Jets, Jets and more Jets, have a single turbojet attached to the bottom of a single FLT100 and a single radial intake attached to the "outside" then fix these with TT-70 couplers to the outside of your rocket, each of these "modules" can lift a shade under 20 tonnes at peak airflow. Use these to either increase the efficiency of your main rocket or to deadlift it half way into orbit, once your airflow is too weak to maintain any reasonable acceleration or once you're concerned about flameouts should happen around 15000m (depending on your T/W and drag) throttle back a little then jettison the turbojet modules and ignite your main boosters, but you NEED to be travelling vertically when this happens because your turbojet modules will fly off in all directions thankfully the careful placement of the radial intakes forces them away from you. Then as soon as you are clear of the debris, starts a steep gravity turn. Your basically raising your launchpad up to 15km, meaning you're not wasting your main fuel reserves on atmosphere Of course the drawback is the effect this has on part count, for 180t of orange tanks you'd need at least 10 jet modules just to get just your cargo of the ground, assuming a 700t lifter and your looking at 880t of total deadlift which makes 44 of these jet modules, each requiring 4 parts and now you've made and additional 176 parts... Which on top of your main rocket is enough to cripple most computers My current career mode lifter uses the same principle (only much smaller) with 12 basic jets and allows me to get a lifter comprised of 10 FLT800 tanks and 5 LV-T30s (asparagus) into a stable LKO with almost half of my total fuel remaining and with almost 16 tons of cargo.