Maintain Structural Integrity with a 5,000Mg Rocket

[Fel]

I have a wide base structure, each Fueltank is tied together with 12 crossed structs, (From the central out, 4 levels, 3 per level (tying each corner together)). All decouplers have been reinforced with structs as well. The level above is stabilized, tent style, onto the larger base.

I THINK KSP is overreacting due to the mass; this iteration has failures... in that two or three of the 32 rockets breaks loose / explodes... but the only reason I can't carry on is because I don't have variable thrust control, critical failure only occurs AFTER the tip.

While launching, things aren't shaking, nothing stretching, or going into the base... not much fine control needed and it is fairly stable going up... I just have a sudden failure in one of the tanks (Still a fair bit below terminal velocity as well).

[Giggleplex777]

Can you post pictures and possibly a .craft file? It's hard to tell what is wrong with your rocket without pictures.

[Fel]

Honestly, not really.

You all tend to spoil far too much for my taste; (heck, I consider the delta v's you all throw around so cavalierly spoilers as well, so).

I don't want "how to", nor do I want "use this design", I want very general solutions / suggestions... let me work out the details.

*The problem, I suspect... is that the tanks are tightly bound and I am exceeding the collision tolerance.

[foamyesque]

Could be any number of things, from the orange failtanks to overstrutting to heaven knows what else with a rocket that size.

[Jason Patterson]

How high are you stacking the fuel tanks? They'll collapse under their own weight at some point, struts or no, and any upward acceleration will only make that worse. I'd tell you how many, but that would be a spoiler. The X-32 tanks tend to hold up better than the orange, jumbo sized tanks.

I find that, very generally speaking, for monstrously large ships, an umbrella shape tends to hold up better, with as much cross bracing underneath the ship as possible.

Honestly though, with rockets of a certain size you usually wind up having to coddle them into space with high, slow gravity turns and low accelerations. The wasted launch delta-v is usually better spent removing part of the ship and making the entire thing more stable. You can also try fighting your way above the atmosphere (whether you're on a good launch trajectory or not) and get a quicksave off before the thing explodes. Once you've got a save above the atmosphere it is usually possible to figure out a means by which you can get the thing into a proper orbit.

[corvus2606]

Honestly, not really.

You all tend to spoil far too much for my taste; (heck, I consider the delta v's you all throw around so cavalierly spoilers as well, so).

I don't want "how to", nor do I want "use this design", I want very general solutions / suggestions... let me work out the details.

*The problem, I suspect... is that the tanks are tightly bound and I am exceeding the collision tolerance.

So you ask for help, then wont give the tools needed to give that help, saying you dont actually want help???

If you didnt want a How To answer, you're in the wrong part of the forum, the title is a fair giveaway.

that said, from the description you have given, it sounds like you're just trying to go too big. maybe split the ship and assemble in orbit, you can always use docking struts or quantum struts to hold it together once up there

[HoY]

Too big?? I don't consider 0.000005 tonnes to be big.. Didn't know we had parts that small to be honest.

[Fel]

Could be any number of things, from the orange failtanks to overstrutting to heaven knows what else with a rocket that size

This actually gave me a considerable thought process.

I can say, without a doubt, that I am overstrutting... but I asked "why does that matter." The answer lies in truss systems (not something I am well versed in), I am guessing... trussing is good for distributing load over a structure, but it also can absorb / dampen that load.

I've observed KSP struts undergoing tension / compression which means that even though something isn't moving; it is still under the applied forces. Motion allows some of those forces to dissipate but can cause resonant effects in large structures.

Non-motion means the forces transfer nearly perfectly, which can quickly massive forces.

How high are you stacking the fuel tanks? They'll collapse under their own weight at some point, struts or no, and any upward acceleration will only make that worse. I'd tell you how many, but that would be a spoiler. The X-32 tanks tend to hold up better than the orange, jumbo sized tanks.

