Auto-balance VTOL thrust?

[Tokamak]

I'm a long-time KSP player, just getting back into the game after a few years, and for the first time trying to seriously play with aircraft.

 

I'm sure this question has been asked a zillion times before, but apparently I fail at choosing search terms.

Is there a way, I assume a mod, to dynamically balance thrust from multiple engines to keep the center of thrust in line with the center of mass? Or, to be more specific... it is incredibly fiddly to get a VTOL aircraft perfectly balanced, especially as fuel tanks drain. If you had magic reflexes you could in principle vary the thrust limits on all of the engines to keep the thing balanced. In reality, not so much. But surely there must be a mod for this. 

Like I said, I've searched, but searching for things like "ksp mod VTOL balance thrust" gets me a huge list of discussions containing those words, but nothing actually apropos.

Actually, it occurs to me that, absent dynamic balancing, even something that lets you see the CoM and CoT in flight would be a lot better than nothing, since you could manually balance tanks. That would still be a better option than just gunning it and seeing if your craft flips over or not. XD

[HvP]

@Tokamak I know of two mods that do something similar to what you are asking. But rather than balance the engine thrust, they both move fuel around your craft to keep the center-of-mass in the same position. I have not personally used any of these mods, but a quick review of the links below makes me think that something here should work for what you want.

PWB Fuel Balancer Restored which focuses on allowing you to set a center-of-mass marker in the VAB and it will adjust fuel levels as necessary to keep that COM constant during flight.

and

TAC Fuel Balancer which includes other fuel transfer options as well as the ability to maintain a consistent center-of-mass if desired makes all tanks drain evenly, but requires balanced placement to begin with.

You may find this mod helpful, if a bit over-automated: Vertical Velocity Controller Redux. It will allow you to enter a desired hover altitude and then will automate the process of maintaining that altitude, including compensating for the pitch angle of the craft.

Then there's the truly indispensable RCS Build Aid Continued which allows you to fine tune the placement of engines and thrusters in the VAB to carefully eliminate any unwanted torque. It will also show you where your center-of-mass moves.

And, of course, a huge thanks to @linuxgurugamer for maintaining a truly massive collection of mods, the lifeblood of KSP!

Happy flying!

Edited May 20, 2020 by HvP

[Tokamak]

Thank you for the info!

 

And yeah, @linuxgurugamer contributes a truly absurd amount to the community, and deserves much thanks.

[HvP]

2 minutes ago, Tokamak said:

Thank you for the info!

You're welcome.

I also just amended my post to include a link to RCS Build Aid. I don't even attempt building craft without it anymore.

[Tokamak]

I'm not seeing anything related to CoM in TAC fuel balancer, which I already had installed. Do you just mean the "balance" tanks option? I thought that just kept them all equally full, which isn't always the same thing as keeping the CoM constant. Though even that function is better than nothing.

4 minutes ago, HvP said:

You're welcome.

I also just amended my post to include a link to RCS Build Aid. I don't even attempt building craft without it anymore.

Oh, neat. I will also look at that one. If I understand correctly, it is only applicable in the VAB, but it still seems useful. Thanks!

[Misguided Kerbal]

@Tokamak there's this mod, called throttle controlled avionics. It (quote) "TCA is a plugin that enhances the attitude control of a ship by dynamically changing the output of its engines and RCS thrusters. Even with most unbalanced designs TCA maintains stable flight and quick precise response to user or autopilot input. TCA also provides many sophisticated autopilot programs based on this core functionality, including waypoint navigation and automatic landing. It is also fast enough to simultaneously control a whole squadron of ships without much overhead." I personally use it a lot for helicopters and VTOLs.

 

 

[HvP]

I've not used it myself, but I think you're right.

The balance tanks option relies on making sure that the tank placement was balanced already in the VAB and that the COM wouldn't change when empty. Which really is no longer a problem because the way tanks drain in KSP was already changed to drain evenly several updates ago. I guess TAC Fuel Balancer isn't going to add the functionality you need after all.

...

Bingo @Misguided_Kerbal! Thanks, that looks like the one. I couldn't think of the name of it.

