"Moar struts" aren't working. Help, or workarounds?

[birrhan]

Problem: rockets fly apart. Solution: more struts. This leads to a new problem: too many frickin parts.

This rocket has around 1600 parts, about half of which are struts. When it fails, which is ~75% of the times, it's generally at this juncture:

"Structural failure between Rockomax Jumbo 64 fuel tank and T77 radial decoupler". Devs, please take note of this critical game flaw. it's a catch 22--either you don't cross brace, and that failure mode happens, or you do cross brace, and it takes 20 minutes to get to orbit--or to find out at t=15 minutes (real time) that at 25000 meters your cross bracing did squat, then you're back to the drawing board. In neither case are you in orbit. I really want to drive this home as a critical game flaw--there needs to be some modification of the strength of supports to obviate the need for so many struts and to make the game even playable.

[rditto48801]

You might have to many parts.

The game has to simulate physics on every last part there is. The more parts, the more it has to simulate. The more it has to simulate, and the more likely something will go wrong. I have heard that the struts require extra effort to simulate physics properly.

Chances are, the physics simulation simply cannot keep up with the sheer load of parts.

There could also be a simple design flaw buried within the design that is going to cause problems, no matter how many struts you use.

I am finding myself a bit curious about a few things.

What are you trying to achieve with that rocket design?

Heck, does that thing even have enough delta V to even get into orbit?

Edit:

Your rocket may also just be far to big, heavy, and complex for the overall goal you are trying to achieve. A smaller, more efficient design might be needed.

To avoid a design that is bogged down in diminishing returns of increased weight needing more fuel and engines, which adds more weight (rinse and repeat).

Edited May 12, 2013 by rditto48801
indecision...

[OdinYggd]

Are you familiar at all with real world truss building?

KSP physics properly respects trussing when created using struts, but it also exhibits the same behavior that it is impossible to make a perfectly rigid structure- you have to allow some flex or it pops right apart.

And I too am kind of curious what kind of vessel that is. You don't see too many people launching a great wad of orange tanks like that except when attempting to reach the record for weight to LKO.

[Specialist290]

If you're only trying to get that last bit into orbit (the capsule with the LV-N), you've got way more rocket than you really need. If you're trying to get something much larger into orbit, I'd advise launching each part separately with a smaller rocket, then assembling them in orbit.

For that matter, your payload itself might be much larger and more inefficient than you really need to complete the mission. Once you're above the atmosphere and in a stable orbit, your engine's fuel efficiency (ISP) matters much more than its raw thrust, and the exact amount of fuel is less important than the mass ratio (i.e. the number you get when you divide the mass of the whole thing with full fuel tanks by its mass when empty). Both of those work together to determine your craft's "delta-v potential." There's an awesome website that explains exactly how that works in layman's terms.

tl;dr: Your problem might be that you just have Too Much Rocket.

Edited May 12, 2013 by Specialist290

[PrISM]

Your problem might be that you just have Too Much Rocket.

That isn't possible in KSP.

[birrhan]

Well, it was built as a Tylo lander. I've since reengineered it to be smaller, but the problem with the t77 is evident even with smaller tanks.

While i appreciate th criticism about the size, half of those parts are strut, and they don't work to reinforce the t77. You see the catch 22? Can someone post a picture of that rig strutted "correctly"?

[Nurph]

Would you mind posting the .craft file of your lander?

[birrhan]

Would you mind posting the .craft file of your lander?

Sure. It's already linked in the original.

[EndlessWaves]

While i appreciate th criticism about the size, half of those parts are strut, and they don't work to reinforce the t77. You see the catch 22? Can someone post a picture of that rig strutted "correctly"?

This is a game about building from different parts. In this case it seems more likely that you're using the wrong parts, rather than using the parts wrongly.

I'm trying to have a look at the craft file but KSP keeps freezing up when I attempt to load it. It doesn't appear to be delivering rovers/satellites/bases. I'd be surprised it it wasn't possible to recreate it using a lot less parts in a more efficient design.

Edited May 12, 2013 by EndlessWaves

[Flixxbeatz]

Well, it was built as a Tylo lander. I've since reengineered it to be smaller, but the problem with the t77 is evident even with smaller tanks.

