I use air breathing engines for small single stage orbital vehicles in KSP. They are much more fun to fly, albeit you have to stay in atmosphere for a longer ti

I use air breathing engines for small single stage orbital vehicles in KSP. They are much more fun to fly, albeit you have to stay in atmosphere for a longer time due to very low degree of ascent to gain speed :) If I have to go further, I make it two stage, with the last stage traditional booster stage. Anything bigger than that tends to fail though.