So, I've only had this program for a couple of days. It's pretty great, I have to say. But I'm having a big issue. My first missions (the 'Hermes' missions) were originally planned to reach a height of 500k and re-enter Kearth's atmosphere, and then I had planned to go on to various missions escaping Kearth's gravity, orbiting, etc. etc. Hermes I hit 100k, Hermes II managed 200k, and Hermes III reached 300k. Beyond a three or four stage rocket, however, things seem to stall out. Adding more rockets seems to make it extremely unstable even with a dozen SAS modules. It simply becomes too heavy or too delicate, and after more than a dozen tries I've still failed to reach the same heights as Hermes III was capable of. My basic plan is to use a liquid rocket with three fuel tanks (as more seems to take more fuel to achieve lift and acceleration than the benefit it provides) and basically get it as close to being out of the atmosphere with solid fuel thrusters. Is there a better strategy? Any tips for increasing stability? I just feel stumped...