Stock Turboprop Endurance Record

[Gman_builder]

42 minutes ago, Pds314 said:

Download the craft. It's up. I've since made minor improvements, but its basically the same design. Two Avionics nosecones facing into each other with the antennas as the axle. Antennas are, insofar as I can tell, infinitely thin, so don't give them much room to wobble.

On a related note, I wonder if strutting the prop blades on would reduce the variation in rotor speed? I notice a significant amount of sudden contraction and expansion causing rapid adjustments of several rad/s that could be causing damage. I know that without the prop blades, it can reach 61 without issue.

Ya Azimech's engine has heavy strutting between props and to the shaft. Seems to help a lot. Is it up on KerbalX? Where is it up?

Edited July 12, 2016 by Gman_builder

[Pds314]

5 minutes ago, Gman_builder said:

Ya Azimech's engine has heavy strutting between props and to the shaft. Seems to help a lot. Is it up on KerbalX? Where is it up?

Google drive. Click the download link on previous page.

[Pds314]

Made a light aircraft. It has a pretty decent climb rate and speed. About 100 m/s in level flight at 4000 meters is pretty doable. May improve the prop or something before my actual run:



In a test, the range was 330 km, including splashdown distance, but I may improve it somewhat so that's not gonna be my entry.

A note: yes: the massive solar panels are important. They are in fact the turbine blades.

Edited July 12, 2016 by Pds314

[Gman_builder]

17 minutes ago, Pds314 said:

Made a light aircraft. It has a pretty decent climb rate and speed. About 100 m/s in level flight at 4000 meters is pretty doable. May improve the prop or something before my actual run:



In a test, the range was 330 km, including splashdown distance, but I may improve it somewhat so that's not gonna be my entry.

A note: yes: the massive solar panels are important. They are in fact the turbine blades.

I like your designs of bearings and engines. Very unorthodox!

3 hours ago, Pds314 said:

Google drive. Click the download link on previous page.

There is no link of any kind on the other page. Post another one.

[Pds314]

5 minutes ago, Gman_builder said:

I like your designs of bearings and engines. Very unorthodox!

There is no link of any kind on the other page. Post another one.

The plane is nice and light, at under 6 tonnes empty, but the engine isn't safe over 42 Rad/s. This means that immediately after takeoff, before reaching ~50 m/s, you must either lower the throttle or adjust the pitch of the prop.

Here's the link again: https://drive.google.com/file/d/0Bx5IDYRs0obMbnUxUENEaC1VMDA/view?usp=sharing

Edited July 12, 2016 by Pds314

[Gman_builder]

Just now, Pds314 said:

The plane is nice and light, at under 6 tonnes empty, but the engine isn't safe over 42 RPM. This means that immediately after takeoff, before reaching ~50 m/s, you must either lower the throttle or adjust the pitch of the prop.

Here's the link again: https://drive.google.com/file/d/0Bx5IDYRs0obMbnUxUENEaC1VMDA/view?usp=sharing

Ok, that definitey wasn't there before.

[Pds314]

1 minute ago, Gman_builder said:

Ok, that definitey wasn't there before.

It was labeled "download" before.

The little plane has 50 kN*m of torque from 6 engines. So at 40 rad/s, that's a solid 2 Megawatts of power output, better than any WW2 fighter.

Edited July 12, 2016 by Pds314

[Gman_builder]

9 minutes ago, Pds314 said:

It was labeled "download" before.

I don't really know whats going on with your engine. But I can't activate the decoupler from the staging. When I go to click decouple manually it only give me the "enable crossfeed" option. The Junos don't run unless I enable crossfeed.  I also can't control prop pitch or throttle. I have no idea why. It's just always stuck on 50% throttle and 30RAD/s regardless of what throttle I input. It's acting like the blowers are a spate craft.

[Pds314]

7 minutes ago, Gman_builder said:

I don't really know whats going on with your engine. But I can't activate the decoupler from the staging. When I go to click decouple manually it only give me the "enable crossfeed" option. The Junos don't run unless I enable crossfeed.  I also can't control prop pitch or throttle. I have no idea why. It's just always stuck on 50% throttle and 30RAD/s regardless of what throttle I input. It's acting like the blowers are a spate craft.

Yes, that engine needed infinite fuel to operate. And the staging was wrong. You also need to make sure physics.cfg is modified to support high rotation rates and FAR is not installed.

I think I'll upload my little plane. Design is 40 rad/s, max is 42. Try to stay above 38.

Press space twice to start engine. Be sure to correct for the 50 kN*m engine torque. It can reach about 135 m/s in level flight near sea level. (ironic it doesn't go faster, considering the engine is more powerful than any WW2 fighter engine. I guess the prop is probably of inferior quality to real ones).


