Aerojet Rocketdyne gained much experience in large cryogenic booster engines from the M-1 engine. Intended for post-Saturn applications, Aerojet Rocketdyne’s M-1 engine demonstrated the highest thrust of any LOX/LH2 rocket engine ever built – 1.5 million lbf. The turbopump-fed, cryogenic engine had regeneratively cooled and uncooled thrust chamber configurations. All elements of the M-1 were demonstrated in subassembly tests, including integrated turbopump and gas generator tests. In addition, the M-1 engine was demonstrated using an ablative thrust chamber.