Hi there, I have previously been playing KSP without getting into any of the science behind it, but various videos and forum posts have inspired me to go and learn some of the fundamental equations for rocket science. I have a good understanding of the 'Rocket Equation' where: ÃŽâ€V = Vexh x In(M1/M0) Where Vexh = ISP(specific impulse) multiplied by G (9.8068 on Kerbin). M1 is the entire rocket's mass, and M0 is the mass of the rocket after the propellant has been burnt. My question is this: Does the specific impulse of a particular engine 'stack' with another? For example, would four engines with an impulse of lets say 320, give me a total impulse of 1280? Which when we times by G, give me a Vexh of 12552.704 for use in the rocket equation? Because when using this to calculate my ÃŽâ€V, I seem to end up with a ridiculously high number (around 10000m/s) which should be more than enough to leave Kerbin on an orbital trajectory. However, I am not seeing these results in game. ... Also on a side note, I would be really grateful if anyone could explain why whenever I am flying a 3-man capsule, using the larger stock parts, about 15,000m up my craft suffers insane amounts of G-force and tears itself apart? The craft literally bends in on itself sometimes, or a structural failure between two connected fuel tanks sends the rocket motor plowing into the rest of the rocket. I have no trouble getting to the Mun and back with the smaller parts and 1-man capsules, but 3-man capsules continue to elude me, even after directly copying other peoples successful designs.