What is the point of keeping "wobbly rocket syndrome" stock?

[clivman]

Why not just add KJR? Struts add drag and weight, make crafts look horrible, and are not used in RL(for boosters and such). Is there any point to making 2.5 and 3.75 rockets have no structural integrity? Removing the need for struts would also severly reduce part count. I'm guessing a rigid body physics model would also require less CPU. I know this has already been suggested but I just want to know the devs reasoning for it.

[Red Iron Crown]

As I understand it the cartoonish wobble is regarded as an essential part of KSP's wacky charm. It got much better with the Great Strengthening of 0.23.5, so much so that I stopped using KJR in stockish installs. Could certainly due with being more solid still, but the "wacky charm" bit doesn't really do much for me.

[regex]

Wobbly rockets exist purely for e-peen value nowadays. Before 0.23.5 it was a failing of the devs to make joints strong enough to work with the silly LEGO paradigm of KSP.

[Camaron]

If a real space agency built something as cumbersome and bulky and multilayered as what many people create is KSP, they probably would use some struts.

If you build a classic-style pillar rocket in KSP, you don't need struts.

So really, I don't know what you're talking about.

[Hotaru]

If you build a classic-style pillar rocket in KSP, you don't need struts.

I disagree: in my experience, if a "pillar" rocket gets much taller than three or four Jumbo tanks, especially with a long payload in a fairing on top of it, it wobbles like crazy, especially with SAS/SmartA.S.S./MechJeb autopilot trying to fly it. Reducing gimbal authority helps, but often not nearly enough. Personally, I don't mind having to add the odd strut here and there to radial boosters and Space Shuttle-type configurations (where struts are used, sparingly, in real life) but the current state of things is pretty silly.

I sincerely hope there's some technical reason why this is still the case and it isn't being left this way because the devs think it's cute or "so Kerbal." Glitches and unfinished functionality bother me a lot less than lousy game design.

[A35K]

Well, I sometimes still use my 0.23 save, and with KW Rocketry mod it is simply not possible to fly a 3.75 m rocket without KJR. So we have it much better now, but I agree further joint strengthening wouldn't be bad.

[Ignath]

Because ISK (it's so Kerbal!). Personally, I think it's crazy how ridiculously strong the Gimble on engines has become, which is causing nearly all the wobble that I notice.

[Red Iron Crown]

Because ISK (it's so Kerbal!). Personally, I think it's crazy how ridiculously strong the Gimble on engines has become, which is causing nearly all the wobble that I notice.

It's not the strength of the gimbal so much (generally lower in KSP than IRL), it's that it can instantly jump from one extreme to another that causes problems, IMO.

[Ignath]

It's not the strength of the gimbal so much (generally lower in KSP than IRL), it's that it can instantly jump from one extreme to another that causes problems, IMO.

Yeah, you're right...I'm sure my designs also play a part. It's usually a combo of strong gimble + too much control authority via Reaction Wheels that causes all my wobble (the 2 forces fighting against each other); that and the fact that in these circumstances a VERY small correction can lead to HUGE wobble.

[Wallygator]

Well, if in the real world, space agencies built their rockets out of non-customisable "lego" components, and slapped together without a design plan... wobble? no, more like catastrophic failure.

Which is why ANY vehicle designed for flight is tested to the max to assure dynamic stress is dealt with. Joint reinforcement should be standard in KSP - heck, let the player pay more for additional reinforcement if desired (both cost and weight)

[godefroi]

It's not the strength of the gimbal so much (generally lower in KSP than IRL), it's that it can instantly jump from one extreme to another that causes problems, IMO.

It's not, though, or not exlusively that. The stock bug fix mod had, for a time, a fix that disabled the insta-gimble. It made things worse, not better.

I believe it's PID auto-tuning that's off. SmartASS does it, and SmartASS suffers from much less wobble.

[Red Iron Crown]

Could be, godefroi, can't disagree that SmartASS does a much, much better job of it.

[m4v]

I'm not fan of the wobblying and I don't make really big rockets.

[clivman]

It's not, though, or not exlusively that. The stock bug fix mod had, for a time, a fix that disabled the insta-gimble. It made things worse, not better.

I believe it's PID auto-tuning that's off. SmartASS does it, and SmartASS suffers from much less wobble.

For that matter, why don't they integrete stock plus and bugfix modules as well, are game breaking glitches "too kerbal" too?

[Mat2ch]

The problem with the wobble is that KSP only uses a singel point to attach parts, not the three point type. If you wonder what the difference is: Try to sit on a chair with only one leg.

If you ask me, I'd do a whole lot of things different. Parts are attached fixed point. But they can bent. Calculating the bent is not that hard and putting this information back to the 3D model neither. But this way you'd have a bending coefficent and a breaking value. This could result in other, pretty funny things, like things getting bend permanently, but not breaking, if too much force is applied. Struts could work this way. On some parts you could just ignore this, like parachutes (or only calculate something for them on impact. Like someone crashing into your stored chute and destroying it). But this will be a lot of work. Really a lot. It means writing your own physics engine, at least for the space ship parts.

