 The Saturn INT-18 would have used the standard S-II with J-2 engines, augmented by two or four Titan SRBs.The UA1204 and UA1207 boosters were considered, with the highest total impulse configuration using four UA1207 boosters, capable of placing of payload into low Earth orbit.Designers considered changing the amount of fuel loaded into the rocket, and whether to ignite the S-II stage on the ground, or whether to launch using the solids, and start the main stage in flight.