DOWNLOAD [Propler R1 single engine turboprop]

Edited July 12, 2016 by Pds314

[Gman_builder]

20 minutes ago, Pds314 said:

Yes, that engine needed infinite fuel to operate. And the staging was wrong. You also need to make sure physics.cfg is modified to support high rotation rates and FAR is not installed.

I think I'll upload my little plane. Design is 40 rad/s, max is 42. Try to stay above 38.

Press space twice to start engine. Be sure to correct for the 50 kN*m engine torque. It can reach about 135 m/s in level flight near sea level. (ironic it doesn't go faster, considering the engine is more powerful than any WW2 fighter engine. I guess the prop is probably of inferior quality to real ones).


DOWNLOAD [Propler R1 single engine turboprop]

Ya I have modified the physics.cfg and I do not have FAR. But it is definitely stuck at 30 RAD/s

[Pds314]

2 minutes ago, Gman_builder said:

Ya I have modified the physics.cfg and I do not have FAR. But it is definitely stuck at 30 RAD/s

It shouldn't be... hmm.. Have you made sure the physics.cfg is currently working right?

[Gman_builder]

9 minutes ago, Pds314 said:

It shouldn't be... hmm.. Have you made sure the physics.cfg is currently working right?

Uh... ya. I'm pretty sure the game wouldn't run if the physics.cfg wasn't working.

[Pds314]

2 minutes ago, Gman_builder said:

Uh... ya. I'm pretty sure the game wouldn't run if the physics.cfg wasn't working.

I mean edited. Mine used to be editted until 1.1.3 and then it undid itself.

[Gman_builder]

Just now, Pds314 said:

I mean edited. Mine used to be editted until 1.1.3 and then it undid itself.

huh... wow you were right. It did undo itself!

[Pds314]

6 minutes ago, Gman_builder said:

huh... wow you were right. It did undo itself!

I think it sometimes redownloads the physics.cfg

[Gman_builder]

8 minutes ago, Pds314 said:

I think it sometimes redownloads the physics.cfg

Weird. I guess that's why when I tried to fly my 224 m/s plane in FAR it couldn't even get above 40 m/s.

I wonder, in the physics.cfg for the max angular velocity, if you just put   NaN  what would happen. would there just be no limit? Maybe the infinity symbol would do it....

Edited July 12, 2016 by Gman_builder

[Pds314]

I think I'll make a twin-engine bomber next, that is, assuming I can get twin engines to work. While, yes, increasing radius increases efficiency and power, it also makes takeoff and powered landing quite difficult.

 

I suppose increasing rpm also reduces the required torque, but from the looks of it, anything over 500 rpm for the prop itself is pure fantasy. Even the most stable engine I currently have operational fails running just a shaft at 600 rpm.

 

If anyone wants to attempt to derive, from first principles, the math behind rotor shaft stability as a function of physics time delta, rotor rpm, and whatever other variables apply, please do. It would help everyone to design faster engines. Maybe even exceed the magical pi radians/tick level

Edited July 12, 2016 by Pds314

[Gman_builder]

8 minutes ago, Pds314 said:

I think it sometimes redownloads the physics.cfg

 

2 minutes ago, Pds314 said:

I think I'll make a twin-engine bomber next, that is, assuming I can get twin engines to work. While, yes, increasing radius increases efficiency and power, it also makes takeoff and powered landing quite difficult.

 

I suppose increasing rpm also reduces the required torque, but from the looks of it, anything over 500 rpm for the prop itself is pure fantasy.

I did a test and my game gets upset at 60 rad/s. So theoretically your max prop speed depends on your machine and install.

[Pds314]

9 minutes ago, Gman_builder said:

 

I did a test and my game gets upset at 60 rad/s. So theoretically your max prop speed depends on your machine and install.

Yes. Without a practical prop, 60 rad/s or better is possible. I haven't seen any engine capable of doing anywhere close with a prop that it can actually turn without stalling. Above a certain rpm, the jitter might reduce due to turning more than half way around every tick.

Edited July 12, 2016 by Pds314

[Gman_builder]

Just now, Pds314 said:

Yes. Without a practical prop, 60 rad/s or better is possible. I haven't seen any engine capable of doing anywhere close with a prop that it can actually turn without stalling.

Ya same. God I wish this game had fluid dynamics and better support for this stuff so we could build REAL engines. Until that we will just have to deal with these crapy engines we can make.

[Pds314]

45 minutes ago, Gman_builder said:

Ya same. God I wish this game had fluid dynamics and better support for this stuff so we could build REAL engines. Until that we will just have to deal with these crapy engines we can make.