The SAS problem is PID tuning. It could use some predictive code. Like, if you turn from prograde to retrograde and accelerate half of the way it will take half of the way to come to a stop. This is easy to calculate and I guess SmartSAS does it. But I haven't looked into the code yet.

[NovaSilisko]

are game breaking glitches "too kerbal" too?

Well, I have seen people defend the game's bugs and glitches as being "part of the charm". I think they need immediate medical help.

[PB666]

As I understand it the cartoonish wobble is regarded as an essential part of KSP's wacky charm. It got much better with the Great Strengthening of 0.23.5, so much so that I stopped using KJR in stockish installs. Could certainly due with being more solid still, but the "wacky charm" bit doesn't really do much for me.

Yeah. I remember trying to secure those big orange tanks. But alot of the launch 'comics' were due to inexperience and you have to learn the tricks.

1. Strut placement and triangulation. Placing struts on some parts of the ship have little effect, others have profound effects.

2. The SAS module should not be on the part of the ship will highest flexibility per unit length. It better to turn off the space stage SAS and use a large SAS attached to the launch phases.

3. The winglets need to be tuned. To close to the thrusters and they may apply to much force, to high up and too little.

4. Reduce the number of segments (needs net-loonish exclamation points). While side mounting parts increases drag, it can markedly reduce the segmental flexibility, since the side mounted parts sit over a wider stages its not too bad if a cap is placed on top (or one blenders an aero tank or device).

5. Build or stretch fuel tanks so that no stage is composed of more than one stacked tank.

If player does 2 through 5. they may find that they only need struts on space stages (looking at the lunar lander they appear to have strut comparables) , wanting stability may frequently be gained simply by slowing down the launch.

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#/media/File:LunarLander.JPG

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#/media/File:LM-9KSC.jpg

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#/media/File:Lunar_Module_Equipment_Locations_2_of_2.jpg

note the extensive use of small struts. (cough), based on this and other similar images I created small strut connector scale mods that are basically fall into

1. Welds (which the game really needs)

2. lander strapers (i.e. about apollo lunar lander length)

3. Stock

4. Super long and heavy strut for securing things like a mega-space telescope to an oversized fuel tank.

Note that !st, 2nd and 3rd parts can produce problems in VAB, the strut overstretch bug that locks the game until you exit VAB and reenter, since once you attach one end of the strut it will not release until to have validly attached the other end.

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#/media/File:Apollo_17_LM_Ascent_Stage.jpg

Notice the enclosed out mounts for the RCS thrusters. I am using 3D scale-modded MK1 cylinders for out mounting, the stock MGS and the cubic strut just aren't suitable. They are not aerodynamic.

Note that in the Heat Omnibus thread, I used such an enclosed outmount to feed a fuel line to an engine around the a heat shield (which blocks in-stack fuel transfers) to protect the rest of the craft from the improper heat reset issue in the game.

And look how extensively struts are used in this research vessel

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#/media/File:Lunar_Landing_Research_Vehicle_in_Flight_-_GPN-2000-000215.jpg

Struts are a reasonably good choice when you do not have to enclose a volume of gas, in total vacuum they do not produce drag. So the issue is enclosing the space stage.

So I have to disagree with OP. Struts have a place in the game and much of the wobble problem can be fixed by better design without necessarily resorting to struting the lower stages. And I think if you are creating someting 'outside' the NASA box, struts are a handy thing to have around even in launch stage. The reason why I say this is now with aero getting those wide draggy packages into space requires slowing the launch down (meaning engines like jets that are efficient and lots of them) and this also means securing those outmounts and also stabiling a huge dragy thing on a node that is stock 3.75 or with mod maybe 5 to 8 meters. I've launched factorys that are almost 30 meter across so struts are very nice things to have around.

But........some parts realistically need zero span welds. (massless preferably)

The problem with the wobble is that KSP only uses a singel point to attach parts, not the three point type. If you wonder what the difference is: Try to sit on a chair with only one leg.

If you ask me, I'd do a whole lot of things different.......

You can adjust the breaking torque parameter.

In general when I have fishing pole flexibility its because my launch SAS was on a thin space stage. If I turn off the space stage SAS and add a SAS module to the launch stage this causes alot to diminish. Then slow the speeds down.

A second cause of wobble is winglet tuning. There is only one winglet in the game (unless you've added more), but you can bet that NASA does not put winglets that are oversized or undersized on their rockets. Oversized winglets are as much a problem as undersized, but one can mediate this problem by moving the winglets up the launch phase lower the distance between the winglet and CoG and therefore lowering the torque they can produce.

