The big Rockets

[G Addict]

So, just got 0.16 and I\'m liking it a lot, though it would be nice if my silly massive rockets would stop imploding for long enough that I can actually launch them. What this post is really about is a specific type of engine - the larger liquid rocket for main stages. Do they rip themselves apart at maximum thrust for anyone else? If I\'m sufficiently far through the atmosphere or in space and throttle even one of them up, it breaks off and shoots through the remainder of my rocket. Last time it happened my command pod was the only thing that survived - not much use when you\'re in a 100km orbit!

I mean, sure, I can just avoid using 100% thrust, but that seems rather silly to me.

Another oddity is the large SRBs - they\'re incredibly heavy for the amount of thrust and burn time they give compared to the small ones, so are more or less useless for most applications. Still, EVAs are fun and I\'ve already stranded a one kerbal lander on the Mun (silly Jeb, he mixed up the landing gear. The whole thing actually came down intact, but one leg goes down while the others go up, meaning it\'s not stable, and while it survived the landing on the Mun, I\'m dubious as to whether it would survive a kerbin landing.), the first rescue mission for which is actually the one I discovered the 100% problem. So, the rescuers are stranded in orbit while Jeb\'s twiddling his thumbs in a crater somewhere. :

[A Fat Pokemon]

Are you using struts? It seems the thrust from the engines is too much for the new decouplers if that\'s what you\'re using. And yes, EVA is awsome I also had the same sorta stranded problem heh, I ended up doing 2 orbital rendevous with stock, and it turned out alright ???

[mrdest21]

The answer really is massive and excessive usage of struts. I had the same troubles as you describe. My rockets would fly up good and then suddenly, when the atmosphere thins and the speeds pick up, the bottom would ram through the top of the rocket. The decouplers are too weak for keeping your rocket intact alone. Put struts that connect the top of lower fuel tanks to the top ones, criss cross them and just put a ton of struts. If your top stage is as wide as the bottom one, making connecting struts awkward, add wings and connect the struts to those. As an example, my current best rocket has 36 engines and 120 struts. I kind of wish the struts wouldn\'t appear in the stage assignment ui

I also find that the old decouplers, which are longer, make design easier than the new flat ones. Last note, decouplers should be put in the middle of the connected stacks. If you have 3 tanks, the decoupler connects to the middle one. In pre-0.16, I\'d put my decouplers on the top part of the stack and it would work fine. Not so in 0.16.

[MaxMurder]

Yup, spectacular failures abounds! 'You have to be careful with those big engines Jeb! The are extreamly powerful!'

I actually like the new SRBs. they look much sliker than the 'trashcan filld with explosives' look of the old ones! =P

[Hikaru]

Struts are the solution to your problem. For my rocket for each large tank I added to the ship I needed to have two struts holding it to adjacent parts, and one to two more to hold it to the inner/outer stages. An example of a recurring problem I had with my design was the decoupler and engine that connected the upper stages (lander) and the lower stages. The lander was so heavy that when the lower stages were near empty they\'d just crush the decoupler and engine, and destroy the rest of the ship as it collided with the debris remaining. For this specific decoupler, I had to use eight struts going from the bottom connection (fuel tank) to the decoupler, another eight struts going from the fuel tank above the engine on the lander to the decoupler, three struts on each wing of the lander to the fuel tanks on the outer ring of the lower stages, and finally, three struts from the outside stages on the lander to the decoupler on below the lander\'s engine. You can see the craziness here, or at least some of it:

If you\'d like a more in depth look at how I set my ship up, I\'d be glad to disassemble it. Note that you cannot see it in this shot, but I found the aircraft decoupler to be a better choice for safely jettisoning parts over the square spacecraft decoupler. It\'s a weaker joint though, so you need to add - you guessed it - more struts.

[Ziff]

What this post is really about is a specific type of engine - the larger liquid rocket for main stages. Do they rip themselves apart at maximum thrust for anyone else?

Another oddity is the large SRBs - they\'re incredibly heavy for the amount of thrust and burn time they give compared to the small ones, so are more or less useless for most applications.

Is it the engine ripping itself apart, or is it causing a failure in the large stack decoupler that has been increased in size and mass but still has the same strength of the old one? (Which will be fixed, but check here for info on the math -> http://kerbalspaceprogram.com/forum/index.php?topic=17300.msg252749#msg252749 or just go here for the new part.cfg files -> http://kerbalspaceprogram.com/forum/index.php?topic=17313.msg252831#msg252831)

Honestly, I am guessing the devs will end up making almost these same changes when they get around to going through all the parts.

Also, pay attention to your G forces. It is very easy with the new engines to clear your launch tower in a very timely fashion and if all those new engines are still burning when you get past that first atmospheric layer you can easily break 4 or 5 G\'s, which causes all kinds of bad things to happen. You are working with a lot more thrust and mass than before, so yeah, throttle that baby back and keep it around 2 G\'s for safe, happy, and still living, Kerbals.

I -LOVE- the new SRB\'s. I rarely if ever found a good use for the old ones, however, now I can use these new SRB\'s to get a nice boost up to the 3km mark which really helps conserve my liquid fuel.

-Ziff

[G Addict]

So, the answer is, as always, moar struts. Just that it\'s actually even moar struts. Could\'ve sworn I\'d used enough. Thanks all.