Big Rocket Asplode

[Demetrious]

Upon downloading 0.16 I skipped gleefully into the VAB to try out the new 'large' parts. After embracing this new era of more realistic scaling, I soon discovered the new parts have all the structural integrity of beer cans.

It makes sense that, with the parts scaled up roughly 3X, their structural integrity would be lower. Since the weight of support struts wasn\'t scaled up, you can brace them sufficiently without making it less efficient then a 'small' rocket. That\'s logical, right?

Except it doesn\'t work. You can watch those huge fuel tanks wiggle and wobble just sitting on the pad, as if little more then superglue on top and bottom keeps one attached to another. I\'ve tried bracing, and cross-bracing, and X-Bracing, and - on my latest rocket - I\'ve even resorted to running struts right down the tank-stacks, to try and hold them together. Sometimes, I can get the smaller ones into orbit, but any proper three-stage, Mun-capable rocket is a no-go. The latest one made it to 35K or so, solid as a rock, before it all went sideways. (Literally, after half the rocket exploded.) And leading the Event Log, in those same maddening, mocking tones:

Structural Failure on linkage between Fuel Tank and Fuel Tank-

Clearly I\'m missing something here. Anybody care to educate me? I\'ve built rockets that look like an explosion in a girder factory and I still can\'t put much payload on them (i.e. anything more then a minimalist Mun lander with the 3-man, 4 mass command pod) without them going mass asplode.

EDIT: Okay, re-checked, apparently it\'s a bit more then 3X. I are smrat

[Ziff]

Clearly I\'m missing something here. Anybody care to educate me? I\'ve built rockets that look like an explosion in a girder factory and I still can\'t put much payload on them (i.e. anything more then a minimalist Mun lander with the 3-man, 4 mass command pod) without them going mass asplode.

Best advice I can give you is to use the new tanks and large engines as a center main stage. Build your radial stages out of the older fuel tanks and parts. Look at the thrust on those new engines! 1200! If you\'re sticking 4 or 5 of those new LV-T30 engines on a rocket, that\'s the equivalent of 30 of the older LV-T45 vectored engines. That\'s just a kertastrophe waiting to happen. Also, pay attention to your G forces. It\'s really easy to break 4 or 5 G\'s once get above 9km with the new engines. 5 G\'s = BOOM.

Here is the first successful rocket I built in .16 that is both Mun and Min capable, with plenty of fuel for course corrections. I have several with larger landers and some with the crewtank for rescue missions as well.

-Ziff

[Demetrious]

Best advice I can give you is to use the new tanks and large engines as a center main stage.

That\'s the conclusion I\'m coming to as well. I\'ve had some success using 'large' main stages and using 2-tank 'large' parts/engines as boosters - the immense power makes them fantastic for that - but even then it can be iffy.

Look at the thrust on those new engines! 1200! If you\'re sticking 4 or 5 of those new LV-T30 engines on a rocket, that\'s the equivalent of 30 of the older LV-T45 vectored engines. That\'s just a kertastrophe waiting to happen. Also, pay attention to your G forces. It\'s really easy to break 4 or 5 G\'s once get above 9km with the new engines. 5 G\'s = BOOM.

That would explain it. If there\'s a G-meter in the GUI I really need to start watching it - it\'s obvious I vastly underestimated the size and sheer power of these new parts. I moronically thought they were there to match the 'new' 3-man command pod, so, as the command pod had been scaled up, so had the rocket parts, and roughly the same relationships applied as with building with the 'small' parts.

I can see I was mistaken.

Here is the first successful rocket I built in .16 that is both Mun and Min capable, with plenty of fuel for course corrections.

The way you cluster multiple 'small' boosters onto one decoupler is pretty clever; it solves the issue of simply not having enough space to stick boosters onto (which was driving me towards using the new parts as boosters, inevitably.) I\'m also glad to see I\'m not the only one who thinks the new radial engines are really, really nifty.

Thanks for your help!

EDIT: I especially like your use of fuel lines + the radial engines so that all three stages are firing from the get-go, but the final stage ends with full tanks.

[bsalis]

Yeah - it\'s harder but doable to build big rockets with big parts in 0.16

This is 1142 tons. Does over 1000m/s in atmosphere without breaking up. It\'s surprisingly stable on the pad.

Brace your outer tanks to inner at bottom and top.

Horizontal struts between tanks that are next to each other, at least at the bottom, sometimes the top as well.

Struts supporting second stage. Note all upper tanks have couplers.

Lots of struts needed here since i\'m not using couplers.

Less struts here since there is less weight.

I attached the craft file. It has a mechjeb radial. You can remove that by editing the craft file and removing the PART and LINK if you don\'t have mechjeb. You don\'t need it to launch it for you, but steering is impossible when your framerate is a slideshow on 1st stage.

[segaprophet]

Ample cross-bracing is your friend.

[Clouds]

but steering is impossible when your framerate is a slideshow on 1st stage.

Yyyyeah...that\'s the problem. I was excited by the new large parts because they\'re essentially 8x the smaller parts in one, so I should be able to make a more powerful rocket with less lag, but the need for so many struts offsets that. My craft-building ambitions aren\'t limited by the parts, they\'re limited by how many I can piece together and still have the game be playable.

One trick I\'ve used it to put struts literally on the facing surfaces of the tanks - you can move the camera until it\'s INSIDE one of the tanks and you\'re viewing the facing side of the connected tank. Because they have indentations in the end, you can place a strut on that surface, then zoom out and click on the congruent end of the tank you were inside - the strut will hit and connect with the nearby end instead. This doesn\'t do much for flexing, but it helps keep the joint from failing.

[bsalis]

My craft-building ambitions aren\'t limited by the parts, they\'re limited by how many I can piece together and still have the game be playable.

For that rocket of mine, i don\'t bother gravity turning until the SRBs and 1st stage is gone. A decent framerate returns with only the top three stages. It\'s less efficient, but works fine. More recently I have been using Mechjeb to do the ascnet until coasting-to-Ap, then do the rest myself. It\'s more efficient that way. You might want to try Mechjeb out.