I don't want to use the word whine but from what I see alot of the complaints are complaints about not knowing the physics and poor design. I have launched rockets with 10 burn stages that are taller than the VAB itself, yeah used struts, yeah needed outmounts and modified struts, yeah slowed down launch phase, yeah its all to compensate for an unrealistic design with a magnitude more unwelded segments (meaning linewelded not separable) than NASA has in their rockets, should I expect flawless operation? But another point is that the GAME allows users to redesign parts to suit their needs, so don't whine, modify, and if the modification was really something the game needed then it might get added.

If you really really want to fix the single point snap issue without needing struts, modify your tanks to exactly fit your need. IOW don't have a 400 and 800 when you need a 1200, instead modify the scale of an 800, making the y = 1.5 times the original. Then add 50% more mass, 50% LF and 50% more Ox. Do this for every stage and reduce, realistically, the segmental flexibility. The real name of the problem is segmental flexibility, unrealistic numbers of segments result in 'unrealistic' levels of wobble. Count your segments from your SAS module in both directions and from your winglets. if you end up with lots of segments on the thinnest stage, . . . . . . . .

IMHO, wobble and flexibility below 20000 meters alt tell me that I have a problem in my design. MechJeb generally takes care of the control issues (keyboard controls are not as good as stick controls). If the issue remains you have to treat is as a design flaw not neccesarily a game problem.

Edited June 16, 2015 by PB666

[Jouni]

In 0.22, it took me a long time to figure out how to use the Mainsail without it tearing the rocket apart. Over time, I slowly learned to use enough struts in the right places, sometimes building exoskeletons for my rockets. With enough practice, I could reliably launch 50-60 tonnes to orbit with a prebuilt rocket. Using standard lifters was almost mandatory, as it took a long time to build and test a heavy rocket.

When I saw the first screenshots from 0.23.5, they looked ridiculous. Huge boosters were attached with just the decoupler and a single strut. Soon I learned to appeciate the change. Struts had become almost unnecessary, and rockets barely wobbled at all. Now we can build quick and dirty rockets to launch large payload easily. For example, this rocket can lift around 100 tonnes to a 600 km orbit using just 6 struts (2 for the boosters and 4 around the undersized parts between the fairing base and the payload).

If you tweak the gimbal range of the Mammoth and the Twin-Boars down to 50%, the rocket follows prograde with stock SAS without any wobble.

This is why I don't believe that wobble is a problem in the game anymore.

[Captain Sierra]

It's not the strength of the gimbal so much (generally lower in KSP than IRL), it's that it can instantly jump from one extreme to another that causes problems, IMO.

I use Claw's amazing StockPlus (SQUAD, hire this guy and make StockPlus properly stock) which gives engines gimbal speed. Default speed is stupidly fast (no apreciable difference) but it limits it down to 10% of that. I've found setting it at 5% makes the SAS behave a lot better. The SAS is very much in need of some tuning though because in 1.0 it does a God-awful job of handling gimbal.

- - - Updated - - -

Well, I have seen people defend the game's bugs and glitches as being "part of the charm". I think they need immediate medical help.

Dammit Nova, I cant keep giving you rep this fast. Slow down with the quotables.

[Wallygator]

PB666... I can't requote such a big post.

I also can't spend the time reading it. Sorry.

IMHO if there is sooo much specificity required in stock play to address "wobble" then the entire concept of game play and fun has been completely lost.

Something is clearly broken... And it's likely game physics.

[Jarin]

People complaining of wobble never played pre-0.23.5. Rocket strut-exoskeletons are where it's at.

Edit:

Edited June 16, 2015 by Jarin

[clivman]

IMHO, wobble and flexibility below 20000 meters alt tell me that I have a problem in my design. MechJeb generally takes care of the control issues (keyboard controls are not as good as stick controls). If the issue remains you have to treat is as a design flaw not neccesarily a game problem.

1. Not everyone uses MechJeb

2. Not everyone can spend 10 hours on every craft and lifter.

3. Have you ever seen a booster without struts in stock KSP work? And it's not a design flaw because real boosters don't use struts. If boosters are a "design flaw" then the Delta 4 Heavy would have never existed.

4. Joints in KSP are all the same so 3.75 m parts are the same as 1.25 m parts. So building larger rockets is a "design flaw" too.

[luizopiloto]

I can make any design rock solid with just a few of well placed struts...

[Jarin]

3. Have you ever seen a booster without struts in stock KSP work? And it's not a design flaw because real boosters don't use struts. If boosters are a "design flaw" then the Delta 4 Heavy would have never existed.

You really think those real-life boosters have only a single attachment point? Struts are just secondary connections to the center stack.

[clivman]

You really think those real-life boosters have only a single attachment point? Struts are just secondary connections to the center stack.

I'm pretty sure most do have one single sturdy connection point. The Shuttle SRB's connected to the ET in one point. Besides? since complete realism is clearly not the focus of the game, why not just add rigid body physics for performance increase and part count decrease.