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Yes, resizing works much better. And MechJeb's dV readout helps immensely (before I was calculating mass and ISP and using those to calculate dV- a little bit time consuming). Plus, Ferram's launch vehicle tutorial helped me figure out which engines to use. And now that I know the TWR that I need for each stage, I can use basic physics to calculate the kN range that I need engines to be for future rockets. Finally put my first satellite into orbit! RO makes a world of difference (see what I did there?). With stock KSP physics I would just build whatever I wanted, stick the biggest rocket I could make stable under it, and shoot away. It got almost... Boring. RO may be many things (a good way to lose hair comes to mind), but never boring. Anyway. For the moment I'm working on my first manned mission. I'm sure I'll have more dumb questions later, but for the moment I'm happily building away. Thanks for your help!

Thanks! Hot staging works for me. Haven't tried the small boosters yet but I imagine they would as well. Still haven't made it to orbit, but I'm one step closer. The biggest issue now seems to be getting my dV/TWR in the right range. I don't mind crunching the numbers (I do love a good math) but for some reason it takes a ton of fiddling with fuel quantities in different stages to get even close to the dV I want. I think that this is because I'm using the wrong engines/fuels (kerosene/liquid oxygen [kerolux? Is that the right terminology?] for the first stage, hydrogen/liquid oxygen [hydrolux?] for the second stage, hydrogen/liquid oxygen for the orbital stage). Just discovered Ferram's launch-vehicle tutorials on the wiki- we'll see if that gets me any closer to the stars.

I'm new to RO, but enjoying it immensely (my math-nerd side is taking over). I've built a rocket which I believe can make it to orbit, but I have a problem. The first stage goes off well enough, but whenever I try to ignite a stage after that I can't because the engine is vapor-locked. What causes this? How do I avoid it? I've heard of ullage, but I was moving about 500 m/s at the time so this doesn't seem like it...?