Edited May 20, 2020 by HvP

[Tokamak]

1 minute ago, Misguided_Kerbal said:

@Tokamak there's this mod, called throttle controlled avionics. It (quote) "TCA is a plugin that enhances the attitude control of a ship by dynamically changing the output of its engines and RCS thrusters. Even with most unbalanced designs TCA maintains stable flight and quick precise response to user or autopilot input. TCA also provides many sophisticated autopilot programs based on this core functionality, including waypoint navigation and automatic landing. It is also fast enough to simultaneously control a whole squadron of ships without much overhead." I rsonally use it a lot for helicopters and VTOLs.

 

 

So many new mods to play with @.@

[KerikBalm]

1 hour ago, Tokamak said:

If you had magic reflexes you could in principle vary the thrust limits on all of the engines to keep the thing balanced. In reality, not so much. But surely there must be a mod for this. 

I would like such a feature... BG gives you some ability to do this with the KAL-1000 controller, but you have to set it up, it would be nice if SAS could do this.

I have a similar set up with motor torque for quad copters (which previously I used for pitch, roll, and yaw, but now only for yaw since the 1.9 update with cyclic and collective control settings.

You could set it up to adjust fore and rear engine thrust limits to trim your VTOL, or have a cruder mixing that goes along with the control inputs (default wasd), but then its binary.

If your don't have breaking ground, you can do what I did,

In the case of this VTOL, I would pre-adjust the thrust settings for the VTOL burn, using the VAB/SPH to estimate the right throttle setting... this requires a relatively small amount of CoM shift during the burn though

Note the small 2nd engine plume on each side of the pic above, vs the full size plumes below... due to different fuel loads and payload

Or what I did here (sorry, no good pics of the sytem:

Just below the tri-cluster of Aerospikes, I have a vertically facing aerospike. Since its far from the CG, I would just have that part window open, and adjust the thrust limit slider as needed for trim... now i could just do it with an axis group (this was pre-axis groups). You can easily have your VTOLs balance controlled by just shifting the thrust of 1 engine.

Just have 1 "balancing" engine. I liken it to the horizontal tailrotor on this thing:

https://en.wikipedia.org/wiki/LTV_XC-142

 

[Tokamak]

Hokay, TCA is going to take some figuring out. I can get the basic thrust balancing, but I can't for the life of me figure out how to access any of the modules, like landing and altitude holding.

Not asking for help, just muttering.

[Vanamonde]

This discussion of add ons has been moved to Add-on Discussions. 

[Tokamak]

On 5/21/2020 at 9:31 AM, Vanamonde said:

This discussion of add ons has been moved to Add-on Discussions. 

Whoops. Sorry.

[DeadJohn]

One more option for VTOL balancing: Mk2 Expansion includes RCS-like thrusters powered by just atmosphere and electricity. The part is called "Configurable ACS Blister". Get your craft close to balanced with the main VTOL engine, then add a few ACS thrusters for maneuvering and to compensate for fuel imbalance.

Small VTOL drones can be powered by nothing but thrusters; no engines and no control surfaces needed.  Larger VTOL craft still need engines unless you install dozens of ACS thrusters and crazy amounts of electricity to keep them powered.

For vacuum worlds without atmosphere, there's a similar "Configurable OMS Blister" powered by LFO.

the mkl2

[DStaal]

On 5/21/2020 at 3:03 AM, Tokamak said:

Hokay, TCA is going to take some figuring out. I can get the basic thrust balancing, but I can't for the life of me figure out how to access any of the modules, like landing and altitude holding.

Not asking for help, just muttering.

TCA tries to have a progression with the tech tree - you have to unlock the modules, and then enable them in the VAB/SPH for any particular ship.  (You can set a particular configuration as default - I tend to hit the 'enable all' and then the 'save as default' buttons any time I've made a major change in the tech tree.)

Some of the modules do take a bit of getting used to to get to work - and note that TCA *only* controls the throttles, while being a full autopilot.  Sometimes depending on your design it'll work a lot better with a twitch or a spider engine pointing up or something, just so that TCA has an option to put thrust in that direction.