Oh uhmm... right.... the entire launcher is totally not the size of the VAB... (Although, the significant mass (say, 60%) is on the bottom (only 2 tanks high); I can think of a few ways to distribute the top mass more evenly... or even reduce it. [And thank you for not giving a precise amount.]

And the tip about the fuel tanks is something I also had not considered... and fairly helpful i should say

Too big?? I don't consider 0.000005 tonnes to be big.. Didn't know we had parts that small to be honest.

XD. Now that is just silly... (At first I was going to jab at brits using "," as a fraction mark... but then I realized you used ".")

So you ask for help, then wont give the tools needed to give that help, saying you dont actually want help???

If you didnt want a How To answer, you're in the wrong part of the forum, the title is a fair giveaway.

I personally don't believe I am going "too big"; but I do believe I WENT "too big too quickly"... I went from design directly to large scale application; bad engineering on my part. I'm going to try to make smaller scale tests and do individual stage tests rather than trying to test the whole rocket all at once (I mean, I have "Subassembly Loader"... I might as well use it.)

And I understand that it is people's TENDENCY to spoil rather than to help, they know the precise solution and they WANT to give it... which is why I didn't ask "how to launch my rocket" but asked for "maintain structural integrity"... "Tips and Tricks" (preferably tips though) rather than out right solutions; you can only launch your first super heavy rocket once, so it might as well feel like an enormous achievement.

Point is, I was stuck because I thought that what I was doing would work and just needed some people to help nudge me a bit in the right direction... I'm going to apply what others have mentioned here and build a little slower, but I WANT to make this super-heavy launcher. Not with a particular ship to launch in mind (although I'll certainly build one) but because I think I CAN! Isn't that what KSP is all about?

*I guess thread can be closed, or w/e... just wanted to thank those who provided help (and a smile)*

[Giggleplex777]

You may have too many struts.

[ZingidyZongxxx]

If you're stacking the jumbo tanks more than 3 or 4 tanks high, then add some struts in between where they meet to strengthen the joints.

[HoY]

There are only two countrys left in the world that are not "officially" using the metric system, myself being a Canadian I use the Hybrid system lol.

Feet, inches, pounds, meters, kilometers, and Celsius lol

[Nao]

Stop using struts! Use docking ports instead.

1700t ship not even one strut and can get to orbit no problem.

The failures are most likely due to too big rigidity of the craft. So when load transfer occurs, under natural wobble, it ends up pushing the whole mass and inertial forces through a handful of parts and struts and thus failing.

When using docking ports, the loads are better distributed as the thing is less rigid and forces flow through more parts lowering maximum force values.

Several tips on using docking ports:

When using such design and in need to strut something you can put docking port on one end of strut to ease up the connection.

Not strutted orange tanks tend to fail when under heavy forces, replacing them with two gray ones solves the problem. (strutting tanks in stack helps also but doesn't cure all the problems)

If you want to use decouplers, the big radial one have almost the same height as two big docking ports.

[SmarterThanMe]

Too big?? I don't consider 0.000005 tonnes to be big.. Didn't know we had parts that small to be honest.

I think M is for Mega, right? Little m is for milli.

[falofonos]

When I don't go silly with struts i use only 1 or two struts to reenforce a rocket laterally.

I use lots more vertical re-enforcement.

Is it always the same tank that pops? Could be one or more struts failed to connect on that one and you've got some unbalanced forces being amplified by the ones that did.

[Merinsan]

I think M is for Mega, right? Little m is for milli.

Yep, 1Mg is generally called 1 tonne, but Mg is perfectly legitimate. To be honest, this is the first time I've ever seen it used. I suspect many people confuse tonne and ton - I know I do - so Mg would be much less confusing (you would think!).

[Fel]

You know, I had ASKED people not to supply information like that. (And you terribly know docking ports are a blatant exploit).

Requesting Lock, again.

[Navy4422]

Locked at OPs request