  A single RTG produces 0.8 EC/sec =~ 0.8 hp.  Therefore, to get anything remotely approaching realistic power out of a "stock propeller", you need 2500 hp / 0.8 hp/RTG = 3125 RTGs  on EACH SHAFT..

Therefore, stock "propellers" are exploits/cheats same as the old infinigliders.  QED.

Edited September 21, 2017 by Geschosskopf

[Reusables]

Now this is what I was thinking about years. I decided to forget about it, due to the weakness of propellers.

Electric propellers are very weak on its TWR side. I had hard time getting it over 2 on operation. And - Eve has higher gravity, which makes this weakness worse. So 8km on kerbin won't guarantee good high altitude performance on eve. I got a prop plane to 10km with 1g, but it refused to go over 5km with 1.7g.

I recommend rocket-turboprop. It can gain both higher TWR and higher effective ISP in atmosphere, so why not try it?

 

Well, and yeah I agree that it's an exploit, but at least for me it is so fun to make!

[AeroGav]

7 hours ago, Geschosskopf said:

This is easy enough to answer. As I understand things from reading what more knowledgeable folks have written, 1 EC/sec = 1 kJ/sec = 1 kW =~ 1 hp.  The very top-end, high-octane, turbo-supercharged, late-WW2 frontline combat aircraft engines in service use, optimized for power-to-weight ratio, developed about 2500-3000 hp at war emergency power (for short duration, using water, methanol, and/or nitrous oxide injection from a low-capacity tank).  A single RTG produces 0.8 EC/sec =~ 0.8 hp.  Therefore, to get anything remotely approaching realistic power out of a "stock propeller", you need 2500 hp / 0.8 hp/RTG = 3125 RTGs  on EACH SHAFT..

Therefore, stock "propellers" are exploits/cheats same as the old infinigliders.  QED.

I'm not disputing the reaction wheel power output is broken, but the complete engine is still bulky and draggy and only situationally useful.

It is very easy to take a cheap shot at what i am trying to do and yes, you have a simple and irrefutable math argument to back you up.

However, you still haven't answered what I am supposed to do when no stock nuclear turbojet exists.    My craft is carrying the weight of 5 nuclear reactors already ,  are you saying Kerbals are not capable of utilizing that thermal power to run a turbojet, given how advanced their spaceplane tech is in other areas,  and given how bad the alternatives are for Eve ?

Honestly, all I'm getting from your posts on this topic is   "I'm right, you're wrong." . The wording used to deliver each winning argument makes it sound smug ("take that! pow!") or like you're gloating.   Your disapproval at what i am trying to do is obvious, fair enough I suppose you're entitled to it if you think this is so against the spirit of the game.

You've  put me off wanting to pursue this,  so you've won,  hope you feel better knowing there's one less cheaty craft in this world

 

[Spricigo]

The whole "cheating" argument is moot.  The  OP ask for help to build a stock propeller and we should discuss how to do it, not the "ethics" of having fun in single player games.

That said, there are huge odds against the viability of the project. The fact people don't bother with stockpropeller spaceplanes for Kerbin is quite telling.

 

[Helmetman]

@gesschosskopf I'm not particularly against exploits. Infiniglide was just a crude auto orbit function (that is me being crude :P)

Atleast in this case it requires effort, lots of weight, and lots of balancing. The fact that this apparently experienced SSTO flyer comes asking for help probably means hes in a loophole with this, and perhaps pulling his hair out. Getting to build one that may Orbit Eve is a achievement, not a cheat.

I also have never heard of aircraft with WW2 performance being driven by electricity. So if that's the point to debunk stock propellers this project is unrealistic to begin with not even mind the comparison through the numbers you gave us. But you have quite the proven point there concerning the numbers of RTG's. This would never work.

But most values in ksp related to irl applications are off. And it is a exploit of physics after all. The anomaly is just the absurd EC values you get to see. But that's more a result of the exploit rather then that you actually get to see realistic EC usage.

[Geschosskopf]

1 hour ago, Spricigo said:

The whole "cheating" argument is moot.  The  OP ask for help to build a stock propeller and we should discuss how to do it, not the "ethics" of having fun in single player games.

Actually, it's not moot because to solve the OP's problem you have to understand how this exploit works.  Stock props are functionally the same as the ladder drive.  Both rely on the game engine not letting 2 objects occupy the same space.  Thus, if 1 object moves into the space occupied by another, the game moves that other object and all parts attached to it out of the way.  So just as the Kerbal on a ladder head-butts the ship and pushes it forward,  the front end of the prop shaft pushes on the part in front of it.  Because this is simply the result of spatial housekeeping by the game, no notice is taken of the actual force needed to move the object that's in the way.  This is why a fallen Kerbal under a huge rocket can flip it just by standing up. 