[RandomKerbal]

Ummm, so what's the final solution?

[DStaal]

3 hours ago, RandomKerbal said:

Ummm, so what's the final solution?

I don't know what Tokamak went with - but almost always if you're doing VTOL, the mod to reach for is TCA.  There are some others that are helpers to build something you can control manually, or some that allow you to build specific ships (or at least with specific parts), but the general-purpose solution is TCA.

[Kindpie1994]

 

Spoiler

 

Hey I think I might know how to help with your thread question!  I play on XBOX so I have been using the most VANILLA of vanilla KSP versions. With 100% STOCK VTOL tilt engine with zero mods. It took me a while to understand how the programming behind how KSP runs as well as real day studies to make a VTOL jet fighter without the need for stability/thrust balancing mods. The jet can hover with excellent stability & hold at altitude. Can perform sharp manoeuvres while in ‘VTOL mode’ to either reorient the jet or to quickly shave off speed for a quick but smooth touch down. It can dogfight successfully at all altitudes @ or below 20km ASL. check out the links below and lemme know what you think? If so flick me a message!!  

F-35b Lightning II- unloaded

Part count: 91

Cost: 64,316

Mass: 14.3t

Height: 3.5m

Width: 8.6

Length: 12.5

https://imgur.com/user/alexiichristidis

https://imgur.com/gallery/f0NDJxR

https://imgur.com/gallery/918HyM4

https://imgur.com/gallery/9rFoHaX

 

 

 

7 minutes ago, Kindpie1994 said:

 

  Hide contents

 

Hey I think I might know how to help with your thread question!  I play on XBOX so I have been using the most VANILLA of vanilla KSP versions. With 100% STOCK/zero mods.. check out the links below and lemme know what you think? If so flick me a message!!  

F-35b Lightning II- unloaded

Part count: 91

Cost: 64,316

Mass: 14.3t

Height: 3.5m

Width: 8.6

Length: 12.5

https://imgur.com/user/alexiichristidis

https://imgur.com/gallery/f0NDJxR

https://imgur.com/gallery/918HyM4

https://imgur.com/gallery/9rFoHaX

 

 

 

 

Edited July 13, 2020 by Kindpie1994
Accident

[RandomKerbal]

18 hours ago, Kindpie1994 said:

 

  Reveal hidden contents

 

Hey I think I might know how to help with your thread question!  I play on XBOX so I have been using the most VANILLA of vanilla KSP versions. With 100% STOCK VTOL tilt engine with zero mods. It took me a while to understand how the programming behind how KSP runs as well as real day studies to make a VTOL jet fighter without the need for stability/thrust balancing mods. The jet can hover with excellent stability & hold at altitude. Can perform sharp manoeuvres while in ‘VTOL mode’ to either reorient the jet or to quickly shave off speed for a quick but smooth touch down. It can dogfight successfully at all altitudes @ or below 20km ASL. check out the links below and lemme know what you think? If so flick me a message!!  

F-35b Lightning II- unloaded

Part count: 91

Cost: 64,316

Mass: 14.3t

Height: 3.5m

Width: 8.6

Length: 12.5

https://imgur.com/user/alexiichristidis

https://imgur.com/gallery/f0NDJxR

https://imgur.com/gallery/918HyM4

https://imgur.com/gallery/9rFoHaX

 

 

 

 

What is this? I don't see this is related.

Edited July 14, 2020 by RandomKerbal

[Kindpie1994]

How so? 

 

Hey I think I might know how to help with your thread question!  I play on XBOX so I have been using the most VANILLA of vanilla KSP versions. With 100% STOCK VTOL tilt engine with zero mods. It took me a while to understand how the programming behind how KSP runs as well as real day studies to make a VTOL jet fighter without the need for stability/thrust balancing mods. The jet can hover with excellent stability & hold at altitude. Can perform sharpmanoeuvres while in ‘VTOL mode’ to either reorient the jet or to quickly shave off speed for a quick but smooth touch down. It can dogfight successfully at all altitudes @ or below 20km ASL. check out the links below and lemme know what you think? If so flick me a message!!  

