Kerbal Joint Reinforcement as stock?

[clivman]

Poor design is poor design.

Claw's Stock Plus, giving tweakable to gimbal range/reaction wheel force fixes the SAS problem without touching joints. So, KJR - still nah.

Poor design is poor design, you shouldn't have included a cargo bay on your ship. So no bugfixes to get rid of the Kraken.

The logic on these forums......

Edited September 20, 2015 by clivman

[Jouni]

Wobble is 90% bad rocket design and 10% bad game design. KJR removes a large part of that 10%, but it also makes the game less fun, as you no longer have to worry about structural integrity.

In the real world, tall structures are never rigid. They always either bend or break. In KSP, a rocket can only bend at joints, which leads to unintuitive behavior. Because the stiffness of each joint depends only on node size, an interstage with an engine, a decoupler, a probe core, and a reaction wheel module will bend and wobble more than an interstage with just an engine and a decoupler.

If I remember correctly, KJR tries to fix this by adding something similar to invisible struts between the parts in the same stack. This makes the rockets too rigid for my taste. I would prefer another solution, where the overall bendiness of the stack depends only on its width and height. Individual joints would be stiffer in the region of the stack with many small parts than between large fuel tanks.

[Majorjim!]

Gentlemen please. No you do not need this as stock. You need to learn how to use struts. One or two between each tank will stop the wobble.

[Bloody_looser]

Poor design is poor design, you shouldn't have included a cargo bay on your ship. So no bugfixes to get rid of the Kraken.

The logic on these forums......

Wut? Cargobay? We were kinda talking about SAS induced wobbling.

You tell me about logic.

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Gentlemen please. No you do not need this as stock. You need to learn how to use struts. One or two between each tank will stop the wobble.

The truth had been spoken.

[clivman]

Gentlemen please. No you do not need this as stock. You need to learn how to use struts. One or two between each tank will stop the wobble.

Yeah more struts lower FPS! Seriously, we don't have life support and they expect us to make the struts that go on the INSIDE of a rocket. You can't use struts in a vertical stack and you know what rockets are, TALL and SKINNY. If you want to change reality to be less fun in a game, please just do it in a mod.

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Wut? Cargobay? We were kinda talking about SAS induced wobbling.

You tell me about logic.

My point is just because a feature is broken and there is a way around it doesn't mean you can't fix it.

[DocMoriarty]

I don't think it should be stock. This is really a balance thing and this is Kerbal Space Program and not Orbiter or Human Space Program or Realistic Space Program. In Kerbalverse things must wobble and rocket sizes and the binding forces are kinda balanced so that rockets shouldn't get bigger than what you can build in VAB. Also strutting is an art. Always think about gothic cathedrals when applying struts and you are kinda on the safe side. And a wrong placed strut can ruin your day by making it worse, not better. It's a challenge, but IMO a good one.

Edit: The only downside to having to use (more) struts is part count and physics lag which is bad in 1.0.x, but i hope unity 5.2 multithreaded pyhsics and hopefully better coded resource allocation in 1.1 iron this out.

Edited September 20, 2015 by DocMoriarty

[Majorjim!]

Yeah more struts lower FPS! Seriously, we don't have life support and they expect us to make the struts that go on the INSIDE of a rocket. You can't use struts in a vertical stack and you know what rockets are, TALL and SKINNY. If you want to change reality to be less fun in a game, please just do it in a mod.

KSP rocket are made of stacks of tanks. I advised placing struts between the tanks, not inside anything. If you don't like the stock wobble then use the mod.

[Bloody_looser]

Yeah more struts lower FPS! Seriously, we don't have life support and they expect us to make the struts that go on the INSIDE of a rocket. You can't use struts in a vertical stack and you know what rockets are, TALL and SKINNY. If you want to change reality to be less fun in a game, please just do it in a mod.

My point is just because a feature is broken and there is a way around it doesn't mean you can't fix it.

There's nothing 'broken' about joints. The Klaw is broken. Mk3 joints were too weak, but it was fixed in 1.0.4.

My point is that if your contraption vessel looks like annual convention of tiny tanks, with reaction wheels in uncomfortable places, hard-gimbaling engine and TWR like 3 - it must fall apart.