The performance of a stock prop is thus determined by how fast the shaft is moving forward relative to the part in front of it.  The faster the shaft moves forward, the further away the part in front gets pushed per frame, so the faster tje rest of the aircraft is dragged along. 

Thus, efforts to improve performance should focus on getting higher RPM on the shaft and increasing the pitch of the prop blades.  This can actually lead to the counter-intuitive result of decreasing the number of SAS in the shaft and thus the EC needed, while making the plane go faster.

I'm not against exploits for having fun.  I use the ladder glitch for bicycles and kayaks.  But that doesn't really impact the believability of the game the way using the same exploit to get an otherwise serious ship off of Eve does.

 The OP seems to be trying to play seriously and attempting a novel solution to getting off Eve, so I was pointing out the method wad an exploit not in keeping with the rest of his game.  In that context, it's not really different from just HyperEditing the ship to orbit.

[Spricigo]

33 minutes ago, Geschosskopf said:

Actually, it's not moot because to solve the OP's problem you have to understand how this exploit works. 

Lets assume he is cheating. So what? 

Its not a challenge and if he claims that is a legitimate way to get out of Eve we can just ignore him. The same way he can use a mod with unbalanced parts, cheat menu , hyperedit or whatever and it will be his concern if that is 'legit' or not because the rest of us really don’t care.

Nonetheless , he seems to be well aware how stock propeller are perceived by the community and already get over that  'cheating' discussion.

[Cpt Kerbalkrunch]

16 hours ago, Geschosskopf said:

If you're only using stock parts, returning from Eve requires a massive amount of LFO rockets of small diameter in a huge number of stages.

I know nothing about stock propellers (except that they look cool) or any of their RL equivalents, so I won't dispute anything you've said and just assume it's all correct. However, since I play strictly stock, I will dispute the above quote because it's simply not true. You seem to have been around for a long time (.20 you said), so I'll assume you meant this is one of the ways of leaving Eve's surface. To say that it's required is misleading and might discourage other players from trying something different.

@AeroGav, I've seen your excellent designs in other threads and, while not a spaceplane or SSTO guy myself, they always impress me in their "cool factor". I don't know if this can be done, but if it is possible, I think the Nervs will have to go. Unless you're using them for RP reasons (i.e. Kerbals are using nuclear power to generate electricity for the props), I think you'll need a little more oomph to get off of Eve. You already know the game, but just remember that a single Dart has 1/3 the mass and 3x the thrust of a Nerv. You'd need ox, of course, but I think the trade off might be worth it. With maybe one or even two Nervs to complete your orbit after you've left the atmosphere. Maybe killing the Darts through an action group once you're high enough. Again though, I know nothing about propellers, so I could be completely wrong. The idea of a reusable Eve lander has intrigued me for a while, though. They say it can't be done, but that's no reason to give up trying.

On a personal note, as a pure stock player, I consider part-clipping to be much more of a cheat than stock propellers. For their cool-factor alone (not to mention all the work and ingenuity that goes into making them) they're acceptable to me. As always, this is just one guy's opinion, though.

[Spricigo]

28 minutes ago, Cpt Kerbalkrunch said:

I don't know if this can be done, but if it is possible, I think the Nervs will have to go. Unless you're using them for RP reasons (i.e. Kerbals are using nuclear power to generate electricity for the props), I think you'll need a little more oomph to get off of Eve.

I tend to agree with this. At least mix and match a bit with darts/vectors (that can be ditched along the way). However I'm also very curious what results AeroGav's experiments will reach.

He seems pretty confident his craft can pull this out if it get enough of a 'head start'. But that is a 50t beast, bound by 1.7g into a thick  atmosphere.

 

on a different note...

Quote

    Since the game doesn't provide electric propellers or nuclear turbojets...

...what I am supposed to do when no stock nuclear turbojet exists.

I don't see why not use mods with that can provide acceptable (and balanced) technology not present in stock game. Even if one is against still 'unproven' technology like nuclear turbojets or air-augmented rockets certainly there is less motive to oppose electric propellers or rocket engines optimized for where you are going. Sure, some people will avoid the modded craft and even tell you that is a 'lesser' achievement but as you noticed the same happens for stock propellers.

But that don't really matter, if you are set to do it for the challenge and rule of cool that is as good motive as any other. Don't waste your time with the naysayers and have fun.

 

[Geschosskopf]

5 hours ago, Spricigo said:

Lets assume he is cheating. So what? 

You obviously didn't read the part about how to get nore performance out of them, which wad the original question.  You can't optimize the things until you know how the exploit works.

Stock props technically don't actually move entire planes with the thrust from their blades.  That moves only the shaft itself, and for this the EC required is as OK as for any other electrical thing in the game.