Yeah. Though, to be fair, they aren't bad power/weight wise. That little plane I made has an engine consisting of:

1500 kg of Junos.

240 kg of solar panels for turbine blades.

200 kg of structural fuselage.

240 kg of avionics nose cones.

24 kg of cube struts.

6 kg of octo struts

300 kg of fuel ducts

50 kg of decoupler.

 

That's 2560 kg plus the prop and nosecone. 2 Megawatts over 2560 kg is not excellent, but its about the same as mid-late 30s engines. Granted, the fuel efficiency is awful. No engine ever in an aircraft had such high power-specific fuel consumption.

Hmm.. Maybe in addition to the twin-engine bomber, I'll make a tiny plane with only 2 blowers and an open cockpit.

Edited July 12, 2016 by Pds314

[Gman_builder]

1 hour ago, Pds314 said:

Yeah. Though, to be fair, they aren't bad power/weight wise. That little plane I made has an engine consisting of:

1500 kg of Junos.

240 kg of solar panels for turbine blades.

200 kg of structural fuselage.

240 kg of avionics nose cones.

24 kg of cube struts.

6 kg of octo struts

300 kg of fuel ducts

50 kg of decoupler.

 

That's 2560 kg plus the prop and nosecone. 2 Megawatts over 2560 kg is not excellent, but its about the same as mid-late 30s engines. Granted, the fuel efficiency is awful. No engine ever in an aircraft had such high power-specific fuel consumption.

Hmm.. Maybe in addition to the twin-engine bomber, I'll make a tiny plane with only 2 blowers and an open cockpit.

I just threw together a engine in 30 minutes to an experiment and it ended up doing 50 rad/s at half throttle! WOW! I have got some work ahead of me tonight!

EDIT: Makes 40 rad/s before the axle comes out of the frame for whatever reason. But with a small prop on the front it does 7 rad/s  how does that even work

Edited July 12, 2016 by Gman_builder

[Gman_builder]

10 hours ago, Azimech said:

Chakora v1 doesn't. The one I did my latest speedrun with runs 47 ;-)

I had a revelation just now about the blowers on turboprops. I realized, Panther's thrust increases dramatically with afterburner on at altitude. So, if you could get to high altitude with your plane than the thrust from the blowers would increase, which would increase RPM on the prop and the engine would become more efficient nd produce more thrust. Juno's are limited to low altitude and subsonic speed. So theoretically you could take a turboprop supersonic by using panthers. Testing now.

[Pds314]

1 hour ago, Gman_builder said:

I had a revelation just now about the blowers on turboprops. I realized, Panther's thrust increases dramatically with afterburner on at altitude. So, if you could get to high altitude with your plane than the thrust from the blowers would increase, which would increase RPM on the prop and the engine would become more efficient nd produce more thrust. Juno's are limited to low altitude and subsonic speed. So theoretically you could take a turboprop supersonic by using panthers. Testing now.

Interesting. One thing to point out is that encountering the sound barrier might reduce prop efficiency. The effects aren't fully simulated in KSP, but the efficiency of a supersonic propeller is likely considerably lower than that of a subsonic one. Say you have a prop turning at 40 rad/s as it approaches the sound barrier, and the blades are 4 meters from the hub, you have a horizontal speed component of 160 m/s, and let's say a linear speed component of 310 m/s.

Your prop blades are now moving 349 m/s. This means they are supersonic. This considerably reduces their L/D, yet also requires the advance ratio to be more than 2.0 to generate meaningful thrust. So let's say your prop is getting an L/D of 4? That means that in order for the prop to overcome its own drag, it must have an advance ratio of less than 4, but in order to generate that L/D of 4, it needs at least several degrees of AOA on the airstream. There's a very slim margin where the prop is generating useful thrust that's also capable if overcoming the prop's own drag. Add in the drag of the aircraft and you start to see why supersonic props are mindbogglingly inefficient.

 

Then again, you could fix some of these things. Change the required advance ratio by spinning the prop faster (dangerous) or making it wider (draggy). Improve supersonic aerodynamics by using swept props (inefficient at low speeds, may be hard to control pitch, may cause structural problems). Perhaps a 50 rad/s prop with swept blades centered 6 meters out would have more promising supersonic behavior.

Edited July 12, 2016 by Pds314

[Azimech]

5 hours ago, Pds314 said:

 It can reach about 135 m/s in level flight near sea level. (ironic it doesn't go faster, considering the engine is more powerful than any WW2 fighter engine. I guess the prop is probably of inferior quality to real ones).
 

Inferiour? Maybe. But it's got to do with RPM, prop diameter and number of blades.