Anyway, why not embrace the wobble and enjoy it?

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[DocMoriarty]

Of course you can use struts on a vertical rocket, just need to be a bit creative. I use girder segments to do vertical struting like in this image:

Edit: Also if I remember right binding forces have been way better in either 0.25 or 0.90 in stock game but they toned it down again because it really was too easy then to build big and heavy.

Edited September 20, 2015 by DocMoriarty

[Red Iron Crown]

Rigid body physics please, KJR is a bare minimum

KSP does not use soft body physics, it's all rigid body already.

[SaturnianBlue]

Most of my builds do ok without KJR, though my Voyager replica is not one of those. For me, the immediate problems with struts is less about part count and more about weight, as many of my probes weighed only perhaps a ton, and every time I added a strut, I was adding around 5% to my structure, which is a problem when your craft is 150 small bits and bobs.

[clivman]

KSP does not use soft body physics, it's all rigid body already.

As in parts are rigid and do not move at all in relation to each other. It's better phrased as rigid join physics

[Red Iron Crown]

As in parts are rigid and do not move at all in relation to each other. It's better phrased as rigid join physics

Sorry, misunderstood you.

AFAIK there's no technical reason why parts joints cannot be much stiffer than they are now (or even completely rigid), it is an aesthetic and gameplay choice on the part of the developers to have them as wobbly as they are now.

[clivman]

Sorry, misunderstood you.

AFAIK there's no technical reason why parts joints cannot be much stiffer than they are now (or even completely rigid), it is an aesthetic and gameplay choice on the part of the developers to have them as wobbly as they are now.

Rigid joints would also improve performance.

[Jon144]

But more rigid joints would also make crafts far less safe. This might make things either more fun or more frustrating.

Even though you would like things to wobble less this is due to the flexibility of joints. And can then survive greater forces placed on them without breaking. Generally the more rigid something becomes the easier it will become to break. Common glass is an example. Very strong but instead of flexing will break under strong forces.

Maybe we could have the option of choosing the rigidity/flexibility ratio of specific joints. Because both have their advantages and disadvantages under certain scenarios.

[ferram4]

I think there's a point to make here that people aren't noticing with stock joints: where does the most wobble occur? Is it between equal-sized parts, or does it occur when you have lower-mass parts sandwiched between higher-mass parts? If it's the former, then it's a design choice. If it's the latter, it's the physics engine not being designed to handle those larger mass ratios and not having joints set properly between parts to account for that.

Now, guess which one KJR is designed to handle and fix?

[nalfz]

in 0.23 and previous it was not uncommon for a third or more of a vessel's part count to be struts

Even now, I find it gets yet more extreme than that

Having gimballing engines and a control point on opposite ends of a body consisting of upwards of 20 wobbly joints between very heavy objects, e.g. 3.75m parts, is a recipe for disaster when you've got an SAS all too happy to oscillate itself into a positive feedback cycle and turn your carefully constructed rocket into a cloud of debris

The only solution to that is to get KJR or stitch the rockets together with 4-8 struts per join and hope for the best

It's a pretty much game breaking problem with larger rescales like 64k or with RSS, because all of your rockets necessarily have to be like 5 times taller. I forgot to get KJR on my 64k install not too long ago and when I tried to launch a reasonably basic heavy lifter design to get about 70t into orbit, the payload ended up backwards around my engines with the whole rocket bent into a U shape between them

[Bloody_looser]

Even now, I find it gets yet more extreme than that

Having gimballing engines and a control point on opposite ends of a body consisting of upwards of 20 wobbly joints between very heavy objects, e.g. 3.75m parts, is a recipe for disaster when you've got an SAS all too happy to oscillate itself into a positive feedback cycle and turn your carefully constructed rocket into a cloud of debris

The only solution to that is to get KJR or stitch the rockets together with 4-8 struts per join and hope for the best

It's a pretty much game breaking problem with larger rescales like 64k or with RSS, because all of your rockets necessarily have to be like 5 times taller. I forgot to get KJR on my 64k install not too long ago and when I tried to launch a reasonably basic heavy lifter design to get about 70t into orbit, the payload ended up backwards around my engines with the whole rocket bent into a U shape between them

Having issues with a mod isn't a good way to justify implementation of another mod into stock, is it?