What moves the plane is a physics-less spatial adjustment to prevent the shaft from clipping into the part in front of it as the shaft moves forward.  Newton's 2nd and 3rd laws are ignored during this adjustment, but this movement still causes wings to make lift.  That's how the tiny amount of EC makes a big plane fly.

So, to fly higher and faster, you need to increase the forward velocity of the shaft, so this spatial adjustment happens more often and with greater magnitude.  However, the prop needs air for the shaft to move so ypu can only get so high, whereas a ladder drive works in space

[Spricigo]

1 minute ago, Geschosskopf said:

You obviously didn't read...

 

6 hours ago, Spricigo said:

..because the rest of us really don’t care.

 

8 minutes ago, Geschosskopf said:

However, the prop needs air for the shaft to move so you can only get so high, whereas a ladder drive works in space

Well, that is up to AeroGav to find out if is enough for if is enough for his purposes. Besides, he may have fun with his self-imposed challenge even if he don't succeed.

[Reusables]

If you keep going for electric propellers...

Here's my design on propeller SSTO on kerbin. It uses Aerospike + Nerva combination.

I think ions are too weak to get this work, as the drag is too much. Also, I found later that mixing engine resulted in worse performance. So I recommend choose one best engine to use.

Also this thread helps greatly with propeller design:

Besides, I observed that the drag of the total plane matches with the lift generated from the propellers..

Edited September 21, 2017 by Reusables

[Azimech]

23 hours ago, Geschosskopf said:

True.  Stock "propellers" are the new infinigliders.  So really, why bother?  If you're going to cheat anyway, just use HyperEdit to get back to orbit and save yourself a lot of trouble..

You'll find that designing a proper engine and propeller is quite a challenge. There's some real engineering here.

[AeroGav]

15 minutes ago, Geschosskopf said:

You obviously didn't read the part about how to get nore performance out of them, which wad the original question.  You can't optimize the things until you know how the exploit works.

Stock props technically don't actually move entire planes with the thrust from their blades.  That moves only the shaft itself, and for this the EC required is as OK as for any other electrical thing in the game.

What moves the plane is a physics-less spatial adjustment to prevent the shaft from clipping into the part in front of it as the shaft moves forward.  Newton's 2nd and 3rd laws are ignored during this adjustment, but this movement still causes wings to make lift.  That's how the tiny amount of EC makes a big plane fly.

So, to fly higher and faster, you need to increase the forward velocity of the shaft, so this spatial adjustment happens more often and with greater magnitude.  However, the prop needs air for the shaft to move so ypu can only get so high, whereas a ladder drive works in space

OK, thankyou this is constructive at least.

Overall it doesn't look worth the very great effort required to make something like this work,  if the results aren't "authentic".   Also I have doubts the average person has the patience to faff around with the props.  If anyone has a good working engine by all means graft it onto the craft file and have a go.

2 hours ago, Spricigo said:

I tend to agree with this. At least mix and match a bit with darts/vectors (that can be ditched along the way). However I'm also very curious what results AeroGav's experiments will reach.

He seems pretty confident his craft can pull this out if it get enough of a 'head start'. But that is a 50t beast, bound by 1.7g into a thick  atmosphere.

 

3 hours ago, Cpt Kerbalkrunch said:

I think the Nervs will have to go. Unless you're using them for RP reasons (i.e. Kerbals are using nuclear power to generate electricity for the props), I think you'll need a little more oomph to get off of Eve. You already know the game, but just remember that a single Dart has 1/3 the mass and 3x the thrust of a Nerv

It already goes to orbit (i have tested that several times with hyperedit )  provided you can somehow get it above 20km or so at flying speed (not stalled).    At this altitude the air is about the same thickness as it is on Kerbin at 7km.  Below that point the ISP and thrust fall away to practically nothing.

However,  the problem is getting it up there.    If we rule out propellers,  that leaves only rockets.   I tested all the stock ones with hyperedit and the Dart (aerospike) has the best ISP at Eve sea level.     However,  even an asparagus staged rocket built with these engines,  would be 8 times heavier than the payload it can deliver to 20km.

So you'd need a 400 ton lifter to get this 50 ton airplane to 20km.    Even if the airplane all makes it to orbit and is recovered back to Kerbin, that's great but what about the 400 ton booster you just left to crash?       Instead of a nuke airplane upper stage that does the whole haul from 20km to orbit bringing all of itself into space,  you should just keep staging and shedding mass, reaching orbit with an Ant and a Command chair.     OK, virtually nothing of the ascent vehicle makes it space and is recoverable, but the booster stage is likely to be a lot less than 400 tons.

Perhaps there's some optimisation of this approach that could be done.    I'm not used to rockets and calculating how to size each stage.   It looks like what I have in the picture above is a grossly oversized second stage that's trying to do too much and hitting diminishing returns.    I'm gonna let this rest for a bit , can't really see a way forward right now.