No wonder why it's so frickin' huge that it looked more like a stack of boosters than a rocket.

Also, I thought I am putting too much struts already on my spacecrafts before.

After seeing that thing you've built above, I can safely say that I was totally wrong.

[Dortmunder]

I've found that using an X formation for struts keeps things pretty stable.

Then maybe one vertical beam if it's still iffy. But I haven't built anything super huge yet. My super heavy lifter has quite a few struts tho.

[maltesh]

The OP also appears to be using an upside-down tricoupler to attempt to connect three engines onto the bottom node that's being counted on to support the entire lander on liftoff.

If that's what he's doing, it's probably a significant reason for the unbalanced forces that are requiring so many struts to have a chance at lifting.

[birrhan]

do you accept that challenge then? I've gone through two failed iterations already today.

[birrhan]

The OP also appears to be using an upside-down tricoupler to attempt to connect three engines onto the bottom node that's being counted on to support the entire lander on liftoff.

If that's what he's doing, it's probably a significant reason for the unbalanced forces that are requiring so many struts to have a chance at lifting.

Well, since Squad hasn't enabled two-point support (e.g. allow the radially connected parts of a rocket to connect to nodes directly above it and provide vertical strength that way), then of course that's what I'm doing. We are limited currently to one node of attachment, and therefore all strength through that. And struts. I still argue it's a game design flaw.

[Nao]

Omg, this thing really over strutted lol ... 1600+parts ? sick.

I threw out the launcher and installed mine, removed most of the struts and now it's slowboating into space on only 570parts (1100 less lol). I have slow PC so it takes a long while to launch, and there was a crash after 20min of launch so im writing this post while waiting for the ship to ascent .

I could help you with strutting the original launher but i cant work with 1670 parts its too much. In general i think you are overstrutting too much, think of strutting not like a duct tape but rather a medical gypsum (idk how its really called). It makes connections really rigid. The more you strut the bigger the maximum tensions in the parts will be, since the most of the load will transfer through only several parts at one moment.

... after struggle with MJ to go where it should be and several crashes due to my alt tabbing :/ i got it into orbit.

I test new docking port "technology" on this launcher, but the strutted version has roughly the same amount of parts, the docking ports help mostly with attaching payload as it's much easier to strut it without random parts exploding. (oh and there is ZERO struts holding that 25 mainsails of the launcher stage together , struts aren't that essential)

Craft file <- oh and watch out for staging since subassembly loader messed up quite big here (i had to turn off engines mid flight to shut down some of the payload engines that got suddenly turned on due to staging). Also use [1] and/or [2] control groups to turn off gimbaling on most mainsails, since they give too much acceleration and wstart to wobble out the payload.

The launcher is my idea and its not really useful in showing how to strut , but try looking on how i strutted the payload, even thou it's in even less favorable position it still remains fairly rigid while transfering loads through the whole structure.

Another tip is to drop orange jumbos and work with gray 32's (it works for me but there are others that like oranges better than gray ones).

Cheers and hope that helps somehow

Edited May 13, 2013 by Nao

[Nurph]

Here is my go at it, enjoy! . https://www.dropbox.com/s/pupt1lg0u8xnz2w/KSS%20Odyssey%202_5.craft?v=0rc-g

This was my first attempt, had some control issuses but got into a stable 210x80km orbit. Final version is only slightly different than this and without control issuses.

490 parts, 8 mainsails on the launcher + 12 BACC SRBs. It should get to orbit without exploding, although that's not guaranteed.

Action group 1 will disable all but 2 of the mainsail gimbals (double tap 1 before you launch). Try not to go above 2/3 thrust until the SRBs are spent. I've also added a fourth LV-N to the center stage, since the 3x symetry engine cluster will cause imbalence if it's pushing a 4x or 2x symetry payload.

The fuel in the lander is also used first so that the rocket isn't so top heavy at latter stages. You will need to send tankers to refuel it. Personally, I would launch the lander and transfer stage seperately and dock them in orbit latter. Lemme know if there are any problems.