[Azimech]

No.

The current joint system is ridiculous.

Joint strength should not be depending on mass but material type. According to KSP physics: an aluminium tank with an empty mass of 3t is stronger than a forged V8 crankshaft of 7kg. Now in your mind upscale the crankshaft to 3t or downscale the tank to 7kg. Ever wondered why crankshafts aren't made of aluminium?

That's why I started the "Other Construction Materials" mod.

KJR: Most of my uploads on KerbalX are stock. And none of them ever needed KJR. It's not about the number of struts, it's how you place them.

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Yeah more struts lower FPS! Seriously, we don't have life support and they expect us to make the struts that go on the INSIDE of a rocket. You can't use struts in a vertical stack and you know what rockets are, TALL and SKINNY. If you want to change reality to be less fun in a game, please just do it in a mod.

Struts inside: place tank on next tank. Use offset to create small gap between them. Place struts between tanks, create triangles. Use offset to decrease gap. Test and decrease number of struts until ideal situation found. Done!

Edited September 21, 2015 by Azimech

[nalfz]

Having issues with a mod isn't a good way to justify implementation of another mod into stock, is it?

Did you read my post? I'm not entirely sure you did

[Guest]

Oh my sweet summer child. Go and play 0.23 and then you can truly understand the pain of wobbly joints.

People defended that crap, too. Man, I remember watching ChickenKeeper24 and seeing how he strutted together 2.5m tanks, putting a 1/4 tank over the Mainsail, and all those little, stupid tricks you had to learn to get anything into orbit. I find stock much, much more bearable nowadays.

Of course, in addition to KJR-level joints, we should also get procedural tanks so we don't have so many joints. That would make the game much better.

[clivman]

People defended that crap, too. Man, I remember watching ChickenKeeper24 and seeing how he strutted together 2.5m tanks, putting a 1/4 tank over the Mainsail, and all those little, stupid tricks you had to learn to get anything into orbit. I find stock much, much more bearable nowadays.

Of course, in addition to KJR-level joints, we should also get procedural tanks so we don't have so many joints. That would make the game much better.

Agree completely

[Columbia]

Gentlemen please. No you do not need this as stock. You need to learn how to use struts. One or two between each tank will stop the wobble.

Can I be frank?

..That's like saying you should learn not to clip things or you should stack a crap ton of radiators on aircraft to stop clipping/overheating issues.

I'm all in for this.

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Maybe it may have been bearable in 0.90, given the crappy aerodynamics and drag mattering much less, but in 1.0, wrapping girders, beams and struts around your rocket makes it perform like you stacked a bunch of rockets on buildings with scaffolding, and under construction.

Impractical, isn't it.

[Bloody_looser]

Did you read my post? I'm not entirely sure you did

Yup, I've read it.

SAS overreaction is an issue, but it has nothing to do with joint strength.

Your problems in RSS have nothing to do with stock.

Edited September 21, 2015 by Bloody_looser

[Jouni]

Even now, I find it gets yet more extreme than that

Having gimballing engines and a control point on opposite ends of a body consisting of upwards of 20 wobbly joints between very heavy objects, e.g. 3.75m parts, is a recipe for disaster when you've got an SAS all too happy to oscillate itself into a positive feedback cycle and turn your carefully constructed rocket into a cloud of debris

This is related to two design problems in the game, but they're both rather minor and easy to work around.

Stock SAS overcorrects when it has too much control authority. The obvious workaround is reducing the amount of control authority. A rocket almost never needs reaction wheels, RCS, or fins with control surfaces, and you can also tweak down thrust vectoring or even disable it in the boosters. Still, it would be better if SAS could take the amount of control authority into account.

KSP models each joint independently, instead of modeling each stack as a single body that bends. When you have many small parts in a stack, the rocket bends too much in that region. The workaround is to avoid placing too many small parts between heavy masses, or placing the small parts in a service bay. I'm not sure how to properly fix this. The KJR solution seems too extreme, at least with the default settings.

The only solution to that is to get KJR or stitch the rockets together with 4-8 struts per join and hope for the best

Remember that one properly placed strut can be more effective than ten randomly placed ones. My stock rockets rarely have more than one strut for each booster and a few struts for securing the payload.