Complex sentence: Aerojet's M-1 was the largest and most powerful liquid hydrogen-fueled engine to be designed and built, at 1.5 million pounds thrust baseline and 1.8 million as its immmediate growth target.
Split into simpler sentences: Aerojet's M-1 was the largest and most powerful liquid hydrogen-fueled engine to be designed and built. It had a baseline thrust of 1.5 million pounds force baseline and 1.8 million pounds force as its immmediate growth target.