F-35b Lightning II- unloaded

Part count: 91

Cost: 64,316

Mass: 14.3t

Height: 3.5m

Width: 8.6

Length: 12.5

https://imgur.com/user/alexiichristidis

https://imgur.com/gallery/f0NDJxR

https://imgur.com/gallery/918HyM4

https://imgur.com/gallery/9rFoHaX

 

[DStaal]

3 minutes ago, Kindpie1994 said:

How so? 

It's just a few shots of a single plane that presumably has VTOL capabilities.  It doesn't answer what was done to balance the thrust on it, or any other design.  All it really shows is that it is possible to make a VTOL - which was never in question.

And I'm certain it doesn't deal with dynamically balancing that thrust as the CoM/CoG moves during flight, which was the question asked.

[Kindpie1994]

12 minutes ago, DStaal said:

It's just a few shots of a single plane that presumably has VTOL capabilities.  It doesn't answer what was done to balance the thrust on it, or any other design.  All it really shows is that it is possible to make a VTOL - which was never in question.

And I'm certain it doesn't deal with dynamically balancing that thrust as the CoM/CoG moves during flight, which was the question asked.

Okay well if Person who asked the question likes what he see’s then as I said in my original message, they’re free to message me to know how. Saves having to explain it all to begin with until someone shows interest and decides to ask & exchange other potential options to making a stable VTOL via balancing thrust on multiple engines.. also its the only stable VTOL on the net that I’ve seen so far.. & that can be done without mods. Haha but yeh.. it’s not really up for debate whether you think my craft is legit or not   It is VTOL and the knowledge I used to make it what it is, is exactly what the thread user seeks to know. Yeh mods are fun but using & training your brain is better. 

[DStaal]

I'll admit I’m using modded parts, but there are three stable VTOLs in this picture:

https://magehandbook.com/owncloud/index.php/s/mK66F8Zf9botcwx/download

Making a stable VTOL wasn't even the question - the question was about auto-balancing thrust.  Which we've pointed them towards.  Just pointing at pictures of a VTOL you've made doesn't answer the question.  (I don't *care* if the VTOL in the picture is legit.)

[Kindpie1994]

Well... the whole point people play Kerbal Space Program is the thrill of learning! Using Mods for aesthetic purposes or  additional parts that don’t exist in vanilla STOCK KSP makes it all the more better BUT... to use a mod that auto balances thrust and COM/COG/COL. The maths to it is pretty simple haha.. so you don’t really have a leg to stand on in ur argument haha. I’ve offered more authentic help on the thread and given a few links to get the ball rolling despite the question being different.... what the original thread user inevitably wishes to achieve is making a stable VTOL. They asked for mods coz they don’t know how to balance the thrust as compensation for inflight transition etc.

 

happy engineering 

[DStaal]

5 hours ago, Kindpie1994 said:

Well... the whole point people play Kerbal Space Program is the thrill of learning! Using Mods for aesthetic purposes or  additional parts that don’t exist in vanilla STOCK KSP makes it all the more better BUT... to use a mod that auto balances thrust and COM/COG/COL. The maths to it is pretty simple haha.. so you don’t really have a leg to stand on in ur argument haha. I’ve offered more authentic help on the thread and given a few links to get the ball rolling despite the question being different.... what the original thread user inevitably wishes to achieve is making a stable VTOL. They asked for mods coz they don’t know how to balance the thrust as compensation for inflight transition etc.

 

happy engineering 

And if you'd said anything like that you'd at least have been on topic.  Instead you just showed pictures of a fighter jet in KSP, and told us how well it performs as a fighter.

[Kindpie1994]

14 hours ago, DStaal said:

And if you'd said anything like that you'd at least have been on topic.  Instead you just showed pictures of a fighter jet in KSP, and told us how well it performs as a fighter.

Considering not many players has been able to sustain altitude & stability in VTOL mode along with everything else  on top  that I mentioned before served as credibility. You can’t  sell anyone on anything without proof.. haha regardless of whether u think it’s relevant or not.