So I gave this a quick shot, took a lot of slimming down for my super heavy lifter to get in under the 128 part limit. So i used some SABRE engines which i know there is some controversy around about so I placed some restrictions on their use. Air-breathing mode was only used between 700m - 25km, with a single air intake used for each engine. Rest of the time the engines were used as a traditional rocket setup. Cargo was a section for a future Jool Space Station, the section alone weighed in at 182.3 tonnes, cargo was left untouched on ascent (no fuel/engine use). The SSTO lifter combined the use of 16 SABRE engines to provide some heavy lifting (11,840 kN at liftoff) Weighing in at 1087.21 tonnes, not a light weight by any measure. Starting TWR of 1.1. Made an orbital delivery at 102km circular orbit and returned with less than 30 seconds of spare fuel. Normally I would reduce the amount of oxidiser I take up with me but needed to keep it on this time to get in under 1.1 TWR. Launch was assisted by MechJeb (edited ascent profile - still fiddling with this to find the optimal, seems to change with each payload anyways). Return was non-assisted, not enough SAS onboard for MechJeb to lock onto retrograde without the help of the thrusters, so manual intervention needed. Piloted the landing (with quicksaves luckily, first touchdown was at around 100m/s into unforseen hill). Haven't had the chance to test this on a RSS etc. mod, would need to lower the payload, but hoping it'd be up for >100 tonne lift with only a little modification. SABRE Grasshopper: http://imgur.com/a/1soHs At the very least this is a very useful super heavy lifter. Cost per launch is about $80k for fuel (provided you return to KSC). So cost-effective, little stumbling block of being $800k to put on the launchpad though. Very good incentive not to crash EDIT: *Fixed final cost of lifter (only)