Hi guys. I've toyed around a lot with KSP in the old v12 days, but after getting v18 (and now 19.1) I've noticed that my old techniques for building rocket stacks just don't seem to work with stock parts - the stack suffers pretty catastrophic failures, and quite suddenly, like in mid-ascent when passing through a couple thousand feet at T+20-40s or so, or even just sitting there on the pad.

After reading and upgrading, I got Mechjeb and Novapunch parts to work again so after using those parts exclusively (well, apart from the 3-Kerbal capsule), the first flight went swimmingly, so the question is, are stock parts just naturally "flaky"?

I don't think stock parts are naturally flaky. However with 3rd party parts, they may be coded to be less in line with the stock parts (i.e have better fuel efficiency, better structural integrity etc.)

I mostly only use stock parts apart from items such as mechjeb, kethane, etc.

What i would suggest if using stock parts (or any parts for that matter) is to use the bracing struts. They make things a hell of a lot easier (and they also break when staging - which is great news if strutting accross stages). Strutts can be located on the second page of the structural items tab.

Weird.

I've tried strutting the strapped-on boosters and they usually hold up fine. It's the core of the rocket stack that for some reason collapses on itself, long before the first stage runs out, and for some reason it's usually something near the top of the stack, like the first decoupler underneath the crew module collapsing onto the RCS fuel tank underneath or something similar. I don't quite know how to strut those parts together since the struts don't seem to span sections the way I expect it to (so I'm probably doing it wrong).

I wonder whether part of this is due to the initial couple of seconds after leaving the construction bay - usually it takes a couple of seconds for KSP to initialise variables and the graphics engine, at which point the frame rate improves. Occasionally I a component at this point, even before I've fired it up. If KSP uses an accumulative damage model, that would explain what happens to be, because the initial "jolt" for when it spawns the rocket is probably quite a bit... or something...

All parts are naturally flaky. It has to do with the way connections are made. That is why the metal strut is your saviour. You really need to be using them to secure parts together at the top and bottom.

I would also suggest that when the rocket crashes, you have a look at the log at the end of the flight. It will tell you what part "failed" first setting off a cascade of events. From that you can get an idea of what to strut to improve integrity.

Also try using the Launch clamps. they will hold your rocket solidly in place and there will be less movement of parts on the launchpad. Just remember to include them in your staging so they releae when you fire your rockets.

Launch clamps i use when on the launch pad and i want to use time compression to bring up a launch window for interplanetary transit.

Hope that helps.