Sorry to resurrect an ancient post, but how in the world does that even hit orbit, let alone with a tank strapped to the top? I've been trying to reverse engineer this lifter with no success. Are the surrounding jets all jet fuel pods, or just structural fuselage sections? What's in the center? The closest I came was with a Rockomax x200-16 tank in the center, with a central Skipper engine. I had structural fuselages to hold the jets and ran fuel lines out from the center tank. Cut the jets at about 21km, engage the rocket, and I end up with a parabolic path to 70km but only about 150m/s dV to do a 600m/s orbital insertion burn -- with no payload. I have tried jet fuel canisters for each jet, structural fuselages with fuel lines from a central tank, various engines in the center, and clipping and stacking up to 4 air intakes without success. So what's the secret sauce? My closest rebuild so far: